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  • From: Bill Jones <billj AT harborside.com>
  • To: Homestead mailing list digest <homestead AT lists.ibiblio.org>
  • Subject: [Homestead] Power vs. Energy
  • Date: Tue, 01 Mar 2005 08:27:13 -0800



Breakthrough in solar photovoltaics

THE HOLY Grail of researchers in the field of solar photovoltaic (SPV) electricity is to generate it at a lower cost than that of grid electricity. The goal now seems to be within reach.

A Palo Alto (California ) start-up, named Nanosolar Inc., founded in 2002, claims that it has developed a commercial scale technology that can deliver solar electricity at 5 cents per kilowatt-hour.

.......

The flagship product, Nanosolar SolarPly, is a 14 feet x 10 feet solar electricity module delivering 120 watts per square inch at 110V. The company is now offering solar panels at below $1 per peak watt.

The first problem I found with this is that solar cells are usually described in terms of the price per watt (the RATE of energy output), not KWH (a measure of total energy). That's because price and wattage are the two fixed quantities associated with a solar cell. The number of KWH it generates over its expected lifetime depends on how long it keeps functioning (in our case, not long; once the solder loosens, it's over). If a product is brand new, how can you have any idea at all how long it will normally last?

But it was the second part that really set off my BS detector. I'm trying to find some other interpretation for what's written here, but 120 watts per square inch is far more energy than what is contained in sunlight. Maybe you're supposed to concentrate the light with a lens first. Since sunlight has about a kilowatt (1000 W) in every square meter (almost 1600 sq. in.), it cannot possibly generate more than _one_ watt per square inch, and generally nowhere near that, since at most 10% of the energy is converted to electricity.

Bill





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