A brand new kind of gas cell that runs on sodium steel might at some point assist clear up sectors the place it’s tough to switch fossil fuels, like rail, regional aviation, and short-distance transport. The machine represents a departure from applied sciences like lithium-based batteries and is extra related conceptually to hydrogen gas cell techniques.
The sodium-air gas cell was designed by a crew led by But-Ming Chiang, a professor of supplies science and engineering at MIT. It has the next power density than lithium-ion batteries and doesn’t require the super-cold temperatures or excessive pressures that hydrogen does, making it probably extra sensible for transport. “I’m excited by sodium steel as an power service of the long run,” Chiang says.
The machine’s design, printed immediately in Joule, is said to the expertise behind certainly one of Chiang’s corporations, Type Power, which is constructing iron-air batteries for giant power storage installations like people who might assist retailer wind and solar energy on the grid. Type’s batteries depend on water, iron, and air.
One technical problem for metal-air batteries has traditionally been reversibility. A battery’s chemical reactions have to be simply reversed in order that in a single route they generate electrical energy, discharging the battery, and within the different electrical energy goes into the cell and the reverse reactions occur, charging it up.
When a battery’s reactions produce a really steady product, it may be tough to recharge the battery with out shedding capability. To get round this drawback, the crew at Type had discussions about whether or not their batteries could possibly be refuelable reasonably than rechargeable, Chiang says. The thought was that reasonably than reversing the reactions, they might merely run the system in a single route, add extra beginning materials, and repeat.
Finally, Type selected a extra conventional battery idea, however the concept caught with Chiang, who determined to discover it with different metals and landed on the concept of a sodium-based gas cell.
On this gas cell format, the machine takes in chemical compounds and runs reactions that generate electrical energy, after which the merchandise get eliminated. Then contemporary gas is put in to run the entire thing once more—no electrical charging required. (You would possibly acknowledge this idea from hydrogen gas cell autos, just like the Toyota Mirai.)
Chiang and his colleagues got down to construct a gas cell that runs on liquid sodium, which might have a a lot increased power density than present industrial applied sciences, so it could be small and light-weight sufficient for use for issues like regional airplanes or short-distance transport.
GRETCHEN ERTL/MITTR
The analysis crew constructed small take a look at cells to check out the idea and ran them to point out that they might use the sodium-metal-based system to generate electrical energy. Since sodium turns into liquid at about 98 °C (208 °F), the cells operated at reasonable temperatures of between 110 °C and 130 °C (or 230 °F and 266°F), which could possibly be sensible to be used on planes or ships, Chiang says.
From their work with these experimental units, the researchers estimated that the power density was about 1,200 watt-hours per kilogram (Wh/kg). That’s a lot increased than what industrial lithium-ion batteries can attain immediately (round 300 Wh/kg). Hydrogen gas cells can obtain excessive power density, however that requires the hydrogen to be saved at excessive pressures and sometimes ultra-low temperatures.
“It’s an fascinating cell idea,” says Jürgen Janek, a professor on the Institute of Bodily Chemistry on the College of Giessen in Germany, who was not concerned within the analysis. There’s been earlier analysis on sodium-air batteries previously, Janek says, however utilizing this type of chemistry in a gas cell as an alternative is new.
“One of many important points with one of these cell idea is the protection concern,” Janek says. Sodium steel reacts very strongly with water. (You will have seen movies the place blocks of sodium steel get thrown right into a lake, to dramatic impact). Requested about this concern, Chiang says the design of the cell ensures that water produced throughout reactions is constantly eliminated, so there’s not sufficient round to gas dangerous reactions. The stable electrolyte, a ceramic materials, additionally helps forestall reactions between water and sodium, Chiang provides.
One other query is what occurs to one of many cell’s merchandise, sodium hydroxide. Generally generally known as lye, it is an industrial chemical, utilized in merchandise like liquid drain-cleaning answer. One of many researchers’ strategies is to dilute the product and launch it into the environment or ocean, the place it could react with carbon dioxide, capturing it in a steady type and stopping it from contributing to international warming. There are teams pursuing discipline trials utilizing this precise chemical for ocean-based carbon elimination, although some have been met with controversy. The researchers additionally laid out the potential for a closed system, the place the chemical could possibly be collected and bought as a by-product.
There are financial components working in favor of sodium-based techniques, although it could take some work to construct up the required provide chains. As we speak, sodium steel isn’t produced at very excessive volumes. Nevertheless, it may be constituted of sodium chloride (desk salt), which is extremely low-cost. And it was produced extra abundantly previously, because it was used within the course of of creating leaded gasoline. So there’s a precedent for a bigger provide chain, and it’s doable that scaling up manufacturing of sodium steel would make it low-cost sufficient to make use of in gas cell techniques, Chiang says.
Chiang has cofounded an organization known as Propel Aero to commercialize the analysis. The venture acquired funding from ARPA-E’s Propel-1K program, which goals to develop new types of high-power power storage for plane, trains, and ships.
The following step is to proceed analysis to enhance the cells’ efficiency and power density, and to start out designing small-scale techniques. One potential early utility is drones. “We’d wish to make one thing fly inside the subsequent 12 months,” Chiang says.
“If individuals don’t discover it loopy, I’ll be reasonably disillusioned,” Chiang says. “As a result of if an concept doesn’t sound loopy initially, it in all probability isn’t as revolutionary as you assume. Thankfully, most individuals assume I’m loopy on this one.”