Experimental investigation of using ZnO nanofluids as coolants in a PEM fuel cell

In this paper we report on an experimental study conducted on the thermo-electrical performance of a small-scale (i.e. 2.4 kW) Proton Exchange Membrane Fuel Cell (PEMFC), in which both conventional 50/50 water-Ethylene Glycol (EG), and 50/50 water-EG based ZnO nanofluids were used as coolants. PEMFCs are a promising alternative to Internal Combustion Engines (ICEs) for automotive applications. However, among other challenges, the large-sized cooling system of PEMFCs (i.e. the radiator) imposes a great challenge for this application. Using nanofluids as coolants has the potential to address this challenge. Employing selected nanofluids as coolants, with maximum 0.5 vol% nanoparticle concentration, showed no change in the electrical power outputs of the stack based on its polarisation curve, whereas the cooling capacity of the system was improved 29% compared with that while using 50/50 water-EG as coolant. The experimental investigation reported here confirmed the earlier theoretical finding that the frontal area of the radiator (i.e. used for fuel cell cooling) could be reduced by about 27% when nanofluids (0.5 vol%) replaced conventional EG/water coolants. Using 0.5 vol% ZnO nanofluid also showed just less than 10% increase in the pumping power compared to when the conventional 50/50 water-EG was used as coolant. It is concluded in this study that up to 0.5 vol% ZnO nanofluid can be applied to the PEMFC cooling system without affecting any electrical performance of the system.