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1
Schurger, Uwe. "Investigation into solar powered adsorption cooling systems : adsorption technology and system analysis". Thesis, De Montfort University, 2007. http://hdl.handle.net/2086/4122.
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Due to the fact that the worldwide energy consumption caused by cooling devices in buildings has been increasing steadily and also the fact that the pressure has been rising to provide this cooling energy with environmentally friendly technology, solar powe.re~ DEC-systems (Desiccative and Evaporative Cooling) have begun capturing increasing interest over the past few years. , However, up to now little experience has been gained in the operation of these systems and thus currently little information is available about the performance, the efficiency, the control strategy and the best component choice. This lack of knowledge has resulted in a low rate of acceptance of, this technology so far. The studies presented in this thesis serve as a contribution to the advancement of DEC technology by providing fundamental knowledge about the operation and attainable performance of these systems. A comprehensive study of desiccant wheels was undertaken which provides detailed information about the operation and the achievable dehumidification performance of this component. A detailed simulation model for desiccant wheels was developed and verified with measured data from a desiccant wheel test plant. Additionally, two commercially used DEC-systems (one in a public library in Spain and the other in a plastics processing factory building in Germany) were monitored for the purposes of evaluating the performance of these systems and resolving existing problems in their operation and control strategies. In spite of the generally positive validation of the planned and expected cooling performances in both cases, the monitoring also showed that there are considerable possibilities· for improvement, especially with the regulation of the system.
2
Papakokkinos, Giorgos. "Computational modeling of adsorption packed bed reactors and solar-driven adsorption cooling systems". Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672099.
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Environmental concerns regarding climate change and ozone depletion urge for a paradigm shift in the cooling production. The cooling demand exhibits an alarmingly increasing trend, thus its satisfaction in a sustainable manner is imperative. Adsorption cooling systems (ACSs) are a potential candidate for a sustainable future of cooling production, since they can utilize solar energy or waste heat, as well as they can employ substances with zero ozone depletion and global warming potential. The objective of this thesis is to contribute to the investigation and improvement of ACSs, through the development of two computational models - which approach ACSs from different perspectives - and their respective utilization for the conduction of related numerical studies.
The first research direction focuses on the design of the adsorption reactor, the most vital component of ACSs. Its geometrical configuration is determinant for the system performance. The reactor design is a crucial task since it creates a dichotomy between the two performance indicators - the Specific Cooling Power (SCP) and the Coefficient of Performance (COP). Individual optimizations based on the SCP and the COP would result in completely opposite geometrical configurations. A computational model for the simulation of adsorption packed bed reactors was developed, capable of simulating any potential reactor geometry. A multi-timestep approach is adopted, resulting in a drastic reduction of the computational cost of the simulations. Verification and validation assessments were performed in order to evaluate the reliability of the model. Two major studies were conducted within this research direction. The first aspires to provide a comparison between five reactor geometries, motivated by the lack of comparability across different studies in the literature. Thirteen cases of each geometry are simulated, by varying the fin thickness, fin length and solid volume fraction. The second study pertains to a thorough investigation of a geometry that remained underexplored hitherto - the hexagonal honeycomb adsorption reactor. A parametric study is conducted with respect to the three dimensions that define the geometry, as well as for various operating conditions.
The second research direction is dedicated to the investigation of adsorption cooling systems, and in particular, to their integration within a wider thermal system, a solar-cooled building. Such integration is not straight-forward due to thermal inertia effects and the inherent cyclic operation of ACSs, as well as due to the dependence on an intermittent source and an auxiliary unit, with a clear objective to prioritize solar energy. A numerical model was developed using 1-d models for the adsorption reactors and 0-d models for the evaporator and condenser. The model is validated against experimental results found in the literature. The model is coupled to the generic optimization tool GenOpt, thus allowing the conduction of optimization studies. The ACS model is then coupled to solar collectors and thermal storage models, as well as to a building model. The latter was previously developed in the CTTC laboratory. This coupling results in a comprehensive simulation tool for adsorption-based solar-cooled buildings. A case study for a solar-cooled office is considered, with the objective to investigate the potential of satisfying its cooling demand using solar energy. A control strategy is proposed based on variable cycle duration, using optimized values for the instantaneous operating conditions. The variable cycle duration approach allows to satisfy the cooling demand using significantly less solar collectors or less auxiliary energy input. The potential carbon dioxide emissions avoidance is calculated between 28.1-90.7% with respect to four scenarios of electricity-driven systems of different performance and carbon emission intensity.La preocupació mediambiental sobre el canvi climàtic i l'esgotament d'ozó exigeix un canvi de paradigma en la producció de fred. La demanda de refredament mostra una tendència alarmant creixent, així és imperatiu satisfer-la de forma sostenible. Els sistemes de refredament per adsorció (ACS) són un candidat per a un futur sostenible de la producció de fred, ja que poden utilitzar energia solar o calor residual, emprant substàncies amb zero potencial d'esgotament d'ozó i d'escalfament global. L'objectiu d'aquesta tesi és contribuir a la investigació i millora dels ACS, mitjançant el desenvolupament de dos models computacionals - que aborden els ACS des de diferents perspectives - i la seva utilització per a la realització d'estudis numèrics. La primera línia d'investigació se centra en el disseny del reactor d'adsorció, el component més important dels ACS. La seva configuració geomètrica és determinant pel rendiment de sistema. El seu disseny és una tasca crucial, ja que crea una dicotomia entre la potència específica de refrigeració (SCP) i el coeficient de rendiment (COP). Les optimitzacions individuals basades en el SCP i el COP resultarien a configuracions geomètriques completament oposades. S'ha desenvolupat un model computacional per a la simulació de reactors d'adsorció tipus "packed bed", capaç de simular reactors de qualsevol geometria. S'adopta una estratègia multi-timestep, que permet una dràstica reducció del cost computacional de les simulacions. La fiabilitat del model es va avaluar a través de processos de verificació i validació. Dins d'aquesta línia de recerca es van realitzar dos estudis principals. El primer aspira a proporcionar una comparació entre cinc geometries de reactors, motivat per la falta de comparabilitat entre diferents estudis en la literatura. Es simulen tretze casos de cada geometria, variant el gruix de les aletes, la seva longitud i la fracció de volum de sòlid. El segon estudi presenta la investigació d'una geometria sub-explorada previament, el reactor d'adsorció de honeycomb hexagonal. Es realitza un estudi paramètric pel que fa a les tres dimensions que defineixen la geometria, així com per a diverses condicions de funcionament. La segona línia de recerca es dedica a la investigació dels ACS. i en particular, a la seva integració dins d'un sistema tèrmic més ampli, un edifici refredat per energia solar. Aquesta integració no és senzilla a causa de la inèrcia tèrmica i a el funcionament cíclic inherent dels ACS, així com a la dependència d'una font intermitent i d'un sistema auxiliar, amb l'objectiu de prioritzar l'energia solar. S'ha desenvolupat un model numèric utilitzant models 1-d pels reactors i models 0-d per l'evaporador i el condensador. El model es va validar amb resultats experimentals trobats en la literatura. El model es va acoblar amb l'eina d'optimització genèrica GenOpt, permetent així estudis d'optimització. El model ACS es va acoblar amb models de col·lectors solars, emmagatzematge tèrmic i amb un model d'edifici. Aquest últim va ser desenvolupat prèviament al CTTC. Aquest acoblament resulta a una eina de simulació integral per a edificis refredats per energia solar utilitzant adsorció. Es considera un cas d'estudi per a una oficina refredada per energia solar, amb l'objectiu d'investigar el potencial de satisfer la seva demanda de fred utilitzant energia solar. Es proposa una estratègia de control basada en la duració variable del cicle, utilitzant valors optimitzats per a les condicions instantànies. La durada variable d'el cicle permet satisfer la demanda utilitzant una quantitat significativament menor de col·lectors solars o un menor aportació d'energia auxiliar. Les emissions de CO2 evitades es calculen entre 28.1-90.7% respecte a quatre escenaris de sistemes elèctrics de diferent rendiment i intensitat d'emissions de carboni.
3
Merino, Jose Carlos Alvarez, e Kazuo Hatakeyama. "Technology surveillance of the solar refrigeration by absorption/adsorption". Institute of Electrical and Electronics Engineers Inc, 2016. http://hdl.handle.net/10757/622310.
Texto completo da fonteResumo:
PICMET 2016 - Portland International Conference on Management of Engineering and Technology: Technology Management For Social Innovation, Proceedings4 January 2017, Article number 7806767, Pages 1976-19822016 Portland International Conference on Management of Engineering and Technology, PICMET 2016; Honolulu; United States; 4 September 2016 through 8 September 2016; Category numberCFP16766-ART;
Code 125891In order to establish networks of cooperation looking for not to duplicate research and even to make use of existing research in a remote form, it is necessary to identify and classify (around the world) the researchers and laboratories, that are researching in the topic of solar refrigeration by absorption/adsorption. The methodology consists in: i) the technology's classification, ii) technological trajectory Identification, iii) a thematic bibliographic review, and iv) patent's analysis. In this way, with the previous determination of keywords, will be identified main authors and their respective institutions. With the same keywords, are determined the licensed patents (in certain span of time). In addition, the analysis of publications, patents, and commercial products give us an opportunity to establish comparisons between prototypes and tests (in several conditions). The larger results implicate the use of actor's network and the remote access to the data and tests, for a collaborative research, overcoming the lack of laboratory resource and accelerating the knowledge acquisition
Revisión por pares
4
Sinha, Saket. "An energy efficient solar-assisted advanced adsorption chiller system". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23401.
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The rise in living standards and the environmental challenges associated with fossil energy has attracted engineers and researchers to focus on energy use of buildings. Buildings consume 40% of world’s total energy consumption and air-conditioning alone consumes 15% of building’s total energy consumption. The integration of solar energy with adsorption cooling technology is an attractive area of research. The thesis develops a literature review of adsorption working pairs and different nanofluids used as cooling liquid in the adsorption chiller system. An advanced adsorption chiller system uses composites ‘salt inside porous matrix’ (CSPM) as adsorption material and multiwalled carbon nanotubes/graphene nanofluid (MWCNT/GNF) as cooling liquid. An adsorption chiller model used in TRNSYS simulation software compares temperature profiles of different components like solar collector, hot storage tank and an office space for conventional silica gel↔water and activated carbon fiber with barium chloride salt (ACF/BCS)↔ammonia adsorption chillers. The effect of MWCNT/GNF to improve performance of adsorption chiller is analysed. It is found that activated carbon fiber/nickel chloride salt (ACF/NCS) and ACF/BCS can improve the coefficient of performance (COP) by 23.4% and 95.7%, respectively. The later part of the thesis develops a nonlinear model predictive control (NMPC) model for (ACF/BCS)↔ammonia adsorption chiller system. The cumulative fossil fuel consumption for an year reduces by 61.3% using the NMPC approach for (ACF/BCS)↔ammonia adsorption chiller plant. The potential benefits of the application of NMPC in optimal management of solar energy, improving energy-efficiency and thermal comfort for an office space are highlighted in this study.
5
You, Ying 1962. "A solar adsorption refrigeration system operating at near atmospheric pressure". Monash University, Gippsland School of Engineering, 2001. http://arrow.monash.edu.au/hdl/1959.1/8740.
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6
Escobedo, João Francisco. "Refrigeração com uso de energia solar". Universidade de São Paulo, 1987. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-28052009-094024/.
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Uma simulação numérica do ciclo de refrigeração a adsorção é realizada para os pares zeólita-água e carvão ativo AC-35 metanol, justificando a escolha do par bem como do sistema de captação a serem utilizados no protótipo. O protótipo construído compreende um concentrador cilíndrico-parabólico com rastreamento solar, um tubo de calor e uma unidade frigorífica (com zeólita-água). Aspectos tecnológicos como válvulas, soldas e carregamento do par na máquina são analisados. Os resultados dos testes de desempenho são apresentados, discutidos e comparados com a literatura. Uma análise de custos é feita. Paralelamente, construímos termo pilhas pelo método da evaporação. Estas termopilhas foram utilizadas na construção do piranômetro e do pireliômetro. Os instrumentos são caracterizados em termos de sensibilidade, constante de tempo, linearidade, efeitos de temperatura e convecção natural. Os resultados desta caracterização são discutidos e comparados com um modelo fabricado pela Eppley. Finalmente, no apêndice I, testamos o desempenho de um coletor plano utilizando no absorvedor o revestimento seletivo de óxido de alumínio recentemente desenvolvido no IFQSC. As melhores condições para obtenção do revestimento seletivo em placas de grande porte são estudadas.A numerical simulation of the adsorption refrigeration cycle was made for zeolite/water and activated carbon(AC-35)/ methanol pairs, to select the pair and the solar collector in the prototype. The fabricated prototype consists of a cylindrical paraolic concentrator with solar trackins, a heat pipe and the refrigeration unit (with the zeolite/water pair). The technical aspects of values, welds and out-gassing are analyzed. The results of the performance tests are presented, discussed and compared with the literature. An analysis of costs is made. In parallel thermopiles were constructed using the evaporation method. These thermopiles were used in the construction of the piranometer and the pirheliometer. The instruments were characterized in terms of: sensitivity, stability with time, linearity, effects of temperature and natural convenction. The results of this characterization are discussed and compared with a model made by Eppley. Finally, in Apendix I, we tested the performance of a flat plate collector using a selective coating of aluminium oxide (developed in IFQSC) as absorber. The Best conditions for obtaining the seletive coating on big size plates are discussed.
