A Fresh Way to Take the Salt out of Seawater

Ben Sparrow and Joshua Zoshi met at Simon Fraser University in Vancouver, while completing their MBAs. Their company, Saltworks Technologies, has set up a test plant beside the sea in Vancouver and will open for business in November. Existing desalination plants work in one of two ways. Some distil seawater by heating it up to evaporate part of it. They then condense the vapour — a process that requires electricity. The other plants use reverse osmosis. This employs high-pressure pumps to force the water from brine through a membrane that is impermeable to salt. That, too, needs electricity. Even the best reverse-osmosis plants require 3.7 kilowatt hours (kWh) of energy to produce 1,000 litres of drinking water. Mr Sparrow and Mr Zoshi reckon they can produce that much fresh water with less than 1 kWh of electricity, and no other paid-for source of power is needed. Their process is fuelled by concentration gradients of salinity between different vessels of brine. These different salinities are brought about by evaporation