Among the green power projects in the works, the molten salt technology to tap solar power is receiving wide attention.
The sun could be an efficient source of energy, but it is not all that reliable. It fluctuates, and it turns off at night, as you might know! A way out is to store the solar energy in the form of heat using molten salt.
An aerospace company, Hamilton Sundstra, created a venture called SolarReserve to try out the idea and is hoping to generate 500 megawatts of peak power, the size of a typical power plant.
"The molten salt holds its heat very efficiently and for long periods of time," said Dan Coulom a spokesman at Hamilton Sundstrand last year.
He also revealed that the company planned to build as many as 10 plants over the next 10 to 15 years, pulling in revenues of $1 billion over that time period.
SolarReserve is now saying it is working on agreements with several utilities to buy electricity generated from the plant. It hopes to have several announcements in a few months that could help jump-start construction of the first plant in California, according to company's President Terry Murphy.
The plant could begin operating by early 2013. It would use an array of 15,000 heliostats, or large tilting mirrors about 25 feet wide, to direct sunlight to a solar collector atop a 600-foot-tall tower, somewhat like a lighthouse in reverse.
The mirrors would heat up molten salt flowing through the receiver to more than 1,000 degrees, hot enough to turn water into powerful steam in a device called a heat exchanger. The steam, like that coming out of a nozzle of a boiling tea kettle, would drive a turbine to create electricity.
The molten salt, once cooled, would then be pumped back through the solar collector to start the process all over again. "The plant has no emissions, and if you have a leak or something, you can just shovel it up and take it home with you to use for your barbecue," Murphy said.
The molten salt can be stored for days if not weeks and then used to generate electricity at any time. Many other solar technologies work only when the sun is shining. Storing electricity in a battery works for cars and homes but not on a massive scale that would be needed to power thousands of homes.
"You can put that into a storage tank that would look much like a tank at an oil refinery," Murphy said. "We can store that energy almost indefinitely."
While there are high hopes for the technology, some environmentalists have criticized solar-thermal plants for requiring vast tracts of land as well as precious water for generating steam and for cooling the turbines, Peter Pae reported for Los Angeles Times.
The array of the mirrored heliostats for the SolarReserve plant would take up about two square miles. Transmission lines would also be needed to transport the power where it's needed. With dozens of solar, wind and geothermal projects planned for California's deserts, some fear that this unique habitat will be destroyed.
But SolarReserve officials said that the plant would use one-tenth the amount of water required by a conventional plant and that mirrors will be "benign" to the environment.
The solar-thermal technology was proved workable more than a decade ago, but the attempt was given up in 1999 when the cost of natural gas fell to one-tenth of what it is today.
Also there wasn't as much concern for the environment then, Murphy said. "It was ahead of its time. The market hadn't caught up to it."