Use of R-114 as the working fluid in a flat-plate collector system for electric power generation

Abstract

The use of flat-plate solar collectors for the generation of electric power is attracting the attention of engineers and scientists for its simplicity in construction and operation. The efficiency of collection is low due to the low operating temperatures of the flat-plate collectors. In the low temperature range applicable to flat-plate collectors, refrigerants can be used as working fluid. The cost of construction can be reduced by the suitable selection of collector and refrigerants. It has been shown that R-114 has suitable characteristics for use as a Rankine cycle working fluid. By using an aluminium tube-plate type collector with 0·005 m tube diameter, 10 risers per metre width of collector, it becomes light and cheap. When the emissivity of the collector is 0·1 and a single cover is used, the maximum efficiency condition is attained. Limited to a pressure drop of 2·5 bar in the collector, 16 collectors can be used in series and the overall efficiency can be as high as 7·8% under 1000 W/m 2 insolation conditions and for an outlet temperature of 380 K. Under these conditions 5600 collectors of 1·5 m × 1·5 m size will be required to produce 1000 kW of electricity.