Nos países em desenvolvimento, como o Brasil, a secagem de produtos agrícolas com uso de secador solar representa uma alternativa promissora de baixo custo, reduzindo perdas e agregando valor aos produtos. Porém, devido à natureza periódica da radiação solar e das condições do tempo, nem sempre é viável sua utilização. Dessa forma, o objetivo do trabalho foi a modelagem de um sistema auxiliar de armazenagem de energia térmica (SAET) em um secador solar, cuja finalidade é armazenar energia durante o dia para ser utilizada conforme necessário. Com base em registros de temperatura e umidade relativa, ambas do ar, de um secador solar, foi feito um estudo da termodinâmica dos processos envolvidos, a fim de propor meios para o dimensionamento do SAET. Foram explorados a estimativa do fluxo de massa de ar no secador, a modelagem da temperatura em função da radiação, e o dimensionamento para diferentes modos de operação do SAET, considerando o sistema ideal. Este dimensionamento tratou tanto do caso de fornecimento contínuo de fluxo de água preaquecida, como de uso de automação para controlar o fluxo. A estimativa de fluxo de ar no secador se aproximou de valores típicos encontrados na literatura. O dimensionamento do sistema, embora considerado ideal, mostra que a utilização do SAET melhora o desempenho do secador, servindo como parâmetro para melhor compreender o comportamento das variáveis durante seu funcionamento. / In developing countries such as Brazil, drying of agricultural products by using solar dryer is a promising low cost alternative to reduce losses and add value to products. However, due to periodic behavior of solar radiation and weather conditions, the use of solar drier is not always feasible. The objective of this study is to model an auxiliary thermal energy storage (ATES) in a solar drier, aiming to store energy during the day to be used as needed. Based on both air temperature and relative humidity records of a solar dryer, the thermodynamics of the underlying processes was studied in order to propose means for designing the ATES. It was addressed the estimative of the air mass flow in the dryer, the modeling of the temperature as a function of the radiation, and the designing of the ATES for different modes of operation, considering the optimal system. The designing dealt with both the continuous supply of preheated water flow and the use of automation for controlling the flow. The estimated air flow in the dryer approached typical values found in the literature. The designing of the system, although considered ideal, shows that the use of ATES improves the drying performance, serving as a parameter to better understand the behavior of variables during operation.

A photo-voltaic system consists of solar cells, power converters, battery and the load. The power converter interfaces the solar cells, battery and the load. The battery serves to equalise the energy demand (load) and the energy supply (solar cell). Currently the solar cells and the battery cost nearly 90% of the system cost. A typical photo-voltaic system can adopt various power bus configurations. Battery tied bus is the simplest of the power bus configurations. In this topology, the battery is always attached to the bus. This system is extremely simple in terms of power circuit configuration as well as control. Such systems weigh less and are more reliable. However, the battery tied bus suffers certain disadvantages. The first among them is the poor utilisation of solar panels. The load has to tolerate the full swing of the battery voltage variation. On account of the constraint on the solar panel voltage, the solar panels may not be loaded to the maximum power capacity. Such operating conditions lead to gross under-utilisation of the expensive solar panels. The battery tied bus configuration is designed, built and evaluated experimentally with 4 solar panels rated at 35 W each and a lead acid battery of 12 V 42 AH rating. This thesis explores alternate power architecture to overcome the above limitations. Load regulation and maximum power harvesting from the solar panels are the objectives. In the proposed configuration, a bidirectional power converter is inserted between the bus and the battery. The bidirectional power converter operates in boost mode and charges the battery when the sunlight is available. During eclipse period, it operates in buck mode and meets the load demand. The maximum power is extracted from the panels by controlling the voltage across the solar panels. The bus voltage reference is computed by MPPT block and the bus voltage is regulated to the reference voltage through closed loop control. So the maximum power is extracted from the panels at the expense of extra bidirectional power converter. Even though there is an additional power loss due to the introduction of power converter, this power bus configuration is superior because it increases the output power from the panel itself. The entire control logic implementation is done digitally using dspic30F6010A. The simulation is done by writing script files in C language. The proposed bus configuration is designed, built and evaluated experimentally with the same setup and the results are then compared.

