Design, construction and performance analysis of a solar powered dual mode desalination system for water purification

Abstract

Human life is based on water. Safe drinking water is one of our fundamental needs. Water is one of the most abundant resources on earth covering 75% of the planet’s surface. About 97% of the earth’s water is salt water in the oceans, and a tiny 3% is fresh water. Sea water contains large amount of salts. The salts exist in the form of chloride, sulfate, sodium, magnesium, potassium etc. Chloride and sulfate contribute to about 55% and 31% of sea salts respectively. Eating small quantities of saline water are not harmful, but more can be dangerous, ultimately producing fatal seizures, heart arrhythmias and kidney failure. Other than salts, there are many other unwanted elements, like bacteria, Parasites and heavy metals in the water. Major parts of Bangladesh do not have access to safe drinking water. Fresh water which was once obtained from rivers, lakes and ponds in plenty is now becoming scarce because of industrialization and population explosion. Increased irrigation of land for producing larger amount of food adds to the fresh water scarcity. Also, the available portable water is now increasingly being polluted by industrial and sewage waste. Therefore, there is need to purify the water to make suitable for drinking. It would be feasible to address the water-shortage problem with seawater desalination; however, the separation of salts from seawater requires large amounts of energy which, when produced from fossil fuels, can cause harm to the environment. Therefore, there is a need to employ environmentally friendly energy sources in order to desalinate seawater. As a part of my thesis, I have made a single basin single slope desalination device, where I used dual mode thermal energy for quick vaporization. One is the thermal energy trapped from solar radiation through a transparent top cover. Another one is the thermal energy of DC heaters powered by Photovoltaic module. Designed device is renewable energy (Solar) based and environmentally-friendly. This can be used for water heating, desalination and purification. This report covers introduction into desalination, comparative analysis of current desalination technologies. Some general concepts are given for the proper selection of desalination method. Description of designed desalination device is given in detail. After that, its construction, total cost, performance, efficiency and results are given here. Device maintenance, drawbacks and few related points etc. are also studied. From this research, I have concluded that, solar powered dual mode desalination may not be a viable option at the present price structure, further research for efficiency improvement of device could make solar assisted desalination one of the most economically advantageous device.