Mechanically refuellable zinc-air battery: A safe and sustainable alternative for large-scale, long-duration energy storage

P4-029-Akhil Kongara

Rising concerns over global warming have motivated scientists to explore various clean energy generation options. In this quest for clean energy generation, renewables like solar and wind have gained significant traction and have seen a tremendous increase in energy generation from these sources over the last decade. However, these renewable sources are intermittent in nature leading to a time gap between energy generation and consumption. This time gap can be either between the day and night or between the seasons, thus varying from a few hours to a few months. Filling this time gap with energy storage is essential to realize the goal of a carbon neutral world and fight global warming. This energy storage technology should be available at low cost per kWh, safe, sustainable and store all the excess renewable energy for a few months with negligible self-discharge. In this poster presentation, we show the potential of zinc-air battery as an alternative battery technology for large-scale and long-duration energy storage and meets most of the above requirements. The charging and discharging can be decoupled and operated simultaneously. This enables excess renewable energy storage as and when it is generated by charging. A zinc charging station was built to recycle zinc oxide discharge product back to zinc for reuse. This work implies that the renewable energy can be used to convert zinc oxide to zinc and stored safely as zinc plates for long duration with very less self-discharge. For discharge, power and energy can be decoupled where energy is stored as zinc plates external to the battery. These zinc plates can be inserted in batteries for discharge upon energy demand. The battery size dictates the power output. A 220 Ah mechanically refuellable zinc-air single cell was designed and fabricated with in-house developed gas diffusion electrodes. The discharge tests confirmed a specific energy of 300 Wh kg^-1 and energy density of 600 Wh l^-1
at module level. Six of these cells were used to make a 1.3 kWh module whose refuelling time is less than 5 minutes.