Electric utilities face a special problem in a world is constantly changing. To function best, they don’t just have to respond properly to changes that happen, they have to anticipate and be properly prepared for them. As part of that work, they periodically produce Integrated Resource Plans (IRPs) detailing what they are preparing to do for the future.
Green Mountain Power (GMP) files an IRP every third year with the Vermont Public Utilities Commission. The most recent was filed in late 2021 (www.bit.ly/GMP-IRP-2021). The plan provides details on how GMP expects to address climate change, increase reliability and resiliency, and provide its customers with cost-effective carbon-free, renewable power. Part of the plan shows that GMP will increase the numbers of microgrids in the state. It will also build up a two-way sharing system, generate more renewable electricity closer to where it is used, and increase the electric vehicle charging system.
A microgrid can continue to operate when the broader grid fails. It does this by including the generating and electric storage capacities along with the loads they will provide for, along with the electronics needed to “island” it, detaching it from the rest of the grid. In theory, a microgrid could operate entirely in the absence of the broader grid for an indefinite time, though there are benefits for both when they operate together.
Microgrids are not new. They have been around for a long time. In the past, they were often built around diesel generators that could start up in the event of grid failure, keeping disturbances down to a minimum. Hospitals often operate this way.
Modern microgrids are usually built around renewable energy resources. They are often designed so as to provide power for such things as emergency shelters in a community, along with fire stations, pharmacies, and food stores in their loads. The generating capacity is specified so as to be sufficient for the load nearly all the time, though many microgrids have additional backup capacity such as diesel engines.
GMP’s IRP describes a move toward distributed generation in microgrids that will be undertaken in “hyper local planning.” This will use technological innovations to “drastically improve” local resiliency by use of the microgrids. And with sufficient resiliency, a community can continue to function separately, when that is necessary.
GMP will begin by building a small group of the microgrids. One microgrid, in Panton, VT was commissioned in October of 2021 and already serves 51 customers. Its electricity is generated in an one megawatt (MW) solar array backed up by four megawatt hours (MWh) of battery storage.
Rochester is to have a microgrid in an area along Route 100. The area includes the town water pumps and an emergency shelter at an elementary school.
In Strafford, a microgrid will be in the downtown area. It will serve emergency shelters at the Newton School, Rosa Gym, and Barrett Hall, in addition to the general store and post office. It will get power from a solar project owned by the town and a 7-MW solar installation at the former Elizabeth Mine superfund site.
Two other microgrid sites are smaller. One is in a small part of Grafton, which will have solar power and storage integrated with the larger grid, but to continue operations when the larger grid is down. The other one is a cooperative housing community in Brattleboro that is vulnerable to flooding.
Along with these, there will be two other communities chosen for microgrids, though the decision as to which they will be has not yet been announced.
The microgrids being established by GMP are first steps toward a more distributed and resilient future. In it, local demand will be met, as much as possible, by local supply. And this implies local jobs and a more robust local economy in Vermont.