Integrate a solar thermal system with a ground source heat pump to complemente each other’s strengths

(22/09/2009)

Solar thermal heating is most effective in the summer months and ground source heat pumps used for central heating work particularly well in winter. By integrating the two technologies, you can get a sum that is greater than the parts. Murray Treece, Managing Director of Econic, explains:

Solar thermal systems offer simple but effective domestic water heating – particularly in the summer when the sun shines – and they are capable of raising the water well above boiling point. Heat pumps, on the other hand, are efficient producers of hot water for central heating and operate most efficiently at lower output temperatures, ideally around 35 deg C.

If done correctly, it can make sense to integrate a solar thermal system with a ground source heat pump (GSHP); they make particularly good bedfellows, complementing each other’s strengths.

A GSHP benefits from a consistent source of energy – the ground – at a constant temperature all year around, which is used to heat a building in the colder months. The Solar Thermal collector frequently has more heat than it knows what to do with even in the summer and the warmer months of the spring and autumn.

By using a special water tank as the interface this can easily be used to make the system more efficient. When the central heating is required and more heat is available from the Solar Thermal Collectors than is needed for the Domestic Hot Water the excess is diverted to directly heat the home. This happens surprisingly often in the spring and autumn but sometimes even on a bright winters day. It also saves wear and tear on the Heat Pump and improves the systems overall efficiency.

In addition if the domestic hot water needs have been met and no central heating is needed, for example during the summer months, the excess heat from the solar panels can be directed into the ground via the boreholes that support the GSHP. This warms the ground around the boreholes with the ground acting as a sort of giant “thermal store”. In the winter months this stored energy can be used to help supply the heat pump making it run more efficiently than it otherwise would.

Integrating the two technologies in this way doesn’t add significantly to the cost of installation but can bring real benefits in overall efficiency. Also of course there will be real reductions in CO2 emissions as a result.

Related categories:  Energy management   Heat pumps   Residential applications   Solar heating