I prevent my panels from getting too hot by keeping them in the shade.

the company DualSun has a panel that can take in pool water to heat the pool while cooling the panels. If no pool, they can also be used to preheat water for your water heaters or go to any heat exchanger. It's a pretty cool system.

Saves $4, almost $5 on electric bill. Water bill goes up $6. Celebrates with a $7 beer.

I am so glad it is only 5% and we all not have to waste water to cool every single panel. Thanx for your work.

Being in a desert area I can't do the water idea but I did put a fan under one of my panels and got a better watt hour return than without the fan. Just moving air on the underside helped a lot!

The problem is less the water, since you can simply capture it with a rainwater harvesting system and re-use it. The question is if you gain more power than you need to have a pump running all day. Maybe it helps if you just turn the pump on for about 20 seconds every minute, but that might drastically reduce the lifespan of the pump and might leave your panels covered in mineral residue left by the evaporating water.

I went in 2015-2017 to a energy convention and there was a company who had solar panels with hoses at the backside. It had a couple of functions. It was to cool the solar panel and to heat the water for your pool, shower. Somehow I never saw it again as the idea sounded good.

Thanks for making this excellent comparison. One cooling option is to use thermal conductive glue to attach aluminum heat sinks to the back of the panel. You could even hook up a separate solar powered fan to draw air over the heat sinks.

Thanks for doing the test. I think the 5% extra energy production seems low and probably will scale up to more if done over a home sized array of 2000+ watts. I've hosed down a solar arrays in the middle of the day and noticed upwards 10% power increase on just the watt output. But, in addition to using up a lot of water, a big problem with is *hard water* stains on the panel's glass from using normal city tap water. Those minerals will get _baked in_ even harder with the intense daily UV and heating. Personal experience. As someone else mentioned, this can only be practical with a heat sink system on the back of the panel: (a) no hard water stains (b) low to zero water waste as water is circulated Requires a lot more materials like hosing, valve, heatsink, anti-bacterial additives, etc. If its going to give 10% energy gain then might as well spend 10% more on panels and spend less money and time. The ever falling prices of solar panels makes that the best alternative to get more energy output. However... I do like this idea of having a substantial behind-the-panel cooling system that would also save the heated water to a solar tank. That way, the house is getting much more energy efficiency from solar panels well beyond the ~21% efficiency of the latest generation solar panels. Look up "2-in1 DualSun SPRING hybrid panel" that has all the heatsink and hosing built into each panel. The manufacturer claims it can give that 5% to 15% panel energy output efficiency improvement as well as heat the water to 70°C. This is a double benefit that's kind of a no-brainer if it can be made and installed economically. But it really shows what our sun is capable of when the correct set of technology is applied!

I would reclaim the water at the bottom, run it down into a geothermal system, in the ground, then when the water cools, it's pumped back up to start the cycle again. Many other uses for that hot water, hot water storage tank for baths, etc.

I have an Ecoflow Delta 2 and 2-HQST 190 watt panels. I purchased them in August of 2023. The panels are connected side-by-side and are rigged with 10in wheels and a sturdy PVC adjustable leg arrangement that can accommodate tilt-angle and azimuth all year long. I can move it around the yard as needed to dodge the shade of nearby trees to grab as much sun as is available. Later in the year, I was charging on a sunny but cooler day, what we call DELUXE weather in Florida. The Ecoflow app showed a whopping 400 watts, but only for a few seconds. It kept on charging in the low to mid-300 watt range. Now that it is 95° here, I’m getting no more than 300 watts and usually under that, in sunny weather. So, today, June 8, 2024, I recalled you experimenting with water to cool off a solar array; I gave it a shot. I was charging and getting a steady 263 watts with the panels grabbing the sun at the correct tilt angle and azimuth. I began watering at the top of the panels with a hand fan sprinkler, letting the water cascade down to the bottom. Within one minute the charge went from 263 watts to 313 watts and stayed there until I removed the sprinkler. The wattage slowly returned to 263. Armed with this knowledge, I might rig something up if and when we lose our power to a hurricane this season. (We've never lost water pressure in the past, only electricity.) That significant wattage increase may come in handy.

