Renewable energy is the way forward if tackling global warming and averting the fast-approaching energy crisis is high on every nation's list of priorities. While progress is being made in harnessing the power of the sun and the solar energy market is expected to add between 265GW and 568GWth of cumulative capacity by 2020, coal-powered thermal plants still fuel 41 percent of the world with some nations relying extensively on the fuel source.
These plants release large amounts of CO2 into the atmosphere, and while steps are being taken to reduce CO2 emissions and capture and store the gas, the big question is what to do with it.
Fortunately, GE has an answer. The biggest drawback of solar energy is that it's entirely dependent on the availability of sunlight. If the sun is down, then you've got no power and when the sun is up, there's a surplus of energy that is difficult to store.
"That's the grand challenge," says Stephen Sanborn, senior engineer and principal investigator at GE Global Research (GRC). "We need to make renewable energy available to the grid when it is needed."
Sanborn and his team are tackling this problem by storing the heat generated by solar thermal plants in CO2. Solar thermal plans work by reflecting sunlight with a vast array of mirrors. The heat from the sun is then used to produce steam, which spins a turbine, thus generating electricity.
In the innovative new process developed by Sanborn and his team, the CO2 is used like a battery to quickly release energy when required.
The system functions in two parts, one in which heat is collected from the sun and stored in molten salt. In the other, some of the surplus electricity is used to cool a pool of liquid CO2 and turn it into dry ice. The molten salt is used to heat the solid CO2 to create a supercritical fluid â€” a state where CO2 will present the characteristics of both a gas as well as a liquid â€” which will then power an innovative turbine called a sunrotor.
Based on GE's gas turbines, the sunrotor has the potential to generate 100MW of power, enough to power 1,00,000 homes. According to Sanborn, the entire system is compact enough to be placed on the back of a truck and he hopes to bring the costs down to $100 per megawatt-hour of energy produced from the current $250.
According to GE Reports, GE is currently looking at commercial applications of the system â€” a product of a research partnership between GRC and U.S. Department of Energy â€” although the irony is that CO2 is the major cause of global warming and climate change, which is why the world is turning to renewable sources of energy in the first place.