Calculations

[mark1965]

Going over the dvd on the PV calculations for figure 6-100. Need a little breaking it down. I am good down to the last 3 lines.

 

[jaggedben]

You'll need to spell out the question. This is a Mike Holt DVD?

 

[mark1965]

It is Mike Holt DVD. PV= voc 22.60vocX{1+(-13.27%)}X23 modules
PVvoc= 22.60 voc X0.8673X23 modules. What I do to get the 0.8673?

Thank you,
Mark

 

[jaggedben]

I don't have the DVD so I am guessing here. But it sounds like this is a voltage calculation for hot temperatures.

Module specifications will typically state "temperature coefficients, which are percentage variations in voltage (and current) for each degree difference from 25C, which is standard testing temperature. It is stated as a negative percentage because voltage goes down as temperature increases. The value is typically a fraction of a percent, for example, -0.34%. Thus the -13.27% is probably the product of multiplying the given temperature coefficient by the number of degrees above 25C that the system is expected to operate at in a maximum temperature situation.

If you're considering a low temperature, for max pv voltage, it will be the negative percentage multiplied by a negative number of degrees (i.e. degrees below 25C), so then the voltage will be 1+the percentage, and will be higher than the panel specification.