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amps from photovoltaic panel?

L

Lee Carkenord

Jan 1, 1970
0
I have been given a PV panel. Its commercially made, on a stout piece
of aluminum I-beam. Its more than 12 years old, I know that, but
don't know the actual age. Its never been put into use, spent its
whole life stored in a dark garage.

It has 36 individual cells, each cell slightly less than 2 1/8 inch
(2.125")in diameter. It appears that all 36 of them are wired in
series. In direct sun, the no-load voltage that appears at the 2
terminals is 19.90 VDC as measured with cheap digital voltmeter.

Under those conditions, what might be an approximate amperage
available?

Please give me some examples of what this panel would be capable of
running or driving.

I could drive a device that required "X" volts and "Y" current.
What might "X" and "Y" capabilities be with this panel in direct
sun?

Thank you, folks.
Lee Carkenord
 
I

Ian Stirling

Jan 1, 1970
0
Lee Carkenord said:
I have been given a PV panel. Its commercially made, on a stout piece
of aluminum I-beam. Its more than 12 years old, I know that, but
don't know the actual age. Its never been put into use, spent its
whole life stored in a dark garage.

It has 36 individual cells, each cell slightly less than 2 1/8 inch
(2.125")in diameter. It appears that all 36 of them are wired in
series. In direct sun, the no-load voltage that appears at the 2
terminals is 19.90 VDC as measured with cheap digital voltmeter.

2.125" = 5.4cm.
Call it 5cm.
That's around 19 square centimeters per.
In full sun in arizona without any coverings, you get about .13W/cm^2.
So, the amount of sunlight each gets is around 2.5W.
At 0.5V output, this will output 5A at 100% efficancy.
However, I'd be slightly surprised if it's not more like 14% efficiancy,
or .7A.

Probably more like 0.5A, for a total of around 9 watts at 18V.

--
http://inquisitor.i.am/ | mailto:[email protected] | Ian Stirling.
---------------------------+-------------------------+--------------------------
"Melchett : Unhappily Blackadder, the Lord High Executioner is dead
Blackadder : Oh woe! Murdered of course.
Melchett : No, oddly enough no. They usually are but this one just got
careless one night and signed his name on the wrong dotted line.
They came for him while he slept." - Blackadder II
 
D

Dana Raymond

Jan 1, 1970
0
I don't know if this is already understood...

Don't shine a light and measure the voltage with the DVM and then measure
the current with the DVM's ammeter, and then report the panel or cell as VxA
watts! A friend once got bit buying surplus cells once and that was the
technique used at the store to rate them!

Dana Frank Raymond
 
R

Rheilly Phoull

Jan 1, 1970
0
Could you re-word this ??
"Don't shine a light" how would there be any output ??
In any case such things are made to work in full sunlight.
I can't understand what you are saying.
 
N

N. Thornton

Jan 1, 1970
0
Dana Raymond said:
I don't know if this is already understood...

Don't shine a light and measure the voltage with the DVM and then measure
the current with the DVM's ammeter, and then report the panel or cell as VxA
watts! A friend once got bit buying surplus cells once and that was the
technique used at the store to rate them!

Dana Frank Raymond


Right, though thats not legal, at least in UK. The panel will never
put V_oc and i_short at the same time, so the wattage would be bogus.
Trades descriptions Act.

Regards, NT
 
S

Sir Charles W. Shults III

Jan 1, 1970
0
You cannot get an accurate reading of the output voltage unless the panel is
under a load. Load the panel in full sunlight until it reads 12 volts (or 13.8
in the case of a panel used as a charger) and then read the amps being supplied
under the load.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
 
N

N. Thornton

Jan 1, 1970
0
I believe this is how some appliances are rated here in the US. Power
Rating = Motor Stall Torque * No Load RPM = nothing based in reality. My
"5.0 HP" shop-vac runs off a 15A 115V outlet. I'm guessing we don't have an
equivalent law here to prevent this type of deceit.

Chris


Well FWIW our laws dont prevent it either, but they do reduce it a
lot. Its about time someone selling 'PMPO' rated stuff got prosecuted
under this act.

Regards, NT
 
D

Don Lancaster

Jan 1, 1970
0
Rheilly said:
Could you re-word this ??
"Don't shine a light" how would there be any output ??
In any case such things are made to work in full sunlight.
I can't understand what you are saying.

The output power of a pv panel when short circuited is zero.
The output power of a pv panel when open circuited is zero.

ONE HALF the open circuit voltage times ONE HALF the short circuit
current will roughly get you in the ballpark. Or ONE QUARTER their
product.

You only approach this performance when the load is carefully and
properly matched.
The matched load must, of course, increase or decrease with sun angle
and strength.


--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: [email protected] fax 847-574-1462

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
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