7
Tabassum, Alim Abid. "Solar refrigeration : evaluation of technical options and design of a solar-generator-adsorber for a novel adsorption refrigerator". Thesis, Cranfield University, 1989. http://dspace.lib.cranfield.ac.uk/handle/1826/4213.
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Various technical options for developing a solar operated refrigerator have been discussed. Their suitability for being used as a vaccine store for the conditions specified by the World Health (EPI) Organization Expanded Programme on Immunization 4have been evaluated. A model to predict the performance of a photovoltaic refrigerator have been developed and used to identify factors which influence its performance. It was concluded that it can be more competitive in areas where insolation is high and sunshine hours are long. It has been proposed that ice-lined refrigerators, which would run during the day, may be more economical and eliminate the need for a battery storage. The option of operating an 'Electrolux' absorption refrigerator with evacuated tube heat pipe collectors has been assessed. It was concluded that the operation was not possible without a major re-design of the commercially available models. However, it was proposed that coordination of the EPI with other development programmes may be useful. It is proposed to build, with this coordinated effort, biogas plants. Biogas can then fuel the modified burner of the kerosene fueled absorption refrigerators. This may well prove to be a cheaper option. Characterization of various adsorption pairs has been done using the experimental rig developed for the purpose. The influence of various properties of adsorption pairs on the performance of an adsorption refrigeration cycle has been studied. It was observed that the generation temperature in an adsorption refrigeration cycle (or a bivariant absorption system), for a specified operating regime, was only a function of the refrigerant. A relationship between the refrigerant properties and the generating temperature for specified operating conditions was developed. Using this relationship it was established that ammonia and methanol cannot be generated at temperatures below 1200C for WHO/EPI specified operating conditions, if the condenser was air-cooled. A novel idea of direct absorption of solar radiation into the activated carbon bed is put forward to combat the temperature differential of 214°C, in a conventional design of SGA, between the carbon and the metal container. The idea was practically implemented by replacing the top of the metal box by transparent glass sheet. The seal between the metal container and glass imposed practical difficulties in that design but the tests proved that the idea had potential. A new tubular design of the SGA is proposed finally which is hoped to bring improvement to the performance of activated carbon adsorption refrigerators.
8
Tabassum, Salim Abid. "Solar refrigeration: evaluation of technical options and design of a solar-generator-adsorber for a novel adsorption refrigerator". Thesis, Cranfield University, 1989. http://hdl.handle.net/1826/4213.
Texto completo da fonteResumo:
Various technical options for developing a solar operated
refrigerator have been discussed. Their suitability for being used
as a vaccine store for the conditions specified by the World Health
(EPI)
Organization Expanded Programme on Immunization
4have been evaluated.
A model to predict the performance of a photovoltaic refrigerator
have been developed and used to identify factors which influence its
performance. It was concluded that it can be more competitive in
areas where insolation is high and sunshine hours are long. It has
been proposed that ice-lined refrigerators, which would run during
the day, may be more economical and eliminate the need for a battery
storage.
The option of operating an 'Electrolux' absorption refrigerator with
evacuated tube heat pipe collectors has been assessed. It was
concluded that the operation was not possible without a major
re-design of the commercially available models. However, it was
proposed that coordination of the EPI with other development
programmes may be useful. It is proposed to build, with this
coordinated effort, biogas plants. Biogas can then fuel the modified
burner of the kerosene fueled absorption refrigerators. This may
well prove to be a cheaper option.
Characterization of various adsorption pairs has been done using the
experimental rig developed for the purpose. The influence of various
properties of adsorption pairs on the performance of an adsorption refrigeration cycle has been studied. It was observed that the
generation temperature in an adsorption refrigeration cycle (or a
bivariant absorption system), for a specified operating regime, was
only a function of the refrigerant.
A relationship between the refrigerant properties and the generating
temperature for specified operating conditions was developed. Using
this relationship it was established that ammonia and methanol
cannot be generated at temperatures below 1200C for WHO/EPI
specified operating conditions, if the condenser was air-cooled.
A novel idea of direct absorption of solar radiation into the
activated carbon bed is put forward to combat the temperature
differential of 214°C, in a conventional design of SGA, between the
carbon and the metal container. The idea was practically implemented
by replacing the top of the metal box by transparent glass sheet.
The seal between the metal container and glass imposed practical
difficulties in that design but the tests proved that the idea had
potential. A new tubular design of the SGA is proposed finally which
is hoped to bring improvement to the performance of activated carbon
adsorption refrigerators.
9
AraÃjo, Maria Elieneide. "ValidaÃÃo experimental de um resfriador de Ãgua operando em ciclo de adsorÃÃo com aquecimento solar indireto". Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=3400.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorApresenta a validaÃÃo experimental de um novo refrigerador solar por adsorÃÃo com aquecimento indireto. Os componentes do refrigerador sÃo: adsorvedor, condensador, evaporador e coletor solar. A escolha do par adsorbato / adsorvente, Ãgua e sÃlica gel tipo RD, respectivamente, levou em consideraÃÃo as temperaturas alcanÃadas pelos coletores e disponÃveis para a dessorÃÃo do fluÃdo refrigerante (Ãgua) das cavidades do material adsorvente (sÃlido poroso). Devido à coexistÃncia das etapas de aquecimento e resfriamento no adsorvedor, foi definida uma geometria para este componente capaz de permitir uma melhor dissipaÃÃo de calor no material adsorvente na fase de resfriamento, e a conservaÃÃo de energia tÃrmica durante a fase de aquecimento. Os resultados experimentais comprovaram o funcionamento do refrigerador, visto que foram atingidas temperaturas de 140ÂC na entrada do adsorvedor, 80ÂC no leito adsortivo e de 4,4ÂC no evaporador, possibilitando sua aplicaÃÃo em sistemas de condicionamento de ar
This work presents the experimental validation of a new adsorption solar refrigeration with indirect heating. The components of the refrigerator are: an adsorber, a condenser, an evaporator, and a solar collector. The choice of the adsorbate / adsorbent pair, water and silica gel type RD, respectively, took into consideration the temperatures reached by the solar collectors and available for the desorption of the refrigerant fluid (water) from the cavities of the adsorbent material (a porous solid). Due to the co-existence of the heating and cooling phases in the adsorber, a specific geometry for this component was defined so as to allow a good heat dissipation in the adsorbent material in the cooling phase, and the conservation of thermal energy in the heating phase. The experimental results validate the operation of the refrigerator, as temperature valves of 140ÂC at the inlet of the adsorber, of 80ÂC in the adsorber bed, and of 4,4ÂC in the evaporator were reached, allowing its application in air conditioning systems
10
Demirocak, Emre Dervis. "Thermodynamic And Economic Analysis Of A Solar Thermal Powered Adsorption Cooling System". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610110/index.pdf.
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In this thesis, yearly performance of the solar adsorption cooling system which is proposed to be installed to a residential building in Antalya is theoretically investigated in detail. Firstly, thermodynamic designs of the adsorption cooling cycle for three different types of cycles which are intermittent, heat recovery and heat &mass recovery cycles are presented. Secondly, adsorption characteristics of three adsorbent/adsorbate pairs which are zeolite-water, silica gel-water and activated carbon-methanol are given. Following this, load side (i.e., building) of the system is designed and parameters that should be considered in building design are presented. Then, solar-thermal cooling system design methodology with an emphasis on solar fraction is presented. In addition, system parameters effecting the performance of the adsorption cooling system are analyzed and results are presented. Finally, economic analysis is done in order to understand the economic feasibility of the solar-thermal cooling systems compared to conventional cooling systems. TRNSYS is used for the yearly simulations and an integrated model of the overall system is developed in TRNSYS. Since energy consumption and performance investigations of environment-dependent systems such as building HVAC, refrigeration systems and solar collectors usually require weather information, typical meteorological year (TMY) data for Antalya is also generated in order to be used in the analysis of the system parameters.
11
Taylan, Onur. "Numerical Modeling And Performance Analysis Of Solar-powered Ideal Adsorption Cooling Systems". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611799/index.pdf.
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Energy consumption is continuously increasing around the world and this situation yields research to find sustainable energy solutions. Demand for cooling is one of the reasons of increasing energy demand. This research is focused on one of the sustainable ways to decrease energy demand for cooling which is the solar-powered adsorption cooling system. In this study, general theoretical performance trends of a solar-powered adsorption cooling system are investigated using TRNSYS and MATLAB. Effects of different cycle enhancements, working pairs, operating and design conditions on the performance are analyzed through a series of steady and seasonal-transient simulations. Additionally, a normalized model is presented to investigate the effects of size of the system, need for backup power, collector area and mass of adsorbent. Results are presented in terms of values and ratios of cooling capacity weighted COP. For the conditions explored, the thermal wave cycle, wet cooling towers, high evaporation temperatures and evacuated tube collectors produced the highest COP values. Moreover, the heat capacity of the adsorbent bed and its shell should be low for the simple and heat recovery cycles and the adsorbent bed should be cooled down to the condensation temperature for all cases to achieve the highest possible COP. The selection of working pair should depend on the temperature of the available heat source (solar energy in this study) since each working pair has a distinct operating temperature range. Furthermore, there is always a need for backup power for the analyzed location and the system.
12
Marcos, Carla Abregú, Abraham Sopla Maslucán, Miguel Cano Lengua e José C. Alvarez. "Co-authors Networks in Adsorption Refrigeration and Air-Conditioning with Solar Energy". Universidad Peruana de Ciencias Aplicadas (UPC), 2021. http://hdl.handle.net/10757/653778.
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El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.The refrigeration and air conditioning systems by adsorption with solar energy are a very interesting option to replace the conventional compression systems because they save energy, are noiseless and use non-aggressive ozone layer refrigerants; however, there are scarcities of studies at this topic. The acquisition of knowledge and positioning in research on this topic by new research groups could be facilitated by knowing the context, trends, and collaborations that emerge in the subject. A map of collaborative co-authors between the greatest authors on the subject was drawn up, the same one that is done using Gephi software. From the analysis of these maps, the centrality degree and collaboration between the authors were determined.
Revisión por pares
13
Yeung, King-ho, e 楊景豪. "An optimization model for a solar hybrid water heating and adsorption ice-making system". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29632432.
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14
Bivona, Santo. "Adsorption Machine & Desiccant Wheel based SOLAR COOLING in a Second Law perspective". Thesis, Università degli Studi di Catania, 2011. http://hdl.handle.net/10761/224.
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This thesis work is intended to investigate energy and exergy performance of a low power prototype solar air conditioning system based on sorption materials. Its performance is analyzed in the light of both the First and Second Law of Thermodynamics and compared with conventional HVAC systems as well as with a further solar cooling technology based on desiccant wheels (Solar DEC).
The adsorption machine based solar cooling plant was thoroughly designed and its thermal performance analysed in several operating conditions and then optimized according to a First Law and Second Law approach.
The sensitivity theory was also applied in order to investigate the system response to deviations of some state variables from their nominal values. In this context a number of sensitivity coefficients were determined in relation to the most relevant design parameters. That provided useful information for control strategies in dynamic regime and hints for systems design and optimization.
A general model was also developed and implemented in a computer code for the determination of the thermophysical properties of humid air streams when leaving a desiccant wheel, based on the Jurinak Method.
An important outcome of this research work is that solar energy, with its relatively low energy potential -when made available by a low-to-medium temperature collector, such as with adsorption machines or desiccant wheels-, is a more appropriate energy source to air-conditioning than conventional systems, from a true thermodynamic point of view. In this sense its technology should be developed and its use should be encouraged.
15
Mayor, Louise Charlotte. "The adsorption and charge-transfer dynamics of model dye-sensitised solar cell surfaces". Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/13521/.
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In this thesis, the dye molecule cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II) (N3) is studied on the rutile TiO2(110) and Au(111) surfaces. The molecules were deposited onto the surfaces using an ultra-high vacuum (UHV) electrospray deposition system. Thermally labile molecules such as N3 cannot be deposited using the typical method of thermal sublimation, so development of this deposition technique was a necessary step for entirely in situ experiments. The geometric and electronic structure of the samples are characterised using core-level and valence band photoemission spectroscopy, x-ray absorption fine structure spectroscopy, density functional theory, resonant x-ray emission spectroscopy and scanning tunnelling microscopy. These reveal that N3 bonds to TiO2(110) by deprotonation of the carboxyl groups of one bi-isonicotinic acid ligand so that its oxygen atoms bond to titanium atoms of the substrate, and one of the thiocyanate groups bonds via a sulphur atom to an oxygen atom of the substrate. N3 bonds to Au(111) via sulphur atoms with no deprotonation of the carboxylic groups, and at low coverages decorates the Au(111) herringbone reconstruction. For N3 on TiO2, a consideration of the energetics in relation to optical absorption is used to identify the main photoexcitation channel between occupied and unoccupied molecular orbitals in this system, and also to quantify the relative binding energies of core and valence excitons. For N3 on Au(111), the energetics show that the highest occupied molecular orbital overlaps with the Au conduction band. The transfer of charge between the N3 molecule and the TiO2(110) and Au(111) surfaces was studied using resonant photoemission spectroscopy and resonant x-ray emission spectroscopy. These techniques, combined with knowledge gained about the geometric and electronic structure, are used to determine the locations and electronic levels of N3 from which charge is readily transferred to the substrate. The core-hole clock implementation of resonant photoemission spectroscopy is used to reveal that electron delocalisation from N3 to TiO2(110) occurs within 16 femtoseconds.
