Why is the solar fraction not increasing, even if I still continue to increase the solar collector area?

The yield of the collector circuit is delivered to the tank. Above a certain size, an increase of the collector area causes that the energy input in the tank is greater than the demand and the tank is heated above the required temperature. At 90°C the collector circuit is turned off. A portion of the yield of the solar system is not used to meet the requirements, but there are increased tank losses generated. These “solar tank losses” are presented on the results page. For optimum sizing of the solar system you have to vary the size of the collector area, the tilt angle and the tank size. Design criteria are efficiency, solar fraction and the solar tank losses.