Submitted by Fabricia Fialho Reginato (fabriciar) on 2015-06-30T23:58:11Z No. of bitstreams: 1 ClauberFerasso.pdf: 8384052 bytes, checksum: dc9cfb947f94d52412c3434032ae62da (MD5) / Made available in DSpace on 2015-06-30T23:58:11Z (GMT). No. of bitstreams: 1 ClauberFerasso.pdf: 8384052 bytes, checksum: dc9cfb947f94d52412c3434032ae62da (MD5) Previous issue date: 2013-08 / FINEP - Financiadora de Estudos e Projetos / A contribuição das fontes de energias alternativas, principalmente a solar térmica, para a diversificação da matriz energética brasileira é importante devido, principalmente, ao aumento da demanda do consumo de energia elétrica, ocasionado pelo progresso e desenvolvimento da população e do País. Parte deste aumento é consequência do uso simultâneo de milhares de chuveiros elétricos, na maioria das vezes no horário de ponta, considerado um dos responsáveis pelo elevado pico na curva de demanda entre 18 e 21 horas. Frente a isso, a utilização da energia solar através de sistemas de aquecimento solar para o uso doméstico, vem ao encontro deste propósito. Após análise do consumo médio mensal de energia elétrica fornecida pela concessionária AES Sul no período de um ano em um conjunto residencial na cidade de Canoas – RS, foi possível estimar o custo da utilização do chuveiro elétrico nesse local, por domicílio, que representa entre 25 a 30 % da fatura de energia elétrica. A produção de energia térmica através de sistemas de aquecimento solar para pré- aquecimento de água quente para uso doméstico foi simulada utilizando-se o software TRNSYS, para diversas configurações de sistemas (área de coletor e capacidade de armazenamento). A relação entre a demanda de energia para aquecimento de água e a energia produzida pelo SAS foi parametrizada utilizando-se o conceito de fração solar mensal e anual. Foi considerada uma temperatura mínima de consumo de água quente de 40 °C e um perfil de consumo correspondente à taxa de ocupação média dos domicílios no local. Os dados climáticos necessários para a simulação foram obtidos a partir do ano meteorológico típico (TMY) para Porto Alegre. Os resultados obtidos das diversas simulações mostraram que é possível obter uma economia direta para consumidor de até 58% de energia consumida pelo chuveiro elétrico e uma economia de energia estimada em 12.399 kWh para o sistema elétrico ao longo de 20 anos. Estes resultados podem ser melhorados com a diminuição do custo unitário do SAS ou através de incentivos decorrentes da diminuição dos custos de ampliação da capacidade da rede elétrica por parte das concessionárias, decorrentes da mudança do perfil de carga do sistema. / The contribution of alternative energy sources, particularly solar thermal, to diversify the Brazilian energy matrix is important, mainly due to increased demand of electricity consumption, caused by the progress and development of the population as well as the country. Part of this increase is a consequence of the simultaneous use of thousands of electric showers, mostly during peak hours, considered one of the chief responsible for the high peak in the demand curve between 6.00 and 9.00PM. Given this, the use of solar energy, through solar heating systems for domestic use, meets this purpose. After the analysis of the average monthly consumption of electricity provided by the supplier AES Sul in the period of one year in a residential complex in the city of Canoas – RS, it was possible to estimate the cost of using electric showers in that location, per household, which was between 25 to 30% of the electricity bill. The production of thermal energy through solar heating systems for preheating domestic hot water was simulated using the TRNSYS software for various system configurations (collector area and storage capacity). The relationship between energy demand for water heating and energy produced by SAS was parameterized using the concept of monthly and annual solar fraction, considering a minimum temperature of hot water of 40 ° C, and a profile of consumption corresponding to the average occupancy rate of households at the site. The climatic data required for the simulation were obtained from the typical meteorological year (TMY) to Porto Alegre and the results of several simulations showed that it is possible to get direct savings to the consumer up to 58% of energy consumed by electric shower and energy savings estimated at 12,399 kWh for the electricity system over a period of 20 years. These results can be improved by reducing the unit cost of SAS or through incentives from lowering the cost of expanding the capacity of the electric grid by suppliers, resulting from the change of the system load profile.

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.

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.

