Two ways to use solar power to make clean water

A couple of weeks ago I came across solar hydropanels for the first time. Developed by an American company called Zero Mass Water, these are panels that use solar PV to draw moisture out of the air. Each panel can make 2-5 litres of water a day, depending on humidity conditions. It’s the same quality or better than bottled water. Since these SOURCE panels can be placed anywhere, even in the desert, it’s potentially a way of bringing clean water to people who don’t yet have it. “Every person on this earth should have perfected water” says the website. “With SOURCE this is possible.”

If you want to install hydropanels on your home, each panel currently costs $2,000 plus $500 installation. Meeting my own family’s drinking water needs would be in the region of $4,500 dollars. Assuming the panels worked at the upper end of their efficiency, it would still take years before each litre of water I got out of the system was cheaper than bottled water.

But it’s new technology. Let’s say that as they improve the design and build bigger factories, they’ll be able to bring costs down to just a tenth of the current expense: $500 for a family of four. Now we’re talking, right? Maybe for me, so I can save on bottled water – if I was drinking bottled water in the first place. But it’s still not cheap enough for those who most need access to clean water, those living on less than $2 a day.

Let’s be generous. Let’s say they can make it a hundred times cheaper, and I could get a system for $50. With financing or philanthropy, you could get these out to Sub-Saharan Africa and make a difference. Maybe – unfortunately the panels have moving parts and need their filters replacing from time to time, so it’s not a one-off expense. But let’s be generous again and say those matters are solved in later iterations. Now we’ve got a technology that could provide “the water of everyone on the planet”, to quote Zero Mass.

Erm, no. We still don’t. Because it only makes 2-5 litres a day, hydropanels can indeed provide drinking water in the middle of nowhere. But they don’t make enough to provide water for cleaning and cooking, or any of the other things we might use water for.

Imagine a household in Madagascar where there’s a girl who isn’t in school because she’s sent to carry water every day. If a charity were to fit a hydropanel on her home, she’d still have to go and carry water.

Even though hydropanels can work anywhere, you’d still need to have another source of water nearby for all your other water needs. A river, a well or borehole – something that can provide water for non-drinking purposes, not to mention agriculture or animals. And if you’ve got another source of water, even seawater, then you can make yourself something like this:

A solar still heats up in the sun, and turns salty or dirty water into clean drinking water through the natural process of evaporation. There are many different designs, from basic lined pits in the ground to glass or perspex boxes. You can make one yourself, or there are off-the-shelf options like the Watercone. An elegant clay version won a design award a few years ago. These are all true appropriate technologies – affordable and easy to make with local materials. If you want a more advanced version, an Italian company called Solwa has combined one with a tiny solar PV panel to make an ‘active solar still’. It can make 8-10 litres of water a day.

So if you’d need another source of water anyway, and you can use passive solar power to purify it, what do we need hydropanels for? Why has it won awards, got so much attention, and attracted $24 million in start-up funding?

Don’t get me wrong – the SOURCE hydropanel is very clever. I have no interest in talking the company down. But they’re the ones making the big claims about meeting the world’s water needs. Green blogs such as Treehugger or Inhabitat have reported these claims uncritically, but this isn’t a system for ‘the world’. This is a system for rich people who currently drink bottled water.

It’s easy to be dazzled by high-tech solutions. But often what would work best for those who really need it is something simpler, cheaper, and low tech.


  1. Some people love the idea of a silver bullet, so a device that is stand alone, and can work anywhere is powerful — even if it is relatively very expensive.
    To me, this shows how cheap it is to harvest rainwater. In somewhere with decent year-round rainfall, you can probably harvest drinking/washing/gardening water for $3000 to $5000 for 10 to 15 kL. (I live in Adelaide, which has about a 5 month dry season, and spent more like $7000 to get 40 kL)
    I have considered trying to make a solar still to reclaim some of my grey water though — reclaiming 20 L / day would make my summer water go a _lot_ further. Main reason I haven’t is the engineering difficulty, and the risk of contamination if I get it wrong — also: realistically, I’d be better off making better use of grey water in the garden and using less potable water on the garden. Also, finally getting around to building that composting toilet…

    Cheers, Angus

    1. The hydropanels speak to our desire for self-sufficiency and our idolising of technology, so it’s not really surprising that it’s a powerful idea. But as you say, the affordability of rainwater catchment is thrown into sharp relief.

      Good luck with the composting toilet!

  2. Uncritical or shallow advice on sustainability is, unfortunately, rampant.
    I like Treehugger for some of their articles, but sometimes they not be as deeply researched as other sources (like the Guardian – still the gold standard, imo, and worthy of user contributions)

  3. We are in the 21st century and we all aware that what are our present and future needs? The technology is all make our life better because currently we have lots of problems and water crises is one of the main concern of our society, in this the technology make it possible to resolve the water crises for our future generations.

  4. The very inspiring thoughts you shared and I really want to learn more about solar panel’s, when I am installing it I am ready to the possibilities that will happen. Thank you for the great ideas you shared.

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