An example of an installation operating without a heat pump is an installation designed by the Technical University of Copenhagen for a single-family house built in 1978 r.
Scheme of a solar installation system for heating domestic hot water. and for central heating: 1 - solar panels, 2 - heat accumulators, 3 - oil heater, 4 — low-temperature radiators, 5 - circulation pumps, 6 - domestic hot water preheating tank, 7 - domestic hot water tank.
The most effective solution is solar systems combined with a heat pump using two heat sources. In this system, the pump has two evaporators, one located in the storage tank or its circuit, and the other outside the building, np. in the ground, in a tank with wastewater from the building, in ventilation ducts that discharge warm air to the outside, in external natural or artificial bodies of water, etc. At the same time, a solar heating system can be solved like this, that excess heat energy (in summer) will be transferred to this heat source, that the heat pump evaporator uses in winter.
Scheme of the heating installation in the BBC experimental building in Walldorf: 1- oil boiler, 2 - floor heating, 3 - solar panels, 4 - heat exchanger, 5 - heat accumulator, 6 - heat pump, 7 - hot water heater, 8 - a coil in the ground.
Such extensive systems cover from 50 do 80% annual heat demand.