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Unexpected Development: New Lithium-Sulfur Flow Battery With Revolutionary Features

The search for a solution that makes it possible to dampen the intermittencies of renewable energies is focused, as it is widely known, on alternative battery technologies. A Scottish company has now just developed an alternative that combines the potential of cheap and long-lasting flow batteries, with high energy and volumetric density; allegedly higher than Tesla 4680 cells.


The person responsible for this advanced system is the startup company StorTera, which has developed a unique liquid flow battery that basically has the advantages of lithium technology, high energy and volumetric density on one hand, and on the other hand a fast and reliable response to actual network electricity requirements, with the additional benefits of flow batteries, such as a lower levelized cost of storage, and a technology that produces less waste when recycling.

The result is a lithium sulfur flow battery that achieves an energy density of 250 Wh/L, the highest figure ever achieved by a commercial product. Something that, according to its developers, allows it to replace existing lithium technology in many applications, such as network backup, storage of surplus renewables, etc, while providing a much longer useful life. To give context, Tesla´s 4680 batteries have a cell gravimetric energy density of 244 Wh/kg, and a cell volumetric energy density of 650 Wh/l (according to the Laboratory for Energy Storage and Conversion, which carried out the testing and data analysis).

Tesla Model 3, Courtesy of Tesla Inc.

Just to clarify, “gravimetric energy density” is a measure of the amount of energy stored in a given mass of material, while "volumetric energy density" is a measure of the amount of energy stored in a given space. The StorTera lithium-sulfur flow battery exhibits a much higher volumetric energy density than any other commercial flow battery, some 3.2 times the energy density of Tesla’s current battery technology.

This is a great leap forward for the energy industry, as StorTera´s chair and co-founder, Walt Patterson says: “This is a major breakthrough: what we are bringing to the market is a solution which has been sought after since the start of the industry and will make a real difference to the economics of renewable energy”.

The new battery is also remarkably long-lasting: according to the company, the battery cells they have been testing showed no decrease in energy density up to 25,000 cycles, and no signs of degradation after 30 years of simulated historic cycles. This is impressive, given that current lithium batteries usually have a lifetime of about 10 years; there are experts in the field that are already saying it could potentially be a serious competitor to Tesla Megapacks.

Megapack, courtesy of Tesla Inc.

This new technology is already in the process of being tested in the field. StorTera has already won two Non-Domestic Renewables Obligation (NDRO) projects, in which the company showed the use of its technology for storing energy generated by renewables. It basically provides millisecond response times and up to eight hours of storage based on average settings. In addition, the company indicates that according to its estimates, each pack may last more than 30 years of use, since the commercial model certification will indicate an estimated life of 20 years or 7,500 cycles, at which time the degradation and loss of efficiency indicators "will be minimal".

The system works by pumping a single ionic liquid through its proprietary membrane. The liquid design allows it to enjoy a design with fewer components, which in turn reduces maintenance to a minimum, and while the use of low-cost materials offers a competitive product in economic terms.

The company itself has made cost of capital estimates of approximately $146.20/kW and $91/kWh; which places it slightly above LFP (Lithium-Iron-Phosphate), but below NMC (Lithium-Nickel-Manganese, Cobalt-Oxide) systems and the like. All in all, this is a new alternative that will allow the deployment of large backup battery parks that help mitigate the intermittencies of renewables, and basically help the transition process from using non-renewable sources, such as coal, gas and nuclear, to clean-green technologies.

Source: StorTera

All images courtesy of Tesla Inc.

Nico Caballero is the VP of Finance of Cogency Power, specializing in solar energy. He also holds a Diploma in Electric Cars from Delft University of Technology in the Netherlands, and enjoys doing research about Tesla and EV batteries. He can be reached at @NicoTorqueNews on Twitter. Nico covers Tesla and electric vehicle latest happenings at Torque News.