**Solar-Powered Desalination**

## Emrah Deniz

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88 Desalination Updates

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Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/60436

#### **Abstract**

Drinkable fresh water, being a fundamental need of human beings, has become a serious concern for people especially living in crowded cities and countries with limited amount of water resources. Supplying fresh water is an energy intensive task especially when there is need for heating cold water to evaporate for distillation. Most of the big desalination plants around the world use fossil-based fuels as energy source to heat and vaporize the sea water or brackish water in order to produce fresh water.

However, environmental concerns along with decreasing oil reserves and increasing fuel costs call for reconsideration on the fuel types used in many areas as well as in desalination or distillation processes. There are a number of well-known alternative and renewable energy sources in the world like wind, geothermal, solar, biomass, etc. but achievability, availability when needed and energy storage are also very critical issues to operate the distillation plant effectively.

Since most of the desalination processes run on heat, solar energy can be used directly as heat source. Complex desalination systems which are all designed to improve the thermal efficiency and freshwater yield/productivity use many approaches such as multiple stage operation, pre-heating the feed water with the condensation energy, using additional heat sources (waste water from another process), concentrating solar energy to improve the operation temperature of the process, etc.

Solar desalination systems can be a good solution to the water scarcity, especially the Sunbelt region. However, dominant use of clean and renewable energy sources for desalination process and replacing the fossil fuel–based operations require more R&D studies to find more efficient and/or less costly power plants with continuous operation by the means of energy storage solutions.

**Keywords:** Desalination, solar energy, distillation, water scarcity, desalination methods

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **1. Introduction**

Freshwater and energy are two inseparable and essential commodities for sustaining human life on earth. Rapid population growth and industrialization, especially in developing countries in the recent past, have placed pressing demands for both freshwater and energy [1]. Both are to be conserved and preserved for the sustainable development of the world. On the other hand, there is an acute shortage of both energy and water, especially in the third world countries [2]. Only less than 1% of the water is available for the society for direct use, out of which the maximum fraction has been polluted due to non-manageable industrial develop‐ ments [2].

Due to the fast increase in the world population, the need for the energy increases rapidly. Various studies have been made to meet this extra energy demand. Most of these studies were focused on alternative energy sources. Solar energy is one of the most popular ones of these sources due to relatively less installation cost and long operation time without any need for maintenance [3]. Basically, all forms of the energy in the world, as we know it, are solar in origin. Oil, coal and natural gas is originally produced by photosynthetic processes, followed by complex chemical reactions, in which decaying vegetation was subjected to temperature and pressure over a long period of time [4].

Solar energy is so powerful and abundant that 30 min of solar radiation falling on earth is equal to the world annual energy demand. It is also cheap, environment friendly and nearly inexhaustible. Most of the world receives powerful solar radiation and has a good chance and opportunity to benefit from solar energy [3].

All ecosystems and every field of human activity depend on clean water and it is one of the most precious resources in today's world. Water is a primary need for life, health and sanita‐ tion, which brings it into the international agenda as a very important issue [2]. The lack of potable water poses a big problem in arid regions of the world where freshwater is becoming very scarce and expensive. Clean drinking water is one of the most important international health issues today [5]. Remote and arid to semi-arid regions depend on underground water for drinking. Unfortunately, underground water is not always considered to be fresh drinking water. In some instances, the salinity is too high for being drinkable, and it is called brackish water. In such cases, fresh water has to be either transported for long distances or connected with an expensive distribution water network at extremely high cost for, usually, a small population. Solar desalination can be a good solution for such a problem [6].

Desalination is one of mankind's earliest forms of water treatment, and it is still a popular treatment solution throughout the world today [5]. Distillation is one of the oldest and most rustic desalination techniques. In fact, it reproduces the natural process of the industrial desalination. Solar distillation is a thermal process that represents a sustainable solution to water shortages in the world. The desalination technique by solar energy, based on the principle of greenhouse is not new. Solar energy coupled to desalination offers a promising prospect for covering the fundamental needs of power and water in remote regions, where connection to the public electric grid is either not cost effective or not feasible, and where the water scarcity is severe [5].
