Interesting product I came across

[copec]

Solar heat pump solution for water, pool heating

U.S. solar thermal specialist Fafco is set to launch a new photovoltaic-thermal heat pump solution for water and pool heating. The system consists of photovoltaic-thermal panels, a 5 kWh thermal battery with a heat pump, and an electric hot water heater.

www.pv-magazine.com

Like many of you, I've been interested in solar, heat pumps, geothermal, etc. for a long time.

I've been planning to build something like the product linked for years, where I put some pex/aluminum heat spreaders on the back of all my panels, and a pump circulates that to one tank (probably IBC totes with some basic insulation), and then home built liquid/liquid heat pump to a thermal storage tank for heating and domestic hot water. According to my calculations I can opportunistically gather and store plenty of low grade heat without dedicated insulated glazed collectors, enough so as to have a better CoW than geothermal without digging up my suburban yard for some geothermal.

Check out this forum if you are unfamiliar with it: https://ecorenovator.org/forum/forumdisplay.php?f=10

 

[A.Justice]

I work on swimming pools professionally, and I used to work at an incredibly affluent area where people had all kinds of extra money for weird projects. We actually saw quite a few professionally built "diy" solar pool heaters that were mounted in the yards or on the roof. Some of them used black tubing, but a lot of them actually used corrugated plastic.

There would be two pieces of PVC pipe, painted black, with a slit cut all the way down them, that were attached to the two open ends of the black corrugated plastic sheet. Water would be pumped into the top piece of PVC, at a relatively low pressure, and would then run down the black corrugated plastic that was mounted in the sun, into the bottom piece of PVC, then back into the pool. We saw water temps sometimes of over 130° coming out of them, and they definitely weren't the most efficient things. I think if the materials were made of something other than plastic you could definitely increase the temps MUCH higher, but it works as a proof of concept.

I wonder if you could secure a piece of corrugated plastic or aluminum to the back of the entire solar panel, and use that to extract the heat. I think it would be relatively efficient.

 

[copec]

I wonder if you could secure a piece of corrugated plastic or aluminum to the back of the entire solar panel, and use that to extract the heat. I think it would be relatively efficient.

I like the idea of the corrugated plastic or aluminum pressed flat against the back. I need to experiment for a while with the end manifolds and mounting. I have a few extra panels I didn’t rack on the roof just for experiments.

 

[WYtreasure]

According to my calculations I can opportunistically gather and store plenty of low grade heat without dedicated insulated glazed collectors, enough so as to have a better CoW than geothermal without digging up my suburban yard for some geothermal.

Those are a couple cool links copec. Thanks

According to my other half I can't dig up the yard. I will be playing with my old copper pipe solar panels after my solar electric is completed.

 

[circus]

I bought some underfloor radiators to modify them to snap onto tubing, paint them black and install in a glazed box. Manifolds on both ends. There's no reason they couldn't be glued, or something, to the back of a PV panel. Normally they're simply stapled to the underside of a wood floor. If the hot water storage tank is higher than the panel a pump isn't even needed, convection circulates the heated water between the panels and the tank. Then just tap the hot water tank with a circulation pump. Be aware, for what your thinking of doing, it would takes a hell of lot of them to make it worth while. Conflicting goals, wanting heat for the pool or cool for the electricity.

 

[copec]

It seems reasonable to me, even heating a pool to 90F is significantly cooler than my panels. They seem to sit at 60-70 degrees above ambient during the day. Right now it is 40F outside where I'm at, and my hand held temperature gun reports them at 100F. My poly-crystalline panels seem to make about 20% less peak output when hot. Spraying one string of 12 panels down last summer with the hose made the output jump from ~3.7kW to ~4.2kW and my temp gun never showed them dropping below 100F (down from 170F).

My water heater is at the back of my third car single garage, and I took over the wall for PV inverters/batteries, so taking over the back wall for thermal storage tanks, I want to at least have two, one a drainback style with a small 10-20W circulation pump (probably an IBC tote wrapped with some cheap insulation), and then a home built or alibaba imported water to water heat pump to a high temperature thermal storage tank. I could have a pre-pre-heat coil-loop through the first tank, and then a pre-heat through the second, and finally through the gas (now backup) water heater.

During the cold season I would also have a coil-loop that I would use for heating.

From reading some research, black-body panels radiating to the sky can bring a coolent temperature to less than ambient during the night, so during the summer maybe just leaving the circulation pump running all the time can dump the excess heat that would build up. The panels aren't black body, but I would hope I could radiate off some of the heat.

That is large aspect planning, but I wonder if anyone has some practical advice, like how to attach the aluminum underfloor heat spreads to the back of the panel? silicone with some weights? Then put some wood/bars in caught in the PV panel frame to press down on it too?

 

[WYtreasure]

I bought some underfloor radiators to modify them to snap onto tubing, paint them black and install in a glazed box. Manifolds on both ends. There's no reason they couldn't be glued, or something, to the back of a PV panel. Normally they're simply stapled to the underside of a wood floor. If the hot water storage tank is higher than the panel a pump isn't even needed, convection circulates the heated water between the panels and the tank. Then just tap the hot water tank with a circulation pump. Be aware, for what your thinking of doing, it would takes a hell of lot of them to make it worth while. Conflicting goals, wanting heat for the pool or cool for the electricity.

The underfloor radiators look similar to those in my, guessing here 1980's or 90's panels, mine are copper though. I have 4 panels that weigh about 100 pounds each. The panels measure 75 x 49 x 3 1/2 inches. They have 11 copper tubes 1/2" x 69" and 2 copper tubes 1" x 45" at each end. The 1" tubes exit the housing in 3 places as indicated in the pic.
Maybe someday I will find a data plate on a panel and share the info.

