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Cooling Solar Panels?

04/19/2019 12:22 PM

I hear that solar panels lose efficiency with temp increase. I wonder if I were to rig a misting system on my panels if it would be worth the cost of water? Anyone doing it yet?

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#1

Re: Cooling solar panels?

04/19/2019 12:35 PM

I doubt it would be worthwhile unless this could be done passively. For instance, if your panels were near water higher than the panels then a gravity-driven siphon of water could drip or spray the panels to cool them.

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#18
In reply to #1

Re: Cooling solar panels? Ocean Mimicry, Passive Convection

04/21/2019 3:28 PM

Ocean Mimicry, Thermal Tractor

Yes, passively. But if you have a water reservoir higher than your panels, you can
use a mostly closed loop with a manifold under the panels at the lowest point of the
loop. The density of the water in the manifold will drop as it warms, powering the
flow in the loop as incoming higher density cool reservoir water displaces the warming water. The warm water rises into the return pipe and ultimately returns to the reservoir.

To save on pipe costs, you can open the loop under the water in the reservoir.
The openings in the reservoir should not be too close together and the warm water return should open somewhat higher than the intake. Both connections to the reservoir should be as far beneath the surface of the reservoir water as you can easily make them. Understand that the thermal gradient you create in the reservoir will form an unpiped circulation within the reservoir. Huge amounts of heat can escape the reservoir through evaporation at the reservoir water surface which might have enormous total surface area. If you experience any fouling in your piping, you may be forced to close your loop at the bottom of the reservoir but, if you do, be sure to create a large thermal transfer surface area between your loop and the reservoir water.

Realize that a totally closed loop causes additional flow resistance within your loop.
With a closed loop, consider filling your loop with sterilized water. Also, consider
adding a water hammer eliminator dead end to buffer any pressure extremes in your loop. This water hammer eliminator could be implemented with a vertical dead end pipe with a Schrader valve so you can add an air pocket pressure accumulator. I would install a pressure gauge in this vertical pipe to allow monitoring the pressure as well as a small diameter parallel vertical transparent pipe to view the air level. A very small pipe running from your bottom manifold could allow this accumulator and gauges to be placed some distance from your panels for convenient access and frequent inspection.

Use large pipes with the cold input to the manifold at the bottom of the panels
and the warm outlet from the manifold at the top of the panels. Use the largest
diameter pipes you can afford especially for the reservoir supply and return.
Insulate the cool water supply pipe. The manifold assembly should have a large diameter pipe at the top and bottom but the pipes under the solar panels can be smaller in diameter since they are in parallel. Resistance to flow at every possible
cross-section of the flowing loop should be approximately uniform. As much as you
can, make the slope of the reservoir access pipes uniform so that air cannot become
trapped and impede the main flow.

Not dripping or spraying around your panels reduces the chance of contamination and
corrosion of your panels. Any leaking of your piping should be repaired promptly.
If your water brings your manifold under the dew point you can get condensation under your manifold pipes, so design your system to deal with that possibility. Make provisions for directing any condensation drips from your manifold away from your panels and into a proper drain.

If your installation is subject to freeze, you will want to provide a means to winterize your loop during cold weather, probably with shut off valves at the reservoir and a drain near the bottom of your piping. Then you can evacuate the water from all your piping whenever cooling is unnecessary or when any repairs are needed.

By manifold in this discussion, I mean a big diameter pipe feeding many small diameter pipes then the small diameter pipes feeding back into a large diameter pipe. Most likely the small pipes tap into the large diameter pipe at 90 degrees, run in parallel under the PV panels and then enter another large diameter pipe at 90 degrees to continue the large diameter pipe loop. Many geometries are possible as long as you take care not to create bottlenecks in the loop cross section flow resistance.

