“Freeze-Thaw Battery” Can Freeze Its Vitality for Later Use

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PNNL Long Duration Grid Battery

An extended-duration grid battery could possibly be charged with renewable power, then discharge that power when wanted months later. Credit score: Animation by Sara Levine | Pacific Northwest Nationwide Laboratory

Molten-salt battery marks step towards seasonal storage of grid-scale power

Scientists have developed a battery designed for the electrical grid that may retailer power for months with out shedding a lot storage capability.

The creation of the “freeze-thaw battery,” which freezes its power for later use, is a step towards batteries that could be used for seasonal storage: saving power in a single season, equivalent to spring, and utilizing it in one other, equivalent to fall.

The prototype is small, roughly the scale of a hockey puck. Nevertheless, the science behind the system has huge promise, foreshadowing a day when power from intermittent sources, equivalent to daylight and wind, may be saved for prolonged intervals of time. The examine by scientists on the Division of Vitality’s Pacific Northwest Nationwide Laboratory was revealed on-line on March 23, 2022, within the journal Cell Reviews Bodily Science.

“Longer-duration power storage applied sciences are vital for growing the resilience of the grid when incorporating a considerable amount of renewable power,” mentioned Imre Gyuk, director of Vitality Storage at DOE’s Workplace of Electrical energy, which funded the work. “This analysis marks an vital step towards a seasonal battery storage resolution that overcomes the self-discharge limitations of at the moment’s battery applied sciences.”

Harnessing and packaging nature’s power

Renewable sources ebb and circulation with nature’s cycles. That makes it troublesome to incorporate them in a dependable, regular stream of electrical energy. Within the Pacific Northwest within the spring, as an example, rivers heavy with runoff energy hydroelectric dams to the max simply as winds blow fiercely down the Columbia Gorge. All that energy have to be harnessed instantly or saved for a couple of days at most.

Grid operators would like to harness that springtime power, retailer it in giant batteries, then launch it late within the 12 months when the area’s winds are gradual, the rivers are low, and demand for electrical energy peaks.

The batteries would additionally improve utilities’ capability to climate an influence outage throughout extreme storms, making giant quantities of power out there to be fed into the grid after a hurricane, a wildfire or different calamity.

“It’s quite a bit like rising meals in your backyard within the spring, placing the additional in a container in your freezer, after which thawing it out for dinner within the winter,” mentioned first writer Minyuan “Miller” Li.

The battery is first charged by heating it as much as 180 levels Celsius, allowing ions to flow through the liquid electrolyte to create chemical energy. Then, the battery is cooled to room temperature, essentially locking in the battery’s energy. The electrolyte becomes solid and the ions that shuttle energy stay nearly still. When the energy is needed, the battery is reheated and the energy flows.

The freeze-thaw phenomenon is possible because the battery’s electrolyte is molten salt—a molecular cousin of ordinary table salt. The material is liquid at higher temperatures but solid at room temperature.

The freeze-thaw concept dodges a problem familiar to anyone who has let their car sit unused for too long: a battery that self-discharges as it sits idle. A fast discharge rate, like that of batteries in most cars or laptops, would hamper a grid battery designed to store energy for months. Notably, the PNNL freeze-thaw battery has retained 92 percent of its capacity over 12 weeks.

In other words, the energy doesn’t degrade much; it’s preserved, just like food in a freezer.

Rushing Water PNNL

Rushing water can be a powerful, perhaps long-lasting, source of renewable energy. Credit: Photo by RomGams | Shutterstock.com

Ordinary ingredients a plus

The team avoided rare, expensive and highly reactive materials. Instead, the aluminum-nickel molten-salt battery is chock full of Earth-abundant, common materials. The anode and cathode are solid plates of aluminum and nickel, respectively. They’re immersed in a sea of molten-salt electrolyte that is solid at room temperature but flows as a liquid when heated. The team added sulfur—another common, low-cost element—to the electrolyte to enhance the battery’s energy capacity.

One of the biggest advantages of the battery is the composition of a component, called a separator, placed between the anode and the cathode. Most higher-temperature molten-salt batteries require a ceramic separator, which can be more expensive to make and susceptible to breakage during the freeze-thaw cycle. The PNNL battery uses simple fiberglass, possible because of the battery’s stable chemistry. This cuts costs and makes the battery sturdier when undergoing freeze-thaw cycles.

“Reducing battery costs is critical. That is why we’ve chosen common, less-expensive materials to work with, and why we focused on removing the ceramic separator,” said corresponding author Guosheng Li, who led the study.

Grid Storage Launchpad PNNL

The Grid Storage Launchpad, where scientists will develop and test grid-scale energy storage technologies. Credit: Architectural rendering by Pacific Northwest National Laboratory

The battery’s energy is stored at a materials cost of about $23 per kilowatt-hour, measured before a recent jump in the cost of nickel. The team is exploring the use of iron, which is less expensive, in hopes of bringing the materials cost down to around $6 per kilowatt-hour, roughly 15 times less than the materials cost of today’s lithium-ion batteries.

The battery’s theoretical energy density is 260 watt-hours per kilogram—higher than today’s lead-acid and flow batteries.

Researchers point out that batteries designed for seasonal storage would likely charge and discharge just once or twice a year. Unlike batteries designed to power electric cars, laptops or other consumer devices, they don’t need to last hundreds or thousands of cycles.

“You can start to envision something like a large battery on a 40-foot tractor-trailer parked at a wind farm,” said coauthor Vince Sprenkle, senior strategic advisor at PNNL. “The battery is charged in the spring and then the truck is driven down the road to a substation where the battery is available if needed during the summer heat.”

Battelle, which operates PNNL, has filed for a patent on the technology. More information is available here.

Other authors of the paper include PNNL researchers Evgueni Polikarpov, Nathan Canfield, Mark Engelhard, J. Mark Weller and David Reed, and former PNNL scientist Xiaowen Zhan.

Reference: “A freeze-thaw molten salt battery for seasonal storage” by Minyuan M. Li, Xiaowen Zhan, Evgueni Polikarpov, Nathan L. Canfield, Mark H. Engelhard, J. Mark Weller, David M. Reed, Vincent L. Sprenkle and Guosheng Li, 23 March 2022, Cell Reports Physical Science.
DOI: 10.1016/j.xcrp.2022.100821

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