Energy harvesting from liquid cooling systems using thermo-electrochemical flow cells

Abstract

We report a flow thermocell that is integrated into liquid cooling systems to convert the temperature difference between hot and cold pipes into electrical energy. This flow thermocell uses porous Ni foam electrodes that are inserted into the pipes carrying heated and cooled fluids. An aqueous ferricyanide/ferrocyanide electrolyte is used as a coolant fluid to generate electricity through thermally driven redox reactions on the electrodes. The power generation capability of the fabricated device is evaluated for operating conditions. As the flow rate of electrolytes having a temperature difference of 22 °C increase from 0.3 to 1.5 mL/s, the power density increase from 0.129 to 0.208 mW/cm2 owing to the reduction in the mass transport overpotential for power generation, and a Carnot-relative efficiency of 0.304% is obtained at an optimal flow rate of 1.2 mL/s. The efficiency can be further increased to 0.50% by reducing the heat loss from heated to cooled electrolytes with increasing the inter-electrode spacing. The efforts provide here to optimize the design and performance of flow thermocells would be useful in devising new active cooling systems that incorporate the ability to harvest heat flow in liquid cooling systems into electrical energy while simultaneously performing liquid cooling.