Applicability of graphite nanofluids in direct solar energy absorption

Applications of nanofluids in direct absorptions of solar radiation in volumetric solar collector have been investigated in this research. Radiative transport equations along with mass, momentum and energy equations are solved together to simulate operating characteristics of direct absorption solar collector. Different diameter and volume fractions of graphite nanoparticles are investigated and for each case, efficiency of solar receivers in absorption of solar energy, impacts on the harvested solar energy, irradiation spectrum distribution and irradiation energy level versus the depth of the flow have been studied. Moreover, for a proposed low-temperature solar collector, increase in outlet temperature, convective losses, and costs are evaluated. Results of this study show that by using graphite nanofluids having volume fraction around 0.000025%, it will be possible to absorb more than 50% of incident irradiation energy by just about 0.0045 $/L increase in cost, while pure water solar collector can only absorb around 27% of incident irradiation energy. (C) 2013 Elsevier Ltd. All rights reserved.