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Sustainable ‘flow Batteries’ to Store Sun and Wind Energy

I received my Master’s degree in chemical engineering from SU, USA. I worked as a writer and researcher for Fortune 500 company clients.


Renewable energy is environmentally friendly. But how do we use them when the wind doesn't blow and the sun doesn't shine. Flow batteries, which are giant devices can be the answer. The flow batteries work by using liquid electrolyte which is pumped through the electrodes to capture the energy (electrons) from solar panel or turbine. The heated electrolyte liquid is then stored in insulated tanks. In this way, stored chemical energy in the tanks can be converted to electricity for use.

Why Flow Batteries Are The Ideal Solution.

The Lithium-ion batteries which are used in laptops, vehicles providing backup power for offices and towns, have proven to be difficult to scale up for large cities. The flow batteries available today although having the potential, are not big enough to store power for large grid areas. So far the current flow batteries use vanadium metal as electrolyte or fluorinated membranes, which are rare, expensive, toxic, and having short battery life.
In order to power many houses, bigger tanks of electrolytes will be required to store more energy increasing cost. So, We need an affordable, environmentally friendly, scalable, stable battery to store energy efficiently and power many homes for a long time.


Hydrogen Bromine Flow Batteries As Solution.

The high power density and availability of materials make hydrogen bromine flow batteries (HBFB) an ideal solution. However, conventional hydrogen/bromine flow batteries used nowadays consist of expensive materials such as membrane (Nafion), carbon-paper electrodes, and platinum catalysts. Additionally, platinum catalysts tend to get corroded and poisoned with time when exposed to Br2 and HBr. These issues comprise the system's lifetime. In view of this, researchers are encouraged to develop new materials that reduce the cost and increases the durability of H2/Br2 flow batteries. Lawrence Berkeley National Laboratory has come up with new Nafion/ polyvinylidene fluoride electrospun composite membranes showing high selectivity. Moreover, the institute has also developed a new nitrogen-functionalized platinum-iridium catalyst that shows excellent durability and activity in HBr/Br2 environment. Preliminary cost analysis revealed that the new advanced H2/Br2 flow batteries significantly reduce system costs and H2/Br2 flow-battery energy-storage system stack, offer high power, high efficiency, and increased durability.

What Recent Studies Reveal

A research paper reveals the techno-economic analysis of a 500 kW nominal power/5 MWh HBFB storage system, for both the current and a future scenario (2030). Results revealed that HBFB having improved stack performance and reduced stack and system costs could result in around 62% reduction in capital investments. Moreover, the paper reveals that the cost of energy storage presently for a wind-solar storage system is as low as $0.074/kWh, as compared to the high cost of fossil-based power plants. Further, the paper reveals that the cost of energy storage with new HBFB flow batteries can reduce to $0.034/kWh in the future. Also, sensitivity analysis mentions that the cost of storage is sensitive towards the batteries' stack lifetime. To achieve longer stack lifetime researchers must develop ion-exchange membranes with improved selectivity and advanced electrocatalysts with higher durability.

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The findings of the new Nafion/ polyvinylidene fluoride electrospun composite membranes in the hydrogen bromine batteries developed by Lawrence Berkeley National Laboratory offer a potential solution to the issues of having a good life long stable membrane.

Other studies by Berkeley Lab offer the potential of large-scale development of affordable membrane technology from polymers called AquaPIMs. Generally, the grid battery is designed with chemistries that have alkaline electrodes. However, the present membrane technologies are intended for acidic chemistries. The new AquaPIM membrane proves to work well in alkaline conditions by avoiding collapsing, showing high structural stability, staying conductive throughout the performance period. In comparison with the fluorinated polymer membranes, the new polymers offer long-lasting, scalable, and low-cost grid batteries.
Moreover, experimental results reveal that the new class of polymer membranes show good performance, easy compatibility, and forms stable alkaline cells with commonly available materials like zinc, iron, and water for anode and cathode.

The AquaPIM membranes find a huge scope of application in aqueous flow battery chemistries, metals, inorganics, and organics. The researchers also predict that these new polymer membranes could be compatible with batteries that use either manganese oxide, oxygen, or metal-organic frameworks as the cathode.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2021 Nikita Nandakumar Thattamprambil

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