GE is developing compact "large" turbines as part of a system designed to more efficiently store and deliver energy from thermal solar power plants.

Typically, such plants concentrate solar rays with vast fields of mirrors and use the heat to generate steam that spins a turbine. GE's technology involves storage of some of the heat generated by such plants in carbon dioxide, which can work like a battery to quickly release energy during peak demand.

The system design has two primary parts. In the first part, heat energy is collected from the sun and stored in a liquid of molten salt. In the second, surplus electricity from the grid is used to cool a pool of liquid CO2 so that it becomes dry ice.

During power generation, the salt releases the heat to expand the cold CO2 into a supercritical fluid, a state of matter in which it no longer has specific liquid and gas phases. That allows engineers to make the system more efficient.

The supercritical fluid is designed to flow into a compact CO2 turbine called a "sunrotor," which is based on a GE steam turbine design. Although the turbine can fit on an office shelf, it can generate as much as 100 megawatts (MW) of “fast electricity” per installed unit—enough to power 100,000 U.S. homes (pictured is a 10 MW model).

GE steam turbine specialist Doug Hofer holds a 10 MW sunrotor. Image credit: GE Global Research.GE engineers believe that large-scale deployment of the design would be able to store significant amounts of power and deliver it back to the grid when needed. “We’re not talking about three car batteries here,” says Stephen Sanborn, senior engineer and principal investigator at GE Global Research. “The result is a high-efficiency, high-performance renewable energy system that will reduce the use of fossil fuels for power generation.”

He says the system could be easily connected to a solar power system (or a typical gas turbine). The tanks and generators could fit on trailers.

The process is also highly efficient, Sanborn says, yielding as much as 68% of the stored energy back to the grid. By comparison, the most efficient gas power plants yield 61%.