Microgrids

Microgrids are localized grids that can operate independently, thereby improving the resiliency of an isolated area. Microgrids allow for continuous operation amid grid disturbance. And because they are autonomous and intelligent, they can be useful in the integration of distributed energy resources, such as solar.

A microgrid is a self-contained power system confined to a small geographic area. It can have one or more generating sources, such as a gas generator and/or a solar photovoltaic solar array—usually relatively small in size. It might also have some means to store energy, such as batteries or thermal storage. The microgrid will serve one or more nearby buildings through wires and pipes connecting them. The whole system communicates and operates by way of intelligent control systems so that the amount of energy needed and the amount of energy being produced are always balanced, a requirement for reliable electric service and good power quality.

Our current electric grid is extremely large—but also vulnerable, which is never more apparent than when it breaks. Recent examples of include an Atlanta airport outage resulting in over a thousand cancelled flights, a rash of recent hurricanes with millions of people without power and massive storms like Superstorm Sandy, where some people lost power up to two weeks.

Staying On

One benefit of microgrids is that they are localized, allowing areas within the larger grid to remain energized when crises happen on a larger level. They are attractive to certain types of businesses or organizations with requirements for reliable power that go beyond what a local utility can provide. These needs can be driven by financial or security concerns, or by the need to serve the public good. Some examples include:

  • Critical facilities like hospitals, emergency shelters, police stations and grocery stores, which most need electricity during times of crisis
  • Businesses for which loss of power can create massive losses to products and profits, such as data centers
  • Campuses such as military bases, universities and corporate environs that need resiliency and energy surety to protect key military, intellectual or business assets
  • Remote areas with low electric reliability where microgrids are the best economic option

Currently, TVA is working with the Electric Power Research Institute (EPRI) to perform a microgrid feasibility study at a site in Knoxville, Tenn. Results from this study will provide insights into the technical and economic aspects of microgrids, including the costs of microgrids, what components (such as generators and storage) would make an optimized microgrid, and risk comparisons between operating a microgrid versus purchasing power from the grid.

This is a first, and will help TVA to better understand how microgrids can provide value, what their economic and technical feasibility truly is, and where they might best be used in the Tennessee Valley. It will also guide TVA’s strategic approach as it moves forward with multiple research partners to better understand the science behind, proper environment for and long-term value of microgrids.