Desalination domes, a novel approach to producing fresh water, are being developed to address the increasing global demand for water. This blog post explores the evolution of these domes, their designs, and the challenges they face, particularly in the context of a significant project in Saudi Arabia.
The global rate of water desalination is on the rise, with nearly 100 million cubic meters of fresh water produced daily—enough to fill the Great Pyramid of Giza around 36 times. As demand for fresh water continues to increase, researchers are exploring new methods to achieve desalination in a more energy-efficient and cost-effective manner. One intriguing concept is the use of large desalination domes, developed by the English company Solar Water, which has secured a $1.1 billion contract to deploy this system in Saudi Arabia as part of the 2030 NEOM project.
Desalination domes are not a new idea; they are a modern iteration of thermal desalination techniques that date back to ancient Greece, where salt water was boiled, and the resulting vapor was condensed to collect fresh water. These domes are visually striking and typically combine heating and condensation processes through their transparent outer structures.
The simplest form of a desalination dome can be seen in solar stills, which utilize a transparent plastic sheet to cover salty or dirty water. When sunlight hits the plastic, it creates a warm environment that heats the water, causing it to evaporate. The vapor then condenses on the plastic sheet and runs down to a collection point. This method is often used in survival situations due to its simplicity.
Aquam, a company specializing in solar stills, has developed a model that resembles a desalination dome, where water evaporates from the center and condenses on the outer walls, running down into a collection channel.
Solar Water's initial designs for their desalination domes have evolved over time, with varying capacities for fresh water production—from 200 million liters per day in the first version to just 1 million liters per day in a later iteration. The original design featured a steel structure with glass panels surrounded by mirrors that concentrated sunlight onto the steel frame, which conducted heat to a pool of salt water below. This process was intended to evaporate the water, with the steam being collected through small pipes to drive turbines for electricity generation.
Several concerns arose regarding the original design, particularly about the pressure within the dome and the efficiency of collecting fresh water. If steam was only collected from the small pipes, much of the fresh water could be wasted as it condensed on the dome's walls and returned to the saltwater pool. These issues prompted Solar Water to collaborate with Cranfield University in the UK to refine their design.
The second design, outlined in a paper titled "Design of a Novel Concentrating Solar Power Multi-Effect Desalination System," incorporates concentrated solar power and a multi-stage desalination process. This method involves a chain of chambers where salt water is turned into vapor in one chamber, and the heat from this vapor is used to heat salt water in subsequent chambers, maximizing energy efficiency.
In this design, the generated steam is used to heat salt water in an external tank, which is a more efficient use of energy compared to the original turbine-driven approach. However, the complexity of the dome design raises questions about its practicality compared to conventional multi-effect desalination systems.
One of the main advantages of the dome system is its simplicity and large condensation surface. However, similar to the original design, the water condensed on the dome's walls is not collected, complicating the overall system. Additionally, the new design relies heavily on a nearby concentrated solar field, which could take up an area about 50 times larger than the dome itself. This raises concerns about the efficiency of using a dome compared to traditional methods of desalination.
The desalination dome project was initially set to be commissioned in 2021. However, in an interview with the BBC, CEO Malcolm O. announced that he had ceased collaboration with Saudi Arabia and the NEOM project due to concerns over human rights violations and the displacement of villagers caused by construction activities. As a result, the future of the solar domes remains uncertain.
While desalination domes present an innovative approach to addressing water scarcity, their practicality and efficiency compared to established desalination technologies are still in question. The concept may be better suited for smaller-scale applications or survival devices in desert environments. Ultimately, leveraging proven thermal desalination technologies may provide a more effective solution for extracting fresh water from saltwater sources.
As the world continues to grapple with water scarcity, the exploration of new technologies like desalination domes will be crucial in finding sustainable solutions to meet the growing demand for fresh water.
