Rozprawy doktorskie na temat „POLYGENERATION SYSTEMS”

Ever-increasing energy consumption and consequent extensive greenhouse gas (GHG) emissions are two major urgent problems faced by all human beings in the 21st century. As a major contributor, the energy production section appears to be the most suitable field where further improvements could be explored to tackle these problems. Polygeneration is a typical type of next generation energy production technology with higher energy efficiency and lower/zero GHG emissions. However, methodologies guiding an efficient and stable transition from our existing energy systems to more advanced ones are still lacking. The purpose of this thesis is to provide a generic modelling and optimization framework to guide planning and design of energy systems. This framework of methodologies ad- dresses the following issues arising in the planning and designing of energy systems: a) decision making at both strategic planning level and process design level; b) selection of roadmaps, technologies, and types of equipment from many available options; c) planning or design according to both economic and environmental criteria; d) planning or design under inevitable and unpredictable future uncertainty. The thesis is organized as follows: first, a review of energy systems is presented, followed by methodologies of energy systems engineering and their applications. Then a section of polygeneration process modelling is provided, at both strategic planning and process design levels, comprising superstructure representations of polygeneration energy systems at different levels, implementations of the superstructure based modelling strategy using mixed-integer programming, multi-objective optimization for the optimal process design according to both economic and environmental criteria, and optimization under uncer- tainty to account the impacts of future uncertainties at the planning/design stage and to increase the flexibility and robustness of a process design. Finally, major achievements of this work are summarised and future research directions are recommended.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 301-319).
Polygeneration is a concept where multiple energy products are generated in a single plant by tightly integrating multiple processes into one system. Compared to conventional single-product systems, polygeneration systems have many economic advantages, such as potentially high profitability and high viability when exposed to market fluctuations. The optimal design of an energy polygeneration system that converts coal and biomass to electricity, liquid fuels (naphtha and diesel) and chemical products (methanol) with carbon dioxide (CO²) capture under different economic scenarios is investigated. In this system, syngas is produced by gasification of coal and/or biomass; purified by a cleaning process to remove particles, mercury, sulfur and CO²; and then split to different downstream sections such as the gas turbine, FT process and the methanol process. In this thesis, the optimal design with the highest net present value (NPV) is determined by optimizing equipment capacities, stream flow rates and stream split fractions. The case study results for static polygeneration systems reveal that the optimal design of polygeneration systems is strongly influenced by economic conditions such as feedstock prices, product prices, and potential emissions penalties for CO². Over the range of economic scenarios considered, it can be optimal to produce a mixture of electricity, liquid fuels, and methanol; only one each; or mixtures in-between. The optimal biomass/coal feed ratio significantly increases when the carbon tax increases or the biomass price decreases. An economic analysis of the optimal static polygeneration designs yielded a slightly higher NPV than comparable single-product plants. The flexible operation is then considered for the energy polygeneration system. In real applications, product prices can fluctuate significantly seasonally or even daily. The profitability of the polygeneration system can potentially be increased if some operational flexibility is introduced, such as adjusting the product mix in response to changing market prices. The major challenge of this flexible design is the determination of the optimal trade-off between flexibility and capital cost because higher flexibility typically implies both higher product revenues and larger equipment sizes. A two-stage optimization formulation for is used for the optimal design and operation of flexible energy polygeneration systems, which simultaneously optimizes design decision variables (e.g., equipment sizes) and operational decision variables (e.g., production rate schedules) in several different market scenarios to achieve the best expected economic performance. Case study results for flexible polygeneration systems show that for most of market scenarios, flexible polygeneration systems achieved higher expected NPVs than static polygeneration systems. Furthermore, even higher expected NPVs could be obtained with increases in flexibility. The flexible polygeneration optimization problem is a potentially large-scale nonconvex mixed-integer nonlinear program (MINLP) and cannot be solved to global optimality by state-of-the-art global optimization solvers, such as BARON, within a reasonable time. The nonconvex generalized Benders decomposition (NGBD) method can exploit the special structure of this mathematical programming problem and enable faster solution. In this method, the nonconvex MINLP is relaxed into a convex lower bounding problem which can be further reformulated into a relaxed master problem according to the principles of projection, dualization and relaxation. The relaxed master problem yields an nondecreasing sequence of lower bounds for the original problem. And an nonincreasing sequence of upper bounds is obtained by solving primal problems, which are generated by fixing the integer variables in the original problem. A global optimal objective is obtained when the lower and upper bounds coincide. The decomposition algorithm guarantees to find an E-optimal solution in a finite number of iterations. In this thesis, several enhanced decomposition methods with improved relaxed master problems are developed, including enhanced NGBD with primal dual information (NGBD-D), piecewise convex relaxation (NGBD-PCR) and lift-and-project cuts (NGBD-LAP). In NGBD-D, additional dual information is introduced into the relaxed master problem by solving the relaxed dual of primal problem. The soobtained primal dual cuts can significantly improve the convergence rate of the algorithm. In NGBD-PCR, the piecewise McCormick relaxation technique is integrated into the NGBD algorithm to reduce the gap between the original problem and its convex relaxation. The domains of variables in bilinear functions can be uniformly partitioned before solution or dynamically partitioned in the algorithm by using the intermediate solution information. In NGBD-LAP, lift-and-project cuts are employed for solving the piecewise lower bounding problem. In all three enhanced decomposition algorithms, there is a trade-off between tighter relaxations and more solution times for subproblems. The computational advantages of the enhanced decomposition methods are demonstrated via case studies on the flexible polygeneration problems. The computational results show that, while NGBD can solve problems that are intractable for a state-ofthe- art global optimization solver (BARON), the enhanced NGBD algorithms help to reduce the solution time by up to an order of magnitude compared to NGBD. And enhanced NGBD algorithms solved the large-scale nonconvex MINLPs to [epsilon]-optimality in practical times (e.g., a problem with 70 binary variables and 44136 continuous variables was solved within 19 hours).
by Yang Chen.
Ph.D.

In recent times the problems regarding global warming and climate change have become increasingly relevant in our society. Public attention is growing due to seemingly larger and more severe natural disasters each year and the search for solutions to these problems is greater than ever. Humanity is facing a lot of environmental challenges, but one could argue that the increasing rate of greenhouse gas emissions related to energy production and use is the main focus. This study focuses on how electricity generating and storage technologies can be installed for different types of buildings and businesses to maximize economic benefits and at the same time reduce dependency on grid bought electricity. The buildings in the analysis will have prior solar PV systems installed ranging from 35 kW to 254.8 kW in capacity. Three different buildings within this interval have been chosen and have the solar PV capacity of 35.84 kW, 143.36 kW and 254.8 kW. These buildings have been chosen to get three different load profiles that are as different as possible, given the available data. The study concludes that only using solar PV is the financially most profitable system configuration for all three buildings, rated by maximum IRR. Both wind power and batteries have a negative impact on IRR for all buildings. The building with the least changes in day-to-day peak demand benefited the most from solar PV. Wind power affects the demand in a similar way as solar PV, however batteries added more value to a building with a less consistent load curve.
På senare tid har problemen med global uppvärmning och klimatförändringar blivit alltmer relevanta i vårt samhälle. Allmänhetens uppmärksamhet växer på grund av till synes större och allvarligare naturkatastrofer varje år och sökandet efter lösningar på dessa problem är större än någonsin. Mänskligheten står inför många miljömässiga utmaningar, men det går att hävda att den ökande andelen växthusgasutsläpp relaterade till energiproduktion och användning är huvudfokus. Denna studie fokuserar på hur elproduktionens- och lagringsteknologier kan installeras för olika typer av byggnader och företag för att maximera ekonomiska fördelar och samtidigt minska beroendet av köpt el från elnätet. Byggnaderna i analysen har tidigare installerade solcellsanläggningar som sträcker sig från 35 kW till 254.8 kW. Tre olika byggnader inom detta intervall har valts och för dessa var solenergikapaciteten 35.84 kW, 143.36 kW och 254.8 kW. Dessa byggnader har valts för att få tre olika elförbrukningsprofiler som är så olika som möjligt med tanke på den tillgängliga datan. Studien drar slutsatsen att användningen av endast PV är den ekonomiskt est lönsamma systemkonfigurationen för alla tre byggnader, rankad efter maximal IRR. Både vindkraft och batterier påverkar IRR negativt för alla byggnaderna. Byggnaden med minst förändringar i det dagliga toppbehovet gynnades mest av solceller. Vindkraft påverkar elbehovet på liknande sätt som PV, men batterierna däremot gav mer värde till en byggnad med en förbrukningsprofil som var mindre konsekvent.

