Egypt is facing a growing water crisis due to its arid climate, limited water resources, and rapidly increasing population. The country of 114 million people depends heavily on the longest river in the world, the Nile, for fresh water. But rising demand for water in Egypt and from upstream users of the Nile’s water (like Ethiopia’s Grand Ethiopian Renaissance Dam) means the Nile is no longer enough.
Chemical engineer Thokozani Majozi was part of a team who built a model of a new wind-powered reverse osmosis desalination system. These use energy from the leftover salty water to power the plant. The team found that this model could work well in very windy coastal resorts. Water systems like this are resilient to climate change. Water agencies are currently lobbying the G20, led this year by South Africa, to dedicate much more finance to setting these up.
How could desalination help Egypt?
Egypt’s per capita share of renewable fresh water from the Nile and rain water has been falling for decades. The country is currently below the water poverty threshold of 1,000 cubic metres per person per year. This is only about half the water they need for health and wellbeing.
Climate change is making the situation worse. It disrupts rainfall patterns and intensifies droughts, making traditional water sources less reliable.
Desalination offers a promising solution. By removing salts and impurities from seawater, desalination can provide a steady supply of clean water for drinking, agriculture and industry. For example, Saudi Arabia’s Jubail Desalination Plant 3A supplies drinkable water to 1.6 million people per day.
Desalination is very effective when reverse osmosis is used. Reverse osmosis uses pressure to force seawater through a semi-permeable membrane. This removes all dissolved salts, contaminants, and impurities like dirt and microplastic from the water.
It’s already recognised as especially suitable for Egypt’s extensive coastal regions which are far from the Nile river.
How much energy do desalination plants need?
Reverse osmosis desalination requires high-pressure pumps to force seawater through membranes. The process typically consumes between 3 kWh and 8 kWh of electricity for every cubic metre of freshwater produced. This is enough to power an average household refrigerator for 24 hours.
So, producing 600,000 cubic metres of water would use the same amount of electricity as 600,000 fridges. By comparison, a typical (municipal) water treatment facility only uses 0.2 kWh to 1 kWh of electricity to produce a cubic metre of drinkable water.
This energy demand makes desalination plants costly to run. If a country’s electricity is generated from burning fossil fuels like coal, using this dirty energy to run a desalination plant would mean that desalination has a negative environmental impact.
Egypt aims to reduce its carbon footprint and transition to a more sustainable energy model. Therefore, running desalination plants using renewable energy is vital for the long-term viability of desalination technologies in the region.
How could wind power help?
Our research built a model of a new wind-powered reverse osmosis desalination system.
Instead of converting wind energy into electricity, our new model used wind power to drive pumps that provide the pressure required for the reverse osmosis. When wind speeds are high, the system stores excess compressed air in dedicated compressed air storage. This is drawn upon during low wind periods. We found that this eliminated the need for conventional electrical infrastructure, such as generators, motors and battery banks.
Our model showed that energy could also be created from the salty water that is left over after sea water is desalinated. Reverse osmosis uses high pressure to push seawater through the membrane that removes salt and other impurities. This means that the salty water is always on the high pressure side of the reverse osmosis membrane. This leftover salty water is usually discarded.
In our system, we lower this high pressure back to atmospheric pressure before throwing away the salty water. This provides extra pressure that helps push new seawater through the membrane, thereby reducing the system’s overall energy consumption.
We tested our model in a laboratory using wind speed data from 20 coastal cities across Egypt. Results showed that Hurghada, a major resort city situated about 500 kilometres south-east of Cairo, would be the most promising location. This is because of its favourable wind speeds, which would mean the lowest total cost of water and the highest annual water output. The amount of drinkable water that could be produced depends on the size of the system – in other words, how much funding is available to build a bigger size desalination plant.
This concept is still at a research stage of development. It falls under what have become known as Long Duration Energy Storage Schemes (technology that can store renewable energy for over 10 hours). It now needs to be applied in practice.
What needs to happen next?
The next step should be the development of pilot projects in very windy areas like Hurghada, and El Gouna, a purpose-built resort town located about 25km north of Hurghada.
Pilot projects would validate the performance of the proposed system under real-world conditions. This would allow scientists to see what these desalination plants will need if they are to operate over many years.
We also need to test all the components that make up this system to see if they are durable, reliable and cost-effective.
Egypt’s Science and Technological Development Fund and other national funding organisations usually play a leading role in financing these innovative projects. Partnerships between universities, engineering firms and local authorities are also crucial for building technical expertise and infrastructure.
Public awareness campaigns should be held, to get community support for these projects and hear community concerns. Publicity would also attract private investment by showing the environmental and economic benefits of wind-powered desalination.
By capitalising on its abundant wind resources and coastline, Egypt can pioneer a new generation of decentralised, low-carbon water infrastructure. The wind-powered reverse osmosis systems could serve as a model for other water-scarce nations in the region and beyond.
(Professor Majozi is the president of the Academy of Science of South Africa council in the S20 – the official engagement group within the G20 that fosters science-based dialogue and provides policy advice).
Thokozani Majozi receives funding from National Research Foundation (NRF) and South African National Energy Development Institute (SANEDI).
By Thokozani Majozi, Full Professor and Dean of the Faculty of Engineering and the Built Environment, University of the Witwatersrand
