Enabling distributed generation

 

THERE'S AN OLD ADAGE THAT CAUTIONS there's no point reinventing the wheel.

Oftimes, it's true, but every once in a while, taking a step back and looking at potential new uses for that old yet favorite shirt-or wheels-has its advantages.

So it is with the concept of distributed generation, and distributed energy resources.

A history and a legacy

Back in 2006, in a paper titled "Installing distributed generation into electric power systems: A review of drivers, challenges and opportunities," J. A. Pecas Lopes et al. wrote: "It is now more than a decade since distributed generation began to excite major interest amongst electric power system planners and operators, energy policy makers and regulators as well as developers."

But it actually reaches much further into the past than that. A February 2007 study by the U.S. Department of Energy entitled "The Potential Benefits of Distributed Generation and Rate-Related Issues that May Impede Their Expansion," notes:

"Distributed generation is not a new phenomenon. Prior to the advent of alternating current and large-scale steam turbines-during the initial phase of the electric power industry in the early 20th century-all energy requirements, including heating, cooling, lighting and motive power were supplied at or near their point of use."

Energy storage and responsive loads

It is the concept of distributed energy resources, rather than that of distributed generation alone, which is most exciting today. Distributed energy resources (DER) include not only distributed generation, but also energy storage and responsive loads.

Microgridding, too, becomes part of the mix. A 2009 Pike Research analysis of microgrids indicated that, although microgrids "offer a compelling alternative to traditional energy generation and distribution, utilizing smart grid technologies to enable integrated control of distributed power generation assets either in parallel to or `islanded' from the utility power grid," there are still few commercialized, state-of-the-art microgrids with significant generation capacity actually up and running in North America.

The same can be said for energy storage, though that may be changing in the coming year. In late October, the Federal Energy Regulatory Commission (FERC) issued a final rule designed to justly compensate energy and storage-based resources that provide certain key reliability services on the electric grid.

Order No. 755, on frequency regulation compensation in the organized wholesale markets, noted in part: "Commenters cite several studies to support the argument that faster-responding resources will result in economic benefits. Among them is PNNL's study showing that fast-ramping energy storage devices (such as flywheels and batteries) could be as much as 17 times more effective than conventional ramp-limited regulation resources because of how quickly and accurately they respond to a system imbalance; and a California Energy Commission study which shows that, `on an incremental basis, storage can be up to two to three times as effective as adding a combustion turbine to the system for regulation purposes.'"

Implementing energy storage

This past summer, American Electric Power (AEP) became the first electric utility in the U.S. to deploy a community energy storage (CES) system in its service territory. Termed "a watershed in the history of grid-connected electricity storage in the United States" by James Greenberger, executive director of the National Alliance for Advanced Technology Batteries, the AEP CES system consists of 80 25-kW units, installed in a residential neighborhood in Columbus, Ohio.

Greenberger feels that many industry experts are coming to the view that CES will be the "killer app" in grid-connected energy storage, as CES has a number of unique advantages. "Because CES systems are located immediately proximate to the ultimate customers, they can provide backup power, level peak loads and reduce the strain on, and necessary investment in, the complicated and often unsightly infrastructure needed to distribute centralized electric power," he said.

As well, CES systems can be networked to provide transmission support and leveling of variable renewable energy generators, and can "facilitate the deployment and rational net metering of distributed solar and wind electricity generation and support the recharging of electric vehicles on demand," he added.

Microgrids on the rise?

While the town board of Lewisboro, NY, said "no" to a microgridding plan-in fact, the board refused to even hear the proposal-brought forward by a private entrepreneur back in 2009, U.S. military bases, college campuses and utilities themselves are moving forward with pilot projects and research designed to prove microgrids as a boon to system reliability.

San Diego Gas & Electric's Borrego Springs project is one example. In another, AEP's hosting, for more than a decade, of the Consortium for Electric Reliability Solutions (CERTS) test site has allowed for key breakthroughs in potential microgrid commercialization. And the Sacramento Municipal Utility District (SMUD) is now taking the CERTS research out of the laboratory and into the real world.

SMUD's headquarters-based microgrid will include three 100 kW CHP combined-heat-and-power natural gas-fired generators, 10-kW of solar PV panels, and a 500-kW battery for storage purposes. It is meant to further test, monitor and potentially refine the electrical integration of micro-generation systems with the larger utility electrical supply systems and other small power sources such as photovoltaic or fuel cells. SMUD expects to operate the facility for a decade or more.

Brave new world?

According to Pecas Lopes, the power system architecture is bound for change. "The power system architecture of the future, incorporating DER, will look very different from that of today," he and his colleagues wrote. "Whilst the pace of change is likely to be evolutionary, the change itself is expected to be nothing short of a revolution as many traditionally held views and approaches to system operation and planning developed over the past 100 years are challenged and transformed to suit the requirements envisaged in the brave new world of the future."