16
Thoms, Matthew W. "Adsorption at the nanoparticle interface for increased thermal capacity in solar thermal systems". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74946.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 86-88).
In concentrated solar power (CSP) systems, high temperature heat transfer fluids (HTFs) are responsible for collecting energy from the sun at the solar receiver and transporting it to the turbine where steam is produced and electricity is generated. Unfortunately, many high temperature HTFs have poor thermal properties that inhibit this process, including specific heat capacities which are half that of water. In an effort to enhance the effective heat capacity of these high temperature HTFs and thus increase the efficiency of the CSP systems, adsorption energy at the liquid-solid interface was investigated as a mechanism for increased thermal capacity. Solid ceramic nanoparticles were dispersed in several molten salts at 1-2% by mass with diameters ranging from 5 nm to 15 nm to provide a significant available surface area for adsorption at the particle-molten salt interface. After successful nanofluid synthesis, differential scanning calorimetry (DSC) was used to measure anomalous deviations from the expected heat capacity and enthalpy of fusion values in the nanofluids. The variation in the sensible and latent heat values was determined to be dependent on the presence of sub-100 nm particles and attributed to a layer of salt that remains adsorbed to the surface of the nanoparticles after the bulk of the salt has melted. The adsorbed salt layer is expected to desorb at a higher temperature, providing an increased effective thermal capacity in the vicinity of this desorption temperature. A thermal analysis technique utilizing DSC was proposed to approximate the thickness of the adsorbed layer at the liquid-solid interface, a value that has previously only been obtained using simulation or transmission electron microscopy. More specifically, the adsorbed layer of LiNO3 on Al2O3 particles was determined to be 5.3-7.1 nm thick, similar to the 1-3 nm layers that have been observed in literature for simple, monatomic fluids. The results provide new insight into the nature of adsorption at the liquid-solid interface in more complex fluid and particle systems that can be harnessed for enhanced thermal capacity in HTFs.
by Matthew W. Thoms.
S.M.
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Lefebvre, Dominique. "Thermal Energy Storage Using Adsorption Processes for Solar and Waste Heat Applications: Material Synthesis, Testing and Modeling". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34173.
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As the worldwide energy demand continues to increase, scientists and engineers are faced with the increasingly difficult task of meeting these needs. Currently, the major energy sources, consisting of oil, coal, and natural gas, are non-renewable, contribute to climate change, and are rapidly depleting. Renewable technology research has become a major focus to provide energy alternatives which are environmentally-friendly and economically competitive to sustain the future worldwide needs. Thermal energy storage using adsorption is a promising technology which can provide energy for heating and cooling applications using solar and waste heat sources. The current work aims to improve adsorption systems to provide higher energy outputs and therefore, more economical systems. New adsorbents and operating conditions were tested with the goal of storing the available energy more efficiently. A model was also developed to gain a better understanding of the adsorption system to improve this developing technology.
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Al, Hodali Reyad. "Numerical simulation of an agricultural foodstuffs drying unit using solar energy and adsorption process". Doctoral thesis, Universite Libre de Bruxelles, 1997. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212169.
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Liu, X. "Removal of humic substances from water using solar irradiation and granular activated carbon adsorption". Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/20232/.
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For the existing water treatment processes, difficulties in removing humic substances (HS) to improve drinking water quality, and safety, have created the demand for exploring novel options to enhance HS removal. Here a combination of solar irradiation and granular activated carbon (GAC) adsorption is proposed. It aims to make use of the most freely available and abundant energy source, sunlight, to improve the performance of GAC adsorption process. An investigation into how characteristics of HS vary under natural sunlight and how this influences the subsequent removal of HS by GAC adsorption was carried out. Bulk water parameters, and more specifically, UV absorbance at 254 nm (UV254), as well as dissolved organic carbon (DOC) were used in conjunction with molecular weight (MW) to evaluate the performance of the solar-GAC method. The observation was made that solar irradiation led to a decrease in DOC, UV254 and MW of HS. The high MW components were photodegraded into smaller molecules, even with very low solar intensity in winter. Significant photodegradation of small molecules was also achievable by exposure to natural sunlight alone. Pre-treatment using solar irradiation was shown to successfully improve the GAC adsorption performance on HS removal, increasing the DOC removal from 69 % to 95 %. An up to three-fold increase in the adsorption capacity of GAC for the irradiated HS was observed. Solar collectors were found to effectively enhance the photodegradation of HS, and consequently enhance the removal of HS by GAC adsorption. The application of solar collectors could be a viable option for humic water treatment. The proposed solar irradiation-GAC adsorption method provides a new approach for the treatment of humic rich waters. The utilization of solar irradiation in water treatment processes is considered a sustainable and promising field.
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Mengistu, Meron Mulatu. "Study of Solar Cooling Alternatives for Residential Houses in Bahir dar city :". Thesis, KTH, Energiteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-63419.
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The energy consumption rate of non-OECD countries rises about 2.3 percent per year as compared to the energy consumption rate of OECD countries which is 0.6 percent. If developing countries use energy efficient technology and integrate renewable energy systems in the new building their carbon dioxide emission rate reduces by 25 to 44 percent. However, even now, renewable energy integrated buildings are hardly considered while constructing them. This thesis work focuses on the study of solar cooling system options for residential house in Bahir Dar city. To meet the demand of housing in the city, different type of apartments and villa houses are under construction. Case study was made focusing on two types of residential houses (condominium apartment and Impact Real-estate Villa house) to determine the cooling load and to select cooling system. Simulation results of IDA ICE software show that the average operative temperatures and cooling loads for condominium apartment and Real-estate Vila are 31.8oC and 30.7oC, 5.53 kW and 5.73 kW respectively. Most of the residences are not satisfied at this operating temperature. There are different types of solar cooling systems. Solar Sorption cooling systems are commonly used which can also be classified in to absorption, adsorption and desiccant cooling systems. Solar adsorption cooling systems are easy to manufacture locally as compared to solar absorption cooling systems. They do not have moving parts. Some of the working medium pairs used in adsorption cooling system are: Activated Carbon/Ammonia, Silica gel/ water, Zeolite/water. Adsorption chillier with Silica gel/ water as a working pair was selected since it can operate at regeneration/desorption temperature as low as 45oC coming from flat plate collectors. At 75oC regeneration temperature, the system delivers 9oC chilled water temperature. The selected solar adsorption chiller has been compared with kerosene based adsorption cooling system using HOMER software. In this project, the optimization was limited on cost comparison between the two energy sources. The solar based cooling system has lower working cost. From cooling load simulation result direct solar irradiation is the highest source of cooling load for both houses. This gives an opportunity for passive solar cooling technology.
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Karki, Bipin. "Experimental and Life Cycle Analysis of a Solar Thermal Adsorption Refrigeration (STAR) Using Ethanol - Activated Carbon". University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1524583058600568.
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Mesta, Murat. "Adsorption Of Aromatic Molecules On Rutile Tio2(110) Surfaces". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610928/index.pdf.
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Transition metal oxides having high dielectric constants and wide band gaps find very important and interesting technological applications in surface physics. In particular, titania is the most commonly used material in heterogeneous catalysis because of its stable and flat surfaces. Having Ti cations at different charge states within the system brings about various novel electronic properties which are mainly surface related. Adsorption of catalytically important or chemically useful molecules on titania surfaces are investigated, electronic energy bands and charge densities are calculated from first principles using the density functional theory in the GGA scheme. The comparisons with the leading theories and existing experimental data are maid.
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James, Keith Edward. "The Effects of Phosphonic Acids in Dye-Sensitized Solar Cells". PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2951.
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Novel methods for the construction of dye-sensitized solar cells (DSSCs) were developed. A thin dense underlayer of TiO2 was applied on fluorine-doped tin oxide (FTO) glass using as a precursor Tyzor AA-105. Subsequently a mesoporous film of P-25 TiO2 was applied by spreading a suspension uniformly over the surface of the underlayer and allowing the plate to slowly dry while resting on a level surface. After sintering at 500° C slides were treated with TCPP as a sensitizing dye and assembled into DSSCs. A novel method was used to seal the cells; strips of Parafilm® were used as spacers between the electrodes and to secure the electrodes together. The cells were filled with a redox electrolyte and sealed by dipping into molten paraffin.
A series of phosphonic acids and one arsonic acid were employed as coadsorbates in DSSCs. The coadsorbates were found to compete for binding sites, resulting in lower levels of dye adsorption. The resulting loss of photocurrent was not linear with the reduction of dye loading, and in some cases photocurrent and efficiency were higher for cells with lower levels of dye loading.
Electrodes were treated with coadsorbates by procedures including pre-adsorption, simultaneous (sim-adsorption), and post-adsorption, using a range of concentrations and treatment times and a variety of solvents. Most cells were tested using an iodide-triiodide based electrolyte (I3I-1) but some cells were tested using electrolytes based on a Co(II)/Co(III) redox couple (CoBpy electrolytes). Phosphonic acid post-adsorbates increased the Voc of cells using CoBpy electrolytes but caused a decrease in the Voc of cells using I3I-1 electrolyte. Phosphonic acids as sim-adsorbates resulted in a significant increase in efficiency and Jsc, and they show promise as a treatment for TCPP DSSCs.
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Besharat, Zahra. "Adsorption of molecular thin films on metal and metal oxide surfaces". Doctoral thesis, KTH, Materialfysik, MF, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195613.
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Metal and metal oxides are widely used in industry, and to optimize their performance their surfaces are commonly functionalized by the formation of thin films. Self-assembled monolayers (SAMs) are deposited on metals or metal oxides either from solution or by gas deposition. Thiols with polar terminal groups are utilized for creating the responsive surfaces which can interact electrostatically with other adsorbates. Surface charge effects wetting and adhesion, and many other surface properties. Polar terminal groups in thiols could be used to modify these factors. Mixed SAMs can provide more flexible surfaces, and could change the resulting surface properties under the influence of factors such as pH, temperature, and photo-illumination. Therefore, in order to control these phenomena by mixed polar-terminated thiols, it is necessary to understand the composition and conformation of the mixed SAMs and their response to these factors. In this work, mixtures of thiols with carboxylic and amino terminal groups were studied. Carboxylic and amino terminal groups of thiol interact with each other via hydrogen bonding in solution and form a complex. Complexes adsorb to the surface in non-conventional orientations. Unmixed SAMs from each type, either carboxylic terminated thiols or amino terminated thiols are in standing up orientation while SAMs from complexes are in an axially in-plane orientation. Selenol is an alternative to replace thiols for particular applications such as contact with biological matter which has a better compatibility with selenol than sulfur. However, the Se-C bond is weaker than the S-C bond which limits the application of selenol. Understanding the selenol adsorption mechanism on gold surfaces could shed some light on Se-C cleavage and so is investigated in this work. Se-C cleavage happens in the low coverage areas on the step since atoms at steps have lower coordination making them more reactive than atoms on the terraces. Another area where the self-assembly of molecules is of importance is for dye sensitized solar cells, which are based on the adsorption of the dye onto metal oxides surfaces such as TiO2.The interface between the SAM of dye and the substrate is an important factor to consider when designing dyes and surfaces in dye sensitized solar cells (DSSCs). The quality of the self-assembled monolayers of the dye on the TiO2 surface has a critical influence on the efficiency of the DSSCs. Creation of just a monolayer of dye on the surface could lead to an efficient current of photo-excited electrons to the TiO2 and degeneration of the dye by redox. This work, T-PAC dye showed island growth with some ad-layer that is not in contact with the surface, whereas the MP13 dye adsorption is laminar growth. Cuprite (Cu2O) is the initial and most common corrosion product for copper under atmospheric conditions. Copper could be a good replacement for noble metal as catalysts for methanol dehydrogenation. Knowledge about the structure of Cu2O(100) and Cu2O(111) surfaces could be used to obtain a deeper understanding of methanol dehydrogenation mechanisms with respect to adsorption sites on the surfaces. In this work, a detailed study was done of Cu2O(100) surface which revealed the possible surface structures as the result of different preparation conditions. Studies of the structure of Cu2O(100) and Cu2O(111) surfaces show that Cu2O(100) has a comparatively stable surface and reduces surface reactivity. As a consequence, dehydrogenation of methanol is more efficient on the Cu2O(111) surface. The hydrogen produced from methanol dehydrogenation is stored in oxygen adatom sites on both surfaces.QC 20161107
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Alkan, Ufuk. "The effects of solar radiation, adsorption and sedimentation of the population of enteric bacteria in marine waters". Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359000.
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Milani, Dia. "Modelling framework of solar assisted dehumidification system to generate freshwater from "Thin air"". Thesis, The University of Sydney, 2012. http://hdl.handle.net/2123/13581.
