3.2 Application of Nanofluids in Solar Collectors
For energy applications, two remarkable properties of nanofluids are utilized, one is the thermo-physical
properties of nanofluids, enhancing the heat transfer and another is the application of nanofluids in solar
collectors. The conventional direct absorption solar collector is a well-established technology, and it has
been proposed for a variety of applications. However, the efficiency of these collectors is limited by the
absorption properties of the working fluid. This technology has been combined with the emerging
nanofluids technologies prepared by liquid-nanoparticle suspensions. The previous researchers review by
Omid mahian et.al [44] gives a noble awareness about enhanced the efficiency and performance of the
solar thermal system, solar water heater, thermal energy storage, solar cells and solar stills, there is a very
limited number of research works in the area of solar collectors augmented with nanofluids. Basically,
low temperature nanofluids based direct absorption solar collectors (DASC) were investigated
theoretically by Tyagi et.al [45]. They studied Al2O3 water based nanofluids was used for the
investigation where the particle volume fraction (0.1% to 5%) influenced the collectors efficiency.
Significant increase in the collector’s efficiency was observed not only varying the particles volume
fraction, but also the glass cover transmissivity & collector height. It is reported, efficiency increases by
8% for volume fraction ranging from 0.8% to 1.6% and the effect of size of nano particles in increasing
efficiency is marginal.Taylor et.al [46] investigated experimentally, by using graphite/ therminol VP-1 nanofluids for 10-
100MW solar power tower collectors and observed potential improvement in efficiency. Theoretically
10% in efficiency can be observed when compared with the conventional solar collectors, when using
solar concentration ratio of 10-1000. Experimental results shown that 5-10% increase in efficiency can be
achieved while using the nanofluids in the receiver section. The authors also estimated that $3.5
million/year more revenue can be attained by proper implementation.