Let's set aside the obvious, that as a generality, water and electricity don't mix well.
I suppose we all know that there are some pv panels that do very well when floated on water.
And we know that panel output drops by about 0.5% per degree C (about 0.3% per degree F) for every degree above STC (cell temperature 25 degrees C) reached by the panel in its normal operating condition.
... So it "makes sense" that cooling the pv panel by removing excess heat could improve its output.
But realistically, how much heat can be removed, and what is the quality of this heat (i.e., temperature, aka "enthalpy" of the cooling fluid)?
With ambient air at 25C, s typical air-cooled pv panel's NOCT (Normal Cell Operating Temperature) might be in the 50C (122F) ballpark.
Because
conductive heat transfer only flows from "hotter" to "cooler", any flowing coolant will never get even that hot.
(Solar thermal panels, like solar ovens, are designed to capture
radiant heat from the sun, and can reach temperatures far higher than this).
Yes, the fluid used to cool the PV panel can be used as a heat source. But to get water, for example, up to a usable "hot" temperature for domestic use, it likely will be necessary to use a water-to-water heat pump to get the desired temperature.
You could accomplish half of the intended result by collecting your conventional (air-to water) DHW heat pump's intake air from just above the top of the pv panels, using the panels' waste heat that transfers into the surrounding air and rises by convection up to the top of the panels.
This would not improve the pv panel's efficiency, (unless you actively pulled air across the panel and thus cooled the panel somewhat).
I think what we are dealing with here is the difference between what theoretically makes perfect sense, versus what is simple and practical.
In a residential setting, how hard do you want to work to fractionally increase the panel's output? And what is the value of the heat you would capture, which otherwise would be "wasted" by heating the surrounding air?
Now, in a fixed array commercial solar farm, there might be a way to make use of the large amount of relatively low-quality heat coming off all the pv panels, if it could be efficiently collected. But in a home situation (where what might be collected is much smaller), perhaps not so much.
A "tracking" array? The complexity boggles my mind.
Bottom line - PV energy is cheap, and getting cheaper each year. Trying to squeeze a bit more out of each panel, by not "wasting" the discarded heat, once all the costs are tallied, may not be the economical way to go.
Just my 2 cents' worth.
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Hugh Willis
Old Engrs Never Really Retire
GREENSBORO, NC
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Original Message:
Sent: 11-30-2021 11:49 AM
From: Allen Wilkinson
Subject: PV+solar thermal panels ?
Are there PV+solar thermal panels on the market yet?
I saw a concept a couple years ago for an IR transparent PV panel that then has a solar heating panel below it to capture the IR.
Sincerely,
-- Allen Wilkinson