Malcolm Aw’s quest to create fresh water using the power of the sun started out with two salad bowls.
It was the early 1980s, and the entrepreneur was sitting on his balcony on a bright, sunny London day. Pondering the power of the rays beaming down from our star 150 million kilometers above his head, Aw conducted an experiment that wouldn’t be out of place in a high-school science class.
He placed some saltwater in a salad dish, with another, larger bowl on top. After a while, somewhat unsurprisingly, some of the salt water evaporated and condensed, gathering in a tray below.
It wasn’t exactly a eureka moment. But it did set Aw’s mind racing as to how such a basic principle could be used on a grand scale. And, almost 40 years after that improvised experiment, he is trying to make this a reality in the Middle East.
It’s no secret that the world’s looming water crisis affects this region more than most. According to the World Resources Institute, 12 of the 17 countries facing “extremely high” water stress are in the Middle East and North Africa.
The lack of natural water resources in the Arabian Gulf, especially, has led to some expensive, and highly polluting measures. The Gulf has the dubious honor of being the world’s “leader” in desalinated water, producing 40 percent of the world’s total supply, according to a study in early 2020. Saudi Arabia—home to the world’s largest water desalination facility at Al-Jubail, and which is expected to invest $80 billion in similar projects over the next 10 years—is responsible for about a fifth of the world’s total output.
Desalination plants spew out a combined 76 million tons of CO2 per year, with emissions expected to grow to around 218 million tons by 2040 if no action is taken, according to Abu Dhabi sustainability initiative Masdar. Yet they also pose a specific danger to marine life, thanks to the salty water that gets pumped back into the sea, warns Leticia Reis de Carvalho, coordinator of the UN Environment Programme’s Water Management Branch.
Waste brine from desalination can limit the growth of marine organisms, increase seawater temperature, and lower the levels of dissolved oxygen, causing further harm to aquatic life, Carvalho says.
“Hot and highly saline brine associated with desalination facilities, a range of pollutants, high energy use, and associated repercussions including carbon emissions, represent… increasing environmental threats,” she adds.
It is a problem Malcolm Aw thinks he can solve. After his balcony experiment, Aw became consumed in other projects. But the entrepreneur returned to the idea in 2000, forming a company called Water L’eau—a pun on the English and French words for “water”—and which later became the somewhat less playfully named Solar Water, a UK-based company looking to deliver “carbon neutral” desalination.
Developing the salad-bowl desalination concept was “not rocket science,” says Aw—but still took many years. It was accelerated by an association with the UK’s Cranfield University, where a proof of concept was developed over the course of six months in collaboration with researchers and students.
The bowl will be much bigger this time. Imagine a sphere formed by a dome extending 25 meters into the air, which covers a cauldron extending a further 25 meters into the ground. Solar Water envisages seawater being transported inland via aqueducts topped with glass that, under sunlight, would warm the water. This would then feed into the cauldron, where it would be superheated thanks to energy feeding down from the “solar dome.” The glass-and steel dome would itself be heated using concentrating solar power (CSP), with more than 100 solar reflectors around the structure directing the sun’s energy onto the frame. After the salt water evaporates, it condenses as freshwater as it is piped to reservoirs.
Although similar technology has been used to generate electricity—typically by generating heat to create steam, driving a turbine—this is one of the first to use it directly for desalination. Yet Aw downplays the sophistication of the tech involved. “Basically what we have is a huge kettle,” he says. “You can’t get more simple than that: We have a big kettle boiling water, and producing 30,000 cubic meters per hour.” There is a little more to it than that. The mirrors surrounding the dome have to be adjusted to maximize efficiency. “It’s like a sunflower—it’s got to follow the sun,” says Aw. “Even though it’s a very simple thing, there has to be precision.”
The problem of leftover salt remains. Aw says Solar Water’s system allows for the byproduct to be drained away to tanks, which can then be sold on to, for example, battery producers.
Some have expressed reservations about the feasibility of the design, as well as some of the projected production costs. One estimate was 34 US cents per cubic meter of water produced—significantly lower than desalination plants using reverse osmosis methods. The solar dome is yet to be tested on an industrial scale.
But that is going to change. Neom, Saudi Arabia’s ambitious $500 billion country-within-a-country currently under development, said in January it had signed an agreement with Solar Water to pilot the first ever solar dome. The initial plan is for a 25-meter desalination sphere, followed by three more of between 50 and 80 meters, says Aw. Work on the first plant was expected to be completed by the end of this year, although the announcement was made before the full extent of the coronavirus pandemic was known.
Solar Water also says it has signed a contract with a Jordanian mining company, and hopes to have several plants under construction by the end of the year.
The water produced could be used as drinking water—although further treatment would be required—but Aw sees a major use as being in desert farming and irrigation.
“We can build miles of canals into the middle of the desert, and turn the desert green,” he says. “We can reverse climate change. The only thing we need is water… We can make the desert blossom.”
Aw believes solar technology could replace traditional desalination plants—but that would not, of course, happen overnight.
“We got out of the Stone Age, but not because we ran out of stones. So we can get out of fossil fuel age by going straight on to solar power,” he says. “There are 18,000 desalination plants across the world. If we can replace all of them in due course, can you imagine how healthy the ocean would become? Because at the moment, what they are doing is horrible.”
Additional research by Malavika Kodiyath