I think the pex material has poor thermal transfer but if you put metal tubing with a heat transfer paste that would work better. You definitely want the back ope as you discovered because the panel cools off by releasing radiant heat.

My Thoughts: Use the pvc drip system (from the prior video), and let the water run down the front of the solar panel, then let it drip off the bottom of the panel directly into the pool, but put a few feet above the pool so the water can dissipate some of the extra heat while falling through the air.

Have you checked out the DualSun Spring solar panels? They are a commercial solar panel with water cooling

This channel is great by showing what not to do, like using insulating polymer tubing to transfer heat. You are almost there man!

Completely half-baked idea: aluminum sheets with a silicone/caulk "maze" (or zig zag) sandwiched between?

You have almost no heat transfer between the pipe and the panel. It appears that most of the panel's cooling is coming from ambient air, which is why the temperature went up when you added the foam panel. You could probably do better by blowing air over the panel instead of messing with a water system. The water's going to eventually approach ambient temperature anyway, unless you have a larger pool. Some black spray paint on the back of the panel could also help it radiate heat better. If the humidity is low enough, you could try evaporative cooling. Build an enclosure on the back of the panel with an air inlet on one end and an outlet on the other. Add some baffles so the air has to meander around the panel instead of just blowing straight through. Put some wet material (like a swamp cooler pad) on the inlet, and use a fan to blow air through it. You should also consider collaborating with @NightHawkInLight.

Your first test was not a failure! It showed that the panel needs to cool itself from the back. You prevented that by adding the insulation turning the panel into a solar oven. So given that panels do cool themselves from the back, try painting the back of the panels flat black. Even without any water you should see an increase in output because of the black-body radiation from the back.

In addition, with a pump system, you should also consider how much power the pump uses during the experiment.

The first test was so great didn't think you needed another but this is even better, great job

If run correctly (In a zig-zag pattern from bottom to top,) you should be able to use Natural Circulation to induce flow from bottom to top instead of running a pump.

Your tests were not failures you found out what works and what does not. I was thinking instead of using the pool water create a loop by using a cooler full of water and ice and run it through the pex tubing. The water will definitely be a lot colder than the ambient temperature outside.

I love how scientific this channel is - experimenting to see what is the best setup. What if you built a set up like in your first video and collected the water as it ran off the solar panel and moved it back into the pool?

Dude I like your experiments! Was interesting to watch even though it didn't work out quite well. Keep up the good work!

These videos are great! Ultimately, 1/4" copper tubing has several advantages. Make a radiator type pattern by using a 1/4" tubing bender and make those 180 degree bends. Do not use one pass. Instead use several parallel passes. Using the wood to press the plastic tubing is great and doesn't result in any permanent changes to the panel, so use the same approach with the copper tubing with the addition of some thermal coupling compound (like you put on a new CPU when coupling it to the cooler) along as much of the copper tubing. Apply this once the tubing is in place. Although more expensive than your trial methods, still probably less than $50 per panel. Lastly, the fountain pump is a very weak link. Looking at your previous video, where you went thru 130 gallons, Which ever DC pump you choose, it should be closer to that 130 GPH as your fountain pump is probably on 7.5 GPH. I look forward to your next video in the series!

Maybe a heatsink would perform better, by insulating the rear of the panel you are trapping in heat that would normally transfer to the air, also you need to ensure more surface area contact between the pipe and the back of the panel, micro copper tubing and heatsink compound would be required to improve the system you have right there.

By opting for hydro coils instead of a drip system you switched from a really good cooling strategy (evaporative) to a really good heating strategy. Coils will work great for keeping the pool warm, but they will never work for cooling the panels no matter how well you insulate them. With how much UV radiation those panels are getting, insulating the back just turns the panel into a heat battery. The only way the insulated hydro strategy MAYBE works is if the pump pushes water from the pool to an underground reservoir big enough to absorb the 80+ degree water, cools it to around 55 degrees geo-thermal style, and THEN gets pushed to the panel. That temp differential should suck a bunch of heat out and equalize to around 80 degrees by the time water reaches the pool. But, that would be a monstrous investment, so evaporative cooling is the way to go for the panels. I would try to run the next experiment with the drip setup, but then have a water reclamation strategy where the warm water that doesn't evaporate gets deposited into something that routes to the pool. Also, you should semi-shade the kiddie pools. The UV heat they're getting makes it harder for this experiment to be applicable for folks with larger, in-ground pools since they wouldn't heat up as quickly in sunlight. Side note if you go this route, there will have to be a way for larger systems to add city water as the drip water evaporates over time. Probably something like a float switch somewhere along the pool-to-panel line with a hose hookup.

