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Analysis of Advanced Supercritical Carbon Dioxide Power Cycles for Concentrated Solar Power ApplicationsMostaghim Besarati, Saeb 31 October 2014 (has links)
Solar power tower technology can achieve higher temperatures than the most common commercial technology using parabolic troughs. In order to take advantage of higher temperatures, new power cycles are needed for generating power at higher efficiencies. Supercritical carbon dioxide (S-CO2) power cycle is one of the alternatives that have been proposed for the future concentrated solar power (CSP) plants due to its high efficiency. On the other hand, carbon dioxide can also be a replacement for current heat transfer fluids (HTFs), i.e. oil, molten salt, and steam. The main disadvantages of the current HTFs are maximum operating temperature limit, required freeze protection units, and complex control systems. However, the main challenge about utilizing s-CO2 as the HTF is to design a receiver that can operate at high operating pressure (about 20 MPa) while maintaining excellent thermal performance. The existing tubular and windowed receivers are not suitable for this application; therefore, an innovative design is required to provide appropriate performance as well as mechanical strength.
This research investigates the application of s-CO2 in solar power tower plants. First, a computationally efficient method is developed for designing the heliostat field in a solar power tower plant. Then, an innovative numerical approach is introduced to distribute the heat flux uniformly on the receiver surface. Next, different power cycles utilizing s-CO2 as the working fluid are analyzed. It is shown that including an appropriate bottoming cycle can further increase the power cycle efficiency. In the next step, a thermal receiver is designed based on compact heat exchanger (CHE) technology utilizing s-CO2 as the HTF. Finally, a 3MWth cavity receiver is designed using the CHE receivers as individual panels receiving solar flux from the heliostat field. Convective and radiative heat transfer models are employed to calculate bulk fluid and surface temperatures. The receiver efficiency is obtained as 80%, which can be further improved by optimizing the geometry of the cavity.
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Optimization of a SEGS solar field for cost effective power outputBialobrzeski, Robert Wetherill 10 July 2007 (has links)
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.
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Système de refroidissement sec et de production d'eau pour centrale électrosolaire thermodynamique à cycle de Rankine / Dry cooling and water producing system for Rankine cycle concentrated solar power processesEspargilliere, Harold 08 March 2017 (has links)
Les centrales solaires à concentration industrielles consomment 4 m3/MWh d’eau pour le refroidissement de leur cycle thermodynamique. En environnement aride, cela est susceptible d'induire des conflits d’usages sur une ressource encore plus fondamentale que l’électricité, l'eau. Ce constat met en évidence la nécessité de concevoir des solutions alternatives de refroidissement sèches mais tout aussi efficaces. Le champ solaire d’une centrale CSP représente 50% de son coût d’investissement pour n’être utilisé que de jour pour la production de chaleur nécessaire au cycle thermodynamique. L'approche du sujet de thèse consiste à utiliser cette surface considérable comme macro-échangeur de chaleur avec son environnement via un transfert thermique couplé avec l'air ambiant (convectif) et avec l'espace extra-atmosphérique à 3K (radiatif). Après avoir démontré la pertinence des matériaux du champ solaire pour une telle application, le travail de thèse a montré expérimentalement qu'au-delà d'extraire les chaleurs fatales du cycle thermodynamique, il pouvait aussi produire du froid par transfert radiatif nocturne. Une solution alternative innovante pour le refroidissement des centrales solaires CSP offrant deux nouvelles fonctionnalités à leur champ solaire déjà existant au bénéfice de son amortissement. / Industrial concentrated solar power plants consume 4 m3/MWh of water to cool down their thermodynamic cycle. In arid area, it could induce conflicts of use on a more fundamental resource than electricity. This fact highlights the need to develop alternatives dry cooling technologies but equally effective. The solar field represents 50% of the investment cost of a CSP plant to be used only daily for the heat production needed for the thermodynamic cycle. The approach of the project is to use this huge area as macro-heat exchanger with its surrounding environment through a coupled heat transfer with the ambient air (convective) and with outer space at 3K (radiative). After validating the compatibility of solar field materials for a such application, these research works has shown experimentally that in addition to extract the waste heat of the thermodynamic cycle, it could also produce cold by night radiative cooling. An innovative alternative solution for cooling CSP plants offering two new features to their already existing solar field for the benefit of its paying off.
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[en] NUMERICAL SIMULATION OF A HYBRID CONCENTRATED SOLAR POWER PLANT / [pt] SIMULAÇÃO DE UMA USINA HÍBRIDA TERMOSSOLARBERNARDO WEBER LANDIM MARQUES 11 May 2020 (has links)
[pt] O presente trabalho consiste na integração de um campo solar em uma usina
de gaseificação de resíduos sólidos urbanos no município de Boa Esperança em
Minas Gerais. Os resíduos sólidos acumulados no lixão da cidade são utilizados
como insumos para a geração de gás de síntese no reator químico da unidade. Esta
operação recupera a extensa área degradada deste vertedouro permitindo a
instalação do campo solar com coletores de calhas parabólicas. O intuito do projeto
é o fornecimento contínuo de calor pelo campo solar através da instalação de
tanques de armazenamento direto de calor. A operação do campo solar é simulada
pela elaboração de uma rotina computacional no software Matlab através do método
das diferenças finitas unidimensional. A solução numérica do sistema de equações
diferenciais que compõe o balanço de energia do receptor solar é validada pela
comparação com o teste experimental do Laboratório Nacional de Sandia do
concentrador solar SEGS LS-2 com tubo absorvedor evacuado. Além disso, o
controle da vazão mássica circulante pelo campo solar é incorporado na lógica
computacional de modo que a temperatura na saída do campo solar seja mantida
com valores próximo ao set-point de 390 graus Celsius. Portanto, as simulações
computacionais com proposições sobre a partida e operação do campo solar são
testadas para dias ensolarados do ano meteorológico típico de Boa Esperança.
Finalmente, um dia real com nebulosidade é simulado para a análise do
funcionamento do campo solar de acordo com a variação intermitente da irradiância
direta normal. Os resultados da operação do dia real são utilizados como base para
a aplicação da presente rotina computacional em futuros projetos do campo solar. / [en] This work intends to hybridize a solar field into the current waste to energy
gasification power plant in Boa Esperança in Minas Gerais. The gasification
process converts municipal solid waste to usable synthesis gas for electrical
production. This current operation of waste to energy power plant removes waste
accumulated from the landfill site. It recovers an extensive area for future solar field
installation due to this available space without any waste in the future. The design
of the planned solar field comprises the parabolic trough concentrating systems.
The aim of the solar design is to provide ongoing heat to the power block with direct
storage tanks. The solar field operation is simulated by the development of a Matlab
computer program based one dimensional implicit difference method with energy
balance approach of an evacuated receiver. The validation of present model was
done by comparing the outlet temperatures of simulation results and the
experimental data obtained by Sandia National Laboratories. Moreover, the mass
flow rate is regulated through the field to make sure that the outlet temperature from
the solar collector is kept as close to the desired 390 Celsius Degree as possible. To accomplish
the main purpose of the work, many different computational models with start-up
and full operation stages are suggested for different clear days along the typical
meteorological year of the city Boa Esperança. Eventually, a cloud day with a real
meteorological data was chosen for a computational model of the solar field
performance. All results of the real day operation are used to improve the computer
program of the present work. These results are useful for future solar field design.
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