Decade after decade, the dream of a sustainable future becomes increasingly more of a reality. Startup companies pop up all over the world, consumers invest in their products, and before long it seems like everyone is at least a little more eco-oriented. Even so, it’s clear that we’ve still got a long way to go before we can say we’ve actually achieved that goal.

Overcoming Storage Challenges at MIT

Electrical lines connecting the power grid.

Storing renewable energy has proved just as challenging, if not even more so, than creating it. Storage in lithium-ion batteries is a feasible option but prohibitively expensive. Pumped hydroelectric storage is also an alternative, but it’s still too costly to be a practical solution.

The engineers at MIT developed a theoretical concept to not only successfully store solar and wind power, but also transfer that renewable energy to an electric grid on an as-needed basis. This is a significant step forward, as it means entire communities could start relying on this energy 24/7, all year long — not just when the sun is shining or the winds is billowing.

Evolution of the “Sun in a Box”

solar panels and wind turbines

TEGS-MPV, short for Thermal Energy Grid Storage-Multi-Junction Photovoltaics, evolved from an MIT project on concentrated solar power. Instead of using solar panels to turn light straight into electricity, this technique uses gigantic fields of massive mirrors to focus sunlight on a centralized tower. The concentrated light is then turned into heat that can be converted into electricity later on. This method is immensely more economic than lithium-ion batteries and about half as costly as pumped hydro storage.

Asegun Henry, an Associate Professor in the Department of Mechanical Engineering, and his associates published their design in the Energy and Environmental Science journal. Henry commented: “Even if we wanted to run the grid on renewables right now we couldn’t, because you’d need fossil-fueled turbines to make up for the fact that the renewable supply cannot be dispatched on demand. We’re developing a new technology that, if successful, would solve this most important and critical problem in energy and climate change, namely, the storage problem.”

MIT's new "Sun in a Box" energy production system.

The project’s latest iteration trades in the tower and mirrors for two 33-foot-wide graphite tanks: one of which stores white-hot liquid silicon at a temperature of 3,450° F (1,900° C), and the other of which keeps it at a much hotter temperature of 4,350° F (2,400° C). The process begins when the gleaming white liquid is forcefully driven out of the cooler tank through a series of tubes that both heat it up (via external wind or solar power) and emanate its light. Dedicated solar cells then convert that light into electricity as the now-hotter silicon flows into the other tank. When it eventually cools back down, the liquid flows back into the first tank, where it sits until needed again. Sort of like a big rechargeable battery, in a way.

The MIT team believes a single one of their “Sun in a Box” systems could produce enough energy to power 100,000 homes. And who knows? After they’ve been put into action and all the appropriate tests have been conducted, these tanks could very well be running the entire grid.