Liking these experiments. Keep up the good work!

Try 2 changes: 1) more loops behind the panels - as much pex as you can fit back there. 2) use heat conductive FOIL TAPE - the entire length of the pex to increase the surface area in contact with the PV panel. In radiant floor systems, pex is laid in aluminum channels to improve heat transfer. Use this principle in YOUR experiment. I've been thinking about this very principle to see if I can create free hot water in winter for my radiant floor system. Do a Trial 3, and let us know how it turns out. If you get good results, try using a pump with a higher flow rate. Good Luck!

You might try Aluminium box section. Much better heat conductor and more contact area. In fact it might improve things without water. Just the greater thermal mass and cross section. It would improve against with a fan blowing air through it Also look at thermal tape to connect it

That was alot of work for this video, you did great, always learning anew. Awesome 👍🏿

Awesome, thanks for running these tests. I don't think you truly appreciate how efficient what you just made is though. A 4 F increase of 60 gallons is 586wh, that's 82% more energy than the non cooled panel when the heat is added in.

Nice job. Really enjoy the measured approach you use for the experiments. Have you thought of just using a small DC fan to blow air from the shade under the panel across the bottom of the panel? Maybe see if placing on the grass vice the concrete driveway? Look forward to your next attempt. Thanks for making and sharing these.

I think a higher flow pump and different material of hose that has less insulating properties would have much better results, I don't know if it would have enough of an effect to overcome the power usage of the pump though

NOTE - I love these experiments!!!

This was really interesting. I watched your other video on dripping water on the surface. I'm guessing that worked better due to evaporative cooling. Seems like the water cooling idea probably isn't worth it. Thanks for the videos!!

Great video! I’m looking at both solar and solar heater for my pool. I’ve been wondering about combining them into 1 system

You identified the first issue: Pex does not have the thermal efficiency of copper. Any metal would be better. The reason the water cooled the panel in the first test is that water was in direct contact with a surface (glass) that was efficient at transferring heat to the water. If you do the first test and have it drain into the pool, you would likely get a better result, even if loosing more water to evaporation. . The overall problem using this system is that you are having to use energy to pump the water through. Can it save enough energy to supply the energy needed to pump? The first test was getting "Free" energy in that the pumping was already paid for, but even there you are still paying for pumping at the utility.

You could make a giant "CPU water block" for the back side of the panel. Feed water in from the top and make it take multiple paths under the panel to transfer directly to the water. I also like the suggestion of going back to your first test and just collecting the water after it has traveled over the panel to pump it back over the panel. The temp of the water coming from the hose is going to be a lot colder than water that has been sitting in the sun.

Can you compare the temperature of two panels, one connected to the load and the other not connected (open circuit)

Coat the back of the panels with small finned heat sinks and blow a fan across the fins.

you could use 1in+ aluminium extrusion the length of the panel found in hardware store. You drill the bottom and top and cap the end. Then you stack them the entire width of the panel with silicone. The water pass through the bottom and go to the top, then to next aluminum channel but down to the other channel that will go up. Make sure you apply a thermal interface material (TIM) inserted between aluminium and panel. that remove all air bubble and surface defect. I know you are saying that is overkill, well yes, it's proper engineering, it require work. if you save 5%+ for the next 20 years, it will pay off!

Thanks for saving me the trouble of going down this path. The easiest / cheapest solution is, of course, to put 5% more panels in the system and accept the inefficiencies. .But that is no fun. Keep inventing

May I suggest you look into thermosiphon systems. Usually they are used simply for water heating but maybe you can get rid of the solar thermal "collector" and replace it with solar PV and somehow channel water directly on the back of the PV. What's great about them is there's no pump required. The downside is the tank/pool of water needs to be above the solar panels! I believe Solahart was one of the original companies that made thermosiphon solar water heaters for home use.

I’m now a new subscriber to your channel! I’ve watched a few of your videos and I like your theory and testing methods. I look forward to seeing more of your content! BTW, I just set up a small 12V 400 watt panel system which has a 400 AH capacity as a grid down emergency system. I’ll see what type of results I get from it over time. I did install a PV combiner box several safety switches for both the panels and batteries and I’m using a 40 A Epever Mppt charge controller. My inverter is a large Vevor pure sine wave at 5KW continuous / 10KW surge but I will probably purchase a smaller converter to use on this system so that I don’t have as much stand by power waste. Thanks again for sharing your findings!

