Thursday, September 01, 2005


Two months of solar

I went through the charge controller's log of daily solar power received. Here's the chart:

  1. The first week or so I didn't have a functioning "Mate" controller, so I couldn't get the inverter to run in HBX mode, which allows for automatic switching to the grid when the battery voltage drops below a certain point. Since I was using the crummy old batteries at this point, I was restricted largely to using solar only when I was home and the sun was shining. That's why there are four approx. 1 kwh days in early July.
  2. The high daily value for the two months was 10.2 kwh. This was the result of not only the extended high-angle sunshine available in early July, but also because the shingles put out more than their rated 17 watts each when they are new.
  3. The new batteries were connected on August 12.
  4. This shouldn't be taken as a direct measure of how much solar power was available each day. If the batteries were fully charged and not many loads were running, the amperage will drop to a trickle or stop altogether, even in full sunlight. Once we figure out the dump load, there should be less wasted power.
  5. The average daily power before 8/12 was 5.47 kwh; after 8/12 it was 6.65 kwh. This occurred even though the days are getting shorter and the shingles newness is wearing off. (I think we've had more cloudy and rainy days, too.) This shows that I needed adequate battery capacity to take fuller advantage of the solar power available. With the old batteries, I was generally unable to use any solar power at night--the batteries discharged quickly, and that was it. With the new batteries, I can power the house all evening and through the night, leaving the batteries ready to receive more charge the next day.

have you considered using net-metering as your dump load? now that we've got that here in michigan (note to self, i need to stop by and see this thing up close and personal sometime - i'm in ann arbor too), it seems like a pretty decent way to go.

See this post for my answer on net metering:

Come on over and check it out!
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