Skip to main content

NREL's ESIF Offers Equipment Testing on Grand Scale

April 16, 2015

This article is reprinted with permission from the April 14, 2015 issue of Smart Grid Today.


NREL's Energy Systems Integration Facility (ESIF) is playing a part in Hawaiian Electric's (HECO) deployment of home solar, Ben Kroposki, director of power systems engineering at NREL, told us last week. Solar City, the solar designer, financier and installer of solar PV, is deploying rooftop PV solar for HECO across much of Hawaii, Kroposki said.

HECO last summer issued a moratorium on all new PV installations until it could get a better handle on understanding the characteristics of solar PV inverters being installed (SGT, Jan-27).

"Within a couple of months, we were able to define the parameters around how the inverters were working, so that they could lift the moratorium," Kroposki said, noting the Golden, Colo-based research center "is the only one in the US that can conduct integrated, utility-scale testing and evaluation of the components and strategies needed to safely integrate clean energy technologies into the electricity grid."

That service is paid for by DOE and the lab's clients, with the former paying "for all of the costs of facility operation and research setup," while the "clients pay for the time it takes to run the experiment," he added.

ESIF worked with SolarCity on "a combination of smart inverter and smart grid technologies, conducting investigations into how solar inverters can be programmed and controlled to trip on and off in response to grid voltage fluctuations, or to perform other grid balancing tasks," Kroposki said. That research represented one of the first attempts to aggregate control of smart inverters in the US, he added.

Other ground-breaking research on behind-the-meter power storage and bidirectional power flow is in process with HECO now, Kroposki said.

HECO is facing an explosion in home PV systems and with it, solar-integration lessons useful for grids in the rest of the US, Smart Grid Today reported recently in a report titled "Growing Pains: Taking on the most urgent challenges of renewables."

To run and test smart grid hardware on a plug-and-play basis, ESIF "set up infrastructure that allows us to take, for example, PV inverters and plug them into either alternating current or direct current buses to replicate the grid (AC) and the home (DC)," he added. Solar City sent ESIF about 30 inverters and that let it "take inverters from 3-KWs (residential) to 1-MW (utility-scale) and across the full range, plug them in and conduct investigations in a streamlined manner."

The "research electrical distribution bus" (REDB) is a specialized ESIF network capable of connecting multiple sources of energy and interconnecting labs and experiments to test and simulate equipment. At the research center, the REDB is what connects power electronics, MW-scale grid simulators, electrical load banks, smart grid technology assessment capabilities and power electronic inverters and converters, Kroposki said.

Integrated throughout the ESIF, the distribution bus is tied into a SCADA platform that centrally collects, displays and stores information from all ESIF labs. It also connects to outside test beds such as microgrids, he added.

QUOTABLE: We set up a microgrid being built by the defense contractor Raytheon for eventual deployment at the Marine Corps Air Station Miramar in San Diego. This was a first-of-its-kind microgrid that included PV energy storage. Before Raytheon deployed it out in the field, they sent the entire system to us and we ran it through its paces, including a wide range of operating parameters. Raytheon was extremely happy with this because we found some bugs in their control logic that we were able to fix before real-world deployment. - Ben Kroposki, director of NREL's Energy Systems Integration Facility (ESIF) in an exclusive interview

ESIF is studying energy storage, too, looking at "several different scales of storage" - starting with small, residential-size lithium-ion-based storage units and up to community energy storage using lead-acid battery systems and some selenium redox flow batteries, he added.

ESIF is testing an American Vanadium flow battery, Kroposki said. "In addition, we recently received and are ready to do some tests on a 300-KV battery system" that is part of a Dept of Defense project.

DOE built ESIF for $135 million in 2012 and the 185,000-square-foot complex houses 200 scientists and engineers, 14 labs, several outdoor test beds and Peregrine, one of the world's most powerful supercomputers.

Kroposki has been at the helm of ESIF since January. He took part in its planning over the last five years, to establish "a place where we could build complete energy systems at the scale at which they eventually would be deployed," he noted. "The good news is that now, we are fully up and running with over 45 external partnerships with industry and universities along with DOE research in our lab space."

Remote testing coming

For the most part, ESIF does its testing at its facility. "We are doing on-site assessments because we have very unique hardware testing capabilities," Kroposki said.

"We are working now on connecting to simulations and software at a different location. We have been working with the DOE's Pacific Northwest National Laboratory (PNNL) in Richland, Wash, to run distribution circuit models at their facility. They don't really have the hardware testing abilities that we do.

"We connect virtually through the internet to assess how hardware - those same inverters, just to keep it simple - would perform in a variety of distribution systems. PNNL can actually replace their simulation quickly on their side - from rural to urban environments - to see how real hardware interacts with those different types of circuits," he added.

"We also are working on remote testing with Idaho National Laboratory in the US and with the Commonwealth Scientific & Industrial Research Organisation [sic] (CSIRO) in Australia. Australia is really the farthest we could go to be able to connect and run a virtual experiment," Kroposki said.

Cybersecurity considered

ESIF considered the security implications of hooking up laboratory experiments. "There is definitely a cybersecurity issue," Kroposki said, "but we take care of that. We basically make our own virtual private network (VPN) between the two locations."

The facility has a broader cybersecurity program, too. "With the proliferation of new technologies at the grid edge/distribution edge - from solar systems to electric vehicles to learning thermostats - we are seeing a huge amount of potential access points to the grid that never were there before," he added.

ESIF recently hired EPRI's Erfan Ibrahim (SGT, 2009-April-9) as its director for cybersecurity and resilience, Kroposki said. Ibrahim has experience leading security efforts out of the EPRI, and "we are expecting him and his team to come up with some exciting ideas."

© 2015 Modern Markets Intelligence, Inc. IMPORTANT: This article was reproduced from the April 14, 2015 issue of Smart Grid Today with the limited permission of the owner. To view the full story on Smart Grid Today's website, please visit