[Editor’s note: this news post is by Frank Currie, Lead Faculty for the Distributed Energy Systems program at Santa Fe Community College (an MSL consortium Member). MSL contributed to the microgrid’s conceptual design.]
After an extensive design and development process, the “educational microgrid” at Santa Fe Community College (SFCC) – also known as the “greenhouse microgrid” and the “nanogrid” – was tested, validated, and commissioned for operation in July, 2021. The system comprises an 11,000 square-foot greenhouse, a classroom/lab building, and several distributed energy resources. As of late 2019, the greenhouse and the classroom were fed from the campus electrical distribution system and a small (12kW) PV tracking array that had been built near the greenhouse also fed into the campus distribution system.
Then in the fall of 2019, several upgrades were made that moved the greenhouse towards becoming a microgrid. One of the key enablers of the microgrid was the donation of funds by the Department of Energy’s Office of Electricity through its energy storage demonstrations team at Sandia National Labs. The donation included $100,000 to purchase and install an energy storage system and switchgear which would, among other things, install a relay and breaker which would make the greenhouse and classroom islandable. The battery system — a 100 kW/85 kWh lithium-ion system — was purchased from (the now dissolved) NEC energy storage division, and has capacity to be expanded to expanded to 170 kWh. The State of New Mexico, the U.S. Economic Development Administration, and Siemens Industry also contributed to the cost of the project.
With the installation of the switchgear, the tracking array was also connected into the greenhouse side of the circuit so that the greenhouse, classroom, energy storage system, and PV could form a simple microgrid. The commissioning of the switchgear upgrades was completed in 2019, while the commissioning of the battery was completed in July of this year. The educational microgrid will be used to support curriculum and coursework in the distributed energy systems areas at the college.
SFCC is in the process now of purchasing a back-up generator (a natural gas unit) for the greenhouse microgrid which will allow for indefinite microgrid operation (and which will also buy time for the addition of more DERs within the microgrid, most specifically, the expansion of PV and possible a wind turbine to provide a larger fraction of energy from renewables). The generator will have a controls upgrade that will allow it to be run in parallel with the other DERs in the microgrid, most notably the energy storage system, which will provide the “grid reference,” (I.e., the frequency signal that other DERs will follow). The greenhouse microgrid has been successfully operated in two modes: it has been “black started” from a no-load condition with loads then being brought online manually, and has also successfully had the battery transition from a grid-following state to its grid-forming mode with a surprisingly seamless pickup of all loads within the microgrid. The latter has been done under a variety of load conditions with no issues seen thus far.
The microgrid must, for now, be islanded and resynched manually (I.e., the main circuit breaker must be manually opened and closed) because SFCC is still waiting for the intended controls that will be part of the broader campus-wide microgrid being installed by Siemens under an energy performance contract. When completed, this will make the entire SFCC distribution system islandable from the utility grid. The greenhouse microgrid will be operated as a nested microgrid controlled by the campus microgrid controller. Although its primary function is to support greenhouse microgrid resiliency and microgrid education, SFCC will also explore options to use available DER capacity to support the larger microgrid when appropriate. Current expectations have the campus microgrid going online in 2022.