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The measured performance of seven low-cost solar water heating systems in the San Luis Valley of southern Colorado is summarized. During the summer and fall of 1981, SERI monitored a variety of low-cost solar water heating system designs and components. Five systems had site-built collectors, and four included low-cost tank-in-jacket heat exchanger/storage tank components. Two were air-to-water systems. The five liquid-based systems included a drain-down design, a propylene glycol-charged thermosiphon system, and three pumped-glycol systems. The pumped-liquid systems performed the best, with system efficiencies greater than 20% and solar fractions between 40% and 70%. Tjhe air-to-water systems did not perform as well because of leakage in the collectors and heat exchangers. The thermosiphon system performed at lower efficiency because the collector flows were low.

Measured performance results: low-cost solar water heating systems in the San Luis Valley