A team of USU researchers is getting some national attention for a project that could give electric vehicle batteries a second life as solar energy storage.
The team from USU’s Utah Power Electronics Lab includes professors Hongjie Wang and Regan Zane as well as doctoral students Marium Rasheed and Mohamed Kamel. Working with Maryland-based research firm Dream Team, the researchers are developing technology that could adapt batteries retired from electrical vehicles for storing solar energy.
“That would solve two problems,” said Wang, the project’s principal investigator. “One is how to handle the retired batteries from electrical vehicles. And the second one is to reduce the solar energy storage cost.”
The project is one of 10 finalists out of 121 teams competing for the $3 million American-Made Solar Prize.
As the lithium-ion batteries in electric vehicles are charged and discharged, they lose some of their capacity. In vehicles, losing battery capacity means losing mileage per charge, so drivers will replace batteries with as much as 85 percent of their storage still usable, according to a USU College of Engineering press release.
“But solar energy storage is stationary, so it does not have that high requirement on the capacity,” Wang said.
There are clear advantages to storing solar energy — you can generate electricity when the sun’s shining and then still use it when it’s not. Most current home solar systems don’t have a battery backup, however, largely because of how expensive new batteries can be.
Zane, director of USU’s SELECT and ASPIRE research centers, said he’s long wanted to add storage to his own home’s solar power system.
“Every few months I look at it again and think, ‘I sure wish I had battery backup at the house,’” Zane said. “And we will before long, I imagine, but boy, the economics are still pretty tough.”
Even though the cost of those new battery systems is still coming down, it can take 10 years or more for solar storage to pay for itself, Zane said. The goal of USU’s project is to cut those costs in half by buying retired EV batteries.
Electric vehicle battery packs are made up of dozens or even hundreds of smaller battery cells. Due to a number of causes, those cells degrade at different rates.
“When a battery pack’s capacity is not evenly distributed, if we just use it in that way it will have a shortened lifetime and that’s not good for any storage application,” Wang said.
Currently, Wang said, most companies that buy EV batteries disassemble them, test the cells and then reassemble all the cells with similar remaining capacities into homogeneous battery packs. The USU technology can take a wide variety of batteries, determine the capabilities of each individual cell and balance their use accordingly to greatly extend the life of the storage system, Wang said.
“The key value for the technology is to extend the battery lifetime, so it works for retired batteries from electrical vehicles, but it also works for new batteries,” Wang said. “With this active balancing technology, a new battery’s lifetime can be extended up to 40%.”
The team is hoping their modular design will prove so flexible that it could easily be scaled up from residential solar applications measured in kilowatt-hours of capacity all the way up to storing megawatt-hours, a scale that could make the tech useful even for power companies. If all goes according to plan, a demonstration of the technology could be ready later this year, Wang said.
Electric Power Systems, a company headquartered in North Logan and one of ASPIRE’s funding partners, is using technology developed from the same roots as USU’s Solar Prize entry to improve batteries for “first life” batteries, especially for aerospace. EP Systems isn’t currently involved in the solar project, Zane said, but the company specializes in lightweight battery packs with smart management systems also capable of cell-by-cell active balancing.
“We haven’t talked to them directly about this solar project,” Zane said of EP Systems, “but they’re also interested in charging solutions at airports for aircraft and things like that, and they’ve been looking at their own solutions for taking batteries out of aircraft and using them, let’s say, at an airport” in second-life applications.