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

Abstract

The world demand for potable water is increasing steadily with growing population. Desalination using solar energy is suitable for potable water production from brackish and seawater. In this paper, we presents design, fabrication and testing of double slope solar still with external flatted and internal parabolic reflectors and also optimization of external flat reflector tilt angle for Egyptian climatic conditions. The external flat reflector tilted at (30°, 45°, 60° and 75°) on the horizontal plane. The depth of water inside basin still is 1cm. Experimental results were compared with conventional double slope solar still. Optimum tilt angle is found to be 60° with a maximum daily productivity of 9.89 lit/m 2 . Clean water is essential for good health which influences the social and economic development of any nation. People who use contaminated water are prone to waterborne diseases and they cannot effectively engage themselves in economic activities. Moreover, financial resources that could have been allocated to developmental projects are channelled to disease-curing efforts. Consequently, ill health contributes to the retardation of economic growth. The shortage of drinking water is expected to be the biggest problem of the world in this century due to unsustainable consumption rates and population growth. Pollution of fresh water resources (rivers, lakes and underground water) by industrial wastes has heightened the problem. Water is one of the most abundant resources on earth, covering three fourths of the planet's surface. About 97% of the earth's water is salt water in the oceans covering three fourths of the planet's surface covering three fourths of the planet's surface. About 97% of the earth's water is salt water in the oceans and 3% (about 36 million km 3 ) is fresh water contained in the poles (in the form of ice), ground water, lakes and rivers, which supply most of human and animal needs. Nearly, 70% from this tiny 3% of the world's fresh water is frozen in glaciers, permanent snow cover, ice and permafrost. Thirty percent of all fresh water is underground, most of it in deep, hard-to-reach aquifers. Lakes and rivers together contain just a little more than 0.25% of all fresh water; lakes contain most of it (1). Water is a basic necessity for sustaining life on the earth. With the passage of time due to technological usage and their waste disposal along with ignorance of human being caused water pollution which led the world to water scarcity. Due to water pollution the surface and under ground water reservoirs are now highly contaminated. The demand of fresh water is increasing with growth in human population. To meet the demand of potable water, scientists have developed various technologies such as reverse osmosis (RO), vapour compression (VC) and electro dialysis (ED) (2). These water purification methods are highly energy and cost intensive. It is well known that desalination plants use electrical energy which have both economical and environmental drawbacks and rely on conventional fuels (3). Therefore a method is required to use renewable energy, low input cost and less effort for the production of potable water. Solar distillation is a thermal desalination method where solar energy is used to distill fresh water from saline and brackish water. A distillation is one of many processes available for water purification, and sunlight is one of several forms of heat energy that can be used to power that process. Sunlight has the advantage of zero fuel cost but it requires more space for its collection. It is a great practical alternative, which offers life to those regions where the lack of fresh water hinders development (4). Solar water distillation is a solar technology with a very long history, and installations were found to be built over 2000 years ago, to produce salt rather than drinking water. An early large-scale solar still was built in 1874 to supply drinking water to mining community in Chile. Mass production occurred for the first time during the Second World War (5).