The colossal risks and challenges posed by climate change require innovative solutions that must fulfil energy service demands sustainably. The concept of small-scale, biomass-based polygeneration (SBP) is one such technological approach, which optimizes locally supplied fuels to provide several energy services like electricity, heating, cooling, potable water, and/or bio-chemical products. By presenting chosen SBP systems and models employed in various socio-geographic locations, in particular distributed applications, the thesis identifies benefits as well as drawbacks of the SBP concept and aims to promote its wider usage in the field. Because a multitude of technologies can be applied for polygeneration system design, the thesis starts with a thorough review of the highly complex and rapidly evolving field, where relevant literature is presented and assimilated. Based on this review, several models have been created for various solar-assisted SBP systems: Firstly, a small-scale Combined Cooling, Heating, and Power (CCHP) system based on biomass gasification has been investigated for a hotel resort on one of the Andaman Islands, India. Apart from economic and environmental superiority compared to a fossil-fuel reference system, the study also expanded technological aspects by adding a socio-political analysis of the benefits and drawbacks of the system for the entire island community. In the second study, a novel control algorithm was devised for a biogas-based polygeneration system generating electricity and potable water generation for a rural off-grid village in El Pando, Bolivia. It was found that the proposed system could lead to significant cost and emissions reductions paired with greater energy autonomy. In the third study, an optimization model for a combined gasification-based CCHP/Heat Pump (HP) system is presented for a tourist facility in Barcelona considering various climate scenarios. The study reveals that the system design is only slightly affected by future changes in climate and that the CCHP/HP system shows only a moderate economic performance but still considerable CO2-savings potential. The overall findings of these studies reveal that the economic feasibility of SBP systems depends greatly not just on their inherent design but also on their location. However, all proposed polygeneration systems could lower emissions significantly, while excelling in energy efficiency as well as adaptability towards service demands and other technologies. The presented studies contribute to the state of the art by adding innovative polygeneration system designs, proposing new modelling approaches and subsequent models including SBP system enhancing technologies, as well as by investigating the effects of geographical location and climate change on the system design process.
Los colosales riesgos y retos puestos por el cambio climático requieren soluciones creativas para satisfacer las demandas de servicios energéticos de una manera más sostenible, comparado con los sistemas actuales. El concepto de poligeneración a escala pequeña y basada en biomasa (Small-scale, biomass-based polygeneration o SBP) es uno de estos enfoques, que optimiza el uso de combustible locales para proveer varios servicios energéticos como electricidad, calor, enfriamiento, agua potable y/o productos bioquímicos. Presentando una selección de sistemas SBP y modelos empleados en varias localizaciones socio-geográficas, esta tesis identifica los beneficios e inconvenientes del concepto SBP con el objetivo de promover su un uso más amplio en el mundo. Como se puede aplicar una multitud de tecnologías para el diseño de sistemas SBP, la tesis empieza con una revisión profunda del campo, altamente complejo y dinámico, donde la literatura relevante está presentada en una forma estructurada y resumida. Basado en esta revisión, se han creado varios modelos SBP para varios sistemas SBP con asistencia solar: Principalmente, se ha investigado un sistema de generación conjunta de frio, calor y electricidad (en inglés: Combined Cooling, Heating, and Power or CCHP) basado en gasificación de biomasa para un resort (hotelero) en una de las islas Andamán, India. Además de mostrar de una superioridad económica y ambiental comparado con el sistema de referencia de combustibles fósiles, el estudio expandió el conocimiento científico añadiendo un análisis socio-político de los beneficios e inconvenientes del sistema SBP para la comunidad de la isla entera. En el segundo estudio, se ha desarrollado un nuevo algoritmo de control para un sistema de poligeneración basado en biogás, que genera electricidad y agua potable para una comunidad rural y sin conexión a una red eléctrica más grande en el Pando, Bolivia. Se ha revelado que el sistema propuesto podría bajar significantemente los costes y las emisiones junto con un aumento de la autonomía energética. En el tercer estudio se ha presentado un modelo de optimización para un sistema combinado de CCHP y bombas de calor (sistema CCHP/HP), que se considera para una estructura museístico-turística en Barcelona y para varios escenarios climáticos. En el estudio se ha descubierto que el cambio climático influye sólo ligeramente en el diseño del sistema óptimo, y que el sistema CCHP/HP demuestra sólo un moderado desempeño económico, similar al convencional, pero también un potencial considerable para la reducción de emisiones de CO2. El conjunto de los estudios revela que la viabilidad económica de los sistemas SBP depende altamente no solo de su diseño inherente, sino también de su entorno. De todos modos, todos los sistemas SBP propuestos podrían bajar las emisiones significantemente, mientras sobresalen en eficiencia energética y adaptabilidad a servicios energéticos y tecnologías alternativas. Los estudios presentados contribuyen al estado del arte añadiendo diseños innovadores de sistemas SBP, proponiendo nuevos enfoques de modelado y cálculo, y subsecuentemente nuevos modelos incluyendo tecnologías aumentando sistemas SBP, e investigando los efectos de la ubicación geográfica y del cambio climático al proceso del diseño de los sistemas SBP.
Sammanfattning Klimatförändringen bär med sig kolossala risker och utmaningar, som kräver innovativa lösningar för att tillhandahålla energitjänster på ett mer hållbart sätt än med tidigare energisystem. Konceptet med småskaliga, biomassa-baserade polygeneration (SBP) system är ett sådant teknologiskt tillvägagångssätt, vilket optimerar användningen av lokalt producerat bränsle för att tillhandahålla olika energitjänster som elektricitet, värma, kyla, dricksvatten, eller/och bio-kemiska produkter. Doktorsarbetet identifierar för- och nackdelar hos olika SBP konceptet genom att presentera ett urval av SBP system och modeller av dem för olika geografiska regioner, med mål att främja vidare applikation av dem i fält. Eftersom en mängd tekniker kan användas för design av polygenerationssystem, börjar avhandlingen med en grundlig genomgång av det mycket komplexa och snabbt utvecklande området, där relevant litteratur presenteras och assimileras. Baserat på denna recension har flera modeller skapats för olika solassisterade SBP-system: För det första har ett småskaligt kombinerat kyl-, värme- och kraftsystem (CCHP) baserat på biomassaförgasning undersökts för en hotellanläggning på en av Andamanöarna, Indien. Bortsett från ekonomisk och miljömässig överlägsenhet jämfört med ett referenssystem för fossila bränslen har studien även inkluderat tekniska aspekter genom att lägga till en socio-politisk analys av fördelarna och nackdelarna med systemet för hela ö-samhället. I den andra studien utvecklades en ny regleralgoritm för ett biogasbaserat polygenereringssystem som genererar el och renar vatten till dricksvatten för en by utan elförsörjning i El Pando, Bolivia. Det konstaterades att det föreslagna systemet kan leda till betydande kostnads- och utsläppsminskningar i kombination med större energiautonomi. I den tredje studien presenteras en optimeringsmodell för ett kombinerat förgasningsbaserat CCHP / värmepumpsystem (HP) för en turistanläggning i Barcelona under olika klimatscenarier. Studien avslöjar att systemdesignen bara i låg grad påverkas av framtida klimatförändringar och att CCHP / HP-systemet endast visar en måttlig ekonomisk prestanda men fortfarande en betydande potential för CO2-besparingar. De övergripande resultaten av dessa studier visar att den ekonomiska genomförbarheten för SBP-system inte bara beror på deras inneboende design utan också på deras lokalisering. Alla föreslagna SBP-system kan emellertid sänka emissionerna betydligt, samtidigt som de sticker ut i energieffektivitet samt anpassningsbarhet efter energitjänster och annan teknik. De presenterade studierna bidrar till vetenskapen genom att lägga till innovativa SBP-systemdesigner, föreslå nya modelleringsmetoder och efterföljande modeller inklusive SBP-systemförbättrande teknik, samt genom att undersöka effekterna av geografisk plats och klimatförändringar på systemdesignprocessen

The optimal design and operation of an energy supply system is very important for the matching of the energy production and consumption especially in the residential-tertiary sector characterized by an energy demand with a high variability. The main objective of this thesis is to develop an optimisation environment for the preliminary design and analysis of polygeneration plants. The optimisation models are organized in different units represented by blocks that can be connected between each other to create the flowsheet of the polygeneration system. To characterize the energy demand in the residential and tertiary sector a graphic methodology has been developed to select typical energy demand days from a yearly energy demand profile. The environment developed has been applied to two case studies: a small scale polygeneration plant using a liquid desiccant system for air conditioning and a polygeneration plant connected to a district heating and cooling network.

A polygeneration system is a small-scale energy system with multiple components of different technologies. The system consists of generations and storage that is sized and configured to match a specific demand. With these decentralized energy systems, located close to the end user, local energy resources can be used easily. Different technologies for electricity and heat generation and electrical and thermal storage are presented in the report. The objective of this thesis is to describe important aspects of polygeneration in decentralized energy systems. Interactions between environmental, economic and social aspects of life are essential when configuring a sustainable polygeneration system. Also, climate change and low levels of living standards is a driving force to provide better alternatives for energy supply. A case study in a rural village in India has been carried out to model and optimize a polygeneration system for the community. The optimization is made in the software HOMER (Hybrid Optimization of Multiple Energy Resources) with suitable data for different input parameters, resulting in a techno-economic analysis. Additionally, a sensitivity analysis of the system has been performed in order to consider fluctuations of uncertain input parameters. The result from the case study shows an optimized system with 79 % of renewable resources, which consists of solar PVs with a capacity of 50 kW. Moreover, the system includes a diesel generator with the capacity of 20 kW and 40 batteries of 6V each. In theory, a polygeneration system with 100 % of renewable resources would be the most sustainable configuration in regard to the environmental aspect. However, implementing that kind of system in a rural area would not be the most reliable or cost effective alternative for the end users. An implementation of a polygeneration system is indeed a complex process as a result of multiple aspects and energy supply is rarely the only aspect to be considered. The difference between needs in developing and developed countries vary, as the first may prefer to cover basic needs such as electric lighting to a low environmental footprint.
Ett polygenererande system är ett småskaligt energisystem bestående av ett flertal komponenter med olika teknologier. Systemet inkluderar komponenter för energiproduktion samt energilagring vars storlek och sammansättning syftar till att möta en specifik efterfrågan. Med dessa decentraliserade energisystem, placerade nära slutanvändaren, kan lokala energikällor tas till vara. Olika teknologier för el- och värmeproduktion samt elektrisk och termisk lagring beskrivs i rapporten. Syftet med kandidatarbetet är att beskriva viktiga aspekter av decentraliserade polygenererande energisystem. Samverkan mellan de miljömässiga, ekonomiska och sociala aspekterna är avgörande för att skapa ett hållbart polygenererande system. Klimatförändringar och låga nivåer av levnadsstandard är en drivkraft för att skapa bättre alternativ till energiproduktionen. En fallstudie har gjorts i en avlägsen by i Indien för att utforma och optimera ett polygenererande system för ett samhälle. Optimeringen är gjord i datorprogrammet HOMER (Hybrid Optimization of Multiple Energy Resources) med lämplig indata, vilket resulterat i en teknisk och ekonomisk analys. Utöver detta har en känslighetsanalys gjorts som tar hänsyn till fluktuationer i osäkra parametrar. Resultatet från fallstudien visar ett system bestående till 79 % av förnyelsebara energikällor, vilket i detta fall är solpaneler med en kapacitet på 50 kW. Systemet inkluderar även en dieselgenerator med en kapacitet på 20 kW och 40 batterier med 6 V vardera. I teorin är ett system bestående av 100 % förnyelsebar energi det mest hållbara systemet ur ett miljöperspektiv. Ett sådant system i en avlägsen by är dock varken det mest pålitliga eller kostnadseffektiva alternativet för slutanvändaren. Implementeringen av ett polygenererande energisystem är en komplex process eftersom energiförsörjningen sällan är det enda utfallet att beakta. Behoven i utvecklingsländer och industrialiserade länder skiljer sig åt. I utvecklingsländer är grundläggande behov så som elektriskt ljus av större vikt medan en liten miljöpåverkan är allt viktigare i industrialiserade länder.