I live in Central Florida. I have a 2500 watt solar panel system. Man it makes sense to actually use pex pipe stuck to the bottom side of the solar PV panels to gain heat with an inline pump to a water heater to get free water heating. I was even looking into Heliatos Solar panels for water heating but this may be a whole lot cheaper for water heating. Great video. I know you're looking to cool off the panels but use that picked up heat from the PV for the water heater! Jeff - Sunny Central Florida

try to spread water system with a 4 x 4 on the end of the bottom solar panels with a gutter to catch the water and return it to the pool however you’d like.

Very interesting follow up video! I wonder if you had a stronger pump to move more water if that would help. That and as you noted a thiner pipe to help dissipate the heat better (not sure what that might be that's cost efficient though). Another thing that I did see mentioned before was you need to take into account the power used to run the pump.

I saw somewhat the same experiment from India. They had submerged the panel in water to keep it cool.

what about a combination of your first test and this one? water can flow over the top but drain into the pool with same pump setup.

Maybe try double wall polycarbonate panels they would make a good contact with back of panel and pump water inside the walls you would need to make some kind of connector to split water in to all channels.

This is just my two cents, but... PEX will never work as it does not make enough thermal contact with the cells to make a difference. Water absorbs heat like a champ so use it better. Seal off the bottom of the panel. Use glass or plastic or metal , it will not matter. Make it water tight. Some people will say to use baffles to direct the water but in this situation it's not needed. Be sure to make the inlet bung orifice larger than the exit bung and since the panels are angled, have the exit bung at the bottom. Drill a hole for a vent valve at the top for a valve to vent the air pocket that may develop. The pump only needs to be powerful enough to just move the water. You need to move enough water to remove 160 watts of heat from your 200 watt panel. You might need a larger pool but you can experiment with that. Realize that using water is the worst for long term usage, oil would be preferable.

It would be interesting to compare a passive heat sink version, or even a heat sink with a small fan. If it’s useful, the fan could be set to turn off on windy days, so it only runs when needed.

You should use pex-al-pex. It is way better at transferring heat and is cheap. But realistically you should seal the panel with mineral oil inside and run the PEX-al-PEX through it. That is the best way to pull from the entire surface area. Another option if you want to save money and time is to use aluminum across the back and sandwich the pex-al-pex between another layer of aluminum on top then insulate. By aluminum I mean even a thin layer like aluminum foil or possibly aluminum tape.

Should be using black piping for better absorption of heat.

I have always wondered why people are not doing this! Now I know! Thank you!

Interesting video. Thanks for the test. You can try a square ABS or PP pipe, there will be a much higher contact and you can try to cover the back of the panel evenly. They will just work as microchannels and remove heat.

I thought about mounting the panels about 6 inches above the shed roof with a pressure treated wood frame that sits on a waterproof vinyl membrane like they install under shower pans to collect water at the low end. Install a grid of drip mist sprayers aimed at the back side of the solar panels and allow the water to flow into a gutter then into a collection pond like the kiddy pool you are using. Use an RV 12 volt water system pump to provide the spray pressure with a cheap whole house filter to keep the nozzles clean. Putting water to the back side of the panels avoids the scale buildup like wetting the collector surface. Last Summer I noted an additional 47 watts output from 800 watt rated panels when I hosed them off at mid day. Normal max output in my installation is about 610 watts but it was nice to watch output jack up to 657 watts when I washed them down. I use a Windex window cleaner hose attached sprayer to clean my panels when they are in the shade. Dishwasher spot free detergent crystals work as well. But alas....want more power, install more panels and don't bother cooling them. They all suck during low angle sunlight and the short days of Winter.

It's super awesome that you published the negative result! We don't do that nearly enough IMO.

