Photothermal Energy Conversion Enhancement Studies Using Low Concentration Nanofluids

Abstract

The present study aims to develop a compact experimental facility to trap solar energy. Line focusing concentrators, i.e., Fresnel lens and secondary reflectors, are coupled to enhance the photothermal conversion efficiency. Two types of receiver tubes are used, a plain copper tube and an evacuated glass tube embedded with a copper tube. Surfactant-free multiwalled carbon nanotubes–Therminol55 nanofluid with concentrations of 25, 50, 75, and 100 ppm are used in this study. The characterization of the nanoparticles and nanofluids is presented. In the visible range, a maximum absorbance and extinction coefficient of 0.75 and 1.7 cm−1 are obtained for 100 ppm concentration. The thermal conductivity is also enhanced by 6.29% compared to base fluid. A maximum fluid temperature of 78.15 and 89.58 °C is observed for plain receiver tube and receiver tube in evacuated space, respectively, and the corresponding efficiencies are 12.65 and 17.36%

Experimental investigation on low concentration nanofluids with Fresnel lens and evacuated tubes for solar applications

“…used Therminol55 /Al 2 O 3 nanofluids with Fresnel lens and evacuated tubes and obtained a maximum photo‐thermal conversion efficiency of 62.7% for .1% volume concentration. The photo‐thermal conversion efficiencies of plain copper tube and evacuated tubes were 12.65% and 17.36% for the concentration of 100 ppm (Therminol55/MWCNTs), reported by Kalidoss et al 13 . This clearly shows that the combination of evacuated tubes and nanofluids play a major role in solar thermal conversion.…”

“…The absorbance and extinction coefficient trends of Al 2 O 3 nanofluids observed in this study are similar to that reported by various researchers. 13,20,39,40 The extinction results are derived from the absorbance results using mathematical equations. The maximum values obtained for Al 2 O 3 and CuO nanofluids, respectively, are 5.5 and 3.4 cm -1 in the UV region.…”

“…For a solar intensity of 1046.7 W/m 2 , the obtained maximum efficiency and outlet temperature were, respectively, 48% and 60 • C at a flow rate of 10 Lit/h. Photo-thermal efficiency and maximum temperature rise for a copper tube in evacuated space was reported by Kalidoss et al 13 Therminol 55 -MWCNTs nanofluid of concentration 100 ppm was used. The maximum temperature rise was 89.58 • C, and the conversion efficiency was 17.36%.…”

Optical and Thermal Properties of Therminol 55-TiO2 Nanofluids for Solar Energy Storage

“…The experimental efficiency of the ORC was 6.2%, and the power generated was 11.43 KWh/day. The optimum concentration for the optical absorbance of Therminol 55-MWCNTs was reported by Kalidoss et al [23].…”

“…The recorded temperature values at the specific time are added and divided by the number of days (five days each) for extracting the average values. The same procedure was followed in the research work of Kalidoss et al [23]. The experimental setup is placed in the surface azimuth angle 0°which is the true north-south direction.…”