Climate change is an important topic of today's discussion where scientists have determined that a large proportion of the increasing global temperatures is a product of the increasing greenhouse gases in the atmosphere. Globally it is expected that the share of renewable power generation is set to increase with 50 % between 2019 and 2024. Together with cost reductions and advancements in renewable energy technologies this opens up an opportunity for companies and market actors to reevaluate their power generation systems. By utilising a polygeneration system an energy system is able to combine multiple energy sources to produce several energy services in an efficient, cost effective and sustainable way. This thesis analyses the possibilities of implementing alternative power generation systems for a unit in the Swedish Armed Forces. In close conjunction with the Swedish Armed Forces works The Swedish Defence Material Administration with the primary assignment to procure, develop and deliver equipment and services to the Swedish defence. In this thesis, a Ground Based Air Defence Operations Center is used as a case study which utilises diesel gensets for power generation. The energy system of the unit is analysed as well as the power, heat and cooling demands. Different scenarios based on current and future developments in energy technology are modelled in the microgrid software Homer Pro. The system model 1 for the scenarios BAU, AF1 and AF2 requires no modification of the gensets in the current power generation system. Instead alternative fuel types are modelled where a biodiesel B20 blend is used for AF1 and 1 hydrogenated vegetable oil is used in the AF2 scenario. In the scenarios using the system model 2, FS1 is utilising the current genset upgraded with a heat recovery system running on hydrogenated vegetable oil. The FS2 scenario proposes a microturbine with a capacity of 30 kW as an alternative to the current genset. In the FIFS scenario a PEM fuel cell is modelled, also having a capacity of 30 kW. All of the system model 2 configurations included a battery system, a membrane distiller for water purification and a thermal storage tank as additional units. The main results from the thesis show that all scenarios except for FS2 reduce the annual emissions from the unit. However, this brings a higher net present value for the systems as well as a higher yearly operation cost. The results indicate that the FS1 scenario is able to decrease the CO2 emissions with almost 50 % with adjustments to the current gensets as well as providing the unit with excess heat for water purification and storage in the thermal tank.
Klimatförändringen är ett viktigt ämne idag där forskare har fastställt att en stor andel av ökningen av medeltemperaturen beror på ökade växthusgaser i atmosfären. Globalt förväntas kraftgenerering från förnybara källor att öka med 50 % mellan åren 2019 till 2024. Detta i samband med kostnadsminskningar och framsteg inom förnybara energiteknologier leder till en möjlighet för företag och aktörer att omvärdera sina energisystem. Genom att använda ett polygenereringssystem kan ett energisystem kombinera flera energikällor för att producera fler energitjänster på ett hållbart och kostnadseffektivt sätt. Detta examensarbete undersöker möjligheten att implementera alternativa kraftgenereringssystem för en enhet i Försvarsmakten. I ett nära samarbete med Försvarsmakten arbetar Försvarets Materielverk med det primära uppdraget att upphandla, utveckla och leverera materiel och tjänster till det svenska försvaret. I detta arbete har en luftvärnscentral som nyttjar dieselgeneratorer för kraftproduktion använts som en fallstudie. Enhetens energisystem har analyserats och därtill även el-, värme- och kylbehovet för denna enhet. Olika scenarier baserat på nuvarande och framtida utveckling inom energiteknik har modellerats i microgridprogrammet Homer Pro. För system modellerna 1 i scenarierna BAU, AF1 och AF2 görs inga modifieringar av befintliga system utöver bränsletyp. Scenario AF1 använder en biodieselblandning B20 och i AF2 drivs systemet med vätgasbehandlad växtolja. För modellerna som använder sig utav system modellerna 2 är FS1 ett scenario baserat på en uppgradering av nuvarande kraftenhet genom en värmeåtervinningsenhet. FS2 föreslår en alternativ kraftenhet i form av en mikroturbin med en kapacitet på 30 kW. En PEM-bränslecell är modellerad i scenario FIFS som även den har en kapacitet på 30 kW. Tillhörande komponenter till system modellerna 2 är ett batterisystem, en vattenreningsenhet och en varmvattentank. Resultaten visar att alla scenarier förutom FS2 minskar de årliga utsläppen från enheten. Detta på en bekostnad av en högre nuvärdeskostnad och en högre årlig kostnad för driften av systemen. Från simuleringen visar resultaten även att FS1 kan bidra till att minska utsläppen med nästan 50 % genom justeringar av nuvarande kraftenhet samtidigt som systemet levererar överskottsvärme för vattenrening och lagring i varmvattentanken.

Growing data generation and increasing computational power accelerate the advance of machine learning (ML) as a subsection of artificial intelligence in various sectors, while in Sub-Saharan Africa (SSA) electrification cannot keep up with the pace of population growth. Hence, this study aims to determine how ML can support rural polygeneration minigrids and thus assisting the electrification efforts in SSA in cooperation with the company RVE.Sol. This study focuses on electricity supply and demand balancing, but also discusses other application areas and non-rural context. Within the (micro)grid and energy area, main application areas studied in academia are identified as power and load forecasting, scheduling and sizing. Building on existing works, this thesis proposes a concept aimed at improving the supply and demand mismatch, while discussing further ML applications and generating knowledge transfer to general, non-rural polygeneration systems. The load and generation mismatch and the impact of possible demand response (DR) implementation are quantified, followed by an expert questionnaire to back up machine learning knowledge in the discussed context. Moreover, GHI and PV power predictions are performed to obtain indications about promising features and algorithms. Finally, considering the previous steps a concept for ML supported generation and load matching by DR is proposed. Results indicate that DR could improve the significant mismatch of load and power generation in RVE.Sol’s grids. According to the proposed model, a 30% acceptance rate to the DR scheme results in 56% operational expenditure (OPEX) and approximately 60% CO2 and particulate matter (PM) emissions decline. A sensitivity analysis indicates that acceptance is a critical success factor for a DR scheme. Hence, a DR concept is proposed where load and PV power are forecasted by ML to set 4 different tariff periods 24 h in advance to improve acceptance. The tariff prices could possibly be derived by reinforcement learning. Preliminary PV power forecasting indicates that a random forest algorithm for regression with weather and time related input features is promising due to high accuracy and short training time compared to other algorithms including neural networks. While the proposed scheme has advantages within all three pillars of sustainability, the lack of data as well as small system and load sizes/low complexities remain as two major impediments for ML in rural polygeneration systems. Thus, ML likely bares better applicability in the urban and developed context, where data availability is higher and loads are more diverse.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
A geração de energia distribuída em edificações e cidades tem sido proposta como uma importante alternativa para que os países ampliem a base tecnológica de suas matrizes energéticas. No caso do Brasil, a possibilidade da incorporação da geração distribuída em edificações apresenta amparo legal por meio de recentes regulamentações do setor elétrico e das normas de melhoria da eficiência energética de edificações. Por estas razões, novos empreendimentos imobiliários com visão de sustentabilidade ambiental, estão avaliando o uso da geração distribuída na etapa de planejamento. Nesta dissertação, foi analisada uma proposta para atender as necessidades energéticas de um hospital (vapor, água quente, resfriamento e eletricidade) considerando as informações de demanda, classificadas em oito dias típicos do ano, dois por cada estação do ano (outono, inverno, primavera e verão) sendo um dia de trabalho normal e outro de final de semana. A proposta consiste na otimização de uma superestrutura composta de diferentes tecnologias de geração e cogeração incluindo equipamentos solares, para assim obter a melhor configuração em termos econômicos. A superestrutura é flexível, ou seja, permite a venda ou compra de eletricidade e analisa três casos, verificando-se a viabilidade de gerar mais eletricidade. Finalmente são apresentados os resultados da configuração final obtida pela otimização.
Distributed generation in buildings and cities has been proposed as an important option for countries in order to include more technologies in their energy mixes. In Brazil, the possibility of including distributed generation in buildings has recent advances in energy policy and building energy efficiency standards. For these reasons, new construction projects of sustainable buildings include the assessment of distributed generation in the initial stages. In this work, we present an approach for attending energy needs (steam, hot water, cooling and electricity) of a hospital. The information about demand is classified in eight typical days, two for each season of the year (autumn, winter, spring and summer); a workday and a weekend day. The approach consists in the optimization of a superstructure containing different energy generation and cogeneration technologies like solar panels, for obtaining the best configuration in economic terms. The superstructure is flexible, this is, it allows buying or selling electricity. It also analyzes three cases, verifying the feasibility for generating more electricity. Finally, the results present the final configuration obtained from the optimization process.

This study explores the application of micro-CCHP systems that utilize a 30 kW gas microturbine and an absorption chiller. Engineering Equation Solver (EES) is used to model a novel single-effect and double-effect water-lithium bromide absorption chiller that integrates the heat recovery unit and cooling tower of a conventional CCHP system into the chiller’s design, reducing the cost and footprint of the system. The results of the EES model are used to perform heat and material balances for the micro-CCHP systems employing the novel integrated chillers, and energy budgets for these systems are developed. While the thermal performance of existing CCHP systems range from 50-70%, the resulting thermal performance of the new systems in this study can double those previously documented. The size of the new system can be significantly reduced to less than one third the size of the existing system.

