Posted by Bob on May 9, 2008, 9:08 pm
On May 9, 1:00 pm, d...@25.usenet.us.com wrote:
Not _my_ numbers, the NSRDB's
That's great, thanks for the information. So in this thread we have
two pieces of data that I was looking for:
1) Doug, output measured with a SMA 6000U inverter 1,593 kWh/yr per
kW system STC. NSRDB 1991-2005 data for Long Beach, insolation is
1,788 kWh/yr/m2. Performance ratio using this data is 89%
2) Clarence, output measured with a Fronius inverter 1,616 kWh/yr per
kW system STC. Insolation -- no nearby data in the NSRDB.
The above figures are total output from the photovoltaic system. To
measure net output, I think you would need a separate, bidirectional
BTW Clarence, if you have a chance, take a look at the NSRDB 1991-2005
and let me know if I am missing anything. It seems that there are no
sites in the Clear Lake area. The closest sites I find are Ukiah,
Santa Rosa, and Napa, and they would be a stretch.
Would anyone else like to contribute some data?
Posted by dold on May 10, 2008, 3:00 am
I'm not sure what other losses you expect. 20 feet of wire from the
Fronius to the PG&E box? I'd introduce more loss with another meter than
what I would expect to see dropped on that wire.
That sounds like the "nearby" set for weather as well. Those would not be
comparable weather... maybe Ukiah. Certainly not Napa, too cold and foggy.
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5
Posted by Bob on May 10, 2008, 7:46 am
On May 9, 8:00 pm, d...@25.usenet.us.com wrote:
to the PG&E box?
1) Standby tare losses for the inverter when the solar panels are not
generating any electricity. The one inverter I have a figure for is
the Xantrex PV 10, where it is <30 watts. Low total if the inverter
is off at night and if it always performs within its specs -- but you
don't know until you measure it.
2) power to warm up a cold inverter every morning -- I don't have a
figure for that, I was told by one person in the monitoring field that
it was in the range of the standby tare losses at night, i.e., there
wasn't a big difference between leaving the inverter on at night, or
leaving it off and powering it up every day.
dropped on that wire.
More questions. What's the loss with another meter? More than in 20
feet of wire but less than the inverter standby losses I would guess.
Too late to look that up right now.
Posted by daestrom on May 10, 2008, 2:42 pm
Why should an inverter draw a lot of energy to 'warm up' when first powered
up every day? I don't understand this point.
Posted by Bob on May 10, 2008, 6:17 pm
That's an email response I got from tech support from fatspaniel last
year. 1) "The inverter draws power during its standby mode to keep the
complex electronics and electrical conversion mechanics ready for when
there is production" and 2) "I am not sure that the amount of power
needed to warm up a completely cold inverter is any less than
maintaining it on standby all night."
At the time, I just accepted it the second statement. But it
shouldn't take much to "warm up" a solid state device. Tech support
can be mistaken, and if the statement is wrong, I am glad to get that