Monday, March 9, 2009

Spring has sprung!

Almost exactly a year ago, I first hooked up my solar electrical system and started drawing power from the sun.

I can tell spring has come now, because I looked over at my solar controller and saw it pulling in 10 amps! That's something I haven't seen in a long, long time, probably not since September.

I'm stunned at the tremendous variability in sunshine here in the northern latitudes of California. It's a huge difference: from 10 amps a lot of the day in the summer, to maybe 1-2 amps for a few hours of the day on rainy days in the winter.

There are several problems. First, San Francisco is in the upper latitudes, so the angle of the sun is lower, especially in winter. So my flat-mounted panels just won't pull in during the winter. Secondly, and also because of the high latitude, the hours of sunshine varies a lot between winter and summer. And, finally, California has a wet season and a dry season. It does not rain all spring, all summer, and all fall! Then we get all our rain in the winter... and then it's over.

Which means: LOTS of rainy days in wintertime, combined with few hours of sunshine, and a very low angle of the sun. So the factor of sunshine between winter and summer is like 10-to-1.

I installed my system in the springtime and started designing my usage based on that type of constant availability of sunshine. As I've blogged before, the end of October was a disaster for me: the rainy season startd, and my electricity usage suddenly way outstripped availability. I recovered by buying a small, low-power netbook. But still, that cost me a lot of money.

Now that spring has come, I can relax a bit more and be somewhat more lavish with electricity. But I've learned just how seasonal this type of thing is.

If anyone is designing a solar electrical system for their van (or for anything), my advice would be: design your system so that it provides enough power for all your uses, in the dead of winter with next to no sunlight. That will be expensive, but not as expensive as having to purchase new, more energy-efficient gear to cope with the lack of sunlight in wintertime.

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