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_________________________________________________
<<<<.................................................................................................... |
______warm water return pipe_________________________|
." " " " " " " " " " " " " " " " " " " " " " " " " ".
." " " " " " " " " " " " " " " " " " " " " " " " " ".
." " " " " " " " " " " " " " " " " " " " " " " " " ".
." " " " " " " " " " " " " " " " " " " " " " " " " ". < PV Panels on top of small pipes
." " " " " " " " " " " " " " " " " " " " " " " " " ".
." " " " " " " " " " " " " " " " " " " " " " " " " ". ^ direction of small pipe water flow
." " " " " " " " " " " " " " " " " " " " " " " " " ".
." " " " " " " " " " " " " " " " " " " " " " " " " ".
_____________________________________________________________________
|" " " " " " " " " " " " " " " " " " " " " " " " " " <<<< direction of large pipe water flow..
|______cool water supply pipe_____________________________________________

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#2

Re: Cooling solar panels?

04/19/2019 12:47 PM

I think the accumulation of scaling of minerals from the water would be detrimental...not to mention increased oxidation...An internal piped cooling system might work, but I don't think it would be cost effective...

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#4
In reply to #2

Re: Cooling solar panels?

04/19/2019 1:28 PM

They do make dual purpose panels....don't know how well they work...

https://dualsun.com/en/product/panels/

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#5
In reply to #4

Re: Cooling solar panels?

04/19/2019 2:19 PM

I see on the website that they have a simulation program that you can use if you register. That could answer a lot of questions if it is well done.

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#3

Re: Cooling solar panels?

04/19/2019 12:49 PM

A misting system would probably leave you with mineral deposits and attract dust. Filtering and conditioning would be required.

You could attach cooling coils to the rear of the panels and use the cooling liquid for domestic hot water or as a preheat for the hot water system. There are solar hot water systems that do this and have some payback. If it also helps your panel efficiency, it may be worth the cost.

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#6

Re: Cooling Solar Panels?

04/19/2019 8:07 PM

I hear that solar panels lose efficiency with temp increase. I wonder if I were to rig a misting system on my panels if it would be worth the cost of water? Anyone doing it yet?

I'm sure it depends on the ambient temperature.

Here is a paper written about it.

https://www.sciencedirect.com/science/article/pii/S2090447913000403

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#7

Re: Cooling Solar Panels?

04/19/2019 8:49 PM

I like the cogeneration approach people have suggested. Turning waste heat into redirected heat seems like a good idea, at least in general.

But if one has so much solar energy that your solar panels become less efficient from self heating, so what? You already have full potential power coming out of the panels at this point in time and likely your energy storage or energy sharing capability has already maxed out. The fact that you are not using all of the available energy converted from light will much more dramatically reduce efficiencies.

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#8

Re: Cooling Solar Panels?

04/20/2019 12:38 PM

"worth the cost of water"? How about worth the cost of electricity/materials/labor to supply the water? Seems to me a finned heat sink for air cooling would be better.

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#9

Re: Cooling Solar Panels?

04/20/2019 10:44 PM

Per degree rise in temperature, solar PV panels lose 2.2 millivolts. So it is better to cool. With mist cooling however, there could be a thin layer of water, which would reflect sun light too. Secondly, no water is perfectly pure. It always contains some salts. Over a period, these salts would solidify on the surface too.

Perhaps the better option would be to paint the underside with a black paint. Black surface would help in taking away heat, if the ambience is cooler, and absorb, if it is hotter. Since we always place the panels at an angle to the horizontal, there would be a sort of chimney effect, making air flow upwards, carrying the heat absorbed by the black surface, and thus have a passive cooling.

Alternately, you could always have a water jacket below the PV surface, but that would involve higher costs and cost of pumping water, as well cooling.

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#10

Re: Cooling Solar Panels?

04/21/2019 1:53 AM

Could you reutilize the heat on the panels to run a refrigeration cooling system ?

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#24
In reply to #10

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles

04/22/2019 8:59 PM

Cooling Roof Tiles

There is a serious effort underway to produce an on-chip gas chromatograph. The ammonia(or other chemistry) absorption refrigerator has existed for many decades. It strikes me as way easier to produce a nanotech roof tile with embedded absorption refrigeration than to produce an on-chip gas chromatograph.

