SIMPLE AND ACCURATE METHOD TO EVALUATE THE TIME-AVERAGED PERFORMANCE OF FLAT-PLATE SOLAR COLLECTORS

The article demonstrates an improved version of a method that the auth ors developed over the last IO years. The method has two stages. First , computational procedures, graphs, and tables are presented for the a verage day of a given time period and for a specific reference state o f the collector (horizontal position and the working fluid average tem perature kept constant during the day). Then procedures are developed to use these graphs and cables for different cloud cover classes of da y and collector states characterized by any tilt, orientation, and the rmal condition and for operational regimes. The central concept of the method is the noon equivalent time, which plays a role similar to tha t of utilizability in other computational methods. The required tables and graphs must be presented all at once for a given location and tim e period. Toward this aim, detailed data are needed on the dependence of solar global irradiance on tilt and orientation and cloud cover. Se veral computational examples are shown.