Ross Goldstein: Waste heat recovery from solar PV

A little-known fact about solar electric panels is that the hotter the panel itself, the less efficient it becomes. Studies have found a 0.05% efficiency loss for every degree of temperature that is increased. The reverse is true in that efficiency increases by 0.05% for every degree temperature decreases.

Although the numbers above are an average, efficiency change depends on the panel design and hardware used. The temperature coefficient is how solar panel manufacturers measure how well a panel handles heat or cold. It’s a range for the temperatures at which a panel can produce at its best.

People assume that the ideal day for solar is sunny and hot. The inverse is true: Cold, sunny and windy. Under these conditions, the panel gets plenty of energy from the sun, keeps cool and the wind sweeps away the excess energy of heat generated within the solar panel itself. If it is too cold out, the panels are affected as well.

Cooler temperatures are actually better for solar panel production, the warmer regions make up for their heat with extra sunshine. Cooler regions tend to be at slightly less advantageous angles from the sun and the equator but make up for it in excellent efficiency when the sun is shining. All in all, whether you live in a warmer or cooler region, you can get great solar efficiency.

Cooler temperatures are actually better for solar panel production, the warmer regions make up for their heat with extra sunshine. Cooler regions tend to be at slightly less advantageous angles from the sun and the equator but make up for it in great efficiency when the sun is shining.

In Saudi Arabia, at the King Abdullah University of Science and Technology, researchers have developed a unique way to collect solar collectors with waste heat recovery.

I have installed copper piping on the back of PV cells — this acts like a heat exchanger — where a portion of the excess heat is transferred to the copper, which has running cold water that soon is able to become water used to preheat water for water heaters or boilers.

Another option is to use hybrid solar panels, or PVT solar panels, which are a combination of solar photovoltaic panels and solar thermal panels in one module. A hybrid solar PVT module can therefore produce both electricity and heat simultaneously.

Although as a plumbing or hydronics contractor, you may not think solar electric would be something you would be working with, the fact is innovations are happening at a fairly rapid pace and a blurring of the lines between different trades is taking place.

If up have any questions, would like to share information or wish to correct anything I wrote, please contact me at rgch9@outlook.com.