As solar panels devoured the winter sun from the roof of North Market on a recent morning, a new set of nearby panels was sending energy right back to the sky.
Equipped with a 3M-manufactured film that reduces temperatures without electricity, these reflective panels can dramatically improve the efficiency of energy-intensive refrigeration systems.
For the North Minneapolis grocery store — the first in Minnesota with a SkyCool Systems installation — that means money saved. For a warming planet, that means greenhouse gas emissions reduced while cooling needs climb.
The world now faces “unavoidable multiple climate hazards” in the coming decades, according to the most recent U.N. climate report. Adapting to a changed climate in which air conditioning will play a bigger role has become more important as efforts to mitigate global warming have fallen short.
SkyCool and 3M are working together to sell the cooling panel systems to grocery stores and other users who consume a great deal of electricity keeping things cold — though the concept could spread to other energy-saving uses.
“Grocery stores run on thin margins — anything over 10% in energy savings is going to be very meaningful,” said 3M business developer Billie Pritzker. The panels can provide savings of 15% to 20%, she said.
Air conditioning and refrigeration consume a quarter of the world’s electricity and contribute 7% of global greenhouse gas emissions. SkyCool says its panels can save twice as much energy as similar-sized solar panels can produce.
Chief Executive Eli Goldstein knows the assertion raises some eyebrows.
“There’s always skepticism around new technologies,” said Goldstein, whose company is based in Silicon Valley. “This is a technology that can directly cool the environment. It’s a very clear cost-benefit.”
A few big-box retailers are trying out the panels as a way to meet ambitious carbon reduction goals. 3M is installing the technology on one of its plants in California. A data center is also piloting the cooling panels.
“There’s a lot we can do just by having these very reflective surfaces on rooftops,” Goldstein said. “Now how do you integrate it into a product, and who do you sell it to?”
How the technology works
3M’s high-tech piece of what feels like plastic — really hundreds of nano-layers of precise thickness that work together to reflect solar energy — is borrowed from the natural world.
“That same structure is in the wings of butterflies and fish scales,” 3M scientist Tim Hebrink said.
The type of film used to reflect sunlight and radiate heat back into the atmosphere relies on “passive radiative cooling,” another natural phenomenon seen when frost appears on windows even when air temperatures remain above freezing.
“The two key properties are solar reflectivity and thermal emissivity,” Hebrink said. “That’s what gives us the ability to radiate heat to the sky.”
SkyCool arrays work by cooling a fluid that moves below the panels and is pumped through refrigeration systems. The cooling helps reduce the run time of motors in the refrigeration system to reduce