Using either the heat pump for heating at solar-assisted mode or the biomass boiler for CHP
At moments with solar energy availability, the pump of the solar field is controlled to reduce the temperature of the solar heat at up to 65 oC, and thus increase the collector efficiency at cold conditions. This heat is stored and is used as follows, according to its temperature:
Heat at 65 oC is used for (1) DHW, and (2) space heating at up to 45 oC. In buildings with no DHW needs, the solar heat temperature is reduced to 50 oC for space heating only, further enhancing the collector efficiency.
Heat at very low temperature (5 < T < 30 oC) supplies the evaporator of the electric HP for assisting the heating production and increasing its COP to over 4.5, reaching 5 in south Europe.
At moments with no solar energy availability or higher heating needs than the heat pump production, the biomass boiler operates to cover the excess of heating demand, by operating at CHP mode.