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1
Omer, Siddig Adam. "Solar thermoelectric system for small scale power generation." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/7440.
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This thesis is concerned with the design and evaluation of a small scale solarthermoelectric power generation system. The system is intended for electricity generation and thermal energy supply to small scale applications in developing countries of the sunny equatorial regions. Detailed design methodologies and evaluations of both the thermoelectric device and the solar energy collector, which are parts of the combined system, are presented. In addition to experimental evaluations, three theoretical models are presented which allow the design and evaluation of both the thermoelectric module and the solar energy collector. One of the models (a unified thermoelectric device model) concerns the geometrical optimization and performance prediction of a thermoelectric module in power generation mode. The model is unified in the sense that it accounts for the effect of all the parameters that contribute to the performance of the thermoelectric module, a number of which are ignored by the available design models. The unified model is used for a comparative evaluation of five thermoelectric modules. One of these is commercially available and the others are assumed to have optimum geometry but with different design parameters (thermal and electrical contact layer properties). The model has been validated using data from an experimental investigation undertaken to evaluate the commercial thermoelectric module in power generation mode. Results showed that though the commercially available thermoelectric cooling devices can be used for electricity generation, it is appropriate to have modules optimized specifically for power generation, and to improve the contact layers of thermoelement accordingly. Attempts have also been made to produce and evaluate thermoelectric materials using a simple melt-qucnching technique which produces materials with properties similar to those of the more expensive crystalline materials.
2
Sharma, Chandan. "Techno-economics of solar thermal power generation in india." Thesis, IIT Delhi, 2016. http://localhost:8080/xmlui/handle/12345678/6985.
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Kamanzi, Janvier. "Thermal electric solar power conversion panel development." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2527.
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Thesis (DTech (Engineering))--Cape Peninsula University of Technology, 2017.The world has been experiencing energy-related problems following pressuring energy demands which go along with the global economy growth. These problems can be phrased in three paradoxical statements: Firstly, in spite of a massive and costless solar energy, global unprecedented energy crisis has prevailed, resulting in skyrocketing costs. Secondly, though the sun releases a clean energy, yet conventional plants are mainly being run on unclean energy sources despite their part in the climate changes and global warming. Thirdly, while a negligible percentage of the solar energy is used for power generation purposes, it is not optimally exploited since more than its half is wasted in the form of heat which contributes to lowering efficiency of solar cells and causes their premature degradation and anticipated ageing. The research is geared at addressing the issue related to unsatisfactory efficiencies and anticipated ageing of solar modules. The methodology adopted to achieve the research aim consisted of a literature survey which in turn inspired the devising of a high-efficiency novel thermal electric solar power panel. Through an in-depth overview, the literature survey outlined the rationale of the research interest, factors affecting the performance of PVs as well as existing strategies towards addressing spotted shortcomings. While photovoltaic (PV) panels could be identified as the most reliable platform for sunlight-to-electricity conversion, they exhibit a shortcoming in terms of following the sun so as to maximize exposure to sunlight which negatively affects PVs’ efficiencies in one hand. On the other hand, the inability of solar cells to reflect the unusable heat energy present in the sunlight poses as a lifespan threat. Strategies and techniques in place to track the sun and keep PVs in nominal operational temperatures were therefore reviewed.
4
Pierce, Warrick Tait. "Solar assisted power generation (SAPG) : investigation of solar preheating of feedwater." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80139.
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Thesis (MEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Solar Assisted Power Generation (SAPG) can be seen as a synergy of solar and fossil plants – combining the environmental benefits of the former and the scale, efficiency and reliability of the latter. SAPG offers great potential for cost effective utilization of solar energy on utility scale and could accelerate the adoption of solar thermal energy technologies in the short and medium term, especially in countries with a significant coal base and a good solar resource such as Australia, China, United States, India and South Africa. SAPG is the replacement of bled-off steam in a Regenerative Rankine power cycle. Power plant simulations were performed using weather data for Lephalale, South Africa (Matimba power station). With an increase in the solar field outlet temperature, an increase in overall solar to electric efficiency was observed, superior to a stand-alone Solar Thermal Power Plant(s) (STPP) at similar temperatures. The performance of four solar collector technologies was compared: flat plate, evacuated tube, Linear Fresnel (LF) and Parabolic Trough (PT). This comparison was limited to the normal incidence angles of irradiation. For this application, nonconcentrating technologies are not competitive. For non-normal incidence angles, annual simulations were limited to PT and LF at final feedwater heater temperatures. The actual aperture area of around 80 000 m2 was used (50 MW thermal based on LF). On an equal aperture area basis, PT outperforms LF significantly. For the conventional North-South arrangement, LF needs to be around 53% of the specific installation cost (in $/m2 aperture area) of PT to be cost competitive. A SAPG plant at Lephalale was compared to a stand-alone Solar Thermal Power Plant STPP in a good solar resource area, namely Upington, South Africa – Parabolic Trough solar collector fields of equal size were considered for both configurations. It was found that the annual electricity generated with a SAPG plant is more than 25% greater than a stand-alone STPP. If the cost of SAPG is taken as 72% of the cost of a stand-alone STPP, this translates into SAPG being 1.8 times more cost effective than stand-alone STPP. Furthermore, SAPG performs better in high electricity demand months (South African winter – May to August). Stand-alone STPP have been adopted in South Africa and are currently being built. This was achieved by the government creating an attractive environment for Independent Power Producers (IPP). Eskom, the national power supplier, is currently investigating solar boosting at existing Eskom sites. This report argues that on a national level, SAPG, specifically solar preheating of feedwater, is a more viable solution for South Africa, with both its significant coal base and good solar resource.
AFRIKAANSE OPSOMMING: Son ondersteunde krag generasie (SOKG) kan gesien word as sinergie van sonkrag en fossiele brandstof aanlegte – dit voeg die omgewings voordele van die eersgenoemde en die grote, effektiwiteit en betroubaarheid van die laasgenoemde by mekaar. SOKG opper groot potensiaal vir koste effektiewe gebruik van son energie op nutsmaatskappyskaal en kan die aanvaarding van sontermiese energietegnologieë in die kort en medium termyn versnel, veral in lande met beduidende kool reserwes en goeie sonkrag voorkoms soos Australië, China, Verenigde State van Amerika, Indië en Suid-Afrika. SOKG impliseer die vervanging van aftap stoom in die regeneratiewe Rankine krag kringloop. Kragstasie simulasies was gedoen met die gebruik van weer data van Lephalale, Suid-Afrika (Matimba kragstasie). Met die toename van die sonveld uitlaat temperatuur kon oorhoofse son-na-elektrisiteit effektiwiteit vasgestel word, wat hoër is as die van alleenstaande sontermiese krag stasie (STKS) by soortgelyke temperature. Die effektiwiteit van vier son kollekteerder tegnologieë was vergelyk: plat plaat, vakuum buis, lineêre Fresnel (LF) en paraboliese trog (PT). Die vergelyking was beperk tot normale inval van bestraling. Vir hierdie toepassing is nie-konsentreerende tegnologie nie mededingend nie. Vir nie-normale inval hoeke was jaarlange simulasies beperk tot PT en LF by finale voedingswater temperatuur. Die werklike opening area van omtrent 80 000 m2 was gebruik (50 MW termies gebaseer op LF). By gelyke opening area, uitpresteer PT LF beduidend. Vir die gebruiklike Noord-Suid rankskikking benodig LF omtrent 53% van die spesifieke installasie kostes (in $/m2 opening area) van PT om kostes mededingend te kan wees. ‘n SOKG aanleg by Lephalale was vergelyk met alleenstaande STKS in die goeie son voorkoms gebied van Upington, Suid-Afrika – Paraboliese trog kollekteerder velde van gelyke grote was oorweeg vir al twee konfigurasies. Dit was gevind dat die jaarlikse elektrisiteit gegenereer vanaf SOKG meer as 25% is as die van alleenstaande STKS. Indien SOKG oorweeg word met 72% van die kostes van alleenstaande STKS, dan beteken dit dat SOKG 1.8 keer meer koste effektief is as alleenstade STKS. Verder, SOKG presteer beter in die hoer elektrisiteitsnavraag maande (Suid- Afrikaanse winter – May tot Augustus). Alleenstaande STKS is gekies vir Suid-Afrika en word tans gebou. Dit is bereik deur dat die regering ‘n aantreklike omgewing geskep het vir onafhanglike krag produsente. Eskom ondersoek tans SOKG by bestaande Eskom persele. Hierdie verslag beweer dat op nasionale/Eskom vlak, SOKG, besonders son voorverhitting van voedingswater, meer haalbare oplossing is vir Suid-Afrika met sy beduidende koolreserwes en goeie son voorkoms.
5
Desai, Ranjit. "Thermo-Economic Analysis of a Solar Thermal Power Plant with a Central Tower Receiver for Direct Steam Generation." Thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-131764.
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Sun, Amy (Amy Teh-Yu). "Field fabrication of solar-thermal powered stream turbines for generation of mechanical power." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37400.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2006.Includes bibliographical references (p. 65).
Providing adequate energy to developing countries is one of the greatest global technical challenges today. Fabrication is undergoing a revolution that parallels the digitization of computation and communications. Emerging affordable, "desktop" fabrication tools are providing the precision and repeatability necessary for regular people to design, manufacture, and install a system to convert solar thermal energy to useful work. In the spectrum of devices that use solar energy, this field-fabricated system exists in a space between crude solar cookers for heating food and complex, expensive photovoltaic cells. Computer control and high precision allows regular people to experimentally converge on a locally-appropriate design and implementation to solve the challenge of providing energy. This thesis describes a field producible, small-scale turbine that uses solar thermal energy to provide mechanical energy. I investigate a solar thermal steam-driven turbine system and build and evaluate several versions in field fabrication lab locations around the world. I consider the efficacy of deployment in rural developing areas.
by Amy Sun.
S.M.
7
Assembe, Cedric Obiang. "Integrated solar photovoltaic and thermal system for enhanced energy efficiency." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2387.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016.South Africa has raised concerns regarding the development of renewable energy sources such as wind, hydro and solar energy. Integration of a combined photovoltaic and thermal system was considered to transform simultaneous energy into electricity and heat. This was done to challenge the low energy efficiency observed when the two solar energy conversion technologies are employed separately, in order to gain higher overall energy efficiency and ensure better utilization of the solar energy. Therefore, the notion of using a combined photovoltaic and thermal system was to optimize and to improve the overall PV panel efficiency by adding conversion to thermal energy for residential and commercial needs of hot water or space heating or space cooling using appropriate technology. The PV/T model constructed using water as fluid like the one used for the experimental work, presented a marginal increase in electrical efficiency but a considerable yield on the overall PV/T efficiency, because of the simultaneous operation by coupling a PV module with a thermal collectors.
