Nanofluids poses the following advantages as compared to conventional fluids which makes them suitable for use in solar collectors:
*Absorption of solar energy will be maximized with change of the size, shape, material and volume fraction of the nanoparticles.
*The suspended nanoparticles increase the surface area but decrease the heat capacity of the fluid due to the very small particle size.
*The suspended nanoparticles enhance the thermal conductivity which results improvement in efficiency of heat transfer systems.
*Properties of fluid can be changed by varying concentration of nanoparticles.
*Extremely small size of nanoparticles ideally allows them to pass through pumps.
*Nanofluid can be optically selective (high absorption in the solar range and low emittance in the infrared.
The fundamental difference between the conventional and nanofluid-based collector lies in the mode of heating of the working fluid. In the former case the sunlight is absorbed by a surface, where as in the latter case the sunlight is directly absorbed by the working fluid (through radiative transfer). On reaching the receiver the solar radiations transfer energy to the nanofluid via scattering and absorption.