%0 Journal Article
%A Todd P Otanicar
%A Patrick E Phelan
%A Ravi S Prasher
%A others others
%B J. Renewable Sustainable Energy
%D 2010
%G eng
%I aip.scitation.org
%R 10.1063/1.3429737
%T Nanofluid-based direct absorption solar collector
%8 05/2010
%X <p>Solar energy<span>&nbsp;is one of the best sources of renewable energy with minimal environmental impact. Direct&nbsp;</span>absorption<span>&nbsp;</span>solar collectors<span>&nbsp;have been proposed for a variety of applications such as water heating; however the efficiency of these collectors is limited by the&nbsp;</span>absorptionproperties<span>&nbsp;of the working fluid, which is very poor for typical fluids used in&nbsp;</span>solar collectors.<span>It has been shown that mixing&nbsp;</span>nanoparticles<span>&nbsp;in a liquid (nanofluid) has a dramatic effect on the liquid thermophysical&nbsp;</span>properties<span>&nbsp;such as&nbsp;</span>thermal conductivity.<span>&nbsp;</span>Nanoparticles<span>&nbsp;also offer the potential of improving the radiative&nbsp;</span>properties<span>&nbsp;of liquids, leading to an increase in the efficiency of direct&nbsp;</span>absorption<span>&nbsp;</span>solar collectors.<span>&nbsp;Here we report on the experimental results on&nbsp;</span>solar collectors<span>&nbsp;based on nanofluids made from a variety of&nbsp;</span>nanoparticles<span>&nbsp;(carbon nanotubes, graphite, and&nbsp;</span>silver).<span>&nbsp;We demonstrate efficiency improvements of up to 5% in solar thermal collectors by utilizing nanofluids as the&nbsp;</span>absorption<span>&nbsp;mechanism. In addition the experimental data were compared with a numerical&nbsp;</span>model<span>&nbsp;of a&nbsp;</span>solar collector<span>&nbsp;with direct&nbsp;</span>absorption<span>&nbsp;nanofluids. The experimental and numerical results demonstrate an initial rapid increase in efficiency with volume fraction, followed by a leveling off in efficiency as volume fraction continues to increase.</span></p>