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Quick Solar no-load question.
By Psycogeek, Section Solar Posted on Wed Apr 19, 2006 at 07:03:42 AM MST
Will a load help heat on the cells.

Hi, you guys helped me to create my first solar pannel. that now runs the LED lighting in the kitchen non-stop now for years.
i also have other solar things that i am running, and i have a quick question, that i will eventually come back for the answer.
I have one backpack solar pannel that is low voltage high power, and its epoxy covered. it is only that pannel that i ask this question.
if there is no load, no battery to charge, and the solar cells are recieving full sun power, and the juice is just going nowhere. does the solar cell heat up more?
WHY
because the epoxy on it was making popping sounds, so i need to know if it was just normal heat and expansion contraction, or if i am going to hurt it more by no-load.

Quick Solar no-load question. | 4 comments (4 topical)

Re: Quick Solar no-load question. (3.00 / 0) (#1)
by ghurd on Wed Apr 19, 2006 at 01:20:41 AM MST

The panel should have some cooling air flowing behind, if it is in a place where it can get very hot. Do not place a panel flat and tight on a black shingle roof.
Make sure the retaining fasteners are not too tight.

No Load conditions should not have much effect on a good PV.

Never heard of this before. Please let us know what it is!
G-
Ghurd.info

Re: Quick Solar no-load question. (3.00 / 0) (#2)
by richhagen on Wed Apr 19, 2006 at 10:04:05 AM MST

In theory, there would be the same amount of energy bombarding the panel, if you are not taking part of it as electrical output, it has to go somewhere. It strikes me that some, or most of it would likely turn up as heat. Even the most efficient solar cells do no better than about 20% efficiency however, so there isn't going to be an order of magnitude of difference or anything. If you have thermal issues with the unloaded panel, they will probably still exist when the panel is loaded. Rich
'A Joule saved is a Joule made'

Re: Quick Solar no-load question. (3.00 / 0) (#3)
by iFred on Wed Apr 19, 2006 at 11:27:47 AM MST

panels normally should be installed with air gap behind to allow cool air to flow through the back of the panel. heat reduces output of any solar panel, as the cells get hotter the output is reduced. thus it is best to keep them cool. not connecting them to anything does nothing to the temprature. shorting the panel out electrically would produce heat by the amount of the electrical rating listed on the panel plus the resistance of the internal cells, the energy has to go somewhere and that somewhere is a PN junction which will act as a heater. the is how those small box thermo beer coolers work. thus open circuit panels will do nothing. Good Luck!

>> all energy used to produce this comment or post came from solar and wind energy! It works!

Re: Quick Solar no-load question. (3.00 / 0) (#4)
by Ungrounded Lightning Rod on Wed Apr 19, 2006 at 05:07:37 PM MST

not connecting them to anything does nothing to the temprature. shorting the panel out electrically would produce heat by the amount of the electrical rating listed on the panel plus the resistance of the internal cells,

Beg to differ:

Once a photon is absorbed, creating an electron-hole pair, some of the photon's energy is changed to the energy represented by the separation of the electron and hole, and the rest went into heating the panel.

Now what do you do with the electron-hole pair:

- You can do nothing: It recombines, emitting infrared (which is absorbed and becomes heat in the panel)
- You can use it to drive an electron through the wiring: Some of the energy goes into the load, some in to the panel resistance, and some into the electron-hole anihalation when a returning electron falls into the hole (across a much lower energy gap).

The difference in panel heating is the energy that was delivered to the load and the wiring beyond the panel.

So disconnecting the load means that 20% or less of your incoming solar energy that WOULD have been delivered to the off-panel load is now delivered to the panel.

So the panel is heated significantly, but not greatly, more WITHOUT the external load. (And the heating of the wiring internal to the panel comes from energy that, without the current, would have been heat in the panel anyhow.)

[ Parent ]

Quick Solar no-load question. | 4 comments (4 topical)

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