Can try using the first experiment water spray set up. Build a catchment trough at bottom to catch the run off water and recirculate. This will safe water. +- a filter to avoid blockage. . Nice work a joy to watch your videos. 👍

So your videos have not only given me a added idea to try something like what you have done but instead of just letting the water run down to the ground or in a pool my thought is to get a ease through and have it at the bottom of the solar panels and then run a hose from there in to a water collection container so it can be spray back on there to keep the panels cooled down and and the same thought could be used during winter with windshield deicer to keep the solar panels clear of the ice and snow plus you could set up both system to integrate in to home assistant to be able to control the system with automations and make it to the point were you can shut the pump off when its not needed to run

Appreciate the effort. Please do use a cheap small diameter copper tube, stick it on large thin metal plate sheet, alu, tin, something, the size or close to, of the backside, please use thermal compound between everything, thin layer, like on a cpu or it will be a failure. Especially between pipe and plate/sheet. Please do not add insulation, we dont want an oven lol Love your vids. Thanks!

Always ask yourself many questions! I liked your first experiment with this with the long shower head you made. If you had a thin aluminum side wall running down each side of the solar panel to keep the water from wasting over the side, then mount the end over the pool, so as to catch it. I feel, that at first it would make a great deal of difference, but as the pool water heats up, it would become less efficient. Maybe a larger pool? I made a solar water heater for my 12’ inflatable pool a few years ago. It worked well, & the pool was enjoyed, while it lasted. I still have the solar water heater, but the pool deflated itself, & is no longer with us! Keep your smiles on!

I have been considering doing something exactly like this for my panels, but I was going to use garden hose. After watching this, I think it might be better to create a reservoir under each panel pumping water into the top, and out the bottom. Think "gluing a tupperware dish to the underside of your panel", and running enough water through it to keep the actual underside coated in flowing water.

Maybe you can close the back of the panel with a watertight plate. Seal the complete panel and let water run in from the bottom and out on the top. Like this you have direct contact between the water and the panel.

I think you pretty well got it at the very end - Pex doesn't xfer heat too well, and low contact area / poor contact to the back of the panel. Another issue I would investigate: what is the back of the panel made of? If it is aluminum, then ok, but if its fiberglass or any other variation of plastic, heat xfer thru that is already compromised there. My suggestions: 1) If the panel backing is aluminum itself (or any metal that has good heat transfer), use a metal tubing on the back instead of anything plastic-based. Yes, I know it'll be pricier... but it doesn't have to be copper - you should find a less expensive small aluminum tubing that is flexible enough. 2) Use a heatsink compound / thermal transfer paste or glue between the tubing and panel. Even with a good metal tubing, the point where it contacts the panel surface is so small, you need to give it as good of a contact quality that you can. (Square tubing would be great! But STILL use thermal compound even so...) 3) Try to distribute the cooling as evenly across the back as you can - if some cells don't get cooled as well, their internal resistance can still inhibit improvements gained by the rest of them. 4) If the panel backing is NOT a good, heat-conductive, aluminum or other metal, then you have a lot more to overcome - you will need to provide much more complete coverage of the back to effectively cool it: 4A) Use a piece of aluminum sheet metal cut to just fit inside the back of the panel, right against the back surface. Use thermal conductive paste over the whole surface so that the whole panel back area can transfer its heat better to YOUR aluminum back that it SHOULD have had, then add the tubing to THAT, as above. The idea here is you need to pull heat from a much more complete surface area to make up for the poor transfer from a non-metallic backing. 4B) Alternatively, you could basically turn the back of the panel into a thin water tank by making sure all corners and edges are well sealed and adding a backing to it, sealed all around the edges of the panel, and put intake and outlet ports on it for water to flow in & out. This way, the water itself is in full contact with the back of the panel, with no gaps, giving good transfer and good coverage. The problem with this, is that the panel probably isn't constructed for this type of use, and could be a risk of water infiltration to the cells and wiring, so is not a good idea for an actual installation, but should be ok for experimentation if the panel isn't high voltage, and you are carful! 5) You COULD extend the original idea and run water down the front of the panel, but do a similar water "tank" idea to 4B, but on the front, using clear glass to contain it. The problem here, though, is the added cover glass may lose more light on it's way to the panel than you gain by cooling it. Just my ideas for it, FWIW...

I'm impressed with your creativity in these tests. I grew up in IL but think solar in that state is a bit of a stretch. I think you'd really have to over panel and much more battery capacity. Come to the Southwest, we got more solar than you would know what to do with. Water not so much. Cheap property taxes too.

