Hybrid Nanofluids in Solar Thermal Collectors: Size and Cost Reduction Opportunities

Solar thermal collector, an alternative way to harvest renewable solar energy, requires high heat transfer area. Hybrid nanofluid has potential to reduce the size of the collector due to its high thermal conductivity and low specific heat capacity. This study investigates the effects of Multi-Walled Carbon Nanotubes (MWCNT) combine with metal oxides, including Al₂ O₃, CeO₂, TiO₂, ZnO at the volume ratio of 1:4 between MWCNT and metal oxides with a total of 1 vol.% in water. The investigation focuses on assessing this nanofluids with 1 kg/min mass flow rate for its effect in size and cost reduction. Following the validation of nanofluids properties predictor and the numerical model of flat plate solar collector with experimental data, the original size of collector is calculated to be 1.51 m². The effects in terms of size and cost reduction are evaluated. In best case scenario, the use of MWCNT-TiO₂ can reduce the size of flat plate solar thermal collector by up to 8.54% and cost by 5.15% compared to using water as the heat transfer fluid.