Baigiamajame magistro darbe nagrinėjamos decentralizuoto (paskirstytojo) generavimo ir atsinaujinančių energijos išteklių panaudojimo sprendimai, aprūpinant pastatą įvairia energija – šiluma, vėsa, karštu vandeniu, elektra. Energija aprūpinama panaudojant tokius įrenginius – kogeneratorių, kompresorinę ir absorbcinę šaldymo mašinas, saulės kolektorius, dujinį katilą. Apibūdinami pasirinkti įrenginiai, jų veikimo principai, savybės, atskleidžiami jų privalumai ir trūkumai. Parengiamos trys alternatyvių variantų principinės energijos sistemų schemos, suformuotos iš minėtų įrenginių derinių. Pristatomi šių alternatyvių įvairios eneregijos gaminimo variantų galios ir energijos kiekių rodikliai. Parenkamas optimalus naujų technologijų derinys. Alternatyvių variantų ekonominis pagrįstumas įvertinamas, parenkant optimalų energijos generatorių derinį atsižvelgiant į jų bendrą atsiperkamumą. Apibendrinus teorines žinias ir gautus skaičiavimo rezultatus, pateikiamos baigiamojo darbo išvados ir pasiūlymai. Darbą sudaro 6 dalys: įvadas, teorin�� dalis, analizinė dalis, ekonominė dalis, išvados ir pasiūlymai, literatūros sąrašas. Darbo apimtis – 61 psl. teksto be priedų, 34 iliustr., 11 lent., 46 literatūros šaltiniai. Atskirai pridedami darbo priedai. / Solutions of decentralized (distributed) production and application of renewable energy sources in the case of different energy - like heating, cooling, hot water, electricity - supply for a building were analyzed in the final master thesis work. Energy supply sources are cogenerator, compressor and absorption cooling machines, solar collectors, gas boiler. Selected devices, their principles of work, characteristics, their advantages and disadvantages were described. Three schemes of principal energy system alternative were described, using combinations of devices mentioned above. Power and energy amount indexes of different energy generating alternatives were specified. The optimal combinations of new technologies were selected. After the optimal combination of energy generating system was done, economical validity of alternatives were estimated taking into account their total payback time. After theory and received results were summarized, the conclusions and suggestions were presented in the end of the final master work. Work consists of 6 parts: introduction, theory, analysis part, economical part, conclusions and suggestions, literature source. Size of Work: 61 pages of text excluding the appendixes, 34 pictures, 11 tables, 46 literature sources. Appendixes of the work are attached separately.

This thesis presents and demonstrates procedures to model and optimize the collector field of a parabolic trough solar thermal power plant. The collector field of such a plant is universally organized into parallel loops of solar collectors. Heat transfer fluid returning from the energy conversion plant is heated to a moderately high temperature in the field. Typically fluid enters a collector loop around 270 °C and leaves at 380 °C. The fluid is then returned to the plant to generate steam. In the first part of this thesis, the collector field and the energy conversion system of a typical parabolic trough solar thermal power plant are modeled. The model is compared with actual performance data and is enhanced and verified as necessary. Originally, the collectors in the plants under consideration were provided with evacuated tube receivers of the highest feasible efficiency without much regard for cost effectiveness. In practice, these receivers have failed at an unexpected rate and need replacement. It is unlikely that a very expensive evacuated tube receiver is now the most cost effective for every location in a collector loop. In particular, a receiver optimized for 270 °C operation may not be optimal at 380 °C. For example, a relatively inexpensive receiver with a flat black absorber and no vacuum may be more cost effective in the lower temperature segments of a loop. In the second part of this thesis, a procedure for the optimum deployment of collectors is developed and demonstrated. The results of this research should be directly applicable to the refurbishment and upgrading of several of the largest solar energy plants in the world.

