Optimal sizing of solar collectors by the method of relative areas

Abstract

A method is presented for calculating directly, without iteration, the approximate collector area which minimizes the total life-cycle cost of an active solar space and/or domestic hot water heating system. The method is based on an empirical relationship between annual solar load fraction and relative collector area. This relationship was determined by correlating data that were generated by the Klein, Beckman and Duffie F-Chart program, which in turn is based on a correlation of digital computer simulation results. The calculations may be performed in a few minutes using a hand-held calculator. Required data are tabulated for 170 locations, and a solved example is included. Compared to results from the F-chart program, deviations of total life-cycle costs from the minima are typically less than 3 per cent. Uncertainty of future energy prices is regarded as the limiting factor in the accuracy of the optimization calculations. A detailed economic analysis is included.