SSHP. The SSHP model was prepared as a polynomial approximation model based on experimental data.
The WHP was modelled as a polynomial approximation model similar to the SSHP model, by using the data provided by the manufacturer.
Calculation was carried out to reproduce the second day of the experiment, and the heating load of the WHP and outdoor air conditions were input in accordance with the operating schedule of the experiment for both the WHP and SSHP. In this simulation the ground temperature distribution was not considered but was assumed to be a uniform temperature.
The heat source water inlet and outlet temperatures for the SSHP and ground heat exchangers are shown in Figure 6(a) and (b).
The simulation model was verified only in heating operation, but it can be applied to an annual simulation because the SSHP operates only for heating, the GHEX has the same performance in both heating and cooling operation, and the WHP was modelled based on the specification data of all operation mode provided by the manufacturer.
The heating load is shared between the SSHP and the ground heat.
The SSHP module employed a drainer as an expansion device, which drained liquid refrigerant without passage of high-pressure gas and showed no superheating at the outlet of the evaporator.
Daily charge or discharge of the ground heat with the SSHP allows high-density and compact GHX because the thermal penetration distance is a few tens of centimeters; one digit shorter than annual restoration that is common to the conventional ground source heat pumps.
Antifreeze solution was not used because heating with the SSHP protected the loop water from freezing.
It followed the heat charging with the SSHP to restore the soil temperature up to the undisturbed ground temperature (i.e.
At night, the SSHP cooled the soil down to the undisturbed ground temperature (i.e.
The grounds of the target are that COP of each water-source heat pump was about 8 and will be further improved, a DC water pump dedicated to each heat pump consumed less than 10% of the compressor, and the SSHP will be able to compensate its consumption with generation of its own PV cells on an annual integration basis.