The test procedure include the measurement of: (a) climatic parameters such as global solar irradiance on the collector plane, ambient temperature, wind direction and speed; (b) energy consumption of pumps, electronic valves and controls included in the test system and (c) operational parameters such as orientation and inclination of solar collector, initial inlet water temperature, outlet water temperature, and flow rate.

These parameters allow evaluating increase or decrease of water temperature, available energy transferred to the water during the operation period, average thermal efficiency, steady-state thermal efficiency, instantaneous efficiency, etc.

1.1.1 Average solar irradiance

In order to evaluate the average solar irradiance on the collector plane, the following equation is used

n T

.=1 n