Most energy solutions in developing countries focus primarily on solving domestic energy demands of their growing populations without due consideration of sustainable development. On the other hand, in most of these countries, a segment of energy users that has not received enough attention from governments and institutions regarding appropriate energy solutions is the productive sector. This sector is mainly composed by small and medium-sized industries and ventures that greatly contribute to the countries’ economy, as in the case of Bolivia. However, the low investment capacity, the lack of knowledge, training and insufficient support from local and national governments do not allow these solutions to arrive as expected. Although many of these sectors have the potential to apply energy solutions utilizing alternative energy sources, as the waste generated by the activity, this work has not materialized. This is the case of the dairy farmers in central Bolivia, who do not have an adequate management of farm waste. This problem contributes negatively to the contamination of the local and global environment.  This study explores solutions of combined energy systems applied to the dairy sector of Bolivia. The two cases under investigation consider the utilization of waste from farms to produce biogas, which drives the proposed systems. The first solution focuses on a polygeneration system featuring either an internal combustion engine or internally fired microturbine for the simultaneous provision of biogas for cooking, electricity, refrigeration, and fertilizer. The second system involves trigeneration i.e. absorption chiller integrated to an externally fired microturbine for supplying electricity, refrigeration and hot water. Analysis methods include determination of levelized cost of services, payback period, primary energy rates and energy saving rates.  The techno-economic assessment for the polygeneration system shows that the costs of the supplied services are still attractive when compared to subsidized prices of fossil fuel-based services in the market if the investment capital of this system is partially subsidized. The biogas cost from the system is lower than the cost of conventional gas used for cooking. The use of the internal combustion engine results in a lower electricity cost than using the microturbine. The refrigeration cost is slightly higher than conventional refrigeration for both cases. A sensitivity analysis shows that the cost for feedstock (cow dung) can be increased while maintaining an attractive price of biogas, and that subsidies on investment capital cause a reduction in the services costs. In the case of energy performance evaluation of the trigeneration system it was found to be more efficient in terms of energy utilization than conventional fossil fuel-based solutions, and this leads to energy savings.  Finally, it is shown that combined energy systems applied to the Bolivian dairy sector are competitive in terms of their economic feasibility and energy performance.
De flesta energilösningar i utvecklingsländer fokuserar på att lösa inhemska energibehov för sina växande populationer utan att ta hänsyn till hållbar utveckling. Å andra sidan är ett segment av energianvändare den produktiva sektorn, som inte fått tillräckligt med uppmärksamhet från regeringar och institutioner när det gäller lämpliga energilösningar. Denna sektor består huvudsakligen av små och medelstora industrier och företag som i hög grad bidrar till ländernas ekonomi, vilket är fallet med Bolivia. Låg investeringskapacitet, brist på kunskap, utbildning och otillräckligt stöd från lokala och nationella regeringar tillåter dock inte att dessa lösningar kommer fram som förväntat. Även om många av dessa sektorer har potential att tillämpa energilösningar som använder alternativa energikällor, som det avfall som genereras av verksamheten, har detta inte exploaterats i nämnvärd grad. Detta gäller bland annat mjölkbönderna i centrala Bolivia, som inte har en adekvat hantering av jordbruksavfal, vilket bidrar negativt till föroreningar av den lokala och globala miljön. Denna studie undersöker lösningar med kombinerade energisystem för mjölkhantering i Bolivia. De två fall som undersöks gäller användningen av avfall från gårdar för att producera biogas, som driver de föreslagna systemen. Den första lösningen fokuserar på ett polygenerationssystem som innehåller antingen en förbränningsmotor eller mikroturbin med klassisk intern förbränning. Systemet möjliggör samtidig försörjning av biogas för matlagning och elgenerering, bl.a. för kylning samt ger gödningsmedel som restprodukt. Det andra systemet innefattar tri-gereration, dvs en absorptionskylare integrerad med en externt driven mikroturbin för att leverera el, kylning och varmt vatten. Analysmetoder innefattar bestämning av driftkostnader för de olika energitjänsterna, återbetalningsperiod, förbrukad primärenergi och relativ energibesparing. En teknisk-ekonomisk analys av polygenerationssystemet visar att kostnaderna för de tillhandahållna tjänsterna är attraktiva i förhållande till de subventionerade priserna på tjänster på marknaden om subventioner tillämpas på investeringskapitalet. Kostnaden för biogas från systemet är lägre än kostnaden för konventionell gas som används för matlagning. Användning av en förbränningsmotor resulterar i en lägre elkostnad än att använda en mikroturbin. Kylkostnaden är något högre än med konventionell kylning för båda fallen. En känslighetsanalys visar att kostnaden för råvaror (kogödsel) kan tillåtas öka, samtidigt som ett attraktivt biogaspris bibehålls, och att subventioner på investeringskapital leder till en minskning av kostnaderna för energitjänsterna. När det gäller utvärdering av energiprestanda för tri-gererationssystemet visade sig det vara mer effektivt när det gäller energianvändning än konventionella lösningar baserade på fossila bränslen, vilket leder till energibesparingar. Slutligen visas att kombinerade energisystem som tillämpas på mjölkhanteringssektorn är konkurrenskraftiga när det gäller den ekonomiska genomförbarheten och energiprestanda.

I ett modernt samhälle är elektricitet en nyckelkomponent för industrins, individens och samhällets utveckling. Naturkatastrofområden där elektriciteten slagits ut står inför stora prövningar för att kunna få samhällsviktiga funktioner att fungera igen. Med hjälp av den mobila miljövänlig energienhet Emergency Energy Module (EEM) kan elbehovet lindras. Detta examensarbetes mål var att ta fram en elsystemsbeskrivning för den kommande Export container (EXC), samt ta fram ett korrekt elschema för den befintliga EEM. Elsystemsbeskrivningen måste ta hänsyn till EXC:s kravspecifikation samt innehålla Bills of Material (BoM) och elschema. Problematiken ligger bl.a. i att få flera olika energikällor (sol, vind och biomassa förgasare) att fungera tillsammans i ett elsystem där likspänning, växelspänning, trefas och enfas blandas. Stor vikt ligger också vid att få ett flexibelt elsystem som relativt lätt kan förändras efter olika kunders behov. Genomförandet av detta examensarbete utfördes inledningsvis med en faktainsamligs-fas. Detta efterföljdes av en genomgång och analys av EEM:s elsystem vilket resulterade i ett elschema och en manual. Svagheter i EEM:s elsystem ansågs vara avsaknaden av överspänningsskydd och jordfelsbrytare, mätpunkt 5 var felplacerad, mätutrustningen borde av säkerhetsskäl vara fastmonterade och 1-fas generator borde användas i biomassaförgasaren för att avlägsna snedbelastningsproblem. Den befintliga Power routern, vars uppgift är att kontrollera energiflöde i systemet, ansågs begränsad eftersom den endast kunde ta emot en AC-energikälla, endast hantera 1-fas samt hade en relativt låg max uteffekt på 5,5 kW. Med hjälp av analysens funna svagheter och med hänsyn till EXC:s kravspecifikation konstruerades sedan ett elsystem för EXC med tillhörande BoM, elschema, kravspecifikation avseende delsystem och förslag på kandidater som uppfyller dessa. Elsystemet rekommenderas byggas kring Power routern Quattro vilket ger stora möjligheter till flexibilitet i form av att kunna skala upp systemet om bl.a. mer effekt skulle önskas av kund, eller om det finns behov av 3-fas system. En mängd olika programmeringsinställningar kan då göras vilket underlättar uppbyggnaden av specifika elsystem efter varierande kunders behov.
In a modern society electricity is a key component for the development of the individual, industry, and society. Natural disaster areas where the electricity has been knocked out face great trials in order to get vital public functions working again. With the help of the mobile eco-friendly energy device Emergency Energy Module (EEM) electricity needs can be eased. The goal of thesis was to produce an electrical power system description for the upcoming Export container (EXC), and to generate a correct circuit diagram for the existing Emergency energy module (EEM). The electric power description must take into account EXC's specifications and include Bills of Material (BoM) and circuit diagram. The problems lies in getting the various sources of energy (solar, wind and biomass gasifier) to work together in a power system where DC, AC, three-phase and single-phase are mixed. Great emphasis is also given to obtain a flexible electricity systems that can be relatively easily changed for different customer needs. The making of this thesis was carried out initially with a gathering facts phase. This was followed by a review and analysis of the EEM's electrical system which resulted in a circuit diagram and a manual. Weaknesses in EEM's electrical system was considered to be the lack of overvoltage protection and residual current device, measuring point 5 was misplaced, measuring equipment should for safety reasons be firmly attached and 1-phase generator should be used in biomass gasifier to remove uneven load problems. The existing Power router, whose task is to control the energy flow in the system, was limited because it could only receive one AC power source, handle only one-phase and had a relatively low maximum output power of 5.5 kW. Whit the help of the analysis improvement suggestions above and with EXC's specification taking into account was then an electric power system for EXC constructed. with associated BoM, circuit diagram, specifications for subsystems and proposals for candidates that meet these. The electrical system is recommended to be built around the Power router Quattro which provides great opportunities for flexibility in terms of being able to scale up the system if such more power would be desired by the customer, or if there is a need for 3-phase systems. A variety of programming settings can then be made which facilitates the construction of specific electrical systems for varying customer needs.

Due to the recent development of small-scale energy technologies, the energy industry is changing from a centralized to a more decentralized energy system. And because of the current problems with limited energy sources it is now important to focus on renewable energy sources and how to store the energy for later use. One solution is polygeneration system. A Polygeneration energy system is a system that combines heat, cold and power generation. Therefor it is a flexible system that can easily be modified depending on the size of the system, its application, the demands and other requirements. This project focuses on mapping different types of energy storage and the important parameters in each method. Initially the different concepts of energy storing will be described thoroughly so the reader gets an overview of the different storing methods. Thereafter the report maps the different methods and how developed they are via TRL (Technology Readiness Level). To achieve a greater knowledge of how a polygeneration systems is built and optimized, , an optimization tool can be used. One of these programs is HOMER. HOMER will be used in this project to create a wider comprehension about optimization and effects of energy storage in a polygeneration system. By using different data, the program can calculate the profit, from an economic and a geographical perspective. The demarcation has been selected by choosing a geographical area and what sorts of resources that are available in relation to it. Since the main purpose with the report consists of defining ways to store energy, the focus will be on the different battery types that exist today. A comparison between three different types of batteries will be done and further on what results they will show. The optimization in HOMER showed that it is possible to build a decentralized polygeneration system on the chosen location, Sagar Island. The system combines different renewable energy resources such as, solar and wind together with a generator, converter and batteries to create a sustainable system. The results showed a high investment cost for the energy system in all cases, despite the use of different battery types. However, the investment is profitable for the population on Sagar Island to have access to electricity and what future benefits that may provide.
På grund av den senaste utveckling av småskaliga energisystem, där energiindustrin går från ett centrerat till ett mer decentraliserat system och bristerna som finns i samband med energikällor, är därför nu viktigt att fokusera på förnybara energikällor och hur denna energi kan lagras. En lösning till detta är polygenerationsystem. Ett polygenerationsystem bygger på ett system som kombinerar värme, kylning och effektutveckling. Därigenom är det ett flexibelt system som kan modifieras beroende på systemets storlek, efterfrågan och krav. Denna rapport fokuserar på att kartlägga olika typer av energilagring och deras viktiga parametrar. Inledningsvis beskrivs de olika energilagringskoncepten grundligt sådan att läsaren får en överblick av de olika lagringsmetoderna. Därefter kartlägger rapporten de olika metoderna samt hur utvecklade de är genom TRL (Technology Readiness Level). För att få en bättre översikt över hur ett polygenerationsystem är uppbyggt samt dess funktion kan ett optimeringsprogram användas. Ett av dessa program är HOMER. HOMER kommer att användas i denna undersökning för att skapa en bredare förståelse över hur man kan optimera ett polygenerationsystem. Med hjälp av olika indata kan programmet räkna ut systemets vinst, bland annat utifrån ett ekonomiskt samt geografiskt perspektiv. Avgränsningen har valts genom att välja ett geografiskt område samt vilka resurser som finns tillgängliga i anknytning till detta. Eftersom huvudsyftet med rapporten handlar om de olika lagringsmetoderna kommer fokus främst ligga på batterierna, där en jämförelse mellan tre olika batterityper görs och vilka resultat de medför. Optimeringen i HOMER visade att det är möjligt att konstruera ett decentraliserat polygeneration system på den valda platsen, Sagar Island. Systemet kombinerar olika förnybara energikällor så som, sol och vind tillsammans med en generator, omvandlare och batterier för att skapa ett hållbart system. Resultatet visade en hög investeringskostnad för energisystemet i alla fallen, trots användandet av olika batterityper. Emellertid är investeringen lönsam för populationen på Sagar Island att få tillgång till elektricitet och de framtida fördelar som det kan medföra.

