Urban Scale

The term “microgrid” has been a part of broader smart grid conversations for several years, but definitions have varied. Campus-sized projects have brought these electrical-systems-in-miniature to universities and military installations, but some smart grid advocates argue developers are thinking just a bit too small. Think urban scale, they say. Two prototype projects now underway are seeking to do just that.

Building on the basics
Regardless of the size of a microgrid, some basic components are common in all interpretations of the concept. These include generation sources, intelligent switching equipment, customer-side information and controls. Advanced communications tie it all together. In Borrego Springs, Calif., San Diego Gas & Electric (SDGE) is testing a community-sized microgrid to better understand ways residential solar-power systems can contribute to overall system stability.

According to Vic Romero, SDGE’s director of asset management and smart grid projects, the 2,800 residents of Borrego Springs, a remote desert community, already have approximately 500 kilowatts of solar-generating capacity. A single transmission line, with power stepped down through a single, three-circuit substation, serves the area. Work will focus on the substation circuit with the largest amount of connected solar-power capacity.

“The idea is to identify benefits,” Romero said, adding that these benefits include reduced peak demand, better reliability and quicker repair. Networked equipment will include photovoltaic-generating sources, home area networks, smart meters, utility gensets and battery storage at both the residential and substation levels. “It’s all going to interface with our systemwide outage management.”

Improved reliability is a major goal of the effort, through what SDGE is calling “self-healing” technology, which includes new control equipment tied to existing switches. The utility hopes the technology will be able to identify actual or potential problems faster than existing devices and possibly reroute power around problem areas to limit outage-affected areas. Researchers also hope to evaluate how customer-based generation might be able to help in an outage.

While real-time pricing won’t be a part of this study, homeowners will have access to real-time usage data. Romero and his team want to see if this information has an effect on how energy-conscious residents use energy, especially in the desert location, where they depend heavily on air conditioning.

In 2011, the utility is getting generators, batteries and other equipment in place, with start up planned for next year and a final report expected in 2013.

Innovating new paradigms
In Boston, the Galvin Electricity Initiative, a national advocate for smart grid technologies and policies, leads a group focused on the Innovation District, an underused area that is the target of a city-led redevelopment plan. The group is looking beyond meters and switches, toward a vision of how utilities and customers might relate to each other.

At a high level, Galvin sees a future state in which utilities are fully segregated from generating assets, with a sole purpose of delivering reliable electricity. According to Deputy Director John Kelly, customers would buy electricity, in aggregate, directly from their independent system operator (ISO), with transparent access to actual wholesale power costs and generation sources. In this view, microgrids would be substation-sized—in other words, they’d encompass the full collection of equipment from the utility substation to a household (or business) end-use device. The Galvin initiative sees three specific benefits:

• Easier access to clean generation sources
• Improved power quality and reliability
• The ability to engage directly with customers to help cut energy costs

Researchers plan to model at least some of these ideas in the Boston study, Kelly said. Program leaders are recruiting five midsize commercial tenants within the district, with annual usage in the range of 100,000 kilowatt-hours, to form a buying group. In cooperation with the local utility, NStar, this group will go directly to the region’s ISO for power purchases, with access to real-time data and time-of-use pricing. The city of Boston will invest in efficiency upgrades and on-site generation, as part of its overall redevelopment plans for the district. NStar will follow up with a second phase that would include developing a reliability plan, most likely for the entire Innovation District.

The paradigm shift Galvin envisions, from utilities as vertical, turbine-to-toaster electricity suppliers to, more simply, owners and operators of local distribution systems, will take time, Kelly said. The group is also working with 20 Illinois cities that are aggregating power purchases to enable better pricing structures and create pressure for reliability improvements. Galvin hopes to take the initiative to cities across the United States.

Once this happens, Kelly said, “we see [cities] putting pressure on utilities to put in place a reliability improvement plan—we think [cities] are going to demand this and will drive change.”

ROSS is a freelance writer located in Brewster, Mass. He can be reached at chuck@chuck-ross.com.

About the Author

Chuck Ross

Freelance Writer
Chuck Ross is a freelance writer and editor who has covered building and energy technologies for a range of industry publications and websites for more than 25 years. He specializes in building and energy technologies, along with electric-utility bus...

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