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Freshwater scarcity is a major obstacle of growth and prosperity for many nations in the world. Conventional centralised freshwater supply options in general are depleting and the unanticipated social and environmental costs of alternative solutions are emerging. Similar to energy, water sector may also need to explore renewable decentralised freshwater alternatives such as atmospheric moisture as discussed in this thesis. For hot and humid regions, condensed water is unwillingly discharged out of air-conditioning systems and the energy consumed for condensation to full humidity comfort level is wasted. Only a few limited small-scale experimental studies and no systematic modelling have been found in the literature on atmospheric water capture. This thesis works to fill some of this gap by developing an understanding of the fundamental factors that have and continue to challenge the development of technologies for atmospheric water capture. In this thesis, a framework is developed encompassing several modelling elements for assessment of feasibilities of moist air dehumidification technologies for atmospheric water capture. This framework integrates technical, meteorological and economic modelling elements. In the technosphere, detailed models of thermoelectric and absorption cooling are developed as potential dehumidification technologies. These models are interfaced to renewable energy input algorithms, namely solar photo-voltaic (PV) and solar-thermal. Solar energy collection technologies are also part of this framework which includes models of solar PV systems and evacuated tube collectors (ETCs). Studies of such integration of solar-assisted dehumidification and associated analysis for atmospheric water capture are limited in the literature. Fundamental solar energy input models are developed and interfaced to meteorological data to provide geographical location specific analysis. In this way the model framework is generic and applicable to any location on Earth where meteorological data is available. Finally, an economic modelling component completes the framework to provide comprehensive techno-economic assessments of different technologies for atmospheric water capture. This framework therefore provides a tool to support decision making related to feasibilities of different technologies associated with water capture from atmosphere. Along the way to developing the modelling framework, a detailed categorisation of dehumidification systems is established and a model to estimate condensation rates based on local climate data is built. The hurdle of condensation energy requirement is highlighted through simulation results. To alleviate this energy burden, an assessment of renewable solar energy input is then made. Techno-economic challenges for two different climates, Sydney and Abu Dhabi are examined and compared throughout this thesis providing comparisons for water and energy profiles. Several modelling components are developed and presented f or this purpose, requiring implementations in different modelling environments including Matlab, Trnsys, Homer and VBA. Based on the operation principles, dehumidification techniques are categorised into three categories in this thesis (Fig. 2.2). Gas separation membrane technologies were modelled but are not included in this thesis presentation because initial analysis showed they suffer from several key technical drawbacks primarily associated with the sensitivity to fluctuations in feed air temperature and humidity. Technologies in the cooling surfaces category in general use electrical or mechanical power to circulate and compress a refrigerant and cooling down conductive surfaces or coils. This process aims to decrease the temperature of moist air stream below dew point where water vapour molecules start to bond and settle forming the condensation stream. Amongst a wide range of cooling surface techniques, thermoelectric cooler (TEC) devices are attachable to cooling surfaces without using a refrigerant medium. A conceptual TEC dehumidification system is modelled in this thesis targeted at moist air streams with ambient temperature ranges (10-50) C and relative humidity ranges (10-100) %. For large-scale water production, the energy cost is calculated and found to be the major factor contributing to more than 95% of the total cost of generated water. This model is implemented for Sydney and Abu Dhabi case studies by using their annual typical meteorological weather data. This shows the generic nature of the applicability of the model and in this specific comparison confirms the influence of energy consumption over the cost of generated water in those two very different regions. However, lower local utility rates and favourable climatic conditions for dehumidification in Abu Dhabi show significant differentiation in water cost over Sydney. To confront excessive energy demands for atmospheric water capture, the idea of facilitating solar energy via PV panels is examined in this thesis. A comprehensive solar algorithm is developed and implemented to optimise solar collector positioning and for calculating solar penetration ratios for Sydney and Abu Dhabi. As far as the author is aware, this is the first time such optimal position calculation for Sydney and Abu Dhabi is done. It is found that optimal surface tilt angles for Sydney and Abu Dhabi are 32 and 22 respectively, while optimal surface azimuth angles for Sydney and Abu Dhabi are 195 and 16 respectively. This algorithm is generic in its structure allowing such calculation to be executed for any city in the world and is later used in this thesis for calculations associated with a new ETC diffuse at reflector (DFR) model. This thesis also presents a detailed economic model for prediction of utility costs with consideration for CAPEX, OPEX, subsidies and carbon taxation. It is found that investing a $338,000 on a PV array of 100 kW at current utility rates can meet 53% of energy demand of proposed dehumidification system and reduce LCOE by 6 c/kWh in Sydney. Solar PV array at current utility rates to feed proposed dehumidification system is found to be uneconomical for Abu Dhabi. Solar-thermal collectors represent an attractive option for driving refrigeration techniques. Evacuated tube collection technology has progressed significantly over the last few years and this technology is assessed in this thesis as a heat collector for absorption chillers. The role of DFR to improve the performance of ETC is highlighted and modelled. Results showed that DFR can significantly improve ETC performance by an average of 24.1% for Sydney and 22.9% for Abu Dhabi respectively. The optimisation of DFR is therefore an important factor for the enhancement of this solar energy collection technology and the algorithm developed in this thesis is generically applicable across geographical locations. The concept of solar refrigeration is reviewed and investigated for the implementation of sorption refrigeration. Sorption techniques use low-grade heat sources such as solar energy to convert thermal heat into chilling effect. This function is investigated for dehumidification of a moist air stream via cooling coils. A conceptual absorption model is developed in TRNSYS to calculate overall energy demand and water productivity. An ASHRAE algorithm is developed and implemented to cross validate the TRNSYS model. This absorption model was used in an optimisation analysis and showed water productivity improvement of 29% for Sydney and 34% for Abu Dhabi, while energy demand can be reduced by 22% for Sydney and 55% for Abu Dhabi. Unlike Sydney, the cumulative cost of generated water is declining over time in Abu Dhabi reaching $15 /kL. If this system is projected to work during the day only, solar penetration ratio will substantially increase and could meet the entire diurnal load for dehumidification in Abu Dhabi. If the capital cost of developing such system is affordable, absorption model can be further optimised to specifically match local conditions in respect to solar radiation and energy sources where the cost of generated water can economically compete with other conventional sources. In regions such as Abu Dhabi, the idea of having small-scale dehumidification system where the energy demand is mostly met by solar radiation and the volume of generated water is freely controlled and managed by household seems appealing.
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Vural, Kivilcim Basak. "Adsorption Of Gold Atoms On Anatase Tio2 (100)-1x1 Surface". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610962/index.pdf.
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In this work the electronic and structural properties of anatase
TiO2 (100) surface and gold adsorption have been investigated
by using the first-principles calculations based on density
functional theory (DFT). TiO2 is a wide band-gap material and
to this effects it finds numerous applications in technology such
as, cleaning of water, self-cleaning, coating, solar cells and so
on.
Primarily, the relation between the surface energy of the anatase
(100)-1x1 phase and the TiO2-layers is examined. After
an appropriate atomic layer has been chosen according to the
stationary state of the TiO2 slab, the adsorption behavior of
the Au atom and in the different combinations are searched for both
the surface and the surface which is supported by a single Au
atom/atoms. It has been observed that a single Au atom tends to
adsorb to the surface which has an impurity of Au atom or atoms.
Although, the high metal concentration on the surface have increased
the strength of the adsorption, it is indicated that the system
gains a metallic property which is believed to cause problems in the
applications. In addition, the gold clusters of the dimer (Au2)
and the trimer (Au3) have been adsorbed on the surface and
their behavior on the surface is investigate. It is observed that
the interaction between Au atoms in the atomic cluster each other is
stronger than that of gold clusters and the surface.
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Vieira, Herbert Melo. "Estudo teórico e experimental de coletor adsortivo". Universidade Federal da Paraíba, 2009. http://tede.biblioteca.ufpb.br:8080/handle/tede/5392.
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This paper presents simple and feasible alternatives that will help improve the performance of a refrigeration system by adsorption, which uses solar energy as a heat source to promote the raising of the temperature of the porous bed, thus occurring, the process of desorption, which is the separation of the adsorbent adsorbato. The studies were made in the modification of the geometry of the absorber plate for triangular tube, which caused an increase in the area provided between the plate and the adsorbent, which were analyzed by a computer program that simulates the cycle of a refrigeration system by adsorption . Another study proposed is the removal of a concentric screen, which aims to promote the flow of radial adsorbato during the processes of sorption, the withdrawal of this screen aims to verify whether the change in the flow of adsorbato of radial to the axial an increase in the concentration of adsorbato the porous bed and if the phenomenon occurs throughout the entire adsorptive column, thus enabling a constructive process of collecting tubular simple plan, this phase of work, is shown through experimental results, verifying the concentration and temperature in two adsorptive columns during the adsorption.
O presente trabalho apresenta alternativas viáveis e simples que venham contribuir para melhorar o desempenho de um sistema de refrigeração por adsorção, que utiliza a energia solar como fonte de calor para promover a elevação da temperatura do leito poroso, ocorrendo assim, o processo de dessorção, que é a separação do adsorbato do adsorvente. Os estudos feitos constituíram na modificação da geometria da placa absorvedora de tubular para triangular, o que ocasionou um aumento na área de contanto entre a placa e o adsorvente, que foram analisadas através de um programa computacional que simula o ciclo de um sistema de refrigeração por adsorção. Outro estudo proposto é a retirada de uma tela concêntrica, que tem como finalidade promover o fluxo radial do adsorbato durante os processos de adsorção/dessorção, a retirada desta tela tem como objetivo verificar se com a modificação do fluxo do adsorbato de radial para axial a um aumento na concentração de adsorbato no leito poroso e se ocorre o fenômeno adsortivo ao longo de toda coluna, possibilitando assim, um processo construtivo do coletor plano tubular mais simples, esta etapa do trabalho, é apresentada através de resultados experimentais, verificando a concentração e temperatura em duas colunas adsortivas durante o período de adsorção.
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Das, Saikat. "FUNDAMENTAL STUDIES OF SURFACTANT TEMPLATED METAL OXIDE MATERIALS SYNTHESIS AND TRANSFORMATION FOR ADSORPTION AND ENERGY APPLICATIONS". UKnowledge, 2015. http://uknowledge.uky.edu/cme_etds/48.
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This work addresses fundamental aspects of designing templates and curing conditions for the synthesis of mesoporous metal oxide thin films. The first section addresses selection of cationic-carbohydrate surfactant mixtures to synthesize templated silica thin films for selective adsorption of simple carbohydrates based on molecular imprinting. Nuclear magnetic resonance and fluorescence spectroscopy results suggest a novel structure for mixtures of alkyl glucopyranosides or xylopyranosides with cationic (trimethylammonium) surfactants. Despite thermodynamically favorable mixing, the carbohydrate headgroups in the mixed micelle adopt an inverted configuration with their headgroups in the micelle core, and therefore are inaccessible for molecular imprinting. This orientation occurs even when the alkyl tail length of the carbohydrate surfactant is greater than that of the cationic surfactant, but this limitation can be overcome by introducing a triazole linker to the carbohydrate surfactant. The next section addresses the effects of aging conditions on the structural and chemical evolution of surfactant templated silica thin films. The third section describes the synthesis of carbohydrate/cationic surfactant imprinted silica thin films with orthogonally oriented cylindrical pores by modifying the glass surface with a random copolymer. The last part of the dissertation addresses the effect of pore orientation on the transformation mechanism of block copolymer templated titania thin films during high temperature curing. Mesoporous titania thin films can be used for photochemical and solar cell applications, but doing so requires addressing the tradeoff between loss of mesostructural order and growth of crystallinity during thermal treatment. By using advanced x-ray scattering techniques it has been shown that the titania films with vertically oriented pores can better withstand the anisotropic stress that develops during thermal treatment compare to titania films with mixed pore orientation. For instance, films with parallel or mixed pores can only be heated at 400 °C for a brief time (~10 min) without loss of order, while orthogonally oriented films can be heated at 550 °C or greater for extended time periods (on the order of hours) without significant loss of long-range mesopore structure. Detailed kinetic modeling was applied to enable the comparison of activation energy for mesostructure loss in films as a function of pore orientation and thickness.
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Ghaghazanian, Arash. "System Integration of PV/T Collectors in Solar Cooling Systems". Thesis, Högskolan Dalarna, Energiteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:du-19554.
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The demand for cooling and air-conditioning of building is increasingly ever growing. This increase is mostly due to population and economic growth in developing countries, and also desire for a higher quality of thermal comfort. Increase in the use of conventional cooling systems results in larger carbon footprint and more greenhouse gases considering their higher electricity consumption, and it occasionally creates peaks in electricity demand from power supply grid. Solar energy as a renewable energy source is an alternative to drive the cooling machines since the cooling load is generally high when solar radiation is high. This thesis examines the performance of PV/T solar collector manufactured by Solarus company in a solar cooling system for an office building in Dubai, New Delhi, Los Angeles and Cape Town. The study is carried out by analyzing climate data and the requirements for thermal comfort in office buildings. Cooling systems strongly depend on weather conditions and local climate. Cooling load of buildings depend on many parameters such as ambient temperature, indoor comfort temperature, solar gain to the building and internal gains including; number of occupant and electrical devices. The simulations were carried out by selecting a suitable thermally driven chiller and modeling it with PV/T solar collector in Polysun software. Fractional primary energy saving and solar fraction were introduced as key figures of the project to evaluate the performance of cooling system. Several parametric studies and simulations were determined according to PV/T aperture area and hot water storage tank volume. The fractional primary energy saving analysis revealed that thermally driven chillers, particularly adsorption chillers are not suitable to be utilizing in small size of solar cooling systems in hot and tropic climates such as Dubai and New Delhi. Adsorption chillers require more thermal energy to meet the cooling load in hot and dry climates. The adsorption chillers operate in their full capacity and in higher coefficient of performance when they run in a moderate climate since they can properly reject the exhaust heat. The simulation results also indicated that PV/T solar collector have higher efficiency in warmer climates, however it requires a larger size of PV/T collectors to supply the thermally driven chillers for providing cooling in hot climates. Therefore using an electrical chiller as backup gives much better results in terms of primary energy savings, since PV/T electrical production also can be used for backup electrical chiller in a net metering mechanism.
