Thermally Regenerable Redox Flow Battery.

The efficient production of energy from low-temperature heat sources (below 100 °C) would open the doors to the exploitation of a huge amount of heat sources such as solar, geothermal, and industrial waste heat. Thermal regenerable redox-flow batteries (TRBs) are flow batteries that store energy in concentration cells that can be recharged by distillation at temperature <100 °C, exploiting low-temperature heat sources. Using a single membrane cell setup and a suitable redox couple (LiBr/Br2 ), a TRB has been developed that is able to store a maximum volumetric energy of 25.5 Wh dm-3 , which can be delivered at a power density of 8 W m-2 . After discharging 30 % of the volumetric energy, a total heat-to-electrical energy conversion efficiency of 4 % is calculated, the highest value reported so far in harvesting of low-temperature heat.