Microgrids promise reliable, efficient, environmentally-friendly electricity in a ‘peer-to-peer’ network:
In 1996, a sagging power line in Oregon brushed against a tree, and within minutes 12 million customers in eight states lost power supply. Such is the vulnerability of today’s power grid. To address this, Berkeley Lab research scientists developed a cluster of small, on-site power generators serving offices, industry, homes.
The system designed to shoulder the US growing thirst for electricity without building the 1,000 new power plants required to meet demand, will lead to a revolution in the way we can live green.
Microgrids, the concept of transforming the electricity network from a single, central network to small, localised clusters, offer far more reliable and environmentally friendly power supplies claim Dr Tomas Markvart of Southampton University and Professor Ray Arnold of Siemens, in Ingenia, the magazine of the Royal Academy of Engineering.
MARKET REPORT: Small-Scale Power Generation: U.S. Markets and the Emerging Microgrid – buy it from Amazon for $4,313 – key conclusions:
THE overall U.S. small-scale power market will rise at an average annual growth rate (AAGR) of 16.6%, from $2.8 billion in 2003 to $6.1 billion in 2008.
RECIPROCATING engines and wind turbines will continue to comprise the majority of sales, 54% and 33.5%, respectively, but are ceding market share to high-efficiency gas engines and alternative energy technologies.
OUTPUT of the U.S. small-scale power market is expected to double in five years, growing at an AAGR of 15.1% to 10,109 megawatts in 2008.
THE capacity of the average reciprocating engine will increase as utilities expand their investments in distributed, backup power.
SOLAR and wind turbines will exhibit strong output growth reflecting reduced costs from improved engineering, materials and manufacturing processes.
Also known as ‘distributed energy’ or ‘distributed generation’, microgrids mirror the structure of early electricity distribution. In those days, hundreds of unregulated companies managed generators that each provided power to a tiny region. Controlling supply and demand with these systems was impossible, and small generators were hopelessly inefficient, leading to a gradual transformation into a single national authority, and a few gigantic stations.
According to the report, the “evolution of energy technologies and the consequent awareness of the environmental impacts that this can bring” has reshaped what we should be looking for. This new version of distributed energy is to have a large number of household generators connected into a low voltage local network, on the same scale as a housing estate.
Sophisticated computer systems could be used to regulate the system, exporting and importing power to larger networks only occasionally. The analogy is that of a peer-to
peer file-sharing network, where small numbers of users both contribute and benefit from the service on offer.
The advantages are:
A smaller network would find it easier to integrate electrical storage systems due to reduced size requirements. It would work better with environmentally friendly generator technologies like renewables, or micro-CHPs – combined generator/boilers which use waste heat to produce hot water. Their small power output would still be useful locally, and these generators’ efficiencies are often not dependent on their size. It would reduce the volatility of supply because failures would only affect a single isolatable network. It would cut waste during transmission, because the majority of power would only be transported a short distance, without a need for transformer stations to change voltages.
According to the report, efficiency is expected to soar to around 80%, compared to the 35-40% figure of today. Prototype microgrids are already being designed and tested. In Germany’s Nordheim-Westfalen, a training academy uses a small network containing a battery, a photovoltaic array, and a CHP system. In the US, the Consortium for Electric Reliability Technology Solutions developed a first-of-its-kind microgrid to serve Northern Power and its nearby corporate neighbourhood. “Catastrophic loss of power to all systems like the 1996 blackout should be impossible,” says Chris Marnay, an energy scientist in Berkeley Lab’s Environmental Energy Technologies Division. “If we sat down today to devise a power system from scratch, our design wouldn’t resemble the one we have.” Instead of relying solely on large power plants, a portion of the nation’s electricity needs could be met by small generators such as ordinary reciprocating engines, microturbines, fuel cells, and photovoltaic systems. A small network of these generators, each of which typically produce no more than 500 kilowatts, would provide reliable power to anything from a postal sorting facility to a neighborhood.
