The maximum efficiency value was 82%. For a detached house, which is a typical application for the solar collector, an efficiency of approximately 75% is reached. The efficiency curve equation is: h = 81.9 – 0.0149(Tm – Tamb) – 0.000429(Tm – Tamb)2. The resulting efficiency here is achieved when solar radiant power is 930 W/m2; in a bright summer day the maximum efficiency of solar radiant power is 1 000 W/m2. The efficiency is calculated according to the active area of the collector. In the graph below, it is indicated with the uppermost curve. The curve lower down depicts the efficiency calculated in relation to the collector’s gross area.
The testing examined the performance and efficiency of the solar collector.
Efficiency was measured for four different temperature levels in standard laboratory conditions. Water with a flow speed of 1.5 litres per minute was used as circulation liquid in the test. The testing method is based on the ASHRAE 93-77 and EN 12975-2 standards.