A team of researchers from the Massachusetts Institute of Technology has figured out a way to deliver low cost solar energy at night as well as during the day, by combining a concentrated solar power system with a molten salt heat storage system. Concentrated solar and salt storage are two familiar technologies and this would not be the first attempt to merge the two. However, the MIT team is focusing their system on bringing down installation, operating and maintenance costs. If the concept proves workable, it could help small towns and communities take themselves off the grid with a reliable, steady stream of clean energy.
Concentrated Solar Power and Molten Salt Storage
Concentrated solar power basically means using mirrors to focus sunlight on a central tower. When combined with molten salt in the conventional manner, the idea is to heat the salt with solar energy, then transfer the energy to water, which generates steam that turns a turbine to produce electricity. However, without a storage element this arrangement does not provide a steady stream of energy, and it requires pumps and piping that can be expensive to install and operate.
A Low-Cost Solar-Salt Combo
The MIT team resolved the cost problem with a ground-mounted tank instead of a tower. The low-rise system eliminates a significant amount of plumbing and related equipment, and it would be less expensive to install and maintain over the long run. Rather than positioning mirrors to focus sunlight upwards to a tower, the mirrors would be positioned on a hillside above the tank, and focus sunlight downwards to a narrow opening at the top of the tank, achieving temperatures of more than 500 degrees Celsius. The tank would double as storage by use of a floating barrier that adjusts itself during daylight hours to keep the heated salt separate from cold salt.
Solar Power as Cheap as Fossil Fuels
Earlier this year the Obama administration announced the SunShot initiative, designed to promote new technologies that bring the cost of solar energy down to a competitive level with fossil fuels. In a best case scenario, the MIT team estimates that the cost of their “Concentrated Solar Power on Demand” system would be about seven cents per kilowatt hour. Small-scale tests have already been conducted using sodium-potassium nitrate salt and the next step is to build larger demo facilities, potentially at sites in New Mexico or California.
Image: The moon by dingopup on flickr.com.
Tina Casey specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. You can also follow her on Twitter @TinaMCasey and Google+.