Evaluation of the flat-plate solar collector system for electric power generation

Abstract

The simplest method of utilizing the energy of the sun to generate electric power is to use a flat-plate collector system. Flat-plate collectors have no tracking mechanism, make use of both direct and diffuse radiation, have no focusing arrangements and are less costly per square foot than parabolic trough collectors, paraboloid of revolution collectors or heliostats. The main disadvantage to the flat-plate collector system is the relatively low temperatures reached by the collector surface (∼ 300°F maximum). This evaluation of the flat-plate collector system was designed to determine the number of flat-plate collectors required to generate a given amount of electricity with optimum efficiency. Variable parameters are the temperature of the heat transport fluid, both to and from the collector field. In the analysis, the efficiency of the flat-plate collectors was coupled to the efficiency of the thermal cycle to calculate optimal overall system effeciencies. Overall system efficiencies for the system are on the order of 3·5 per cent or less. Over two million 4 ft by 4 ft collectors would be required to produce 100,000 kW(e). Based on the results of this analsis, it can be shown that the limiting factor in the use of the flat-plate collector system for electric power generation is the efficiency of the collectors. An increase in the overall system efficiency can occur only if the collector efficiency can be increased at the higher surface tempertures.