Water cooled solar panels for significant output boost

[shocksofmighty]

As well as the thermal cycling of the modules, mineral deposits on the modules, Both shortening the life of the modules. (in many areas you would have 1/8" of calcium deposits in very short order).

Avoided by using rain water which has little in the way of dissolved mineral content. I have observed no scale on panels using rain water, but if you use tap, sure there will be Mg2+/Ca+ pretty quickly.

As I pointed out earlier and backed up by the data there is little to no thermal cycling. Thermal cycling tests are used to determine longevity of solder joints in a module and are done by extreme cycling (-80 to +40-something C) as a proxy for long-term cycling over shorter temperature ranges. The decreased overall operating temperature could actually prevent thermal degradation during times of peak irradiation as the modules never see the extreme heat end of the spectrum. I say 'could'.

It is clear that you can get some (small, not significant) power via spraying some water on the modules. However, at a cost, maintenance, and risk that seems greater then adding more modules, which will add more power on a consistent basis

It is without a doubt significant if one were look at p-values, but I suppose you mean significance in the more subjective view point. I personally would say +2-4 kWH a day to be reasonably significant. But I fully agree that the absolute best way to add more consistent power is to add more modules, if that's an option.

[ButchDeal]

Mostly correct, but a bit simplistic maybe. It's more than the power for the pump. It also includes what amounts to a complete solar thermal collector system about equal in area to the PV array as well as all the piping, valves and other devices, controls and instrumentation. Then there's the maintenance. All that, in the case of what are marginal temperature differences in the optimum of situations, makes the economics a challenge that is, for most applications, still a bridge too far.

As well as the thermal cycling of the modules, mineral deposits on the modules, Both shortening the life of the modules. (in many areas you would have 1/8" of calcium deposits in very short order).

It is clear that you can get some (small, not significant) power via spraying some water on the modules. However, at a cost, maintenance, and risk that seems greater then adding more modules, which will add more power on a consistent basis

[foo1bar]

It also includes what amounts to a complete solar thermal collector system about equal in area to the PV array

No - it includes a cooling method (ie. sprayed water)
A "collector system" implies the heat is collected, not just dissipated by evaporation of water.

the relatively lower availability of a low temp. difference situation like the thermal scavenging in a PV array.

"Thermal scavenging"???
you make it sound like the heat is being used for something, which it's not.
Are you thinking of a heat-pump system to do cooling instead of sprayed water?
Or a system that tries to utilize the heat of the array somehow?
That's very different than what's being discussed.

The blower example therefore, is probably not a good comparison

Actually it's a very good comparison.
The spray cooling improves the output of the array, just like a turbo improves the output of the engine.
Each is improved a small percentage
The cost for each is only a portion of the improvement that's gotten from using the system..

The blower is easier to make work because its drawing on greater availability than the thermal collector.

As for the really big energy source - the sun - while it's pretty big, it's also pretty diluted.

Yes - but the real point is that it's the external source of energy in the system.
Because it is the source of energy, having a more efficient PV system (because of spray cooling) doesn't make it a "Over unity" system.
Just like a supercharger isn't an "over unity" system - it makes the entire system more efficient, BUT the source of energy is external - in that case it is the gas/diesel.

[J.P.M.]

There is no "Over Unity" to be seen here.
There is a really really big outside energy source called the sun.
It's providing all the power in the system.
A small amount of the power is being used to run a small pump, and that pump is causing the solar modules to run more efficiently, allowing more of the sun's power to be converted into power.

It's very similar to a turbo blower on an engine providing extra horsepower - yes the engine is powering the turbo, and that's decreasing the HP available - but the increased air pressure more than makes up for the HP needed to run the turbo.

Mostly correct, but a bit simplistic maybe. It's more than the power for the pump. It also includes what amounts to a complete solar thermal collector system about equal in area to the PV array as well as all the piping, valves and other devices, controls and instrumentation. Then there's the maintenance. All that, in the case of what are marginal temperature differences in the optimum of situations, makes the economics a challenge that is, for most applications, still a bridge too far.

In the case of the blower, it's purpose, in a thermodynamic sense, is to use some of the shaft work to add horsepower by utilizing the relatively high availability of the compressed air that would not be available without the blower, to raise the compression ratio, as can be seen in the increased distance (more pressure difference between the two isentropic processes on the P-V diagram) for the Otto cycle. The blower example therefore, is probably not a good comparison because of the greater availability wrung out of the cycle by the blower vs. the relatively lower availability of a low temp. difference situation like the thermal scavenging in a PV array. The blower is easier to make work because its drawing on greater availability than the thermal collector.

As for the really big energy source - the sun - while it's pretty big, it's also pretty diluted. So, while solar energy has low entropy - meaning for our purposes, and thanks to Prof. Einstein and the photoelectric effect, more versatility, it is also more diffuse with a quite low energy flux which makes it harder to utilize the lower entropy of the stuff. That's one reason, if you look back on the last 150 yrs. or so of solar progress (see: "A golden Thread, 2,500Years of Solar Architecture and Technology", Authors: Butti, Ken, and Perlin, John. Publisher:Van Nostrand Reinhold, New York, 1980, ISBN # 0-442-24005-8), many of the efforts have included methods to increase temperatures by concentration schemes to increase solar flux and operating temperatures and thus increase the thermodynamic availability - which BTW makes energy scavenging easier and more economically viable.

