Conventional Flat Plate Solar Collector Research Articles

Calculation of flat-plate collector utilizability

The “utilizability” or φ-curve method developed by Whillier [1] and later generalized by Liu and Jordan[2, 3], can be a very useful design tool for some types of solar energy systems which utilize conventional flat-plate solar collectors. The generalized φ-curve method in its original form, however, has several drawbacks. The calculation effort required to assess long-term collector performance is significant. The calculations can not be completely automated on a computer or hand calculator because many graphs are needed for which analytical representations are not available. In this paper, the φ-curve method is reviewed and situations for which the method is useful are described. Then, an easier method, using daily φ -charts, rather than the original hourly φ-curves, is presented. The φ -charts greatly reduce the calculations required to determine flat-plate collector utilizability. φ -charts can be easily implemented on a programmable hand calculator. A comparison of the original hourly and the new daily calculation methods is presented. An example demonstrating the use and utility of the φ -charts is also included.