Viewpoints: How electrical 'microgrids' might revolutionize power transmission

Jul 2, 2011 - Peter Asmus - sacbee.com

The Sacramento Municipal Utility District has long been seen as a clean technology pioneer. After all, this is a utility that shuttered a nuclear reactor after a public vote in 1989 and has since blazed trails on wind, solar and energy efficiency.

The company's corporate headquarters will soon show off a new technology – a "microgrid" – that many other utilities have long loathed and resisted. Microgrids promote energy independence, even allowing customers to secede from the larger utility grid powered up by their own resources. In an energy sector dominated by monopolies and centralized planning, microgrids could be a game-changer.

What exactly is a microgrid? In essence, it is just a miniature version of today's sprawling transmission and distribution grid, except much smaller in scale.

Microgrids are usually limited to serving a handful of customers, most often a campus featuring a cluster of buildings, such as a college or military complex. Mobile military microgrid applications are also being developed by defense contractors such as Lockheed Martin, with the idea being that these solar-powered temporary power systems could be set up within a day and then deployed during combat missions.

In the case of SMUD, its microgrid will be fueled primarily by solar photovoltaic panels, small combined heat and power units – which generate both electricity and heat from natural gas – and zinc flow batteries. It is expected to be up and running this summer.

In energy engineer terms, the fundamental concept of a microgrid can be summed up as an integrated energy system consisting of distributed energy resources and multiple loads (i.e, buildings and appliances) operating as a single, autonomous grid either in parallel with or "islanded" from the existing utility power grid.

Perhaps the most compelling feature of a modern microgrid is the ability to separate and isolate itself – known as "islanding" – from the utility's distribution system during brownouts or blackouts. SMUD hopes its planned microgrid will allow its most critical operations to continue to function in the event of a larger power outage affecting the Central Valley.

Over the long term, these microgrids represent a vehicle to allow the developing world to leapfrog past the industrial world's reliance upon large, sprawling transmission systems and instead create nimble, small-scale sustainable energy networks that hardly touch the landscape.

Shorter-term, microgrids represent a bottom-up solution to improving reliability and boosting reliance upon indigenous resources, which, in the case of Sacramento, is the sun. Once the SMUD microgrid is fully tested, the utility will evaluate whether it might sponsor such islands of power or allow the private sector to develop these microgrids.

Why microgrids?

Today, more than 95 percent of the solar and small wind systems connected to the larger utility grid must shut down during emergencies – storms or terrorist attacks. This exasperates microgrid advocates, who argue that this is precisely when these on-site renewable energy sources could offer the greatest value, both to owners, who plunked down $10,000 to $30,000 to install their own solar or small wind systems, as well as to the rest of society. Instead of firing up the dirtiest of power sources – diesel generators – a microgrid could, theoretically, allow folks to power up vital services with a mix of renewable and other resources.

Utility engineers have historically opposed the concept of "islanding" on the basis of safety and lack of control of their own power grids. The standard line was that unintentional islanding endangered the lives of crews working to restore power. Today, however, a host of new power conversion technologies has convinced the Institute of Electrical and Electronics Engineers that islands of self-sufficient microgrids are no longer a threat to either workers or to the utility grid in general.

So, SMUD is among a handful of utilities exploring how microgrids can deliver benefits – instead of being perceived as a threat. Other utilities currently investigating how microgrids could help them do their jobs better include San Diego Gas & Electric, American Electric Power and Canada's B.C. Hydro.

California in the lead

SMUD's corporate headquarters is deploying a technology that is actually the antithesis of the "smart grid" being developed by investor-owned utilities such as Pacific Gas & Electric. Developed with help from the California Energy Commission and the University of Wisconsin, newly developed software and "smart" switches allow all generation sources and appliances and other "loads" to harmonize like a commune when the grid goes down. Unlike the complexity of sensors and smart meters necessary for the smart grid, this new microgrid software is so simple and dumb that it could allow small solar communities in Africa, South America, the Mideast and Australia to boost reliance upon small solar and wind systems, while accelerating power sharing and collaborative ventures.

SMUD is also rolling out a $6 million residential storage project that takes the idea of a microgrid down to the individual home level, with back-up emergency storage provided by lithium ion batteries, which are also being integrated into tomorrow's plug-in electric hybrid vehicles.

Several new microgrid projects have popped up here in the Golden State, with General Electric developing a microgrid at Twentynine Palms, the largest U.S. Marine Corps base near Joshua Tree National Park in Southern California. For the military, the primary appeal is security, both cyber and physical, since the term "emergency" is a 24/7 matter.

One of the largest microgrids in the world should be up and running later this year at the University of California, San Diego. At 42 megawatts in size, this microgrid could power a small city of 25,000 residents. And finally, SDG&E is also developing a microgrid at Borrego Springs in the high desert, looking to tap excellent solar energy resources to help sustain operations at a remote utility substation.

Bottom of the pyramid

Promoters of microgrids have opportunities in poorer countries that have yet to develop centralized power plants with radial transmission lines strung across the landscape.

Typically, these microgrids will be on a smaller scale and have a simpler design. The first ones being built in British Columbia will be only 100 kilowatts in size, about one-third the capacity of SMUD's corporate headquarters. Over the long term, however, the markets in developing countries could become the largest microgrid sector. Why? It is quite feasible that as smaller microgrids become networked with each other, these pockets of power may obviate the need for – or greater reduce the scale of – any central transmission grid.

Ironically, deploying state-of-the-art microgrids in developing countries may allow them to leapfrog over developed nations in the sophistication and efficacy of electric grid operations, offering enticing business prospects for microgrid developers that actually can deliver real social and environmental value and component suppliers – a rare combination these days. This may be the most attractive "bottom of the pyramid" business model of any kind available today.