You can watercool the panel by making the backside watertight and pump water through it, and use that water in your heat tank or swimming pool heating. All in all, it's not worth the effort unless you really have a lot of difference between night and day, but the year itself is not changing that much. So if you do have cold nights, the heat is good for storage in a heat tank, and at night it keeps the temperature of the panels stable plus it lowers the amount of electricity needed to heat up cold water to 65+ celsius after it went through the heat tank. Be aware that you should either have cold water or hot water, but not in between due to legions disease that thrives between 20 and 60.

to be clear, efficiency increases below STC. The flow meter was a nice addition. One additional test would be periodic water flow. Save water and allows the water to evaporate, cooling the panels. This will depend on humidity which varies by day and region. Also, if the heated water could be used for things like swimming pool heating or hot water preheating, it gets a bit more cost effective. Water also block longer wavelengths of light (so red more than blue), so cooling the back of the panels might be more effective.

there's no way the extra 5% justifies the cost/waste of the water. Thanks for the video!

I really appreciated that you started with a control verification.

when i was getting my degree in this field, i met a guy that installs flat fin tubing on the back of panels and the water was cooling the panels and was used to generate heat through thermo heat generators, and some went to domestic use. the important thing to remember is to use as clean a water as you can if you are going to wet the panels to prevent degrading by mineral build up and water is a universal solvent and will destroy the frame over time

I remember reading years ago (early 2000's) that solar panels were more efficient in slightly overcast days, I have no idea if it was accurate or not, but this would kind of back up the theory that the panels work better at a cooler temp. Either way pretty interesting to me, thanks for making and posting this.

I have a small array in my yard with a 200ah lifepo4 battery. I use this for my pool equipment, outdoor lighting and power tool charging. You video made me start thinking of a way I could use my pool pump and reclaim the water to heat the pool.

This video gives me the idea of using patio misters to cool my 6 100w panels. Misting systems are very cheap and use little water, interesting. Thanks for the idea!

This is informative. I wonder if an internal cooling solution may yield even better results. Not only because the actual cells would be cooled but your also avoid any potential loss of sunlight hitting the cells due to the reflection and refraction from the water cascading down the glass. Might he something to consider for a future aide by side test.

Sundrum Solar has modules that attach to back of conventional solar panels and then use that heat generated for hot water needs, can be swimming pool, car wash, hotels or space heating.

You do a really nice job on these videos. Thanks for all the hard work you put in making your videos. Keep up the great work.

I not only have this set up for my 12.4K W backyard fence mounted system but I also have low pressure misters that clean my solar panel and pull my solar panels from 130° down to 88° increasing my total power production by 1200 W which is enough to run a small air conditioning unit. I also have a smaller version of a whole home water softener for lime scale.

Maybe you should recommend dual use panels. They harvest the heat with watercooling loops on the back of the panels. So you 1. cool your panels down to get a better efficiency (more Wh) and 2. You can harvest the warm water from the system via heat exchanger.This way you have not wasted any water and get the dual purpose use out of the sun energy

Thank you for all your efforts Scott, this video represents pretty much what YT *should be* about in my mind 🙂👍 A temp diff of almost 50% for a 5% gain in yield sounds pretty sobering to be honest. Even if this would vary up to 10%, will be it worth the extra investment for the required material, electricity (water pump) and the water itself, which will become a more valuable resource in the coming decades? BTW - have you observed a significant efficiency gain during winter then?

Ok, I have been thinking about this for a while so I cannot wait to watch this

This is also why early in the morning you can have your charge controllers trip on over voltage if you string is close to the max on your charge controller.

