Scientists in Canada have demonstrated a promising new device that can purify a gallon of water a day, for just a few cents per gallon. Better yet, it’s made of old tires, and can even generate small amounts of electricity.
There’s no shortage of water on Earth, but the irony is that very little of it is safe to drink. Oceans are too salty, and rivers and lakes are often too polluted, leaving many people unable to meet their basic needs.
But the new device, from researchers at Dalhousie University in Canada, could help people harvest drinking water on the cheap. The basic design looks familiar – it’s a floating solar still that soaks water up from below and evaporates it using heat from solar radiation, where it condenses on a dome that directs the water into a bag for collection.
The device has aced real-world tests, producing as much as 3.67 L (15.5 US cups) of fresh water per day per m2 of material. That’s roughly 1.5 times the amount of water an average person needs each day. Scaling up to serve a community could involve making larger stills or floating a whole fleet of them.
Importantly, it’s cheap too – the device can produce water at a cost of just 0.86 cents per liter. The key is that unlike similar devices that use precious metals like gold and silver, the main material here is old tires. That keeps the costs down while also keeping these waste materials out of landfill.
These tires are processed through what’s called pyrolysis, which involves heating them at high temperature without oxygen to produce a carbon-rich char. This is then mixed into plasmonic titanium carbides, which capture light and convert it into heat to evaporate the water. In this case, a paper-thin layer of this material is placed on the top surface of the floating foam under the dome.
As a bonus, the solar still can also be modified so that it also generates a small amount of electricity through the thermoelectric effect. This wouldn’t provide much juice, but it could be enough to power small water quality sensors, the team says.
There are plenty of solar still designs out there, including those that harvest water from the air and those that float on bodies of water, like this one. Some proposed designs have been claimed to be more efficient and produce more water per day, but this new one gets extra points for being so damn cheap. That’s a major advantage for developing countries and isolated areas where this could be most useful.
“We shouldn’t be making an expensive or very complicated device,” said Dr. Mita Dasog, co-lead author of the study. “It has to be easy to manufacture, last for a long time, and be easy to take apart and move.”
Plus, we don’t think we’ve seen another one that also produces electricity as a side hustle.
The research was published in the journal iScience.
Source: Dalhousie University