An Experimental Study on a New Design of Double Slope Solar Still with External Flatted and Internal Parabolic Reflectors

The demand for freshwater is exponentially rising in today's society, with industrial and manufacturing growth resulting in increased pollution of environmental assets. Therefore, one of the primary challenges for researchers is to produce freshwater using straightforward, inexpensive technology. Around the world, there are various arid and desert areas where ground water is scarce and rainfall is less common. The majority of the world's water sources, including lakes and rivers are brackish or saltwater, making them unsuitable for irrigation, drinking, or even basic household needs. Solar distillation (SD) overcomes the gap between the scarcity and productivity of water. The SD is a technique for purifying water that yields ultrapure water that is superior to bottled water sources. Despite the fact that SD is a straightforward technology, due to its large thermal capacity and lengthy processing times, productivity seems to be low. Researchers have endeavored to create several designs of stills in order to increase yield and have concluded that wick-type solar stills (WSSs) are efficient and effective. When compared to a traditional system, WSS improves efficiency by around 60%. Installing a multi-wick basin-type inverted absorber solar still (MWBIASS) delivers an instantaneous energy efficiency, destroyed exergy percentage and annual cost per kilogram of yield approximately 50.59%, 84.73%, and Rs. 0.91 (0.012 US$), respectively. This comparison review serves as a resource for prospective researchers looking to enhance the performance of WSSs while focusing on the most adroit aspects.

Fresh water is the basic requirement of human life. Water for drinking purpose, industrial and agricultural purposes demands ample quantity of fresh water. The solar desalination systems have the advantage of low maintenance and operational cost. In spite of high investment cost of solar stills, they are friendly to the nature. In the present article, a modified stepped solar still has been designed, fabricated and tested. The modification includes fabricating steps on which small earthen lamps are placed. The maximum temperature on the steps was found to be 67oC. In case of conventional solar still the maximum temperature recorded was 53oC. The maximum temperature of water at the steps was 26.41% higher than the basin temperature of conventional solar still. The maximum productivity of the modified solar still was 326.66% higher than conventional solar still. The optimum water input flow was found to be 250 ml/hr. I. Introduction Fresh water is primary requirement of human race. Water for drinking purpose and other industrial and agricultural purposes demands large quantity of fresh water (1). The solar desalination systems have the advantage of low maintenance and operational cost. Although solar stills have high investment cost, they are compatible with the environment (2). About 6.3 billion people are living on earth in which 400 million people are at living in water scarce areas which would rise to four billion by mid-century (3). The fabrication of solar still is simple and can be constructed by locally available materials and unskilled people. Solar stills are widely used for desalination in small scale. (4). According to an estimation, about 97% of available water sources are saline and/or consist of harmful bacteria and 2% are in the form of frozen glaciers and polar ice. Hence, only 1% of the earth's water can be used for drinking and domestic purposes (5).The arising requirement for water is primarily due to the increase of population and fast growth of industries (7). The heat energy of sun can be used in solar collectors, solar cooking, desalination and cooling systems (8). Generally, for steam generation, water heating processes and CPCs are used, as they are capable of producing higher temperatures in comparison of flat plate collectors, they can also be used for desalination purpose (9).Most of the arid, remote and semi-arid regions are lack natural fresh water in the southern part of the country and are dependent heavily on underground water for drinking purpose (10). Higher productivity is obtained in multiple-effect diffusion solar still (MEDS) (11). Solar stills are largely used for water purification in rural and remote areas with limited demand and low population when the potential of brine water sources and solar energy are available (12). II. Literature review There has been a lot of work in the field of solar stills to enhance its performance. Researchers have improved the performance by various means such as change in geometry, employment of mirrors in various orientation, use of waste heat etc. Park et al. (2016) designed a multiple-effect diffusion (MED) hybrid solar still with dual heat sources of solar thermal energy and waste heat. Performance tests with waste heat were performed with three operational parameters: (1) the seawater level in the basin (2) the seawater flow rate to the wick and (3) the amount of heat input into the hybrid still. It was observed that the productivity of the hybrid still increases with the increasing heat input, which recorded productivity of 18.02 kg/m 2 at waste heat amount of 22.37 MJ/d. The maximum productivity of distillate was obtained at the lowest seawater level with the experiment including waste heat source. The maximum performance of the MED solar still was achieved at the operation condition obtaining maximum productivity at the second effect plate (13). El-Agouz modified a stepped solar still using a storage tank for salt and sea water with continuous water circulation. Investigation was made on effect of installing a storage tank and cotton black absorber for modified stepped solar still on the distillate productivity. The indication was given by the results that, the productivity of the modified stepped still was higher than conventional solar still by 43% and 48% for sea and salt water with black absorber respectively, while 53% and 47% of sea and salt water, respectively with cotton absorber. The daily efficiency for conventional solar still was 20% lower than the modified stepped still. At a feed water flow rate of 3 LPM for salt water and 1 LPM for sea water, maximum efficiency of modified stepped still was obtained (8).

