This refers to passive solar collector, where solar radiation is used to heat water. It is therefore not on the solar cells.
What characteristics should solar collectors have, to function in an optimal way?
Why should these properties be fulfilled?
If there is a water flow of 500 g / minute to a solar panel on one m2, how much water is heated up under optimal conditions during the passage of the collector? Expect that the collector is in Gothenburg and the calculation is done for one day in mid-June (noon)