There used to be consumer ammonia absorption refrigerators that ran silently with no compressors, just a pilot light heat source and a few check valves as moving parts. Safety became too much of an issue with that much ammonia in the home and with cheap electricity and modern style chloroflourocarbon compressor working fluids the absorption refrigeration was relegated to commercial installations where the safety could be better insured and the water/NH3 efficiency was compelling.

A PV panel with builtin nanoscale absorption refrigeration could conceivably be a match made in heaven for high solar availability states like my own TX. When you have a lot of sun and need a lot of refrigeration these roof tiles could be wonderful. The cooling of PV materials could be a valuable side effect of appropriately designed integrated systems.

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#30
In reply to #24

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles

04/23/2019 7:03 PM

It seems like heat rejection would be a significant hurdle to developing a practical nanoscale absorption refrigeration roof tile.

The hottest part of the tile will be the top in direct sun. The hottest part will necessarily be used for the generator/regenerator portion. Heat transfer dictates some separation will be required between heat source and heat sink for continuous operation, so with heat being introduced on the top of the tile, heat must be rejected elsewhere....

Into the attic, or even just under the tiles seems like a bad place to try to reject heat if this application is a response to high summer temperatures. Similar problems would beset attempts to use this for solar panels and have the system neatly contained to just the panel footprint, i.e. if the panel surface is the high temperature, where do you reject heat that won't immediately heat what you're trying to cool, and how can you use what you are attempting to cool as your driving heat source for said cooling?

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#31
In reply to #30

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles

04/23/2019 8:43 PM

"It seems like heat rejection would be a significant hurdle to developing a practical nanoscale absorption refrigeration roof tile." Well, I don't know much about that technology. But, I do know that enough nano particles could make a lot of beaches. It can add up. If it didn't, it wouldn't absorb enough heat in the first place. I just don't see the problem of cooling anything. When there's a will there's a way. It's usually the will that's the stumbling block. "heat must be rejected elsewhere....". Well,sure. But why is that a problem? "Into the attic, or even just under the tiles seems like a bad place to try to reject heat if this application is a response to high summer temperatures" Not if it's done in the winter to heat the house. In the summer, it could go to another/different heatsink/load. Why not? "if the panel surface is the high temperature, where do you reject heat that won't immediately heat what you're trying to cool". That's like saying about the PV panel, "...have the system neatly contained to just the panel footprint, i.e. where can you use that electricity that won't immediately heat that same system. (is a short-circuit the only circuit you can imagine?)" That's what conductors/pipes are for: to transport the product to a usable area. What's the problem? "...how can you use what you are attempting to cool as your driving heat source for said cooling?" Well, the only way to use a steam boiler, is to withdraw steam (cool) from it. Again, what's the problem? In fact, you can't use any heat at all for anything without cooling the heat-source. If the heat-source stayed hot, then there was no heat xfer. "...as your driving heat source for said cooling?" There are many ways. A lot of things can use heat as a driving force. And, it doesn't have to be mounted on the back of the PV panel. Even PV panels themselves have remote parts to the system. You are not limited to the footprint of that panel. However, the footprint of that panel is probably all you need to cool, until you go to the next panel.

A lot of people already use reversible heat pumps for heating/cooling. In summer, it's an air conditioner. In winter, it's a heater. To be reversible, the evaporator and condenser need to switch functions. As an air conditioner, the condenser needs to be outside in the shadiest/coolest spot to dissipate/waste the heat, and the evaporator needs to be inside somewhere to cool the house/room. As a heater, the condenser needs to be inside to heat the house/water, and the evaporator needs to in a sunny/hot spot outside to collect the most heat. The inside heat exchanger might need to be floor-level for heating/condensing, and ceiling-level for cooling/evaporating. Therefore, the heat exchangers need a different location for each of the functions. Before refrigeration, there used to be natural ice imported from cold areas to hot areas, and survived when insulated well. Even if you could not recover the heat from that PV cooling system, There's a tremendous amount of more heat already getting wasted by air conditioners. I'm sure that system can be improved, too

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#32
In reply to #31

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles

04/24/2019 6:35 AM

Do you really want to know, or are you just feeling testy?

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#33
In reply to #32

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles

04/24/2019 7:53 AM

Let me put it this way. If I said something wrong, please let me know so I know don't do it again.

