Renewable energy sources for water desalting in Tunisia

Achievements and potential of coupling between renewable energy sources and brackish or seawater desalting technologies in Tunisia have been investigated. These sources of energy, mainly solar, wind and geothermal, have been identified throughout the country, and their suitability for coupling with different desalting technologies has been investigated. Renewable energies are expected to have a flourishing future and an important role in the domain of brackish and seawater desalination. Of special interest are small desalination plants that can be operated with small quantities of energy. Small-scale, renewable, energy-driven desalination plants might be the most economical solution for providing potable water to remote and isolated communities where the electric grid and the proper infrastructure are lacking. By exploiting renewable energies for fresh water production, three main problems can be addressed: fresh water scarcity, fossil energy depletion and environmental degradation due to gas emissions and hydrocarbon pollution.

The prospects of renewable energy development in Tunisia show a flourishing future. Solar energy, being the most promising form, has been assessed to be available in huge quantities throughout the country and all year round. With a higher potential in the southern part of the country, solar energy is in perfect synergy with locations where water desalination is most needed. Solar energy is well suited for powering most of desalting techniques. In addition, to direct solar radiation usage via solar stills, solar energy can be coupled to MED and TVC processes in the form of heat energy as well as to RO, ED and MVC in the form of electrical energy. It is also encouraging to know that a large percentage of the population in the south lives in small agglomerations and remote villages, making the implementation of small-size desalination plants a perfectly adequate solution. These small desalination plants can be operated with minimal energy requirements and are thus suitable for coupling with renewable energy sources. Wind potential in the country is more abundant in the northern part and in coastal regions. This form of renewable energy is also suitable for use with small capacity desalination units, especially the RO type. If water desalination for urban use is less needed in the northern part of the country, the wind energy potential can surely be of great use, especially in the coastal region where numerous tourist resorts are potential users of small desalination plants, and in mountainous regions. The geothermal energy potential has been assessed as limited, given that most of the geothermal sources in the country are of low enthalpy. However, their direct use in thermal desalination plants (e.g., MED, TVC) can still give promising results knowing that these desalination processes can be operated at relatively low temperatures. Of special value are the geothermal sources in the south where important brackish groundwater sources need to be desalted. The potential of any of the three main renewable energy sources described above is considerable. However, a higher potential can be obtained by coupling two or more of these energies within a hybrid desalination system. It is, for example, a very attractive idea to couple both geothermal and solar energies, especially in locations where both are present in substantial amounts.