Submitted by JOSÉ APARECIDO SILVA DE QUEIROZ null (jqueiroz@unilins.edu.br) on 2016-06-28T17:33:24Z No. of bitstreams: 1 TESE FINAL JOSÉ QUEIROZ.pdf: 1990890 bytes, checksum: 8dbd46996efdf66f13c164f994bd6087 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-06-29T20:20:08Z (GMT) No. of bitstreams: 1 queiroz_jas_dr_bot.pdf: 1990890 bytes, checksum: 8dbd46996efdf66f13c164f994bd6087 (MD5) / Made available in DSpace on 2016-06-29T20:20:08Z (GMT). No. of bitstreams: 1 queiroz_jas_dr_bot.pdf: 1990890 bytes, checksum: 8dbd46996efdf66f13c164f994bd6087 (MD5) Previous issue date: 2016-04-29 / O principal objetivo deste estudo é avaliar, com bases em resultados experimentais, um sistema de aquecimento solar constituído de mangueira de polietileno que permite a transferência do calor gerado pela radiação solar direta e/ou difusa (Energia Solar Térmica) para a água. O sistema foi dimensionado para atender a demanda de um Centro de Ressocialização com capacidade para 220 internos. Justifica-se a escolha do tema pelo fato de que consiste em um assunto atual de grande relevância, principalmente porque vive-se uma crise energética em nível mundial. O estudo comprova através de um experimento a viabilidade do aquecedor solar de baixo custo, considerando-se sua aplicabilidade em locais que demanda grande volume de água aquecida para banho. Os resultados demonstraram que o sistema alternativo proposto atendeu de forma eficiente e econômica a demanda solicitada, o que pode ser adotada pelo poder público em qualquer um de seus segmentos que necessite de água aquecida, com objetivo de reduzir custos e contribuir com o sistema energético brasileiro. O sistema foi analisado para atuar em fluxo continuo e fluxo intermitente, ambos objetivando aquecer a água a temperaturas superiores a 37 °C no inverno. Os resultados alcançados atenderam as expectativas coletando grandes volumes, com temperaturas médias acima de 42 °C. / The aim of this study is to evaluate, with bases on experimental results, a solar heating system consists of polyethylene hose that allows the transfer of heat generated by direct solar radiation and / or diffuse (Solar Thermal Energy) to the water. The system has been designed to meet the demand of a Rehabilitation Center with a capacity for 220 inmates. Justified the choice of the theme for the fact that consists of a current subject of great importance, especially because it lives in an energy crisis worldwide. The study proves through an experiment the viability of solar heater low cost, considering their applicability in places that demand large volume of heated water for bathing. The results showed that the alternative system proposed met efficiently and economically the requested demand, which can be adopted by the government in any of its segments that need heated water, in order to reduce costs and contribute to the Brazilian energy system. The system was analyzed to operate in continuous flow, intermittent flow, both aiming at heating the water to temperatures above 37 °C in winter. The results achieved met the expectations collecting large volumes, with average temperatures above 42 °C.