[shocksofmighty]

Nothing dangerous about the links. and not for you - NOMB what you do with your time. I do much the same. As an example: Having developed and used a procedure to measure my array's individual (16) ) panel temps. 8 time each over a 16 min. period used on more than 200 clear days (BTW, thermocouples as you seem to report using are not accurate for such purposes.) - but that is little more than fooling around and more the stuff of tinkering than serious.

I'm just tinkering as well, as I've explained on a number of occasions. In fact, if you decide to go back and look at my first post in this thread, I have no interest in the economic viability, or I would have stopped before I started. Thermocouples are not ideal, but they are consistent (certainly within 10% of actual), cheap, and I can easily string them together to get temperatures with my Raspberry Pi. Tinkering.

My reference to dangerous was for others who may think your investigations may be rigorous enough to stand critical peer review and so place some faith in them and as a result go out and buy some junk some charlatan is using to separate fools from their money. I looked at the stuff you're doing 40+ years ago. I was then and still is an idea whose time has not yet come, save for some specialized applications involving large scales temperature differences or high fuel costs, or combinations of those things.

I spend my work days submitting and reviewing manuscripts, granted in an entirely different field (when I'm not writing grant proposals). I, probably more than others here, would have a good idea of what types of results would be necessary to even consider submission to a peer reviewed journal. The results I've presented here sufficiently refute the likes of Sunking that were giving the OP grief. Nothing more. There is a net energy gain from this cooling system. You yourself have agreed that this would be the case in your theoretical example. I've taken it one step further and done the actual test. I could even argue that by doing the actual demonstration, I've done more to advance the idea that while this type of scheme can provide net positive returns (with data), it is too much of a pain to be something that anyone should consider for a normal rooftop install. That being said, the cost of materials that are in my latest version of the system are less than the cost of a basic 250W module and an optimizer/microinverter. I went through a number of iterations, however. I even got to have fun edifying activities like figuring out the difference between the theoretical (manufacturer reported) and actual pump head.

From what I've seen of your stuff, my opinion is that you lack the training, technical experience and equipment to understand why what seems to be your preconceived notions about a type of what are often and commonly referred to as energy scavenging schemes has a tougher hill to climb than you know of. Just my opinion.

Everyone's got one.

Most of the reason solar recovery schemes do not work well except perhaps for large installations or in warm to hot climates is due to Thermodynamics. secondary energy (heat) recovery, like any process operating between a heat source, the array and a sink, the heat load gets harder (read less cost effective) to recover as the temperature differences between heat source and sink become smaller. Entropy and the 2d law are against you more for small delta T's than large ones. Any extra energy recovered by improved PV efficiency is helpful, but not enough to swing the cost effective needle far enough - even though the extra electrical energy is much more ordered, and of a lower entropy making it more valuable. That's one reason why heat recovery schemes focus on the economics of the thermal recovery aspects of heat recovery. Lower quality, but much higher quantity.

Everything you say is fine and correct, but as I think foobar pointed out earlier, its an open system, not a recovery system in the sense I think you have put forth. There is convective cooling, but primarily it is evaporative. Not great on muggy days, but there is lots of latent heat in frames and glass. You can look at the graphs I presented and my array temp can be held roughly constant through the hottest part of the day which reflects roughly a ~13 degree drop. You can argue the exact temperatures from thermocouples aren't correct, but the relative temperatures certainly are, and is backed up by the apparent improved efficiency. I think we can agree that is not coming from convective heat transfer via spraying ~12L of water on the array every 3 minutes.

EDIT: correct 6L to 12L (6L per string) and from ~15 to ~13 degree drop

[J.P.M.]

Other than me climbing on my roof (for which I take necessary precautions) what is exactly dangerous about what I have presented? What is dangerous about all the links that were posted before or the papers I cited?

Nothing dangerous about the links, and not for you - NOMB what you do with your time. I do much the same. As an example: Having developed and used a procedure to measure my array's individual (16) ) panel temps. 8 times each over a 16 min. period used on more than 200 clear days (BTW, thermocouples as you seem to report using are not accurate for such purposes.) - but that is little more than fooling around and more the stuff of tinkering than serious.

My reference to dangerous was for others who may think your investigations may be rigorous enough to stand critical peer review and so place some faith in them and as a result go out and buy some junk some charlatan is using to separate fools from their money. I looked at the stuff you're doing 40+ years ago. It was then and still is an idea whose time has not yet come, save for some specialized applications involving large scales, temperature differences or high fuel costs, or combinations of those things.

From what I've seen of your stuff, my opinion is that you lack the training, technical experience and equipment to understand why what seems to be your preconceived notions about a type of what are often and commonly referred to as energy scavenging schemes has a tougher hill to climb than you know of. Just my opinion.

