Control problems in solar domestic hot water systems

Abstract The settings on the controller for a solar domestic hot water system can have major impact on the “ratings” obtained from a 1-day test or simulation. The settings become more critical as the effectiveness of any freeze protection heat exchanger decreases. This paper develops equations for optimal controller settings that will maximize the simulated performance. The practice of using solar radiation that is constant over hourly periods in both experimental- and simulation-based rating procedures is shown to cause problems. Recommendations are made for controller settings that yield a “fair” rating comparison.