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#34
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Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles

04/24/2019 11:42 AM

My comment was about absprption refrigeration of the type that is powered by a heat source and a heat sink being able to contained within a reasonable roofing tile.

Your comment about heat pumps powered with electricity generated elsewhere with good separation between evaporator and condenser is not a good analogy.

Absorption refrigeration powered by a heat source and sink would be very difficult to contain in something of the shape of a typical roofing tile where the dimensions of the two faces are much greater than the small dimension of the sides (the thickness). Absprption refrigeration systems typically require at least three differeny heat reseviors.

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#44
In reply to #34

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles

04/24/2019 6:52 PM

Oh... The absorption part, I missed. For some reason, I was thinking of absorbing heat instead of refrigerant. I should have known better. I am familiar with lithium-bromide units. It just didn't occur to me. Sorry.

I didn't catch it from the title of the post. For some reason, the title changed from the original post. I didn't catch it.

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#36
In reply to #30

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/24/2019 12:22 PM

Roof Tile Example Details Straw Man

There seems to be skepticism that a roof tile can contain a good refrigerator.
OK. As a straw man consider the following roof tile constituent elements:

1) Louvers for shading metal heat emitter
2) Metal heat emitter(upward facing surface under louvers) in contact with external air
3) Heat emitter metal sticks through wall of evacuated envelope and is thermally isolated
from the other stuff inside the envelope except for the hot reservoir(see 7)
4) A layer of insulation is above reservoir(C). C combines fluids and cools the other
metal plate(the cool one.)
5) The metal cool plate separately penetrates the envelope and is in contact with air under
the tile(domicile air) and PV's within the envelope.
6) The PV material faces upward through evacuated envelope toward sun.
7) An insulation layer under reservoir(H). H separates the working fluids using heat.
8) Evacuated envelope allows sunlight to hit H reservoir within it from above.
9) Tiny tubes w/ check valves circulate fluids between H&C.

If electrically actuated valves can be used to improve the efficiency of the
absorption refrigerator significantly then do it.

Yes, I know complex 3D geometry is necessary to get all of these
pieces in the right place, thermally isolated, and at the right elevations.
Is anything worthwhile trivally easy ?

Basically, the critical geometries are achieved with chip like microlithography.
There will need to be a light bulb style pump down of the vacuum envelope.
The vacuum envelope may not be ultimately necessary but for prototyping I
would use one for reducing conductive parasitic heat transfers between the
two working fluid reservoirs, both each other and surroundings.
Yes, I am aware that there can be radiative parasitic heat transfers which will
need minimization as well.

I believe that the system can work well without solar tracking, but solar tracking
could improve system efficiencies. I do not think it is worth the added costs.
Generally, run the louvers East/West and optimize all dimensions for peak summer
optimal operation to get the most return for your investment.
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#37
In reply to #36

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/24/2019 1:21 PM

By the time this is all done and costed out, machine process changed, it will be cheaper to stay on the grid.

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#38
In reply to #37

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/24/2019 2:53 PM

Scaling is a Powerful Concept

Yes, and my Wilson Pickett slide rule was cheaper in 1969 than the Friden four banger plus square root console calculator in the physics lab lounge room by 100X but it did not stay that way. Scaling is your friend. These techniques ultimately make the homeowner less dependent on big business and government for continuity of lifestyle during change/stress. Using power where intercepted is a well known fundamental principle for overall efficiency and cost savings.

The grid, by the way, is a great place to bank energy savings. Reduce peak demand and you save big bucks. Here in TX peak demand is during summer when everyone's HVAC is struggling to keep up. Also, with nearly zero moving parts, these tiles should prove very long lived. For anyone who cares about womb to tomb complete cost analysis, these tiles should cost out quite respectably. The only thing I know which should beat them is my IR retroreflector bead scheme and those could be glued onto the louvers.

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#39
In reply to #38

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/24/2019 3:16 PM

A product that has yet to be prototyped, let alone field tested will outlast and have lower lifetime cost than existing technology. Will it cure my asthma, too?

