An energy-storage solution that flows like soft-serve ice cream

Dec 1, 2021 04:37 PM ET
  • Batteries made from an electrically conductive combination the consistency of molasses might help fix a critical piece of the decarbonization puzzle.
An energy-storage solution that flows like soft-serve ice cream
Image: Thaneer Narayanan

An interdisciplinary group from MIT has located that an electrochemical technology called a semisolid flow battery can be a cost-competitive type of energy storage space and back-up for variable renewable energy (VRE) resources such as wind and solar. The group's study is described in a paper published in Joule.

" The shift to clean energy needs energy storage space systems of different durations for when the sunlight isn't radiating and the wind isn't blowing," says Emre Gençer, a research study researcher with the MIT Energy Initiative (MITEI) and also a member of the team. "Our work shows that a semisolid flow battery could be a lifesaving in addition to affordable alternative when these VRE sources can't create power for a day or longer-- when it comes to natural calamities, as an example."

The rechargeable zinc-manganese dioxide (Zn-MnO2) battery the scientists created defeated other long-duration energy storage space contenders. "We did a detailed, bottom-up evaluation to understand exactly how the battery's composition influences performance and price, considering all the compromises," says Thaneer Malai Narayanan SM '18, Ph.D. '21. "We showed that our system can be less costly than others, and can be scaled up."

Narayanan, that performed this work at MIT as part of his doctorate in mechanical engineering, is the lead author of the paper. Added writers include Gençer, Yunguang Zhu, a postdoc in the MIT Electrochemical Energy Lab; Gareth McKinley, the School of Engineering Professor of Teaching Innovation and professor of mechanical engineering at MIT; and Yang Shao-Horn, the JR East Professor of Engineering, a professor of mechanical engineering and also of materials science and also engineering, and a member of the Lab of Electronics (RLE), who directs the MIT Electrochemical Energy Lab.

Going with the flow

In 2016, Narayanan began his graduate studies, signing up with the Electrochemical Energy Lab, a hotbed of research study and also exploration of solutions to reduce environment modification, which is centered on cutting-edge battery chemistry as well as decarbonizing gas and also chemicals. One amazing chance for the lab: creating low- as well as no-carbon backup energy systems appropriate for grid-scale needs when VRE generation flags.

While the lab cast a broad net, checking out energy conversion as well as storage making use of strong oxide gas cells, lithium-ion batteries, and metal-air batteries, to name a few, Narayanan took a particular rate of interest in flow batteries. In these systems, two various chemical (electrolyte) solutions with either unfavorable or positive ions are pumped from separate containers, meeting across a membrane (called the stack). Below, the ion streams respond, transforming electrical energy to chemical energy-- basically, billing the battery. When there is demand for this stored energy, the solution obtains pumped back to the stack to convert chemical energy right into electric energy once more.

The duration of time that flow batteries can discharge, launching the kept electrical power, is determined by the volume of favorably and also adversely charged electrolyte solutions streaming via the stack. Theoretically, as long as these solutions maintain flowing, responding, and transforming the chemical energy to electric energy, the battery systems can offer electrical power.

" For backup lasting greater than a day, the design of flow batteries recommends they can be an affordable option," says Narayanan. "You recharge the solution in the containers from sun as well as wind power sources." This makes the entire system carbon cost-free.

Yet while the pledge of flow battery innovations has actually beckoned for at the very least a decade, the unequal efficiency and expense of materials needed for these battery systems has actually reduced their application. So, Narayanan set out on an enthusiastic journey: to create and develop a flow battery that can back up VRE systems for a day or even more, saving as well as discharging energy with the same or higher effectiveness than backup rivals; as well as to identify, with extensive expense analysis, whether such a system might verify economically feasible as a long-duration energy choice.

Multidisciplinary collaborators

To strike this multipronged challenge, Narayanan's project combined, in his words, "three giants, scientists all widely known in their fields": Shao-Horn, who specializes in chemical physics as well as electrochemical scientific research, and also design of products; Gençer, who creates comprehensive financial versions of emergent energy systems at MITEI; and McKinley, a professional in rheology, the physics of flow. These three likewise worked as his thesis experts.

" I was delighted to operate in such an interdisciplinary team, which used an one-of-a-kind possibility to develop an unique battery design by designing charge transfer and also ion transport within flowable semi-solid electrodes, and to guide battery engineering utilizing techno-economics of such flowable batteries," says Shao-Horn.

While various other flow battery systems in opinion, such as the vanadium redox flow battery, use the storage capacity and also energy density to support megawatt and larger power systems, they depend on costly chemical active ingredients that make them negative bets for long period of time objectives. Narayanan got on the hunt for less-pricey chemical elements that likewise include rich energy capacity.

Via a series of bench experiments, the scientists came up with a novel electrode (electrical conductor) for the battery system: a blend including spread manganese dioxide (MnO2) particles, shot through with an electrically conductive additive, carbon black. This substance responds with a conductive zinc solution or zinc plate at the stack, making it possible for reliable electrochemical energy conversion. The liquid properties of this battery are much eliminated from the watery solutions utilized by various other flow batteries.

" It's a semisolid-- a slurry," claims Narayanan. "Like thick, black paint, or possibly a soft-serve ice cream," suggests McKinley. The carbon black includes the pigment and also the electrical punch. To arrive at the optimal electrochemical mix, the scientists modified their formula many times.

" These systems have to be able to flow under sensible pressures, however also have a weak return stress and anxiety so that the energetic MnO2 bits do not sink to the bottom of the flow storage tanks when the system isn't being utilized, in addition to not separate into a battery/oily clear fluid stage and a thick paste of carbon bits and MnO2," claims McKinley.

This series of experiments educated the technoeconomic analysis. By "attaching the dots between composition, efficiency, as well as price," claims Narayanan, he and also Gençer had the ability to make system-level price and also effectiveness calculations for the Zn-MnO2 battery.

" Analyzing the expense as well as efficiency of early innovations is very difficult, as well as this was an example of how to establish a basic technique to aid researchers at MIT and also somewhere else," says Gençer. "One message right here is that when you consist of the price evaluation at the advancement stage of your speculative work, you obtain a vital early understanding of your project's expense effects."

In their last round of researches, Gençer and Narayanan compared the Zn-MnO2 battery to a set of comparable electrochemical battery as well as hydrogen back-up systems, looking at the capital expenses of running them at periods of eight, 24, as well as 72 hours. Their searchings for stunned them: For battery discharges longer than a day, their semisolid flow battery vanquished lithium-ion batteries and also vanadium redox flow batteries. This held true also when factoring in the hefty cost of pumping the MnO2 slurry from storage tank to stack. "I was unconvinced, and also not expecting this battery would be affordable, once I did the price estimation, it was plausible," claims Gençer.

However carbon-free battery backup is a really Goldilocks-like company: Various scenarios require different-duration solutions, whether an expected over night loss of solar energy, or a longer-term, climate-based disruption in the grid. "Lithium-ion is terrific for backup of eight hours and under, but the products are also costly for longer durations," says Gençer. "Hydrogen is very costly for very short periods, and also good for long durations, and we will require all of them." This suggests it makes good sense to continue working with the Zn-MnO2 system to see where it could fit in.

" The next step is to take our battery system and develop it up," claims Narayanan, that is functioning now as a battery engineer. "Our research study likewise points the way to other chemistries that could be established under the semi-solid flow battery platform, so we could be seeing this kind of modern technology made use of for energy storage in our lifetimes."

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