8
Muhammad, Mubarak Danladi. "Development of a cascaded latent heat storage system for parabolic trough solar thermal power generation." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9303.
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Concentrated solar power (CSP) has the potential of fulfilling the world’s
electricity needs. Parabolic-trough system using synthetic oil as the HTF with
operating temperature between 300 and 400o C, is the most matured CSP
technology. A thermal storage system is required for the stable and cost
effective operation of CSP plants. The current storage technology is the indirect
two-tank system which is expensive and has high energy consumption due to
the need to prevent the storage material from freezing. Latent heat storage
(LHS) systems offer higher storage density translating into smaller storage size
and higher performance but suitable phase change materials (PCMs) have low
thermal conductivity, thus hindering the realization of their potential. The low
thermal conductivity can be solved by heat transfer enhancement in the PCM.
There is also lack of suitable commercially-available PCMs to cover the
operating temperature range. In this study, a hybrid cascaded storage system
(HCSS) consisting of a cascaded finned LHS and a high temperature sensible
or concrete tube register (CTR) stages was proposed and analysed via
modelling and simulation. Fluent CFD code and the Dymola simulation
environment were employed.
A validated CFD phase change model was used in determining the heat
transfer characteristics during charging and discharging of a finned and unfinned
LHS shell-and-tube storage element. The effects of various fin
configurations were investigated and heat transfer coefficients that can be used
for predicting the performance of the system were obtained. A model of the
HCSS was then developed in the Dymola simulation environment. Simulations
were conducted considering the required boundary conditions of the system to
develop the best design of a system having a capacity of 875 MWhth, equivalent
to 6 hours of full load operation of a 50 MWe power plant.
The cascaded finned LHS section provided ~46% of the entire HCSS capacity.
The HCSS and cascaded finned LHS section have volumetric specific
capacities 9.3% and 54% greater than that of the two-tank system, respectively.
It has been estimated that the capital cost of the system is ~12% greater than
that of the two-tank system. Considering that the passive HCSS has lower
operational and maintenance costs it will be more cost effective than the twotank
system considering the life cycle of the system. There is no requirement of
keeping the storage material above its melting temperature always. The HCSS
has also the potential of even lower capital cost at higher capacities (>6 hours
of full load operation).
9
Kumbasar, Serdar. "Techno-Economic Assessment of Solar PV/Thermal System for Power and Cooling Generation in Antalya, Turkey." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119608.
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In this study a roof-top PVT/absorption chiller system is modeled for a hotel building in Antalya, Turkey to cover the cooling demand of the hotel, to produce electricity and domestic hot water. PVT modules, an absorption chiller, a hot storage tank and a natural gas fired auxiliary heater are the main components of the system. Elecetrical power produced by the system is 94.2 MWh, the cooling power is 185.5 MWh and the amount of domestic hot water produced in the system is 65135 m3 at 45 0C annually. Even though the systems is capable of meeting the demands of the hotel building, because of the high investment costs of PVT modules and high interest rates in Turkey, it is not economically favorable. Using cheaper solar collectors, integrating a cold storage unit in the system or having an improved conrol strategy are the options to increase the system efficiency and to make the system economically competitive.
10
Howard, Dustin F. "Modeling, simulation, and analysis of grid connected dish-stirling solar power plants." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34832.
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The percentage of renewable energy within the global electric power generation portfolio is expected to increase rapidly over the next few decades due to increasing concerns about climate change, fossil fuel costs, and energy security. Solar thermal energy, also known as concentrating solar power (CSP), is emerging as an important solution to new demands for clean, renewable electricity generation. Dish-Stirling (DS) technology, a form of CSP, is a relatively new player in the renewable energy market, although research in the technology has been ongoing now for nearly thirty years. The first large plant utilizing DS technology, rated at 1.5 MW, came online in January 2010 in Peoria, AZ, and plants rated for several hundred MW are in the planning stages. Increasing capacity of this technology within the utility grid requires extensive dynamic simulation studies to ensure that the power system maintains its safety and reliability in spite of the technological challenges that DS technology presents, particularly related to the intermittency of the energy source and its use of a non-conventional asynchronous generator. The research presented in this thesis attempts to fill in the gaps between the well established research on Stirling engines in the world of thermodynamics and the use of DS systems in electric power system applications, a topic which has received scant attention in publications since the emergence of this technology.
DS technology uses a paraboloidal shaped dish of mirrors to concentrate sunlight to a single point. The high temperatures achieved at the focal point of the mirrors is used as a heat source for the Stirling engine, which is a closed-cycle, external heat engine. Invented by the Scottish clergyman Robert Stirling in 1816, the Stirling engine is capable of high efficiency and releases no emissions, making it highly compatible with concentrated solar energy. The Stirling engine turns a squirrel-cage induction generator, where electricity is delivered through underground cables from thousands of independent, autonomous 10-25 kW rated DS units in a large solar farm.
A dynamic model of the DS system is presented in this thesis, including models of the Stirling engine working gas and mechanical dynamics. Custom FORTRAN code is written to model the Stirling engine dynamics within PSCAD/EMTDC. The Stirling engine and various other components of the DS system are incorporated into an electrical network, including first a single-machine, infinite bus network, and then a larger 12-bus network including conventional generators, loads, and transmission lines. An analysis of the DS control systems is presented, and simulation results are provided to demonstrate the system's steady state and dynamic behavior within these electric power networks. Potential grid interconnection requirements are discussed, including issues with power factor correction and low voltage ride-through, and simulation results are provided to illustrate the dish-Stirling system's capability for meeting such requirements.
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Bachelier, Camille [Verfasser], and R. [Akademischer Betreuer] Stieglitz. "Techno-economical analyses of linear solar thermal electric plants for dispatchable power generation / Camille Bachelier ; Betreuer: R. Stieglitz." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1238148115/34.
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Kulkarni, Sachin Shashidhar. "Effect of composition, morphology and semiconducting properties on the efficiency of CuIn₁₋x̳Gax̳Se₂₋y̳Sy̳ thin-film solar cells prepared by rapid thermal processing." Orlando, Fla. : University of Central Florida, 2008. http://purl.fcla.edu/fcla/etd/CFE0002467.
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Ellakany, Farid. "Enhancing the Thermo-Economic Performance of a Direct Steam Generation Solar Tower Power Plant through the Implementation of Steam Flow Control Strategies for Flexible Operation." Thesis, KTH, Kraft- och värmeteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150112.
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Above 90% of the current installed concentrating solar power plants are based on conventional steam-turbine cycles. The operation of steam turbines in these plants is distinctive when compared to traditional base-load power plants. The reason goes back to the intermittent nature of solar power which, in the absence of thermal energy storage or a back-up combustion boiler, forces plant operators to shut down the turbines during night time or at times of low solar radiation. Furthermore, such intermittency often leads to undesirable off-design turbine operating circumstances, either by load variations or changes on live-steam conditions.The present study examines the influence of implementing two operating strategies dealing with steam flow control as a function of incoming solar power for enhancing the thermo-economic performance of a direct steam generation solar tower power plant. The first one consists of a simultaneous high pressure turbine stage- and feed-water preheater bypass. This strategy is used during periods in which the solar radiation is higher than nominal. On these occasions, the plant is capable of generating a larger flow of steam, which allows for an increase in the power production when inserting the additional steam in the turbine bypass. On the other hand, the second operating strategy consists of using an additional feed-water preheater when the power from the field is lower than nominal. In this way, the feed water can reach a higher temperature prior entering the boiler, which is not only beneficial during times of cloud-passages, but also during the start-up process.A dynamic model of a direct steam generation solar tower power plant has been developed following design and operation specifications of an existing reference plant. The two proposed strategies were implemented to the reference model, then a whole year worth simulation was performed for both the reference and the modified models. Lastly, the thermodynamic and economic performance of both systems was measured for the purpose of comparison, by means of using KTH in-house tool DYESOPT. Results show that the implementation of the proposed strategies can enhance the economic viability of the systems by yielding a reduction of 8.7% on the levelized cost of electricity, mainly due to allowing achieving a 12% increase in the net electricity production.
14
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.
15
Sheu, Elysia J. (Elysia Ja-Zeng). "Hybrid solar-fossil fuel power generation." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78189.
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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. 83-92).
In this thesis, a literature review of hybrid solar-fossil fuel power generation is first given with an emphasis on system integration and evaluation. Hybrid systems are defined as those which use solar energy and fuel simultaneously, thus excluding the viable alternative of solar thermal plants which use fossil fuels as backup. The review is divided into three main sections: performance metrics, the different concentrated solar receiver technologies and their operating conditions, and the different hybridization schemes. In addition, a new linear combination metric for analysis of hybrid systems, which considers trade-off of different metrics at the fleet level, is presented. This metric is also compared to alternative metrics from multi-objective optimization. Some previous work only evaluates the hybrid cycle at a certain point in time, which can be misleading as this evaluation would not take into account certain aspects of hybrid cycle such as fluctuating solar supply. Furthermore, almost all previous work designs the hybrid solar-fossil fuel systems for a certain point in time and then evaluates the performance of the system for an entire year. By not taking into account fluctuating solar supply and selling price of electricity in the design of the system, the best possible annual performance of the hybrid cycle may not be reached. Second, an analysis of solar reforming as the integration method for the hybrid cycle is presented, in particular steam reforming of methane. Two solar reforming systems are analyzed: one with a parabolic trough and the other with a solar tower. From the analysis, it is determined that parabolic troughs are not suitable for steam reforming due to the relatively low operating temperatures. The tower reformer system is integrated with a standard combined cycle, and the design and operation of the hybrid cycle is optimized for highest work output for a fixed fuel input and solar collector area (essentially optimizing for maximum cycle efficiency). A heuristic two step procedure is used for the optimization due to the limitation of the optimizer which cannot simultaneously optimize both design and operation. From the optimization, it is determined that the tower reforming integration method is a promising integration option in that this type of hybrid cycle yields high incremental solar efficiencies and also satisfies the linear combination metric for efficiency and CO₂ emissions (i.e., the analyzed hybrid cycle has a higher efficiency for a fixed CO₂ emissions compared to a linear combination of solar only and fossil fuel only cycles).
by Elysia J. Sheu.
