Desalination via solar energy for sustainable development

The economic viability of solar desalination methods is the primary obstacle
The challenge is of ascertaining how renewable energy sources can be utilized to operate a desalination system (Image: Vmenkov, Wikimedia Commons)
The challenge is of ascertaining how renewable energy sources can be utilized to operate a desalination system (Image: Vmenkov, Wikimedia Commons)

Water shortage has become a serious barrier to the development of many areas of the world in the context of global warming. This has prompted the development of novel desalination techniques for brackish and seawater. The only option to meet society's freshwater needs is to desalinate copious seawater to produce potable water.

Large desalination plants have been established owing to numerous successful research projects. However, significantly fewer attempts are made for dry regions where low-cost, maintenance-free, and low-operational-cost approaches are required. Both rapidly developing and underdeveloped nations struggle to provide their populations with pure drinking water.

In the desalination sector, CO2 emissions and significant ecological problems have increased. The desalination sector may be sustainable by integrating renewable energy and using proper brine disposal techniques. A recent paper ‘Emerging technologies to sustainability: A comprehensive study on solar desalination for sustainable development’ by Bhagwati et al reviews various desalination systems that incorporate renewable energy sources, with an emphasis on solar energy.

It tries to explain what solar desalination is, why it is performed, and what techniques can be used to make desalination more structured and cost-effective. In addition, this study provides a comprehensive review of all the solar desalination systems, indirect and direct, along with plant-specific technical data. In addition, the efforts that have been made to evaluate the economic viability of each desalination technology and the elements that determine its cost are discussed. 

Desalination costs vary depending on desalination technology and feed water requirements. The estimated per-unit expense of desalinated water is high since most thermal desalination plants use coal and oil. The cost of desalination water per m3 ranges between 0.521 and 1.02 dollars per m3, while the multiple effect distillation plant has a high potential of more than 91000 m3 per day.

Challenges and future scope

Solar desalination has proven to be a great and efficient source for desalinating water, but it has some challenges. The key issue is comprehending the essentials for desalination as a technique, what contributes significantly to the cost, and how these costs can be investigated.

The main challenge for solar desalination technologies is the economic feasibility. The costs of many solar desalination technologies are twice the market price. Therefore, it would be more expensive to use solar desalination than conventional. Furthermore, the utilization of batteries degrades the cost price and the economic feasibility.

Desalination is a power-consuming process requiring high-capacity plants which use expensive perishable fossil fuels, leading to global warming and pollution. Therefore, increasing fossil fuel prices greatly deterred this technology.

For instance, the infrastructure cost of sun-based collectors or plates in solar energy is high, and when heat energy is constant, it will result in heat flux. The main challenge in using geothermal energy in enabling a desalination plant is restrained by the geographical area where there is an excess of reachable.

Different solutions are available for treating brackish water with the limitation of very high temperature or mechanical force to drive the desalination unit. There is a need to ascertain the parameters in specific calculation formulas, and the method to determine the parameters needs to be clearer. The challenge is of ascertaining how renewable energy sources can be utilized to operate a desalination system.

Lastly, to assess and find out potential areas which require enhancement in a geothermal and solar power-driven desalination system is a challenge. Desalination costs, especially in seawater, remain relatively high, which is not sustainable for the countries of the freshwater avenue.

Weighing between environmental advantages and sustainability of the resource is quite debatable. However, the development of a cost-effective and energy-efficient desalination system may be the floodgate to the future. There is future scope to utilize nuclear energy for driving desalination units.

Developing a hybrid or mixture of solar desalination and various electrical options with giant desalination and power plants can be a good beginning for sustainable technology. Several options for solar desalination and electric power can be fused with the thermal or membrane desalination process. The experience and insight gathered in this expansion can lead to better and more large-scale projects. However, for remote areas, the most uncomplicated form of solar still is optimum for producing freshwater.

If we cite India's position in desalination technologies, the development of many desalination technologies is commendable. Chennai has two desalination plants on the principle of reverse osmosis (RO). RO is a consistent technology for freshwater creation but not quite supportable due to the high rejection rate. India's average daily solar emission ranges between 4 to 7 kWh/sq. meter, with at least 300 bright sunny days. It receives 500 trillion kW of solar energy per year, with Rajasthan and northern Gujarat receiving higher solar energy recipients.


The study of solar desalination for the availability and conversion of fresh potable water from salty or brackish water is gaining immense importance because the groundwater source is depleting and inconsistent. Moreover, freshwater is acutely in shortage in rural areas and arid areas. Hence, the need and importance cannot be over-emphasized. Hence, keeping the carbon footprint in mind is also important while designing a solar desalination plant.

Solar desalination systems are of two types, direct and indirect. Direct methods generally include solar stills. However, passive solar still cannot produce adequate freshwater per meter square area. In the active solar still, pre-heated water is taken, which helps the solar plant's efficiency. In the humidification and dehumidification process, distilled water is recovered, bringing moist air in contact with cool surfaces using condensation. Other methods like a solar chimney, reverse osmosis (where the membrane is the most fundamental element), multiple-effect distillation, and solar-powered multi-stage plants are some emerging and developing technologies.

The need to augment solar desalination and its techniques is due to the need for economy and structured sources rather than fossil fuel to generate pure water. The main challenge of solar desalination is the economic viability infrastructure cost of the plates and collectors, resulting in heat flux. The efficiency of the plant depends on various factors like defused radiation, geographical terrain, etc. Around 61% of the world's population can access potable water.

Desalination can become more acceptable and widespread for fresh water supply with a significant decrease in energy and cost. Various experimental analyses across the globe are done to examine the potential of various systems, their efficiency, and their effectiveness in various terrain and water supply levels. Solar desalination, converting saline water into freshwater, is an emerging technology. When recharge is less frequent, water desalination is heavily dependent.

The authors believe that both direct and indirect desalination techniques positively impact freshwater production. Some systems are suitable for large-scale production, while some are for small-scale. Most of them are cost-effective, but some are not. Some systems rely on recovering waste heat and treating saline water. The methods are eco-friendly, unconventional, and have the potential to be used in the future using regenerative energy.

The full paper can be accessed here

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