Cooling off PV panels?? - Page 2

Patrick · 09-03-10, 08:02 AM

How about some aluminum flashing bent into L shapes, then "glued" to the back of the panels with silicone sealer? According to one DIY site, the silicone works fine as a heat transfer agent. I'd orient the L shapes vertically along the back of the panels so that convection will carry the heated air up and out. I think if you try to use fans that they will probably consume more energy than the lower temp will provide - a net loser, but I could be wrong. :-)

Xringer · 09-03-10, 08:21 AM

That sounds like a good idea. I could glue strips on and duct tape them down until the glue cured..

I would angle them outwards about 30 degrees, so the hot air would be directed up and also towards the sides.
Sorta like this tire pattern:

That might keep the top panels from being heated by the air flowing up from the bottom in 'channels'.

I know that flashing is more cost effective, I just wonder if the metal is too thin?
Most heat sinks that I've seen are pretty sturdy..
But, now that I think about the coils in your typical AC or HP, flashing might be pretty good!

Thanks for getting me thinking about this again..

I may have to take a look at these:
Shop Amerimax 2-1/2" x 21/2" x 7"' Aluminum Prebent Shingle Flashing at Lowes.com

Pre-formed! Get 144 (1-per-cell) for about $30..

Xringer · 10-18-10, 10:02 AM

Now the weather is getting cooler, I'm seeing 7 amps just about every morning.
Figuring in the cable loss, the panels are providing their full rating of 500w..
Sometimes 3 or 4 more watts..

