We are now really into the heat of things. May is the third most important month for solar radiation. So it is very important to maximize the power one generates in May. Only July and June are more important.
May 2012 was good month. Lots of sunny days. Plenty of mixed sun and cloud days. Just a few rainy days. Pretty much what one would expect. So now that the Deger tracking device has been fixed, we should have been generating power almost at the top of our potential.
At the end of April, I reported that our meter read 5720 kilowatt hours. Last night, once the sun went down, it read 7693. So we generated 1973 kilowatt hours. That is still short of the 2151 projected by PVwatts. It is 91.7 percent – much better than any other month, so far, but still shy of what we would have hoped.
Why?
PVwatts measures solar radiation in Ottawa, the closest big city. But Ottawa is still an hour’s drive away. Is it possible that there is a significant variation in solar radiation between here and Ottawa?
I have searched in vain for a regional radiation map. Anything I can find is Canada-wide, like the one below. If anyone knows where I can find more localized solar radiation data, I would love to hear from you.
In any case, the payment for May will still be by far the largest one yet, and the system is still a positive investment. So I am smiling even as I scratch my head.
LOL i imagine when you scratch your head..This summer it is really helpful to a solar panel to get a lot of energy.Pretty good blog.
Steven, I believe they are each 250. The entire system creates 10,000 kilowatt-hours of AC Capacity, which requires about 12,000 of DC input. So each panel shoud have about 250 watts absorption capacity.
Nice Blog. I see that you have 48 panels on your two trackers. What wattage are the panels?
Thanks and keep up the good promotion
What values did you use as inputs for the PV Watts calculation?
Using the online PV Watts calculator found here:http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/
I used the input variables of:
-Input 10kW (assuming you have 10kW rated inverter(s))
-Derate .77 (as recommended by PV watts)
-2 Axis tracking (should be an underestimate as Deger claims to be better)
-Tilt/azimuth should not matter as it’s 2 axis tracking
Anyway, with those variables I got a much smaller number than you did for the Ottawa area. 1706kWh AC for the month of May. So an underestimate of what your system produced. Probably due to the lack of rain we had this May. If I change the derate to .81 as your panels might not be dirty as is assumed by PV watts. With that change I get 1795kWh, still an underestimate. If I again, change the derate to assume your inverter and transformer are 99% efficient I get 1949kWh. This is still a small underestimate.
Have you tried double checking your PV watts calculation?
With warmer-than-normal temperatures, you will certainly need to derate for that.