An outdoor comparison performance test of two solar air-heating systems was performed between January 7, 1987 and May 23, 1987, near Potsdam, NY. Each system was installed in a small test cell and was equipped with phase change energy storage (PCES). A third test cell, identical except for having no solar heating system installed, served as a control Infiltration air was blown into the cells at 0.5 air changes per hour (ach). System Control ranges of 68°F-72°F (20°C-22.2°C), 65°F.75°F (18.3°C-23.9°C) and 65°F-80°F (18.3°C-26,7°C) were employed in rotation during the test. The auxiliary heaters were controlled at the lower temperature. The solarheated air was sent directly to the test cell if the cell air temperature was below the higher temperature, otherwise it was sent to the PCES.

The average solar fractions obtained for each control band ranged from 0.42 to 0.48. These values were significantly higher than those obtained in a previous test without storage reported in Thacher and Wen (1987). The average solar fraction of both cells was smallest in the 65°F-75°F (18.3°C-23.9°C) control range and largest the 68°F-72°F (20°C-22.2°C) control range. We recommend that the high and low system control temperature setpoints should be as low as possible to maximize the energy discharge rate of the PCES units.