Bit of an addendum to the article below. Since we came out with our PVT panel a decade ago, the cost of PV dropped by 80%. It just doesn’t make financial sense (in Canada for sure) to produce the PVT when PV direct to element in a water tank is far more economical and simple to install. Maintenance is also near zero as well. Using a PV direct to element system also allows the electrical energy to be switched to other loads when the tank is heated. This is the approach we are now using. That said, feel free to read the desctiption below just for education.
PVThermal panels take the excess heat off the back of the traditional PV panel and transfer that heat to a domestic water heater or to space heating.
When any PV panel heats up under bright sun, its efficiency decreases. Panels will often have a surface temperature of 60-80°C under full sun, reducing efficiency up to 30%. The PVT can increase the electrical output by 10-25% over the year when the excess heat is taken out by the solar hot water system behind the PV panels.
Another benefit of the PV-Thermal system is that the same real estate needed for a PV system can now be used for solar hot water as well, allowing for a larger PV system. The PVT system looks the same as a PV system, except for the piping that you would expect from hot water collectors.
The average solar water heater has 5-6m2 (50-64 sq ft) of panel area and provides 70% of its heat in the spring/summer/fall months. Imagine a 2kw PV system with an area of 12m2 (125 sq ft) of hot water collector. In the summer months we have all the hot water capacity we need and in the winter we have more than we would have had with a smaller Domestic Hot Water (DHW) only system. This gives us the ability to pre-heat a lot more water especially for floor heating which needs, in a well insulated house, 30-35°C (85-95°F).
Got an air source or ground source heat pump? We can provide heat for that too and bump up its efficiency.