The researchers from Massachusetts Institute of Technology (MIT) estimate that such a system would be vastly more affordable than lithium-ion batteries, that has long been considered a viable method for renewable energy storage.
MIT scientists have designed a system that could store renewable energy, such as solar and wind power, and deliver it back into an electric grid on demand. The system, described in the journal Energy and Environmental Science, may be designed to power a small city not just when the sun is up or the wind is high, but around the clock.
“Even if we wanted to run the grid on renewables right now we could not, because you’d need fossil-fuelled turbines to make up for the fact that the renewable supply cannot be dispatched on demand,” said Asegun Henry, Associate Professor at MIT. “We are developing a new technology that, if successful, would solve this most important and critical problem in energy and climate change, namely, the storage problem,” Henry said. The new storage system stems from a project in which the researchers looked for ways to increase the efficiency of a form of renewable energy known as concentrated solar power.
Unlike conventional solar plants that use solar panels to convert light directly into electricity, concentrated solar power requires vast fields of huge mirrors that concentrate sunlight onto a central tower, where the light is converted into heat that is eventually turned into electricity. “The reason that technology is interesting is, once you do this process of focusing the light to get heat, you can store heat much more cheaply than you can store electricity,” Henry said.
Instead of using fields of mirrors and a central tower to concentrate heat, they propose converting electricity generated by any renewable source, such as sunlight or wind, into thermal energy, via a process by which an electric current passes through a heating element. The system could be paired with existing renewable energy systems, such as solar cells, to capture excess electricity during the day and store it for later use.
The system would consist of a large, heavily insulated, 10-metre-wide tank made from graphite and filled with liquid silicon, kept at a “cold” temperature of almost 1927 degrees Celsius. A bank of tubes, exposed to heating elements, then connects this cold tank to a second, “hot” tank. When electricity from the town’s solar cells comes into the system, this energy is converted to heat in the heating elements.