So, cooling fins on the backsides of the panels is on my list for next summer..
If I can pick up 15 or 20 watts for $30 of aluminum, it would be worth it.
~~~
Of course, if I could buy a 10w panel for $30 and somehow make it contribute 10watts to the array..?..

Solar Mike · 10-19-10, 07:45 PM

I have 20 180 watt panels to install on a ground mounted fixed frame outside my house, seems cooling them in the heat of summer will be very beneficial.

What I'm thinking of doing is getting 20 sheets of alloy cut that will fit against the backing of each panel, stick each of these to the pv panel with a thick bead of silicon so there is gap of 3-4 mm between the two, sealed around the edges. Run cooling water via an In and Out push fit nozzle and circulated with a small magnetic drive pump, join them together with 10mm push on rubber tube.
The circulating water can come from a large tank or spa pool. At most the water pressure on the panels will be 1.5 meters head, so should have little effect on its structure.
This arrangement will cool the panels more efficiently than using air and has the added benefit of doing something with the warmed water.
The back of the panels seem quite resistant to water, the stick on alloy sheets would be best anodized to prevent corrosion.

Perhaps best tried on 1 panel for a period first.

Cheers
Mike

Xringer · 10-19-10, 08:07 PM

I would be worried about the junction boxes on my panels.. They are probably water resistant, but not really water proof..

How is your water supply there? If it's not restricted, there might be
easier ways to cool those panels..

And, you could grow some vegetables at the same time..

gasstingy · 10-22-10, 07:33 AM

On my 700w array (Sharp 175 monochrystaline x 4, Enphase inverters), my best observed hot weather ready was 652 watts @ ~ 95 degrees f. My best observed cold weather performance was 712 watts @ ~ 26 degrees f.

By my imprecise calculations, it went from 93% efficient to 101.7% efficient

including all losses into the house. I've no idea how much difference a fan system would improve their performace on a really hot day, but at least the cold weather performance helps make up for the fewer hours of daylight in the winter.

pachai · 10-29-10, 09:33 AM

bs"d

I like this discussion.

I am about to have an addition put on my house,
with roof space for about 500KW.
I was thinking of having a pump circulate
water to the front of the panel, with a gutter
for recovering the water.
Not sure how much water flow I would need.

Maybe a 12 V pump like I bought for the electric
car I am trying to build. The controller needs to be
water cooled. It could run off a small panel.

(Flash!) The old radiator from my car - maybe I could
flush it out and use that for the solar panels' radiator.
An EV does not need such a big radiator.

I am a bit worried about cooling it so fast that
it cracks....but then again, if the pump comes on
at 70 degrees, the panel will never get to be
terribly hot.

Seth

Xringer · 10-29-10, 01:35 PM

If you install a 500KW array, you will be able to make as much power
in one hour, as I use in one month.. 500KWh costs me about $100..

pachai · 10-29-10, 01:46 PM

>>>If you install a 500KW array, you will be able to make as much
>>> power in one hour, as I use in one month.. 500KWh costs me
>>>about $100..

Right, that old decimal point thing.
It's a 5 KW array... :-)

Thanks

Xringer · 10-29-10, 02:10 PM

5kw is still a monster array (compared to my 500w hobby array).
If I had an array that big, I wouldn't be trying to squeeze out the last watt.
But I would be selling power back to the grid.

To cool off a 5kw PV array would be a big project..

You might want to look into the SunDrum PV/Water type panels..

Products

09-03-10, 08:21 AM	#12
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	That sounds like a good idea. I could glue strips on and duct tape them down until the glue cured.. I would angle them outwards about 30 degrees, so the hot air would be directed up and also towards the sides. Sorta like this tire pattern: That might keep the top panels from being heated by the air flowing up from the bottom in 'channels'. I know that flashing is more cost effective, I just wonder if the metal is too thin? Most heat sinks that I've seen are pretty sturdy.. But, now that I think about the coils in your typical AC or HP, flashing might be pretty good! Thanks for getting me thinking about this again.. I may have to take a look at these: Shop Amerimax 2-1/2" x 21/2" x 7"' Aluminum Prebent Shingle Flashing at Lowes.com Pre-formed! Get 144 (1-per-cell) for about $30.. Last edited by Xringer; 09-03-10 at 08:31 AM..

10-19-10, 08:07 PM	#15
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	That would make them super efficient I would be worried about the junction boxes on my panels.. They are probably water resistant, but not really water proof.. How is your water supply there? If it's not restricted, there might be easier ways to cool those panels.. And, you could grow some vegetables at the same time..

10-29-10, 09:33 AM	#17
pachai Renovator-in-planning Join Date: Oct 2010 Location: Northern NJ Posts: 85 Thanks: 6 Thanked 0 Times in 0 Posts	Cooling PV panels bs"d I like this discussion. I am about to have an addition put on my house, with roof space for about 500KW. I was thinking of having a pump circulate water to the front of the panel, with a gutter for recovering the water. Not sure how much water flow I would need. Maybe a 12 V pump like I bought for the electric car I am trying to build. The controller needs to be water cooled. It could run off a small panel. (Flash!) The old radiator from my car - maybe I could flush it out and use that for the solar panels' radiator. An EV does not need such a big radiator. I am a bit worried about cooling it so fast that it cracks....but then again, if the pump comes on at 70 degrees, the panel will never get to be terribly hot. Seth

09-03-10, 08:02 AM	#11
Patrick Apprentice EcoRenovator Join Date: Jul 2010 Location: East Coast of Florida, USA Posts: 149 Thanks: 2 Thanked 5 Times in 5 Posts	How about some aluminum flashing bent into L shapes, then "glued" to the back of the panels with silicone sealer? According to one DIY site, the silicone works fine as a heat transfer agent. I'd orient the L shapes vertically along the back of the panels so that convection will carry the heated air up and out. I think if you try to use fans that they will probably consume more energy than the lower temp will provide - a net loser, but I could be wrong. :-)

10-18-10, 10:02 AM	#13
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Now the weather is getting cooler, I'm seeing 7 amps just about every morning. Figuring in the cable loss, the panels are providing their full rating of 500w.. Sometimes 3 or 4 more watts.. So, cooling fins on the backsides of the panels is on my list for next summer.. If I can pick up 15 or 20 watts for $30 of aluminum, it would be worth it. ~~~ Of course, if I could buy a 10w panel for $30 and somehow make it contribute 10watts to the array..?..

10-19-10, 07:45 PM	#14
Solar Mike Helper EcoRenovator Join Date: Apr 2010 Location: Wellington, New Zealand Posts: 61 Thanks: 0 Thanked 6 Times in 5 Posts	I have 20 180 watt panels to install on a ground mounted fixed frame outside my house, seems cooling them in the heat of summer will be very beneficial. What I'm thinking of doing is getting 20 sheets of alloy cut that will fit against the backing of each panel, stick each of these to the pv panel with a thick bead of silicon so there is gap of 3-4 mm between the two, sealed around the edges. Run cooling water via an In and Out push fit nozzle and circulated with a small magnetic drive pump, join them together with 10mm push on rubber tube. The circulating water can come from a large tank or spa pool. At most the water pressure on the panels will be 1.5 meters head, so should have little effect on its structure. This arrangement will cool the panels more efficiently than using air and has the added benefit of doing something with the warmed water. The back of the panels seem quite resistant to water, the stick on alloy sheets would be best anodized to prevent corrosion. Perhaps best tried on 1 panel for a period first. Cheers Mike

10-22-10, 07:33 AM	#16
gasstingy Journeyman EcoRenovator Join Date: Feb 2010 Location: Arab, AL Posts: 491 Thanks: 109 Thanked 49 Times in 43 Posts	On my 700w array (Sharp 175 monochrystaline x 4, Enphase inverters), my best observed hot weather ready was 652 watts @ ~ 95 degrees f. My best observed cold weather performance was 712 watts @ ~ 26 degrees f. By my imprecise calculations, it went from 93% efficient to 101.7% efficient including all losses into the house. I've no idea how much difference a fan system would improve their performace on a really hot day, but at least the cold weather performance helps make up for the fewer hours of daylight in the winter.

10-29-10, 01:35 PM	#18
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	If you install a 500KW array, you will be able to make as much power in one hour, as I use in one month.. 500KWh costs me about $100..

10-29-10, 01:46 PM	#19
pachai Renovator-in-planning Join Date: Oct 2010 Location: Northern NJ Posts: 85 Thanks: 6 Thanked 0 Times in 0 Posts	>>>If you install a 500KW array, you will be able to make as much >>> power in one hour, as I use in one month.. 500KWh costs me >>>about $100.. Right, that old decimal point thing. It's a 5 KW array... :-) Thanks

10-29-10, 02:10 PM	#20
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	5kw is still a monster array (compared to my 500w hobby array). If I had an array that big, I wouldn't be trying to squeeze out the last watt. But I would be selling power back to the grid. To cool off a 5kw PV array would be a big project.. You might want to look into the SunDrum PV/Water type panels.. Products