Ce travail s'inscrit dans le cadre de la recherche des solutions d’économie d'énergie du bâtiment tout en utilisant des sources naturelles et renouvelables (Energie solaire pour le chauffage et la géothermie pour le rafraîchissement). Il est nul besoin de rappeler que l'Algérie dispose d'un potentiel énergétique hélio géothermique important. Dans ce travail de thèse on s'intéresse particulièrement à l'étude du confort thermique (hiver et été) dans l'habitat alimenté par un plancher hydraulique réversible. Pour mener à bien cette étude, nous disposons d'un gisement solaire important d'une part et d'autre part d'un dispositif expérimental à échelle réelle. Une pièce munie d'un plancher hydraulique réversible (chauffant ou rafraichissant) est instrumentée. Une citerne de stockage enfuie à quelques mètres de la surface du sol afin de bénéficier du rafraichissement géothermique. Un service d'asservissement permettant la régulation du système en fonctionnement mode chauffage ou mode rafraichissement. Plusieurs sondes de mesures reliées à une station d'acquisition qui est reliée à un ordinateur permettent le suivi des évolutions de températures. La modélisation de la structure de l'enveloppe de la cellule et l'évolution de la température de l'air intérieur et celle des parois sont réalisées sous le logiciel TRNSYS. A l'aide des résultats obtenus par TRNSYS, logiciel FLUENT nous a permis de modéliser la tache solaire et son influence sur le plancher chauffant sous les conditions climatiques de la ville d'Oran.Après validation, la simulation numérique est utilisée pour étudier le comportement thermique de la cellule, les performances énergétiques du plancher réversible et le calcul des économies d'énergie que l'on pourrait réaliser avec de tels systèmes. / This work is part of the search for energy saving solutions in the building industry while using natural and renewable sources, such as solar energy for heating and geothermal energy for refreshment. There is no need to recall that Algeria has a very large geothermal gravitational energy potential in view of its geographical position.In this thesis work, we are particularly interested in the study of thermal comfort in the case of a housing powered with a reversible hydraulic floor (heating and cooling).To carry out this study, as we can see Algeria have an important solar field and on the other hand we use an experimental system representing a real scale local. To do this, a room with a reversible hydraulic floor (heated or refreshing) is instrumented. A storage tank buried in the ground at few meters from the ground surface is used for thegeothermal refreshment during the warm periods. A service system allows us to regulate the system in heating or cooling mode. Several measuring probes used are connected to an acquisition station which is connected to a computer for monitoring of temperature évolutions.The modeling of the structure of the cell envelope is carried out under the TRNSYS software. With this, we have access to evolutions of the temperatures of the indoor air and to that of the walls. These results obtained by TRNSYS are used in a second step as input data for the FLUENT software. This allows us to model the solar spot and its influence on the heating floor under the climatic conditions of the city of Oran.After validation, numerical simulation is used to study the thermal behavior of the cell, the energy performance of the reversible floor and the calculation of the energy savings that could be achieved with such systems.

Ces travaux consistent en l’étude expérimentale et numérique des performances énergétiques d’un prototype de micro-cogénération solaire. L’installation, située sur le campus de l’Université de la Rochelle, fonctionne grâce au couplage d’un champ de capteur solaire cylindro-parabolique de 46,5 m² avec un moteur à vapeur à piston non lubrifié fonctionnant selon le cycle thermodynamique de Hirn. Le système de suivi solaire s’effectue selon deux axes et l’eau est directement évaporée au sein de l’absorbeur des capteurs cylindro-paraboliques. La génération d’électricité est assurée par une génératrice et la récupération des chaleurs fatales doit permettre d’assurer les besoins en chauffage et eau chaude sanitaire d’un bâtiment. La première partie de ces travaux présente les essais réalisés. L’objectif est de réaliser des essais complémentaires pour caractériser le concentrateur solaire, d’étudier les conditions de surchauffe de la vapeur, ainsi que le fonctionnement de l’installation complète en hiver. Ce travail a permis le développement de modèles pour le capteur cylindro-paraboliques, les essais en régime surchauffé ont montré la nécessité d’un appoint pour le fonctionnement d’une telle installation tandis que les essais avec moteur présentent des productions compatibles avec les consommations en électricité et chaleur d’un bâtiment résidentiel. La seconde partie concerne la modélisation des éléments constituant le micro-cogénérateur ainsi que l’intégration de cette installation au bâtiment à l’aide d’un logiciel de simulation thermique dynamique (TRNSYS©). Cette étude propose deux options d’intégration selon le positionnement de l’appoint de chaleur. Pour les deux configurations, des bilans hebdomadaires et annuels sont présentés permettant de discuter les avantages/inconvénients de chaque disposition. Il apparaît que le positionnement de l’appoint sur le circuit primaire permet de piloter la production électrique. L’ajout de l’appoint sur la distribution semble plus facilement réalisable mais empêche le contrôle de la production électrique. / This work consists of the experimental and numerical study of the energy performance of a prototype of solar micro-cogeneration. The facility, located on the campus of the University of La Rochelle, operates by coupling a 46.5 m² parabolic trough solar collector field with an oil-free piston steam engine operating according to the Hirn thermodynamic cycle. The solar tracking system is carried out in two axes and the water is evaporated directly into the absorber of the parabolic trough collectors. Electricity generation is provided by a generator and the recovery of fatal heat must make it possible to meet the heating and domestic hot water needs of a building. The first part of this work presents the tests performed. The objective is to carry out additional tests to characterize the solar concentrator, to study the conditions of steam overheating, as well as the operation of the complete installation in winter. This work has allowed the development of models for the parabolic trough sensor, the tests in overheated mode have shown the need for an extra charge for the operation of such an installation while the tests with motor present productions compatible with the electricity and heat consumption of a residential building. The second part concerns the modelling of the elements constituting the micro-cogenerator as well as the integration of this installation into the building using dynamic thermal simulation software (TRNSYS©). This study proposes two integration options depending on the positioning of the auxiliary heater. For both configurations, weekly and annual reviews are presented to discuss the advantages/disadvantages of each provision. It appears that the positioning of the auxiliary on the primary circuit makes it possible to control the electrical production. The addition of back-up boiler on the distribution seems more easily achievable but prevents the control of power generation.