S.M.
16
Obadal, Petr. "Různé způsoby využití slunečního záření pro výrobu elektrické energie." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219072.
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The thesis deals with the problem of potential use of solar energy through the conversion into electric energy. The thesis analyses in great detail several types of conversion. My special concern included photovoltaic conversion and thermal conversion of solar energy using steam turbines for energy production. In the subsequent parts, I focus on the problem of photovoltaic, photovoltaic systems, and solar thermal power plants, their installation and use.
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Aldali, Yasser. "Solar thermal and photovoltaic electrical generation in Libya." Thesis, Edinburgh Napier University, 2012. http://researchrepository.napier.ac.uk/Output/5272.
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This thesis investigates the application of large scale concentrated solar (CSP) and photovoltaic power plants in Libya. Direct Steam Generation (DSG) offers a cheaper and less risky method of generating electricity using concentrated solar energy than Heat Transfer Fluid (HTF) plant. However, it is argued that the location of a DSG plant can be critical in realising these benefits, and that the South-East part of Libya is ideal in this respect. The models and calculations presented here are the result of an implementation of the 2007 revision of the IAPWS equations in a general application based on Microsoft Excel and VBA. The hypothetical design for 50MW DSG power plant discussed in this thesis is shown to yield an 76% reduction in greenhouse gas emissions compared to an equivalent gas-only plant over the ten-hour daily period of operation. Land requirement is modest at 0.7km2. A new method for improving the distribution of heat within the absorber tube wall was developed. Internal helical fins within the absorber tube have been proposed to provide a regularly pitched and orderly distribution of flow from the ‘hot' to the ‘cold' side of the absorber tube. Note that the irradiance profile on the absorber tube is highly asymmetric. A CFD simulation using FLUENT software was carried out for three types of pipes with different internal helical-fin pitch, and an aluminium pipe without fins. The results show that the thermal gradient between the upper and lower temperature for the pipe without a helical fin is considerably higher compared with the pipes with helical fins. Also, the thermal gradient between the two halves for the aluminium pipe (without a helical fin) is much lower when compared to the result for the traditional steel pipe (without a helical fin). A 50MW PV-grid connected (stationary and tracking) power plant design in Al-Kufra, Libya has been carried out presently. A hetero-junction with intrinsic thin layer (HIT) type PV module has been selected and modelled. The effectiveness of the use of a cooling jacket on the modules has been evaluated. A Microsoft Excel-VBA program has been constructed to compute slope radiation, dew-point, sky temperature, and then cell temperature, maximum power output and module efficiency for this system, with and without water cooling for stationary system and for tracking system without water cooling. The results for energy production show that the total energy output is 114GWh/year without a water cooling system, 119GWh/year with a water cooling system for stationary system and 148GWh/year for tracking system. The average module efficiency with and without a cooling system for the stationary system is 17.2% and 16.6% respectively and 16.2% for the tracking system. The electricity generation capacity factor (CF) and solar capacity factor (SCF) for stationary system were found to be 26% and 62.5% respectively and 34% and 82% for tracking system. The payback time for the proposed LS-PV power plant was found to be 2.75 years for the stationary system and 3.58 years for the tracking system. The modelling that was carried was based on the measurements conducted on the experimental system set in a city in the southern part of Turkey. Those measurements are recorded by a Turkish team at Iskanderun. As well as the current, voltage and cell temperature of the photovoltaic module, the environmental variables such as ambient temperature and solar irradiance were measured. These data were used for validation purposes. The correlation for the conversion of solar irradiation from horizontal to sloped surface indicated that the presently used model is highly successful reflected by the goodness of fit parameters: the coefficient of determination is 0.97, and the mean bias error -2.2W/m2. Similarly, the cell temperature model used in the present thesis is validated by the following correlation parameters R2 = 0.97 oC, while MBE is 0.7 and RMSE = 2.1 oC.
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Cottam, P. J. "Innovation in solar thermal chimney power plants." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10045417/.
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This thesis analyses novel technology for renewable electricity generation: the solar thermal chimney (STC) power plant and the suspended chimney (SC) as a plant component. The STC consists of a solar collector, a tall chimney located at the centre of the collector, and turbines and generators at the base of the chimney. Air heated in the collector rises up the chimney under buoyancy and generates power in the turbines. STCs have the potential to generate large amounts of power, but research is required to improve their economic viability. A state-of-the-art STC model was developed, focussing on accurate simulation of collector thermodynamics, and providing data on flow characteristics and plant performance. It was used to explore power generation for matched component dimensions, where for given chimney heights, a range of chimney and collector radii were investigated. Matched dimensions are driven by the collector thermal components approaching thermal equilibrium. This analysis was complemented with a simple cost model to identify the most cost-effective STC configurations. The collector canopy is an exceptionally large structure. Many of the designs proposed in the literature are either complex to manufacture or limit performance. This thesis presents and analyses a series of novel canopy profiles which are easier to manufacture and can be incorporated with little loss in performance. STC chimneys are exceptionally tall slender structures and supporting their self-weight is difficult. This thesis proposes to re-design the chimney as a fabric structure, held aloft with lighter-than-air gas. The performance of initial, small scale suspended chimney prototypes under lateral loading was investigated experimentally to assess the response to wind loads. A novel method of stiffening is proposed and design of larger prototypes developed. The economic viability of a commercial-scale suspended chimney was investigated, yielding cost reductions compared to conventional chimney designs.
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Trolove, Hamish P. "Line focus solar Stirling domestic power generation." Thesis, University of Canterbury. Mechanical Engineering, 1994. http://hdl.handle.net/10092/6468.
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This thesis has found that to generate electricity for a domestic supply, the use of a two stage line focus concentrator coupled to a Stirling engine by way of a heat pipe is very inefficient, and the end result (useful power) could be better achieved by a line focus system with a Rankine cycle heat engine, or by using photovoltaic cells. For larger systems such as that needed to supply a small community, a point focus solar Stirling engine is the most efficient system at this stage, but with the rapid improvements being made in the performance of photovoltaic cells, this may not be the case in the future.
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Amatya, Reja. "Solar thermoelectrics for small scale power generation." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70784.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 243-253).
In the past two decades, there has been a surge in the research of new thermoelectric (TE) materials, driven party by the need for clean and sustainable power generation technology. Utilizing the Seebeck effect, the thermoelectric devices can be used as heat engines to convert heat into electricity. With no moving parts, the generators are considered highly reliable with low maintenance, which is essential for decentralized power source. With nearly 1.6 billion people living without basic electricity, the need for a small scale power generation is there. Through this work, we show that the solar thermoelectric generators (STEGs) using cheap parabolic concentrators with high ZT modules can be a viable and a costeffective alternative to solar photovoltaics for distributed power generation. The maximum conversion efficiency of 3% has been achieved for a STEG under AM 1.5G conditions with commodity thermoelectric module. The generator was able to produce a peak output power of 11 W, with an inexpensive parabolic solar concentrator which can be found in developing countries being used as solar cookers. The output power is the highest achieved value for concentrated solar thermoelectrics and it is comparable to photovoltaic modules that are deployed in these rural communities. Based on a heat transfer model developed during this work, various system parameters were analyzed for maximizing the performance. An optimized thermoelectric module design with a slight aspect ratio variation for the TE legs have been identified that can increase the efficiency by 28%. Another parameter for system improvement that has been considered is the use of novel TE material. Issues of earth-abundance, material scarcity and cost have been taken into consideration for new material. These are important considerations for a technology that can have a potential cost-effective large scale deployment. A robust, high temperature thermoelectric material characterization tool (Z-meter) has been developed with proper radiation suppression (20x below black body radiation) and low system parasitics (41.6% lower electrical contact parasitic that previous published results). We investigated novel metalsemiconductor superlattice structures ((HfZr)N/ScN) using the Z-meter setup. Low thermal conductivities (2.5-5 W/m.K) have been measured for temperature range of 300-650 K. The Seebeck coefficient of 132 [mu]V/K was measured at 830 K, which is comparable to the state-of-the-art SiGe at similar temperature.
by Reja Amatya.
Ph.D.
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Chalk, Ryan. "Solar power generation in a mining town." Thesis, Chalk, Ryan (2017) Solar power generation in a mining town. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/38686/.
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Climate change is a pertinent issue facing governments and societies around the world. The industrial revolution has resulted in a steady increase in the average global temperature. The mining and energy production industries have been significant contributors to this change prompting governments to intervene by promoting low emission technology within these sectors. This thesis reviews the energy problem in Australia and the mining sector with a focus on the energy requirements and production methods utilised in Newman WA. BHP operate the largest open cut iron ore mine in the world requiring substantial amounts of energy to maintain.
Renewable energy in the form of utility scale solar photovoltaics (PV) provides a solution to these problems by providing emission free energy which can be used to supplement the existing natural gas turbines in operation. This research presents a custom renewable solution for the Newman scenario considering the specific township network, local weather conditions and load profile. A summary of the required PV output is presented to supply slightly over 50% of the towns power requirements during the peak (summer) period, resulting in close to full coverage in the trough (winter) period. Power Factory is used to simulate the characteristics of the existing infrastructure and produces results of integrating PV. These results conclude that the problems requiring mitigation strategies unacceptable levels of harmonics and low power factor.
Strategies are proposed to control these issues predominantly through the use of high quality, made for purpose inverters. Results show that use of inverters with harmonic filtering dramatically reduce the level of harmonic injections to an acceptable level according to Australian standards. Furthermore, the configuration of inverters to supply active and reactive power assist in mitigating low power factor problems.
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Oliveira, Pedro Nuno Ferreira Pino de. "Optimal scheduling of hydro-thermal power generation systems." Thesis, University of Strathclyde, 1992. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21228.
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This thesis is concerned with the optimal scheduling of hydro-thermal power generation systems. This problem, usually referred to as the unit commitment and economic dispatch problem, manifests itself as a large scale mixed integer programming problem. In the first instance a linear model is built and solved using branch-and-bound. This approach is, however, very expensive in terms of computational time. Using Lagrangian relaxation the original primal problem may be written in a dual formulation: the problem then admits decomposition into more tractable subproblems. Furthermore, the primal solution can be approximated closely from the dual solution using the duality gap as a termination criterion. A heuristic is used to construct nearly optimal solutions to the primal problem based on the information provided by the dual problem. The decomposition is such as to allow an implementation on a transputer array with significant reductions in the computational time. An investigation into the application of genetic algorithms to power scheduling shows that this approach is feasible although expensive in terms of computational time. Lagrangian relaxation is next used to solve a nonlinear model incorporating the purchasing and selling of electricity. The information provided by the Lagrange multipliers which can be interpreted as shadow prices, is used to determine the best strategy for the purchasing and selling of energy. Nonconvex programming problems such as this may exhibit a duality gap, that is a difference between the optimal solution of the primal and dual problems. An investigation of this problem for power scheduling linked the existence of this gap to the operating constraints of the system.
