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Microgrids


A microgrid is an interconnected set of electricity sources and loads that falls under a common method of control.

Description of microgrid technologies

Because the electric grid must constantly remain in a balanced state where sources and loads are roughly equal, a microgrid is a means by which the grid is segmented to reduce the size of that balancing area. A microgrid can be as small as a single building (a net-zero building, for instance), but most are campus-sized operations. The University of California, San Diego, is an example of a college campus that has implemented a microgrid.

Microgrids are most commonly associated with the integration of small-scale renewable generation like rooftop solar (photovoltaic or PV) panels. While microgrids with renewables is new, microgrids are old. Going back to World War

II, military field hospitals and forward operating bases represented microgrids that burned fossil fuels to run generators. Modern data centers have a similar capability, coupling local generation with energy storage capabilities that allows them to operate even when the surrounding grid is out of service. This is also referred to as “islanding” capability.

Microgrid’s role in outage prevention and service restoration

Microgrids are natural delineations where the grid can be segmented during outages. This not only holds true for traditional causes of outages like weather-related events, but also for emerging threats, such as cybersecurity. During a widespread attack, islanding and microgrid capabilities would insulate consumers from potential outages. Additionally, microgrids also offer benefits to grid operators. In a 2002 paper1, Professor Robert Lasseter of the University of Wisconsin described how microgrids could be “model citizens” of the grid by providing interruptible loads. This capability is key to grid operators on “peak of the peak” days when the potential for brownouts is at its greatest.

Illustration

The March 2011 earthquake and subsequent tsunami were devastating events in Japan. As IEEE reported in Spectrum magazine in October 2011:

“...The bustling port city of Sendai was directly in harm’s way...but in one small section of the city, the lights stayed on. At Tohoku Fukushi University, in the northwest part of town, the laboratories’ servers kept on humming, the clinic’s MRI machines didn’t lose a tesla, and the hospital’s lights and equipment operated without a hitch. These facilities were the beneficiaries of an experimental microgrid project fed by three types of energy generators—fuel cells, solar panels, and natural gas microturbines. Because the project also uses the thermal exhaust from the gas turbines and fuel cells to heat the buildings, the hospital’s patients were kept warm through northern Japan’s cold March nights2.”

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1 www.pserc.wisc.edu/documents/research_documents/certs_documents/certs
_publicationscerts_microgrid/certsmicrogridwhitepaper.pdf

2 spectrum.ieee.org/energy/the-smarter-grid/a-microgrid-that-wouldnt-quit, October 26, 2011