Arizona Solar Power Plant Keeps Lights On Even After Dark

By Joelle Renstrom | 8 years ago

SolanaWhat’s not to love about solar energy? It’s plentiful, relatively cheap, and it’s not going to run out any time soon. Of course, there’s a catch: what happens when it’s dark? If you’ve ever used solar powered lights or other gadgets, you’ve undoubtedly noticed that when the rays disappear, you only have a matter of minutes before your device loses power. You didn’t think that would remain a problem for long did you?

The Solana Generating Station, a solar power plant located about 70 miles outside Phoenix, has found a way to supply solar power to over 70,000 Arizona homes for up to six hours after the sun sets. This represents a major technological advance from conventional photovoltaic technology that relies on direct sunlight. It also helps that Arizonians don’t have to worry so much about winter weather and long, cold, dark nights. Can you tell how excited I am that winter is coming to Boston?

The three-square-mile Solana facility, one of the biggest of its kind in the world, collects the sun’s heat using thermal energy storage and concentrated solar power technology. During peak energy usage time—ie, television and internet time between coming home from work and going to bed—the cutting-edge tech churns out up to 280 megawatts, which keeps the lights on for tens of thousands of Arizona residents. Solana’s solar energy portfolio has increased by almost 50 percent, which Arizona Public Service Company (APS), which is purchasing all of the energy being generated by Solana, believes will “make Arizona the solar capital of America.” All that hot-as-hell sun should be good for something.

Solana harnesses heat from the sun using 2,700 sun-following parabolic trough mirrors. The mirrors direct the sun’s heat on a pipe full of a heat-transferring synthetic oil, which reaches temperatures of approximately 735 degrees. Then they dump the oil on invaders storming the castle…oops—I guess I never stopped thinking about Game of Thrones. Anyway, this super hot oil then travels to the boilers where it converts water into steam. The steam then powers two 140-megawatt turbines, which produce the electricity.

This process is pretty typical of power plants, but what makes Solana special is that the oil also heats up molten salt kept in tanks next to the boilers. The facility has six pairs of tanks (one hot and one cold in each pair) that collectively contain 125,000 metric tons of salt. You could season a lot of French fries with that. The salt maintains a temperature of at least 530 degrees, so after it gets dark and the mirrors are no longer harnessing the sun, the salt heats up the oil, and the plant continues to generate steam for upwards of six hours.

APS will be able to provide solar power to an impressive 185,000 customers by the end of the year. If they can just find a way to convince the sun not to make itself scarce in the coming months, I’ll subscribe from here.