Most of the reason solar energy recovery schemes do not work well except perhaps for large installations or in warm to hot climates or applications such as power towers or concentrators is due to Thermodynamics. secondary energy (heat) recovery, like any process operating between a heat source - the array, and a sink - the thermal energy load gets harder (read less cost effective) to recover as the temperature differences between heat source and sink become smaller. Entropy and the 2d law are against you more for small(er) delta T's than large ones. Any extra energy recovered by improved PV efficiency is helpful, but not enough to swing the cost effective needle far enough - a few % of less than 20% of the input is not as much as, say, 10% of 80% - even though the extra electrical energy is much more ordered (of a lower entropy) making it more available (read versatile) and thus more valuable. That's one reason why heat recovery schemes focus on the economics of the thermal recovery aspects of heat recovery. Lower quality, but much higher quantity.

[shocksofmighty]

I do not think shockfofmighty is a SCAMMER. He is not that smart. Like everyone else on the Forum I think he is a Fool.

I think its pretty clear to everyone who has been watching this thread that you are wrong. Not only are you wrong, but your obstinance to the evidence and analysis provided by everyone here (JPM included) makes you not just a fool, but an ignorant fool. 100% hot air unless you are willing to debate specifics.

As for the Forum allowing it, All I can say is it is good comedic entertainment watching someone make a Fool out of themselves.

So you are kinda for free speech? That's great! That must just be the military in you, because the rest of you screams deplorable.

[foo1bar]

I really do not have a big problem with the Over Unity Crowd.

There is no "Over Unity" to be seen here.
There is a really really big outside energy source called the sun.
It's providing all the power in the system.
A small amount of the power is being used to run a small pump, and that pump is causing the solar modules to run more efficiently, allowing more of the sun's power to be converted into power.

It's very similar to a turbo blower on an engine providing extra horsepower - yes the engine is powering the turbo, and that's decreasing the HP available - but the increased air pressure more than makes up for the HP needed to run the turbo.

[Sunking]

I do not think shockfofmighty is a SCAMMER. He is not that smart. Like everyone else on the Forum I think he is a Fool.

I really do not have a big problem with the Over Unity Crowd. As long as they stay on websites and talk among themselves keeps them out of the public eye doing no harm except wasting their own time and money being foolish and ignorant.

As for the Forum allowing it, All I can say is it is good comedic entertainment watching someone make a Fool out of themselves.

[shocksofmighty]

FWIW, I don't think Shocksofmighty is a scammer as much as a wishful thinker and an example of how a little knowledge can be a dangerous thing if uncontrolled or untempered..

Other than me climbing on my roof (for which I take necessary precautions) what is exactly dangerous about what I have presented? What is dangerous about all the links that were posted before or the papers I cited?

[J.P.M.]

Although some people (I am not saying shocksofmighty is one of them) continue to try to sell you equipment to cool off your panels and make is sound like it is the best thing since slice bread.

I would call that pretty close to the "S" word.

FWIW, I don't think Shocksofmighty is a scammer as much as a wishful thinker and an example of how a little knowledge can be a dangerous thing if uncontrolled or untempered..

[SunEagle]

So, not a scam but not really practical except in a few limited situations.

Although some people (I am not saying shocksofmighty is one of them) continue to try to sell you equipment to cool off your panels and make is sound like it is the best thing since slice bread.

I would call that pretty close to the "S" word.

[J.P.M.]

So, not a scam but not really practical except in a few limited situations.

I'd agree, but to paraphrase Kipling a bit, scammers will use wishful thinking and ignorance to twist the truth and make a trap for fools.

[shocksofmighty]

Your data presentation and lack of description, but my ignorance is of no real import.

I'll take this to mean that you are not interested in my explaining further? If that is not the case I will be happy to do so.

Butch's attachment post has the types of information and references to other sources that have gone before you, and are of the type I've been using for a long time. While your stuff is interesting and informative for you and me as well, it appears that you, like many others in a way that's becoming more common, have not looked for or noticed what's already been done in an area of research and are reinventing the wheel or covering ground that's already been travelled.

Actually, you are wrong there. I have looked a fair bit of literature associated with cooling. You'll note that most of what Butch presents and the links therein relate to specific PV/T systems that contain thermal modules or forced air. I wasn't going to be designing one of those so my focus was on what had been done as it relates to direct water contact on the panel surface.
I personally found Wu and Xiong's approach (http://ijlct.oxfordjournals.org/cont...5/ijlct.ctu013) to be quite clever. They had a conservative ROI of 14 years, but as I was not even interested in ROI (see my first post in this thread), I wanted to try something more like Moharram et al. (http://www.sciencedirect.com/science...90447913000403). This was more straightforward to put together with the materials more readily available. I also don't see any problem in covering ground that has already been covered. In the scientific disciplines (where I'm coming from) it is in fact vital.

That's one theme I and others have been posting about in this thread, and maybe why Butch's 0903 A.M. post is due an attoboy for elegantly saying/showing the same without the histrionics.

Yes, there is interesting stuff to read there and the lack of histronics is a refreshing change for this thread.

[Ian S]

For small systems the thinking seems to be it ain't worth the money or hassle, and for large systems a better probability of being cost effective in warm/hot climates , but not where cheap fuel is available.

So, not a scam but not really practical except in a few limited situations.