## Wednesday, February 21, 2007

### Solar power

With the exception of nuclear fusion, solar power remains the greatest untapped energy resource available on the planet. The diagram on the left demonstrates the magnitude of the flow of energy from the Sun reaching the Earth's surface (89 petaWatts), compared to the average power consumption of humans (15 teraWatts). Solar power is generally expected to become a competitive rival to fossil-fuel power circa 2030, but an article in the Daily Telegraph (www.telegraph.co.uk/money/main.jhtml;?xml=/money/2007/02/19/ccview19.xml) claims that "Within five years, solar power will be cheap enough to compete with carbon-generated electricity." The article goes on to claim that "The "tipping point" will arrive when the capital cost of solar power falls below $1 (51p) per watt, roughly the cost of carbon power." This is a rather strange assertion, because the tipping point for solar energy is generally considered to be the point at which its financial cost, per kiloWatt-hour (kWh), drops to the fossil-fuel cost per kWh. The current cost of fossil fuel power is about 5 cents/kWh. Now, without patronising the reader, a Watt is 1 joule of energy per second, and there's 3600 seconds in an hour, and 1000 Watts in a kiloWatt. So$1 per Watt is \$3,600,000/kWh, or 360,000,000 cents/kWh.