Saturday, June 6, 2009

Learning to Monitor What the System Does


I've been walking to the side of the house and checking the PSE&G electric meter all day. When the sun is out it spins backwards, often pretty fast, as evident in this video:

video

That, of course, means we're generating excess power which is going out through the meter and onto the power grid. We'll get credit for those kilowatt hours (see the description of "net metering" above.)

It was interesting to watch what happened when a cloud passed in front of the sun. Earlier in the afternoon the meter continued to spin backwards but at a much slower rate. Later, presumably after the sun was approaching the horizon, the meter actually stopped altogether (meaning the system was producing exactly as much as the house required) or even reversed direction until the cloud was gone.

Also, we noticed that running the vacuum made a significant difference in the speed of the meter spin. This is probably going to make me think more about the power that various electrical equipment uses, solar issues aside. Hopefully this won't turn me into too much of a miser. I already caught myself before asking my daughter "Do you really need to do that?" when she took her boom box out back to listen to Miley Cyrus with her friends.

I was going to report today's meter readings but now as I look at them I realize I may not have read them all correctly. It's difficult to read those numbers, which are presented in a series of 'dials' rather than a simple readout.

We think we've figured out out how to read the inverters to determine how much energy the panels are throwing. We're going to record those numbers, as well as a careful meter reading, every day at 7:00 p.m. (and report the data here, of course). Maybe after a few days we'll start to understand what the numbers all mean and what the effect of running our system really is.

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