Can solar panels be safely short-circuited?

[Pimpom]

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.

 

[Pimpom]

Pimpom wrote:

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no
particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.

I mean safe for the panel. Please disregard consideration of
external circuits.

 

[Tom Biasi]

On 12/19/2012 1:47 AM, Pimpom wrote:

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.


Usually not a problem. Most panels run close to their short circuit

current capability.

 

[John Larkin]

On Wed, 19 Dec 2012 12:17:55 +0530, "Pimpom" <Pimpom@invalid.invalid> wrote:

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.

They can't get any hotter than a sheet of black stuff.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
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Multichannel arbitrary waveform generators

 

[George Herold]

On Dec 19, 1:47 am, "Pimpom" <Pim...@invalid.invalid> wrote:

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.

I use photodiodes 'short circuited' (into a TIA opamp circuit). It
doesn't seem like short circuiting a solar panel could hurt it. (But
I've never used one!) It might be useful as the short circuit current
would be some measure of the total intensity. Are the panels all just
single 'diode drops' or do they sometimes put a few in series?

George H.

 

[Pimpom]

Tom Biasi wrote:

On 12/19/2012 1:47 AM, Pimpom wrote:
Can solar panels be safely short-circuited while they are
fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no
particular
design or application in mind where short-circuiting the
output
plays a role - just that it might be useful to know.


Usually not a problem. Most panels run close to their short
circuit
current capability.

Thanks.

 

[Pimpom]

John Larkin wrote:

On Wed, 19 Dec 2012 12:17:55 +0530, "Pimpom"
Pimpom@invalid.invalid
wrote:

Can solar panels be safely short-circuited while they are
fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no
particular
design or application in mind where short-circuiting the
output
plays a role - just that it might be useful to know.


They can't get any hotter than a sheet of black stuff.

I didn't get that right away but let's see (basic college
thermodynamics is >40 years in the past). The panel receives
solar radiation, much (most?) of which is thermal and the black
panel is efficient at absorbing it. So the panel gets heated up
quite a bit. But some of the radiant energy is converted to an
electrical potential. If that electrical potential is
short-circuited, there's no change in the power expended in the
cells, and therefore no additional heat produced. Is that the
logic?

But then not all the radiation is thermal and the non-thermal
part is also converted to electricity. Wouldn't that produce
additional heat if it's short-circuited?

 

[Pimpom]

George Herold wrote:

On Dec 19, 1:47 am, "Pimpom" <Pim...@invalid.invalid> wrote:
Can solar panels be safely short-circuited while they are
fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no
particular
design or application in mind where short-circuiting the
output
plays a role - just that it might be useful to know.

I use photodiodes 'short circuited' (into a TIA opamp circuit).
It
doesn't seem like short circuiting a solar panel could hurt it.
(But
I've never used one!) It might be useful as the short circuit
current
would be some measure of the total intensity. Are the panels
all just
single 'diode drops' or do they sometimes put a few in series?

George H.

I have one panel as a sample and it has 39 cells in series.
Judging from the size, I'd guess the power rating as somewhere
around 50W. Its open circuit voltage in bright sunlight is about
23V. I haven't tested it yet to plot its characteristics under
different levels of load and sunlight. No datasheet, and the
company has only a rudimentary website.

Someone gave me the sample to play with and see if I could turn
it into something useful. It seems they have truckloads of the
things but they don't know what to do with them. I didn't bother
asking why they bought them in the first place. Probably with
some vague idea of using them as backup power.

 

[Jasen Betts]

On 2012-12-19, Pimpom <Pimpom@invalid.invalid> wrote:

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.

If you short circuit them they will heat up, there will be the
same amount of heating as if you leave them open circuit and
unloaded, just via a slightly different mechanism.

--
⚂⚃ 100% natural

 

[George Herold]

On Dec 20, 1:07 am, "Pimpom" <Pim...@invalid.invalid> wrote:

John Larkin wrote:
On Wed, 19 Dec 2012 12:17:55 +0530, "Pimpom"
Pim...@invalid.invalid
wrote:

Can solar panels be safely short-circuited while they are
fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no
particular
design or application in mind where short-circuiting the
output
plays a role - just that it might be useful to know.

They can't get any hotter than a sheet of black stuff.

I didn't get that right away but let's see (basic college
thermodynamics is >40 years in the past). The panel receives
solar radiation, much (most?) of which is thermal and the black
panel is efficient at absorbing it. So the panel gets heated up
quite a bit. But some of the radiant energy is converted to an
electrical potential. If that electrical potential is
short-circuited, there's no change in the power expended in the
cells, and therefore no additional heat produced. Is that the
logic?


But then not all the radiation is thermal and the non-thermal
part is also converted to electricity. Wouldn't that produce
additional heat if it's short-circuited?

That seems right. The energy has to go somewhere.
But when the cell is open circuited there's no energy 'lost' from the
cell either. The photo-generated e-h pairs recombind in the silicon.
So the cell runs at it's coolist when you are pulling just the right
amount of energy out of it.

George H.

- Hide quoted text -

- Show quoted text -

 

[George Herold]

On Dec 20, 5:24 am, Jasen Betts <ja...@xnet.co.nz> wrote:

On 2012-12-19, Pimpom <Pim...@invalid.invalid> wrote:

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.

If you short circuit them they will heat up, there will be the
same amount of heating as if you leave them open circuit and
unloaded, just via a slightly different mechanism.

Right!... sorry I should have read to the end of the thread before

posting.

(Can you see the temperature rise 'in practice', as opposed to 'in
theory'?)

George H.

--
⚂⚃ 100% natural

 

[Jasen Betts]

On 2012-12-20, George Herold <gherold@teachspin.com> wrote:

(Can you see the temperature rise 'in practice', as opposed to 'in
theory'?)

It was an issue for the builders of the sunshark
http://en.wikipedia.org/wiki/Sunshark_Solar_Car_Team
I had a chat with them around 1991 some time.

In their design the silicon wafers are beneith a layer
of fibreglass abd the overheating was causing delamination.

--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Bret Cahill]

Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the
concept of MPP, conversion efficiency, etc. I have no particular
design or application in mind where short-circuiting the output
plays a role - just that it might be useful to know.

Not as much hotter as they would get cooler in the shade w/o a short.


Bret Cahill

 

[Tim Wescott]

On Thu, 20 Dec 2012 10:24:28 +0000, Jasen Betts wrote:

On 2012-12-19, Pimpom <Pimpom@invalid.invalid> wrote:
Can solar panels be safely short-circuited while they are fully
illuminated? I've looked at the specs and I understand the concept of
MPP, conversion efficiency, etc. I have no particular design or
application in mind where short-circuiting the output plays a role -
just that it might be useful to know.

If you short circuit them they will heat up, there will be the same
amount of heating as if you leave them open circuit and unloaded, just
via a slightly different mechanism.

Except that when they're short circuited the heating may be concentrated
in some wire or another and burn it up.

I hadn't chimed in to this thread yet because I suspect that the short-
circuit current is close enough to the optimal current that unless the
panel is really poorly designed it'll do just fine. But I don't KNOW.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com