Photovoltaic Thermal:: EcoBuild Expo Update
At the Ecobuild expo, there were a LOT of companies who had photovoltaic elec or water heating systems. Few were combined PVT (both electricity and heating water). So I started asking why. Speaking to those that make the panesl and installers / advisors the consistent reply was that the reduction in output of both systems was more than 50% down on what you’d get if each was stand alone. One company that produced PV and PT panels said that:
- A PV panel could produce around 280 Watts of elec, a PVT panel about 120 Watts
- A PT panel over 200 (I think degrees) water, but only 40 degrees from PVT.
Yes, it’s still good to cool down PV panels, with ventilation, or even surrounding green roofing. But it seems that cooling them, by linking in pipes to generate hot water doesn’t work. It seems that the temp hot water panels work at is so high to be efficient, that takes out too much electricity production. Or you compromise the amount of hot water production by having the panels at a much lower temp. ie to be efficient they both operate at vastly different temperatures.
So that means looking at seperate systems for electricity production (PV), hot water productin (PT) and something for when the sun isn’t shining for hot water (for taps and heating).
- The debate re PVT versus PV or PT is extensivly thrashed out at http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=7740&page=1 (the debate rapidly moves on from Thermodynamic Panels.)