In a world where energy consumption increases every year and the current system harms the environment, new technologies are necessary to cope with such intensive energy demands worldwide. In such an era, polygeneration systems are an innovative and sustainable solution for that problem. Polygeneration systems can simultaneously produce electricity, heating, cooling, hot water, potable water, and other services in smaller, more flexible, and more efficient ways. Small-scale polygeneration systems can also help with the decentralization of energy generation and with promoting the use of more renewable energy sources in the power generation sector. In this study, a polygeneration system is proposed for an ecohotel in the Guanacaste region of Costa Rica. The ecohotel demand as well as the availability of local renewable energy resources were studied to size the components of the system correctly. The small-scale polygeneration system consists of a biomass gasifier and an internal combustion engine as prime mover, as well as PV panels, batteries, a biomass boiler, an absorption chiller, and a membrane distillation system. The outputs obtained from the system and to be used in the hotel are electricity, cooling, hot water, and potable water. The results obtained were positive from an economic and environmental perspective when compared to the national grid electricity system. The economic savings are of $410,268 per the system lifetime of 25 years, which represents a 27% margin difference. As for the emissions, 14.4 tons of CO2 are saved every year from going into the atmosphere which represents a 38% yearly reduction. The results shown in this study reflect that the polygeneration systems are of great interest in order to shift to a more sustainable and efficient energy system. This study can be replicated by other hotels in Costa Rica taking into consideration the natural resources present in the local surroundings and adjusting the system to those resources available.
I en värld där energiförbrukningen ökar varje år och det nuvarande systemet skadar miljön, är ny teknik nödvändig för att klara sådana intensiva energibehov över hela världen. I en sådan tid är polygenerationssystem en innovativ och hållbar lösning för det problemet. Polygenerationssystem kan samtidigt producera el, värme, kylning, varmt vatten, dricksvatten och andra tjänster på mindre, mer flexibla och effektivare sätt. Småskaliga polygenerationssystem kan också hjälpa till att decentralisera energiproduktionen och främja användningen av mer förnybara energikällor inom kraftproduktionssektorn. I denna studie föreslås ett polygenerationssystem för ett ekohotel i Guanacaste-regionen i Costa Rica. Ekohotelbehovet och tillgängligheten för lokala förnybara energikällor studerades för att dimensionera systemkomponenterna korrekt. Det småskaliga polygenerationssystemet består av en biomassaförgasare och en förbränningsmotor, liksom PV-paneler, batterier, en biobränslepanna, en absorptionskylare och ett membrandestillationssystem. Energiflödena från systemet, vilka ska användas på hotellet är el, kylning, varmt vatten och dricksvatten. Resultaten är positiva ur ett ekonomiskt och miljömässigt perspektiv jämfört med det nationella elnätet. De ekonomiska besparingarna uppgår till 410 268 USD under en systemlivslängd på 25 år, vilket motsvarar en marginalskillnad på 27%. När det gäller utsläppen sparas 14,4 ton koldioxid varje år från att nå atmosfären, vilket motsvarar en minskning på 38% per år. Resultaten som visas i denna studie återspeglar att polygenerationssystemen är av stort intresse för att övergå till ett mer hållbart och effektivt energisystem. Denna studie kan replikeras för andra hotell i Costa Rica med beaktande av de naturresurser som finns i de lokala omgivningarna och med anpassning av systemet till de tillgängliga resurserna.

This project has addressed the design of a cost-effective Polygeneration system that guarantees a continuous, equitable and environmentally friendly energy supply for the rural settlement of Filipinas ETCR, (in Spanish, Espacios Territoriales de Capacitación y Reincorporación) Colombia, which is currently not achieved, due to a system that relies on the national electricity grid (with numerous outages) and on LPG (Liquefied Petroleum Gas) and wood to meet the thermal demand, mainly for cooking. For this purpose, in addition to the current energy supply situation, the energy demand according to type (electricity and heat) and sector (residential, commercial and agro-livestock) is characterized. Also, the availability of renewable energy sources is examined, resulting in the existence of a potential for solar and residual biomass resources. Then, the most suitable sub-systems and technologies for their exploitation have been analyzed. In this way, HOMER Pro software has been used to find the most competitive solution (the lowest LCOE, Levelized Cost of Energy), together with a technical, economic, environmental and social analysis to analyze its impact on the ETCR. Thus, the final solution results in a Polygeneration system based on a PV (Photovoltaic) subsystem, the electrical grid and a biogas production plant (48 m3/day) by anaerobic digestion of agricultural, livestock and urban waste biomass coupled with an ICE (Internal Combustion Engine). The PV (250 kW) would be the major source of electricity generation, followed by the grid and, as a back-up, the biogas-fired ICE (25 kW), which is also used to replace LPG and wood for heating purposes. The solution presents a remarkable renewable fraction (73% instead of the current <0.5%) and a significant reduction of polluting emissions (60.5% of CO2 emissions). Moreover, it is ensured an economic viability over time (a ROI of 9.7% and DPB (Discounted Pay-Back) lower than 18 years) and a potential positive impact in the socio-economic development of Filipinas ETCR. To conclude, these results are in line with the UN SDGs (Sustainable Development Goals) 7 and 13, being an example of the viability of such systems and the positive environmental, social and economic consequences they can have in rural locations with economic difficulties and non-renewable and weak energy supplies.
Detta projekt har behandlat utformningen av ett kostnadseffektivt polygenereringssystem som garanterar en kontinuerlig, rättvis och miljövänlig energiförsörjning för bosättningen på landsbygden i Filipinas ETCR (Espacios Territoriales de Capacitación y Reincorporación på spanska) i Colombia, vilket för närvarande inte är uppnått på grund av ett existerande energisystem som är beroende av det nationella elnätet (med många avbrott) och av gasol och ved för att tillgodose det termiska behovet, främst för matlagning. I detta syfte har man förutom den nuvarande energiförsörjningssituationen även karakteriserat efterfrågan på energi efter typ (el och värme) och sektor (bostäder, handel och jordbruk och boskapsskötsel). Dessutom undersöks tillgången på förnybara energikällor, vilket påvisar att det finns potential för både solenergi och biomassa. Därefter har man analyserat lämpliga delsystem och tekniker för att kunna nyttja energikällorna. För detta har programmet HOMER Pro använts till att hitta den mest konkurrenskraftiga lösningen (med lägst LCOE), tillsammans med en teknisk, ekonomisk, miljömässig och social analys för att analysera dess inverkan på ETCR. Således är den slutliga lösningen ett system för polygenerering som bygger på ett delsystem av solceller, elnätet och en biogasproduktionsanläggning (48 m3/dag) som använder sig av anaerob nedbrytning av biomassa från både jordbruk, boskap och stadsavfall i kombination med en ICE. Solcellerna (250 kW) skulle då vara den främsta källan till elproduktion följt av elnätet, varav den biogaseldade ICE-anläggningen (25 kW) används som reserv och för att ersätta gasol och ved för uppvärmning. Lösningen innebär en anmärkningsvärd andel förnybara energikällor (73% jämfört med nuvarande <0,5%) och en signifikant minskning av förorenande utsläpp (60,5% av koldioxidutsläppen). Dessutom garanteras en ekonomisk lönsamhet med tiden (med en ROI på 9,7 % och en DPB på mindre än 18 år) och en potentiellt positiv inverkan på den socioekonomiska utvecklingen i Filipinas ETCR. Sammanfattningsvis ligger dessa resultat i linje med mål 7 och 13 av FN:s hållbarhetsmål, eftersom de är ett exempel på lönsamheten hos sådana system och de positiva miljömässiga, sociala och ekonomiska konsekvenser som de kan få på landsbygden där det förekommer ekonomiska svårigheter, och där eltillförseln är opålitlig och baserad på energikällor som inte är förnybara.

The polygeneration is an innovative and sustainable solution which has become an attractive concept. The simultaneous production of electricity, heating and cooling including hot and cold water respectively in autonomous smaller energy systems can manage a more flexible and environmentally friendly system. Furthermore distributed generation and micro scale polygeneration systems can perform the increase of the utilized renewable energy sources in the power generation. The aforementioned energy systems can consist of several power generation units however the low emission levels, the low investment costs and the fuel flexibility of microturbines are some of the reasons that the study of the microturbines in polygeneration systems is a crucial necessity. In this study, an autonomous small-scale polygeneration energy system is investigated and each component is analyzed. The components of the system are a microturbine, a heat recovery boiler, a heat storage system and an absorption chiller. The purpose of this work is the development of a dynamic model in Matlab/Simulink and the simulation of this system, aiming to define the reliability of the model and understand better the behavior of such a system. Special focus is given to the model of the microturbine due to the complexity and the control methods of this system. The dynamic model is mainly based on thermodynamic equations and the control systems of the microturbine on previous research works. The system has as a first priority the electricity supply while thermal load is supplied depending on the electric demand. The thermal load is supplied by hot water due to the heat recovery which takes place at the heat recovery boiler from the flue gases of the microturbine. Additionally the design of the system is investigated and an operational strategy is defined in order to ensure the efficient operation of the system. For this reason, after creating the load curves for a specific load, two different cases are simulated and a discussion is done about the simulation results and the future work.

