SIMULATION OF SOLAR AIR HEATING AT CONSTANT-TEMPERATURE

Solar space heating with warm air in typical air collectors and rock bed storage systems involves constant air now rates and varying the temperature of supply to roams and to storage. This practice results in undesirable fluctuations in comfort levels in the living space, excessive storage size, useful but inaccessible heat in storage, and unnecessarily high energy consumption for air circulation and auxiliary heat. These drawbacks can be avoided by use of a practical controller and variable speed fan to provide heated air from the collector at constant temperature and a continually varying now rate. Collector manufacturer's data, confirmed by seasonal tests on a solar air heating system in Solar House II at Colorado State University, have been used in simulations at constant hot air supply temperatures of 40 degrees, 50 degrees, and 60 degrees C, and at one typical constant flow rate of 49 kg/h per m(2) through a 50 m(2) collector and rock bed storage unit, providing approximately half the seasonal heating requirements of a residential building. Auxiliary heat requirements and fan power use in the 40 degrees C and 50 degrees C constant temperature operations were significantly reduced from the levels prevailing under constant flow conditions. Collection efficiency and solar heat supply at constant now were slightly higher than values at the 60 degrees C constant temperature level.