A REALISTIC HOT WATER DRAW SPECIFICATION FOR RATING SOLAR WATER HEATERS

摘要

In the United States, annual performance ratings for solar water heaters are simulated, using TMY weather and specified water draw. Bias stemming from lack of realism in the current ratings draw includes: i) low flow rates boost performance for systems with load-side heat exchangers; ii) low mains temperature boosts performance for all solar water heaters; and iii) an invariant draw profile can't properly credit larger vs. smaller storage volumes and doesn't portray realistic variations south to north. A more-realistic ratings draw is proposed that eliminates most bias by improving mains inlet temperature and by specifying realistic hot water use. This paper outlines the current and the proposed draws and estimates how much ratings will be affected for draw specification changes for typical systems in four cities. Average change in the ratings from the proposed draw is ～8%.