Majority of the cooling is from water exaporating off the panel so this could probably be done with much less water at intervals. A supprisingly effectave way to cool your house when the ac cant keep up is to hose off your roof a few times throughout the day.

As a standalone fixture, the potential savings are probably offset by the water and power pumping it. However, if were done as a multifaceted system that is cleaning the panels (keeping pv efficiency ratio up), cooling the panel and also heating water for internal use, then the compounding effect could make it a more efficient and cost worthy approach. I think we'll see more cooling systems in future, as pv panels become more efficient and cost effective.

I did a project on this effect in my heat and mass transfer class, the math behind it is very interesting but it's only a viable option at certain temperatures, I primarily studied the effects of wind on the efficiency

Yeah! I've noticed this in my van one day after it rained. Also, it's counterintuitive but my panel covers a ventilation vent in the van, and running the fan produces more power despite the fan load than not. One great use case for this is for an off grid tiny shack house with a single slope roof where nearly the entire roof is solar to block the sun. The water would keep the roof and shack cooler. In my case during those direct sun hours I'm running a 12v pump to filter rain water used for bathing, washing, cleaning and irrigation so might as well run it over the roof achieve this affect, which i think will also disinfect and heat the water.

omg thank you for showing both Celsius and Fahrenheit scales. much appreciated effort

Apparently the temperature coefficient changes with the age of the panel because I have some 14 yo panels with extensive spider cracks that have degraded by about 10-15% at STC, (basically when it's cool out), but when they really heat up in the summer the power output crashes. It was a simple test I did when they were very hot I took a hose and hosed down the panels. I saw over a 40% rise in amperage on my Amprobe. There could have been some SMALL variations in solar input but the sky was clear that day. It was an eye opener for me.

i think the data is tainted due to the sprinkler tube being set up in a way that partially shaded the panel. i would say it needs to be rerun and setup in a way where each panel is equally shaded... 0% shaded. i like the experiment though, curious to know what the real results would be

We can place finned heatsinks behind the panels and wet these heatsinks regularly with micro sprays. In this way, semi-passive cooling can be achieved by evaporation on the increased surface of the heatsinks with fins. If we ignore the heatsink cost, I think this will be the most viable solution that provides the highest efficiency... I love your videos, keep it up. Thanks.

Instead of pouring lots of cold water on the panels, you could try to spray a little mist. Then water evaporating would cool the panels with minimal water consumption.

Actually a negative power loss if you (should) distill your water to prevent lime buildup on your panels.

I love your videos. I’ve been researching a solar heater for my pool. It may be possible to combine the tubes from a solar header with panels to make a cooling system.

Such a cool experiment! Can't to wait to see what else you've got planned!

Thank you for the testing..really appreciate it.. I think refraction help to improve the efficiency. This is how ETFE panel works.

"My current power bill" . . . I see what you did there ;-)

"Combined heat and power" is so often an explicit benefit (steam from power plants at large scale, cars at small scale) that I'm surprised there aren't more systems doing it! I know water and electricity don't "mix" and it would be more complexity, but I would have thought all the puzzle pieces are already here given existing products like water-cooled CPU coolers. Must be missing something still.... 🤔

Great video. I've wondered about this too.

Off grid 20+ years and heat loss is an obvious factor you can mitigate. I don't recommend using water though and the way solar installers mitigate it is by adding additional panels to make up what is lost in high temperatures and on cloudy overcast days. However, for DIY solar I recommend not putting your panels on a roof that is black or dark as that will increase heat loss even more and use a ground mount system over dirt or light colored rock. You can also increase air flow to the back side of the panels by removing obstructions and if possible set them so the natural wind patterns flows across the panels. Even a light breeze makes a difference. A ground mount system with adjustable tilt and angle or a solar tracker is optimal. I also recommend a ground mount system so you can wash the dust and bird crap off your panels and check and do any maintenance needs. My system gets washed off a few times a week. My system is 1.4Kw ground mount with 600Ah LIFEPO4 batteries and Geneverse 200Ah and ALLPOWERS 200AH power station for extra capacity and that runs everything: water pump, lights, microwave, laptop, evap cooler, ebikes and recharges lots of tools and gadgets.

