Water cooled solar panels for significant output boost

[J.P.M.]

See the original description. It was a comparison to two control panels that were not cooled, then extrapolated to the system as a whole.

I've slowly been modifying my design to go from a pop-up sprinkler to individual micro sprinkler heads for each column of panels. Once it is back in action I'll provide overall production and individual panel outputs for those that want to look at it.

Again, I'm just having fun ( and sunking is still wrong).

Is that the one described in your 05/26/2016, 1:43 P.M. post ?

[shocksofmighty]

Unless the experiment is not well done. How was the 4 % determined ? Kind of tough without a pyranometer.

See the original description. It was a comparison to two control panels that were not cooled, then extrapolated to the system as a whole.

I've slowly been modifying my design to go from a pop-up sprinkler to individual micro sprinkler heads for each column of panels. Once it is back in action I'll provide overall production and individual panel outputs for those that want to look at it.

Again, I'm just having fun ( and sunking is still wrong).

[J.P.M.]

From a previous post from someone who actually built one:
"Taking into account all pump usage, I'm getting a 4% (daily) boost."

One experiment is worth a thousand expert opinions.

Unless the experiment is not well done. How was the 4 % determined ? Kind of tough without a pyranometer.

[jflorey2]

Maybe, maybe not. More than likely possible, but not practical or cost effective.

Agreed. Given how cheap both PV and solar thermal panels are lately, there's no advantage to combining the two (outside of some very contrived situations.)

[J.P.M.]

The amount of energy you put into the cooling is greater than the power gained.

Maybe, maybe not. More than likely possible, but not practical or cost effective. See my latest epistle.

[J.P.M.]

If I may:

If I have a pump that delivers say 6 GPM using a motor that draws 80 W (and I do), and assuming I can design an array cooling system - very probably not cost effective BTW - that will reduce my array's operating temp. by say 5 deg. C. (and I bet I can, having designed all manner of cooling systems and devices for a good part of an engineering career), I'm also pretty sure I can see an improvement of a PV system's efficiency by about 2.5 %, assuming a 0.5 % increase per deg. C. lower array temp. - that is, reduce the array operating temp. by 5 deg. C.

Using my array (because I know a lot about it), set the following conditions without aux. cooling (using actual data from 11/08/2015) :

POA Irradiance: 838 W/m^2
Array operating temp.: 49.5 C.
Ambient temp.: 25.7 C.
Efficiency before inverter loss @ stated operating conditions: 18.2 %
Angle of incidence for beam radiation :31.7 deg.
Estimated glazing reflectance 4.3 %, based on ARC reducing reflectance by 50%

The temp. diff., array - ambient = 49.5 - 25.7 = 23.8 C.

If I'm going to knock 5 deg. C. out of the array temp, and assuming ambient loss coeff. are linear with respect to temp., I'll need to reject 5/23.8 = 21 % of the energy that's rejected as heat via convection to the ambient or radiation loss to the sky and surroundings.

A simple energy balance on the array, assuming for now and for simplicity that heat conduction loss through the frame is negligible:

Irradiance input = 838 * 26.09 m = 21,863 W
Reflection loss = 21,863 * .043 = 940 W
Array output = 21863 * .182 = 3,979 W
Approx. array total heat rejection rate = 21,863 - 940 - 3979 = 16,944 W.

Of that 16,944 W, or approx. 57,800 BTU/hr., 21% or approx. 12,000 BTU/hr. will need to be pulled out of the array via my cooling system and rejected to, say, my swimming pool.

A 6 GPM, the cooling water will increase approx. 2.2 C. as it passes through the array in an as yet unspecified manner.

(I'm leaving out a boatload of design details here, not because they're technically insurmountable, just boring and not necessary at this stage. )

Now, if my array temp. drops by 5 deg. C, and the array efficiency increases by 2.5 %, up to .182 * 1.025 = .187, that will increase output by (.187-.182) * 21,683 = 108 W.

Since my pump needs 80 W, there is a net gain of 108 - 80 = 28 W.

A comment or two:

1.) The numbers I used for the array output before aux. cooling are actuals. The add on cooling system numbers are theoretical, but a I wrote, based on a lot of design and sizing of heat transfer equipment and also drawing on my solar water heater system plumbing (which I also designed). There is little doubt in my mind, and a fair amount of confidence that the numbers are technically feasible.

