EDITOR’S NOTE: While there has been a flurry of attention in recent days spurred by Tesla’s announcement that it was going to accelerate widespread deployment of its battery technology, some scientists believe the future of energy storage lies in a different direction. The Energy Times recently caught up with MIT Professor Don Sadoway at the IHS CERAWeek conference and discussed his work on a liquid metal battery.
ENERGY TIMES: Is the new battery technology you have been working on ready for use?
SADOWAY: The first deployment is going to be at a military base on Cape Cod. As you can imagine, the first ones are going to be prohibitively expensive because you’ve got to amortize all of the front-end costs. Down the road we expect to be able to get these things down to the price point of the electricity market.
ENERGY TIMES: How long? Two years or 10 years?
SADOWAY: Closer to two than 10. It depends what we learn from these first deployments. It’s got to be low cost to acquire and it’s got to have a long service lifetime. If we get that product, the demand will assert itself.
ENERGY TIMES: How long will the batteries last?
SADOWAY: The battery could have a full discharge once a day, every day for 10 years, and still have over 99 percent of the main plate capacity. Thing doesn’t fail because it fatigues itself.
ENERGY TIMES: What has been the history of the research effort?
SADOWAY: I was a first round winner of $7 million of ARPA-E funding for research. In addition, I had money from Total, a big French energy company. I put together a team of 20 people, and for three years we worked on a new liquid metal battery. We formed a company, Ambri. There’s about 50 people working at Ambri now, which is five years old. We’re due to get our first prototypes in the field by the end of the year. Our first investor was Bill Gates. We’ve gone through three rounds of funding and raised about $60 million.
ENERGY TIMES: How does the battery work?
SADOWAY: It’s all liquid. Most batteries have two plates that are the electrodes and the liquid is the electrolyte. I reasoned that if we were going to make something that’s going to have a long service lifetime and not wear out in several years, I had to get around all of the breakdown mechanisms that occur inside solid electrodes. We’ve got three liquid layers. Think of it as salad oil and vinegar. The top layer is a low density metal from the northwest part of the periodic table - things like magnesium, sodium or lithium. The bottom layer is a semi-metal like lead, antimony or bismuth. In between is molten salt.
ENERGY TIMES: This is really a tank.
SADOWAY: Yes it’s essentially a tank. You have to isolate the top layer from the bottom layer, otherwise it will short. The way the battery operates is the metal on the top wants to alloy with the metal on the bottom – and it does so by shooting current through the external circuit. The top layer gets thinner and thinner and the bottom layer gets thicker and thicker. And then when we want to charge the battery we push current through the battery and then electro-refine the metal out of the bottom and reform the top layer.
ENERGY TIMES: Out in the field, do you see banks of these or just one large one?
SADOWAY: No, it’s banks because if you try to make one large one it would be very unwieldy. We’ve got something that would be suitable for, say, a subdivision. It would be a footprint of a 53-foot trailer and it would be big enough for 2 megawatt-hours, or 500 kilowatts, drained over 4 hours. This battery operates at around 500 degrees centigrade, has insulation around it and is cool to the touch.
ENERGY TIMES: Is it ready for prime time?