More than 300 million people get their fresh water by desalinating sea water. There are over 21,000 of these desalination installations around the world, including three right here on Ibiza, and they require vast amounts of energy to remove the salt from the water. There are two techniques that are used to desalinate seawater - thermal and membrane. In thermal desalination the water is heated until it evaporates, leaving the salt behind. This process is very energy intensive. The membrane-based system, also known as reverse osmosis, works by pushing saltwater through a semi-permeable membrane, which catches the salt. This still requires a significant amount of energy, but somewhat less than thermal. In both cases, the energy supply most often comes from fossil fuels that create pollution. 

To solve this problem Oneka Technologies of Canada has developed a floating desalination system which turns seawater into fresh water using only the power provided by the movement of the waves. These machines float on buoys that are anchored to the seabed, and use a membrane system. Energy absorbed from passing waves gives power to pumps that draw in seawater and pushes it through the desalination system. The fresh drinking water is then pumped to land through pipelines, again only using the power of the waves. The system works with waves as low as one metre high, and each unit can produce up to 49,000 litres of drinking water per day. These machines are modular, so multiple buoys can be anchored beside each other for maximum production.

The Dutch firm Desolenator has a different approach to sustainable desalination. They use solar panels to create the electricity and heat needed to power their thermal evaporation system. Any electricity that is not immediately needed for the process is stored in batteries, while excess heat energy is kept in hot water tanks. This stored energy allows the system to keep running through the night when there is no sunshine. “Desalination facilities are conventionally powered by fossil fuels,” says Susan Hunt of Oneka. “But the world has reached a point where we want to move away from fossil fuel powered desalination.”