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Tatsidjodoung, Parfait. "Procédé de stockage d'énergie solaire thermique par adsorption pour le chauffage des bâtiments : modélisation et simulation numérique". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENA012/document.
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Les systèmes de stockage de chaleur par sorption (SSCS) ouvrent de nouvelles perspectives dans l'exploitation de l'énergie solaire pour le chauffage des bâtiments résidentiels. En effet, ces systèmes sont très prometteurs dans la mesure où ils permettent un stockage de chaleur sur de longues périodes (le stockage est réalisé sous forme de potentiel chimique) et offrent des densités énergétiques importantes (jusqu'à 230 kWh/m3 de matériau en moyenne) en comparaison aux systèmes classiques comme le stockage par chaleur sensible (qui, pour le cas de l'eau, dispose d'une densité énergétique moyenne d'environ 81 kWh/m3 de matériau pour une variation de 70°C) et le stockage par chaleur latente (qui atteint des densités énergétiques de 90 kWh/m3 de matériau).La présente thèse vise à étudier les performances d'un système de stockage de chaleur par sorption à base de zéolithe 13X intégré à un bâtiment type basse consommation. Des modèles mathématiques de transferts couplés de masse et de chaleur des différents composants du système sont développés et validés par le biais de l'expérimentation. La simulation numérique dynamique, comme outil de dimensionnement, permet, à partir des résultats d'analyses de sensibilité paramétrique sur les différents composants du système, l'étude de son fonctionnement et les critères de sa faisabilitéSorption heat storage systems (SHSS) open new perspectives for solar heating of residential buildings. These systems allow long term heat storage (storage is done in the form of chemical potential) and offer high energy densities (up to 230 kWh/m3 of material on average) compared to conventional heat storage systems such as sensible heat storage (which, for the case of water, has an average energy density of approximately 81 kWh/m3 of material for a temperature change of 70 °C) and latent heat storage (nearly reaching energy densities of 90 kWh/m3 of material on average).This thesis aims to study the performance of a sorption solar heat storage system on zeolite 13X, integrated to low-energy building. Mathematical models of coupled heat and mass transfer of various components of the system are developed and validated through experimentation. Numerical dynamic simulations allow to study the functioning of the SHSS in specific conditions, and its design with the results from the parametric sensitivity analysis on its components
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Alessandrini, Stefano. "Experimental analysis and dynamic simulation of solar cooling systems". Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11128.
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2013/2014Il continuo aumento della richiesta di energia elettrica e la conseguente crescita dei valori di anidride carbonica nell'atmosfera terrestre crea sempre più la necessità di attuare modifiche sostanziali non solo nei metodi di produzione dei settori energetico e industriale, ma anche nella vita di ogni abitante del pianeta. Questa tesi analizza la possibilità di utilizzare l'energia solare per la produzione di acqua fredda grazie alla contemporaneità tra la disponibilità di energia rinnovabile e la richiesta di raffrescamento durante il periodo estivo. Due diversi impianti sperimentali, dotati di collettori solari a tubi evacuati commerciali e chiller ad adsoprbimento di piccole dimensioni (20 kW), sono stati monitorati ed i primi risultati sperimentali sono presentati in questo studio. Per studiare soluzioni diverse e trovare un design ottimale, un modello di simulazione dinamica è stato creato e testato utilizzando il software commerciale TRNSYS 17.
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Vodianitskaia, Paulo José. "Estudo teórico e experimental de um chiller a adsorção para sistemas de ar condicionado solar". Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/8957.
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Human society in general, and Brazil in particular, face severe scenarios, from restricted energy supply to climate change and other challenges for a sustainable future. Thus renewable energy alternatives offering lower environmental and social impacts such as solar energy are subjects of special interest. The present work refers to this challenging picture. As a way to apply renewable energy, solid adsorption air conditioning favors energy security and contributes to the mitigation of greenhouse gases due to the lower dependency in regard to primary energy. It allows to a reduction on demand peaks, and to a natural adjustment between supply and demand levels. Moreover, the materials used in such systems present low environmental impact, especially the refrigerant fluid: water, abundant in nature and non-toxic. The general objective of this work is the development of an experimental chiller using local technology, resulting in a state-of-the-art performance level. Specific objectives include the development of a representative model for the adsorber, the comparison of adsorption kinetics between two fractions of silica gel, the evaluate how specific heat and mass diffusion influence the chiller performance. The numerical model contributions are related to the use of specific heat of the adsorbed phase, and mass diffusion for cycle characterization. The model resulted representative of the experimental behavior. COP was found to be 0,53 and SCP is 68 W/kg for 2.0 mm beads. These values are comparable or higher to the ones reported in literature for silica gel in loose grains. The use of a crushed silica gel of smaller size (026 mm) resulted in lower level of performance, which is probably due to the reduction of porosity after crushing.
A humanidade em geral, e o Brasil em particular, enfrentam duros cenários de restrição de energia, mudanças climáticas e outros desafios para um futuro sustentável. Assim, alternativas de energia renovável, de menor impacto ambiental e social, como a energia solar, se tornam objeto de especial interesse. É dentro desse quadro desafiador que se insere o presente trabalho. Como aplicação de energia renovável, a climatização a adsorção se configura como fator de segurança energética e contribui para a mitigação das emissões de gases efeito estufa, ao reduzir a dependência de energia primária. Conduz à redução de picos de demanda, e apresenta um ajuste natural entre demanda e oferta. Além disso, os materiais utilizados são de baixo impacto ambiental, especialmente o refrigerante: a água, abundante na natureza e atóxica. O objetivo geral do presente trabalho é desenvolver um chiller experimental com tecnologia nacional que permita atingir níveis de desempenho comparáveis ao estado da arte. Os objetivos específicos são: desenvolver um modelo representativo para o reator adsortivo, comparar a cinética de adsorção em duas granulometrias de sílica gel, e estudar a influência do calor específico e da difusão de massa. O modelo numérico trouxe como contribuições originais considerar o calor específico da fase adsorvida e a difusão de massa para caracterização do ciclo. O modelo resultou representativo do comportamento verificado experimentalmente. Foram obtidos COP de 0,53 e SCP de 68 W/kg para partículas de adsorvente de 2,0 mm, valores comparáveis ou superiores aos registrados na literatura para sílica gel em grãos soltos. A fração de granulometria menor (0,26 mm) teve desempenho inferior, provavelmente devido à redução de porosidade após britagem.
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Wilson, Earle Anthony. "Investigation of renewable, coupled solar-hydrogen fuel generation with thermal management systems suitable for equatorial regions". Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4508.
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Solar Energy and Hydrogen (energy carrier) are possible replacement options for fossil fuel and its associated problems of availability and high prices which are devastating small, developing, oil-importing economies. But a major drawback to the full implementation of solar energy, in particular photovoltaic (PV), is the lowering of conversion efficiency of PV cells due to elevated cell temperatures while in operation. Also, hydrogen as an energy carrier must be produced in gaseous or liquid form before it can be used as fuel; but its‟ present major conversion process produces an abundance of carbon dioxide which is harming the environment through global warming. In search of resolutions to these issues, this research investigated the application of Thermal Management to Photovoltaic (PV) modules in an attempt to reverse the effects of elevated cell temperature. The investigation also examined the effects of coupling the thermally managed PV modules to a proton exchange membrane (PEM) Hydrogen Generator for the production of hydrogen gas in an environmentally friendly and renewable way. The research took place in Kingston, Jamaica. The thermal management involved the application of two cooling systems which are Gravity-Fed Cooling (GFC) and Solar-Powered Adsorption Cooling (SPAC) systems. In both systems Mathematical Models were developed as predictive tools for critical aspects of the systems. The models were validated by the results of experiments. The results of the investigation showed that both cooling systems stopped the cells temperatures from rising, reversed the negative effects on conversion efficiency, and increased the power output of the module by as much as 39%. The results also showed that the thermally managed PV module when coupled to the hydrogen generator impacted positively with an appreciably increase of up to 32% in hydrogen gas production. The results of this work can be applied to the equatorial belt but also to other regions with suitable solar irradiation. The research has contributed to the wider community by the development of practical, environmentally friendly, cost effective Thermal Management Systems that guarantee improvement in photovoltaic power output, by introducing a novel way to use renewable energy that has potential to be used by individual household and/or as cottage industry, and by the development of Mathematical Tools to aid in photovoltaic power systems designs.
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Oscarsson, Johan. "Towards Mixed Molecular Layers for Dye-Sensitized Solar Cells : A Photoelectron Spectroscopy Study". Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301164.
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The increasing demand for renewable energy has led to substantial research on different solar cell technologies. The dye-sensitized solar cell (DSC) is a technology utilizing dye molecules for light absorption. Dye molecules are adsorbed to a mesoporous semiconductor surface and after light absorption in the dye, charge separation occurs at this interface. Traditionally, DSCs have used layers of single dye species, but in recent efforts to enhance power conversion efficiency, more complex molecular layers have been designed to increase the light absorption. For example, the most efficient DSCs use a combination of two dye molecules, and such dye co-adsorption is studied in this thesis. A key to highly efficient DSCs is to understand the dye/semiconductor interface from a molecular perspective. One way of gaining this understanding is by using an element specific, surface sensitive technique, such as photoelectron spectroscopy (PES). In this thesis, PES is used to understand new complex dye/semiconductor interfaces. Dyes adsorbed to semiconductor surfaces are analyzed using PES in terms of geometric and electronic surface structure. The investigations ultimately target the effects of co-adsorbing dyes with other dyes or co-adsorbents. PES shows that Ru dyes can adsorb in mixed configurations to TiO2. Co-adsorption with an organic dye affects the configuration of the Ru dyes. As a consequence, shifts in energy level alignment and increased dye coverage are observed. The dyes are affected at a molecular level in ways beneficial for solar cell performance. This is called collaborative sensitization and is also observed in todays most efficient DSC. Dye molecules are generally sensitive to high temperatures and the substantial decrease in power conversion efficiency after heat-treatment can be understood using PES. Furthermore, comparing two mesoscopic TiO2 morphologies used in DSCs show differences in trap state density in the band gap, explaining the photovoltage difference in DSCs comprising these morphologies. Using mixed molecular layers on NiO results in significant improvements of p-type DSC power conversion efficiency. PES shows that changed adsorption configuration contribute to this effect. This thesis shows that PES studies can be used to obtain insight into functional properties of complex DSC interfaces at a molecular level.
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Peic, Antun. "Mesoporous thin-film materials studied by optical waveguide spectroscopy". Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518293.
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A method was developed to access the interior of light-guiding structures in order to exploit the enhanced sensing potential of the highly confined electromagnetic field distributions, located within the core of a waveguide. The work presented in this thesis explores therefore the possibilities of optical waveguide spectroscopy utilising transparent mesoporous thin-film waveguides deposited on top of athin gold layer. These multi-layer assemblies are employed in a prism-coupling attenuated total internal reflection (ATR) configuration. The angular read-out of the reflected light intensity allows label-free detection schemes with high sensitivity to changes of the dielectric environment in the case of the presence of analyte molecules within the probing region. This optical waveguide spectroscopy technique has been used to study the real-timediffusion of Ruthenium 535-bisTBA (N-719) dye into mesoporous nanocrystalline titaniumdioxide films. The porous films were prepared on top of gold substrates and prism coupling was used to create a guided wave in the nanocrystalline film. Dying was carried out by bring the film into contact with a 3 x 10-4 moldm-3 dye solution and using optical waveguide spectroscopy to monitor the change in both the refractive index and theextinction coefficient of the nanoporous layer as dye diffused into the porous network. Dyeuptake in a 1.27 μm film was slow with the refractive index of the film still increasing after 22 hours.
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Telegang, Chekem Cedric. "Matériaux carbonés multifonctionnels à porosité contrôlée à partir des ressources végétales tropicales : application au traitement de l'eau par photocatalyse". Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0026/document.
