Posted by Ron Rosenfeld on July 13, 2008, 10:38 pm
On Sat, 12 Jul 2008 17:21:56 -0700 (PDT), email@example.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
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), firstname.lastname@example.org wrote:
Yes it is sad that you obviously have no idea of the meaning of STC, PTC or
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.
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), email@example.com wrote:
Substitute GG for Tweedledee and you've got the right foot in the right
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).