Daily power output of solar panel below installed PV power

asked 2017-03-11 16:03:23 -0500

solarpanel_m gravatar image

updated 2017-03-11 18:15:43 -0500

We defined solar panel on the core zone of the roof using PhotovoltaicPerformance:Simple, assuming that the fraction of active solar cells is 0.5 and cell efficiency is 0.3. We compared the daily power output from the simulation with the power output of the installed PV and noticed that there were days when the daily power output was significantly lower.

Area of core zone = 150 sq.m

Area of 1 panel (assumed) = 1.5 * 05 sq.m

Number of panels on core zone = 100

Rated power of each panel(assumed) = 100 W

Power output of installed PV = 10 kW

Minimum daily power output from annual run of simulation = 2.3 kW-h

Maximum daily power output from annual run of simulation = 8.6 kW-h

Do these calculations look right? The daily power output doesn't particularly follow any trend for different months. The monthly power output for the array looks right. Any idea why we get such low values for daily power output?

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Comments

can you clarify in your question what you mean by energy and by power? Do you mean to say daily energy output in kWh?

And what is your location?

You can get a rough estimate of solar output using PVWatts

mdahlhausen gravatar image mdahlhausen  ( 2017-03-14 19:45:33 -0500 )edit

Our location is Miami. We realized that there was an error in our calculation. We used rule of thumb of 4 kWh per kW of installed PV per day to calculate the power output that we are supposed to get from our system. For a PV of 12% cell efficiency, fraction of active solar cells of 0.7 and area of 12.69 m^2, we got a value of 4.26 kW. But from the simulation's meter file, we found the minimum value of the daily power output for an entire year to be 2E07 J. That gives us 0.8 kWh per day (2E07/3600). Do these calculations look right? This value is significantly off from desired 4.26 kWh value.

solarpanel_m gravatar image solarpanel_m  ( 2017-03-14 22:29:42 -0500 )edit

We did a similar calculation for annual maximum value and annual average of daily power output and noticed that only the max value was over 4.26 kWh. We used the calculator on the link you suggested. The monthly average of daily power output was between 4-5 kWh/sq.m/day. Our monthly averages were almost half this value.

solarpanel_m gravatar image solarpanel_m  ( 2017-03-14 22:29:51 -0500 )edit

which weather file are you using, and does your model have any shading?

mdahlhausen gravatar image mdahlhausen  ( 2017-03-15 11:41:07 -0500 )edit

TMY3 weather file for Miami downloaded from the Energy Plus website. No detached shading elements, only PV shading on the roof

solarpanel_m gravatar image solarpanel_m  ( 2017-03-15 23:58:47 -0500 )edit