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Coventry, Joseph Sydney. "A solar concentrating photovoltaic/thermal collector /." View thesis entry in Australian Digital Theses Program, 2004. http://thesis.anu.edu.au/public/adt-ANU20041019.152046/index.html.
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ZHANG, SHAN. "Analytical system for photovoltaic and concentratingsolar power generation." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-16174.
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Energy is the material foundation of human survival and development. Throughout human industrialization process, the fossil energy has made tremendous contributions in the progress of human civilization, economic and social development. For a long time, the development of human energy use patterns makes fossil fuels rapidly depleted and the consequences of environmental deterioration by this pattern lead to the severe challenge for mankind. Many countries start paying more attention to develop the new energy. The solar electricity production system is one of the main new energy power generations. The thesis is a guide of principle for solar power generation system. It focuses on comparisons between photovoltaic and concentrating solar power generations and analysis of their market prospects. The merits and demerits of these two systems will also be pointed out in this thesis.
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Hess, Stefan. "Low-concentrating, stationary solar thermal collectors for process heat generation." Thesis, De Montfort University, 2014. http://hdl.handle.net/2086/10874.
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The annual gain of stationary solar thermal collectors can be increased by non-focusing reflectors. Such concentrators make use of diffuse irradiance. A collector’s incidence angle modifier for diffuse (diffuse-IAM) accounts for this utilization. The diffuse irra-diance varies over the collector hemisphere, which dynamically influences the diffuse-IAM. This is not considered by state-of-the-art collector models. They simply calculate with one constant IAM value for isotropic diffuse irradiance from sky and ground. This work is based on the development of a stationary, double-covered process heat flat-plate collector with a one-sided, segmented booster reflector (RefleC). This reflector approximates one branch of a compound parabolic concentrator (CPC). Optical meas-urement results of the collector components as well as raytracing results of different variants are given. The thermal and optical characterization of test samples up to 190 °C in an outdoor laboratory as well as the validation of the raytracing are discussed. A collector simulation model with varying diffuse-IAM is described. Therein, ground reflected and sky diffuse irradiance are treated separately. Sky diffuse is weighted with an anisotropic IAM, which is re-calculated in every time step. This is realized by gener-ating an anisotropic sky radiance distribution with the model of Brunger and Hooper, and by weighting the irradiance from distinct sky elements with their raytraced beam-IAM values. According to the simulations, the RefleC booster increases the annual out-put of the double-covered flat-plate in Würzburg, Germany, by 87 % at a constant inlet temperature of 120 °C and by 20 % at 40 °C. Variations of the sky diffuse-IAM of up to 25 % during one day are found. A constant, isotropic diffuse-IAM would have under-valued the gains from the booster by 40 % at 40 °C and by 20 % at 120 °C. The results indicate that the gain of all non-focusing solar collectors is undervalued when constant, isotropic diffuse-IAMs calculated from raytracing or steady-state test data are used. Process heat generation with RefleC is demonstrated in a monitored pilot plant at work-ing temperatures of up to 130 °C. The measured annual system utilization ratio is 35 %. Comparing the gains at all inlet temperatures above 80 °C, the booster increases the an-nual output of the double-covered flat-plates by 78 %. Taking all inlet temperatures, the total annual gains of RefleC are 39 % above that of the flat-plates without reflectors. A qualitative comparison of the new simulation model results to the laboratory results and monitoring data shows good agreement. It is shown that the accuracy of existing collector models can be increased with low effort by calculating separate isotropic IAMs for diffuse sky and ground reflected irradiance. The highest relevance of this work is seen for stationary collectors with very distinctive radiation acceptance.
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Spelling, James. "Steam Turbine Optimisation for Solar Thermal Power Plant Operation." Licentiate thesis, KTH, Kraft- och värmeteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-35386.
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The provision of a sustainable energy supply is one of the most important issues facing humanity at the current time, given the strong dependence of social and economic prosperity on the availability of affordable energy and the growing environmental concerns about its production. Solar thermal power has established itself as a viable source of renewable power, capable of generating electricity at some of the most economically attractive rates. Solar thermal power plants are based largely on conventional Rankine-cycle power generation equipment, reducing the technological risk involved in the initial investment. Nevertheless, due to the variable nature of the solar supply, this equipment is subjected to a greater range of operating conditions than would be the case in conventional systems. The necessity of maintaining the operational life of the steam-turbines places limits on the speed at which they can be started once the solar supply becomes available. However, in order to harvest as much as possible of the Sun’s energy, the turbines should be started as quickly as is possible. The limiting factor in start-up speed being the temperature of the metal within the turbines before start-up, methods have been studied to keep the turbines as warm as possible during idle-periods. A detailed model of the steam-turbines in a solar thermal power plant has been elaborated and validated against experimental data from an existing power plant. A dynamic system model of the remainder of the plant has also been developed in order to provide input to the steam-turbine model. Three modifications that could potentially maintain the internal temperature of the steam-turbines have been analysed: installation of additional insulation, increasing the temperature of the gland steam and use of external heating blankets. A combination of heat blankets and gland steam temperature increase was shown to be the most effective, with increases in electricity production of up to 3% predicted on an annual basis through increased availability of the solar power plant.Hållbar energiförsörjning är för närvarande en av de viktigaste frågorna för mänskligheten. Socialt och ekonomiskt välstånd är starkt kopplat till rimliga energipriser och hållbar energiproduktion. Koncentrerad solenergi är nu etablerad som en tillförlitlig källa av förnybar energi och är också ett ekonomiskt attraktivt alternativ. Koncentrerade solenergikraftverk bygger till stor del på konventionella Rankine-cykel elgeneratorer, vilka minskar de tekniskt relaterade riskerna i den initiala investeringen. På grund av solstrålningens skiftande karaktär utsätts denna utrustning för mer varierade driftsförhållanden, jämfört med konventionella system. Behovet av att bibehålla den operativa livslängden på ångturbiner sätter gränser för uppstartshastigheten. För att utnyttja så mycket som möjligt av solens energi bör ångturbinen startas så snabbt som möjligt när solstrålningen blir tillgänglig. Eftersom temperaturen i metalldelar hos turbinerna är den begränsande faktorn, har metoder studerats för att hålla turbinerna så varma som möjligt under tomgångsperioder. En detaljerad modell av ångturbiner i ett solenergikraftverk har utvecklats och validerats mot experimentella data från ett befintligt kraftverk. En dynamisk systemmodell av de övriga delarna av anläggningen har också utvecklats för att ge input till ångturbinsmodellen. Tre modifieringar som potentiellt kan bidra till att upprätthålla den inre temperaturen i ångturbiner har analyserats: montering av ytterligare isolering, ökning av temperaturen hos glänsångan och användning av elvärmefiltar. En kombination av elvärmefiltar och en temperaturökning av glänsångan visade sig vara det mest effektiva alternativet. Åtgärderna resulterade i en ökad elproduktion på upp till 3%, beräknat på årsbasis genom ökad tillgänglighet hos kraftverket.
QC 20110629
TURBOKRAFT
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Fernandez-Munoz, Raul. "Design of solar power plant with coupled thermal storage." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/16722.
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El, Khaja Ragheb Mohamad Fawaz. "Solar-thermal hybridization of Advanced Zero Emissions Power Plants." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74434.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 43-44).
Carbon Dioxide emissions from power production are believed to have significant contributions to the greenhouse effect and global warming. Alternative energy resources, such as solar radiation, may help abate emissions but suffer from high costs of power production and temporal variations. On the other hand, Carbon Capture and Sequestration allows the continued use of fossil fuels without the CO2 emissions but it comes at an energetic penalty. The Advanced Zero Emissions Plant (AZEP) minimizes this energy loss by making use of Ion Transport Membrane (ITM)-based oxy-combustion to reduce the cost of carbon dioxide separation. This work seeks to assess if there are any thermodynamic gains from hybridizing solar-thermal energy with AZEP. The particular focus is hybridizing of the bottoming cycle with supplemental solar heating. A simple model of parabolic solar trough was used to hybridize a model of the AZEP cycle in ASPEN Plus*. Two cycle configurations are studied: the first uses solar parabolic troughs to indirectly vaporize high pressure steam through Therminol and the second uses parabolic troughs to directly preheat the high pressure water stream prior to vaporization. Simulations of the solar vaporizer hybrid by varying the total area of collectors (holding fuel input constant) show an increase of net electric output from 439MW for the non-hybridized AZEP to 533MW with an input solar share of 38.8%. The incremental solar efficiency is found to be around 16% for solar shares of input ranging from 5% to 38.8%. Moreover, simulations of variable solar insolation for collector area of 550,000 m2 , show that incremental solar efficiency increased with solar insolation reaching a plateau around 17%. Simulations of the direct solar preheater, show a net electric output of 501.3 MW for a solar share of 35%, (an incremental solar efficiency of 13.73%). The power generation and hence incremental efficiency is lower than in hybridization with steam vaporization with the same input solar share. Synergy analysis for the steam vaporization hybrid indicates no thermodynamic gains from hybridization.
by Ragheb Mohamad Fawaz El Khaja.
S.B.
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Allen, Kenneth Guy. "Rock bed thermal storage for concentrating solar power plants." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86521.
