Effect of working fluids on the efficiency of low-temperature solar-thermal-electric power generation system

The low-temperature solar-thermal-electric power generation system with two-stage evaporators of liquid-area evaporator and saturated-area evaporator was modularized. The relation between the liquid-heat exchanger thermal efficiency and the mass ratio of heat transfer fluid to organic fluid was studied. With the optimum mass ratio the influence of each organic fluid on the total thermal efficiency of collectors was shown. The result indicated that when the evaporation temperature for all the organic fluids is kept constant, the fluid with smaller ratio of the latent heat to the heat needed for liquid-temperature increasing can lead to higher thermal efficiency of the collectors. The influence of organic fluids on the efficiency of collectors is not consistent with that on thermal efficiency of ORC and the fluid that achieves the highest ORC efficiency isn't able to gain the highest efficiency of collectors. Among the researched organic fluids, R113 is the most effective one and the maximum efficiency is 8.0% with an insolation of 750 W/m2.