Whenever the sun shines on clear blue days, the River Falls Municipal Utilities is tapping into thermal power.

Starting last week, six solar panels, installed months ago on the Utilities’ power plant roof on Winter Street, became operational.

The 1,550-square feet of mirror-like panels absorb the sun’s energy, which is then used to heat an anti-freeze substance called glycol that’s circulated to three boilers through a heat exchanger.

The boilers fire up the power plant’s five dual-fuel engine generators that send energy to a grid shared by the 37 members of Wisconsin Public Power Inc. (WPPI), to which River Falls belongs.

Before the solar panels, natural gas was used to heat the power plant’s generators.

“It’s a good application of an evolving technology that has advanced over the years and become cheaper and more efficient,” said Mark Freeborn, the Utilities’ electrical generation engineer. “As long as there’s sun, the heat panels will run year around.”

The Utilities invested $40,000 to buy and have the panels installed by Solar Mining Co. out of De Pere. A $9,250 grant from WPPI defrayed the investment cost.

Jan Lorenz, Utilities’ customer service supervisor, said the savings from using solar power is expected to be 35-45% annually. Even with that savings, it could take more than 10 years to recoup the solar panel investment.

Still, with natural gas prices fluctuating and often going up, Freeborn said the renewable energy initiative makes sense.

Lorenz said the efficiency of the solar panels will be checked in the next year before actual financial savings are verified. She said WPPI promotes the idea of using renewable energy sources whenever feasible.

“Our Utility has talked about doing something like this for almost four years,” she said. “The power plant’s location is a good one because of its southern exposure for the sun.”

Lorenz said River Falls is an environmentally conscious community that will likely embrace the solar power initiative.

The solar panels will be used for educational purposes, too, including for visiting professors, teachers and their students.

To schedule a tour of the power plant and learn more about the Utilities’ solar panels, call Freeborn at his local cell phone number, 222-4396, or the power plant at 425-0917.