英语听力：自然百科 太阳能

The most powerful source of energy on the planet is actually out in space. It's our sun. More energy falls as sunlight on the US in a single day than it uses in a year. But it's been difficult to turn that sunlight into electricity. Many of us already use some solar energy, but the world has a big appetite for power, and solar power has to be competitively priced and reliable.

One good role model is in California. Sacramento, the state capital, is one of the nation's leaders in solar power. Many new homes are equipped with solar cells, and solar panels shade parking lots and city buildings. But most importantly, Sacramento has shown that buying in bulk can dramatically reduce the price per unit, and that people can actually save money using solar power, or make money.

California, along with many other states, has started net metering. It lets citizens sell their extra solar power back to the utility, for exactly the price they would otherwise be paying for. If they use less power than they produce, the utility sends them a check.

Deep in California's Mojave Desert, there is a solar generating plant that dwarfs all others. The Kramer Solar Junction power facility, covering more than one thousand acres, creates more energy from solar power than every other solar panel in America combined--one hundred fifty megawatts in all.

“…which add that full capacity is enough power for the residential needs of about half a million people.”

Unlike photovoltaic systems which capture the energy in the sunlight directly, these mirrors reflect the light onto a tube filled with synthetic oil. The seven hundred degree oil then goes into aboiler that runs an electric turbine. Each segment also has a backup natural gasgenerator, so rain or shine, they can always supply the power Los Angles expects while creating very little carbon dioxide or smog.