Thermal energy storage (TES), the storage of heat or cooling, is a cost-effective energy storage technology that can greatly enhance the performance of the energy systems with which it interacts. TES acts as a buffer between transient supply and demand of energy. In solar thermal systems, TES enables the power output of the plant to be effectively regulated, despite fluctuating solar irradiance. In district energy systems, TES can be used to shift loads, allowing the system to avoid or take advantage of peak energy prices. The benefit of TES, however, can be significantly enhanced by dynamically optimizing the complete energy system. The ability of TES to shift loads gives the system newfound degrees of freedom which can be exploited to yield optimal performance. In the hybrid solar thermal/fossil fuel system explored in this work, the use of TES enables the system to extract nearly 50% more solar energy when the system is optimized. This requires relaxing some constraints, such as fixed temperature and power control, and dynamically optimizing the over a one-day time horizon. In a district cooling system, TES can help equipment to run more efficiently, by shifting cooling loads, not only between chillers, but temporally, allowing the system to take advantage of the most efficient times for running this equipment. This work also highlights the use of TES in a district energy system, where heat, cooling and electrical power are generated from central locations. Shifting the cooling load frees up electrical generation capacity, which is used to sell power to the grid at peak prices. The combination of optimization, TES, and participation in the electricity market yields a 16% cost savings. The problems encountered in this work require modeling a diverse range of systems including the TES, the solar power plant, boilers, gas and steam turbines, heat recovery equipment, chillers, and pumps. These problems also require novel solution methods that are efficient and effective at obtaining workable solutions. A simultaneous solution method is used for optimizing the solar power plant, while a static/dynamic decoupling method is used for the district energy system. / text

Solar energy is a virtually inexhaustible energy resource, and thus, has great potential in helping meet many of our future energy requirements. Current technology used for solar energy conversion, however, is not cost effective. In addition, solar thermal power systems are also generally less efficient as compared to fossil fuel based thermal power plants. There is a large variety of systems for solar thermal power generation, each with certain advantages and disadvantages. A distinct advantage of solar thermal power generation systems is that they can be easily integrated with a storage system and/or with an auxiliary heating system (as in hybrid power systems) to provide stable and reliable power. Also, as the power block of a solar thermal plant resembles that of a conventional thermal power plant, most of the equipment and technology used is already well defined, and hence does not require major break through research for effective utilisation. Manufacturing of components, too, can be easily indigenized. A solar collector field is generally used for solar thermal energy conversion. The field converts high grade radiation energy to low grade heat energy, which will inevitably involve energy losses as per the laws of thermodynamics. The 2nd law of thermodynamics requires that a certain amount of heat energy cannot be utilised and has to be rejected as waste heat. This limits the efficiency of solar thermal energy technology. However, in many situations, the waste heat can be effectively utilized to perform refrigeration and desalination using absorption or solid sorption systems, with technologies popularly known as “polygeneration”. There is extensive research done in the area of solar collectors, including but not limiting to thermal analysis, testing of solar collectors, and economic analysis of solar collectors. Exergy and optimization analyses have also been done for certain solar collector configurations. Research on solar thermal power plants includes energy analysis at system level with certain configurations. Research containing analysis with insolation varying throughout the day is limited. Hence, there is scope for analysis incorporating diurnal variation of insolation for a solar thermal power system. This thesis centres on the thermodynamic analysis at system level of a solar thermal power system using a concentrating solar collector field and a simple Rankine cycle power generation (with steam as the working fluid) for Indian conditions. The aim is to develop a tool for thermodynamic analysis of solar thermal power systems, with a generalised approach that can also be used with different solar collector types, different heat transfer fluids in the primary loop, and also different working fluids in the secondary loop. This analysis emphasises the solar collector field and a basic sensible heat storage system, and investigates the various energy and exergy losses present. Comparisons have been made with and without a storage unit and resulting performance issues of solar thermal power plants have been studied. Differences between the system under consideration and commercially used thermal power plants have also been discussed, which brought out certain limitations of the technology currently in use. A solution from an optimization analysis has been utilized and modified for maximization of exergy generated at collector field. The analysis has been done with models incorporating equations using the laws of thermodynamics. MATLAB has been used to program and simulate the models. Solar radiation data used is from NREL’s Indian Solar Resource Data, which is obtained using their SUNY model by interpreting satellite imagery. The performance of the system has been analysed for Bangalore for four different days with different daylight durations, each day having certain differences in the incident solar radiation or insolation received. A particular solution of an optimization analysis has been modified using the simulation model developed and analysed with the objective of maximization of exergy generated at collector field. It has been found that the performance of the solar thermal power system was largely dependent on the variation of incident solar radiation. The storage system provided a stableperformance for short duration interruptions of solar radiation occurred on Autumn Equinox (23-09-2002).The duration of the interruption was within the limits of storage unit capacity. The major disruption in insolation transpired on Summer Solstice (21-06-2002) caused a significantly large drop in the solar thermal system performance; practically the system ceased to function due to lack of energy resource. Hence, the use of an auxiliary heating system hasbeen considered desirable. The absence of a storage unit has been shown to cause a significant loss in gross performance of the power system. The Rankine cycle turbine had many issues coping with a highly fluctuating energy input, and thus caused efficiency losses and even ceased power generation. A storage unit has been found to be ideal for steady power generation purposes. Some commercial configurations may lack a storage system, but they have been compensated by the auxiliary heating system to ensure stable power generation. The optimization of the solar collector determines that optimal collector temperatures vary in accordance to the incident solar radiation. Hence, the collector fluid outlet temperature must not be fixed so as to handle varying insolation for optimal exergy extraction. The optimal temperatures determined for Bangalore are around 576 K which is close to the values obtained by the simulation of the solar thermal power system. The tools for analysis and simulation of solar thermal power plants developed in this thesis is fairly generalised, as it can be adapted for various types of solar collectors and for different working fluids (other than steam), such as for Organic Rankine Cycle (ORC). The model can also be easily extended to other types of power cycles such as Brayton and Stirling cycles.

