Thermogalvanic bricks: optimising large dimension thermocells for air and water valorisation†

Abstract

Thermogalvanic cells can potentially valorise the huge quantity of energy available as waste heat; using entropy-driven thermoelectrochemistry they can convert a thermal gradient into electricity. Most investigations exploit a thermal source (e.g. hot water, the human body, sunlight, electronics) via a heat exchanger (metal pipe, skin, housing, etc), combined with an unlimited heat sink (e.g. pumped cold water). Limited studies have used ambient air as the heat sink. This study is believed to be the first to explore using air as both the thermal source and heat sink. It compares thermogalvanic cell performance when using water–water and air–air as the thermal energy sources and sinks, respectively, for devices with relatively large physical dimensions (25 to 100 mm wide). Gelation improved power output under both scenarios, due to enhanced thermal isolation of the electrodes; power decreased with increasing width in the water–water setup, but power increased with increasing width for air–air harvesting. Water–water yielded higher power overall, yet the air–air system operated passively and could be further optimised for real-world applications, i.e. as thermogalvanic bricks or panels in building materials.