www.tjprc.org SCOPUS Indexed Journal editor@tjprc.org SOLAR STILL EFFICIENCY AUGMENTATION USING CYLINDRICAL SWEEPING AGITATOR ON THE ABSORBER PLATE M. S. MANJUNATH Faculty, School of Engineering and IT, Manipal Academy of Higher Education, Dubai Campus, Dubai, UAE ABSTRACT Passive solar stills are simple devices which generate potable water by way of desalination of brackish water. However, the main limitation of this device is its poor still efficiency. This paper presents an innovative technique of increasing the still efficiency using the sweeping agitator system in the passive solar still device. The agitator rotates on the still basin plate thereby sweeping the water on the plate and enhances mixing which results in increased heat transfer. The experiment is carried out on a single slope passive solar still in the outdoor conditions of Dubai during the month of May. The presence of sweeping agitator is shown to be effective in enhancing the distillate output as well as solar still efficiency. The results show that the solar still efficiency increased by about 3.95% as compared to base still. KEYWORDS: Solar Still, Still Efficiency, Desalination & Passive Solar Still Received: May 13, 2019; Accepted: Jun 03, 2019; Published: Jun 29, 2019; Paper Id.: IJMPERDAUG201935 1. INTRODUCTION Water scarcity is among the most dangerous crises in the world that currently affects half a billion people. A huge majority of those afflicted with such water shortages reside in arid and semi-arid regions. Desalination through Solar stills can be a simple and economically viable solution to this problem. A solar still is a very simple and cost-effective solution to address global water shortages. Solar stills are small and very simple in construction and hence require minimal maintenance and are easily transportable. Solar distillation is a tried and true technology. The first documented proof of a solar still was by Arab alchemists back in the 16th century. The core principle behind any conventional Solar Still is the greenhouse effect, through which heat from the Sun’s radiation enters the glass setup and stays trapped inside the still, thus allowing a high temperature to be attained inside the Still. The sun's energy heats water to the point of evaporation. As the water evaporates, water vapour rises, condensing on the glass surface for collection onto the guide ways. This process removes any heavy metals and microorganisms and the collected output is of the highest quality. The distilled water obtained through the use of a solar still has a better taste relative to water from a commercially distilled source. Solar stills essentially just operate on the processes of evaporation and condensation, and are thus very pure. Solar stills can therefore be very useful in providing water for any cooking and drinking needs. However, the biggest limitation of a solar still is its lower distillate output leading to lower still efficiency. Hence, there is a need to improve the distillate output and hence the solar still efficiency which could make the solar still more capable of producing drinking water. Several techniques have been proposed in the past by various researchers in this regard. Sellami et al (2017) have shown that the distillate output can be significantly improved to an extent of 58% by using blackened sponge on the absorber plate. The sponge absorbs the solar heat and acts as heat storage device which augments the evaporation rate. Basin water depth has been shown to affect the performance of still by Suneja and Tiwari (1999) where Original Article International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN (P): 2249-6890; ISSN (E): 2249-8001 Vol. 9, Issue 4, Aug 2019, 347-354 © TJPRC Pvt. Ltd.