Friday, July 4, 2008

Solar Energy: Saved by the Sun

Solar Energy: Saved by the Sun is a PBS documentary (a Nova episode) covering the solar energy industry, developments in solar technology, and generally presenting solar energy in a very positive and with a, uh, bright future. The documentary doesn't go into great depth but has great information in it. Interviewees include two members of the German Parliament, the Director of the National Renewable Energy Laboratory (NREL), Amory Lovins, several people who have installed solar systems in their houses, farms or businesses.

In Germany there are deep incentives for solar and wind power. This has led to massive growth of industries to build these technology, and massive installation of these technologies. Germany passed a law, as has many countries, to set a target for 20% renewable by 2020. However it appears Germany may well exceed this target. A pig farmer was interviewed, who has installed a massive 1 MW solar array on his farm. It cost $5 mil investment, earns very significant revenue every year, but they claimed that what made it work was the incentives. Without the guarantees in the incentive program the banks would not have lent the required money.

Which leads to a question of what will happen if/when the incentive program ceases.

A theme returned to over and over is a key flaw in solar or wind power is they don't produce electricity when the sun is down, or the wind is not blowing. There aren't battery systems which can store sufficient power to drive a whole city for any length of time. Therefore the essential feature of electricity is it cannot be stored. Electricity which can't be stored is not much use, further at night when the sun isn't shining how would we power our houses.

This leads to a situation where solar powered houses are still tied to the grid, so that they can draw on the grid when the sun isn't shining. You might think, oh, that's cheating. Well... It's pragmatic is what it is. Some solar advocates are purists, nothing but solar power for them thank you very much. However that means they require batteries to store their power to have lights when the sun doesn't shine. The battery pack raises cost and complexity of their systems. And, if the house is grid-tied then the grid becomes the battery pack to store electricity.

A point presented in several ways throughout the documentary is that it is when the sun is the hottest that electricity demand is highest. Because American houses are misdesigned and heat up badly when it's hot (they could be designed to be less affected by heat) American's learned response is to crank up the air conditioner. Cranked up air conditioners are what cause the steep power demand during the day. Hence solar power can be what provides peak power during the day when the power is most needed.

Rather than it being a flaw that solar panels only produce when the sun is shining, looked at from another angle it is a blessing that solar panels operate when their power is most needed.