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Posted by Ron Rosenfeld on July 13, 2008, 10:38 pm
 
On Sat, 12 Jul 2008 17:21:56 -0700 (PDT), bealiba@gmail.com wrote:


No, I was not aware of a test standard that specified a particular voltage
for the PV cell.

What standard is that?



The standards I've seen with regard to PV panels are STC and PTC.

But they both refer to wattage ratings under specified conditions of
irradiance, temperature and, for the PTC standard, wind speed.  Neither one
mentions a particular voltage.

NOCT is not mentioned in either of those standards, and the irradiance used
to determine NOCT is not the same as that used in either STC or PTC
standards.
--ron

Posted by bealiba on July 13, 2008, 11:02 pm
 


Posted by Ron Rosenfeld on July 14, 2008, 8:38 pm
 On Sun, 13 Jul 2008 16:02:23 -0700 (PDT), bealiba@gmail.com wrote:


Yes it is sad that you obviously have no idea of the meaning of STC, PTC or
NOCT.
--ron

Posted by bealiba on July 15, 2008, 12:51 pm
 
Time to look at Tweedledee's claims about;

1) STC - DC watts-The nameplate rating of a solar module.

2) PTC - DC watts-the rating of a module in real-world conditions as
determined by the California Energy Commission.

PTC it seems is not used anywhere other than California to determine
the rebate paid for solar power installations.

Tweedledee left this part of the information out - CEC AC watts - the
total PTC DC of solar modules factoring in inverter efficiency. This
the number that the rebate is based on. This rebate is generally for
"Grid Connect" systems. Not stand alone systems.

But,

Notice where it says "the total PTC DC of solar modules factoring in
inverter efficiency." it looks suspiciously like "A5 & C10" in the
formula, and "STC DC watts-The nameplate rating of a solar module"
bears a striking resemblance to "C8"

A2      Daily load = 1250Wh
A4      Inverter Efficiency = 85%
A5      Account for inverter inefficiency - Load (A2/A4) = 1470.5
A7      System Voltage = 12
A8      Total A-hr demand per day (A5 / A7) = 122.55

B1      Number of days of autonomy = 5
B2      Maximum allowable depth of discharge = 70%
B3      Battery capacity (A8 x B1 / B2) = 875.35Ah
B4      Lowest 24 hour average temperature c
B5      Temperature correction factor =.97
B6      Adjusted battery capacity (B3 / B5) = 902.42
B7      Selected Battery
B8      Selected battery discharge rate 100
B9      A-hr capacity of selected battery = 225Ah
B10     Number of batteries in parallel (B6 / B9, rounded off) = 4
B11     Number of batteries in series (A7 / battery voltage) =1
B12     Check Capacity of selected battery at l00 Hr rate = 225
B13     Capacity of battery bank at 100 hr rate (B12 x B10) = 900
B14     Daily depth of discharge (100 x A8 / B13) = 13.62%

C1      Design tilt
C2      Design month
C3      Total energy demand per day (A8) 2.55Ah
C4      Battery efficiency = 90%
C5      Array output required per day (C3 / C4) = 136.2
C6      Peak sun hours at design tilt for design month = 5
C7      Selected module
C8      Selected module I at 14 volts at NOCT 2.94A
C9      Selected module nominal operating voltage. = 12V
C10     Guaranteed current (C8 x 0.9) = 2.65A
C11     Number of modules in series (A7 / C9) = 1
C12     Output per module (C10 x C6) = 13.2Ah
C13     Number of parallel strings of modules (C5 / C12) = 10.3

3) NOCT Normal Operating Cell Temperature.  This is "C8" and is user
input from the manufacturer's data.

 Oops, Tweedledee has his foot in his mouth again.

Posted by Ron Rosenfeld on July 15, 2008, 7:21 pm
 On Tue, 15 Jul 2008 05:51:06 -0700 (PDT), bealiba@gmail.com wrote:


Substitute GG for Tweedledee and you've got the right foot in the right
mouth!

GG still has failed to produce any real world items for use, and the
specifications he provides us with continue to need clarification which he
is unable to supply.

He has yet to justify the 14 Volt specification in C8.

He's now bringing in PTC.  I'm waiting for him to start talking about the
GTC (Ghinius Test Conditions -- a proprietary and secret method of rating
panels, which no manufacturer uses, but should, if they expect GG to
recommend their products).





--ron

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