Peak Generation Percentage?

[Walt Bilofsky]

Can anyone help me out with an estimate of the percentage of their
total PV power generation that comes from the period noon-6 PM?

I'm in the San Francisco area (38 degrees north latitude) and trying
to size a system, using the time-of-day metering tariff that pays
higher rates for that time period on weekdays.

I understand it depends on the orientation of the panels but any
figures would help me get started.

FWIW I will have panels tilted 22 degrees and divided between SSE and
WSW orientations.

Thanks,

Walt Bilofsky

 

[Paul]

Can anyone help me out with an estimate of the percentage of their
total PV power generation that comes from the period noon-6 PM?

I'm in the San Francisco area (38 degrees north latitude) and trying
to size a system, using the time-of-day metering tariff that pays
higher rates for that time period on weekdays.

I understand it depends on the orientation of the panels but any
figures would help me get started.

FWIW I will have panels tilted 22 degrees and divided between SSE and
WSW orientations.

Thanks,

Walt Bilofsky

Sounds like you are putting them on both sides of a pitched roof.
The SSE panels will obviously give you more in the morning and
the WSW would give you more in the afternoon. I am not sure that
this is the optimal use of expensive panels.

 

[Walt Bilofsky]

Sounds like you are putting them on both sides of a pitched roof.
The SSE panels will obviously give you more in the morning and
the WSW would give you more in the afternoon. I am not sure that
this is the optimal use of expensive panels.

No, but it's the optimum use of the limited roof space I have
available.

I'm putting them on two adjacent sides of a garage roof. (The house
roof is shaded and gives other installation problems.)

I was able to get a hour by hour estimate of power output by using the
PVWATTS v.1 calculator at
http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/ . After
creating an estimate of output using my specified location,
orientation and tilt, there was an option to create an hour by hour
output estimate. With some spreadsheet massaging, I was able to
calculate that with an orientation of 160 degrees, roughly 50% of the
output would be in the peak (noon to 6 pm) billing period, and with
the 250 degree orientation, roughly 66%.

If I had room, I'd put them all facing 250. But I don't.

 

[Paul]

No, but it's the optimum use of the limited roof space I have
available.

I'm putting them on two adjacent sides of a garage roof. (The house
roof is shaded and gives other installation problems.)

I was able to get a hour by hour estimate of power output by using the
PVWATTS v.1 calculator at
http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/ . After
creating an estimate of output using my specified location,
orientation and tilt, there was an option to create an hour by hour
output estimate. With some spreadsheet massaging, I was able to
calculate that with an orientation of 160 degrees, roughly 50% of the
output would be in the peak (noon to 6 pm) billing period, and with
the 250 degree orientation, roughly 66%.

If I had room, I'd put them all facing 250. But I don't.

Sounds like you have a pretty good handle on the situation.
It looks like putting as many as you can on the 250 location
works out for the best. If you don't have very much room, put
the most efficient ones you can find on your roof.
http://www.sunpowercorp.com/html/Products/Solar/modules.html