In this article

Cu-H2O

Co-H2O

MWCNT-H2O nanofluids were prepared through two-step method. The transmittance of nanofluids over solar spectrum (250 to 2500nm) was measured by the UV-Vis-NIR spectrophotometer based on integrating sphere principle. The factors of various particle size

mass fraction and optical path influencing transmittance of nanofluids were investigated. The experimental results show that the transmittance of the three nanofluids is much less than that of deionized water. The transmittance decreased with the nanoparticle size and mass fraction increasing

but increased with the optical path length reducing. With the same mass fraction

the transmittance of MWCNT-H2O nanofluids is the minimum. The transmittance of Co-H2O nanofluids is higher than that of Cu-H2O during 250～775nm wavelength

while inverse during 775～1370nm wavelength. It indicates that different particle has diverse light absorption properties during different wavelength.