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La double fonction absorption-photodégradation des composites CA-TiO2 vis-à-vis des polluants biorécalcitrants est une alternative prometteuse pour le traitement de l’eau par voie solaire. Dans ce travail, des composites CA-TiO2 sont élaborés suivants trois méthodes simples basées sur l’utilisation des biomasses trouvées dans la sous région ensoleillée de l’Afrique subsaharienne. Les charbons actifs (CA) obtenus après pyrolyse des biomasses développent une structure poreuse qui se modifie ensuite en fonction de la voie de fixation des nanoparticules TiO2 (NPs-TiO2) pour l’obtention des composites. Parmi les trois vois de fixation du TiO2, l’imprégnation du CA avec le sol de NPs-TiO2 préformées conduit à des matériaux (CAT.SX) avec du TiO2 déposé de façon homogène à la « surface externe » du CA. Cette microtexture permet un meilleur couplage des propriétés adsorption-photodégradation, favorables aux performances de dépollution évaluées à l’échelle de laboratoire sur des solutions de phénol à 100 mg.L-1. Le réseau pores/surface spécifique est moins développé sur les composites obtenus par fixation in situ des NPs-TiO2 sur du CA imprégné de gel de TiO2 (CAT.GX), ou par pyrolyse directe de biomasse pré-imprégnée de NPs-TiO2 (CAT.SBX) ; ce qui explique les performances de dépollution moins élevées enregistrées pour ces deux dernières familles de catalyseurs. Les cinétiques d’élimination du polluant obtenues après plusieurs cycles successifs d’utilisation des catalyseurs CAT.SX ont été correctement simulées avec un modèle dont le formalisme tient compte de la double fonctionnalité des catalyseurs. Ce modèle permet d’envisager le dimensionnement d’installations solaires en condition réelle d’utilisation de ces nouveaux catalyseurs en zones fortement ensoleilléeAdsorption/photodegradation dual property of AC-TiO2 composites materials towards biorefractory pollutants is a promising issue for solar water treatment. In this work, AC-TiO2 hybrid materials have been synthesized through 03 novel routes based on the conversion of typical biomasses, abundantly found in the subsaharian African sunny areas. Biomasses pyrolysis derived activated carbon (AC) developed a porous structure which is modified differently according to the method used to fix TiO2 nanoparticules (TiO2-NPs). AC impregnated with a sol containing TiO2-NPs suspension provides the derived composite material (CAT.SX) with TiO2-NPs regularly deposited at the “external surface”, leading to a good coupling of adsorption/photodegradation activities towards phenol elimination in 100 mg.L-1 polluted water, carried out on lab scale experiments. Pore/surface area network is less developed on composites obtained after in situ fixation of TiO2-NPs on TiO2 gel impregnated AC (CAT.GX), or obtained after direct pyrolysis of TiO2-NPs impregnated biomass (CAT.SBX) – which infers lesser decontamination performances for these two latter families of catalysts. Pollutant elimination kinetics curves depicted after recycling of CAT.SX over several running water treatment was simulated with a suitable mathematical model which takes into consideration the dual functionalities of the elaborated material. The established model is a promising attempt for future dimensioning of real solar water treatment plants, operating in sunny areas with the new composite catalysts
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Nedjar, Achraf. "Dimensionnement et optimisation d'un système photovoltaïque thermique avec intégration dans le bâtiment pour la production de froid". Electronic Thesis or Diss., CY Cergy Paris Université, 2024. http://www.theses.fr/2024CYUN1285.
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Cette thèse présente une étude complète sur les performances d'un système hybride photovoltaïque / thermique (PVT) dimensionné pour la production de froid par adsorption. Le logiciel de simulation dynamique TRNSYS a été utilisé pour simuler le système tenant compte des conditions météorologiques d'Alger situé au nord de l'Algérie. L'étude prend en considération la génération effective d'énergie thermique par les capteurs, ainsi que la variation réelle des performances du refroidisseur à adsorption. L'objectif principal étant de dimensionner et d'optimiser le système solaire avec un stockage calorifique afin de garantir une production de froid stabilisée durant toute l'année.Préalablement, une revue approfondie de la littérature a été dressée, examinant les systèmes hybrides PVT, les systèmes de refroidissement à sorption solaire, ainsi que les recherches existantes qui explorent la combinaison de ces deux technologies.En second lieu, une étude numérique sur la géométrie de l'échangeur du collecteur PVT a permis de déterminer que la géométrie en nappe offre les meilleurs rendements thermique et global. De plus, la gamme de température de l'eau chaude délivrée par ces capteurs, notamment les collecteurs DualSun correspond aux températures de fonctionnement des machine de froid solaire à adsorption.Ensuite, les composants du système PVT - Adsorption ont été dimensionné et un modèle mathématique a été élaboré et validé par des travaux expérimentaux publiés. L'étude des performances du système pour une production de froid entre 4°C et 8 °C a révélé que les capteurs hybrides DualSun offrent une production annuelle optimale. En outre, le système de refroidissement par adsorption permet de répondre à 36 % du besoin le long de l'année. La différence de température entre l'intérieur et l'extérieur de l'enceinte à refroidir permet d'équilibrer l'offre et la demande de froid. Il a aussi été relevé que le rendement thermique est fortement affecté par la température ambiante alors que le rendement électrique est plus sensible au rayonnement solaire.L'analyse des pertes du dispositif de stockage a indiqué que celles-ci dépendent d'une part, de la différence de température entre l'intérieur et l'extérieur du ballon de stockage avec des valeurs plus significatives pendant la saison estivale. D'autres part, les pertes dépendent aussi du volume du ballon qui a été optimisé en vue de limiter l'échange thermique avec l'extérieur.L'analyse économique du système PVT - Adsorption proposé a révélé sa viabilité sous certaines conditions clés, principalement liées au coût de l'électricité. La rentabilité est atteinte à condition que le coût de l'électricité dépasse le seuil de 0,08 USD/kWh.L'analyse environnementale a permis de déterminer le taux de l'atténuation des émissions de gaz à effet de serre en fonction des facteurs de conversion liés à la production d'électricité. Le système contribue à l'atténuation d'environ 30 tonnes de dioxyde de carbone par an.Les performances du système PVT - Adsorption ont été également étudiées sous diffèrent climats, méditerranéen, subtropical humide et désertique aride. Les résultats ont indiqué que le système est plus productif sous un climat désertique aride et plus efficace sous un climat méditerranéen, qui présente une meilleure régularité entre l'offre et la demande en matière de refroidissement.La combinaison des technologies PVT et adsorption solaire se révèle ainsi être efficiente pour la production de froid et peut contribuer de façon significative pour atteindre les objectifs du développement durableThis thesis presents a comprehensive study of a hybrid photovoltaic/thermal (PVT) system performance dimensioned for cold production by adsorption. TRNSYS dynamic simulation software was used to simulate the system, considering meteorological conditions in Algiers, northern Algeria. The study takes into account the actual generation of thermal energy by the collectors, as well as the actual variation in performance of the adsorption chiller. The main objective is to dimension and optimize the solar system with thermal energy storage to guarantee stabilized cooling production throughout the year.Prior to this, an extensive literature review was carried out, examining PVT hybrid systems, solar sorption cooling systems, as well as existing research exploring the combination of these two technologies.Secondly, a numerical study of the PVT collector's exchanger geometry determined that the water table geometry offers the best thermal and overall efficiency. In addition, the temperature range of the hot water delivered by collectors with this geometry, notably DualSun manifolds, corresponds to the operating temperatures of adsorption solar chillers.Next, the PVT - Adsorption system components were dimensioned and a mathematical model was developed and validated by published experimental work. A study of the system's performance for cooling needs between 4°C and 8°C revealed that DualSun hybrid collectors offer optimum annual production. Furthermore, the adsorption cooling system is able to meet 36% of year-round demand. The temperature difference between the inside and outside of the cooling enclosure balances cooling supply and demand. It was also noted that thermal efficiency is strongly affected by ambient temperature, whereas electrical efficiency is more sensitive to solar radiation.Analysis of storage system losses showed that these depend, on the one hand, on the temperature difference between the inside and outside of the storage tank, with more significant values during the summer season. On the other hand, losses also depend on the volume of the storage tank, which has been optimized to limit heat exchange with the outside.Economic analysis of the proposed PVT - Adsorption system has revealed its viability under certain key conditions, mainly related to the cost of electricity. Profitability is achieved provided that the cost of electricity exceeds the threshold of 0.08 USD/kWh.The environmental analysis determined the rate of mitigation of greenhouse gas emissions as a function of the conversion factors associated with electricity generation. The system contributes to the mitigation of around 30 tons of carbon dioxide per year.The performance of the PVT - Adsorption system was studied under different climates: Mediterranean, humid subtropical and arid desert. The results showed that the system is more productive in an arid desert climate and more efficient in a Mediterranean climate, which offers better regularity between cooling supply and demand.In sum, the combination of PVT and solar adsorption technologies is therefore proving to be an efficient way of producing cold, and can make a significant contribution to achieving sustainable development goals
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Karlsson, Maria. "Quantum Chemical Investigations of Phenol and Larger Aromatic Molecules on TiO2 Surface". Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2715.
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Adsorption of organic molecules at a surface of titanium dioxide (101) anatase is studied using quantum-chemical density functional theory. Anatase can be used in solar cells. For the clean anatase surface the band gap is so large that only UV-light can excite electrons. Different groups with conjugated systems are attached to obtain a more suitable band gap.
Phenol was attached in different positions to a cluster of anatase and geometry optimized using the B3LYP-functional. The geometry that was energetically most favorable was used to put in phenylmethanol, phenylethanol, naphthol, 2-phenanthrol, 1-pyrol and 2-perylol. To give a more realistic model of phenol at anatase, a study of a two- dimensional periodic anatase surface was also made.
Molecular orbitals were calculated to study the overlap between HOMO and LUMO orbitals. The calculation shows that phenol will remain as a molecule and will not dissociate. The band gap gets smaller when molecules are attached at the cluster and with 2-perylol it reaches the energy of visible light.
The molecular orbitals for HOMO, LUMO and LUMO of the adsorbed molecule were investigated. HOMO was localized at the molecule, LUMO at the cluster and LUMO of the adsorbed molecule move closer to the energy of LUMO when the number of rings increases.
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Su, Lingcheng. "Soil contamination and plant uptake of metal pollutants released from Cu(In, Ga)Se₂ thin film solar panel and remediation using adsorbent derived from mineral waste material". HKBU Institutional Repository, 2018. https://repository.hkbu.edu.hk/etd_oa/552.
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The Cu(In,Ga)Se2 (CIGS) thin-film solar panels (TFSPs) are widely used in integrated photovoltaic (PV) and solar power systems because of their perfect PV characteristics and ductility. However, the semiconductor layers of these panels contain potentially toxic metals. In this study, the potential environmental pollution arisen by CIGS TFSP treated as construction trash at the end of their useful life was examined. Acid extraction was used to simulate leaching toxicity followed by burying CIGS TFSP material in different soils, namely a synthetic soil, a Mollisol, and an Oxisol, to determine whether metal pollutants might be released into the soil. A vegetable, Brassica parachinensis L. H. Bariley (VegBrassica), was selected to grow in these polluted soils to investigate the uptake of metals and their bioaccumulation. The simulative remediation of contaminated soils was carried out using a remediation module created by the combination of activated carbon and modified mineral waste material (MMWM) in this research. The activated carbon derived from the waste biomass material was produced by an environmental friendly method, and the MMWM was obtained through a thermal dehydroxylation treatment. The physiochemical properties of MMWM, with focusing on mineral phase transformation, were related to the changes in surface morphology due to dehydroxylation occurred during the process of thermal treatment of MMWM samples, and the adsorption performances of metal (lead, Pb) and organic compound (methyl orange, MO) onto this newly modified MMWM were studied. Furthermore, an end-of-life treatment method was designed and proposed for harmless disposal of CIGS TFSP. Various metals, including Pb, zinc (Zn), nickel (Ni), chromium (Cr), gallium (Ga), copper (Cu), indium (In) and aluminum (Al) were found to be released into the soil and caused contamination when scrapped end-of-life CIGS TFSP were buried, and the rates of metal release changed with the variations of both the amounts of CIGS TFSP material in the soil and the soil properties. The increases in concentrations of heavy metals such as Zn, Cu, Ni, Ga, Pb, In, and Cr were correlated with the amounts of CIGS TFSP material added in soils. The Pollution Index and the Nemerow Contamination Index calculated from our results confirmed that, when buried, the CIGS TFSP material polluted the soil. Plants grew well in the synthetic soil and the Mollisol, but those in the Oxisol showed prominent signs of chlorosis and died after 30 days. The bioaccumulation factor (BF) and concentration of Zn were 3.61 and 296 mg/kg, respectively in VegBrassica grown in the synthetic soil with 10% (200 g to 2 kg of soil) of added CIGS TFSP, while the BF and concentration of In were 3.80 and 13.72 mg/kg, respectively in VegBrassica grown in the Mollisol, indicating that bioaccumulation occurred. The thermally treated MMWM samples showed morphological transformation mainly on surface based on the scanning electron microscopy (SEM) observations, and an increasing trend in BET specific surface area (SSA) from 120 to 500 ℃ followed by a decreasing trend up to 1000 ℃. Thermal modification had successfully improved Pb adsorption capacity up to 515 mg/g, corresponding to MMWM modified at 600 ℃ with an SSA of 6.5 m2/g. The MO adsorption capacity was also improved after thermal treatment of MMWM, which performed the best adsorption of 87.6 mg/g at 400 ℃. The adsorption of Pb and MO were mainly chemisorption and monolayer coverage, as pseudo-second-order model and Langmuir equation displayed good relationships of correlation for Pb and MO adsorption data. It is therefore indicated that the newly designed soil remediation modules could significantly remove metals from the contaminated soils. In summary, c
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Cavalcanti, Vladyr Yuri Soares de Lima. "Simulação computacional de um tomógrafo capacitivo elétrico paralelo aplicado ao processo adsortivo". Universidade Federal da Paraíba, 2009. http://tede.biblioteca.ufpb.br:8080/handle/tede/5391.
