Cheap Solar Power at Night
Solar storage: The beads in these vials are made of two types of glass that can store heat up to 1,200°C. Halotechnics
Solar power has two main problems: it’s expensive, and it’s intermittent, since the output of a solar power plant depends on the time of day and cloud cover. Halotechnics, an early-stage solar-thermal startup, could help solve both problems.
The company has developed new heat-storage materials that promise to not only make solar-thermal power plants more efficient, but also reduce the cost of storing energy from the sun for use when it’s most needed.
The materials, which include new mixtures of salts as well as new glass materials, could be key to making solar-thermal power plants cheap enough—and reliable enough—to compete with fossil fuels on a large scale.
Unlike solar panels—which convert sunlight directly into electricity—solar-thermal plants generate electricity by using a large field of mirrors to concentrate sunlight and produce high temperatures that, in turn, generate steam for a turbine and drive a generator. Such plants cost a little more than ones based on solar panels, which have recently fallen in price, but they do have one advantage: it’s easier and far cheaper to store heat produced by the mirrors in a concentrated solar plant than to store electricity from solar panels. Some solar-thermal power plants are equipped with heat-storage equipment that allows them to generate steam even after the sun goes down.
Halotechnics, a spin-off from the high-throughput chemicals screening company Symyx (now a part of Accelrys), is funded almost entirely by government grants, for a total of $6 million so far. It is currently raising its first round of venture capital.
By releasing this heat at night, plants can continue operation at maximum efficiency long after the sun has gone down.
The new salt and glass materials, which Halotechnics discovered by using a high-throughput screening process to sort through nearly 18,000 mixtures, could reduce the cost of solar-thermal power in several ways. They allow solar-thermal plants to operate at higher temperatures, thus improving their efficiency and reducing the size of the mirror array needed by up to about 25 percent. The materials store up to three times more energy than heat storage materials used now, reducing the cost of the storage system, and potentially increasing the number of thermal plants that can be equipped with storage (although the trend is to move toward storage even with existing materials). Better energy storage can reduce the cost per kilowatt-hour of the electricity produced by a solar-thermal plant, because the turbines and generators can produce power day and night.
The materials could help lower the cost for solar power to six cents per kilowatt-hour, the goal of the U.S. Department of Energy’s SunShot Initiative. “To hit that six-cent goal, or get close to it, you have to go to a higher-temperature system,” says Mark Mehos, manager of the National Renewable Energy Laboratory’s Concentrated Solar Power program, in Golden, Colorado.
“The systems that are commercial today are limited to about 565 °C—that’s the molten salt tower plants,” says Mehos. “The tower and optics themselves can hit higher temperatures, but you’re limited by the salt temperature right now.” The new materials can work at temperatures up to 1,200 °C.
Improving the reliability of solar power will also be key to making solar power competitive with fossil fuels. Without storage, the amount of solar power that can be installed on the grid is limited, since utilities need to provide backup generation, or build extra transmission lines, to deliver power from other areas when solar power output drops. So far this isn’t a problem, since solar power accounts for only a small part of the power on the grid. But it could be a serious issue within the decade in places such as California, where renewable energy requirements are leading utilities to install large amounts of solar power. Continue reading more…