This project concentrates on the energy flows of Klintehamn and examines if it is possible for Klintehamn to be self-sufficient in the future. To reach this goal, the energy flows in Klintehamn must be analyzed. Subsequently, a new improved energy flow has been designed, where other renewable energy sources are included. Klintehamn is an urban area on the Swedish island of Gotland. An industrial park is established in the harbour of Klintehamn, and currently a sawmill, a fodder production facility and a few wind turbines are located in the area. A program, Program Klintehamn 2030, outlines opportunities to develop Klintehamn in many areas. The goals for Klintehamn are to increase the use of renewable energy sources and decrease greenhouse gas emissions. More specifically, this includes building a biogas plant by evolving the already established sewage treatment plant, and increasing the use of renewable energy sources such as wind and solar energy. Models of the Current Energy System and the Improved Energy System have been designed during the project. Calculations of the Current Energy System have been made and for the Improved Energy System, seven scenarios have been constructed. The calculations program, Matlab, has been used for all calculations. The following scenarios have been modeled in this project: • Scenario 1 - Development of biogas • Scenario 2 - Increased wind power • Scenario 3 - Development of solar park • Scenario 4 - Development of solar panels • Scenario 5 - Combination 1, scenario 1-4 added into one system • Scenario 6 - Combination 2, 100% renewable energy • Scenario 7 - Combination 3, development of Scenario 5, with more renewable energy In the Current Energy System, the total yearly energy demand is 3.423 TWh, where 3.405 TWh is electricity and 18.2 GWh is heat. The future demand of electricity and heat will be 3.407 TWh and 265 GWh per year, respectively. Scenario 5 is the first combined scenario, where the current energy and all renewable energy sources are included. The generated electricity in that scenario is not enough to satisfy the electricity demand. Scenario 6 consists of 100% renewable energy sources. To achieve the energy demand of Klintehamn all the renewable energy sources have been maximized in order to become self-sufficient. It generated an absurd result, which was far from realistic. Scenario 7 is an expansion of Scenario 5 but with more renewable energy. All energy sources have been expanded and Scenario 7 generates 108 GWh of electricity. Scenario 5 and Scenario 7 are two reasonable scenarios with reasonable amounts of renewable energy installed, but with different levels of ambition. The conclusion of the project is that, it is possible to improve the current energy system. The energy system can become more sustainable and fossil energy sources can be removed and replaced by renewable energy sources. In order for Klintehamn to be self-sufficient, more energy sources must be included, for example wave power.
Det här projektet handlar om energiflödet i Klintehamn och hur Klintehamn i framtiden ska kunna bli självförsörjande. För att kunna göra detta måste dagslägets energiflöde i Klintehamn utvärderas. Därefter har ett nytt förbättrat energiflöde konstruerats, där andra förnybara energikällor är inkluderade. Klintehamn är en tätort på den svenska ön Gotland. En industripark är etablerad i Klintehamns hamnområde, och för närvarande är ett sågverk, en foderproduktionsanläggning samt ett fåtal vindkraftverk befintliga i området. Ett program, Program Klintehamn 2030, har tagits fram, då det finns möjligheter att utveckla Klintehamn på många områden. Mål, för att Klintehamn ska ¨oka användande av förnyelsebar energi och sänka sina koldioxidutsläpp i framtiden, har utvecklats. Några specifika mål är att det ska byggas en biogasanläggning i anknytning till det befintliga reningsverket, samt att utöka användningen av förnybara energikällor så som vind och solenergi. Modeller på dagens energisystem och ett utvecklat energisystem i framtiden har konstruerats under projektets gång. Därefter har beräkningar av dagens energisystem gjorts och för framtida systemet har ett antal scenarion byggts upp och beräknats på. Alla beräkningar har gjorts med hjälp av beräkningsprogramet Matlab. Scenariona i detta projekt är följande:  • Scenario 1 - Utveckling av biogas • Scanario 2 - Utökning av vindkraften • Scenario 3 - Utveckling av solpark • Scenario 4 - Utveckling av solpaneler • Scenario 5 - Kombination 1, scenario 1-4 adderat till ett system • Scenario 6 - Kombination 2, 100% förnybar energi • Scenario 7 - Kombination 3, utveckling av Scenario 5, med mer förnyelsebar energi I det nuvarande energisystemet är den totala årliga efterfrågan av energi 3.423 TWh, varav 3.405 TWh ¨ar elektricitet och 18.2 GWh är värme. Den framtida efterfrågan av electricitet och värme kommer vara 3.407 TWh respektive 265 GWh per år. Scenario 5 är det första kombinerade scenariot, där alla förnybara energikällor är inkluderade. Den genererade elektriciteten i det scenariot är inte tillräcklig för att nå efterfrågan. Scenario 6 består av 100% förnybara energikällor. För att uppnå Klintehamns energibehov har alla förnybara energikällor maximerats för att kunna bli självförsörjande. Det genererade ett absurt resultat, som var långt från rimligt. Scenario 7 är en påbyggnad av Scenario 5, med ännu mer förnyelsebar energi. Alla energikällor har utökats och Scenario 7 genererar 108 GWh elektricitet. Scenario 5 och Scenario 7 är två rimliga scenarion med rimliga mängder förnybara energikällor installerade, men med olika ambitionsnivåer. Så slutsatsen av projektet är att det går att förbättra det nuvarande energisystemet. Energisystemet kan bli mer hållbart och fossila energikällor kan fasas ut och i stor utsträckning ersättas med förnybara energikällor. För att Klintehamn ska kunna bli självförsörjande måste fler energikällor inkluderas, till exempel vågkraft.

Modelling Polygeneration with Desiccant Cooling System for Tropical(and Sub Tropical) ClimatesAbstractSpace cooling has become a necessity in tropical countries. Maintainingcomfortable indoor conditions in industrial environments incur high energy bills due toheavy dependency on electrically operated air conditioning systems. In order to exploreways and means to improve the energy efficiency and alternative energy resources, afeasibility study was conducted using a transient simulation software TRNSYS toimplement a combined cooling, heating and power system suitable for a tropicalcountry.It is proven from the literature search that desiccant dehumidification inconjunction with evaporative coolers can reduce air conditioning operating costssignificantly since the energy required to power a desiccant cooling system is small andthe source of this required energy can be diverse.(Low exergy heat such as solar, wasteheat and natural gas)This research is conducted to evaluate the performance and applicability ofdesiccant cooling systems under tropical climatic conditions. Two operating modes;ventilation and recirculation modes of solid desiccants based open cycle air conditioningthat use waste heat from a CHP plant are analysed to understand their operatingranges, performances and applicability. The model developed is used to propose asuitable desiccant cooling system for a selected industry environment in Sri Lanka.Preliminary results obtained by a parametric analysis for weather data for Colombo, SriLanka shows 0.95 and 1.02 optimum coefficients of performance for the ventilation andrecirculation modes respectively when heat is available at 85°C. Based on thecomparisons of the analysis it is seen that the desiccant cooling appears to be a logicalsupplement for space cooling applications in tropical climates like Sri Lanka. And for thecase study taken to investigate can be proposed with a desiccant cooling system with ahot water storage as the energy supply and it can maintain a COP of about 0.48 undertropical weather conditions.

Polygeneration systems attract attention recently because of their high efficiency and low emission compare to the conventional power generation technology. Three different polygeneration systems based on low temperature solid oxide fuel cell, atmospheric solid oxide fuel cell/ micro gas turbine, and pressurized solid oxide fuel cell/ micro gas turbine are mathematically modeled in this study using MATLAB (version 7.12.0.635). These systems are designed to provide space heating, cooling and hot domestic water simultaneously. This report provides the design aspects of such systems. Furthermore, the effects of some important operating properties on the polygeneration systems performance are investigated.

With environmental concerns, alternative solutions for generating electricity while decreasing the consumption of fossil fuels have gained a great importance. Polygeneration is one of these solutions which is also capable to increase the technical performance of electricity generation. Polygeneration systems are available in large scale, medium scale and small scale. This study focuses on small scale polygeneration systems specifically for residential applications. Type and size of the components and the system’s operational strategy plays a significant role in polygeneration system design as these factors affect the system cost and also environmental impacts. This study aims to propose a guide for component selection, sizing and addressing a suitable operational strategy for a predefined system configuration.Decision criteria is defined for component selection by a comprehensive literature review. Internal combustion engines, Stirling engines, micro gas turbines and fuel cells are investigated within these criteria. This provides the user an insight on component selection. When combined with factors such as market conditions, location and especially household demand profile, a selection can easily be made by the customer. For component sizing and operational strategy, a model has been implemented in Matlab. A baseline case model with a predefined system configuration and operational strategy was defined. The baseline case system includes a prime mover, a back-up auxiliary boiler, a vapor compression refrigeration chiller, a thermal energy storage and solar thermal collectors for the domestic hot water demand. The operational strategy is defined as thermal load following. For the case study, this model was altered for different cases with alterations on the operational strategy and the system configuration in order to identify the optimal solution for the user where the total annual cost is minimized while satisfying all kinds of end-use demands of a single-family household in Ankara, Turkey. The results also give insights on the effect of having solar thermal collectors and a thermal energy storage coupled with a CHP unit on the overall system.
Med hänsyn till miljön har alternativa lösningar för att generera elektricitet och samtidigt minska förbrukningen av fossila bränslen fått en stor betydelse. Polygenerering är en av dessa lösningar som också är kapabel att öka dent tekniska prestandan av elproduktionen. System för sådan kombinerad produktion är tillgängliga i sto, medelstor och liten skala. Denna studie fokuserar på småskaliga polygenereringssystem, speciellt för bostäder. Typ och storlek på komponenterna och driftstrategin för systemet spelar en viktig roll vid designav polygenereringssystem eftersom dessa faktorer påverkar systemkostnaden och även har miljöpåverkan. Denna studie syftar till att vara en guide för komponentval, dimensionering och beskriva en lämplig operativ strategi för en fördefinierad systemkonfiguration.Beslutskriterier definieras för komponentval genom en omfattande litteraturöversikt. Förbränningsmotorer, stirlingmotorer, mikro gasturbiner och bränsleceller undersöks med avseende på dessa kriterier. Detta ger användaren en insikt i komponentval. I kombination med faktorer som marknadsförhållanden, plats och i synnerhet hushållens efterfrågeprofil, kan ett urval enkelt göras av kunden. För komponentdimensionering och operativ strategi, har en modell utvecklats i Matlab. Ett referenssystem med en fördefinierad systemkonfiguration och operativ strategi definierades och modellerades. Referenssystemet innefattar en drivmotor, en reservpanna (backup), ett kompressordrivet kylaggregat, ett termiskt energilager och solfångare för det egna varmvattenbehovet. Driftstrategin definieras att följa behovet av termisk energi. För fallstudien ändrades denna modell för olika driftfall med avseende på den operativa strategin och systemkonfiguration, för att identifiera den optimala lösningen för användaren där den totala årliga kostnaden minimeras samtidigt som det uppfyller alla typer av slutanvändarkrav på en enfamiljs-hushåll i Ankara, Turkiet. Resultaten ger också insikter om effekten av att ha solfångare och en termisk energilagring i kombination med en CHP-enhet på det övergripande systemet.

