Wednesday, April 20, 2005


Making progress, slowly, surely, expensively

Rick did some research with the Uni-solar tech folks, and we've redesigned the project a little. We had planned on wiring the shingles in ten series groups of eight, for a nominal voltage of 72 volts. Unfortunately, this voltage would require purchasing expensive fuses and fuse holders in place of simpler breakers. Going with seven shingles per string avoids this problem, and will still provide sufficient voltage to fully charge the batteries through the charge controller. There will be a slight loss in efficiency (lower voltage means higher current means greater resistance loss), but both Rick and the Uni-solar techies think it will be minimal.

However, it does raise other issues. First, I have already bought 80 shingles, and 80 isn't divisible by 7. So I had to find four more shingles so I can have twelve strings of seven. Unfortunately, the shingles are in very short supply right now. A store in Phoenix was able to locate four for me, but at a premium--I paid $150 per shingle, as opposed to about $105 that I paid for the first 80. Also, the wiring in the attic will be a bit more complicated because the 84 shingles won't be organized quite as simply as 80 would have been. But we'll work that out. I've ordered most of the rest of the equipment we'll need to wire the thing up. We're hoping to do the shingle installation in mid-May, with most of the other work done before that. Hopefully I'll be running my house on solar power by Memorial Day.

Monday, April 04, 2005


The Most Important Step

So far, I've forgotten to mention the MOST important step in any renewable energy project--reducing your power usage. I did a lot of this in 2004, cutting my electricity usage from about 17 kilowatt-hours per day in 2003 to about 7 kw-h per day in 2004. My improvements weren't quite that dramatic, actually--my gas furnace conked out in March of 2003, and I didn't fix it right away, figuring warmer weather was right around the corner. Unfortunately, the warmer weather didn't show up until June, so I ran electric space heaters a lot that spring. Also, the 2004 reductions reflect to a small degree the impact of the two solar panels I bought, which I used to run 12-volt fans and the TV from time to time.

Still, most of the savings came from reducing my usage--replacing most of my incandescent light bulbs with compact fluorescents, turning lights off more diligently, and putting "phantom loads" on switchable power strips. "Phantom loads" are electical devices which are on even when they're off, like a clock on a microwave or VCR, or anything with a remote. These thing frequently draw three to five watts each, which adds up to a lot of electricity over the course of a month. Putting them on power strips allows you to easily shut them all the way off.

There are several other easy steps that can be taken to save power, and almost all of them are cheaper than buying more solar panels and batteries.

Once I get my PV system up and running, I'm going to go back and look for more ways to cut my energy use. A new furnace is probably the most obvious choice--the new high-efficiency gas furnaces will save me both gas AND electricity, since the generally have higher-efficiency blower motors than does the 1988 dinosaur in my basement. However, I may investigate something more elaborate, like solar-assisted radiant heating, or maybe incorporating a wood stove or through-the-wall solar, or a ground-source heat pump.

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