WHY SEAWATER DESALINATION:
97% of the earth’s water is seawater. There is a desperate need for potable water. As we see the deteriorating quality of freshwater supply and increasing demand for freshwater from industrial and technology growth, we are witnessing many cities around the world facing acute shortage of water to drink. As more and more desalination plants are moving towards renewable energy, the process has become very commercially viable in many places around the world, especially the coastal areas and islands.
All desalination processes require large amounts of energy, which lowers energy demand and also makes use of renewable energy, necessary to develop feasible processes of desalination.
WHAT IS THERMAL SEAWATER DESALINATION:
We see thermal seawater desalination every day throughout the year naturally happening. Evaporated seawater gets condensated back as freshwater rain. Solar desalination is essentially a small–scale duplicate of this natural hydrological cycle.
Solar energy is ideal for powering thermal desalination processes. This is because its direct application will not lead to energy conversion losses. Moreover, it is possible to retrofit present thermal desalination installations to absorb solar heat. Since desalination is highly energy-intensive, costly infrastructure is necessary for it.
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 to concentrate the sunlight onto a focal axis in which thermic fluid is passed. The thermic fluid absorbs the heat, which then is used in the desalination process. Working temperatures as high as 400 °C can be generated. Use of PTC for desalination is best in areas where you have higher solar irradiation; higher temperatures are required, for e.g. in multi-stage desalination procedures, and is the most cost-effective in large scale.
- Using CPC (Compound Parabolic Collector)
Compound parabolic collectors are non-tracking solar concentrating systems that accept radiation over a wider range of approaching angles for a given concentration ratio. Especially on the seashores 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 much easier to maintain and operate. CPCs are best suited for small to medium-sized desalination plants where temperature as high as 150 °C is required.
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 have very high durability and longevity.
- High energy storing capacity as PTC and CPC are suitable for large scale desalination.
- This process is energy efficient because of very low power being consumed.
- Use of unlimited ocean water resources.
- Prevents 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 have any effect on the environment.
- Can be integrated along with Solar PV desalination plants as well.
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 a possible solution for water shortages in many areas around the world for industries and people.