Polygeneration technology is to utilize a single plant to offer multiple energy products, and the multiple processes are integrated into one system. In comparison with the single-product technology, polygeneration improves the system efficiency significantly since it has multiple outputs, and reduces the relevant capital and production cost accordingly. In this thesis, a polygeneration system was designed specifically for a project in construction industry and the business feasibility of the system was analyzed. The status quo and problems of present temporary power system were introduced and the idea of using polygeneration system as the substitute was described. A substation project in Al Kharj, Saudi Arabia was utilized as the reference to design the polygeneration system and to analyze the system’s technical and business feasibility. After the study of energy demand, 12 scenarios were proposed based on the available energy sources and commercialized technologies in the market. RETScreen 4 software was used to simulate proposed scenarios and relevant techno economic discussion and analysis of the results were made. Based on “RETScreen 4” software’s simulation results, one optimized scenario was selected for the polygeneration system design and business feasibility analysis. A polygeneration system with two polygeneration sets were designed to meet energy demand of the reference project in this thesis. Considered the technical and economic information of the designed system, a business feasibility analysis of the polygeneration system for the construction industry was studied. As the last part of the thesis, a summary of business plan was made to the designed system based on the results of market research and business feasibility study.
Polygenereringsteknik är att utnyttja en enda anläggning för att erbjuda flera energitjänster  där multiplaprocesser är integrerade i ett gemensamt system. I jämförelse med separata tekniklösningar, förbättrar polygenerering systemets effektivitet avsevärt eftersom flera tjänster produceras och kapital- och produktionskostnadernadärmed minskar. I denna avhandling har ett polygenereringssystem utformats speciellt för ett projekt i byggbranschen och lämpligheten hos systemet har analyserats. Status quo och problem med nuvarande tillfälliga kraftsystemet togs med i analysen och idén att använda polygenereringssystemet som substitut har beskrivits. Ett ställverksprojekt i Al Kharj, Saudi Arabien användes som referens för att utforma polygenereringssystemet och för att analysera systemets tekniska och affärsmässiga genomförbarhet. Efter studier av efterfrågan på energi, har 12 scenarier föreslagits baserat på tillgängliga energikällor och kommersialiserade teknologier på marknaden. “RETScreen 4” programvaran anvädes fö att simulera föeslagna scenarier och en teknisk-ekonomisk diskussion och analys av resultaten gjordes. Baserat på RETScreen 4 programvarans simuleringsresultat, har ett optimalt scenario valts för design av ett polygenereringsystem och en affärsgenomförbarhetsstudie har utförts. Ett polygenereringssystem med två uppsättningar av polygenerernde subsystem har utformats för att möta efterfrågan på energi hos referensprojektet i denna avhandling. Med hänsyn taget till de tekniska och ekonomiska uppgifterna i det utformade systemet, har realiseringen av polygenereringssystemet för byggindustrin studerats. Den sista delen av avhandlingen utgör en sammanfattning  avaffärsplanen för det utformade systemet baserat på resultaten av marknadsundersökningar och en affärsförstudie.

This project has addressed the design of a cost-effective Polygeneration system that guarantees a continuous, equitable and environmentally friendly energy supply for the rural settlement of Filipinas ETCR, (in Spanish, Espacios Territoriales de Capacitación y Reincorporación) Colombia, which is currently not achieved, due to a system that relies on the national electricity grid (with numerous outages) and on LPG (Liquefied Petroleum Gas) and wood to meet the thermal demand, mainly for cooking. For this purpose, in addition to the current energy supply situation, the energy demand according to type (electricity and heat) and sector (residential, commercial and agro-livestock) is characterized. Also, the availability of renewable energy sources is examined, resulting in the existence of a potential for solar and residual biomass resources. Then, the most suitable sub-systems and technologies for their exploitation have been analyzed. In this way, HOMER Pro software has been used to find the most competitive solution (the lowest LCOE, Levelized Cost of Energy), together with a technical, economic, environmental and social analysis to analyze its impact on the ETCR. Thus, the final solution results in a Polygeneration system based on a PV (Photovoltaic) subsystem, the electrical grid and a biogas production plant (48 m3/day) by anaerobic digestion of agricultural, livestock and urban waste biomass coupled with an ICE (Internal Combustion Engine). The PV (250 kW) would be the major source of electricity generation, followed by the grid and, as a back-up, the biogas-fired ICE (25 kW), which is also used to replace LPG and wood for heating purposes. The solution presents a remarkable renewable fraction (73% instead of the current <0.5%) and a significant reduction of polluting emissions (60.5% of CO2 emissions). Moreover, it is ensured an economic viability over time (a ROI of 9.7% and DPB (Discounted Pay-Back) lower than 18 years) and a potential positive impact in the socio-economic development of Filipinas ETCR. To conclude, these results are in line with the UN SDGs (Sustainable Development Goals) 7 and 13, being an example of the viability of such systems and the positive environmental, social and economic consequences they can have in rural locations with economic difficulties and non-renewable and weak energy supplies.
Detta projekt har behandlat utformningen av ett kostnadseffektivt polygenereringssystem som garanterar en kontinuerlig, rättvis och miljövänlig energiförsörjning för bosättningen på landsbygden i Filipinas ETCR (Espacios Territoriales de Capacitación y Reincorporación på spanska) i Colombia, vilket för närvarande inte är uppnått på grund av ett existerande energisystem som är beroende av det nationella elnätet (med många avbrott) och av gasol och ved för att tillgodose det termiska behovet, främst för matlagning. I detta syfte har man förutom den nuvarande energiförsörjningssituationen även karakteriserat efterfrågan på energi efter typ (el och värme) och sektor (bostäder, handel och jordbruk och boskapsskötsel). Dessutom undersöks tillgången på förnybara energikällor, vilket påvisar att det finns potential för både solenergi och biomassa. Därefter har man analyserat lämpliga delsystem och tekniker för att kunna nyttja energikällorna. För detta har programmet HOMER Pro använts till att hitta den mest konkurrenskraftiga lösningen (med lägst LCOE), tillsammans med en teknisk, ekonomisk, miljömässig och social analys för att analysera dess inverkan på ETCR. Således är den slutliga lösningen ett system för polygenerering som bygger på ett delsystem av solceller, elnätet och en biogasproduktionsanläggning (48 m3/dag) som använder sig av anaerob nedbrytning av biomassa från både jordbruk, boskap och stadsavfall i kombination med en ICE. Solcellerna (250 kW) skulle då vara den främsta källan till elproduktion följt av elnätet, varav den biogaseldade ICE-anläggningen (25 kW) används som reserv och för att ersätta gasol och ved för uppvärmning. Lösningen innebär en anmärkningsvärd andel förnybara energikällor (73% jämfört med nuvarande <0,5%) och en signifikant minskning av förorenande utsläpp (60,5% av koldioxidutsläppen). Dessutom garanteras en ekonomisk lönsamhet med tiden (med en ROI på 9,7 % och en DPB på mindre än 18 år) och en potentiellt positiv inverkan på den socioekonomiska utvecklingen i Filipinas ETCR. Sammanfattningsvis ligger dessa resultat i linje med mål 7 och 13 av FN:s hållbarhetsmål, eftersom de är ett exempel på lönsamheten hos sådana system och de positiva miljömässiga, sociala och ekonomiska konsekvenser som de kan få på landsbygden där det förekommer ekonomiska svårigheter, och där eltillförseln är opålitlig och baserad på energikällor som inte är förnybara.

The combination of Biomass Energy with Carbon Capture and Storage (BECCS) can reduce the level of CO2 in the atmosphere. It is, therefore, seen as an interesting tool in the CO2 abatement portfolio. In a Swedish context, BECCS could contribute to the goal of CO2 neutrality by 2045. This thesis aims to investigate the application of BECCS in the district heating system of Stockholm region with a case study at the energy utility Fortum Värme. The focus of the study is the technical and economic feasibility of such an application. The applicability of Fortum Värme´s plants to implement carbon capture is investigated together with costs and technical implications on each applicable plant and the district heating system as a whole. Three plants are deemed feasible for carbon capture with a cost of about 45€/tonne of captured CO2 (not including transport or storage). A model for transport of CO2 to promising storage sites in Sweden, Norway, and Denmark is constructed for transport by pipeline and ship. Ship transport is estimated to be the most cost-efficient option in all scenarios. The total cost for BECCS is calculated at 70-100€/tonne depending on size of emissions and distance to storage locations. Furthermore, the total cost is calculated to decrease by 10-25% if some current promising technologies for carbon capture reach maturity, a market for transport services of CO2 evolves, and a number of actors are sharing the costs for storage.Calculated costs are on a similar price level as other CO2 abatement strategies such as CCS in industries, biogas, and biodiesel in the vehicle fleet. If the cost is applied directly to the heat price, without any subsidies, it would increase the price of heat by 14-21%.The major challenge of BECCS in combined heat and power production, compared to other studies based on power production, is the seasonality of heat demand. The capacity of the carbon capture system will be oversized during the summer, or undersized during the winter. This is an optimization challenge which has to be further studied.

Livestock and poultry are two growing subsectors of global farming economy with an impact on the environment and thus deserving closer attention. While the farms play a major role in providing protein essential for human diets, they are also sources of significant amounts of greenhouse gas (GHG) emissions. Hence, the sectors need to improve their environmental performance and mitigate their negative impacts on climate. To estimate the annual GHG emissions from a dairy and poultry farm, a case study was conducted in the rural area of Bangladesh. The study has considered the supply chains of both farms while estimating the emissions.  The study also estimated the GHG emission reduction potential of a small biogas based polygeneration system aimed at providing energy services in the rural area. LCA (lifecycle assessment) has been used as the main tool while estimating the emissions.

Road traffic dominates in domestic Swedish transportation and is highly dependent on fossil fuels, petrol and diesel. Currently, the use of renewable fuels in transportation accounts for less than 6% of the total energy use in transport. The demand for bioethanol to fuel transportation is growing and cannot be met through current domestic production alone. Lignocellulosic ethanol derived from agricultural crop residues may be a feasible alternative source of ethanol for securing a consistent regional fuel supply in Swedish climatic conditions.  This licentiate thesis focuses on regional transport fuel supply by considering local small-scale ethanol production from straw. It presents the results of investigations of regional transport fuel supply with respect to minimising regional CO2 emissions, cost estimates for transport fuel supply, and the availability of lignocellulosic resources for small-scale ethanol production. Regional transport fuel demand between the present and 2020 is also estimated. The results presented here show that significant bioethanol can be produced from the straw and Salix available in the studied regions and that this is sufficient to meet the regions’ current ethanol fuel demand.  A cost optimisation model for regional transport fuel supply is developed and applied for two cases in one study region, one when the ethanol production plant is integrated with an existing CHP plant (polygeneration), and one with a standalone ethanol production plant. The results of the optimisation model show that in both cases the changes in ethanol production costs have the biggest influence on the cost of supplying the regional passenger car fleet with transport fuel, followed by the petrol price and straw production costs.  By integrating the ethanol production process with a CHP plant, the costs of supplying regional passenger car fleet with transport fuel can be reduced by up to a third. Moreover, replacing petrol fuel with ethanol can cut regional CO2 emissions from transportation by half.

