Living off the Grid, Part II: Northern Exposure

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Installers are encouraged to familiarize themselves with article 690 of the National Electric Code (NEC), dealing specifically with photovoltaic equivalent, before installation.

KT: No. You'll be drawing off the bank. It's like a savings account, if you're not putting money in ....

If it's cloudy, the panels will produce about 5% of their normal output-an amp or two. And when it's really cloudy, or after 3 o'clock when the sun dips below the ridge to the west, if I'm getting 2 amps, I'm lucky. If I'm only running lights in the house, I'm not drawing very much. But if I'm also running any tools, then I'm dipping into my savings account and running a deficit.

Twenty-two amps is the most I've gotten at any one reading. It averages-this time of year anyway-about 17 amps at any particular sunny moment.

MOTHER:Any other problems in winter?

KT: The direction of the light often poses some problems during the short days. The sun is lower in the sky and I have to be

careful about the trees creating shadows. Today at about noon, the sun was starting to shine on the modules through one of the trees, and instead of getting 18 amps out of the system, it suddenly went down to like 7.5 to 8. I looked at the meter and said, "Wait a minute. It's sunny out. What's going on?"

I ran around and looked at the panel and noticed the shadow of the tree across it. Shadowing even small portions of the panel changes many of the solar cells from producers into laggards. These few can reduce the efficiency of the whole array considerably. I mean, that's an area where technology definitely needs to work on it some more, I think.

MOTHER:I noticed some compact fluorescent bulbs in the work areas and basement. Do they really make a difference?

KT: Without them I could not afford to use my solar system, period. I've measured their output, because there's a meter down in the basement that reads the power flowing from the batteries all the time. If I turn on an incandescent light, it will read 3 to 3.5 amps of output. If I turn on a compact fluorescent, it's 0.6 amps. I can have five of them on, which is more than the house will ever need, and equal the consumption of one incandescent bulb.

Conventional fridges are tough on the system, too. I'll need to shop for a more efficient model than most homes use.

MOTHER:Right now you're planning on a propane water heater for the house?

KT: Yes. A propane water heater and a wood stove for heat. The refrigerator might end up being propane, too. It makes sense. We'll only need to fill the tank twice a year, it's on the outside of the house so we'll feel safe and save on space, and it's relatively inexpensive.

MOTHER:So power flows from the modules to a battery bank in the basement?

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