You nailed the problem. Plasic is great if you want to absorb radiated heat and it's coloured black (hence the swimming pool solar heaters that are made of thin tubes (a lot of surface area) polypropylene. While they're great at absorbing radiated heat, they're pretty bad at conducting heat which is what you want for your application. One thing you could try is sealing the edge of the inside of a panel with silicone between the aluminium rail and the backing and then adding watertight fittings to your inlet and outlet and then sealing the back of your panel with a waterproof seal like perspex sealed with silicone. That way the water is directly in contact with the back of the panel. The inlet would have to be at the top and outlet at the bottom otherwise I think you'd risk getting a thermocline and some water not cycling through. You couldn't really use that system for a proper swimming pool because salt and/or chlorine are pretty corrosive but it would be an interesting test. Tech Ingredients ran interesting test with an aluminium heat sink and fans. I'm not sure how the Dualsun panels are constructed but it's a solved problem.

I have something like this already. Simple sch 20 pvc. I have 1in input at the top and 1in exit at the bottom on both. All the back of the panel I have 1 vertical run of 1/2 pvc behind each vertical row of cells. O fill the lines with water to weigh them down and poured a 1/2 layer of mold making rubber mixed 2:1 with graphite. Another option is the flexible grout using radiant floor heating and maybe just using a lot of 1/4 aluminum tubing between the top and bottom bulkhead

I watched your first trial and thought it was an interesting concept. On the weekend I was adding another solar panel to the setup on my roof of my van and decided to hose down panels once Id finished. I saw a much more substantial rise then your first test - a 25% rise in Watts! Simply from hosing down the panels. This effect subsided over about half an hour in 32c temps. I'm sure a AIO cooled solution much like you can get for CPU's and GPU's would produce some pretty excellent results.

you might want to shade the pools and use some type of heat transfer past to attach the pex. However, I would check to make sure that the heat transfer paste is easily removed. Very interesting experimentation videos Thanks

I watched the videos last evening. First question: which side (Front/back) is warmer? (I suspect the front). That said the largest delta-T will always (all other things being equal) have the largest heat transfer. Surface area matters (contact-wise). Use AIR. Close the back to create a chamber that is as deep as the frame. Seal the sides. The resulting box/chamber will get HOT. but we wont let that happen. at the TOP rail, create a penetration. the larger the better. That penetration should be used to hold a standard fitting (perhaps a 3/4" or 1" PVC nipple.) Repeat the process at the BOTTOM of the panel. Heat rises. Natural processes WILL cause air to be sucked in the bottom nipple, and exhaust from the top. but thats not good enough. use a flexible hose (garden is fine) to connect to the inlet and outlet at the panel to the wading ponds. at that point transition to copper pipe. the longer the better. a manifold (radiator) would be best. submerge the pipe/manifold/radiator in the pool. the heat will go from the heated air, across the copper pipe wall to the water, cooling the pipe and the air flowing thru it. This is just natural convection/circulation. It works ( at least on Nuclear Reactors. -- i know from first hand experience). It would be a major improvement to have a small plenum inline with the hose that contains a small fan to help move the air faster. This would dramatically improve performance. Small Fans like www.amazon.com/dp/B075V3BYR7 have Airflow: 9.5CFM each. and run on 12VDC drawing 2.8W MAX each. One fan should be enough to force at least one complete 'air change' in the created underpanel "box" per minute, maybe more, forcing a perverbial ton of cool air across the entire surface area of the panel. Benefit: Less overall piping, Much simpler design, no concern of pipes behind the solar panel leaking water onto any electrical components (its all dry air) and most important is the the surface area interface is massively larger than even the spray bar on thesurface, since in that case only the actual drop/glass contact area counts.

I have 2 solutions for you, one simple and one harder and more complex. The first solution is just to drop your solar panel into the pool. The panel will always be cool because the water will always dissipate all the heat. The second solution is to make the solar panel waterproof and fill the back with water. Seal the back with sheet metal, to contain the weight of the water and use angle aluminum to support the metal back. Add hose connectors to the top and bottom to circulate the water to the pool. So instead of tubing (any kind) you fill the solar panel with water and if you use aluminum sheet with angle stock - you might not need the pool.

Hi. I have investigated using 1/2 inch black irrigation tubing in a spiral coil for a DIY pool solar water heater. If there is any air in the system, the differential pressure between inlet water pressure and outlet water pressure is AMPLIFIED greatly if the coils are not absolutely level. Thus, any tilt to collector will substantially increase differential pressure, affecting pump flow efficiency, and therefore performance. Hence, solar pool water heaters are designed to be header-riser configuration and not spiral coil loops, cuz of tilt. Geothermal systems buried in ground do okay with loops because they are laid basically flat and they have a lot more contact surface with the earth. Chuck in Florida.

