Long-term (18 years) performance of a residential solar heating system

Abstract

The long-term performance of a residential solar heating system has been determined for a system which has been operating continuously since 1957 with no maintenance. This residential solar heating system is the Colorado Solar House located in Denver, Colorado, designed and operated by George O. G. Löf. The performance of this system was determined during the 1959–1960 heating season, and the results were publised. The performance of this system was redetermined during the 1974–1975 heating season so that changes in performance occurring over a period of 15 yr could be determined. The collector is an Overlapped-Glass Plate Solar-Air Heater. The system is completely automatic with provision for water heating in addition to space heating. Solar heat is stored in a rock bed of primarily granitic rock approximately 1.3–2.5 cm in diameter. The ratio of useful collected solar heat divided by the total solar radiation on the collector dropped to 71.8 per cent of its original value in 15 yr. For both seasons, the useful collected solar heat was correlated with the ratio of degree days per month divided by the total solar radiation on the collector. For the same value of this ratio, less useful collected solar heat was delivered during the latter season. Additional work that will be published at a later date includes the detailed performance of the hot water heating system.