If the mini power meters are not calibrated, you may need to swap their positions to convince both read the same manner.

Great video! You can also filter the water and pump it back through a heat exchanger. While not ideal, and it is more complex, there are ways to do this without using the water once and throwing it out.

People have been playing around with this idea since the 1980s! It is 100% impractical, but it does work! 😂 not a single commercial application of this idea has ever been implemented successfully. There is a warehouse north of Los Angeles that is stacked with gently used solar panels and you can pick up a 300 W module for about $40.

I thought everyone knew this? This is why you can make more energy on cool sunny days...

Water drops may also locally concentrate sunlight to a very small area, etching the silicon of the panel.

That's actually less of an improvement than I expected, but now that I think of it, cooling the outside of the glass isn't going to cool the solar cells by much due to glass being a pretty good insulator. Also, one risks cracking the glass. Generally speaking it isn't worth trying to cool the panels due to the extra complication. Easier to just add additional panel(s).

I was in between Phoenix and Tucson this summer driving past a huge solar farm. I can't imagine how much their losses are in that 115 deg sun. I also couldn't imagine trying to cool them either.

Good test. You know many people have wanted to try this.

Awesome test, with a large enough system it's worth running a chiller and recirculation of water. I got up to 16% gain. Love these tests 👍

It looked like the PVC was casting a thin shadow across the top of the panel. that will cause a big drop in efficiency. Ideally you would only need to use as much water as necessary to evaporate on the panel and not run off.

good idea, to save on water cost, i would recommend recycling the water that you use for your panels. have a mechanism to collect and repump the water. i would use a solar powered water pump.

I have an old panel that is made with a bunch of ~12cm silicon wafers affixed to a white surface. The white area is obviously not completely wasted space if it serves to cool the wafers. Keeping the wafers round also reduces silicon waste too.

Nice video. I have 800w of ground mount Rich solar panels connected to an EcoFlow Pro and run the sprinkler in the heat of the day. I almost always get at least a 10% increase. It might be because I’m in Oklahoma and it’s 108 today 🤪. I checked my panels and even with water cooling they were 90+ degrees

I'd say some improvements are from cooling and some of the improvements are from light magnification from water droplets. Cool test tho. I'd say cooling the back side of the panel would give you a better knowledge of cooling alone without magnifying light on the front side

Thanks for the review of the concept. IMO, I guess another upside would be removing the dust build-up. Being from the SW-US, the other issues are: 1) Wasting water (I guess if you want to get complex, you could recirc it, but the more complex, the more things to break/maintain), 2) hard-water crusting/build-up on the panels (can be hard to remove), 3) what is pumping the water and what is its energy draw of that pump compared to the increase in power production (assuming you're not just tapping city water)? 4) if you have multiple rows of panels/large system, the plumbing to ensure all panels are cooled is a bit difficult. Finally, what about a simple air circ fan? Is that enough to actually cool the panel/... Probably not.

59 degrees F is about 15 C. You forgot to subtract 32 before 5/9! Love the everyday home stuff!

You could collect rain water, filter with a sand/charcoal. And use a small solar water pump to cycle the water… might do this for my solar shed 😁

Very interesting test. It doesn’t seem though like it would be worth it long-term. The cost of running the water just doesn’t seem like it would outweigh the benefit of 5%. Now if you had a closed loop system where you had a way to naturally cool down the water (without some kind of conditioner running), and all you had to do was run a small pump, it might be worth it. Again, very cool test. Thanks for sharing it!

