Solar thermal collectors can also be considered legendary based on the type of heat transfer liquid and
their construction used (water, non-freezing liquid, air, or heat transfer fluid) and whether they are
covered or uncovered. Solar flat plate collectors are used for water heating applications and the
efficiency of these systems are around 70% which is very high as compared to solar direct energy
conversion systems having efficiency around 17% [13].These collectors are useful for domestic
applications, space heating and industrial low temperature applications. Currently a large number of
solar collectors are available on the market based on concentrating solar power (CSP) systems which
use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam, which is
2418 P.K. Nagarajan et al. / Energy Procedia 61 ( 2014 ) 2416 – 2434
then used as a heat source for a conventional power plant. Extensive ranges of concentrating technologies
developed are the parabolic trough, the concentrating linear Fresnel reflector, the concentrating Sterling
dish and the solar power tower collectors. Recently, the solar thermal configuration system combined
with the emerging technologies of nanofluids and different nano particle suspensions to develop an
innovative approach of nanofluid based solar collectors.