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Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 1578

Posted: 02:33pm 21 Jun 2023

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Something came up on another page that got me thinking but I can't find an answer searching google.

If I removed the diodes from a solar panel and bridged the connections and then fed power INTO the panel, would it become a heating panel?

If so, would it create the say, 300w of thermal energy if that's what the panel was rated to in normal use or less or potentially more?

I have some uses for panels as heaters if this would work and could be very convenient!

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2134

Posted: 11:07pm 21 Jun 2023

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An interesting idea. From a thermal perspective input could go way over the normal output. In normal use if a panel is 20% efficient the other 80% of the solar input is turned to heat, so I guess they could take 4 times as much. However how much current the cells can handle I don't know.

Current regulation may be needed as the cells are forward biased diodes with a negative temp. coefficient. A constant voltage supply could result in thermal runaway.

If the cells are in a single series string it should work with a single current regulator. If there are multiple strings each may need its own regulator.

Davo99
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Joined: 03/06/2019
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Posted: 10:29am 25 Jun 2023

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I was thinking much the same thing with the input conversion. If they are only 20% effective at converting light, should they not be 80% efficient at converting power to heat?

Someone must have thought of this before but I can't find anything on the net, probably because I'm not using the right words in searches.

Solar Mike
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Joined: 08/02/2015
Location: New Zealand
Posts: 1138

Posted: 08:42pm 25 Jun 2023

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I imagine a large PV panel 180-300W would make an excellent flat infrared heater. You would have to remove the bypass diodes and power it from a constant current driver power source of a higher voltage than the panel like a couple of outside PV panels in series.

Paint the rear of the panel silver or leave white and the glass side satin black with a spirit based paint so it will stick. Bolt it to a wall or suspend from the ceiling with the black side outwards.

The max input current will be limited by the size of the small inter cell connection wires, so I wouldn't go much above the panels short circuit current rating stamped on the back.

Would be an interesting experiment.

Cheers
Mike

mab1
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Joined: 10/02/2015
Location: United Kingdom
Posts: 209

Posted: 07:27pm 27 Jun 2023

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I'll be interested to see how you get on with this. If my understanding is correct if you push current through the panel in the normal directon (i.e. positive current coming out of the panels positive lead same as when it's generating power) then that's forward biasing the cells so presumably if you go up to the normal panel current you would end up with something like the voc drop across the panel (0.6-0.7v per cell)?

If you try pushing the current the other way they presumably don't conduct until you reach the zenner voltage, which would give you a higher voltage, and so a higher power per amp, but I've no idea what the zenner voltage would be.

Definitely need to remove the bypass diodes though.

Of course you would need to keep the cells below the max temp for silicon diodes though or they'll go short circuit.
Edited 2023-06-28 05:30 by mab1

Davo99
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Posted: 01:05pm 28 Jun 2023

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I'm thinking when I get to this I'll start with 2 Panels into one and then go to 3 and see what happens.

After that's it's probably non viable to put that much heat in to get what I perceive will be much less out.

Surprised there does not seem to be documentation of anyone doing this I can find and people haven't heard of it.

zeitfest
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Joined: 31/07/2019
Location: Australia
Posts: 482

Posted: 12:10am 19 Jul 2023

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Good idea, I wonder if they can be pushed into acting as large IR emitting LED's ?
that'd be good as a IR heater - hopefully better than the standard crummy bar radiator.

orangezero
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Joined: 12/04/2024
Location: United States
Posts: 2

Posted: 02:17am 04 Jul 2024

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https://groups.google.com/g/electrodacus/c/ncACW0N63Sk/m/cpWWR9F4AAAJ

Here are some photos of someone who has done it in him home. He certainly does the math and limits the amps going through so that the solar panel doesn't get any warmer than it would on a typical summer day in the heat.

I had wondered at one point about finding some really inexpensive old panels and adding them under my floorboards (ceiling of my basement), then insulating under them so the resulting heat would mostly go up into my first level floor, thus heating my house. It would be difficult to find a less expensive 1m x 1.3m surface that is already covered in glass. I don't think the temperatures work out quite right, as it would end up being a little too hot for my wood floor.

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