Monday, May 11, 2009

The Price of Solar Power is Falling

The Wall Street Journal reports that the recession has pushed down the cost of solar power. Back in the late 1970’s when I first looked at the idea of solar power and PV cells the cost per watt was something like $120 just a last year the price was $4 or more. Now it seems that the cost has been pushed as low as $2 per watt. That does make you want to buy. However, not all states offer incentives.
In the 1950’s when Bell Labs fist developed the PV cell operating efficiency was 4%, in the 1970’s efficiency was 9%. Currently efficiency is 15% and there are developers working on higher efficiency PV and concentrating systems. Between manufacturing cost reductions and increase efficiency we find ourselves with solar PV cells at $2 watt. Is that good enough?
Today a PV cell provides 1,000 watts per square meter (costing $2,000 at the current recession discount). At noon on a cloudless day in the Arizona desert (optimal conditions) that square meter produces an impressive 6 kilowatts hours per day. Unfortunately, most of the United States (my address included) has less than optimal solar conditions for much of the year. For the worst part of the year with the current 15% efficiency I calculate that I would get less than 1 kilowatt hour per day from that square meter of solar PV cell in the winter and rainy days, the optimal production for my location seems to be about 4 kilowatt hours per day (despite my location on a knoll and with a dead on southern facing roof). Even this level of pricing does not meet my hurdle rate of return on investment (the best use of my money). Despite my goal to someday move off the grid which will take a combination of technologies, I am tethered until solar and residential turbine technology make the next leap. Until that time, passive solar techniques are where I'm spending.

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