Solar energy storage uses salt mixture for power generation

If the word "solar" is used to characterize the industry, it is the word "big": in the desert, a total of square miles of mirrors surround a 600-foot tower that produces The number of megawatts of electricity, while the cost of billions of dollars at every turn. However, the ability of large solar companies to compete with fossil fuels may ultimately depend on those salt particles.

Scientists at Halotechnics, a startup in the solar-thermal-power industry, are screening thousands of molten salt mixtures in a small lab in the Emeryville, San Francisco Bay Area biotechnology center. They are looking for a suitable molten salt mixture that will allow solar thermal energy to be stored in a cost-effective and efficient manner, so that it can be used to generate electricity after the sun sets. In other words, it can be a 7 days a week, 24 hours a day uninterrupted power supply of solar power stations.

Molten salt storage technology as early as the 90s of last century had appeared, when the United States United Technologies (United Technologies) under the Rocketdyne (Rocketdyne) rocket engine department for the "SolarTwo" developed molten salt storage technology, SolarTwo is the US Department of Energy A solar thermal power station prototype facility built in the Mojave Desert. A row of heliostats focuses the solar energy on the top of the boiler, which contains a mixture of salts that liquefies at high temperatures. The thermal energy released by the molten salt is used to generate steam, which drives the turbine to produce electricity. Some of the heat can be stored in a pot of molten salt, so that when released, to generate electricity.

However, due to the Clinton era of oil prices plummeted, the United States to abandon its ambitious solar thermal power generation test, and molten salt technology has also been sidelined. "There has not been much innovation in this technology lately," says Mark Mehos, senior solar project manager at National Renewable Energy Laboratories in Goldon, Colorado.

Now, the molten salt technology to return to the scope of people to consider, such as California and other states to complete the renewable energy in the total energy composition accounts for a certain proportion of the arduous task, have approved large-scale solar thermal power projects. Utilities are hoping that these plants will store solar energy so they can be used to balance power grids increasingly powered by intermittent power sources such as wind power. By 2015, the market for solar energy storage will reach $ 3.7 billion, according to GTMResearch, a market research firm of GreentechMedia.

JustinRaade, 34, founder and chief executive officer of Halo Technology, sees an opportunity. In 2009, Laird, who received a Ph.D. in mechanical engineering, worked for Silicon Valley, a materials science company called Symyx. "I had been looking for a major problem in the renewable energy sector, and the more I knew about concentrating solar power, the more I realized that solar storage was a bottleneck," he said. Concentrating solar power can not be cheaper than fossil fuels. "

His idea is to find a better molten salt mixture that can store heat at higher temperatures to increase the amount of electricity produced while maintaining a liquid state at lower temperatures, To avoid the curing of energy consumption.

Laird received $ 1.5 million from the US Department of Energy, and in 2009 began screening 5,000 different molten salt mixtures at Simex. With the help of an investment from Simex and the licensing of its intellectual property, Laird founded Halo Technologies. The start-up used another $ 4.5 million in government research funding to develop its first molten salt product, and began to develop a new type of glass liquid storage system. "We have developed a new oxide-based chemical that is much less viscous and has a much lower melting point compared to other glass materials, and in fact you can use a pump like a liquid It is stored in a large jar like a molten PV module using a grade of salt, but it is stable in a much higher temperature environment.

The temperature can be as high as 1,200 degrees Celsius, the temperature is high enough to make the air heated enough to drive as in fossil fuel power plants that use efficient turbines. In the lab, Lloyd picked up the paper cups containing green and black glass, and Halo Technology wanted the two promising mixtures to eventually be used as prototypes for a solar energy storage system. It is planned that the system will be put into use in 2015.

Elsewhere in the lab, Halo Technologies continues to screen nearly 100 molten salt mixtures daily - nearly 14,000 molten salt mixtures have been screened so far. The current molten salt mixture is usually 60% sodium nitrate plus 40% potassium nitrate. Halo technology company's goal is to use the company for the time being only to be disclosed as "adequate resources and low-cost salt substances" to replace about eighty percent of the increasingly expensive potassium nitrate.

The start-up's proprietary software identifies potential candidate mixtures based on melting point, endotherm, and cost. Its laboratory equipment can simultaneously measure, mix and provide 96 different mixtures. A quarter of the mass of the mixture was first baked in a furnace and then placed in a device to heat slowly, and the melting point was determined by firing a laser through these substances. "Rather, these machines were left unused in the corners of the Simex labs," said Laird.

Halo's thrifty - engineers who design storage tanks and pump systems sit shoulder-to-shoulder in the office lobby - meaning that the company expects to raise just $ 2 million in first-round financing to develop A set of molten salt storage pilot system, and then raise 5 million to 7 million US dollars will be able to enter the commercial sales stage.

The company has preliminary discussions with solar thermal power plant developers such as eSolar, Sener and BrightSourceEnergy, which expect energy storage technology to give them the advantage of competing with photovoltaic power plants. Although the price of PV modules has plummeted by 75% in the past three years, the only option to save the electricity generated by solar panels is the prohibitively expensive battery.

Halo Technologies claims that the company's first product, called Saltstream565, will be at least 20 percent cheaper than existing storage systems because it uses less expensive salt mixtures to achieve the same operating temperatures as those used by SolarReserve - 565 degrees Celsius, SolarReserve is a solar power plant developer, the company from the United States United Technologies Corporation where access to technology licensing. But the halo technology company also can be 700 degrees Celsius in the operation of the molten salt mixture applied for a patent. A higher operating temperature means that solar power plants can use the latest and most efficient turbines.

Craig Tyner, who has worked on molten salt storage at Sandia National Laboratories, is planning a long-term technology strategy for eSolar, a company based in Pasadena, Pasadena) solar power plant developers. "It would be very beneficial for us to have a salt mixture that would increase our current operating temperature by 50 degrees Celsius, because it would store more energy in the same amount of salt mixture," he said. Can reduce the cost of storage systems by 10% or 15%. "

Spanish solar power developer Sener has developed its own molten salt storage system, according to MercedesSierra, the US subsidiary of Sener in San Francisco. The company sees HaloTech as a potential Of the partners. "We've been exploring the possibility of testing their products at our power stations," she says. "We need a high quality salt mixture that we are willing to pay for."