One solution to the aging U.S. grid: microgrids

efficiency, security, and energy reliability — all of which are required from a microgrid,” NREL electrical engineer Greg Martin said.

There are two prongs to the microgrid work at NREL: innovative research and partnering with industry.

NREL works with industry to test microgrid systems by providing the experts as well as the infrastructure to support microgrid testing. The U.S. Department of Defense is also working with NREL researchers to examine using microgrids to improve base reliability. Testing includes using grid simulators, load banks, and generators, all currently at the Distributed Energy Resources Test Facility at the National Wind Technology Center near Boulder, Colorado.

“We use equipment such as a grid simulator to create a virtual electric grid to test equipment that is planned to be connected to a utility,” Martin said. “We create outages, or some other kind of electrical phenomenon, to make sure the equipment operates as expected. We basically try to make stuff work while making sure it works the way it’s supposed to.”

“Utilities need to be shown that this technology is safe to integrate into the system and won’t affect the normal operations,” NREL Energy Systems integration director Ben Kroposki said. “One of the goals at NREL is to provide that test bed for a variety of scenarios to be run so that utilities can see that the risk is being reduced.”

An example: take a 200-kilowatt microgrid in a residential area with 100 kilowatts of photovoltaics (PV) installed on homes. When all the homes are grid-connected through a local utility, those 100 kilowatts of PV are no big deal. Once the homes are disconnected from the grid, however, that is a high ratio of PV. Researchers work with industry to figure out which resources have to be maintained to keep the power reliability needed for critical loads. Key questions include, should the homes start shedding loads if a cloud crosses the sun and the PV power drops? Or is energy storage needed, so when a cloud comes, the power supply stays consistent?

NREL is leading the way in understanding issues in energy systems integration and helping industry work through them. The lab’s research tools will get a boost when the Energy Systems Integration Facility (ESIF) is completed later this year.

“ESIF is going to be like our current lab on steroids, and will expand our testing scale to 1 megawatt,” Martin said. “We’ll be able to test large single