Recently, the supercritical carbon dioxide (s-CO2) Brayton cycle has been identified as a promising candidate for solar-thermal energy conversion due to its potentially high thermal efficiency (50%, for turbine inlet temperatures of ~ 1000 K). Realization of such a system requires development of solar receivers which can raise the temperature of s-CO2 by over 200 K, to a receiver outlet temperature of 1000 K. Volumetric receivers are an attractive alternative to tubular receivers due to their geometry, functionality and reduced thermal losses. A concept of a ceramic pressurized volumetric receiver for s-CO2 has been developed in this work. Computational Fluid Dynamics (CFD) analysis along with a Discrete Ordinate method (DOM) radiation heat transfer model has been carried out, and the results for temperature distribution in the receiver and the resulting thermal efficiency are presented. Issues regarding material selection for the absorber structure, window, coating, receiver body and insulation are also addressed. A modular small scale prototype with 0.5 kWth solar heat input has been designed. The design of a small scale s-CO2 loop for testing this receiver module is also presented in this work. There is a lot of ongoing investigation for design and simulation of different configurations of heat exchangers and solar receivers using s-CO2 as the working fluid, in which wall temperatures up to 1000 K are encountered. While CO2 is considered to be transparent as far as solar radiation spectrum is concerned, there may be considerable absorption of radiation in the longer wavelength range associated with radiation emission from the heated cavity walls and tubes inside the receivers. An attempt has been made, in this study, to include radiation modelling to capture the effect of absorption bands of s-CO2 and the radiative heat transfer among the equipment surfaces. As a case study, a numerical study has been performed to evaluate the contribution of radiative heat transfer as compared to convection and conduction, for s-CO2 flow through a circular pipe. The intent is to provide a guideline for future research to determine the conditions for which radiation heat transfer modelling inside the pipe can be significant, and what errors can be expected otherwise. The effect of parameters such as Reynolds number, pipe diameter, length to diameter ratio, wall emissivity and total wall heat flux has been studied. The effect of radiation modelling on wall temperatures attained for certain amount of heat flux to be transferred to s-CO2 is also studied. The resulting temperature distribution, in turn, affects the estimation of heat loss to the environment

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