POSSIBLE FOLLOW UP TEST: Consider a follow up test, to determine the quantity of power required, to run a pump to pump the water from a bucket, then use a rain gutter at bottom to direct the water back into the source bucket. Then subtract the power required from the power gained to get a net gain or loss from water cooling. thx

This has been on the table for decades.... Powerlabs, Engineering with Rosie, ..... have done this. The major point is cost efficiency. No use cooling the panels if the cooling costs more than the additional power from the grid would. I have seen water and air cooled panels (backside cooled) that use the extracted heat for heating purposes, but all those systems don't work well if you can't dump the heat somewhere. Running water over the front might even redude the light input into the cell.

Try a much slower drip rate. BTW it's really common in FL to have hybrid panels that channel pool water through the inside of a solar panel to both cool the panel and heat the pool.

I've certainly noticed this. My array produces more power on cool sunny days than on hot sunny days. My highest production days are actually during the winter! Of course it helps a lot that it only snows for a few minutes per decade in San Diego. This is why you should never mount solar panels with their backs against something solid, unless it's a good heat exchanger. They need the air flow to cool the backs. I think spraying the backs might work better than spraying the glass because they are in better thermal contact with the silicon layers.

As a boater on a liveaboard boat, sailing from point A to point B.... floating "flexible" panels on the water not only provides all the "free" real-estate needed for a 4KW system, it cools the panels and makes them more efficient. When not in use, it is rolled up on a spool (like your garden hose) and stowed there for later use....

Combining PV with channels would be great for people with pools. Not just for the gains in solar efficiency, but for the dual use in terms of roof space.

I wonder what would happen if you just attached black radiator fins to the back of the panel? Passive systems are always the best if you can.

Enhancement would be to swap the watering system to the other panel to nullify any panel performance discrepancies.

There is a company called Radi-cool that developed transparent film using a concept called radiative cooling to reflect just the infrared spectrum and passively result in cooler than ambient temperature in direct sunlight. Would be interesting to see this test done using the film instead of water.

Love the video! I was thinking of using radiant PEX on the back side of the panels with a closed loop evaporative cooler in the summer to cool the panels and my shop, then the same concept for winter to melt the snow, still a closed loop system but this time pulling the heat with copper heat exchange from the wood burning stove in my garage.. Im very curious of the 5% gain would be much higher without water flowing acrosse the panel surface, but cooling it from the back.

What if the water recirculates?

I have to wonder if there is a increase in power from the magnifying effects of the water and if having a mister would be more effective to increase power that way or creating a steady completely covering flow over the face of the panel would be more effective. Likely a full front of panel covering with water would be best as it would even out any magnification and provide the best cooling.

Nice experiment! I have rain barrels and a solar roof, I wonder if I could run something like this on hot days when I have full barrels. Would be interesting to measure how much water evaporates. I really wish there was some product that was solar panels+water (pre?)heating. Not surprising solar installers don't want to do plumbing but would be interesting if it worked out well. Bonus would be the circulating thermal fluid could help keep the cells clear of snow, too.

I've also seen a ton of improvement when I have cloud lensing. Usually about an extra 10% improvement.

100 gallons of water for 20 watts? Also good luck with that Cybertruck, you'll need it.

Had a friend that did copper panel backing with water lines running through it to pull heat from the the solar panel back in 07 as a some form of Master thesis, find myself looking for that final document now. To compare Results. He used his to heat the hot water/warm the house come winter. Wish I had the money to do something like that with my house, but that would be fresh constructions I am pretty sure for my design.

An idea I had was a rain collection system tied to the gutters. Then a solar powered pump taking the water out of the rain barrel/ibc tote to spray on the panels. Any water that didn't' evaporate would recollect in the gutters and refill the barrel. Sure you might have to add water from the tap occasionally but if you have enough tank capacity, maybe not. Add a low pressure timer so that it comes on during the hot part of the day and it would save water. I just picked up a simple solar water pump for $17 for another project. It would be enough to pump for 1-2 panels. so it can be done on the cheep. Just make sure the tank is in the shade so it stays cool enough.