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Thesis (PhD)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Concentrating solar power plants are a promising means of generating electricity. However, they are dependent on the sun as a source of energy, and require thermal storage to supply power on demand. At present thermal storage – usually molten salt – although functional, is expensive, and a cheaper solution is desired. It is proposed that sensible heat storage in a packed bed of rock, with air as heat transfer medium, is suitable at temperatures of 500 – 600 °C. To determine if this concept is technically feasible and economically competitive with existing storage, rock properties, packed bed pressure drop and thermal characteristics must be understood. This work addresses these topics. No previously published data is available on thermal cycling resistance of South African rock, and there is limited data from other countries in the proposed temperature range for long-term thermal cycling, so samples were thermally cycled. There is rock which is suitable for thermal storage applications at temperatures of 500 – 600 °C. New maps of South Africa showing where potentially suitable rock is available were produced. Dolerite, found extensively in the Karoo, is particularly suitable. Friction factors were measured for beds of different particles to determine the importance of roughness, shape, and packing arrangement. Five sets of rock were also tested, giving a combined dataset broader than published in any previous study. Limitations of existing correlations are shown. The friction factor is highly dependent on particle shape and, in the case of asymmetric particles, packing method. The friction factor varied by up to 70 % for crushed rock depending on the direction in which it was poured into the test section, probably caused by the orientation of the asymmetric rock relative to the air flow direction. This has not been reported before for rock beds. New isothermal correlations using the volume equivalent particle diameter are given: they are within 15 % of the measurements. This work will allow a techno-economic evaluation of crushed rock beds using more accurate predictions of pumping power than could previously be made. Thermal tests below 80 °C show that bed heat transfer is insensitive to particle shape or type. A heat transfer correlation for air in terms of the volume equivalent diameter was formulated and combined with the E-NTU method. The predicted bed outlet temperatures are within 5 °C of the measurements for tests at 530 °C, showing that the influence of thermal conduction and radiation can be reasonably negligible for a single charge/discharge cycle at mass fluxes around 0.2 kg/m2s. A novel method for finding the optimum particle size and bed length is given: The Biot number is fixed, and the net income (income less bed cost) from a steam cycle supplied by heat from the bed is calculated. A simplified calculation using the method shows that the optimum particle size is approximately 20 mm for bed lengths of 6 – 7 m. Depending on the containment design and cost, the capital cost could be an order of magnitude lower than a nitrate salt system.
AFRIKAANSE OPSOMMING: Gekonsentreerde son-energie kragstasies is n belowende manier om elektrisiteit op te wek, maar hulle is afhanklik van die son as n bron van energie. Om drywing op aanvraag te voorsien moet hulle energie stoor. Tans is termiese stoor – gewoonlik gesmelte sout – hoewel funksioneel, duur, en n goedkoper oplossing word gesoek. Daar word voorgestel dat stoor van voelbare warmte-energie in n gepakte rotsbed met lug as warmteoordrag medium geskik is by temperature van 500 – 600 °C. Om te bepaal of dié konsep tegnies gangbaar en ekonomies mededingend met bestaande stoorstelsels is, moet rotseienskappe, gepakte bed drukval en hitteoordrag verstaan word. Hierdie werk spreek hierdie aspekte aan. Geen voorheen gepubliseerde data is beskikbaar oor die termiese siklus weerstand van Suid-Afrikaanse rots nie, en daar is beperkte data van ander lande in die voorgestelde temperatuurbereik, dus is monsters onderwerp aan termiese siklusse. Daar bestaan rots wat geskik is vir termiese stoor toepassings by temperature van 500 – 600 °C. Nuwe kaarte van Suid-Afrika is opgestel om te wys waar potensieel geskikte rots beskikbaar is. Doleriet, wat wyd in die Karoo voor kom, blyk om veral geskik te wees. Wrywingsfaktore is gemeet vir beddens van verskillende partikels om die belangrikheid van grofheid, vorm en pak-rangskikking te bepaal. Vyf rotsstelle is ook getoets, wat n saamgestelde datastel gee wyer as in enige gepubliseerde studie. Beperkings van bestaande korrelasies word aangetoon. Die wrywingsfaktor is hoogs sensitief vir partikelvorm en, in die geval van asimmetriese partikels, pakkings metode. Die wrywingsfaktor het met tot 70 % gevarieer vir gebreekte rots, afhanklik van die rigting waarin dit in die toetsseksie neergelê is. Dit is waarskynlik veroorsaak deur die oriëntasie van die asimmetriese rots relatief tot die lugvloei rigting, en is nie voorheen vir rotsbeddens gerapporteer nie. Nuwe isotermiese korrelasies wat gebruik maak van die volume-ekwivalente partikel deursnee word gegee: hulle voorspel binne 15 % van die gemete waardes. Hierdie werk sal n tegno-ekonomiese studie van rotsbeddens toelaat wat meer akkurate voorspellings van pompdrywing gebruik as voorheen moontlik was. Termiese toetse onder 80 °C wys dat die warmteoordrag nie baie sensitief is vir partikelvorm en -tipe nie. n Warmte-oordragskorrelasie vir lug in terme van die volume-ekwivalente deursnee is ontwikkel en met die E-NTU-metode gekombineer. Die voorspelde lug uitlaat temperatuur is binne 5 °C van die meting vir toetse by 530 °C. Dit wys dat termiese geleiding en straling redelikerwys buite rekening gelaat kan word vir n enkele laai/ontlaai siklus by massa vloeitempos van omtrent 0.2 kg/m2s. n Oorspronklike metode vir die bepaling van die optimum partikelgrootte en bedlengte word gegee: Die Biot-getal is vas, en die netto inkomste (die inkomste minus die bed omkoste) van n stoomsiklus voorsien met warmte van die bed word bereken. n Vereenvoudigde berekening wat die metode gebruik wys dat die optimum grootte en lengte ongeveer 20 mm en 6-7 m is. Afhangende van die behoueringsontwerp en koste, kan die kapitale koste n orde kleiner wees as dié van n gesmelte nitraatsout stelsel
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Allen, Kenneth Guy. "Performance characteristics of packed bed thermal energy storage for solar thermal power plants." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4329.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Solar energy is by far the greatest energy resource available to generate power. One of the difficulties of using solar energy is that it is not available 24 hours per day - some form of storage is required if electricity generation at night or during cloudy periods is necessary. If a combined cycle power plant is used to obtain higher efficiencies, and reduce the cost of electricity, storage will allow the secondary cycle to operate independently of the primary cycle. This study focuses on the use of packed beds of rock or slag, with air as a heat transfer medium, to store thermal energy in a solar thermal power plant at temperatures sufficiently high for a Rankine steam cycle. Experimental tests were done in a packed bed test section to determine the validity of existing equations and models for predicting the pressure drop and fluid temperatures during charging and discharging. Three different sets of rocks were tested, and the average size, specific heat capacity and density of each set were measured. Rock and slag samples were also thermally cycled between average temperatures of 30 ºC and 510 ºC in an oven. The classical pressure drop equation significantly under-predicts the pressure drop at particle Reynolds numbers lower than 3500. It appears that the pressure drop through a packed bed is proportional to the 1.8th power of the air flow speed at particle Reynolds numbers above about 500. The Effectiveness-NTU model combined with a variety of heat transfer correlations is able to predict the air temperature trend over the bed within 15 % of the measured temperature drop over the packed bed. Dolerite and granite rocks were also thermally cycled 125 times in an oven without breaking apart, and may be suitable for use as thermal storage media at temperatures of approximately 500 ºC. The required volume of a packed bed of 0.1 m particles to store the thermal energy from the exhaust of a 100 MWe gas turbine operating for 8 hours is predicted to be 24 × 103 m3, which should be sufficient to run a 25-30 MWe steam cycle for over 10 hours. This storage volume is of a similar magnitude to existing molten salt thermal storage.
AFRIKAANSE OPSOMMING: Sonenergie is die grootste energiebron wat gebruik kan word vir krag opwekking. ‘n Probleem met die gebruik van sonenergie is dat die son nie 24 uur per dag skyn nie. Dit is dus nodig om die energie te stoor indien dit nodig sal wees om elektrisiteit te genereer wanneer die son nie skyn nie. ‘n Gekombineerde kringloop kan gebruik word om ‘n hoër benuttingsgraad te bereik en elektrisiteit goedkoper te maak. Dit sal dan moontlik wees om die termiese energie uit die primêre kringloop te stoor, wat die sekondêre kringloop onafhanklik van die primêre kringloop sal maak. Dié gevalle studie ondersoek die gebruik van ‘n slakof- klipbed met lug as hitteoordragmedium, om te bepaal of dit moontlik is om hitte te stoor teen ‘n temperatuur wat hoog genoeg is om ‘n Rankine stoom kringloop te bedryf. Eksperimentele toetse is in ‘n toets-bed gedoen en die drukverandering oor die bed en die lug temperatuur is gemeet en vergelyk met voorspelde waardes van vergelykings en modelle in die literatuur. Drie soorte klippe was getoets. Die gemiddelde grootte, spesifieke hitte-kapasiteit en digtheid van elke soort klip is gemeet. Klip en slak monsters is ook siklies tussen temperature van 30 ºC en 510 ºC verkoel en verhit. Die klassieke drukverlies vergelyking gee laer waardes as wat gemeet is vir Reynolds nommers minder as 3500. Dit blyk dat die drukverlies deur ‘n klipbed afhanklik is van die lug vloeispoed tot die mag 1.8 as die Reynolds nommer groter as omtrent 500 is. Die ‘Effectiveness-NTU’ model gekombineerd met ‘n verskeidenheid van hitteoordragskoeffisiënte voorspel temperature binne 15 % van die gemete temperatuur verskil oor die bed. Doloriet en graniet klippe het 125 sikliese toetse ondergaan sonder om te breek, en is miskien gepas vir gebruik in ‘n klipbed by temperature van sowat 500 ºC Die voorspelde volume van ‘n klipbed wat uit 0.1 m klippe bestaan wat die termiese energie vir 8 ure uit die uitlaat van ‘n 100 MWe gasturbiene kan stoor, is 24 × 103 m3. Dit behoort genoeg te wees om ‘n 25 – 30 MWe stoom kringloop vir ten minste 10 ure te bedryf. Die volume is min of meer gelyk aan dié van gesmelte sout store wat alreeds gebou is.
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Palermo, Rick. "Analysis of solar power generation on California turkey ranches." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1607.
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Guarracino, Ilaria. "Hybrid photovoltaic and solar thermal (PVT) systems for solar combined heat and power." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/58172.