This thesis aims at investigating the polygeneration systems for buildings by dynamic simulation models. In particular, different polygeneration systems, supplied both by the solar renewable energy source and natural gas, were examined from the energy, exergy, economic and environmental point of view.

abstract: Just for a moment! Imagine you live in Arizona without air-conditioning systems! Air-conditioning and refrigeration systems are one of the most crucial systems in anyone’s house and car these days. Energy resources are becoming more scarce and expensive. Most of the currently used refrigerants have brought an international concern about global warming. The search for more efficient cooling/refrigeration systems with environmental friendly refrigerants has become more and more important so as to reduce greenhouse gas emissions and ensure sustainable and affordable energy systems. The most widely used air-conditioning and refrigeration system, based on the vapor compression cycle, is driven by converting electricity into mechanical work which is a high quality type of energy. However, these systems can instead be possibly driven by heat, be made solid-state (i.e., thermoelectric cooling), consist entirely of a gaseous working fluid (i.e., reverse Brayton cycle), etc. This research explores several thermally driven cooling systems in order to understand and further overcome some of the major drawbacks associated with their performance as well as their high capital costs. In the second chapter, we investigate the opportunities for integrating single- and double-stage ammonia-water (NH3–H2O) absorption refrigeration systems with multi-effect distillation (MED) via cascade of rejected heat for large-scale plants. Similarly, in the third chapter, we explore a new polygeneration cooling-power cycle’s performance based on Rankine, reverse Brayton, ejector, and liquid desiccant cycles to produce power, cooling, and possibly fresh water for various configurations. Different configurations are considered from an energy perspective and are compared to stand-alone systems. In the last chapter, a new simple, inexpensive, scalable, environmentally friendly cooling system based on an adsorption heat pump system and evacuated tube solar collector is experimentally and theoretically studied. The system is destined as a small-scale system to harness solar radiation to provide a cooling effect directly in one system.
Dissertation/Thesis
Doctoral Dissertation Mechanical Engineering 2018

Electricity generation using renewable energy helps in combating the emissions produced by fossil fuel-based units. One such renewable energy source which can be utilized more effectively is solar energy and it is one of the finest accessible choices for fighting the issues of increasing electricity use, fossil fuel depletion, and global warming because it is available freely and abundant. However, there are some limitations with solar energy-based systems and one of them is their intermittency in operation as solar energy is not accessible throughout the day and does not remain the same throughout the year. Utilization of solar energy to generate electricity, cooling, and freshwater, hydrogen (as an energy source) in remote areas in a sustainable way still poses lots of challenges to researchers because of poorer conversion efficiencies. The goal of the current work is to design new solar-operated systems to produce electricity, cooling, hydrogen, and fresh water in remote areas. Thus, in this thesis, three solar energy-based systems (solar heliostat system, parabolic trough collector (PTC) operated polygeneration system, and solar operated trigeneration system) for the self-sustained community are presented and evaluated by thermodynamic principles using energy and exergy analyses for technical feasibility. Parametric study of each system individually would help to understand the impact of design factors on the systems performance. System 1 is a solar heliostat system (based on molten salt) that can meet out the electricity demand, hydrogen (for the refuelling of the vehicles) and cooling load in a community in remote areas. Steam Rankine cycle is utilized to feed the electrical power demand while some of the steam is bleed out to operate the two-stage ammonia water-based absorption system for cooling application. The result of the System 1 shows that with a heliostat area of 6000 m2 , 372 kW of electricity, 610 kW of cooling capacity, and 7.2 kg/h of hydrogen is generated. Furthermore, results of exergy study reveals that the significant exergy is being destroyed in the central receiver (1170 kW) followed by heliostat (980 kW). The performance evaluation of the presented system is made via exergy and energy efficiencies and estimated as 17.7%, and 38.9% respectively. Effects of some crucial parameters such as direct normal irradiance, evaporator temperature, the bleeding ratio etc. have been studied on the overall system performance. It has been found that 55% of useful exergy is being destroyed in the central receiver and heliostat iv field. On an average DNI of 700 W/m2 , for a 6 hour day the designed system can provide a cooling capacity of 3 kW to each house with an electrical load of 2 kW. Furthermore, the produced hydrogen can fuel, 100 vehicles with an average range of 100 km per day. Parametric analysis reveals that the central receiver efficiencies increase with an increase in DNI. System 2 is a new parabolic trough collector (PTC) operated polygeneration system that is used to produce freshwater, hydrogen, cooling, and electricity in a residential society. Dowtherm A (a heat transfer fluid) is utilized for transferring the heat from PTC to ORC, which is used to produce electrical power. The produced electrical power is utilized in three different ways, namely, to run the home appliances, to generate hydrogen (using water electrolysis), and to produce cooling (through a vapor compression cycle). Vapor compression cycle supplied the cooling to preserve the food, milk, and to operate the freezing desalination process. Effects of several factors, such as direct normal irradiance, evaporator temperature, and seawater inlet temperature, have been analyzed on the overall system behaviour. Thermodynamic study results show that for a PTC area of 2000 m2 , an electrical output obtained is 72 kW, the cooling rate is 112 kW, and the amount of fresh water obtained is 18.4 l/day and 10.8 kg/day of hydrogen for mean solar irradiation of 700 W/m2 . The systems’ energy efficiency is computed as 17.5%, and systems’ exergy efficiency as evaluated as 10.9%. Simulation results show that on a typical summer day, in India (environment temperature of 35℃, direct normal irradiation of 700 W/m2 ), the presented system will give electrical power to a housing society of around 60 houses/apartment (having 250 people) in a sustainable way. Furthermore, the proposed system delivers a cooling rate of 2 kW per house. The analysis also reveals that the rate of exergy destroyed in the parabolic trough collector is extreme leading to poor overall efficiencies of the system. System 3 is a new solar-operated trigeneration system to provide cooling, electricity, and fresh water using PTCs in remote areas. Electrical power is generated by using ORC, and cooling and fresh water (using freezing desalination technique) is obtained by two-stage NH3-H2O vapor absorption system run by solar energy. Simulation results show that for PTC arrays of 200 m2 , an electrical output obtained is 3.3 kW, cooling rate is 20.4 kW, and rate of freshwater produced is 36 kg/h for an average solar irradiance of 700 W/m2 . Additionally, sensitivity analysis is conducted by varying the parameter like solar irradiation, evaporator temperature, seawater inlet temperature etc. and their effect on performance characteristics of the overall setup is v investigated. Analysis reveals that maximum exergy is being wasted in the parabolic trough collectors pursued by HRVG. Simulation results show that the systems’ energy efficiency is 18.8% and the systems’ exergy efficiency is 4.7%. Additionally, PTCs’ exergy and energy efficiencies are calculated as 29.8% and 70%, respectively. Analysis also reveals that PTC has an exergy destruction rate of 85.0 kW. In overall, each system has its own merits and demerits and could provide a potential option for solar-dominated remote areas to obtain cooling, freshwater, hydrogen, and electrical power in an environmentally safer manner. It has been observed that System 1 is suitable for the location where sufficient sunshine is available to produce hydrogen, electricity and cooling for a residential community of 200 houses (800 people). However, System 2 can be installed or recommended for the location having sufficient sunshine and scarcity of potable drinking water. The designed system produced four useful outputs namely, electricity, cooling, freshwater and hydrogen for the community of 250 people. While System 3 can be implemented in the location where there is a need of cooling, electricity and freshwater with an abundance of sunshine and source of saline water. Additionally, the results in this thesis clearly shows the importance of hydrogen production in any solar energy system. The result presented in the current thesis may help the designers/researcher to create a self-sustained community in a more environmental and benign manner.

The global warming phenomenon as a significant sustainability issue is gaining worldwide support for development of renewable energy technologies. The term ‘polygeneration’ is referred to as “an energy supply system, which delivers more than one form of energy to the final user”, for example: electricity, cooling and desalination can be delivered from polygeneration process. The polygeneration process in hybrid solar thermal power plant can deliver electricity with lesser impact on environment compared to conventional fossil fuel based power generating system. It is the next generation energy production technique with a potential to overcome intermittence of renewable energy. In this study, the polygeneration process simultaneous production of power, vapor absorption refrigeration (VAR) cooling and multi-effect humidification and dehumidification (MEHD) desalination system from different heat sources in hybrid solar-biomass (HSB) system with higher energy efficiencies (energy and exergy), primary energy savings (PES) and payback period are investigated. There are several aspects associated with hybrid solar-biomass power generation installations such as state wise availability of biomass resources, solar direct normal irradiance (DNI) have been analyzed. Month wise solar and biomass heat utilization also has been analyzed for hybrid system in four regions of India (East: Guwahati, Assam; West: Udaipur, Rajasthan; North: Delhi, South: Madurai, Tamil Nadu). The month wise daily average solar radiation is also considered as 20%, 40%, 60% and 80% and remaining heat is taken from biomass resource in northern region (Delhi) in the proposed hybrid plant. The thermodynamic evaluation (energy and exergy) of HSB power plant has also been investigated. The total input energy of the proposed hybrid system is taken v from the heat transfer fluid through parabolic trough collector (PTC) as per availability of solar resource and remaining from biomass to maintain the steam at superheated state of 5000C and 60 bar and supplied to turbine at steam mass flow rate of 5 kg/sec. The energy and exergy analyses of 5 MW HSB system with series mode was carried out to identify the effects of various operating parameters like DNI, condenser pressure, turbine inlet temperatures, boiler pressure on net power output energy and exergy efficiencies. The VAR cooling system operates using the extracted heat taken from turbine and condenser heat of the VAR cooling system is used in MEHD system for production of drinking water as per demand requirement. Though the production of electricity decreases due to extraction of heat from turbine for VAR cooling and MEHD desalination, the complete system meets the energy requirements & increases the PES. The thermodynamic evaluation (energy and exergy), optimization and payback period of polygeneration process in HSB thermal power plant for combined power, cooling and desalination is investigated to identify the effects of various operating parameters. The system has achieved a maximum energy efficiency of 49.85% and exergy efficiency of 20.94%. The Primary energy savings of polygeneration process (PESPP) in HSB system is achieved at 50.5%. The electricity generation from polygeneration process increased to 78.12% as compared to simple thermal power plant. The payback period of polygeneration process in HSB thermal power plant is 1.5 years, which is less than solar thermal power plant, HSB thermal power plant, Cogeneration in HSB thermal power plant.