Stepped solar still: A review on designs analysis

Modelling and Analysis of Single Slope Solar Still at Different Water Depth

Evaluation of transparent acrylic stepped solar still equipped with internal and external reflectors and copper fins

Enhancing the stepped solar still performance using internal and external reflectors

A comprehensive review of direct solar desalination techniques and its advancements

Many researchers have experimentally and theoretically studied fresh water productivity in solar stills. In this regard, water preheating can play a noticeable role in enhancing the productivity of solar stills. In the present study, in order to study the effect of water preheating at the inlet of desalination system, a cascade solar still is built and integrated with two different solar collector in separated modes; an evacuated solar collector and a conventional flat plate solar collector. The mentioned solar still includes an external condenser, fin, and internal and external reflectors. It is worth noting that the embedded fins in the water passage are applied to induce hot spots and increase the evaporation rate and fresh water. The experiments were performed in August 2015 and summer 2017. The results showed that the combined desalination system with conventional flat plate collector and evacuated tube collector enhace productivity %60 and %13, respectively. In addition, efficiency of solar still in combination with conventional flat plate collector and evacuated tube collector was %81.8 and %59.1, respectively. The price of produced fresh water of solar still with conventional collector obtained 0.035 $/lit and for solar still with evacuated tube collector was 0.045 $/lit.

Influence of condensation surface on solar distillation

Productivity Enhancement of a Single Slope Solar Still with Energy Storage Medium

Water is one of the earth's most abundant resources, covering about three-quarters of the planet's surface. Yet, there is an acute shortage of potable water in many countries, especially in Africa and the Middle East region. The reason for this apparent contradiction is, of course, that ∼97.5% of the earth's water is salt water in the oceans and only 2.5% is fresh water in ground water, lakes and rivers and this supplies most human and animal needs. Tackling the water scarcity problem must involve better and more economic ways of desalinating seawater. This article presents a comprehensive review of water desalination systems, whether operated by conventional energy or renewable energy, to convert saline water into fresh water. These systems comprise the thermal phase change and membrane processes, in addition to some alternative processes. Thermal processes include the multistage flash, multiple effects boiling and vapour compression, cogeneration and solar distillation, while the membrane processes include reverse osmosis, electrodialysis and membrane distillation. It also covers the integration into desalination systems of potential renewable energy resources, including solar energy, wind and geothermal energy. Such systems are increasingly attractive in the Middle East and Africa, areas suffering from shortages of fresh water but where solar energy is plentiful and where operational and maintenance costs are low. The advantages and disadvantages, including the economic and environmental aspects, of these desalination systems are presented.

Solar distiller was constructed and tested in this study. The purpose is to get a portable water from nearly any source available in a relatively cheaper means using a renewable solar energy. The result obtained clearly confirmed the reliability of this method to provide portable water especially in a rural area of developing country like Nigeria where the supply of fresh water is inadequate. A local dirty stream that is constantly throughout the year served as the source of the brackish water was used for this work. Sample taken from this stream was distilled using the constructed double slope solar distiller. The incoming solar radiation from the sun is focused and concentrated on to solar water distillation unit. Analyzing the sample of the distillate, the pH value of the brackish feed water was 9.20 ±1.10 while that of the distillate was 8.10 ±1.06, which falls within the WHO limits of 6.5-8.5 for drinkable water.

Development and testing of a vertical solar still

Performance analysis of solar stills based on various factors affecting the productivity—A review

Water is important for all life forms on earth-plants, animals and human being, etc. For fresh water necessities, humanity relies on rivers, ponds, lakes and underground water reservoirs. The available fresh water on earth is mounted; however, the demand of fresh water is exaggerated owing to growth and speedy industrial enterprise. Therefore, there is a great need of proper water purification technique with less price. During this situation, solar distillation plays an awfully vital role. This method is analogous to natural water cycle but processed beneath closed and controlled conditions. The basin area of the still, free surface area of water, inlet temperature of water, wind velocity, solar radiation, depth are some of the factors that affect the productivity of the solar still. In the present work, the effects of introducing cylindrical ceramic packing into the basin of a solar distillation unit to increase the area of the basin were studied and compared with the results of solar distillation unit without packing. The maximum efficiency for copper electroplated aluminium basin with cylindrical ceramic packing and black painted basin with cylindrical ceramic packing at three litres of wastewater are 54.86 and 64.64% respectively. Keywords: Solar distillation, copper electroplated Al basin, Al basin with black paint, cylindrical ceramic packing Cite this Article Vamsi Krishna P, Sridevi V, Sri Hari Priya B. Effects of Introducing Cylindrical Ceramic Packing into a Single Slope Solar Distillation Unit. Journal of Water Pollution & Purification Research . 2016; 3(3): 1–14p.