**6. Conclusion**

Drinkable fresh water, being a fundamental need of human being, 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 reconsidera‐ tion on the fuel types used in many areas as well as in desalination or distillation process‐ es. 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.

A very fortunate aspect of the issue is the coincidence of fresh water need and abundant solar energy. Most of the places with severe water scarcity are about the equator region where people needs more water due to highest degrees of air temperature in the world. Therefore, especially for these countries located in solar belt region, solar energy is a readily available, cost-free and abundant energy source which does not require transportation or very sophisticated technology to benefit from. Since most of the desalination processes run on heat, solar energy can be used directly as heat source which decreases the installation and operation costs significantly. Apart from simple solar powered stills, of course there are more complicated, yet much more efficient solar powered stills. 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 of especially the Sunbelt region. However, dominant use of clean and renewable energy sources for desalination process and replacement of 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.

### **Nomenclature**

**•** Double slope passive solar still has a higher thermal efficiency than double slope active solar

**•** In active double effect solar stills lower basin gives the maximum yield because of the high

**•** The amount of fresh water produce in the still is closely related with thermal conductivity

Drinkable fresh water, being a fundamental need of human being, 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 reconsidera‐ tion on the fuel types used in many areas as well as in desalination or distillation process‐ es. 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. A very fortunate aspect of the issue is the coincidence of fresh water need and abundant solar energy. Most of the places with severe water scarcity are about the equator region where people needs more water due to highest degrees of air temperature in the world. Therefore, especially for these countries located in solar belt region, solar energy is a readily available, cost-free and abundant energy source which does not require transportation or very sophisticated technology to benefit from. Since most of the desalination processes run on heat, solar energy can be used directly as heat source which decreases the installation and operation costs significantly. Apart from simple solar powered stills, of course there are more complicated, yet much more efficient solar powered stills. 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

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

still.

118 Desalination Updates

noon temperature.

**6. Conclusion**

process etc.

the means of energy storage solutions.

of condensing cover material.


