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.

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