When using solar-assisted heat pumps in heating systems, there is the matter of optimizing the conditions of the combined heat pump system, namely, determining the optimal degree of cooling of the medium in the HP evaporator.
The thermal energy obtained from these sources is accumulated in the tank-accumulator and is used when it is required to provide heat to the HWS.
A heat exchanger is installed between the solar collector and the tank-accumulator, in which the salt solution is additionally cooled with cold water that allows the efficiency of the solar collector to be increased. In the evaporator, the solution is cooled to an outlet temperature t brine output. is fed by the pump from the ground collector to the evaporator of the heat pump. The solution with temperature t brine input and volumetric flow rate V GHE. The solution from a solar collector is pumped to the HP condenser where it is heated up to the required temperature in conjunction with the soil heat which is absorbed by an anti-freeze heat-carrier flowing through the pipes of the ground collector. The conversion of incident solar radiation into heat energy is carried out in flat-plate solar collectors in which an aqueous solution of ethylene glycol is used as a heat-carrier, while the accumulating medium is water. The operating principle of this system is as follows. C, compressor C HP, condenser E HP, evaporator ET, expansion tank GHE, ground heat exchanger HE, heat exchanger HWS, hot water supply L C, work input for HP compressor drive L LC, work input for pump drive in the lower HP circuit L UC, work input for pump drive in the upper HP circuit P, pump SC, solar collector TA, tank/accumulator. Schematic diagram of a combined heat pump unit using soil heat and solar energy.
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