Engineering:Hydrogen bromine battery

A Hydrogen bromine battery is a rechargeable flow battery in which HBr serves as the system’s electrolyte. During the charge cycle, as power flows into the stack, H₂ is generated and stored in a separate tank. An additional product of the chemical reaction is HBr₃, which is also an electrolyte and is mixed in the same tank as the HBr. During the discharge cycle H₂ is consumed and energy is generated. The H₂ is combined again with the HBr₃ and the system returns to its initial stage with a full tank of HBr. The electrolyte suffers no degradation during the process and the system is self contained with no emissions. The first scaled up version of this battery, a 50KW/100KWh system, has been deployed in Rotem Industrial Park in Israel. A beta commercial system, sized at 150KW/900KWh, is to be deployed in June 2016 by a consortium including AREVA, Schneider Electric and EnStorage.

The main advantage of the battery is its cost. Bromine is inexpensive, with more than 400,000 tons produced annually worldwide. The cost of the electrolyte is about $20/kWh. Additional advantages include the use on inexpensive membranes and high power density relative to other flow batteries.

A different approach of the battery relies on laminar flow to separate the two materials instead of a membrane, reacting liquid bromine with hydrogen gas to generate electricity. The first such battery pumped bromine over a graphite cathode and hydrobromic acid under a porous anode, along with hydrogen gas. The device operated at room temperature with a maximum power density of 0.795 watts of per square cubic centimeter. Observed performance matched the predictions of a mathematical model that described the chemical reactions. No membranless system has been scaled up, mainly due to balance of plant complexity matters.

Bromine is relatively inexpensive, with more than 243,000 tons produced annually in the U.S. Operation without a membrane reduces cost and increases battery lifetime.

Applications

HBr Redox Flow batteries are optimal for applications that require daily discharge cycles for long duration discharge periods (i.e. 6–12 hours per day) for a relatively long deployment (i.e. 10–20 years). Typical applications would include integration of renewables, deferral of infrastructure investment, peak management and micro grids.

Specifically for renewables, low-cost energy storage is required to enable renewable energy sources with varying and even intermittent output, such as solar and wind power. The storage buffers the varying output of the renewable source, allowing such sources to be considered baseline power. Among the disadvantages of a H2-Br2 flow battery are low energy density (less than that of lithium-ion batteries) and a complex balance of plant. These drawbacks prevent the use of H2-Br2 flow batteries in transportation applications. The next stage in the development of hydrogen-bromine flow battery is hydrogen-bromate flow battery.

"Performance Evaluation of a Regenerative Hydrogen-Bromine Fuel Cell", Haley Kreutzer, Venkata Yarlagadda and Trung Van Nguyen, J. Electrochem. Soc. 2012 volume 159, issue 7, F331-F337

References

• Tolmachev, Yuriy V.; Piatkivskyi, Andrii; Ryzhov, Victor V.; Konev, Dmitry V.; Vorotyntsev, Mikhail A. (2015). "Energy cycle based on a high specific energy aqueous flow battery and its potential use for fully electric vehicles and for direct solar-to-chemical energy conversion". Journal of Solid State Electrochemistry 19 (9): 2711–2722. doi:10.1007/s10008-015-2805-z. 
• Mody, Cyrus C.M. (2016). "The little-known history of Jack Kilby's misadventure in solar power". IEEE Spectrum 53 (10): 50–55. doi:10.1109/MSPEC.2016.7572539.