STTR Phase I: Hydrogen Bromine Electrolysis for Highly Efficient Hydrogen-Based Energy Storage and High Value Chemical Applications

The broader impact/commercial potential of this project includes applications ranging from peak load shifting, grid buffering for renewable energy input, frequency regulation, and chemical conversions. As the percentage of energy from renewables on the grid increases, energy storage will be essential to stabilize the supply and demand. Currently, 20-40% of wind energy is often stranded due to the inability to capture the energy in the peak generation periods. Germany, Europe, Japan, Korea, and other countries are funding significant efforts in energy storage projects. Energy storage is also a critical need for all of the United States armed services, including microgrids for forward operating bases and other off grid installations. While batteries can demonstrate very good round trip efficiencies, they suffer from self-discharge, capacity fade, and high cost. Flow batteries separate the reactant and product storage from the electrode active area, enabling higher capacities through merely adding more storage. Many systems have not been practical in the past due to low energy density values, but fuel cell and electrolysis developments have provided pathways to higher energy density. Advances in these areas would find immediate commercial interest, and address key strategic areas related to energy security and grid stabilization. This Small Business Technology Transfer Phase I project addresses the present technology gaps in flow battery cell stack design to enable a reliable, efficient, high rate hydrogen-bromine flow battery for energy storage applications. The goal of this project is a proof of concept hydrogen bromide stack that operates at a practical hydrogen storage pressure in electrolysis mode, while providing acceptable energy density in fuel cell mode. The majority of hydrogen bromine flow battery research to date has focused on the discharge reaction, leading to material choices that may not be practical for the charging mode. This project will demonstrate feasibility of sealing and supporting thin membranes to practical storage pressures. Objectives include demonstration of differential pressure electrolysis with materials that can support high power fuel cell mode, determining the bromine/bromide crossover rates as a function of hydrogen back pressure, and exploring compatible materials for the full flow battery system. Going beyond the Phase I funded effort, research being planned will include cell stack design optimization, down-selection of appropriate materials, and prototype system development for charge battery cycling. The anticipated result will be a highly efficient flow battery system with durability in charge mode and high power density in discharge mode for a cost effective energy storage system.