My intent is to capture rainwater off the roof and store heated barrels of water in the greenhouse. The plants would really appreciate the stored heat in the Winter. I may also use the system to cool the water at night during the heat of Summer.

It seems reasonable to me, even heating a pool to 90F is significantly cooler than my panels. They seem to sit at 60-70 degrees above ambient during the day. Right now it is 40F outside where I'm at, and my hand held temperature gun reports them at 100F. My poly-crystalline panels seem to make about 20% less peak output when hot. Spraying one string of 12 panels down last summer with the hose made the output jump from ~3.7kW to ~4.2kW and my temp gun never showed them dropping below 100F (down from 170F).

So rob heat from the panels and give it to the pool. Win/Win More power, warmer pool; there's an idea I have not heard of.
You get a point for that one copec.

My water heater is at the back of my third car single garage, and I took over the wall for PV inverters/batteries, so taking over the back wall for thermal storage tanks, I want to at least have two, one a drainback style with a small 10-20W circulation pump (probably an IBC tote wrapped with some cheap insulation), and then a home built or alibaba imported water to water heat pump to a high temperature thermal storage tank. I could have a pre-pre-heat coil-loop through the first tank, and then a pre-heat through the second, and finally through the gas (now backup) water heater.

During the cold season I would also have a coil-loop that I would use for heating.

Yep.

From reading some research, black-body panels radiating to the sky can bring a coolent temperature to less than ambient during the night, so during the summer maybe just leaving the circulation pump running all the time can dump the excess heat that would build up. The panels aren't black body, but I would hope I could radiate off some of the heat.

Yep.

That is large aspect planning, but I wonder if anyone has some practical advice, like how to attach the aluminum underfloor heat spreads to the back of the panel? silicone with some weights? Then put some wood/bars in caught in the PV panel frame to press down on it too?

Hmm, I dunno.
But for those of us concerned with snow and ice on our panels... it seems as though you have shared an awesome idea. Run the coolant to clear snow and ice.
Ya get another point copec.

 

[copec]

Link dump while googling:

Aluminum Solar Absorbers

by U.P. Solar Solutions, a division of U.P. Truck Center

www.aluminum-solar-absorbers.com

PVT heat pump with propane as refrigerant

PVT heat pump with propane as refrigerant with PVT solar panels as energy source as hybrid (existing build) or all-electric (new build)

triplesolar.eu

Solar Hybrid PV-Thermal Panel

Solar Hybrid, Solar PVT, Solar PV-Thermal, Solar Panel, Solar Energy, Photovoltaic Thermal Hybrid Solar Collector

www.solarmastertech.com

 

[WYtreasure]

I forgot to post the picture of panels which are similar to mine. So here are the numbers again and the pic finally.

The underfloor radiators in post #5 look similar to those in my panels, mine are copper though. I have 4 panels that weigh about 100 pounds each. The panels measure 75 x 49 x 3 1/2 inches. They have 11 copper tubes 1/2" x 69" and 2 copper tubes, 1" x 45" one at each end.
The 1" tubes exit the housing in 3 places as indicated in the pic.

Maybe someday I will find a data plate on a panel and share the info.

 

[WYtreasure]

I've been planning to build something like the product linked for years, where I put some pex/aluminum heat spreaders on the back of all my panels, ...

As usual, it takes a while for my typing to catch up with my brain; or vice/versa.

I have seen Solar Panels, the PV type, which will produce power when sunlight hits the back of the panel. So I am thinking some of the harmful to PEX light may getting through the panels.

My point, don't use standard PEX or a pex-like product where sunlight can reach. PEX + Sunlight =

 

[copec]

As usual, it takes a while for my typing to catch up with my brain; or vice/versa.

I have seen Solar Panels, the PV type, which will produce power when sunlight hits the back of the panel. So I am thinking some of the harmful to PEX light may getting through the panels.

My point, don't use standard PEX or a pex-like product where sunlight can reach. PEX + Sunlight =

Oh, I didn't even think about that - all my PV panels pass quite a bit a light!

I think I'm going to first test with some pex and heat spreaders attached with silicone. I'm going to spray the side that attaches flat black to make sure the "light stops here". I'm setting up a cheap solar shed with my spare panels to do experiments with. I'll update this thread as I go along.

 

[WYtreasure]

Oh, I didn't even think about that. All my PV panels pass quite a bit a light!

Perhaps PEX in UV resistant LOOM? Loom would be impractical and difficult to fit in the underfloor radiator though. Maybe there is an underfloor radiator with a tube built in. I have a few hundred feet of copper and a thousand feet of PEX to work with. I think it's funny to take copper out of the house and put it on the roof.

 

[copec]

It seems the guys that make the solar collectors using pex and heat spreaders don't seem to have a problem after it is painted black. I'm going to ask around about that.

It's funny, I started this whole solar project years ago with a pallet of really cheap used panels, and now their cost is so insignificant to everything else I've now done, that if there were someone here that stocks and sells the various Chinese PVT panels on Alibaba, I would totally just replace a string of panels on my roof and save the PV panels for my eventual off-grid cabin somewhere.

 

[WYtreasure]

It seems the guys that make the solar collectors using pex and heat spreaders don't seem to have a problem after it is painted black. I'm going to ask around about that.

A cheaper and possibly better product could be irrigation tubing. That was my first solar pool heater 25 years ago. ?

 

[copec]

The Fafco coolpv product seems to be some nice plastics to press their black polypropylene pool heater material against the back of the panel. There are some pics where you can kinda see that going on here http://artisticpoolscorp.com/cool-pv-solar-energy/



I already tried contacting them though, they don't sell to end consumers, they want you to go through one of the resellers. The couple I contacted are only interesting in doing the full project for you.