Bronzeville's microgrid: what islands when the grid fails

I.What islands, and what does not

At the center is islanding (running disconnected from the regional grid on local power alone). On a normal day, Bronzeville draws its power from the same system as the rest of the city, balanced by PJM Interconnection, the operator that runs the high-voltage network across Illinois and a dozen other states. When a fault hits upstream, the microgrid can open its connection and keep a defined set of blocks energized from its own mix of solar, battery storage, and on-site generation.

Its footprint is bounded, and the boundary is most of the story. At last public report the microgrid serves roughly 1,000 customers, including homes and a set of critical facilities such as a police station and health sites, per ComEd's project page. If your address sits inside that line, islanding could keep your lights on through an outage that darkens the surrounding streets. If it sits a few blocks outside, the microgrid does nothing for you, and that line on the map matters more than any brochure.

II.The honest math

On the hardware side, ComEd's materials describe something modest: on the order of 750 kilowatts of solar and a battery system in the hundreds of kilowatts, backed by larger on-site generation for longer stretches of islanding. Those renewable pieces do not, by themselves, run a neighborhood for days. They shave peaks, smooth the switchover, and cover part of the load, while the generation and the grid connection carry the rest.

Money is the harder question. The project cost on the order of tens of millions of dollars, with partial funding from the US Department of Energy and the balance recovered through rates and programs the Illinois Commerce Commission oversees. Whether that is a good deal depends on how often the grid actually fails here, and on how much of what ComEd learns in Bronzeville lowers the cost of the next microgrid. It depends, honestly, and the dockets are where that argument gets settled.

III.Who is in the drawing

Four names carry most of this. ComEd owns and operates the microgrid and the controls that decide when to island. The Illinois Commerce Commission approved the project and oversees what customers pay for it. PJM Interconnection keeps the regional system balanced and sets the rules a grid-tied microgrid has to follow at the seam where it connects.

Next door is the fourth. The Illinois Institute of Technology, whose Mies van der Rohe campus gives this part of the South Side its ruled, horizontal skyline, has run its own microgrid for years. The two are designed to link into a cluster (two or more microgrids that can support each other or island together), which ComEd has described as among the first such clusters in the country. A cluster is more resilient than a single island and harder to control, and both of those are true at the same time.

IV.Worth watching this month

1. ComEd's Bronzeville microgrid project page for any revised figures on customers served, solar, and storage, which the utility updates from time to time.

2. The Illinois Commerce Commission docket system at icc.illinois.gov for filings tied to microgrid cost recovery and grid modernization, most of them routine.

3. PJM Interconnection notices on distributed energy and interconnection, which can quietly change what a microgrid is allowed to do at the grid seam.

4. US Department of Energy microgrid resources for any evaluation of the Bronzeville and IIT cluster, which tend to appear months after the work itself.

5. ComEd outage alerts for the South Side through this storm season, the real test of whether the island does what the drawing promises.