Thanks for the testing...IMHO, nowadays it is much easier and cheaper to just buy a extra solar panel then to try and rig up some system to cool solar panels to try and get more wattage out of them. I just purchased brand new 400 watt solar panels for $200 each. At 50 cents per watt, its a no brainer to over panel if one wants to make sure they have additional watts/ power on hand.

Air cooling is easier to make and often more reliable if you get outdoor rated fans. However, if you are bent on liquid cooling like to heat a pool and not using panels with built-in liquid cooling, there are a few options: drip water down the front of the panel like test 1, but collect the run off and recirculate it, maybe drain into the pool and pump to the top of the panel, a more practical but labor intensive option is to put something on the back of the panel that can hold water and some baffles so the water can directly touch the panel if the electrical connections are waterproofed... this would provide good thermal contact and the wide flow path and would be less resistive, and also the sealed nature might reduce the needed head pressure since the whole system is one sealed unit and the water going up is offset by water falling down.

PEX Tubing has no Ultraviolet resistance. It will degrade FAST in sunlight. You'd really be better off with a garden hose. This means you're still better off with soft Copper tubing for a solar heat collector.

I was considering fitting solar to garage roof. At present, garage guttering feeds into a couple of large water butts. In view of the success you had in spraying water giving 5% more power, I was considering rigging up something similar but using free collected rain water when the levels in buts were above 50% which they generally are in the UK.

Perhaps devising a method using fans to constantly move air across the back of the panels would be more cost efficient and/or as efficient as copper coils or aluminum heat sinks. Solar panels tend to stay cooler when laying just a foot off the grass vs those mounted several feet above in a rack. That's counter to the above mentioned air movement suggestion. There must be a cooling effect due to the moisture evaporating from the grass. Maybe that cooling effect could be duplicated. Just some thoughts. Great videos!

you could seal the back of the panels and put hole inlets top and bottom and run distilled water through the panels and then through the pex in the pools ,the distilled water will give 100% contact with the panels with higher performance.

I said this on your other video, but will post it here as well. You should consider doing a project like the one you used the hose to spray down the front of the panels, but using a reservoir, rather than running the hose. The reservoir should heat up as the water goes over the panels, where it would collect at the bottom and get pumped back to the panel again. This way, the water would get heated, and evaporation would decrease the temperature. You could attach a hose using a float valve to keep the reservoir at a level you prefer. This way, you only lose water to evaporation.

I was thinking some sort of rudimentary plastic welding with thin sheets (like you see with vacuum seal bags). Not sure what sort of path / maze would be best for the fluid, though. A single path might restrict the flow too much, but multiple paths is a hard design challenge.

Interesting experiment! Ome thing you may try in a next experiment is using something like aluminium tape to stick the tubing to the back plate. That way you increase the contact area of the tubing to the back plate and perhaps the aluminium tape transfers some extra heat too.

Use the same system as a PC water coolant system. It uses a coolant. And a fan radiator to remove heat from the coolant.

Several comments mentioned aluminum plates used for radiant floor heating. I thought they'd be expensive but but they aren't, maybe $2 for a 4 foot long by 4 inch wide section and are designed specifically to transfer heat from pex to a flat surface.

Seems like the best solution would be to use the original test with the water running over the top of the panel and catching the water in a trough at the bottom that could then be recycled for more runs. You can use the streams of water on the top and perhaps misters on the bottom and reduce the waste a little bit while getting the ultimate amount of cooling.

Chem Eng here. Use flat tube instead of round tube. The round tube has a very low area of contact per length of tune. Metal tubing would also help. Equation of heat transfer is heat = area * U * temperature difference. Area can be increase by using flat tube or more coils. U is the heat transfer coefficient, which is mostly determined by the conductivity of the back of the panel, and the tubing, and minimally by the flow rate of the water.

4:15 "Something is wrong BATMAN!"

Cool experiment. If you had a giant array of panels, close to the ground it might (?), makes sense. Having a pump that can move enough water, quickly enough is really going to eat into any gains. Alternatively, you could use copper, or otherwise make more cooling available at the back of the panel... But, that is going to get REAL expensive.

We should figure out a way to laminate a sheet of poly film to the back of the panel and just use the back of the panel itself and create a pocket of water that is directly against the back of the panel. Then open a valve at the bottom edge of the pocket and let gravity drain the water out. Maybe even create a suction effect to draw more cold water. Another idea would be a passive loop that could contain a refrigerant since that will be very efficient at transferring the heat.

