(National Geographic) – The oceans have long taunted those who thirst.
Records dating to A.D. 200 show that sailors boiled seawater and used sponges to absorb fresh water from the steam. Today, desalination is more sophisticated: multistage flash distillation, reverse osmosis, electrodialysis, and more.
But one thing hasn’t changed since the time of the ancient mariners: It takes a lot of energy to squeeze drinkable water from salt water. So even though more than 70 percent of the Earth’s surface is covered with water, civilization has quenched its thirst mainly by tapping the one percent of world water that is unfrozen and fresh.
The one notable exception: Oil-rich Saudi Arabia and neighboring arid nations have used their wealth to purify ocean water. Yet their water demand is rising with population growth and industrialization at the same time that climate change is shrinking supply. Oil states, which depend on selling crude overseas for revenue, are loath to burn more barrels to keep drinking water flowing at home. So some aim to fuel new desalination operations with another abundant resource—the sun.
Other water-starved regions around the world want to do the same.