Model calibration from short-term test data for unpressurized integral-collector-storage systems

A method of test is defined and instantiated for integral-collector-storage solar systems with a load-side heat exchanger immersed in the storage. A "system test/model calibration" approach is used. The test protocol consists of short-term tests and an extended validation test. Short-term tests include warmup tests, a decay test, and heat exchanger tests. The model parameters to be determined are the normal incidence transmission-absorption product, an additive correction to the total heat loss, and heat exchanger parameters correlating the ratio of modeled to measured heat exchanger fluxes. The calibrated system model resulting from the short-term tests is then validated against typical operation data. The calibrated model presented here under-predicts delivered energy over a 5-day period of normal operation by 11%, perhaps because of the present lack of modeling for the tank stratification induced during charging by solar radiation.