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Solar is a particularly promising sustainable energy source in terms of its potential to displace the burning of fossil fuels for heat and power, heating and even cooling, albeit at a cost. The sun load-factor profile has a close and predictable match to the daily varying energy demand for heat and electricity, both thermal and electrical, and thermal storage for periods of low irradiance can be made readily available. In addition, solar thermal technologies can provide a significant fraction of the hot water demand in households, as well as space heating and cooling in residential buildings and for industrial facilities. In fact, solar heating has been proposed as one of the leading solutions in terms of its potential for greenhouse gas abatement [1]. At the small scale, photovoltaic systems presently dominate the domestic solar market with solar to electrical conversion efficiencies of around 15% and at a competitive cost for the building owner. Solar photovoltaic installations were encouraged in Europe at the local level with financial support and now constitute a large and mature market with continuously falling prices. Solar thermal systems are able to make use of a larger proportion of the solar resource as they convert solar energy into heat with a higher efficiency than the PV conversion efficiency. Moreover, the low temperature heat may be used to satisfying the largest portion of the demand for thermal energy that is currently met by fossil fuels. The development of the solar thermal market is strongly dependent on the availability of the local irradiance level and on the cost of the alternative sources of thermal energy. In some countries in Europe the solar thermal market is quite mature (e.g. Austria), whilst in others, such as in the UK, solar thermal energy still contributes marginally to the energy mix and solar thermal systems are not yet cost competitive. Due to the high costs of solar thermal energy systems, these constitute a relatively small market at present with the potential to grow substantially in the near future. A competitive solution for energy (heat and power) provision in buildings is the development of combined solar photovoltaic/thermal (PVT) systems which produce both electricity and heat simultaneously from the same aperture area. This solution is particularly suited to residential applications in urban areas, where the demand for electricity is accompanied by a demand for low temperature heat, and space for solar installations is scarce. Many alternative technologies for PVT integration exist and PVT units can be coupled with various systems for domestic hot water generation and/or space heating. At the design stage of a PVT system, decisions have to be made on the absorber characteristics (consisting of thermal collector and PV laminate), on the thermal to electrical yield ratio and on the application (industrial or residential application, stand alone or grid connected). These design parameters influence the requirements on the fluid temperature and electricity output, and the overall efficiency. In addition, system control can significantly impact the potential of such systems in terms of their performance characteristics in different applications. The aim of this present research effort was to demonstrate the technical and practical feasibility of a novel, high-efficiency hybrid PVT water system, by considering an affordable, small-scale, modular unit that can be scaled easily to cater to varying demand levels. The research investigated the technical issues related to PVT panel technology, by looking in particular at the optical efficiency of the PV cells, at the heat transfer from the PV cells to the fluid, and at the integration of such a unit in a heat and power provision system that attempts to match generation and local demand. A detailed numerical model was developed that constitutes a tool for testing various collector and system designs. The model was validated against experimental data. An experimental apparatus was designed and constructed for the purpose of evaluating the collector model and for collecting a database of performance data on PVT collectors. Collector performance data are scarce at the moment due to the relatively small market size, thus the work constitutes a reference for further development and analysis of this type of collectors. Steady-state tests and dynamic tests were performed on PVT collectors and the results were used to develop a reliable model of collector performance over a wide range of time-varying operating conditions. The model allowed for assessments of various solar PVT system designs under different operating conditions and control strategies. Result showed that such systems may underperform if their operation and design is not designed specifically for the local weather conditions and user-demand specific requirements. It is envisaged that emissivity control applied to the solar cells should be adopted for PVT system application, especially if higher operating temperatures are required (e.g. in combination with thermally driven/heat powered cooling systems). The numerical model confirms that solar cells a with low emissivity coating can maximise the thermal energy output of a PVT system. The potential of improved PVT systems is finally assessed from an economic perspective, in an analysis that considers the potential cost reduction of PVT systems in relation to alternative technologies used as a benchmark.
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Nixon, Jonathan. "Solar thermal collectors for use in hybrid solar-biomass power plants in India." Thesis, Aston University, 2012. http://publications.aston.ac.uk/18722/.
Full textAbstract:
This thesis examined solar thermal collectors for use in alternative hybrid solar-biomass power plant applications in Gujarat, India. Following a preliminary review, the cost-effective selection and design of the solar thermal field were identified as critical factors underlying the success of hybrid plants. Consequently, the existing solar thermal technologies were reviewed and ranked for use in India by means of a multi-criteria decision-making method, the Analytical Hierarchy Process (AHP). Informed by the outcome of the AHP, the thesis went on to pursue the Linear Fresnel Reflector (LFR), the design of which was optimised with the help of ray-tracing. To further enhance collector performance, LFR concepts incorporating novel mirror spacing and drive mechanisms were evaluated. Subsequently, a new variant, termed the Elevation Linear Fresnel Reflector (ELFR) was designed, constructed and tested at Aston University, UK, therefore allowing theoretical models for the performance of a solar thermal field to be verified. Based on the resulting characteristics of the LFR, and data gathered for the other hybrid system components, models of hybrid LFR- and ELFR-biomass power plants were developed and analysed in TRNSYS®. The techno-economic and environmental consequences of varying the size of the solar field in relation to the total plant capacity were modelled for a series of case studies to evaluate different applications: tri-generation (electricity, ice and heat), electricity-only generation, and process heat. The case studies also encompassed varying site locations, capacities, operational conditions and financial situations. In the case of a hybrid tri-generation plant in Gujarat, it was recommended to use an LFR solar thermal field of 14,000 m2 aperture with a 3 tonne biomass boiler, generating 815 MWh per annum of electricity for nearby villages and 12,450 tonnes of ice per annum for local fisheries and food industries. However, at the expense of a 0.3 ¢/kWh increase in levelised energy costs, the ELFR increased saving of biomass (100 t/a) and land (9 ha/a). For solar thermal applications in areas with high land cost, the ELFR reduced levelised energy costs. It was determined that off-grid hybrid plants for tri-generation were the most feasible application in India. Whereas biomass-only plants were found to be more economically viable, it was concluded that hybrid systems will soon become cost competitive and can considerably improve current energy security and biomass supply chain issues in India.
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Zhuang, Fulin 1956. "Optimal generation unit commitment in thermal electric power systems." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75896.
Full textAbstract:
This thesis is devoted to the optimal commitment of generation units in an all-thermal, single or multiple area, power system. The problem, known as unit commitment, is a nonlinear mixed program typically with thousands of 0-1 integer variables and diverse constraints. An exact optimal solution to the problem is only possible via (explicit or implicit) enumeration, which requires a prohibitively long computation time for large problem instances.Two optimization approaches, Lagrangian relaxation and simulated annealing, are explored in this thesis for efficient and near-optimal unit commitment.
Lagrangian relaxation combines the solution of the dual of the unit commitment problem with feasibility search to obtain primal feasible solutions. The feasibility search is necessary because a solution to the dual seldom solves the primal, and because little theory is available to bridge the optimal dual and primal solutions. In this thesis, several new feasibility search procedures to find a near-optimal primal feasible solution from the dual solution are developed and tested. These procedures are independent of the data constituting different problem instances, and are more rigorous and systematic than the existing ones. With these procedures, Lagrangian relaxation is successfully and efficiently applied to both single and multiple area unit commitment.
Simulated annealing exploits the resemblance between a minimization process and the cooling of a molten metal. The method generates feasible solution points randomly and moves among these points following a strategy which leads to a global minimum in a statistical sense. Simulated annealing is very flexible for handling diverse and complicated constraints, such as those typical of the unit commitment problem. Simulated annealing is analyzed, evaluated and implemented for unit commitment in this thesis.
Five major algorithms, proposed in this thesis for unit commitment and reserve-constrained economic dispatch, are extensively tested and compared by numerical simulation on sample power systems of 10 to 100 units. The simulation results show the efficiency of the tested algorithms for large-scale unit commitment and demonstrate the general applicability of simulated annealing. A comparison with the priority list method and a study of the convergence rates of the subgradient type algorithms are also included in the simulation.
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Mayer, Peter (Peter Matthew) 1978. "High-density thermoelectric power generation and nanoscale thermal metrology." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40503.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 299-305).
Thermoelectric power generation has been around for over 50 years but has seen very little large scale implementation due to the inherently low efficiencies and powers available from known materials. Recent material advances appear to have improved the technology's prospects. In this work we show that significantly increased generated power densities are possible even for established material technologies provided that parasitic losses are controlled and effective strategies are found for handling the large resulting heat fluxes. We optimize the performance of a thermoelectric generator in this regime, and discuss fundamental performance limits in this context. We present a design of a thermoelectric generator using conventional material and a microchannel heat sink that we predict can generate many times the power of a conventional thermoelectric, at a comparable efficiency. A high temperature vacuum test station is used to characterize the power generation, efficiency, and material properties of thermoelectric materials and generators. The results of a series of studies on various bulk and thin-film materials are presented, as well as packaged generator performance. The method of CCD thermoreflectance imaging is pursued in this thesis as a quantitative means for making noncontact temperature measurements on solid-state samples at the micro- and nano-scale. We develop and test a theory of the instrument and the measurement process to rigorously characterize the accuracy and precision of the resulting thermal images. We experimentally demonstrate sub-micron spatial resolution and sub-20 mK temperature resolution with this tool. High-resolution thermal images of thermoelectric elements, polysilicon-gate field effect transistors, and other integrated electronic devices are presented.
by Peter M. Mayer.
Ph.D.
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Sheu, Elysia J. (Elysia Ja-Zeng). "A solar reforming system for use in hybrid solar-fossil fuel power generation." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103734.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 229-241).
As demand for energy continues to rise, the concern over the increase in emissions grows, prompting much interest in using renewable energy resources such as solar energy. However, there are numerous issues with using solar energy including intermittency and the need for storage. A potential solution is the concept of hybrid solar-fossil fuel power generation. Previous work has shown that utilizing solar reforming in conventional power cycles has higher performance compared to other integration methods. In this thesis, a two level analysis of a hybrid redox redox cycle is performed. First, a system analysis of a hybrid cycle utilizing steam redox reforming is presented. Important cycle design and operation parameters such as the oxidation temperature and reformer operating pressure are identified and their effect on both the reformer and cycle performance is discussed. Simulation results show that increasing oxidation temperature can improve reformer and cycle efficiency. Also shown is that increasing the amount of reforming water leads to a higher reformer efficiency, but can be detrimental to cycle efficiency depending on how the reforming water is utilized. Next, a system analysis for a CO2 redox reforming hybrid cycle and comparison of cycle and reformer performance between a CO 2 redox reformer and steam redox reformer hybrid cycle are presented. Similar to the steam redox system, results show that increasing the oxidation temperature or the amount of reforming CO2 leads to higher reformer and cycle efficiencies. In addition, the comparison between the CO2 and steam redox reformer hybrid cycles shows that the CO2 cycle has the potential to have better overall performance.Based on the system analysis, a reformer level analysis is also performed. A novel receiver reactor concept for a solar steam redox reformer is presented, and a computational model is developed to assess its performance. The receiver-reactor consists of a dumbbell shape absorber system that has two distinct absorbers. This absorber system setup allows for the switching between reduction and oxidation steps without having to constantly change inlet streams to the reactor and is designed such that the inlet connections do not interfere with the solar window. In addition, at any point in time only one solar absorber is irradiated by the solar energy (during the reduction step). Simulation results show that the receiver-reactor strongly absorbs the solar radiation and most of the radiative heat transfer occurs in the front half of the reactor. Moreover, results show that higher conductivity absorber materials are more suitable for long term reactor operation. A sensitivity analysis is also performed for the solar steam redox reformer with respect to different performance metrics. Important parameters include channel size, inlet temperature, and reformer pressure. Moreover, a strategy for reactor design based on performance as well as integration with the power cycle is discussed.
by Elysia J. Sheu.
