Controlling the flow of electricity to stabilize the grid
Powerful electronics: The smart transformer can handle AC and DC power and, thanks to semiconductors capable of handling high voltages, be programmed to redirect the flow of electricity in response to fluctuations in supply and demand.
A. High-voltage semiconductor-based AC rectifier.
B. High-voltage semiconductor-based DC converter.
C. High-frequency transformers.
D. Control circuitry. Credit: Bryan Regan
In a lab wired up to simulate a residential neighborhood, Alex Huang is working to revamp aging power grids into something more like the Internet—a network that might direct energy not just from centralized power stations to consumers but from any source to any destination, by whatever route makes the most sense. To that end, Huang, a professor of electrical engineering at North Carolina State University, is reinventing the transformers that currently reduce the voltage of the electricity distributed to neighborhoods so that it's suitable for use in homes and offices.
His new transformer will make it easier for the grid to cope with things it was never designed for, like charging large numbers of electric vehicles and tapping surplus electricity from residential solar panels. Smart meters in homes and offices can help by providing fine-grained information about the flow of electricity, but precise control over that flow is needed too. Not only would this stabilize the grid, but it would better balance supply and demand, reducing spikes so that fewer power plants would be needed to guarantee the electricity supply.
"We need a radically new device to sit between homes and grid to provide a buffer, so that the grid will remain stable no matter what is going on in the homes," Huang says. Conventional transformers handle only AC power and require manual adjustment or bulky electromechanical switches to redirect energy. What he wants is a compact transformer that can handle DC as well as AC and can be electronically controlled so that it will respond almost instantaneously to fluctuations in supply and demand. If one neighbor plugged an electric car into an AC charger, for example, it could respond by tapping otherwise unneeded DC power from another neighbor's solar panels.
To build such a transformer, Huang started developing transistors and other semiconductor-based devices that can handle thousands of volts, founding the Future Renewable Electric Energy Delivery and Management Systems Center at NC State in 2008. His first transformer had silicon-based components, but silicon is too unreliable for large-scale use at high voltages. So Huang has pioneered the development of transformers with semiconductors based on compounds of silicon and carbon or gallium and nitrogen, which are more reliable in high-power applications. He expects to have a test version of the silicon-carbon transformer ready in two years and to have a device that utilities can test in five years.
Huang's transformers would make connecting a solar panel or electric car to the grid as simple as connecting a digital camera or printer to a computer. That would reduce our reliance on fossil fuels by making it easier for small-scale sources of cleaner energy to contribute to the grid. He says, "The real benefit to society will come when there's an aggregate effect from many, many small generators, which we hope will be renewable and sustainable energy sources."