A PVT heat pump can be an innovative and sustainable source of energy for heat pumps. A PVT panel is an advanced solar panel that produces both photovoltaic (electrical) and thermal (water/glycol) energy.
These panels generate both electrical and thermal energy, both of which are essential for a heat pump's operation. However, it's important to note that there are different types of PVT panels on the market.
Standard PVT panels are designed to dissipate the heat generated by the photovoltaic portion, often with insulation on the underside of the panels.
PVT panels suitable as a source for a heat pump are specifically designed to absorb as much heat as possible, even from below, and do not contain thermal insulation.
In the simplest setup, a heat pump is considered a ground source heat pump, but the source is not ground energy, but energy from the air extracted via the PVT panels.
A mixing valve on the source side prevents the heat pump from reaching an excessively high source temperature. The maximum source temperature varies by heat pump brand but is usually between 20 and 30°C. In summer, the thermal collector supplies water warmer than 30°C, and the mixing valve mixes the cold returning from the evaporator with the heat from the collector to stay just below the maximum permitted temperature.
The advantage over a 'normal' air/water heat pump is that no outdoor unit with a fan is required, meaning there is no outside noise source that could potentially bother you or your neighbors.
This solution works best if you try to heat as much as possible during the day and possibly reduce the temperature by a few degrees at night. You can also heat the domestic hot water boiler during the day, extracting most of the energy during the day. This has two advantages: the outside temperature is warmer during the day than at night, which means better efficiency for the heat pump, and because you extract energy during the day, the panels cool down outside, which also means a better efficiency for the PV panels.
As a general guideline, it's assumed that for every kilowatt of installed capacity, 5 square meters of PVT panels are needed. For a 6 kW heat pump, this means 6 x 5 = 30 square meters of PVT panels. Note that this is an average, and each supplier may use their own figure.
A company recently commissioned an analysis/test of their PVT panels combined with a heat pump. This proved to be a favorable solution throughout the year. The test setup, with measurements by TNO, showed that a well-insulated new-build home with a capacity of 5 kW and 25 square meters of PVT panels (gross annual energy requirement 30 GJ) achieved an SPF (Seasonal Performance Factor) of 5.01, which can be considered very good.
Undoubtedly, more results from other PVT solutions for heat pumps will become available in the future. Purchasing specialized PVT panels is currently still expensive, as they are not mass-produced and the development costs have not yet been recouped. The costs are even close to what a ground-source system would cost, but this is expected to change in the future. An additional advantage is that this system does not fall under the requirements for ground-source systems.
