Commonwealth Edison Makes the Case for its Bronzeville Microgrid Cluster

Aug. 3, 2017
Chicago-based Commonwealth Edison took a major step last week toward building the much-watched Bronzeville microgrid, a project that will test the emerging concept of microgrid clusters, or a ‘grid of microgrids.’

Chicago-based Commonwealth Edison took a major step last week toward building the much-watched Bronzeville microgrid, a project that will test the emerging concept of microgrid clusters, or a ‘grid of microgrids.’

The Exelon subsidiary petitioned the Illinois Commerce Commission for permission to recover costs for the $25 million project through customer rates (Case 17-0331).

Designed to serve 10 critical facilities, the Bronzeville microgrid will connect to a nearby microgrid at the Illinois Institute of Technology. Working in coordination, the microgrids will demonstrate how the whole-is-greater-than-the-sum of its parts when microgrids ‘talk’ to each other.

 “…likely be the most advanced clustered urban microgrid in the United States”

“The project will likely be the most advanced clustered urban microgrid in the United States,” said Joseph Svachula, ComEd’s vice president, smart grid & technology, in testimony before the commission.

Should the Bronzeville microgrid go forward as planned, it will place Illinois in league with other microgrid leaders like California, Connecticut, Massachusetts, New Jersey and New York.

The value of clustering microgrids

Svachula described the clustering of microgrids as an important step toward creating a decentralized grid. The Bronzeville cluster “enables us to understand how microgrids interface, and how resources from neighboring microgrids can be used to keep power flowing to customers.”

Microgrids are viewed as guardians of electric reliability, since they can disconnect from the grid during a power outage and deliver electricity to local customers with their on-site generators.

Working together, clustered microgrids can offer even greater electric resilience, since they can coordinate their resources and serve a larger geographic region, Svachula said. Clustered microgrids theoretically need fewer resources to maintain the same level of service.

“In other words, even in the event of major system disruptions, some resources can be shared to keep adjacent microgrids operating,” he said. “This could become a cost-effective approach to modernizing the distribution system in the long run.

Bronzeville Microgrid Project Specs

Phase I – 2.5 MW load, solar PV and battery storage, diesel back-up

Phase II – 4.5 MW load, 7-MW of controllable generation (possibility natural gas)

Cost: Total $25 million. Includes $14.7 million for generation and $11.3 million for distribution upgrades

Contributions: $4 million DOE grant; $600,000 from partner

Will serve 10 community facilities in the Bronzeville section of Chicago, including the Chicago Police Department headquarters, the De La Salle Institute and the IIT Math & Science Academy, a library, public works buildings, restaurants, health clinics, public transportation, educational facilities, and churches.

The Bronzeville microgrid also is noteworthy because it represents the latest case of a utility in a restructured state putting forward an argument to develop a microgrid. In states like Illinois that brought competition to their electric industry, utilities cannot own or build power plants. But they can own distribution lines and related facilities, and recover costs for those assets from ratepayers.

Uncertainty exists about how to define microgrids — as power plants or distribution assets — since they can act as either. The distinction is important because it determines if a utility can own a microgrid in a restructured state, as well as ask ratepayers to cover the microgrid’s costs.

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Microgrid as distribution asset, not generation

ComEd argued that rate recovery is justified for the Bronzeville microgrid because it will act as a distribution component of the grid. More specifically, its solar and other power sources will appear as a “broken distribution component” that can be restored by way of microgrid islanding.

The utility filing also offers a different way to think about the microgrid’s output during normal operations.

Within the PJM wholesale market, ComEd can designate power supply two ways – as energy that serves customers or as ‘unaccounted for energy’ (UFE) and line losses. Utilities are allowed to recover costs for UFE and line loss.

It makes sense to think of the microgrid as providing these services because from a practical standpoint, the microgrid will reduce line loss, and therefore lower the amount of generation required to serve customers, according to the utility’s testimony.

Less power lost in transit means less power must be generated within the utility’s service territory to serve customers, which reduces costs. As a result, the microgrid saves money for customers. Those savings can help offset the microgrid costs, said Scott Vogt, ComEd vice president, energy acquisition

As further evidence that the microgrid is not a ‘generation’ resource in this instance, ComEd pointed to its size. If it were being built to act as a power plant, the microgrid would have been sized to generate more megawatts and placed in a different geographic location, the utility said.

In any case, ComEd ultimately may not own the generation aspects of the grid. The utility intends to put that portion of the project out to competitive bid and will consider a leasing arrangement or ownership by a third party, if that proves most cost-effective.

Other arguments for utility cost recovery

Adding to its argument that it should be allowed to recover costs, ComEd said the Bronzeville microgrid will:

  • Serve as an oasis during a power outage where residents of neighboring communities can secure food and supplies
  • Furthers our understanding of grid technology, including its cybersecurity
  • Provides the opportunity to work with communities and businesses to better understand the benefits of advanced distribution system design
  • Offers real world learnings about optimal types about coordinating distributed energy on a distribution system.

“This demonstration will support critical infrastructure in a vital and vibrant Chicago neighborhood where we’re building upon the strength of the smart grid platform,” said Anne Pramaggiore, president and CEO, ComEd. “It will enable us to measure the capability of a microgrid to increase grid security and resiliency against disruptive events, such as a cyber-attack, and test the ability to recover from them. This is the kind of innovative technology we need to be testing in our state as we plan for the continued evolution of our system.”

Utilities in other states have run into rough going convincing regulators that they should be allowed to recover microgrid costs. So the microgrid industry will be carefully watching how the Illinois Commerce Commission handles ComEd’s petition.

Last year in Maryland another Exelon subsidiary, Baltimore Gas & Electric, lost its bid for rate recovery for two public purpose microgrids. In Pennsylvania, PECO Energy proposed microgrids for a high-density neighborhood with an 8.6 MW load.  When the proposal ran into opposition last year before the Pennsylvania Public Utility Commission, PECO withdrew its application and convened a stakeholder collaboration to work out differences. A bill is now before a Pennsylvania state legislative committee that would allow utilities to build microgrid pilots

In Illinois, ComEd’s petition for rate recovery comes after the state legislature failed to include funding for the Bronzeville microgrid and several others as part of a major energy bill last year.

ComEd is requesting that the Illinois commission rule on the Bronzeville microgrid by February 1, 2018. [Editor’s note: The commission is now expected to rule by February 28.]

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About the Author

Elisa Wood | Editor-in-Chief

Elisa Wood is the editor and founder of She is co-founder and former editor of Microgrid Knowledge.

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