Ames utility outlines plan to replace aging Unit 7, preserve Unit 8 and add flexible gas capacity plus renewables

Ames electric utility staff gave a detailed briefing to City Council on June 17 about the condition of the city’s generating units, projected load growth and a staged plan to replace retiring capacity while increasing renewable energy.

Don, electric utility director, and Lane Farber, the city’s new energy services coordinator, told council that Unit 7 — a steam unit installed in 1967 that burns refuse‑derived fuel (RDF) — faces substantial near‑term maintenance needs and is likely to be retired in about five to seven years once the RDF program ends. Unit 8, commissioned in 1982 and currently burning RDF and natural gas, is in better condition but will require longer-term replacement planning, staff said.

Why it matters: MISO (the regional transmission operator) requires load‑serving entities to hold capacity to meet peak demand plus reserve margins. Staff said losing Unit 8 for the three summer months without replacement capacity would cost the utility an estimated $4 million in capacity replacement in one season alone. Council heard that prudent planning is necessary to avoid a forced, costly market purchase if an existing unit becomes unavailable.

Staff reviewed an engineering life assessment by a consultant that used a green/yellow/red scoring of equipment condition. The assessment flagged several critical components on Unit 7 (boiler…