The microgrid appears to the larger grid as if it’s any other customer. And it can quickly switch between operating on and off the grid: when the grid offers cheap electricity, the microgrid can purchase it, but if prices rise or there’s a power failure, the microgrid can isolate itself. It can also temporarily shed unimportant equipment such as refrigerators during power shortages. This ensures uninterrupted power to the critical computers, communications infrastructure, and control systems that drive today’s economy.” Everything is interdependent. For example, if vital communications go down, other sectors falter,” Marnay says. “But if sensitive equipment is powered locally, our vulnerable, centralized power system becomes much less critical, and is a less attractive terrorist target.”
Microgrids boast other advantages, but it’s no coincidence reliability is high on the list. The concept is being pioneered by the Consortium for Electric Reliability Technology Solutions, a national lab, university, and industry group convened by the Department of Energy in 1999 to explore ways to improve power reliability. The consortium, which is supported by the California Energy Commission and centered at Berkeley Lab, is developing several strategies in addition to microgrids, including managing power grids in real time and determining how an emerging open electricity market affects reliability.
The group will also conduct the first microgrid bench test in early 2004, in which three microturbines and several end loads will be linked together at a utility-grade testing facility.
Chris Marnay and colleagues are also developing a computer model that predicts who is most likely to adopt a microgrid, and why. Their work underscores the fact that air quality regulatory restrictions, building code constraints, and site limitations mean some microgrids will be able to use only clean, quiet generators such as fuel cells, instead of more common, gas-fueled reciprocating engines. Despite such hurdles, a microgrid’s many advantages will likely win fans. First, between 60 and 80 percent of the energy consumed by power plants isn’t converted to electricity. It escapes as heat, which, unlike electricity, is neither transportable nor easy to use locally. But with a microgrid, waste heat could feed a small, adjacent heat load such as a water heater.
“We’d place power generation where heat is needed, rather than where we can conveniently discard it,” Marnay says.Recovered waste heat could also cool and dehumidify buildings, using thermally activated processes. This is doubly advantageous. Cooling buildings places tremendous strain on the power grid, and if a microgrid shares some of this load, it will help both the microgrid customer and everyone using the larger grid. This leads to another selling point. Microgrids could become model citizens a term the consortium’s scientists apply to loads that help the power system rather than simply take from it. Specifically, microgrids can inject power into the larger grid, which lessens stress on the overall system and helps maintain local service quality.
Microgrids are also becoming competitive. The latest distributed generators can produce electricity almost as cheaply as huge power plants, especially if benefits such as heat recovery are considered. In addition, recent advances in power electronics, such as inverters that connect small solar generators to the grid, make control of small-scale systems economically feasible for the first time.And generators are getting smaller, such as a closet-sized one-kilowatt solid oxide fuel cell being tested in France. There’s also the tantalizing possibility of incorporating fuel cell-powered cars into the microgrid. Simply park your car in the garage, plug it in, and supply power to a few homes. Or plug the car into your office and help power the building. “What better way to avoid load on the grid than to have everyone drive his or her own power plant around,” Marnay says.
This transformation will not happen overnight, but it demonstrates how microgrids along with increased end-user efficiency, improved energy transmission, and renewable resources can help shepherd the nation from decades of centralized power generation to a new era of decentralized, flexible, and environmentally friendly power generation. And ultimately, microgrids could change the way people think about electricity. As Marnay explains, today’s electricity market is driven by wholesale competition between power companies.
Retail competition, in which customers choose electricity based on price and service quality, is virtually nonexistent. Microgrids, however, will offer consumers a choice, and this choice will impose competitive discipline on power companies yet another way they’ll help bridge the gap between today’s electricity system and tomorrow’s demand.” Electricity demand continues to grow and people think we can get by with traditional power systems, but we can’t,” Marnay says. “We need better ways, and microgrids are one part of the answer to this puzzle.” According to the Ingenia report, the real obstacle is regulatory and economic inertia. Ironically, the same problems that had to be addressed when centralising power must now be faced in decentralising it.
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