Nitrogen doped hybrid carbon based composite dispersed nanofluids as working fluid for low-temperature direct absorption solar collectors

Solar energy is the best source of renewable energy among all other natural resources. Due to the abundant availability of solar energy it could effectively be used to fulfil the energy requirement of modern industrial society. Application of nanofluids in Direct Absorption Solar Collectors (DASC) can significantly increase its efficiency. Carbon nanotubes (CNTs) and graphene, that exhibit high thermal conductivity, unique optical properties, good mechanical strength, and large surface area have been of great advantage in the field of nanofluids. In this present work, application of N-(rGO-MWNTs) (nitrogen doped hybrid structure of reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWNTs)) in DASC has been investigated. The absorption and transmittance studies have been carried out by UV-visible-NIR spectrophotometer. Furthermore, temperature dependant thermal conductivity study with different volume fractions has been carried out. A significant enhancement in thermal conductivity of 17.7% is achieved with 0.02% volume fraction in DI water and 15.1% with 0.03% volume fraction with EG. Furthermore, we have observed that these nanofluids have very good stability without any agglomeration and sedimentation due to percolation network formed through intercalation of MWNTs in-between rGO layers. (C) 2015 Elsevier B.V. All rights reserved.