Η ηλιακή ενέργεια μπορεί να συμβάλει στην αντιμετώπιση του ενεργειακού προβλήματος, με την ευρεία αξιοποίηση των φωτοβολταϊκών και των θερμικών ηλιακών συλλεκτών. Τα φωτοβολταϊκά συστήματα που συνδυάζονται με θερμικές μονάδες κυκλοφορίας νερού ή αέρα, για την απολαβή της θερμότητας από αυτά και την ικανοποιητική διατήρηση της απόδοσής των, αποτελούν τα υβριδικά φωτοβολταϊκά/θερμικά συστήματα (φβ/θ). Τα συστήματα αυτά παράγουν ηλεκτρική και θερμική ενέργεια ταυτόχρονα, αυξάνοντας την ολική παραγόμενη ενέργεια. Με τη χρήση ορισμένων διατάξεων βελτίωσης της απολαβής της θερμότητας από τα φωτοβολταϊκά και της αύξησης της αποδιδόμενης ενέργειας των φωτοβολταϊκών και των θερμικών ηλιακών συλλεκτών, είναι δυνατή η βελτίωση της αποδοτικότητας των συσκευών αυτών, για μια πιο αποτελεσματική εφαρμογή τους στα κτήρια. Η διπλωματική εργασία που ακολουθεί περιλαμβάνει τη μελέτη φωτοβολταϊκών, υβριδικών φωτοβολταϊκών και θερμικών ηλιακών συσκευών. Πραγματοποιήθηκε μελέτη υβριδικού φωτοβολταϊκού/θερμικού συστήματος αέρα με διάφορες βελτιώσεις της αποδοτικής λειτουργίας του και με την προσθήκη μεταλλικών φύλλων ή σωλήνων ροής νερού στον αεραγωγό. Ακόμη, μελετήθηκε επίπεδος ηλιακός θερμικός συλλέκτης με προσθήκη διάφορων τύπων ανακλαστήρων (λευκή επιφάνεια, γαλβανιζέ μεταλλικό φύλλο και καθρέφτης). Πραγματοποιήθηκαν επίσης πειράματα με σωλήνα κενού, ο οποίος συνδυάστηκε με ανακλαστήρες για την αύξηση της προσλαμβανόμενης ηλιακής ακτινοβολίας και βελτίωση της αποδιδόμενης θερμότητας. Με βάση τα αποτελέσματα παρατίθενται συμπεράσματα και προτάσεις σχετικά με τις σύνθετες διατάξεις που αναφέρθηκαν. / Solar energy systems can contribute to energy demand by the proper synergy of photovoltaics and solar thermal collectors. The PV modules which are combined with thermal units and circulating water or air to extract the heat from them, constitute the hybrid photovoltaic/thermal systems (PV/T). These systems provide electrical and thermal energy simultaneously, increasing the total energy output. Adapting some effective heat extraction elements to PV modules and applying devices to have solar radiation increase by the absorbing surfaces of PV and of thermal collectors, an improvement of operation and performance of these systems can be achieved regarding their application to buildings. The thesis that follows includes a study of photovoltaics, hybrid photovoltaic/ thermal systems and solar thermal collectors. More specifically, a study of an air heating hybrid photovoltaic/thermal system was performed, improving suitably the heat extraction by inserting corrugated metallic sheets or water pipes, inside the air channel that is attached to rear surface of PV modules. In addition, a solar thermal collector was studied, by applying several types of reflectors (white plate reflector, galvanized iron plate reflector and specular reflector). Furthermore, a vacuum tube type collector was tested, combined also with reflectors to increase input solar radiation and increase thermal performance. Finally, conclusions and suggestions for a further study, on the above mentioned solar energy systems is included, based on the reported experimental results.

A promising and novel solar concentrator design has been thoroughly investigated and optimised. A prototype concentrator based on this novel geometry was validated using ray tracing techniques. This ray tracing demonstrated the comparative performance of this novel concentrator in regards to equivalent parabolic dishes. The effect of mirror surface normal errors on performance was established using Monte-Carlo based ray tracing code, which agreed well with the optical performance of this prototype which was determined experimentally. A need for low-cost solar cookers to replace bio-mass worldwide was identified, and the concentrator design was then developed as a low-cost solar oven. Despite existing in some number, no current design is able to achieve high performance at low-cost. An industrial partner, Dytecna, was initially involved in the process of this development of the system as a solar cooker. In support of a field trial for the solar cooker developed with Dytecna, a detailed thermal model of the oven was developed. A low-cost lightmeter was constructed and calibrated in order to measure the direct normal irradiance during the field trial in Italy. Laboratory work provided baseline results for the heating of various thermal masses in the oven. The Italian field trials provided a wealth of feedback into the design of the system and many valuable results. The solar cooker was able to bring 0.75L of water to the boil in 33 minutes with an average heat throughput of 203W. Important benchmark results and practical experience of several competing receiver materials was obtained; further lab testing provided more accurate measurements of the receivers' performances. The experiences of the Italian field trial were fed back into the design of a subsequent prototype, intended for a much larger field trial in Tanzania. Improvements in the hotplate, receiver material, and the oven were all incorporated into the design. Additionally, the structure of the solar cooker was redesigned to incorporate a low-cost wooden construction. Supporting work was conducted for the month long trial in which 8 solar cookers would be distributed to families in Tanzania. The field trial in Tanzania provided a wealth of user feedback into the design. At the same time the new solar cooker exceeded previously established performances in Italy. The new design was able to provide an average of 246W of heat to 1kg of water, which was brought to boiling point in 25 minutes. This represents a heating efficiency of 66% compared to the incident solar flux on the hotplate. In response to findings during the Tanzanian trials, further laboratory work was conducted into establishing the reflectivities of low-cost candidate mirror materials. Throughout all phases of the project the design of the solar cooker was refined and improved with the goal of a solar cooker design that could reach price-point, performance, and usability standards which would ensure market success.

Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-12-19Bitstream added on 2014-06-13T18:26:32Z : No. of bitstreams: 1 sato_ai_me_bauru.pdf: 1188425 bytes, checksum: a339b70a2f5c112ab87f327dbf976662 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A utilização de coletores solares - seja para aquecimento de água, produção de energia elétrica, calefação de ambientes ou ainda alimentando sistemas de refrigeração - apresenta uma forte tendência de expansão. As principais razões para isto são que fontes de energias renováveis possuem baixo impacto ambiental além do fato que estes sistemas estão se tornando financeiramente acessíveis. A pesquisa científica neste campo tem acompanhado tal expansão e o coletor solar com tubos evacuados destaca-se como um importante foco de estudos. Projetos deste tipo caracterizam-se pelo seu peculiar processo de fabricação e a sua reduzida perda térmica para o ambiente, aumentando a sua eficiência, principalmente nas regiões frias. Quanto à análise dos fenômenos físicos presentes na operação deste equipamento, devem ser considerados os conceitos inerentes a todos os coletores, como: os mecanismos de captação de radiação solar, convecção natural, condução e os perfis de velocidades e temperaturas ao longo dos sistema. Com isto, diversos estudos foram publicados para obter a representação da estratificação do fluido no interior dos tubos e do reservatório, assim como para a modelagem analítica do problema de fluxo de calor. Este trabalho propõe o estudo de aquecedores solares com tubos evacuados, suas características de operação e parâmetros operacionais. Para o desenvolvimento desta pesquisa, utilizou-se uma ferramenta computacional auxiliar - neste caso, um software para fluidodinâmica computacional (na sigla em inglês, CFD) / The solar collectors usage - whether for water heating, electricity production, ambient heating or associated as heat source in cooling systems - has a strong expansion in studies and investments. The man reasons for this are that renewable energy sources have low environmental impact and the fact that these systems are becoming economic reliable. Researches in this field followed such expansion and the evacuated tube solar collector system stands as an important study focus. Such designs are characterized by their peculiar manufacturing process and its reduced heat loss to the ambient, which increases its thermal efficiency (especially in cold regions). The physical phenomena presented in the operation of this equipment is usually analyzed considering the concepts inherent to all collectos, such as concepts coupled to solar radiation receiving, natural convention heat transfer, conduction through glass thickness, and velocity and temperature profiles in the system. Numerous studies were published to represented the fluid stratification inside the tubes and the storage tank, as well as the analytical modeling of the fluid thermal problem. The objectives of this paper were the study of a solar heater with evacuated tube, regarding the operating characteristics and operational parameters. For this reason, a computational fluidynamics (CFD) was used

Byggnaden i undersökningen stod färdig i oktober 2016 och är belägen på Kvarnvägen 31 i Gemla. Syftet är att kartlägga energianvändningen och fastställa huruvida installation av solfångare är gynnsam. Målet är att kartlägga energiåtgången, redovisa förbättringsåtgärder och analysera de tekniska installationerna. Undersökningens metoder bestod av studiebesök, platsbesök, ritningsstudie och en okulärbesiktning med värmekamera. För att kartlägga och identifiera energiåtgången har modulering av klimatskal och installationer gjorts i VIP-Energy. Resultatet av energikartläggningen blev samma som den projekterade. Framtagen energideklaration gav byggnaden energiklass B. Att ha solfångare installerad visade sig vara teoretiskt energi- och kostnadseffektiv om de är kopplade enligt förslag. Det befintliga ventilationssystemet i byggnaden är teoretiskt fördelaktig för både avrostning och föruppvärmning. Förbättringsförslagen är att justera solfångarvinklen samt att koppla om värmetillförseln som erhålls av solfångarna. / The building in this survey was completed in October 2016 and is located at Kvarnvägen 31 in Gemla. The purpose of the study is to map the energy consumption and determine whether the installation of solar collectors is beneficial or not. The goal is to map the energy use in the building, report improvement measures and analyse the technical installations. The qualitative methods consisted of a study visit, site visits, review of drawings and an ocular survey of the building with a thermal camera. In order to calculate and analyse the building´s energy use, modelling of the building envelope components and technical installations were performed in VIP-Energy. The results of the energy survey shows that the calculated energy use for the building is similar to the projected energy use and the energy declaration places the building in energy class B. Many factors are of significant importance in optimizing solar collectors such as inclination angle, orientation and installation type. Having solar collectors installed proved to be beneficial both in terms of energy and cost if they are connected as proposed. HSB FTX is theoretically advantageous for both preheating of supply air and defrosting of the building's ventilation system. The enhancement proposals are to adjust the inclination angle of the solar collectors and to reconnect the heat input obtained from the solar collectors.

