Global optimization of solar thermal power system

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Research on global optimization of space solar thermal power system

Wu Yuting 1,2, Ren Jianxun 1, Guo Zengyuan 1, Liang Xingang 1

(1. Department of engineering mechanics, Tsinghua University, Beijing 100084; 2. School of environmental and energy engineering, Beijing University of technology, Beijing 100022)

1 introduction

power generation system is an important part of the space station, which is used for life support, control Management and production test activities need not be due to its extremely low density and less material conditions. Solar thermal power generation system has the characteristics of high energy conversion efficiency, small weight and resistance area. For low orbit space stations with large demand for electric energy, the system can not only meet the requirements of electric energy, but also greatly reduce the operation cost, and has a good application prospect [1]. As early as the early 1960s, Garrett company of the United States studied the space solar thermal power generation system, trial produced major components, and carried out a large number of component tests. 3 Test of making the middle beam run in the opposite direction [2]. At present, the United States, Russia, Japan and Europe are actively carrying out research on space solar thermal power generation systems [3~5]. The domestic research on this system has just started, mainly focusing on the development of various components of the system [6]. From the perspective of system, the research on the optimal configuration of structure and operating parameters in solar thermal power generation system is still lack of in-depth research in China

The launch, management and support costs of the space station are extremely high, so it is of great significance to reduce its weight and operational supplies. There are many factors that affect the weight and size of the solar thermal power system, and its impact on each component of the system also has positive and negative effects. Therefore, it is of great practical significance to comprehensively optimize the space solar thermal power generation system and seek the optimal scheme of the system for reducing the launch and operation cost of the space station

2 system composition and working process

suitable for space solar thermal power generation system, there are three types of power cycles to choose from, namely Rankine cycle, closed Brayton cycle and Stirling cycle. Among the three cycle schemes, Rankine cycle has the lowest efficiency and Stirling cycle has the highest efficiency, but its technology is immature. The closed Brayton cycle has relatively high thermal efficiency, and the experience of small gas turbine and aircraft gas turbine engine on the ground can be used for reference, so it is considered to be the most promising cycle scheme [7,8]. Accordingly, this paper also takes the closed Brayton cycle solar thermal power generation system as an example (hereinafter referred to as SCBC system) for optimization research, and its system composition is shown in Figure 1. The system mainly includes the following main components: energy concentrator, heat receiver, energy converter (composed of coaxial turbine, generator and compressor) and radiation radiator. Its working process is: during the sunshine period of the track, solar radiation is focused by the concentrator and enters the heat receiver/heat accumulator through the cavity of the heat receiver/heat accumulator. Part of the heat is used to heat the circulating working medium, and the other part is stored in the heat receiver/heat accumulator. Then the high-temperature circulating working medium expands in the turbine to do work, converting heat energy into mechanical energy, and driving the generator to rotate at the same time, so as to convert mechanical energy into electrical energy. The low-pressure circulating working medium releases part of the remaining heat to the high-pressure working medium from the compressor through the regenerator. Then the waste heat is further discharged to the space through the radiation radiator. The cooled working medium enters the compressor and is preheated by the regenerator after compression, and then enters the endothermic/regenerator to complete an actual cycle. In the orbital shadow period, the heat stored in the endothermic/regenerator heats the circulating working medium. 3 system evaluation criteria

in the study of SCBC system performance, some literatures have studied the cycle efficiency, specific work, device weight and radiation area as objectives [8~10]. Because the solar energy is naturally obtained in the space solar thermal power generation device, which is equivalent to the free fuel in the ground system, the cycle efficiency cannot directly reflect the economy of the system operation. Ground tests have shown that in the SCBC system, the size of the energy conversion unit (compressor, turbine, motor) is much smaller than that of the collector and radiator. The specific work only reflects the specific mass of the energy conversion unit, not the size or mass of the whole system, let alone the economy of the whole device

the area of the radiator is a very important parameter in the SCBC system. It can reflect the size and weight of the device to a certain extent. However, using only the area of the radiator as the evaluation standard of the SCBC system is not comprehensive and cannot fully reflect the many factors and characteristics involved in the SCBC system as a space power device

system quality is a very important parameter, which can reflect the production and partial launch cost of space power plant, but only using system quality as the evaluation criterion cannot reflect the total cost of the system. Because the power station flies in orbit with the space station, the power generation system has a considerable resistance area. The space station is affected by the aerodynamic resistance of this area, and its flight height gradually decreases. To raise the working piston to maintain the orbital height, the thrust generated by the engine in the space station is needed to offset the aerodynamic resistance, and the propellant consumed by the engine needs to be transported from the ground to the space station. Therefore, we must comprehensively consider the weight and resistance area of the system in order to fully reflect the total cost of the system. Therefore, this paper presents the evaluation criteria of total launch weight. This optimization criterion converts the resistance area into the weight of the required propellant, so that the resistance area and the weight of the system are unified into an evaluation criterion, which is convenient for use and comprehensively considers the economic performance of the system

space solar thermal

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