your thoughts on cooling panels?

al128

We all know that hot panels bring the voltage down, dont we ...

given the rather high prices of panels, has anybody thought of retrofitting some kind of heat sink to the back of the panels?

I was thinking about "thermal glueing" some alu "U" channels to the back of the panel, thus offering some more surface to radiate heat off.

not exactly rocket-surgery ... and should not be too expensive, either ...


-> to be honest, the marketeer in me doesnt understand why no brand offers stock panels with some kind of heat sink ... this feature should easily be worth some bucks for the general shopper (if cleverly marketed), especially in a market where all panels are "the same"


thoughts?

as always - thx for your time and effort,
al

niel

Re: your thoughts on cooling panels?

this has been hashed on in past posts, but i think you're the first to just propose only a heatsink type arrangement. don't quote me though. the problem is that heat normally wants to rise and the sink is on the bottom side of the pv. the sink may draw this heat to it, but it will want to go back up into the pv unless there's something to take it away like a fan or running water. this negates any gains at this point because of the power needed to push either the air or the water to carry off the heat. if you experiment and find a possible solution then by all means let us in on it.

BB.

Re: your thoughts on cooling panels?

Probably not worth the added material, weight, and costs.

Best bet is to mount the panels something like 6" or more off of the roof if you are in a hot climate.

I tried the old hose cooling with tap water experiment on a hot day--I could not really see any appreciable difference in output--I am sure it is real, but cooling the cells on a normal panel is probably not easy. Glass itself is a poor thermal conductor, and most of the panels seem to have a plastic composite backing which would also be a poor thermal conductor.

What people have done is experiment with lenses and tracking solar panels--They have done up to about 10x solar radiation--and those cells are mounted to metal blocks with heat sinking (fins or circulating coolant?) to keep what are otherwise more or less normal silicon cells from cooking with all of that light/heat. There are some solar panel systems out there for sale that have lens/concentrator systems--but they do not seem to be mainstream yet (price per watt too high? And I would have questions about long term reliability).

-Bill

al128

Re: your thoughts on cooling panels?

niel wrote: »

this has been hashed on in past posts, but i think you're the first to just propose only a heatsink type arrangement. don't quote me though. the problem is that heat normally wants to rise and the sink is on the bottom side of the pv. the sink may draw this heat to it, but it will want to go back up into the pv unless there's something to take it away like a fan or running water. this negates any gains at this point because of the power needed to push either the air or the water to carry off the heat. if you experiment and find a possible solution then by all means let us in on it.

well, taking into account that we mostly place our panels at ~45° like we do... sould take care of floating the heat away

let me see if I can come up with measures while I still have the panels sitting in the yard.

cheers
al

System2

Re: your thoughts on cooling panels?

I think it is a fine experimental idea. Let us know.

BB.

Re: your thoughts on cooling panels?

There is a thread here (can't find it so far) where you can buy a solar PV panel that has an insulated rear thermal heat exchanger so that you can collect electricity and hot water from the same panel.

-Bill

icarus

Re: your thoughts on cooling panels?

The idea of thermo-siphon water cooling with the water going to domestic hot water is a cool idea, but doesn't seem feasable. I would be concerned about thermal shock of very cold water on hot panels. On the other hand, the withstand sudden rain shower/hail events. Hmmm, gotta think a bit more.

T

niel

Re: your thoughts on cooling panels?

al128 wrote: »

well, taking into account that we mostly place our panels at ~45° like we do... sould take care of floating the heat away

let me see if I can come up with measures while I still have the panels sitting in the yard.

cheers
al

yes, the angle may help in getting rid of some of that heat as well as leaving a larger space between the pvs and the roof could help. i encourage you to try and let us know the outcomes. do you have an ir thermometer as it may make your measurements easier? try to mimic the same conditions the pv will encounter on the roof and on the roof may be the best way to do that. if only testing 1 pv up on the roof then what effect would the rest of the pvs have when placed around it too?

Telco

Re: your thoughts on cooling panels?

icarus wrote: »

The idea of thermo-siphon water cooling with the water going to domestic hot water is a cool idea, but doesn't seem feasable. I would be concerned about thermal shock of very cold water on hot panels. On the other hand, the withstand sudden rain shower/hail events. Hmmm, gotta think a bit more.

