What is a Microgrid?
A microgrid is an approach to electrical distribution that allows local users more control over the optimization of power sources and uses. Technically, it is a grouping of small, independent power-generating equipment connected to computer systems that monitor, control and balance energy demand, supply and storage in response to changing energy needs.
Microgrids produce electricity locally, have discrete electrical boundaries and provide a single point of connection to the larger utility grid. One of the distinguishing features of a microgrid is the ability to disconnect from the utility grid (called “islanding”) to provide autonomous power in response to demand needs or external events, such as power outages or other emergencies.
Typically, one or more conventional generation assets comprise the core of the microgrid, such as a diesel generator, and other distributed power systems may produce electricity from renewable or nonrenewable sources, such as solar photovoltiac or fuel cell systems.
By balancing local energy demand with electricity generated and stored on-site, a microgrid can produce secure, reliable and affordable energy for entire communities or for commercial, industrial and government facilities.
Benefits of a Microgrid
- Increases power reliability and self-sufficiency
- Reduces utility costs and improves economic competitiveness
- Reduces greenhouse gas emissions and other pollutants
- Lower transmission and distribution efficiency losses
- Capable of operating on renewable or nonrenewable resources
- Suite of proven, commercially available technologies for various applications
- Financial incentives available through feed-in tariffs, Self-Generation Incentive Program and investment tax credits
Microgrids in California
Notable microgrid installations in California include university campuses, military bases, jails and small communities.
University of California, San Diego
- 42-megawatt microgrid
- Provides 92% of campus annual energy loads and 95% of heating and cooling loads
- Includes a combined heat and power (CHP) facility, fuel cells, rooftop solar PV electricity and concentrating PV technologies
- Advanced storage system awarded $3 million in SGIP incentive funding
Borrego Springs Microgrid
- Connects a community of 3,500 to the local utility grid
- Solar PV, microturbines, plug-in hybrid electric vehicles (PHEVs) and a wide array of battery storage
Santa Rita Jail Microgid (Alameda County)
- Nearly 3 megawatt
- Wind, solar PV, solar thermal and fuel cell cogeneration with advanced energy storage
Twentynine Palms Marine Base
- 13-megawatt microgrid
- Solar PV, combined heat and power (CHP) facility and an advanced energy storage system
- In “island” mode provides one-third of the base's total load
- Meets stringent Department of Defense cyber security criteria
The Secretary of the Navy’s energy goal of 50% energy use by alternative resources by 2020 has also prompted microgrid development in bases throughout the state.
Technologies Eligible for the Self-Generation Incentive Program (SGIP)
- Internal combustion engine
- Gas turbine
- Pressure reduction turbine
- Fuel cell
- Waste heat to power
- Advanced energy storage
- Organic Rankine cycle turbine*
- Steam turbine*
*Organic Rankine cycle and steam turbines only in waste heat to power applications
The fuel used to generate power in an internal combustion engine, microturbine, gas turbine or fuel cell may come from a variety of renewable and nonrenewable sources such as natural gas, propane, waste gas or biogas (gas derived from the breakdown of organic matter). Combined heat and power (CHP) systems that utilize biogas are eligible for increased incentives through the SGIP.