Lima Saves $10M With Floating Solar on Drinking Water

Lima, Ohio, found a way to generate clean energy without giving up a single acre of farmland or park space.

The city completed a floating solar array on Twin Lakes Reservoir this past August. More than 3,000 solar panels now sit on the water surface, covering about four acres of the city's primary drinking water source. The panels feed electricity directly to the nearby water treatment plant, which uses more power than any other city facility.

The numbers tell an encouraging story. Lima expects to save nearly $10 million in electricity costs over the system's lifetime, with first-year savings around $200,000. For a city utility serving 35,000 residents, those savings can fund other community needs.

The technology solves a problem many cities face. Traditional solar farms need at least 10 acres to produce what Lima's floating system generates on four acres of water. That matters in communities where land competes with housing, businesses, and agriculture.

The panels attach to floating platforms made from high-density polyethylene, the same material used in food-safe water bottles. Anchors keep the array stable while allowing it to move with changing water levels. Eight onshore inverters convert the solar electricity into usable power for the water treatment plant, which processes 14 million gallons daily.

Cities from coast to coast are watching. Reservoirs already occupy space without competing for development dollars. Many sit right next to the facilities that need the electricity, cutting transmission costs and complexity.

The National Renewable Energy Laboratory has studied how floating solar affects different water bodies. Researchers found that the panels can reduce evaporation by shading portions of the water surface. Each reservoir presents unique conditions, though, from water depth to recreational use.

The Ripple Effect

Lima's project shows what happens when innovation meets practical problem solving. The city addressed its biggest energy cost without disrupting existing land use or building miles of new transmission lines.

Other communities with limited space now have a working model to study. The technology could particularly benefit urban areas where land costs make traditional solar farms financially difficult. Water utilities nationwide manage thousands of reservoirs that could potentially host similar systems.

The project required significant upfront investment, but the payback timeline makes economic sense for long-term municipal planning. As more cities complete floating solar installations, construction costs should decrease through economies of scale and improved manufacturing.

Lima turned its drinking water reservoir into an asset that serves double duty, providing both clean water and clean energy to the same community.