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Previous issue date: 2009-04-30Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This thesis aims to computationally simulate the electronic transducer for a parallel electrical capacitance tomography, can generate a voltage level used for image reconstruction of the adsorption phenomenon occurred in the adsorptive bed. This simulation was performed using a computer program like SPICE (Simulation Program with Integrated Circuit Emphasis) for the purpose of defining the parameters for its construction, dedicated to the application of the adsorptive bed bench in a glass case studies of the adsorptive process. This technique uses capacitive sensors coupled to an electronic transducer that will generate a voltage signal associated with the distribution of dielectric permittivity of the medium. The simulation is developed to simulate the main circuit, a differentiator, fitted with high frequency OPA 2690. The simulated model is a simple circuit with a transmitter and a receiver. The results show the technical feasibility of the project being proposed for future work to implement a prototype of the electronic transducer of electrical capacitance tomography applied to the study of the adsorption process.
Esta dissertação tem como objetivo simular computacionalmente o transdutor eletrônico para um tomógrafo capacitivo elétrico paralelo capaz de gerar um nível de tensão utilizado para a reconstrução da imagem do fenômeno de adsorção ocorrido no leito adsortivo. Esta simulação foi realizada em um programa computacional do tipo SPICE (Programa de Simulação com Ênfase em Circuito Integrado) com a finalidade de definir os parâmetros para a sua construção, voltado para a aplicação no leito adsortivo de uma bancada em vidro para estudos do processo adsortivo. Esta técnica utiliza sensores capacitivos acoplados a um transdutor eletrônico que vão gerar um sinal de tensão associado à distribuição da permissividade dielétrica do meio. A simulação desenvolvida consiste em simular o circuito principal, um diferenciador, montado com OPA 2690 de alta freqüência. Simulou-se de um modelo de circuito simples, com um transmissor e um receptor. Os resultados apresentados mostram a viabilidade técnica do projeto, sendo proposto para trabalhos futuros a implementação de um protótipo do transdutor eletrônico do tomógrafo capacitivo elétrico aplicado ao estudo do processo de adsorção.
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Ghani, Fatemeh. "Nucleation and growth of unsubstituted metal phthalocyanine films from solution on planar substrates". Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6469/.
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Organic solar cells (OSC) are interesting as low cost alternative to conventional solar cells. Unsubstituted Metal-phthalocyanines (Pc) are excellent electron donating molecules for heterojunction OSC. Usually organic solar cells with Pcs are produced by vapor deposition, although solution based deposition (like spin casting) is cheaper and offers more possibilities to control the structure of the film. With solution based deposition several parameters (like temperature, solvent and etc.) affect the self-organized structure formation via nucleation and growth. The reason why vapor deposition is typically used is the poor solubility of the metal-phthalocyanines in most common solvents. Furthermore the process of nucleation and growth of Pc aggregates from solution is not well understood. For preparation of Pc films from solution, it is necessary to find the appropriate solvents, assess the solution deposition techniques, such as dip coating, and spin casting. It is necessary to understand the nucleation and growth process for aggregation/precipitation and to use this knowledge to produce nanostructures appropriate for OSC. This is important because the nanostructure of the films determines their performance.
In this thesis, optical absorption and the stability of 8 different unsubstituted metal Pc’s were studied quantitatively in 28 different solvents. Among the several solution based deposited thin films produced based on this study, copper phthalocyanine (CuPc) dissolved in trifluoroacetic acid (TFA) is chosen as a model system for an in-depth study. CuPc has sufficient solubility and stability in TFA and upon solution processing forms appropriate structures for OSCs. CuPc molecules aggregate into layers of nanoribbons with a thickness of ~ 1 nm and an adjustable width and length. The morphology and the number of deposited layers in the thin films are controlled by different parameters, like temperature and solution concentration. Material properties of CuPc deposited from TFA are studied in detail via x-ray diffraction, UV-Vis and FT-IR spectroscopy. Atomic force microscopy was used to study the morphology of the dried film.
The mechanism of the formation of CuPc nanoribbons from spin casted CuPc/TFA solution in ambient temperature is investigated and explained. The parameters (e.g. solution concentration profile) governing nucleation and growth are calculated based on the spin casting theory of a binary mixture of a nonvolatile solute and evaporative solvent. Based on this and intermolecular interactions between CuPc and substrate a nucleation and growth model is developed explaining the aggregation of CuPc in a supersaturated TFA solution.
Finally, a solution processed thin film of CuPc is applied as a donor layer in a functioning bilayer heterojunction OSC and the influence of the structure on OSC performance is studied.In den vergangenen Jahren wurden kosteneffiziente nasschemische Beschichtungsverfahren für die Herstellung organischer Dünnfilme für verschiedene opto-elektronische Anwendungen entdeckt und weiterentwickelt. Unter anderem wurden Phthalocyanin-Moleküle in photoaktiven Schichten für die Herstellung von Solarzellen intensiv erforscht. Aufgrund der kleinen bzw. unbekannten Löslichkeit wurden Phthalocyanin-Schichten durch Aufdampfverfahren im Vakuum hergestellt. Des Weiteren wurde die Löslichkeit durch chemische Synthese erhöht, was aber die Eigenschaften von Pc beeinträchtigte. In dieser Arbeit wurde die Löslichkeit, optische Absorption und Stabilität von 8 verschiedenen unsubstituierten Metall-Phthalocyaninen in 28 verschiedenen Lösungsmitteln quantitativ gemessen. Wegen ausreichender Löslichkeit, Stabilität und Anwendbarkeit in organischen Solarzellen wurde Kupferphthalocyanin (CuPc) in Trifluoressigsäure (TFA) für weitere Untersuchungen ausgewählt. Durch die Rotationsbeschichtung von CuPc aus TFA Lösung wurde ein dünner Film aus der verdampfenden Lösung auf dem Substrat platziert. Nach dem Verdampfen des Lösungsmittels, die Nanobändern aus CuPc bedecken das Substrat. Die Nanobänder haben eine Dicke von etwa ~ 1 nm (typische Dimension eines CuPc-Molekül) und variierender Breite und Länge, je nach Menge des Materials. Solche Nanobändern können durch Rotationsbeschichtung oder auch durch andere Nassbeschichtungsverfahren, wie Tauchbeschichtung, erzeugt werden. Ähnliche Fibrillen-Strukturen entstehen durch Nassbeschichtung von anderen Metall-Phthalocyaninen, wie Eisen- und Magnesium-Phthalocyanin, aus TFA-Lösung sowie auf anderen Substraten, wie Glas oder Indium Zinnoxid. Materialeigenschaften von aufgebrachten CuPc aus TFA Lösung und CuPc in der Lösung wurden ausführlich mit Röntgenbeugung, Spektroskopie- und Mikroskopie Methoden untersucht. Es wird gezeigt, dass die Nanobänder nicht in der Lösung, sondern durch Verdampfen des Lösungsmittels und der Übersättigung der Lösung entstehen. Die Rasterkraftmikroskopie wurde dazu verwendet, um die Morphologie des getrockneten Films bei unterschiedlicher Konzentration zu studieren. Der Mechanismus der Entstehung der Nanobändern wurde im Detail studiert. Gemäß der Keimbildung und Wachstumstheorie wurde die Entstehung der CuPc Nanobänder aus einer übersättigt Lösung diskutiert. Die Form der Nanobändern wurde unter Berücksichtigung der Wechselwirkung zwischen den Molekülen und dem Substrat diskutiert. Die nassverarbeitete CuPc-Dünnschicht wurde als Donorschicht in organischen Doppelschicht Solarzellen mit C60-Molekül, als Akzeptor eingesetzt. Die Effizienz der Energieumwandlung einer solchen Zelle wurde entsprechend den Schichtdicken der CuPc Schicht untersucht.
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Saulich, Sven. "Generic design and investigation of solar cooling systems". Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13627.
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This thesis presents work on a holistic approach for improving the overall design of solar cooling systems driven by solar thermal collectors. Newly developed methods for thermodynamic optimization of hydraulics and control were used to redesign an existing pilot plant. Measurements taken from the newly developed system show an 81% increase of the Solar Cooling Efficiency (SCEth) factor compared to the original pilot system. In addition to the improvements in system design, new efficiency factors for benchmarking solar cooling systems are presented. The Solar Supply Efficiency (SSEth) factor provides a means of quantifying the quality of solar thermal charging systems relative to the usable heat to drive the sorption process. The product of the SSEth with the already established COPth of the chiller, leads to the SCEth factor which, for the first time, provides a clear and concise benchmarking method for the overall design of solar cooling systems. Furthermore, the definition of a coefficient of performance, including irreversibilities from energy conversion (COPcon), enables a direct comparison of compression and sorption chiller technology. This new performance metric is applicable to all low-temperature heat-supply machines for direct comparison of different types or technologies. The achieved findings of this work led to an optimized generic design for solar cooling systems, which was successfully transferred to the market.
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Ribeiro, Enrique. "Composites Charbon-Actif/TiO2 pour des applications solaires Activated-Carbon/TiO2 composites preparation: An original grafting by milling approach for solar water treatment applications TiO2 grafted Activated Carbon elaboration by milling: composition effect on sorption and photocatalytic properties Experimental and theoretical coupled approaches for the analysis of radiative transfer in photoreactors containing particulate media : case study of TiO2 powders for photocatalytic reactions AC/TiO2 granular photocatalysts optical properties : material composition effect on the radiative transfer in a photoreactor". Thesis, Perpignan, 2020. http://www.theses.fr/2020PERP0016.
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L'utilisation de composites possédant une double fonctionnalité adsorption/photo-oxydation est une solution d'intérêt majeur pour traiter les polluants bio-récalcitrants contenus dans les eaux usées, par voie à partir d’énergie solaire. Cette étude propose la mise en œuvre de composites associant charbon actif (CA) et dioxyde de titane (TiO2) par une méthode originale de préparation, la mécanosynthèse. La faisabilité de la préparation de composites CA/TiO2 par mécanosynthèse a d'abord fait l'objet d'un travail d'investigation permettant sa validation. Cette première étape a permis de montrer la pertinence de la méthode pour l'élaboration de composites CA/TiO2 sous forme pulvérulente qui ont des propriétés structurales homogènes et maîtrisées et possèdent les propriétés fonctionnelles de photo-oxydation et de sorption recherchées. Dans un second temps, ces travaux montrent l'adaptabilité de la méthode pour la fabrication de composites CA/TiO2 de composition et donc de propriétés modulables en fonction de l'application de traitement de l'eau ciblée. Les propriétés radiatives de ces matériaux – qu'il est primordial de connaître pour envisager leur intégration au sein d'un photoréacteur – ont été déterminées par une approche théorique couplée à des mesures expérimentales. Il a ainsi pu être possible dans un dernier temps de modéliser et de simuler le transfert radiatif au sein d'un photoréacteur de géométrie simple contenant ces matériauxThe use of bifunctional adsorbent/photocatalyst composite is a solution of great interest for the solar removal of persistent pollutants from wastewaters. This work investigates the mechanosynthesis as an original approach for the preparation of Activated-Carbon/TiO2 composites . First, the feasibility of the preparation approach was validated. The method appeared relevant to produce homogeneous AC/TiO2 granular composites with controlled structural properties. The control of the preparation parameters led to both AC and TiO2 sorption and photo-oxidation functional properties preservation within the composite structure. Secondly, the preparation method ability in creating compositionally-varied AC/TiO2 composites, exhibiting different functional properties. This second part allowed us to show the adaptability of the AC/TiO2 preparation for a wide range of water treatment applications. The radiative properties of these materials - which are essential to know in order to consider their integration within a photoreactor - have been determined by a theoretical approach coupled with experimental measurements. It was thus possible to model and simulate the radiative transfer within a simple geometry photoreactor containing these materials
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Gondre, Damien. "Numerical modeling and analysis of heat and mass transfers in an adsorption heat storage tank : Influences of material properties, operating conditions and system design on storage performances". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI022/document.
