The other day I walked past a house and noted approvingly that it had solar panels and solar hot water fitted on the roof. If get their way, they might one day be able to add a third service: drinking water.
Over 700 million people around the world lack a source of clean water. Many more have access to water from a well or a shared pump, but need to treat it before it is safe to drink. The infrastructure to purify tap water to drinking quality is expensive, and in rural areas in particular, could remain a long way off.
There are plenty of low-tech ways to purify water. One is to boil it, which requires energy. It can be done chemically, which can taste weird and can be expensive. Another option is a solar still, but this produces small amounts at a time. This might be fine for a household, if a bit of a hassle. But purifying enough water for a restaurant, a hospital or a school is going to be prohibitive.
Waterstillar’s solution is to use the natural process of evaporation and condensation to distill clean water, and to accelerate it with thermal solar panels. The panels capture the sun’s heat and go to work evaporating whatever source of water you pipe in – such as rainwater, if you wish. Water vapor condenses onto a distillation panel and runs down to a tank. A single unit can create 200-300 litres of water a day, but this can be scaled up to thousands of litres if required. The system doesn’t need any external energy source, it is designed to last 20 years, and it claims to be “the most sustainable water purification system in the world.”
You can’t buy a purification system, as the up-front cost would be a problem for those that need it most. Instead, the company will install and monitor, and users just pay a quarterly water bill. Developed in Denmark, WaterStillar is currently piloting in Mexico, with plans for local partnerships to make the technology more widely available.
Now we just and it will be possible to build a fully solar household.