Experimental investigation on the photothermal conversion performance of cuttlefish ink nanofluids for direct absorption solar collectors

As a typical renewable energy source, solar energy is important in addressing current energy challenges. The combination of nanofluids and direct absorption solar collectors is an efficient approach to harness solar energy. This study utilized cuttlefish ink, which is a natural biomass material, to prepare deionized water-based cuttlefish ink nanofluids using a two-step method, and the thermal conductivity and optical properties of nanofluids were systematically investigated. The results showed that the addition of cuttlefish ink nanoparticles improves the heat transfer and optical absorption abilities of the base fluid. Furthermore, photothermal conversion experi-ments on cuttlefish ink nanofluids were performed using a solar simulator and natural sunlight. When the mass fraction was 0.02 %, the cuttlefish ink nanofluid achieved a maximum overall photothermal efficiency of 60.2 % under solar simulator irradiation, which was 52.0 % higher than that of deionized water. Moreover, the maximum temperature rise of cuttlefish ink nanofluids under natural sunlight was 33 symbolscript corresponding to an increase of 17.4 symbolscript compared to that of deionized water. Cuttlefish ink is low-cost, easily available, and envi-ronmentally friendly. This study suggests that cuttlefish ink nanofluids are promising candidates for direct ab-sorption solar collectors systems.