Geneva staff outlines seven potential solar sites, recommends study of GGF site with batteries

Geneva officials heard a presentation on May 20 on potential solar installations on city-owned property, estimated project costs and options for battery storage that could increase capacity savings.

The study, presented by Superintendent of Electric Works Aaron Holton, identified seven candidate locations — Prairie Green, Fire Station 1, the downtown parking garage, the wastewater treatment facility, the GGF site, Public Works, and Fire Station 2 — and modeled generation, approximate system size and estimated capital costs. Holton told the special committee the largest site, Prairie Green, could technically support up to about 50 megawatts but that a 10-megawatt layout on roughly 60 acres more closely matches the city’s system hosting capability and would require fewer system upgrades.

Holton said a 10-megawatt utility-scale installation would produce roughly 16,000 megawatt-hours annually, while rooftop and distributed sites described in the study together could yield about 21,000 megawatt-hours, or roughly 6% of Geneva’s annual usage of about 360,000 megawatt-hours. Estimated installed costs in the study (exclusive of distribution or substation upgrades) included about $11.75 million for a 10 MW utility field at Prairie Green, about $4.2 million for a parking-garage canopy and about $2.9 million at the GGF site. A rooftop bundle total was listed at roughly $9.7 million; individual site cost estimates provided later by staff included Fire Station 1 at roughly $256,000, wastewater at about $1.9 million, Public Works at $2.4 million and Fire Station 2 at $206,000.

The presentation also tested battery energy storage scenarios. One distributed scenario (26 MWh co-located across city sites) was projected to yield about $720,000 per year in capacity savings and an additional $3.3 million in capacity savings attributable to GGF-type operations for a combined capacity benefit of roughly $4 million annually, against an added installed cost the presenter estimated at about $8.9 million. A large, 50-MWh battery sized alongside a 50-MW Prairie Green field was estimated at roughly $48–49 million installed, with about $1.9 million in additional annual capacity savings but a longer payback.

Council members questioned lifecycle operating and maintenance costs, roof life expectancy for rooftop candidates, floodplain or permitting constraints at the wastewater site, and financing options. Several alderpersons favored pursuing GGF — the site near a substation that would tie directly into the utility bus and therefore return energy to Geneva’s load accounting — and asked staff to return with more granular modeling of a GGF-plus-battery scenario, updated cost estimates, and lifetime operating expenses. A number of council members emphasized that Geneva’s existing power contracts currently meet demand and that oversupply could force the city to sell excess energy at market (spot) prices.

There was no formal vote to approve construction. By verbal concurrence in the meeting, council members directed staff to remove Prairie Green from further consideration for immediate development; the mayor summarized that direction as “Scratch Prairie Green.” Holton said he will return with updated cost figures and scenarios, including smaller battery options and more granular site-level numbers.

The presentation and supporting slide deck will be posted to the city website and staff indicated they will continue detailed analysis before any formal procurement or contract decisions are brought back to the council.