The maximum efficiency value was 89%. For a detached house, which is a typical application for the solar collector, an efficiency of approximately 74% is reached. The efficiency curve equation is: h = 89.4 – 0.206(Tm – Tamb) – 0.0047(Tm – Tamb)2. The resulting efficiency here is achieved when solar radiant power is 870 W/m2 and efficiency is calculated in relation to the absorber (black collector surface) area. In a bright summer day, the sun’s maximum irradiance is 1 000 W/m2.
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 3.5 litres per minute (106 kg/h/m2) was used as circulation liquid in the test. The effect of wind was neglected in this test. The testing method is based on the ASHRAE 93-77 and EN 12975-2 standards.