T

I actually DIDN'T like the idea behind this. Heating the water means the water will be cycled through over and over until it reaches the set temperature, so you will potentially have 130 degree water being pumped under the panel, as opposed to 100 degree air under it. Seems to me like this would cause the panel to run hotter towards the hottest part of the day than it otherwise would. The only way I see this as being a benefit is if the water were going to a huge load bank like a swimming pool, where you could count on having water that is cooler than ambient air temps throughout the day. With a swimming pool cooling the water that goes in the panel (you'd want a radiator with pure water for the loop, not chlorinated water, being pumped around the panel) I could see a benefit but for DHW seems like the heated water coming in would be a detriment.

icarus

Re: your thoughts on cooling panels?

Telco,

Your probably right. A swimming pool would make better sense by far. I also think the infrastucture of building such a thin would out weigh it's benefits. My guess if it were that easy for net gain Keocera, or Evergreeen of someone would be doing it.

The solution is live in the north (or south for that matter!) where the winter temp is -35. Or just run your panels at night! Solar n the Antarctic works great for several months a year!

T

niel

Re: your thoughts on cooling panels?

icarus wrote: »

Telco,

Your probably right. A swimming pool would make better sense by far. I also think the infrastucture of building such a thin would out weigh it's benefits. My guess if it were that easy for net gain Keocera, or Evergreeen of someone would be doing it.

The solution is live in the north where the winter temp is -35. Or just run you panels at night!

T

gee, do you get much production at night?:roll::p

Telco

Re: your thoughts on cooling panels?

Must live next to a street lamp. :cool:

icarus

Re: your thoughts on cooling panels?

No, I got the new Starlite edition of Moonbeams new line. See the website
WW.dreamon.com. LOL (oops, that is a real url,,guess I have to change it!)

Tony

al128

Re: your thoughts on cooling panels?

niel wrote: »

yes, the angle may help in getting rid of some of that heat as well as leaving a larger space between the pvs and the roof could help. i encourage you to try and let us know the outcomes. do you have an ir thermometer as it may make your measurements easier? try to mimic the same conditions the pv will encounter on the roof and on the roof may be the best way to do that. if only testing 1 pv up on the roof then what effect would the rest of the pvs have when placed around it too?

I guess we all will have to wait a couple of months ... after a traffic accident in feb. I still need crutches to walk ... ;-/

- trust me - you dont want to see me up a roof ;-)))

let me see what I can do on level ground ... any thoughts about the adhesive? ... would need a thermally conductive one, ... something like they use to glue heatsinks on computer parts.

cheers
al

Solar Guppy

Re: your thoughts on cooling panels?

Unless your planning on cooling ALL the cells, you won't even be able to measure the difference.

Any heatsink that is the size of a typical 2'x4' panel will cost MORE than the panel itself, go price alumimum heatsinks, they are very pricy.

Only voltage is effected by heat, current actually increase with heat, but only 1/10th the increase compared to a voltage drop.

In typical conditions, at best you might get a 20C reduction in cell tempature, for a 100 watt panel, that 10% voltage decrease or 10 watts. At 4 dollars a watt, your looking at a value of 40 dollars ... you can't even get 1 foot of finned heatsink for that. You also HAVE to have air movement, otherwise its just a larger thermal mass and no improvement. FYI, My pool pump needs 1500 watts/hour to pump the solar thermal collectors which is an area of about 5kw of panels .. so 25% energy to save 10%

Pool water would work, but it would cost more than 40 dollars to have a water tight seal, not to mention the energy having to PUMP that water around. Domestic is a no-no, your looking at 50C+ tempatures.

The reason its not done as it doesn't make financial sense and that was BEFORE prices for materials have doubled in the last 2-3 years

niel

Re: your thoughts on cooling panels?

"let me see what I can do on level ground ... any thoughts about the adhesive? ... would need a thermally conductive one, ... something like they use to glue heatsinks on computer parts."

be advised that is not adhesive. when having metal to metal you can't get it to contact 100% everywhere so the very small gaps that are left windup being insulative rather than conductive. allowing thermal silicon grease to fill in those gaps allows the thermal conduction that was missing due to the irregularities in the metals. it's not as good as metal to metal in its conduction of heat, but is far better than tiny air gaps that insulate. some other means is usually present to keep the 2 seperate parts pressed together.