Published on October 11th, 2017 | by Steve Hanley0
Sulfur Battery Promises Less Expensive Grid Scale Storage Solution
October 11th, 2017 by Steve Hanley
You can take this story with a grain of salt, literally and figuratively. Researchers at MIT, responding to a challenge issued by the US Department of Energy, have developed a new battery for use by utility companies to store electricity that costs 100 times less than the conventional lithium ion batteries in use today.
The new battery uses sulfur, air, water, and salt — all readily available materials that are cheap to buy. The new battery has store twice as much energy as a typical lead acid battery. Their research was published for the first time on October 11 by energy journal Joule.
“It has become increasingly clear that in order for renewable energy to become the main part, if not all, of our electricity generation system, it needs to match the output of the demand that we have as a society,” says senior author Yet-Ming Chiang of MIT’s Department of Materials Science and Engineering. “We think that this work helps move us in the right direction and creates more hope that this is possible, but we need to push it ahead very quickly because we don’t have a lot of time.”
The announcement comes at a critical time, as many Caribbean islands devastated by two major hurricanes this year are struggling to rebuilt their electrical generation and distribution infrastructure.
Under the leadership of former Energy Department head Steven Chu, the Joint Center for Energy Storage Research set a goal of reducing grid storage battery costs by a factor of five while increasing energy density also by a factor of five and all within five years.
The current costs for the raw materials for lithium ion batteries range from $10 to $100 per kilowatt-hour, largely due to the fact that some of them have to be mined and shipped from sources scattered around the globe to battery manufacturing facilities.
Chiang and his colleagues decided to focus their attention on using sulfur for the cathode of their experimental battery and water as the electrolyte. “We went on a search for a positive electrode that would also have exceptionally low cost that we could use with sulfur as the negative electrode,” Chiang says.
“Through an accidental laboratory discovery, we figured out that it could actually be oxygen, and therefore air. We needed to add one other component, which was a charge carrier to go back and forth between the sulfur and air electrode, and that turned out to be sodium.” The total chemical cost of their proposed battery is roughly $1 per kilowatt-hour.
Since all the chemical components of the battery are dissolved in water, the researchers decided to use a flow battery architecture. In a flow battery, a system of of pumps and tubes causes the components of the battery to flow past each other, generating chemical reactions that help it capture electrons.
Flow batteries tend to be bulky, but size is less important for batteries that will be mounted outdoors than it would be for a battery that needs to be squeezed into the chassis of a vehicle. In most cases, the greatly reduced costs of materials will more than make up for any increase in size.
“We hope to get the community thinking more about long-duration storage, which we’ll need more of as we reach higher penetration of renewables onto the energy grid,” Chiang says. “For example, there are seasonal variations, and we’ll have to figure out how to deal with that. Up until now, electrochemical storage is not the first thing that people think about to accommodate that seasonal variation, just because the cost of it is so high.”
As with all battery research news these days, the MIT project is still in the laboratory stage. The sulfur-oxygen-salt battery under development currently has a useful life of 1500 hours — far less than the 20-year lifespan needed to attract commercial interest in the technology. The researchers have a long way to go yet, but the prospect of ultra low cost grid storage makes their quest worthwhile.
Sergio Marchionne, the CEO of Fiat Chrysler, told the press last week that the world should go slow on its push to build more electric cars because much of the electricity need to recharge them comes from coal fired generating plants with large amounts of carbon emissions. But low cost grid storage could lead to abundant, inexpensive zero emissions renewable energy so the world can use as many electric cars as it wants.
Just as solar panel prices are tumbling, with luck and assistance from researchers like Professor Chiang, the price of battery storage will also start coming down dramatically in the near future.