Add a sheet of polycarbonate or plexiglass or similar material glued/attached to the frame, then pump cold water at the bottom of the panel and collect it from the top. 100% contact, decent heat transfer, simple and quick to build. Of course check the specs of the panel to make sure it's waterproof on the back too (they should, since if not good luck with storms and hurricanes...). You probably also want to try changing the flow rate of the pump to see what kind of difference it makes.

As others have noted, need a more efficient transfer, but copper is too expensive. I would suggest keep using the pvc, but use heat transfer plates, made from aluminum used in installing radiant floor heating. I used these transfer plates installing radiant heat for my living room, and they do work. Second, instead of using the pink rigid foam for insulation, I think using the reflective bubble wrap insulation will do two things: keep the cold energy against the solar panels, and reduce any heat transfer from the concrete up into the solar panel. Some have suggested a stronger pump, but I think you want a slower pump to give the energy transfer more time. This too is similiar to radiant heating for homes, as of course you need a pump to circulate the water, but you also don't want to oversize the pump either. Another great video, keep them coming!

Put a small tray of water on the floor under the panel. Just the cooling effect of evaporation will have a big effect. Bonus that it is easy to setup and passive. No need for a pump (which whenever included should have its consumption measured to know if it adds or subtracts from the energy gained).

Whether the material of choice is copper, PEX, aluminum, etc, I wonder how a system might perform if the back of the panel was covered in as many vertical tubes as possible, with manifolds at the top and bottom of the panel. Rather than a constant flow, a solenoid would control a valve at the outlet of the bottom manifold. The valve could be set to open at prescribed times or based off the temperature of the contained fluid. A system of this type would allow the water to absorb the heat over more time and also reduce the need for high flow rates, as the system of pipes can refill as slowly as your water supply will allow (say if you are running a small solar pump from a pool, rainwater barrel, well, etc). It might also use less power compared to constantly pumping.

Coiling the tubing is a major problem. Heat wants to rise and it's being forced to go back down again to complete each circle of the tubing's coil. So design doesn't allow for heat to effectively be drawn up and away. If you bring in the tubing at the bottom, zigzag it repeatedly side-to-side till it reaches the top, then exit back to pool, the heat will follow the continual upward path drawing more heat from the panel in the process. Using copper tubing which conducts heat better for the part that goes against the back of the panel, must be in contact with the back of the panel as much as possible, will also improve effectiveness. Have you thought of placing a thin back panel of some kind on the back of the solar panel, spaced from making contact with the panel's backside by the panel's frame. With openings across the bottom and top... to create a natural updraft effect as panel heats up. Drawing cooling air in through the bottom openings, passing it like a cooling breeze across the back of the panel on it's way up and out the top. Funneling the top openings down to a 2 or 3 inch diameter pipe that's painted black and extends 2 foot above the panel, could increase the airflow through the cooling chamber even more. No pumps, fans, or moving parts of any kind that would require a power source to work.

I thing getting a stronger water pump would make a big difference. Your pump was barely moving any water. Also obviously changing to copper would help but i would suggest the 1st thing you try is a better pump

use cooper under the panel and pex from panel to pool. use pex under the panel with heat transfer plates like we use in hydronic floor heating or use pex under the panel and fill the underside void with a lightweight gypsum concrete which is also a standard detail used for hydronic floor heating i would still insulate the underside

Most of the systems that I have seen mist the surface with demineralized water (usually filtered rain water) and let evaporation provide the cooling. Add a low powered fan to blow hot air from the underside and that should help some. ...actually, I wonder if moving air from the top would work better in that case. ...actually you could try comparing between misting the surface vs the underside, with a fan blowing the top or the bottom or both... I mean if you want to run some tests, why not? EDIT: I'm a little surprised by how little the water cooling helped here. I wonder if it's because of the small amount of contact the tube is making. Alternatively, can the panels make contact with water? I wonder how they would do sitting directly on the surface of the water...

I would say a cheap answer for the most transfer, if available, is an old coil from a fridge, car radiator or something like that and run the water through that on the back of the panel. I would suggest a pump that has a better rate of flow. And the other answer is if you mixed your last set up with this one for running the pool water back into the pvc setup so you are not using 100 gallons of water. Not sure how effective over time that would be, but I think it would be better overall than this setup for cooling the panel. But from what I read, there are a lot of good suggestions in the comments.

