Solar Desalination

WHY SEAWATER DESALINATION:

97% of the earth’s water is seawater. There is a desperate need for portable water. As we see the deteriorating quality of fresh water supply and increasing demand for fresh water from industrial and technology growth, we are witnessing many cities around the world in acute shortage of drinkable water. As more and more desalination plants are moving towards renewable energy, the process has become very commercially viable for many places around the world, especially the coastal areas and islands.

Momentous amounts of energy are required in all desalination processes; therefore, reducing energy demand, as well as employing renewable energy, is imperative to developing viable desalination processes.

WHAT IS THERMAL SEAWATER DESALINATION:

We see thermal seawater desalination in action every day throughout the year naturally happening. Seawater gets evaporated and condensates back as fresh water rain. Solar desalination is essentially a small–scale duplicate of this natural hydrological cycle.

Solar energy is well suited to drive thermal desalination processes because it can be directly applied without entailing energy conversion losses; furthermore, existing thermal desalination installations can be easily retrofitted to accept solar heat. Desalination is very energy intensive and requires costly infrastructure.

METHODS OF THERMAL SEAWATER DESALINATION:

  • Using PTC (Parabolic Trough Concentrator):

Parabolic trough concentrators are solar concentrating collectors using a single-axis tracking mechanism to follow the sun’s trajectory that concentrate the sunlight onto a focal axis in which thermic fluid is passed. The thermic fluid absorbs the heat and then this heat is used in the desalination process. Working temperatures as high as 400 °C can be generated. Use of PTC for desalination are best in areas where you have higher solar irradiation, higher temperatures are required for eg in multi stage desalination procedures, and is most cost effective in large scale.

  • Using CPC (Compound Parabolic Collector)

Compound parabolic collectors are non-tracking solar concentrating system that accepts radiation over a wider range of approaching angles for a given concentration ratio. Especially on the sea shores where the moisture content in the air is higher, which disperses the solar radiation, CPC can be a very good alternative. CPCs have lower efficiency than PTC but are very easier to maintain and operate. CPCs are best suited for small to medium size desalination plants where temperature as high as 150 °C are required.

Compound Parabolic Collector

The above two solutions can work any of the desalination methods like:

  • Solar Assisted Multi–Stage Flash
  • Solar Assisted Multiple–Effect Distillation
  • Solar Assisted Heat Pumps
  • Solar Driven Reverse Osmosis
  • Solar Driven Electro–Dialysis
  • Solar Driven Membrane Distillation

ADVANTAGES OF SOLAR THERMAL DESALINATION:

  • The solar heating products CPC and PTC used have very high durability and longevity.
  • Having high energy storing capacity as PTC and CPC are suitable for large scale desalination.
  • This process is energy efficient because of very low power is being consumed.
  • Use of unlimited ocean water resource.
  • Prevent scaling because of the large wetting tubes in the heat transfer tubes.
  • Low operation and maintenance costs for the process to be carried out.
  • Eco friendly solution that doesn’t cause any effect on environment.
  • Can be integrated along with Solar PV desalination plants too.

Seawater desalination plants can be installed in industries near coastal regions like oil and gas refineries, Fertilizer plants, Petrochemical industries, Nuclear power plants, LNG plants and also municipalities along the coast. It is the possible solution for water shortages for many areas around the world for industries and people.