During this time period Each year, the Pacific Northwest enjoys a temporary source of renewable energy. A stream of melted snow forms behind the region’s abundant dams just as strong winds blow through canyons, propelling rows of wind turbines. But by the end of summer, non-stop elements. In bleak times, states like Oregon and Washington are increasingly dependent on other, often dirtier sources of energy — like natural gas and coal produced by their neighbors.
Nature does not always appear when we need it. That’s a problem for most renewables. (Germans have the word dunkelflauteor “dark gloom” to describe a time when the sun and wind disappeared together.) For places like Washington state, which has a goal of 100 percent clean energy by 2045, the question arises. is how to fill those seasonal gaps. Maybe California is sunny in the summer, or the Midwest is windy, giving them the strength to trade. However, that is difficult. Have lack of wire to connect those places, for one thing. And besides, California has the same 2045 deadline for zero-carbon energy production, which further complicates sharing across regions. But there’s another option: store the energy from those temporary gusts and melt the snow to help it last through leaner time.
At the Pacific Northwest National Laboratory, researchers have come up with a possible solution: a rechargeable battery that stores energy for months using its own type of freezing and defrosting. Most batteries leak power by design. To charge and release energy, they rely on the easy movement of ions through a liquid electrolyte. But sometimes these ions slip through when there is no need for energy. That’s why the battery of an electric car to sit around will drain over time. PNNL battery, described in Physical Science Cell Report Last month, turn off that leaky faucet by freezing the pipes. It works on an electrolyte made of molten salt, which becomes liquid when the battery is heated to 180 degrees Celsius (that’s 356 degrees Fahrenheit), allowing ions to pass through it. As it cools, the salt becomes solid. The ions are trapped, frozen in place, and so is the energy.
Batteries are not generally considered an ideal way to store energy for weeks or months. So grid experts often look to physics-based solutions – things like pumping water into overhead reservoirs for later extraction, or compressing air into underground caverns. land – or use excess renewable energy to create fuels like hydrogen. Conventional wisdom is that batteries are too expensive to build at scale for that purpose. They are too difficult to create and contain too many valuable minerals to sit still while fully charged. But increasingly, researchers are looking at the unresolved chemistry of older and often cheaper battery designs.
Molten salt batteries fall into that category. During the 1980s, they were considered by automakers like Ford for electric cars, but lithium-ion battery soon got a foothold in small electronics, such as cell phones. The technology became dominant in part because it was so easy to recharge — it was simply a matter of moving ions back and forth within the cell. Other batteries involve chemical and physical changes that are more complex and difficult to reverse. They are like breaking a vase and then trying to put them back together.
The freeze-thaw method presents some of those challenges, because it means that the materials inside physically change – i.e. expand and contract – before each use. “You’re breaking a lot of connections and then trying to reshuffle them,” says Vincent Sprenkle, technical program manager for energy storage at PNNL. The solution was to design a battery with remarkable stability — pairing metals like nickel and aluminum together nicely, plus adding sulfur particles to increase stability. The prototype the researchers created was tiny – a box the size of a hockey puck. To activate it, they heated it in an oven to 180 degrees Celsius. Minyuan Miller Li, a battery scientist at PNNL who led the research, said: “You can do it in home oven. The researchers report that the resulting battery retains more than 90% of the energy put into it after three months. (Loss is largely due to premature migration of ions as the battery gradually heats up.)
