GE has announced it is working on a way to use CO2 pollution to make new types of solar batteries that could each power up to 100,000 homes. CO2 is the main contributor to climate change, and is released into the atmosphere when coal is processed at power plants. Currently environmental procedures mean that some CO2 from these plants is captured and stored, so it’s not released back into the atmosphere. But the question has always been: What do you do with the stored gas?
Now GE says it’s figured out a way to put that stored CO2 to use by using it as a giant battery that could store excess solar energy. The technique would also resolve another long-standing energy problem: how to store solar energy so you can use it when needed most—at nights or on cloudy days. “That’s the grand challenge,” according to Stephen Sanborn, senior engineer at GE Global Research. “We need to make renewable energy available to the grid when it is needed.”
Sanborn’s solution works in two parts. The first collects solar energy and stores it in a liquid of molten salt. The second part uses surplus electricity from the power grid to cool liquid CO2 so it becomes dry ice. During power generation, the molten salt transforms the dry ice CO2 into a “supercritical” fluid, that is a state of matter that neither has specific liquid nor gas phases. That supercritical fluid then flows into a CO2 turbine called the sunrotor. It is the sunrotor that can then dole out the stored solar energy as needed. Sanborn’s team has created a version of the sunrotor that is small enough to fit on an office shelf, yet power 100,000 homes.
Sanborn says the sunrotor could bring the cost of energy down from $250 per megawatt-hour to $100 per megawatt-hour. “It is so cheap because you are not making the energy, you are taking the energy from the sun or the turbine exhaust, storing it and transferring it,” he says. Once deployed sunrotors could yield as much as 68% of stored energy back to the power grid. Even the most efficient gas power plants currently only yield 61% of energy back to the grid. As for the timeline of deployment, Sanborn says sunrotors could see widespread use within 5 to 10 years.
“The result is a high-efficiency, high-performance renewable energy system that will reduce the use of fossil fuels for power generation,” Sanborn says.