A team at U.S Government Northwest National Laboratory has developed a new flow battery. Apparently this uses a readily available chemical common in water-treatment plants, and could be ideal for intermittent renewable energy. Innovation News advises that these earth-abundant iron-based flow batteries withstand 1,000 cycles, while retaining 98.7% capacity.
How Flow Batteries Work to Store and Release Energy
A flow battery comprises two chambers with a membrane between them. Each chamber has a different liquid containing active chemical agents. Ions exchange through the membrane between them as the liquids circulate.
Flow batteries are a robust solution, potentially able to generate grid-scale energy when connected to suitable external circuits. However, their power-to-weight and power-to-volume ratios have been too low to make this feasible.
New Earth-Abundant Iron-Based Flow Batteries
The team at Pacific Northwest National Laboratory (see link below) came up with a novel solution. Innovation News Network explains how they added a neutral-pH phosphate-based energy carrier to a liquid containing charged iron.
Their additive was a material called nitrilotri-methylphosphonic acid, or NTMPA for short. This material is readily available at commercial scale, and commonly helps prevent corrosion in water-treatment plants.
“We were looking for an electrolyte that could bind and store charged iron in a liquid complex at room temperature, and mild operating conditions with neutral pH,” a senior report author explains. “We are motivated to develop battery materials that are earth-abundant and can be sourced domestically.”
Safer Earth-Abundant Iron-Based Flow Batteries
These earth-abundant iron-based flow batteries from Pacific Northwest National Laboratory could replace lithium-ion cells in urban areas. This might be more acceptable to communities concerned about battery farm fires there.
However, at this stage the Pacific Northwest prototype still lags behind proven alternatives. “Our voltage output is lower than the typical vanadium flow battery output,” the team concedes. “We are working on ways to improve that.”
More Information
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