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Le développement de solutions de stockage de l'énergie est un défi majeur pour permettre la transition énergétique d'un mix énergétique fortement carboné vers une part plus importante des énergies renouvelables. La nécessité de stocker de l'énergie vient de la dissociation, spatiale et temporelle, entre la source et la demande d'énergie. Stocker de l'énergie répond à deux besoins principaux : disposer d'énergie à l'endroit et au moment où on en a besoin. La consommation de chaleur à basse température (pour le chauffage des logements et des bureaux) représente une part importante de la consommation totale d'énergie (environ 35 % en France en 2010). Le développement de solutions de stockage de chaleur est donc d'une grande importance, d'autant plus avec la montée en puissance des énergies renouvelables. Parmi les technologies de stockage envisageables, le stockage par adsorption semble être le meilleur compromis en termes de densité de stockage et de maintient des performances sur plusieurs cycles de charge-décharge. Cette thèse se focalise donc sur le stockage de chaleur par adsorption, et traite de l'amélioration des performances du stockage et de l'intégration du système au bâtiment. L'approche développée pour répondre à ces questions est numérique. L'influence des propriétés thermophysiques de l'adsorbant et du fluide sur la densité de puissance d'une part, mais aussi sur la densité de stockage et l'autonomie du système, est étudiée. L'analyse des résultats permet de sélectionner les propriétés des matériaux les plus influentes et de mieux comprendre les transferts de chaleur et de masse au sein du réacteur. L'influence des conditions opératoires est aussi mise en avant. Enfin, il est montré que la capacité de stockage est linéairement dépendante du volume de matériau, tandis que la puissance dépend de la surface de section et que l'autonomie dépend de la longueur du lit d'adsorbant. Par ailleurs, le rapport entre l'énergie absorbée (charge) et relâchée (décharge) est d'environ 70 %. Mais pendant la phase de charge, environ 60 % de la chaleur entrant dans le réacteur n'est pas absorbée et est directement relâchée à la sortie. La conversion globale entre l'énergie récupérable et l'énergie fournie n'est donc que de 25 %. Cela montre qu'un système de stockage de chaleur par adsorption ne peut pas être pensé comme un système autonome mais doit être intégré aux autres systèmes de chauffage du bâtiment et aux lois de commande qui les régissent. Utiliser la ressource solaire pour le préchauffage du réacteur est une idée intéressante car elle améliore l’efficacité de la charge et permet une réutilisation de la part récupérée en sortie pour le chauffage direct du bâtiment. La part stockée sous forme sensible peut être récupérée plusieurs heures plus tard. Le système est ainsi transformé en un stockage combiné sensible/adsorption, avec une solution pour du stockage à long terme et pour du stockage à court termeThe development of energy storage solutions is a key challenge to enable the energy transition from fossil resources to renewable energies. The need to store energy actually comes from a dissociation between energy sources and energy demand. Storing energy meets two principal expectations: have energy available where and when it is required. Low temperature heat, for dwellings and offices heating, represents a high share of overall energy consumption (i.e. about 35 %). The development of heat storage solutions is then of great importance for energy management, especially in the context of the growing part of renewable energies. Adsorption heat storage appears to be the best trade off among available storage technologies in terms of heat storage density and performances over several cycles. Then, this PhD thesis focuses on adsorption heat storage and addresses the enhancement of storage performances and system integration. The approach developed to address these issues is numerical. Then, a model of an adsorption heat storage tank is developed, and validated using experimental data. The influence of material thermophysical properties on output power but also on storage density and system autonomy is investigated. This analysis enables a selection of particularly influencing material properties and a better understanding of heat and mass transfers. The influence of operating conditions is also underlined. It shows the importance of inlet humidity on both storage capacity and outlet power and the great influence of discharge flowrate on outlet power. Finally, it is shown heat storage capacity depends on the storage tank volume, while outlet power depends on cross section area and system autonomy on bed length. Besides, the conversion efficiency from absorbed energy (charge) to released energy (discharge) is 70 %. But during the charging process, about 60 % of incoming heat is not absorbed by the material and directly released. The overall conversion efficiency from energy provided to energy released is as low as 25 %. This demonstrates that an adsorption heat storage system cannot be thought of as a self-standing component but must be integrated into the building systems and control strategy. A clever use of heat losses for heating applications (in winter) or inlet fluid preheating (in summer) enhances global performances. Using available solar heat for system preheating is an interesting option since a part is instantly retrieved at the outlet of the storage tank and can be used for direct heating. Another part is stored as sensible heat and can be retrieved a few hours later. At least, it has the advantage of turning the adsorption storage tank into a combined sensible-adsorption storage tank that offers short-term and long-term storage solutions. Then, it may differ avoidable discharges of the sorption potential and increase the overall autonomy (or coverage fraction), in addition to optimizing chances of partial system recharge
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Rerhrhaye, Amal. "Contribution à l'étude de divers couples frigorigènes : Application à la réfrigération solaire photothermique". Nancy 1, 1986. http://www.theses.fr/1986NAN10093.
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Détermination du profil annuel de l'irradiation globale dans plusieurs sites de climat aride, en vue de la production de froid. Étude des propriétés physico-chimiques de trois couples frigorigènes : CACL::(2)-NH::(3), BACL::(2)-NH::(3), MGCL::(2)-NH::(3). Détermination du couple le plus adapté à la production de froid dans les zones tropicales. Présentation des résultats expérimentaux du fonctionnement d'un réfrigérateur solaire photothermique de capacité de 380 L installé à Madagascar
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Vieira, Herbert Melo. "Estudo experimental e teórico de um resfriador de água por adsorção usando energia solar". Universidade Federal da Paraíba, 2013. http://tede.biblioteca.ufpb.br:8080/handle/tede/5350.
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Previous issue date: 2013-03-25Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The respective thesis aims to develop a cooling system that uses an adsorptive chiller for cooling water and subsequent use of this cold water for air conditioning environment, theoretically and experimentally verifying the performance of adsorption refrigeration system, these devices have several advantages, among them, the use of clean energy such as solar. Brazil is a country with high rates of stroke, with an average capacity 16-20 MJ / year / h, so it becomes quite conducive to harnessing this energy, and to be contributing to the reduction of fossil fuel consumption and reduction of harmful gases to the environment. The proposed system consists of flat solar collectors, which are used to convert solar energy into thermal, being last transferred to a heat transfer fluid that circulates through the collector which is then stored in a boiler, or a thermal fluid, to be used whenever required for heating the bed adsorptive a chiller, which is composed of bed adsorptive the finned annular ducts involved with the adsorbent (silica gel). Many studies have been developed with the aim of increasing the performance of these systems, these studies have focused primarily on increasing the mass transfer and heat of adsorption beds and using systems which run continuously through the use of two adsorption beds which work in different phases. Experimental studies in porous beds featuring different configurations were performed, observing thus which present higher rates adsorbent, and subsequently applied this setting in the construction of the porous bed adsorptive chiller. A computational model was developed theoretically allowing you to check your system's performance.
O respectivo trabalho de tese visa desenvolver um sistema de refrigeração que utiliza um chiller adsortivo para resfriamento de água e posterior uso desta água fria para climatização de ambiente, verificando teoricamente e experimentalmente o desempenho do sistema de refrigeração por adsorção, estes dispositivos apresentam várias vantagens, entre elas, o uso de energia limpa, como a solar. O Brasil é um país que apresenta grande índice de insolação, com uma capacidade média de 16 a 20 MJ/ano/h, desta forma torna-se bastante propício o aproveitamento desta energia, além de estar contribuindo para a redução do consumo de combustíveis fósseis e redução de gases nocivos ao meio-ambiente. O sistema proposto é composto por coletores solares planos, que são usados para converter a energia solar em térmica, sendo está última transferida para um fluido térmico que circula pelo coletor que posteriormente é armazenado em um boiler, podendo este fluido térmico, ser usado sempre que necessário para o aquecimento do leito adsortivo de um chiller, sendo este leito adsortivo composto por dutos aletados na forma anular envolvidos com o adsorvente (sílica gel). Muitos trabalhos vem sendo desenvolvidos com o intuito de aumentar o desempenho destes sistemas, estes estudos estão concentrados basicamente no aumento da transferência de massa e calor dos leitos adsortivos e utilização de sistemas que funcione continuamente através do uso de dois leitos adsortivos que trabalham em fases diferentes. Ensaios experimentais com leitos porosos apresentando configurações diferentes foram realizados, observando deste modo, qual apresentaria maiores taxas adsortivas, sendo posteriormente aplicada esta configuração na construção do leito poroso do chiller adsortivo. Um modelo computacional foi desenvolvido permitindo verificar teoricamente o desempenho do sistema.
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Ranwaha, Tshifhiwa Steven. "Density functional theory study of adsorption of cronconate dyes on TiO2 Anatase (010) and (100) surfaces". 2018. http://hdl.handle.net/11602/1359.
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MSc (Physics)Department of Physics
Currently the dye sensitized solar cells have attracted more attention due to their low cost, transparency and flexibility. These types of solar cells use the dye molecule adsorbed on TiO2 semiconductor in Nano architecture with the role of absorbing photons, in recent research attempts are being made to shifts the absorption spectral of TiO2 to visible and near infrared–region of solar spectrum to achieve maximum photo absorption which yields to an increase in the efficiency of the dye sensitized solar cells. In the current study, density functional theory (DFT) was used to model two croconate dyes (CR1 and CR2), one with an electron donating methyl group (CR1) and the other with an electron –withdrawing caboxyl group (CR2). The geometric, electronic and optical properties of these dyes were compared. The adsorption behaviour of the two dyes on (010 and 100) anatase TiO2 surfaces were investigated in this study by employing first principle calculation based on DFT using a plane-wave pseudo potential method. The generalized gradient approximation (GGA) was used in the scheme of Perdew-Burke Ernzerhof to describe the exchange -correlation function as implemented in the CASTEP package in Material Studio of BIOVIA. The adsorption results shows a spontaneous electron injection followed by efficient regeneration of the oxidized dye molecules by the electrolyte and strong binding ability of CR2 to the TiO2 surface, but also shows a comparable binding strength of CR1. The results of this study will help in the design of high efficient dye for DSSCs.
NRF
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Wang, Ji. "Study on Accumulated Performance of a Solar Thermal Powered Adsorption Refrigeration System". Thesis, 2019. http://hdl.handle.net/2440/120966.
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The thesis presents the outcomes of a study on the accumulated performance of a solar thermal powered adsorption refrigeration system. The solar-powered solid adsorption refrigeration system has numerous advantages including no moving parts during operation, using solar energy as the only heat input to run the whole system and being environmentally benign. The methanol and activated carbon selected as a working pair are due to advantages of their ice-making capacity, high efficiency and low price. The system, in its simplest form, runs according to the intermittent daily solar cycle, only making cooling at night and not during the daytime. The previous research mainly focuses on the individual daily cycle under the assumption that the system restores back to its original point every day, regardless of a real climate condition. In reality, for such a refrigeration system, its real performance depends not only on the current day’s weather condition but also on the previous day’s situation. However, the accumulated performance of the system over a period has only been little studied, which brings out three research questions that remain to be answered: How should a new configuration be modified, in order to make the system accumulate cooling capacity without removing ice daily? How many situations should be involved in the new accumulated cycles with consideration of real daily and hourly climate conditions? How should the mathematical models be established, in order to simulate the accumulated performance of the system more realistic and accurately? Therefore, the aim of the research is to develop a better understanding of an accumulated performance of an activated carbon/methanol refrigeration system if running over a period, e.g. days or weeks, by developing two validated simulation models. The thesis complies with the graduation by publication format of the University of Adelaide, which consists of one published journal article and one submitted journal article which is currently under review. The two articles are able to demonstrate the outcomes of the study and also form the main part of the thesis. Additional introduction and a literature review are provided to establish the context and significance of this work. The main outcomes of the study include: The new configuration of such a system, which can accumulate the cooling capacity without removing ice daily, has been established. In the configuration, the receiver and evaporator must be separated by adding separation valves between them. Possible cycles of such a system have been identified with consideration of realistic daily climate conditions. The mathematical model using daily weather data, with consideration of possible leftover liquid in the receiver, has been developed. The model has been validated against the published experimental data with an acceptable agreement. A desktop case-study for 50 consecutive days has been used to demonstrate the difference in the simulation of accumulated performance by two models, i.e. the model using daily climate conditions and the model under ideal assumptions. It has been concluded that the developed model using daily climate conditions is more accurate than the model under the ideal assumptions. The second mathematical model using hourly weather data has been developed based on seven possible cycles. These cycles, which are involved in the initial heating process and condensing process during the daytime, have been identified. The mathematical model using hourly climate conditions has been validated against the published experimental data with a more accurate agreement, compared to that of the model using daily climate conditions. A desktop case-study for three climatic days has been conducted to demonstrate the difference in the simulation of performance when the model using daily climate conditions and hourly climate conditions respectively. The daily performance (i.e. daily-evaporated methanol liquid) simulated from the new model could be 31.3% more than that from the first mathematical model in a special climatic day.Thesis (MPhil) -- University of Adelaide, School of Mechanical Engineering, 2019
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"Research and Development of a Small - Scale Adsorption Cooling System". Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.14333.
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abstract: The world is grappling with two serious issues related to energy and climate change. The use of solar energy is receiving much attention due to its potential as one of the solutions. Air conditioning is particularly attractive as a solar energy application because of the near coincidence of peak cooling loads with the available solar power. Recently, researchers have started serious discussions of using adsorptive processes for refrigeration and heat pumps. There is some success for the >100 ton adsorption systems but none exists in the <10 ton size range required for residential air conditioning. There are myriad reasons for the lack of small-scale systems such as low Coefficient of Performance (COP), high capital cost, scalability, and limited performance data. A numerical model to simulate an adsorption system was developed and its performance was compared with similar thermal-powered systems. Results showed that both the adsorption and absorption systems provide equal cooling capacity for a driving temperature range of 70-120 ºC, but the adsorption system is the only system to deliver cooling at temperatures below 65 ºC. Additionally, the absorption and desiccant systems provide better COP at low temperatures, but the COP's of the three systems converge at higher regeneration temperatures. To further investigate the viability of solar-powered heat pump systems, an hourly building load simulation was developed for a single-family house in the Phoenix metropolitan area. Thermal as well as economic performance comparison was conducted for adsorption, absorption, and solar photovoltaic (PV) powered vapor compression systems for a range of solar collector area and storage capacity. The results showed that for a small collector area, solar PV is more cost-effective whereas adsorption is better than absorption for larger collector area. The optimum solar collector area and the storage size were determined for each type of solar system. As part of this dissertation work, a small-scale proof-of-concept prototype of the adsorption system was assembled using some novel heat transfer enhancement strategies. Activated carbon and butane was chosen as the adsorbent-refrigerant pair. It was found that a COP of 0.12 and a cooling capacity of 89.6 W can be achieved.Dissertation/Thesis
Ph.D. Mechanical Engineering 2011