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Here comes the sun ... shower

By Larry Hunter (China Daily)
Updated: 2009-02-13 07:42

The Obama administration is poised to start a huge program to develop renewable energy sources - and at the same time, it hopes, create jobs, limit pollution and narrow our trade imbalance. The program is likely to include incentives for conservation - to encourage people to insulate houses and buildings properly, drive cars that need less gas and use low-flow shower heads and high-efficiency lighting. Reducing energy use, after all, is the cheapest way to reduce our carbon footprint.

But after conservation, one of the most effective and efficient steps the government can take is to encourage the use of solar hot-water systems - a well-developed and relatively low-tech method for using the sun's energy.

Solar hot water systems are not as well known as the electricity-generating solar panels that use photovoltaic cells to gather energy. But hot water systems are more efficient than photovoltaic systems and can create the same amount of useful energy with fewer panels. Water heating accounts for a large share of a home's energy use - typically the largest share after heating and cooling.

Three 1.2 x 2.4m panels can, in full sunlight, deliver about 4.5 kilowatts of heat - enough to heat about 50 percent to 80 percent of the water used by a family of four. The cost to install such a system, including the panels, a water storage tank, piping, a pump and control electronics is usually less than $10,000.

In comparison, a photovoltaic system that can produce 4.5 kilowatts in full sun requires 11 like-sized panels and costs about $40,000. Here in New England, where our annual average illumination is equivalent to only about three hours of direct sunlight per day and relatively high electricity rates (about 16 cents per kilowatt hour), either system can replace about 5,000 kilowatt hours of energy a year. A conventional coal-fired power plant delivering the same amount of energy would emit about five tons of carbon dioxide. But the hot water system pays for itself in 13 years, while the photovoltaic system takes about 50. In places with more sunlight like the Southwest, much more energy can be produced.

Solar hot water systems also work better than many photovoltaic systems in partial shade. And they are simpler and easier for most contractors to install.

Ramped-up production of solar hot water systems would create jobs. Construction workers, many of whom are out of work, possess skills needed to install the systems. Several manufacturers of solar hot water panels and storage tanks are based in the United States. Increased production would also shore up demand for aluminum, which has declined as the American auto industry has shrunk.

Since Jan. 1, a federal solar tax credit has been available to homeowners for up to 30 percent of the installed system cost, with a cap of $2,000 on solar hot water and $5,000 on photovoltaics. If Congress and the Obama administration were to raise the individual tax credits to 40 percent or 50 percent, and the cap to $5,000 on both systems, it would reduce the payback time on a solar hot water system to only six to eight years. At the same time, we would be taking a step toward a sustainable energy future.

The author is a professor of physics at Amherst College

The New York Times Syndicate

(China Daily 02/13/2009 page9)