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#40
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Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/24/2019 3:55 PM

"Yet to be Prototyped"...Hardly

Roll all you like. Ammonia absorption refrigeration is the dominant large scale refrigeration technique(due to cost) and all I am saying is that it is easier to do nanoscale than gas chromatography. It really is not invention, just scaling. All the patents one needs are already documented at the US PTO. This particular application of all those techniques as a roof tile system may be novel but the technology itself is largely OTS.

Scaling electronics took the Space Program to overcome the sociological resistance to making super small transistors and thus calculators. I am not surprised that the nano-refrigeration analog receives such inane contempt.

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According to the International Institute of Ammonia Refrigeration (IIAR), ammonia is 3 to 10% more thermodynamically efficient than competitive refrigerants.

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#43
In reply to #40

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/24/2019 4:53 PM

Reading More Deeply

Apparently, the large scale refrigerators are anhydrous ammonia used in a compressor style refrigerator. I was mistaken in believing that they were absorption type. The efficiency of the absorption types (there are many variations) is far lower than I had thought but it was still enough for the US PTO to issue a patent in the 1800s for a home refrigerator which had commercial success for a while. I still think that this is prototype enough. The value of using a solar heat source to operate a compressor free refrigerator is too compelling and gains all that long life which so enthused me.

The safety issues with ammonia are for large volumes of ammonia. They are thus unimportant in an nanoscale device.

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#45
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Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/24/2019 7:10 PM

You never can tell. Mass-production can sometimes reduce those costs drastically. If it works decent enough and catches on, it just still might become affordable. Who really knows until it's given a chance? Even the light bulb had a rough start.

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#48
In reply to #36

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man

04/25/2019 12:43 PM

A rooftop solar powered absorption refrigeration system is feasible, perhaps even sensible. However, getting the system to be self contained in what might reasonably be considered a roofing tile with appreciable benefit still seems far beyond the ideas mention so far.

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#49
In reply to #48

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man Gets a New Heart

04/25/2019 6:08 PM

Computer Chips to Roof Tiles

Well, I just discovered a 2005 patent for a MEMS compression style refrigerator so apparently people are already patenting the harder job of putting a compressor in a system of super tiny volume. Despite the incredulous responses I got on this thread, I guess I am behind the curve. I was going to be satisfied with miniaturization of the much easier absorption style refrigerator.

"1. A micro-refrigerator operating on the vapor compression refrigeration cycle that is less than 10 mm×10 mm×1.5 mm in size and is fabricated using MEMS processes."

The patent leaves the compression job open to multiple means:

"9. A compressor section that is fabricated with MEMS processes allowing the piezoelectric, electromagnetic or thermal actuation to compress the refrigerant fluid to working pressure. "

And they target electronic devices for their cooling efforts and therefore presume a source of electrical power from which to run their compressor. None of this really matters except that the size is totally below the target size required to embed the system into a roof tile. This leaves the "appreciable benefit" part of your statement. I would tune this to require appreciable benefit "for the cost over the lifetime of the tile."

Anyway, they are farther along than I am and headed in the direction I want except for choosing a probably costlier mechanism (vapor compression) than I chose(absorption.) The ultimate efficiency for the cost of the two techniques is something I have been judging without benefit of quantitative information regarding the relative costs and performance of each genre of system when implemented at this scale.

So, for this thread it appears that local cooling for PV panels is something one could steal from processor/memory cooling efforts once it matures. For my cooling roof tiles, I suppose I shall just wait until they appear in my local building supply outlet and see how much they cost and how much they cool in the TX sun.

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#50
In reply to #49

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man Gets a New Heart

04/27/2019 10:46 AM

I'm sticking to my assessment. Is vapor compression vastly different than absorption in many ways, an important one of which is the area and volume of the components in relation to the capacity to move heat. Absorption requires a much larger footprint and volume for the cooling capacity.

Moreover, in the example you sited, the evaporator is minute compared to the entire chiller. The evaporator is less than 5% of the volume/area required of the refrigerator. Absorption figures would be even worse.

