The Model Building And Optimization Study Of The Dish Stirling Solar Thermal Power Geration System

As the problem of the world fossil energy exhausting and causing the environmental pollution and ecological destruction highlights, the world becomes increasing emphasis on solar, biomass, wind energy, and other renewable exploitation.Solar thermal power generation technology is scale as a way of development and utilization of solar energy, so it has a broad development prospects.Contrast with the Tower and Trough solar thermal power generation system,the dish solar thermal power generation system has the simple structure,the flexible layout,the high power efficiency,the high system optimization and cost reduction potential,the little initial investment,the widely application foreground and et al,thus it becomes the focus of the research at home and abroad.Dish stirling solar thermal power generation is a way of the dish solar thermal power generation technology.Due to the dish stirling solar thermal power generation technology starting lately and the manufacturing technology of stirling engine demanding high,so the research of the dish stirling solar thermal power generation system is little. This topic firstly put forward a new kind of the modified cavity receiver, on the basis of analysising the performance of the new cavity receiver, establishes the thermal resistance network model of the 25kW dish stirling solar thermal power generation system contains the new cavity receiver,and the studys the steady state and dynamic thermal performance of the 25kW dish stirling solar thermal power generation system.The main research of this subject is as follows:1.The heat loss of the cavity receiver has a large proportion of the dish stirling solar thermal power generation system,and the convective and radiative heat losses are the main heal losses of the cavity receiver. Therefore,this paper general considers the convective and radiative heat losses,optimizes the inlet structure and shape of the cavity receiver,and then proposes a new kind of modified cavity receiver, establishes the thermal resistance network model of the 25kW dish stirling solar thermal power generation system contains the new cavity receiver. Thermal resistance network model mainly includes the equivalent thermal resistance model of concentrator, the equivalent thermal resistance model of receiver and the equivalent thermal resistance model of stirling engine. Contrast with the cylindrical cavity receiver,the convective and radiative heat losses of the modified cavity receiver are 56.3% and 38.6% of that of the cylindrical receiver, and the total heat loss is only 40% of the cylindrical receiver.This new dish stirling solar thermal power generation system had improved efficiency, it can reach 35.5%, 5.9% higher than that of the dish stirling solar power generation system with the cylindrical cavity receiver. The major difference between the modified cavity receiver and the conventional cylindrical receiver is the ratio of Aw/A1. For a cylindrical cavity, the convective heat loss and the radiative heat loss increase with the increase of Aw/A1.But, for the modified hemispherical cavity, the convective heat loss and the radiative heat loss decrease with the increase of Aw/A1. The losses in concentrator contribute to over 26% of total losses. Thus, after optimization of the cavity receiver, concentrator is in dire need of optimization.2.In the thermodynamic models of the optimized system, considering the influence of solar radiation intensity changes and environmental factor, this paper analysises the dynamic performance of the new 25kW Dish stirling solar thermal power generation system,and then studys the optical error of dish concentrator and concentration ratio influence on the performance of the whole system.The results showed this system start up strength is 474.447 W/m2,and the actual working hours of whole system is from 8:00 to 16:00. System peak output power and efficiency appears at 12:00 p.m, the output power is about 32.5 kW, and the efficiency close to 36%. The whole system in 11:00 to the peak will stage in design, the system output power stable stage in 32 kW or so, efficiency close to 35%. The whole system in 11:00 to 13:00 stage the peak in design, the system output power stable stage in 32 kW or so, and the efficiency close to 35%. Output power and efficiency of the system will decrease with the increase of the error of the dish concentrator,so in order to ensure the performance of the system, the slope error of dish concentrator should be controlled in 2mrad,and other error of dish concentrator also should be controlled in 4mrad.With the increasing of the concentrator ratio,the output power and efficiency of the system will gradually raise, but rising trend will become slowly.Therefore, for this system, the concentrator ratio should be controlled between 750 and 1000.The innovation points of this topic is as follows:1. The convective and radiative heat losses are the main heal losses of the cavity receiver.Therefore,this paper general considers the convective and radiative heat losses,optimizes the inlet structure and shape of the cavity receiver,and then proposes a new kind of modified cavity receiver.2 Establishes the thermal resistance network model of the 25kW Dish stirling solar thermal power generation system contains the new modified cavity receiver,and reveals the thermal performance of steady and dynamic state.The Dish stirling solar thermal power generation system is one of the solar thermal power generation system which has the simple structure,the flexible layout,the high power efficiency,the high system optimization and cost reduction potential,the little initial investment,the widely application foreground.The research about this system is rarely at home and abroad. The research of this topic has great academic value for dish stirling solar thermal power generation system,and has important reference value for experimental demonstration and application of the dish stirling solar thermal power generation system.