Energy Efficiency

Minnesota public power utility uses drones to map building heat loss

The roughly 1,600 people who live in Warren, Minnesota, are used to cold winters. In January, the city in northwestern Minnesota sees high temperatures of 15 degrees and lows of 5 below zero on average. The record low is 43 below zero.

The city’s public power utility has developed an innovative program to help homeowners and businesses find areas in their buildings that may be leaking heat and is preparing to offer on-bill financing to pay for energy efficiency upgrades.

Warren, with about 700 buildings, is finishing up a three-year program taking thermal images of the city’s rooftops using drones.

Starting next year, residents will be able to review the thermal images of their roofs to see if there are areas that may need extra insulation and gaps that need better sealing, according to Shannon Mortenson, Warren’s city administrator.

Utility linemen may be able to follow up with interested residents and take additional thermal images of their buildings, she said.

“It will give a lot of information to residents on what to do with their homes,” Mortenson said.

At the same time, Warren is preparing to offer its customers on-bill financing to help pay for energy efficiency upgrades that are made based on the thermal images, Mortenson said.

Under the planned on-bill financing, Warren’s utility will estimate the monthly savings that could be gained by adding insulation. Those savings will be used to pay down loans from the utility so residents won’t see a change in their bills, according to Mortenson.

Warren would like to land some grant funding to help begin a revolving loan fund for the on-bill financing program, she said.

Along with Minneapolis and St. Paul, Warren was part of a feasibility study that explored where the cities could achieve the most energy efficiency savings. For Warren, the answer was rooftop insulation, Mortenson said.

The thermal imaging program grew out of a climate program run by the University of Minnesota’s Institute on the Environment. The Climate-Smart Municipalities program in 2016 matched five cities in Minnesota — Duluth, Elk River, Morris, Rochester and Warren — with cities in Germany that have been recognized as “climate-smart” communities.

On a trip to Warren’s sister city, Arnesberg, officials learned about the city’s use of airplanes to take thermal images of their buildings, Mortenson noted.

Instead of planes, Warren opted to use drones to take the thermal images.

The project started in the winter of 2017 after Warren held town hall meetings to let residents know about it, according to Zackary Nicklin, who oversees the drone flights and manages “unmanned aircraft system” programs at the nearby Northland Community and Technical College.

The project faced several challenges, Nicklin said.

Ideally, good thermal images need at least a 20-degree difference between inside and outside temperatures, effectively limiting drone flights to the heating season, Nicklin said.

Also, for the first year and a half, Nicklin didn’t have permission to fly drones at night, but sunlight reduces the results of the imaging, so the flights were limited to about a half hour at dawn and dusk. Wind can also affect the results, Nicklin said.

Nicklin said he had to figure out how high the drones should fly to get good thermal images.

“There was a learning curve,” he said, noting he has been able to use his experience to enrich his drone programs at the community college.

Nicklin, who volunteers his time, is close to finishing the project.

Under Federal Aviation Administration rules, permission isn’t needed to take the thermal images, according to Nicklin. Although not required, Nicklin said he would only take side shots of buildings with permission.