The problem remains about where/how to effectively reject enough heat for the heat sink to allow useful levels of power, and still only a small fractoion of the roof would be cooled. Far better would be to use the proposed tile thickness and evelopment cost for a highly reflective cool surface and insulation.

"... In this embodiment, the size of the evaporator is approximately 2 mm×2 mm×1 mm high. The evaporator cavity is provided with extended surface heat transfer fins 306 to allow the cavity to be as small as possible. A similar heat exchanger cavity is shown in FIG. 4 Section III for the condenser. Here the cavities for heat exchange 303 in top part 301 and 310 in bottom part 307 are also provided with extended surface heat transfer fins 304. The condenser cavity in this embodiment is approximately 2 mm×4 mm in plan area by about 1.5 mm high.
3 Kovacs, Gregory T. A., Micromachined Transducers Sourcebook, McGraw Hill, 1998.
[0018]
The advantage of this configuration is that it can be fabricated and assembled in wafer form using two wafers bonded together to provide a hermetic seal for the refrigerant. In the illustrated preferred embodiment, the two wafers containing many individual refrigerators are bonded together in an environment of refrigerant maintained at an appropriate pressure so that the final assemblies are hermetically sealed with the refrigerant inside.
[0019]
Interconnecting piping 308 will be etched into the wafers and the expansion orifice 105 is just a narrowed etched portion of piping 312 near the evaporator cavity 309 entrance.
[0020]
Many potential compressor technologies are available. The exact configuration chosen will depend on the particular application and could be piezoelectric, magnetic, or thermally actuated.
[0021]
Overall the size of the entire refrigerator will be less than approximately 10 mm×10 mm by 1.5 mm i...."

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#51
In reply to #50

Re: Cooling Solar Panels? Nanoscale Ammonia Absorption Refrigerator Roof Tiles ...Straw Man Gets a New Heart

04/27/2019 12:39 PM

This is why I laughed earlier. I intuitively understood the size increases.

I also want to remind people that this thread started with asking if cooling solar panels to make them more efficient is worth the effort. I still say the added energy into the cooling effort will be far larger than any photovoltaic efficiency improvement. Therefore the OP question is that this is not a good idea for the stated purpose.

It still can be a good idea. Cogeneration approaches where the "waste" heat is used in another fashion, like preheating a water heater, can make economic sense.

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#11

Re: Cooling Solar Panels?

04/21/2019 2:30 AM

Be aware that the 25°C temperature quoted on panel specifications refers to actual panel temperature - not ambient temperature.

Under normal clear sky conditions, a panel will likely be somewhere between 20 and 40 degrees hotter than that 25°C. Therefore your panel, (assuming a typical temperature coefficient or pmax of -0.45%/°C, and a Nominal Operating Cell temperature or NOCT of 45°C) will lose around 9% efficiency at a cell temperature of 40°C which is the temperature you could reasonably expect your panel to reach on a clear 25°C ambient day.

It's easy to work out the losses for your specific panel - the NOCT and pmax data is provided for most panels. The NOCT tells you the temperature rise of the panel when subjected to moderate sunlight at 20°C or basically, at an ambient of 20°C the panel temp will be 45°C, the pmax tells you the percentage of power loss for every °C rise in panel temperature above 25°C.

So a bit of math tells you that at 25°C ambient (45°-25°)x-0.45%/°C =20x0.45% = 9% loss of efficiency, at 60°C panel temperature the loss will be closer to 16%. Solar panels rarely exceed 70°C, so worst case would be a 20% loss of performance

One way to reduce cell temperature is to ensure that it always operates at, or as close to, maximum power point (MPP) as is possible.

When a Pv is operating at open circuit voltage or short circuit current it is not producing any electrical power, so all of the energy absorbed by the panel is reproduced as waste heat. That waste heat reduces as the operating parameters approach the MPP

The most effective way to keep the Pv in the maximum power "knee" is to employ a Maximum Power Point Tracking (MPPT) solar controller. These types work at better efficiency levels compared to series or PWM type controllers, but some of them are MPPT in name only and often fare not much better than the series units.

Whilst applying cooling to a panel will reduce losses, The gains will likely not be sufficient to warrant the extra cost, an alternative may be to compensate by adding more panels if you have the available real estate.

