Engineers at MIT and in China are aiming to turn seawater into drinking water with a completely passive device that is inspired by the ocean, and powered by the sun.
In a paper appearing today in the journal Joule, the team outlines the design for a new solar desalination system that takes in saltwater and heats it with natural sunlight.
The researchers estimate that if the system is scaled up to the size of a small suitcase, it could produce about 4 to 6 liters of drinking water per hour and last several years before requiring replacement parts. At this scale and performance, the system could produce drinking water at a rate and price that is cheaper than tap water.
On the large scale this is true, but the problem is that the concentrated brine doesn’t instantly dilute back into the entire ocean. In large quantities, the waste outflow would damage the local coastal ecosystem before it was sufficiently diluted.
What is “sufficiently diluted” this device discharges brine at only slightly higher levels than what it takes in.
A good question. This device is a small prototype, not a production model.
How much salinity is too much would depend on the scale of the output of an actual production unit, and environment it is placed in. Even if the discharge is only slightly higher in salinity, cycling enough water to sustain a city would definitely cause an imbalance in the local coastal environment. Especially as it is used over time, the salinity in that area would increase over time if today’s brine is added before yesterday’s brine can fully spread out.
They’re getting really good at working with tidal flow and weather to ensure they don’t cause problems, it’s just all got to be built into the system when they design it