To compare the dynamic operation of the ISAHP system with the steady-state computer model [4], a 6 hour test with varying glycol temperature was performed. Due to stratification, the temperature at the bottom of the tank remained constant throughout the test providing a constant input temperature for the condenser on the water side. A description of the experiments performed is given below.

1.2. Test Sequence

For the simulated solar day test, the heat out of the auxiliary heater was varied in a sinusoidal profile similar to that occurring on a clear sunny day. The following procedure was followed for the test:

• Prior to testing the storage tank was filled with water at mains temperature to ensure that the entire tank was at constant temperature.

• During this time the collector loop fluid was brought to the desired initial temperature for the test, and the loop flow rate was set to 77 kg/h (0.021 kg/s). This flow rate was used in the simulations previously undertaken, and is based on recommendations by Fanney and Klein [14].

• The data acquisition (DA) system was initialized with the compressor running, and the program delivering the power profile to the heaters was commenced. Data was recorded every 5 seconds for the duration of the experiment.

• COP and natural convection flow rate were then calculated based on the collected data.