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#15
In reply to #11

Re: Cooling Solar Panels?

04/21/2019 10:54 AM

"...so all of the energy absorbed by the panel is reproduced as waste heat."

This is why solar heat (water) collectors should also be used for a good solar power program/system. It uses far more of the sun's radiation spectrum than just PV 'tron-gerating panels by themselves. Since solar water heaters are already being made, there must be some benefit for using a water-cooler to remove heat from a solar collector (as a water heater does). I've heard that some are working on PV panels that DO use more of the spectrum. It would be nice if there was a panel that used the whole spectrum (without using two different collectors for two different parts of the spectrum), so less surface area was needed to capture it all, .

In the original post, maybe he was thinking that one could add a water heater to the PV panels. That way, one could combine the functions a PV collector and a water heater to collect more of the sun's spectrum (except that a misting system could not recover the heat from the water). The thought would be that since it is worthwhile to make solar water heaters, then it might be worthwhile to use a water-cooler for the PV panel as the water-heater. That way, the water could be used for two things at the same time: 1)heat water, 2)cool the PV panels. Whether that can work or not, will depend on the temperature requirements of the two different functions. In other words, if a water heater requires the water be at a higher temp than the cooling water for the PV panels need to be, then the same water cannot perform both functions, as it cannot be at two different temperatures at the same time.

But, it is an interesting thought to make use of the whole spectrum from the sun.

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#12

Re: Cooling Solar Panels?

04/21/2019 5:51 AM

Here in Germany you can buy solar panels with water cooling on the back, that can with a heat pump, produce hot water for domestic use and heating in the winter.

The cooling effect apparently increases the output of the solar panels as well as reducing aging.

Why nobody did it before is a question?

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#16
In reply to #12

Re: Cooling Solar Panels?

04/21/2019 11:04 AM

Since solar water-heaters are already being made, it does seem like one could also recover the heat from a PV panel's cooling water. That way, that heat is not wasted, and the full sun's spectrum,s energy would be collected. Hmmm....

"...that can with a heat pump, produce hot water for domestic use and heating in the winter." You might be onto something.

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#17
In reply to #16

Re: Cooling Solar Panels?

04/21/2019 12:33 PM

Its not my idea, but it certainly made immediate sense. I did mention it some years ago here on CR4....but do not ask me when or where....!

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#13

Re: Cooling Solar Panels?

04/21/2019 6:03 AM

I can only see that the panels will stay clean to generate but cooling them I have doubts, as the mist will evaporate quicker than the cooling will take place. Maybe six of one and half a dozen of the other.

A closed cooling system of pipes laying on top of the panels may work, but then you need to keep the closed system cooler than the panel surface. Probably more hassle than it is worth.

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#14
In reply to #13

Re: Cooling Solar Panels?

04/21/2019 7:23 AM

Here they cool them from behind, but they are specially designed so.

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#20
In reply to #13

Re: Cooling Solar Panels?

04/22/2019 11:59 AM

"... as the mist will evaporate quicker than the cooling will take place. ...."

.

Hmmm. Weird. Have any links to research describing this delay of necessary latent heat of vaporization to some time after vaporization?

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#21
In reply to #20

Re: Cooling Solar Panels?

04/22/2019 12:58 PM

There are some papers on the web about this, but I wonder what will happen for people who live in a hard water area?

It would all look pretty awful after a few months maybe? Totally white?

I feel that a rear mounted cooling system, that would heat water for a house in winter and maybe a pool in summer, is by far the better option...

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#22
In reply to #20

Re: Cooling Solar Panels?

04/22/2019 1:39 PM

Make the experiment. Mist versus an outside area, and see what happens. We call it fog.

Misting is very common around restaurants to try and cool the evening air. Note, Evening air.

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#23
In reply to #22

Re: Cooling Solar Panels?

04/22/2019 7:39 PM

I am failing to see how your response relates to the evaporation occurring before the heat is removed.

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#19

Re: Cooling Solar Panels?