Ph. D.
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Kim, Byungyu. "Solar Energy Generation Forecasting and Power Output Optimization of Utility Scale Solar Field." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2149.
Full textAbstract:
The optimization of photovoltaic (PV) power generation system requires an accurate system performance model capable of validating the PV system optimization design. Currently, many commercial PV system modeling programs are available, but those programs are not able to model PV systems on a distorted ground level. Furthermore, they were not designed to optimize PV systems that are already installed. To solve these types of problems, this thesis proposes an optimization method using model simulations and a MATLAB-based PV system performance model. The optimization method is particularly designed to address partial shading issues often encountered in PV system installed on distorted ground. The MATLAB-based model was validated using the data collected from the Cal Poly Gold Tree Solar Field. It was able to predict the system performance with 96.4 to 99.6 percent accuracy. The optimization method utilizes the backtracking algorithm already installed in the system and the pitch distance to control the angle of the tracker and reduces solar panels partial shading on the adjacent row to improve system output. With pitch distances reduced in the backtracking algorithm between 2.5 meters and 3 meters, the inverter with inter-row shading can expect a 10.4 percent to 28.9 percent increase in power production. The implementation and calibration of this optimization method in the field this spring was delayed due to COVID-19. The field implementation is now expected to start this summer.
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Darwish, Mazen. "Modular Hybridization of Solar Thermal Power Plants For Developing Nations." Thesis, KTH, Kraft- och värmeteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104456.
Full textAbstract:
The current energy scenario in the developing nations with abundant sun resource (e.g. southern Mediterranean countries of Europe, Middle-East & North Africa) relies mainly on fossil fuels to supply the increasing energy demand. Although this long adopted pattern ensures electricity availability on demand at all times through the least cost proven technology, it is highly unsustainable due to its drastic impacts on depletion of resources, environmental emissions and electricity prices. Solar thermal Hybrid power plants among all other renewable energy technologies have the potential of replacing the central utility model of conventional power plants, the understood integration of solar thermal technologies into existing conventional power plants shows the opportunity of combining low cost reliable power and Carbon emission reduction. A literature review on the current concentrating solar power (CSP) technologies and their suitability for integration into conventional power cycles was concluded, the best option was found be in the so called Integrated solar combined cycle systems (ISCCS); the plant is built and operated like a normal combined cycle, with a solar circuit consisting of central tower receiver and heliostat field adding heat to the bottoming Rankine cycle. A complete model of the cycle was developed in TRNSYS simulation software and Matlab environment, yearly satellite solar insolation data was used to study the effect of integrating solar power to the cycle throw-out the year. A multi objective thermo economic optimization analysis was conducted in order to identify a set of optimum design options. The optimization has shown that the efficiency of the combined cycle can be increased resulting in a Levelized electricity cost in the range of 10 -14 USDcts /Kwhe. The limit of annual solar share realized was found to be around 7 % The results of the study indicate that ISCCS offers advantages of higher efficiency, low cost reliable power and on the same time sends a green message by reducing the environmental impacts in our existing power plant systems.
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Bierman, David M. (David Matthew). "Where solar thermal meets photovoltaic for high-efficiency power conversion." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93859.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 71-73).
To develop disruptive techniques which generate power from the Sun, one must understand the aspects of existing technologies that limit performance. Solar thermal and solar photovoltaic schemes dominate today's solar market but both bring intrinsic and practical constraints. What will tomorrow's solar market look like? Third generation solar power generation techniques to utilize a larger portion of the solar spectrum are a promising path for high efficiency power generation, but experimental demonstrations remain limited. In this work, the components of a solar thermophotovoltaic power converter are introduced and discussed. While solar thermophotovoltaic devices have the potential to convert sunlight into electricity at astronomically high efficiencies, there are a number of practical challenges that must first be addressed. Novel photonic materials, design concepts, and both intrinsic and practical limitations of solar thermophotovoltaic conversion are explored in this thesis. The conversion mechanisms as well as a number of experimental implementations are presented. Finally, the device performance is characterized and both geometrical and spectral improvements are discussed.
by David M. Bierman.
S.M.
40
Nithyanandam, Karthik. "Investigations on Latent Thermal Energy Storage for Concentrating Solar Power." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23189.
Full textAbstract:
Thermal energy storage (TES) in a concentrating solar power (CSP) plant allows for continuous operation even during times when solar radiation is not available, thus providing a reliable output to the grid. Energy can be stored either as sensible heat or latent heat, of which latent heat storage is advantageous due to its high volumetric energy density and the high Rankine cycle efficiency owing to the isothermal operation of latent thermal energy storage (LTES) system. Storing heat in the form of latent heat of fusion of a phase change material (PCM), in addition to sensible heat, significantly increases the energy density, thus potentially reducing the storage size and cost. However, a major technical barrier to the use of latent thermal energy of PCM is the high thermal resistance to energy transfer due to the intrinsically low thermal conductivity of PCMs, which is a particularly acute constraint during the energy discharge. Secondly, for integration of TES in CSP plants, it is imperative that the cyclic exergetic efficiency be high, among other requirements, to ensure that the energy extracted from the system is at the maximum possible temperature to achieve higher cycle conversion efficiency in the power block.
The first objective is addressed through computational modeling and simulation to quantify the effectiveness of two different approaches to reduce the thermal resistance of PCM in a LTES, viz. (a) developing innovative, inexpensive and passive heat transfer devices that efficiently transfer large amount of energy between the PCM and heat transfer fluid (HTF) and (b) increase the heat transfer area of interaction between the HTF and PCM by incorporating the PCM mixture in small capsules using suitable encapsulation techniques.
The second portion of the research focuses on numerical modeling of large scale latent thermal storage systems integrated to a CSP plant with the aforementioned enhancement techniques and cascaded with more than one PCM to maximize the exergetic efficiency. Based on systematic parametric analysis on the various performance metrics of the two types of LTES, feasible operating regimes and design parameters are identified to meet the U.S. Department of Energy SunShot Initiative requirements including storage cost < $15/kWht and exergetic efficiency > 95%, for a minimum storage capacity of 14 h, in order to reduce subsidy-free levelized cost of electricity (LCE) of CSP plants from 21¢/kWh (2010 baseline) to 6¢/kWh, to be on par with the LCE associated with fossil fuel plants.Ph. D.
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Alsharkawi, Adham. "Automatic control of a parabolic trough solar thermal power plant." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/17890/.
Full textAbstract:
This thesis is interested in improving the operation of a parabolic trough technology based solar thermal power plant by means of automatic control. One of the challenging issues in a solar thermal power plant, from the control point of view, is to maintain the thermal process variables close to their desired levels. In contrast to a conventional power plant where fuel is used as the manipulated variable, in a solar thermal power plant, solar radiation cannot be manipulated and in fact it ironically acts as a disturbance due to its change on a daily and seasonal basis. The research facility ACUREX is used as a test bed in this thesis. ACUREX is a typical parabolic trough technology based solar thermal power plant and belongs to the largest research centre in Europe for concentrating solar technologies, namely the Plataforma Solar de Almería (PSA) in south-east Spain. The plant exhibits nonlinearities as well as resonance characteristics that lie well within the desired control bandwidth. Failure to adequately capture the resonance characteristics of the plant results in an undesired oscillatory control performance. Moreover, measured disturbances are an integral part of the plant and while some of the measured disturbances do not have a significant impact on the operation of the plant, others do. Hence, with the aim of handling the plant nonlinearities and capturing the plant resonance characteristics, while taking explicit account of the measured disturbances, in this thesis a gain scheduling feedforward predictive control strategy is proposed. The control strategy is based upon a family of local linear time-invariant state space models that are estimated around a number of operating points. The locally estimated linear time-invariant state space models have the key novelty of being able to capture the resonance characteristics of the plant with the minimal number of states and hence, simple analysis and control design. Moreover, while simple classical, series and parallel, feedforward configurations have been proposed and used extensively in the literature to mitigate the impact of the measured disturbances of the ACUREX plant, the proposed control strategy incorporates a feedforward systematically by including the effects of the measured disturbances of the ACUREX plant into the predictions of future outputs. In addition, a target (set point) for a control strategy is normally set at the ACUREX plant by the plant operator. However, in this thesis it is argued that, in parallel, the operator must choose between potentially ambitious and perhaps unreachable targets and safer targets. Ambitious targets can lead to actuator saturation and safer targets imply electricity production losses. Hence, in this thesis a novel two-layer hierarchical control structure is proposed with the gain scheduling feedforward predictive control strategy being deployed in a lower layer and an adequate reachable reference temperature being generated from an upper layer. The generated reference temperature drives the plant near optimal operating conditions, while satisfying the plant safety constraints, without any help from the plant operator and without adding cost. The proposed two-layer hierarchical control strategy has the potential benefits of: (i) maximising electricity production; (ii) reducing the risk of actuator saturation; (iii) extending the life span of various elements of the plant (e.g. synthetic oil, pump and valves) and (iv) limiting the role of the plant operator. The efficacy of the proposed two-layer hierarchical control strategy is evaluated using a nonlinear simulation model that approximates the dynamic behaviour of the ACUREX plant. The nonlinear simulation model is constructed in this thesis and validated in the time and frequency domain.
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Jradi, Fadi M. "Organic light-harvesting materials for power generation." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54976.
