Search

In this research work, a solar air heater with double pass (SAHD) configuration having different porous mediums on its absorber plate is experimentally investigated. The stone pebbles, mild steel and aluminium chips have been used as porous mediums to augment the convective heat transfer (CHT) from plate to the air flowing in channel of SAHD. The experiment is conducted with these three materials at different mass flow rates (MFR) altering from 0.005 to 0.03 kg/s and at distinct solar intensities. The thermal efficiency ( η th ) and thermohydraulic efficiency ( η the ) of SAHD with three porous materials are computed at different MFR to analyse their impact on thermal performance. Findings reveal that SAHD with the porous medium on the absorber plate have higher heat transfer, thermal efficiency and thermohydraulic efficiency as compared to SAHD without porous medium. Out of the three materials used in experimentation, aluminium is found to have maximum influence on the performance of SAHD. The highest enhancement in heat transfer, η th and η the are achieved with aluminium chips as a porous medium. The maximum enhancements in η th and η the obtained are 84% and 74% respectively. The highest η the is attained at MFR of 0.025 kg/s for aluminium chips. The present study concludes that SAHD configuration with the porous medium in its 2nd passage is an efficient design for heat transfer improvement.

The present experimental work aims to improve the performance of single basin solar still using two different augmentation approach namely, reduced graphene oxide (RGO) coated absorber plate in solar still and RGO coated absorber plate along with activated carbon pellet as sensible heat energy storage medium. Results showed that utilization of RGO coated absorber plate along with activated carbon pellet in solar still augmented the water yield by 58.15% and full-day average energy efficiency by 64.44%, respectively, compared to conventional solar still. The fractional evaporation exergy was maximum for solar still integrated with RGO coating and activated carbon pellet, owing to the higher water temperature of the basin. The solar still integrated with RGO and activated carbon pellet caused the maximum average full-day exergy efficiency, due to excellent solar-thermal conversion efficiency and high conductivity of RGO along with high energy storage capacity of porous activated carbon. Cost analysis indicated that cost of fresh water produced per liter using RGO and RGO along with activated carbon pellet were lower than conventional solar still by 1.1% and 15.5%, respectively. Exergo-economic and environmental assessments of modified solar stills exhibited a cost-effective method and highly beneficial in reducing the carbon footprint by CO2 mitigation.

Direct generation of drinking water from ambient air using sunlight is of great interest for many populations. Here, a new desiccant mechanism using a highly hygroscopic silica gel was tested on the double-slope half-cylindrical basin solar still (DS-HCBSS) to extract the water content from the ambient air. As this mechanism is new to be applied into the solar still, an experimental and predictive study was conducted to investigate the thermal performance of the solar still under this modification. The modification was done in a double-slope half-cylindrical basin solar still, which has four longitudinal fins from inside to increase the surface area. The basin liner of the solar still and the fins were covered by a layer of silica gel with a thickness of 1.5 cm. A parabolic trough solar collector was used to raise the temperature inside the solar still during daytime solar illumination. The productivity of the DS-HCBSS with silica gel was enhanced by about 72% and 166% when longitudinal fins and longitudinal fins with gravels were used, respectively. Moreover, the efficiency of the DS-HCBSS with silica gel was increased by 15% and 35% when longitudinal fins and longitudinal fins with gravels were used, respectively. The best accumulated productivity (400 mL/m2) was recorded for the DS-HCBSS with silica gel, longitudinal fins, and gravels. Finally, a Neuro-fuzzy Inference System (ANFIS) model was employed to predict the process response (productivity) of the investigated systems under different process input factors (ambient temperature and solar irradiance). The predictive model obtained a good agreement with the experimental results. The experimental results revealed that the double-slope half-cylindrical basin solar still with the modification provides a new concept for Air Water Harvesting (AWH) and atmospheric water generation.