04/22/2019 11:48 AM

I think the idea of using the PV panels for electricity and then a water loop system to heat a swimming pool would be a great way to do it. When the sun is out, the user runs the pump to filter* and circulate the water through the solar heater. Then the electricity produced from the PV panel can offset the pump electricity.

*the pool is supposed to be filtered/circulated for a few hours a day anyway. Any cost difference would just be the additional head of the heating loop.

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#25

Re: Cooling Solar Panels?

04/23/2019 6:56 AM

So, rather than spraying water over the outside of the panel, what is objectionable about using a closed-loop treated water circuit circulating within the panel so as to provide a hot water service to the building as well as a photovoltaic generation one?

The principle is that of one rooftop panel doing both jobs.

Some design "whizz kid" needs to be working on this one...

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#26
In reply to #25

Re: Cooling Solar Panels?

04/23/2019 8:55 AM

You wrote:-

Some design "whizz kid" needs to be working on this one...

They have and it has been done, and has been on sale at least in Germany for some years, maybe further afield as well.

I did post it some years ago....but do not ask me where today!!

I have also mentioned it here on this topic recently! Did you not readall the posts before posting?

This appears to be one of the companies that I mentioned some years ago:-

https://dualsun.com/en/

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#27
In reply to #26

Re: Cooling Solar Panels?

04/23/2019 9:00 AM

The question was about what was objectionable about it and, so far, no objection has been forthcoming.

If it has been <...post[ed] some years ago...> then please report the entire thread as a duplicate.

<unsubscribes>

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#28
In reply to #27

Re: Cooling Solar Panels?

04/23/2019 9:19 AM

My only concern with running water behind a solar panel is some locations get well below freezing from time to time. So while it might be of value during the hot months, it can become a liability during the cold months.

Can this be properly designed to accommodate, of course it can. Can this be designed for disaster, yes it can.

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#29
In reply to #28

Re: Cooling Solar Panels?

04/23/2019 9:56 AM

Antifreeze.

Many different products will do the trick, though I would use that for usage in solar collectors for heat, they generally have water and something else, which is not poisonous in the case of a leak.

Even simple alcohol should work......40% Ethanol would work down to -30°C.....I suspect that Methyl Alcohol would probably be the same/similar. I don't know if this would be considered "safe" though....

The proper stuff for heating systems is very expensive here....

Maybe a thin oil would work better?

Someone here would know of better chemicals/liquids I suspect.....

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#35

Re: Cooling Solar Panels?

04/24/2019 11:55 AM

Lots of restricted comments to using water and heat transfers, How complicated! Simply seal the PV panels, port in, port out on quick couplers, flood the sealed panel with a R-410A, or R-22 or R-32 coolant and couple the PV panels to your aircon unit. They stay cool(er), the electric produced runs the AC so what hassle is required on that? No water wastage or salting of glass.

You just need to make sure you have a good sealed system. And that is easy. I am surprised no one has mentioned this as a simple fix.

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#41
In reply to #35

Re: Cooling Solar Panels?

04/24/2019 4:10 PM

"... Simply seal the PV panels, ..."

.

Please enlighten those of us who are ignorant about the simple way to seal the PV panels enroute to this simple fix.

Also, it seems like insulating the refrigerated panels would be a necessity to keep the load under any efficiency gains by the panels....that and keep condensation puddling water.

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#42
In reply to #41

Re: Cooling Solar Panels?

04/24/2019 4:34 PM

Now sir, I am no Nicola Tesla, more an Edison, so there is no sense in me telling you how to do this without me being fully compensated. We now have electric aeroplanes, electric cars, space rockets re-landing themselves and silly cars without drivers and Ai to replace humans, I can seal the panels, drain condensate and still produce a decent efficient solar panel. Trust me, there is no more rocket science these days.

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#46
In reply to #41

Re: Cooling Solar Panels?

04/24/2019 7:20 PM

Seems to me that if you're getting condensate, then you're cooling it too much. I doubt it needs that much cooling.

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#47
In reply to #46

Re: Cooling Solar Panels?

04/25/2019 2:59 AM

Nice to see someone thinking outside the box rather than some archaic "its a tried and tested method" thinking.

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