Full textAbstract:
This dissertation focuses on the design, synthesis, and characterization of a variety of organic dyes, semiconducting materials, and surface redox-active modifiers of potential interest to organic-based emerging photovoltaics. A discussion of the materials’ optoelectronic properties, their ability to modify and promote electron transfer through an organic/transparent conducting-oxide interface, and finally their effect on the photovoltaic properties of devices utilizing them as light-harvesters is provided where relevant. The first two research chapters discuss mono-chromophoric asymmetric squaraine-based sensitizers and covalently linked, dual-chromophoric, porphyrin-squaraine sensitizers as light absorbers in dye-sensitized solar cells (DSSCs), in an attempt to address two problems often encountered with DSSCs utilizing this class of near infra-red sensitizers; The lack of panchromatic absorption and aggregation on the surface. Also, this dissertation discusses the design and synthesis of asymmetric perylene diimide phosphonic acid (PDI-PA) redox-active surface modifiers, and reports on the electron-transfer rates and efficiencies across the interface of an ITO electrode (widely used in organic-electronic devices) modified with these perylene diimides. Finally two series of hole-transport materials based on oligothiophenes and benzodithiophenes are reported: optoelectronic properties and preliminary performance of organic photovoltaic (OPV) devices fabricated with them is discussed.
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Lin, Cynthia S. B. Massachusetts Institute of Technology. "Feasibility of using power steering pumps in small-scale solar thermal electric power systems." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43016.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaves 59-60).
The goal of this study was to determine performance curves for a variety of positive displacement pumps in order to select an efficient and low cost option for use as a boiler feed pump in a 1-kWe organic Rankine cycle (ORC) system built by the Solar Turbine Group in Lesotho. The pumps tested included OEM plunger and piston pumps, and rotary vane-type power steering pumps purchased from a junk yard. Motor speed and torque were measured at different flow rates to determine the power consumed to move fluid in the prescribed pressure regime. The test station was designed to pump deionized water; it was intended that measurements and calculations would then be non-dimensionalized and used to predict the ORC working fluid's properties. Unfortunately, deionized water caused the power steering pump shafts to seize; the efficiencies were below anticipated and the pumps were unable to operate under the specified pressures. It was discovered, after WD-40 was added to the water, that power steering pumps performed best when moving fluids with more lubricity. The optimal pump was selected based on how the pump efficiency affected the overall ORC system efficiency, defined as the electrical work output divided by the heat input, and the net electric power output. Power steering pumps achieved efficiencies between 34%-54% under the desired ORC operating conditions with water-oil emulsion as the working fluid. For that pump efficiency range, the overall solar thermal electric ORC system efficiency would be 7.4%-8.5% and the overall system cost would be USD 4.59-5.27 per installed Watt. Made specifically for pumping hydroflurorcarbons, the working fluid used in STG's ORC, the OEM Dynex pump exhibited poorer performance than predicted. The pump efficiency of 31% gave a system efficiency of 7.1% and a cost of USD 6.40 per installed Watt. The OEM water piston and plunger pumps made by Hypro achieved efficiencies of 70% and 81%, respectively, under the same ORC operating conditions described above.
(cont) For those pump efficiencies, the overall system efficiencies would be 9.0% and 9.2% and the costs would be USD 4.58 and 4.63 per installed Watt, respectively. The most optimal pump is the HyproPiston pump; although it costs nearly six times that of a power steering pump, the overall system cost is lower when normalized over the power output.
by Cynthia Lin.
S.B.
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Yazıcı, Osman Can Subaşılar Bedrettin. "Theoretical modeling and designing a line-focused horizontal -receiver- solar thermal power plant/." [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/enerjimuh/T000411.pdf.
Full textAbstract:
Thesis (Master)--İzmir Institute of Technology, İzmir, 2005Keywords: Solar energy plant, solar collectors, fresnel lens, spherical geometry, solar tracking system. Includes bibliographical references (leaves 113-114).
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Hess, Stefan [Verfasser]. "Low-Concentrating, Stationary Solar Thermal Collectors for Process Heat Generation / Stefan Hess." Aachen : Shaker, 2015. http://d-nb.info/1071528009/34.
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Guerreiro, Luís. "Energy optimization of a concentrated solar power plant with thermal storage." Doctoral thesis, Universidade de Évora, 2016. http://hdl.handle.net/10174/25594.
Full textAbstract:
One of the most relevant problems to solve at a planetary scale is the access to an affordable
clean source of energy as CO2 equivalent emissions should be reduced significantly. Some
authors aim for a zero emissions target for 2050. Renewable energies will play a leading role in
this energy transition, and solar energy with storage is a promising technology exploring a
renewable and worldwide available resource.
Within the present thesis component development like a new thermal storage thermocline tank
design or having latent heat storage capability are technological developments that have been
pursued and analyzed on a system perspective basis, focusing on reducing the LCOE value of
a commercial STE plant using TRNSYS software. Material research with molten salts mixtures
and cement based materials has been performed at lab scale. A fully validation should occur
through a 13 partners pan-European H2020 project called NEWSOL which has been developed
supported on the laboratory data obtained.
Moreover, incorporation of local available material, “modern slag” from an old mine of Alentejo
region, was also studied. The material could be used as an aggregate incorporated into calcium
aluminate cement (CAC) or as filler. This would help to solve a local environmental complex
problem related to soil, air and water pollution due to heavy metals and mining activity in Mina
de São Domingos, Southeast of Portugal.
The integration of these results underlies a broad energy transition model, a proposal is
presented in this thesis, with the aim to foster development towards a sustainable usage of
resources and promote clean technologies especially in the energy sector. This model can be
locally adapted depending on the pattern of existing industries. The goal is to achieve a smooth
transition into a clean tech energy society in line with the target of achieving zero emissions for
2050; Optimização Energética de uma Central de
Concentração Solar com Armazenamento de Energia
Resumo:
Um dos problemas mais relevantes a resolver a uma escala planetária é o acesso, com um
custo moderado, a fontes limpas de energia considerando que as emissões equivalentes de
CO2 derão ser reduzidas drasticamente. Alguns autores ambicionam mesmo um objetivo de
zero emissões em 2050. As energias renováveis irão desempenhar um papel preponderante
nesta transição energética, sendo que a energia solar com armazenamento é uma tecnologia
promissora que aproveita um recurso renovável e disponível em boa parte do Planeta.
Na presente tese foi realizado o desenvolvimento de componentes nomeadamente o design
que um novo tanque do tipo termocline, ou de novos elementos recorrendo ao calor latente,
desenvolvimentos tecnológicos que foram analizados de uma perspectiva de sistema, dando o
enfoque na redução do custo nivelado da electricidade (LCOE) para uma planta Termosolar
usando o software TRNSYS. Foi também realizada investigação em laboratório ao nível dos
materiais com várias misturas de sais fundidos inclusivé em contacto directo com materiais de
base cimenticia. Uma validação completa deverá ocorrer no projeto NEWSOL do programa
H2020 que reúne um consórcio de 13 parceiros europeus e que foi preparado e submetido
tendo por base os resultados laboratoriais obtidos.
Adicionalmente, incorporação de material disponível (escória de minério) de uma mina
abandonada da região do Alentejo foi outro dos aspectos estudados. Verificou-se que este
material poderá ser utilizado como agregado num ligante do tipo cimento de aluminato de
cálcio (CAC) ou como “filler”. Este re-aproveitamento resolveria um problema ambiental
complexo derivado do elevado conteúdo de metais pesados resultantes da actividade de
mineração e que actualamente provocam poluição do solo, água e ar na área da Mina de São
Domingos, Sudeste de Portugal.
Estes progressos deverão ser integrados num modelo de transição energética mais amplo. Na
presente tese, uma proposta concreta é apresentada, com o objectivo de incentivar o
desenvolvimento na direção de uma utilização sustentável dos recursos e a promoção de
tecnologias limpas nomeadamente no sector da energia. Este modelo poderá ser adaptado
localmente dependendo do padrão de indústrias existente. O objectivo é atingir uma transição
suave para uma sociedade de energias limpas em linha com o objectivo de atingir zero
emissões de CO2 equivalente em 2050.
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Bialobrzeski, Robert Wetherill. "Optimization of a SEGS solar field for cost effective power output." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24631.
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Dintrans, Philippe Lucien. "Solar ponds for electric power generation : cost model and feasibility study." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/44652.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Vita.
Bibliography: leaves 126-127.
by Philippe Lucien Dintrans.
M.S.
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Wu, Tzu-Wei, and 吳紫微. "Temperature Effect on the Performance of Solar Thermal Power Generation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/50026788004388398083.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
99
The aim of this thesis is to establish a small-scale solar thermal power generation system, and to investigate the efficiency-affecting factors. Fresnel lens is used as a concentrator to collect sunlight from larger area, and the power conversion unit consists of a Stirling engine and a power generator. Cooling device is also integrated into the Stirling engine so that larger temperature difference can be achieved. Finally, system output power and system efficiency were both monitored in the indoor and outdoor experiments. The indoor experiments are divided into two parts. The first one is using heat gun as the energy source. Experimental results shows that system efficiency increases 2.4 times when 7.6℃cooling water is injected. The second experiment uses Halogen lamp as virtual sunlight. Results show that total output energy of the system is increased 2 times by injecting 10.6℃cooling water. Experiments show that this system is a dynamic system. Therefore, the analysis of data is carried out by means of system identification. In analysis process, the system is divided into two parts. The first part discusses about relationship between illumination and the hot side temperature of the Stirling engine. Results show that the hot side temperature of the Stirling engine is strongly affected by not only illumination and but also natural convection. The second part is about temperature effect on the system output voltage. Results show that the trend of output voltage can be predicted by the temperature difference alone through a transfer function. Finally, six efficiency-affecting factors can be summarized.
50
Huang, Huan-Hsiang, and 黃煥翔. "Research and development of photovoltaic/thermal hybrid solar power generation system." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/50795549742758414315.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
90
The main purpose of the present research is to develop a photovoltaic/thermal hybrid solar power generation system to increase the solar energy usage efficiency, and actually to develop a prototype of air-transfer heat photovoltaic/thermal collector（aPV/T）.The design focal point of aPV/T focuses on modifying the rotation rate of the fan to control operational temperature of the solar cell, which can obtain higher power efficiency, and can transfer surplus thermal energy to heat water. However, in order to accurately control operational temperature of the solar cell, a temperature controller is designed by means of dynamic system identification, simulation, and series of tests conducted to evaluate the performance of the system. The results show that if operational temperature of the solar cell is set under 50℃,which the temperature error is between 0.1℃ and we can obtain the highest heat collection efficiency （0.28）, the performance of the heat collection system with this well designed temperature controller is high.