Use rain water, or distilled or reverse-osmosis (without a mineralization filter). Mineral build up on the panel won't be happy for solar efficiency. My water has enough minerals that it will turn splashed surfaces white in a few days. (e.g. around an outdoor water feature)

Failed to include the cost of the water for the minimal gain. My water bill is routinely much higher than electric.

one guy did a flat rear cover then cut long opening on the bottom and put 3 120mm fans on the top. this seems to work amazingly

Thank you for this test. I can currently not use it, because it is to hard to acces my roof (2 stories) but i think this could be valid solution for everyone, that collects rainwater like i do. That would cost no water in that case and also makes installation easier, as the water only needs to be distributed but gets collected with the system that already collects rain water. As long, as the extra energy gained is more than what the pump needs, it should be usefull.

better filter those calcium.

It would be ridiculous to do that. Buy another panel

there is already a similar solution by using some hygroscopic foam at the backside of the panels. This foam is taking up the moisture during the cool nights and releasing it during the hot day. By this evaporation a cooling efect of the panels is obtained.

I would think maybe using the sub-ambient atmospheric window cooling panels might be a better option, you won't have the light scattering like you do with the water droplets

Thank you, Scott! This is interesting, I'd not heard about the heat losses so this is a good idea, if done right. Now, I want to see how to install a solar water heater. I'm ~43 miles north of Florida so I could really benefit from a solar water heater add-on. I want to do my own install because the install is, reportedly the most expensive part. The potential savings could be substantial, specially this far south. So that's why I suggest a video on installing a solar water heater add-on. Have a GREAT day, Neighbor!

So if your a farmer irrigating your crop, you could set up your irrigator with solar panels to follow the Sun and drip water on crops as it moves across the field. Always been a fan of gardens and solar panels occupying the same land. Check out gardening with solar panels.

Very cool. I could see adding a rainwater collection system and a 12 volt bilge pump for a boat in the future.

This gave me an idea to put my garden in front and under one of my ground arrays. I water the garden anyway, so I could let water run off the panels. My only worry is the water being too hot for my garden. I will have to experiment.

Nice video and info but I think you will find 59F is closer to 15C not 33C. I can see with a roof with water capture that the loss of water could be minimised outside of evaporation and that with enough hot days, solar on hand or a separate solar pump perhaps this still makes sense. Simplified with a sprinkler or misting system perhaps both cost and installation time could also be reduced.

You would also need to account for the water's absorption spectra vs. what wavelengths of light the panels use.

this is a great experiment, thanks for sharing. I've always wondered if better air flow under the panels would improve their performance in the same way. I love the way that panel skirts look (like Tesla uses), but also worried about heat. How about a small fan under the panels to help with some air movement? Might be a wash (and probably why it's not done).

Great to actually see the cooling done for the eyes to see. I wonder why panels couldn't become the actual ceiling of a home? The cooled home (in summer) would enhance power generation, and possibly even pay for the cooling cost? This could work in winter as well, because freezing panels lose performance. Panels perform best at 73°F or 23°C.

You can have a combined system that incorporates a passive solar water heater in the solar panels system.

I live in southern Mississippi and temps can be 110+ F for weeks. I wonder if cooling with atmospheric water would prolong the panel's life over time. Having a loop that feeds from the gutter on my roof could catch the water and feed it into a "U" shaped system that would make a small pump work easier. Problem is the water would eventually reach a temp not very far from air temp, maybe a 10F drop from air temp cooled just by evaporation. I could use a float value to keep the system at a needed level. One con would be the increased constant humidity might encourage mold or mildew growth. Another is the pump isn't going to last forever, and keeping debree out is an ongoing issue.

Good info.

I can see a line of shade from the water line to the cooled panel. That's bound to affect the measuring. If you drill the holes on the side of the pipe, you could place it further away and probably get better results.

I've run a large water reserve through those pool-heater panels to preserve low temps during peak loads, and a single panel running a refrigerant.