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Distributed Energy Systems

A growing trend in the power industry is toward distributed generation. Distributed generation involves placing small, modular electricity generators close to the buildings where the power is used, which helps utilities defer or eliminate costly investments in transmission and distribution system upgrades, and provide customers with better quality, more reliable energy supplies and a cleaner environment.

Technologies used for distributed electricity generation include wind, solar, bioenergy, fuel cells, gas microturbines, hydrogen, combined heat and power, and hybrid power systems. Visit the DOE Distributed Energy Program Web site for more information.

Distributed energy refers to a variety of small, modular power-generating technologies that can be combined with load management and energy storage systems to improve the quality and/or reliability of the electricity supply. They are "distributed" because they are placed at or near the point of energy consumption, unlike traditional "centralized" systems, where electricity is generated at a remotely located, large-scale power plant and then transmitted down power lines to the consumer.

Implementing distributed energy can be as simple as installing a small, stand-alone electricity generator to provide backup power at an electricity consumer's site. Or it can be a more complex system, highly integrated with the electricity grid and consisting of electricity and thermal generation, energy storage, and energy management systems. Consumers sometimes own the small-scale, on-site power generators, or they may be owned and operated by the utility or a third party.

Distributed energy encompasses a wide range of technologies including wind turbines, solar power, fuel cells, microturbines, reciprocating engines, load reduction technologies, and battery storage systems. The effective use of grid-connected distributed energy resources can also require power electronic interfaces and communications and control devices for efficient dispatch and operation of generating units.

Diesel- and petrol-fueled reciprocating engines are one of the most common distributed energy technologies in use today, especially for standby power applications. However, they create significant pollution (in terms of both emissions and noise) relative to natural-gas- and renewable-fueled generators, and their use is actively discouraged by many municipal governments. As a result, they are subject to severe operational limitations not faced by other distributed generating technologies.

Distributed energy technologies are playing an increasingly important role in the nation's energy portfolio. They can be used to meet baseload power, peaking power, backup power, remote power, power quality, as well as cooling and heating needs.

Distributed energy also has the potential to mitigate congestion in transmission lines, reduce the impact of electricity price fluctuations, strengthen energy security, and provide greater stability to the electricity grid.

Distributed power generators are small compared with typical central-station power plants and provide unique benefits that are not available from centralized electricity generation. Many of these benefits stem from the fact that the generating units are inherently modular, which makes distributed power highly flexible. It can provide power where it is needed, when it is needed. And because they typically rely on natural gas or renewable resources, the generators can be quieter and less polluting than large power plants, which makes them suitable for on-site installation in some locations.

The use of distributed energy technologies can lead to improved efficiency and lower energy costs, particularly in combined cooling, heating and power (CHP) applications. CHP systems provide electricity along with hot water, heat for industrial processes, space heating and cooling, refrigeration, and humidity control to improve indoor air quality and comfort.

Grid-connected distributed energy resources also support and strengthen the central-station model of electricity generation, transmission, and distribution. While the central generating plant continues to provide most of the power to the grid, the distributed resources can be used to meet the peak demands of local distribution feeder lines or major customers. Computerized control systems, typically operating over telephone lines, make it possible to operate the distributed generators as dispatchable resources, generating electricity as needed.