2.) Technically feasible and practical/serviceable/cost effective are two different animals. Annual saving or additional production from such a system would amount to a savings of something like :
($0.17) *(28/1000) * (say ~ 3,500 hrs./yr.) ~ = $ 17/yr. I doubt it would be cost effective to design/build an aux. cooling system as the cost would probably be a couple orders of magnitude more than the annual savings, even ignoring increased maintenance and servicing costs, not to mention the PITA factor.

So, technically possible from thermodynamic, heat transfer and fluid mechanical considerations - yes, none of those laws/considerations are violated. However, from a practical standpoint, in my engineering opinion, it is neither practical, nor cost effective to provide aux. cooling as I've described it.

Lastly, for a lot of reasons, mostly having to do with pumping costs related to high specific volume of gases, and ambient winds often working at cross purposes to fan pumping of air over arrays as well as poor heat transfer rates of gasses (air) vs. liquids (water), fans blowing air over arrays are probably less cost effective due to pumping costs, not to mention what's probably and aesthetic wet horror dream.

Now, can we get back to professional conduct ?

As usual, take what you want of the above. Scrap the rest.

[jflorey2]

The amount of energy you put into the cooling is greater than the power gained.

From a previous post from someone who actually built one:
"Taking into account all pump usage, I'm getting a 4% (daily) boost."

One experiment is worth a thousand expert opinions.

[Sunking]

No it doesn't. You are simply increasing the efficiency of the system. Nothing there that violates the laws of physics.

The amount of energy you put into the cooling is greater than the power gained.

[sensij]

You idiot. You do not know the difference between an energy source and a carrier of energy. There is no net energy gain, only a loss. I bet when you were a kid you bought watermelons for $1 and sold them for 50-cents. Then claimed to make up for the losses with volume. Problem is I out smarted you. I was the one you bought them from, and I stole them from the farm. the night before.

I bet you believe in HHO and Hydrogen fuel economy.

If you could take 1 unit of energy, and turn it into 1.01 units of energy, you would be the richest person on earth. In fact you would rule the world and be the King of the World as the world would revolve around you and your off-spring until Armageddon.

Easy, fella. Breathe a minute, and consider that there are non-electrical forms of energy in this system. Changing the distribution between light, heat, and electricity (or other forms) does not violate energy conservation. Adding a small amount of electricity in to improve the panel efficiency can return more electricity out (and less heat out) because as the panel efficiency changes, the distribution changes.

There are economic challenges to operating and maintaining a water cooling system, but the laws of physics are fine with it. Just because something is physically possible doesn't mean it will be economically viable.

[jflorey2]

Impossible. It violates all laws of physics.

No it doesn't. You are simply increasing the efficiency of the system. Nothing there that violates the laws of physics.

[Sunking]

It isn't a net gain in energy. It is a net gain in electricity. There are other sources and sinks of energy in this particular control volume than just the electrical connections.

You idiot. You do not know the difference between an energy source and a carrier of energy. There is no net energy gain, only a loss. I bet when you were a kid you bought watermelons for $1 and sold them for 50-cents. Then claimed to make up for the losses with volume. Problem is I out smarted you. I was the one you bought them from, and I stole them from the farm. the night before.

I bet you believe in HHO and Hydrogen fuel economy.

If you could take 1 unit of energy, and turn it into 1.01 units of energy, you would be the richest person on earth. In fact you would rule the world and be the King of the World as the world would revolve around you and your off-spring until Armageddon.

[sensij]

Impossible. It violates all laws of physics. Nothing is above unity gain. If there was a net gain in energy, then the economics would work. The economics do not work because there is no net gain in energy.

It isn't a net gain in energy. It is a net gain in electricity. There are other sources and sinks of energy in this particular control volume than just the electrical connections.

[Sunking]

1. There is a net power gain from cooling the panels. i.e. You get more out than you put in from running the pump.

Impossible. It violates all laws of physics. Nothing is above unity gain. If there was a net gain in energy, then the economics would work. The economics do not work because there is no net gain in energy.

[Sunking]

Yes, you call B.S. quite often, and you do so with a heavy hand. It's painful to be on the receiving end, especially when it's unwarranted.

BS again, you are asked to be attacked, and when you get what you ask for complain and whine to the Admin.

[Sunking]

Perhaps you object to my posts because you can't stand enthusiasm about engineering,.

No because you are clueless activist who knows nothing about what you advocate. You only have passion, not knowledge. It all about how it feels to you and has nothing to do with proven facts and the laws of physics. You are Green Mafia and propaganda is your tool. You are a very easy person to track. You have the same MO on every forum you participate in. You spend your whole day promoting your activism cruising the web spreading your flavor of Propaganda. Russ and I nailed you the first day you showed up.