Orientador: Vicente Luiz Scalon / Banca: Carlos Alberto Carrasco Altemani / Banca: Alcides Padilha / Resumo: A utilização de coletores solares - seja para aquecimento de água, produção de energia elétrica, calefação de ambientes ou ainda alimentando sistemas de refrigeração - apresenta uma forte tendência de expansão. As principais razões para isto são que fontes de energias renováveis possuem baixo impacto ambiental além do fato que estes sistemas estão se tornando financeiramente acessíveis. A pesquisa científica neste campo tem acompanhado tal expansão e o coletor solar com tubos evacuados destaca-se como um importante foco de estudos. Projetos deste tipo caracterizam-se pelo seu peculiar processo de fabricação e a sua reduzida perda térmica para o ambiente, aumentando a sua eficiência, principalmente nas regiões frias. Quanto à análise dos fenômenos físicos presentes na operação deste equipamento, devem ser considerados os conceitos inerentes a todos os coletores, como: os mecanismos de captação de radiação solar, convecção natural, condução e os perfis de velocidades e temperaturas ao longo dos sistema. Com isto, diversos estudos foram publicados para obter a representação da estratificação do fluido no interior dos tubos e do reservatório, assim como para a modelagem analítica do problema de fluxo de calor. Este trabalho propõe o estudo de aquecedores solares com tubos evacuados, suas características de operação e parâmetros operacionais. Para o desenvolvimento desta pesquisa, utilizou-se uma ferramenta computacional auxiliar - neste caso, um software para fluidodinâmica computacional (na sigla em inglês, CFD) / Abstract: The solar collectors usage - whether for water heating, electricity production, ambient heating or associated as heat source in cooling systems - has a strong expansion in studies and investments. The man reasons for this are that renewable energy sources have low environmental impact and the fact that these systems are becoming economic reliable. Researches in this field followed such expansion and the evacuated tube solar collector system stands as an important study focus. Such designs are characterized by their peculiar manufacturing process and its reduced heat loss to the ambient, which increases its thermal efficiency (especially in cold regions). The physical phenomena presented in the operation of this equipment is usually analyzed considering the concepts inherent to all collectos, such as concepts coupled to solar radiation receiving, natural convention heat transfer, conduction through glass thickness, and velocity and temperature profiles in the system. Numerous studies were published to represented the fluid stratification inside the tubes and the storage tank, as well as the analytical modeling of the fluid thermal problem. The objectives of this paper were the study of a solar heater with evacuated tube, regarding the operating characteristics and operational parameters. For this reason, a computational fluidynamics (CFD) was used / Mestre

Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017. / This thesis contains innovations that could help homesteads in sub-Sahara Africa (SSA) to ‘harvest’ more energy from flat solar energy collection surfaces. The thesis makes the assumption that universal resolution of energy poverty is a long term issue – and may not realistically be achieved using the traditional electrification route of: Fossil fuel/Hydro potential → electricity → transmission/distribution → paid for/free usage. Using a combination of literature search, Transient System Simulation (TRNSYS) modelling and experimental validation, the thesis notes the bi-hemispherical tropical location of most of the region and the abundant solar resource. It therefore advocates extensive use of the resource at home level for both electricity generation, and fluid heating/preheating purposes. Using mathematical models, the thesis critically examines relationships among energy incidence, transformation and yield from a flat surface for both Photovoltaic (PV) and Solar Thermal (ST) usage. It suggests the first set of innovations for the region: the two azimuths installations. The second set uses TRNSYS and Operations Research (OR) modelling to optimise selection of PV equipment meeting a starter–home’s energy loads throughout the region. Recommendations for both sets of innovations are presented in the form of colour coded maps. The third innovation in the thesis is the patented gravity driven, hydro-mechanical solar tracker, a novel solar tracking device in three different operation and control modes. In summary, one patent, 4 journal papers and 5 peer-reviewed international conference papers comprise the work.