Among the many issues that electric vehicles face in their quest to be adopted by millions of Americans is how long their batteries will be useful. The lithium-ion batteries being used in most EVs (electric vehicles) are recommended to be used only for 20 percent of their total capacity, because these lithium-ion batteries lose capacity with time and use.
After about three or four years, most EV batteries are worn down to about 80 percent strength, and their driving radius shrinks, requiring the battery to be replaced. These old batteries still have use, and scientists are now trying to figure out the best way to take the old batteries and use them for industrial or commercial purposes.
Right now there’s an exciting project going on involving the U.S. Dept. of Energy (DoE) and the Oak Ridge National Laboratory in Tennessee, where a stationary storage system is being experimented with. This system could eventually lead to an energy storage device that’s significantly cheaper than one that would be assembled from new batteries.
The DoE estimates that there will be approximately one million lithium-ion batteries per year becoming available from various carmakers on the “secondary market” starting in 2020, and if there were a way to harness this potential energy source, it could have a large impact on the powering of homes and businesses.
Dr. Imre Gyuk is the manager of the Energy Storage Research Program in DOE’s Office of Electricity Delivery and Energy Reliability, and he and a team at Oak Ridge are currently in the second year of a three-year testing cycle.
Recycling these lithium-ion batteries is really a hassle right now,” said Omer Onar, a member of the research and development staff at ORNL. “There are only three to four companies that do them, and it’s really costly, and they mostly recycle laptops, cameras, that kind of thing. So if we want to have these batteries make more sense in terms of economy, we need to figure out better ways to use them after they’re no longer useful in cars.”
The DOE and Oak Ridge Lab are currently testing five batteries first used in a Chevrolet Volt, the first “mainstream” electric vehicle sold in the U.S., trying to ascertain if a community energy storage system could put electricity on the grid.
In theory, by distributing electrical energy storage into many locations, the units could provide the benefits of a centralized unit, but could also have more localized applications.
Currently the ORNL platform provides 25 kW of power and 50 kWh of energy that could provide backup.
Where could this kind of backup and community energy be used? Michael Starke, another researcher working at ORNL, defined “stationary applications” as those that can help current power substations and even home appliances. They may also help support a transition network, and maybe most importantly in this era of enormous weather disasters, help cities and states recover from storm issues.
One area of research that the ORNL scientists have been working on is collecting a “load bank,” which is basically creating a “profile” of residential homes.
“We can load the residential data into the bank, and it will look like a residential load profile, and see exactly where the energy storage system could be used best, and when it would be most useful,” Onar said. “We’re going to demonstrate that when you have charging and discharging cycles from that pattern, and the cycling on a storage system is tracked, it could lead to a lot of savings.”
Other industrial applications for the repurposed EV batteries are as a key enabling technology for the future smart grid, and the batteries could also allow intermittent energy sources like wind and solar to integrate into the grid.
“We can also operate our power plants to their highest efficiency with energy storage,” Starke said. “There are several operating points where those fossil fuel plants can get to their lowest emissions.”
“Really, it’s about trying to find applications where energy storage makes sense,” Starke added. “With the ability to get secondary use out of these batteries, we’re helping with energy in multiple ways.”
Dr. Gyuk also emphasized that the repurposed batteries’ use in a smart grid “is a lot smarter if you have storage.”
“When you’re doing solar or wind, if you restrict yourself to a smaller area and the wind stops, you have to stop (getting energy),” he said. “If we can have storage as a buffer for these changes, whether in load or in regeneration, it can be a big advantage.”
So where might these EV batteries be re-used? Interestingly, Gyuk said he thinks that the areas of the U.S. where people were early adopters of electric vehicles will be the first users of repurposed EV batteries.
“It’s not going to happen all over the country (immediately); it’ll happen in California, Silicon Valley, Tennessee, places where EV’s have really caught on,” Gyuk said. “Because shipping these used EV batteries is not easy. They’d have to go to a specialized center of some kind to be transported.”
One possible obstacle in converting old EV batteries into energy storage systems is the lack of uniformity in who owns the EV batteries. According to Gyuk, some EV batteries are owned by the vehicle owner, who could conceivably decide not to turn his battery in when it went below 80 percent, opting to drive on it further.
In other cases, the EV battery is owned by the manufacturer, who would simply issue a warranty to the EV buyer for, say, three years, and then replace the battery at that time.
“If you have some batteries that are at 80 percent (capacity) and others at 70 percent, and you try to put them together in a storage system, that’s a bad recipe,” Gyuk said.
Once the testing, done by the DoE and ORNL in conjunction with teams from ABT and General Motors, is complete in the lab, the scientists said that it would be field-tested in a number of different situations.
Gyuk indicated that the likely first test for the batteries in the U.S. could be in a commercial building where they can use the storage system for integrating renewables, and also for reducing demand charges.
“After checking it out and testing the system, we will show the technical feasibility,” Gyuk said. “We may suggest what kind of policy structures would open the system for best use, but then it’ll be up to private entrepreneurs to manufacture it.
“And there are companies of various sizes, from GE to small businesses who are willing to incorporate batteries in microgrids and facilities,” Gyuk concluded. “At the moment they’re not in a position to use refurbished lithium-ion batteries, because they don’t know if they work. Soon, we hope they will know.”