As in PC cooling, you need to define an efficient water flow ratio, and wait until temperature equilibrium is reached in which the temp of the pool is saturated and then run the test comparing both solar panels.

Another Great video. I get about a 10% gain whether I spray the front or the the back. I also have eight 100 panels wired in series. I wonder if being in series has a cumulative affect. Also mine are on grass and you might be getting some radiated heat off the concrete. You might try wiring the two panels in series and testing it that way

I think the approach is absolutely right. The issue with the test is that the quality of cooling was non existing, there was no contact between the cool water hose and the source of the heat on the panel.

Putting my time with heat-exchangers while working for an industrial pump company hat on: I'm thinking the system needs to be entirely closed, with a coiled loop of tubing going into the pool as well (using no pool water, only what's in the tube) and the diameter of the tubing associated with the pool needs to be smaller, more concentrated than the tubing associated with the panel. So, do that massive coil of smaller diameter tubing, laying in the pool, feeding into the intake of the pump, then from the discharge of the pump to just after the panels have double the diameter of tubing doing a very organized, deliberate serpentine down the back of the panel. Again, that's just going by memory and it has been a few years. I'm also trying to keep in cheap, we'd actually use something like a aluminum pan under the panel for the most surface area, least pressure, but that ain't cheap.

Set 2 (or as. Many that will fit) BIFACIAL panels on aluminum ground mount in the kiddie pool. Rain water collector (50 Gal drum?) as reservoir. Small pump to push thru misters placed at top. Then trial and error on what size pump to pull from kiddie pool back into rain water catchment tank. Have ground mounted panels just above pool height in case the pump fails draining pool. Bifacial should benefit from reflection off pool. Also if rain water catchment was high enough, gravity feed through misters then one pump (do they make adjustaboe flow rate pumps?) to pump back up to reservoir.

Just use tape to seal a sheet of plastic to the back and pump the cold water in at the bottom and hot water out at the top. You could add some aluminium profile to the back of the panel to increase surface area as a test as well. All this assuming you can water tight the frame (tape again since it's only a short term test) and that the diode box is properly sealed.

Seal the back with a sheet material. Blow air across the whole width of the back of the panel and then run this air past a water heat exchanger in to your pool. You may wish to put a number of smallish "disruptors" on to the backing panel to stop the air flow being laminar. Laminar flow would mean that the air would not mix and you would end up with a hot layer of air close to your panels back surface.

My solution if I was serious about doing this would be to sandwich 2 aluminum sheets together, using 1/8" AL rods around the edge and some zig-zagging through the middle and solder it all together. Then use some silicone adhesive for at least a little heat transfer where it doesn't touch. Still want to fixture it in place so the weight doesn't try peeling the cells from the glass. I know this isn't as DIY as buying some tubing, but not that difficult either.

I wonder if you would get better heat transfer into the pex using heat transfer plates like what are used for radiant heat flooring?

I think the absolute best way to get the heat to transfer from the panel to the water would be to literally put the water in contact with the panel surfaces. Can you think of a way to get the water in direct contact with the back of the panel? The most inexpensive way I can think of would be to float the panel on the surface of the water, or even slightly submerged to gain a better angle to the sun. Another way could be sealing the back of the frame to create a water jacket and installing bulk heads at opposite corners(top left and bottom right for example) and use a pump system like in this video, although I believe you need a higher flow pump. One more possible way is to have the solar panel directly above the pool, just above the water, and have a simple sprinkler system that sprays the underside of the panel then just drips back in to the pool.

The best way to execute this test is to have three plates of aluminum sandwiched together with a chanell pattern cut out of the center plate of the sandwich. Your water inlets will need to be drilled into the center cavity and calked to be watertight (welded on pipe would be better). Glue or weld your sandwich together to be watertight. Glue the aluminum plate sandwich to the back of the panels with a full coat of adhesive and run that in your test. That’s the cheapest radiator/heat exchanger I can think of. Also, duct and gorilla tape sucks in heat, you wanted to use gaffers tape. It’s designed to hold film to scalding hot stage lights and works way better than duct tape or gorilla tape can.

I think if i were to do this, I would use black piping and fit the piping so there is no gap inbetween the piping.. i.e. form the piping all in a spiral completely in contact with the adjacent. Wouldnt bother with the cover. All the heat should theoritically transfer onto piping. The problem is the back rubberised backing is an insulation.