Augmenting performance of fuel cells using nanofluids

Fuel cells (FCs) have gained increasing attention over the past few years as sustainable energy conversion devices. This is mainly due to their high efficiency which related to the direct conversion of chemical energy into electrical energy (the most desirable energy form). Despite the high-energy conversion efficiency of FC, still substantial part of the produced energy is lost as waste heat, hence, proper cooling is necessary to maintain the optimum operating temperature and integrity of the FC. Different heat transfer fluids (HTFs), with water as the most common, are typically used as coolants for FC. In recent years, nanofluids (NFs) have emerged as high-efficiency HTF with remarkably enhanced thermophysical properties. In this work, the application of NFs for the heat management and waste heat recovery (WHR) in the FCs has been reviewed and discussed. NFs have been proved to be effective coolants for the FCs. The presence of NFs almost doubles the thermal performance of the FCs while decreasing the size of the cooling system. Additionally, NFs found various applications in the different WHR technologies that can be used for FC devices, like absorption chillers, thermoelectricity generator (TEG), and organic Rankine cycle (ORC) enhancing the performance of the FC-based poly-generation systems. For instance, the use of 0.1 vol% Al₂O₃/water-ethylene glycol NF has reduced the heat exchanger size of 2.13 kW proton-exchange membrane FC by about 30%. Moreover, carbon-based NF demonstrated a significant role in improving the performance of microbial FC through the enhancement of the electron transfer between the bulk microorganisms and the anode surface resulting in about a 50% increase in current and power densities.