Sumaleth

It doesn't stack up well against desalination. You can get a truck-sized desalination plant that can produce 10000 litres per hour, and the really big plants in the middle east can produce 34 million litres of clean water per hour, 24 hours a day. The cost of maintenance and volume of greenhouse gas emissions are probably more important here in Australia that straight volume, but it's still not looking as attractive as I'd hoped. And I found this, which notes that it's an old idea anyway: http://www.itdg.org/docs/technical_information_service/solar_distillation.pdf End of exploration I think. Thanks for helping me work through that.

wow, great post. re turbulence, I thought the less movement of the water the more efficient it would be. re steam, I hadn't thought about the generated steam obstructing the generation. Perhaps if the beam entered the chamber at an angle, and the steam was sucked away on the other side. Or, as you say, boiling up the whole chamber, but there you need to regulate water in/out plus there's heat-up time, so you lose efficiency two ways. I guess this is where practical experimentation would be worthwhile, to find the optimum setup. There might even be different optimums for different environments. re 2600 m^2, that's not as efficient as I hoped it might be, but it's still a smaller footprint than a recycling or desalination plant, and would be a lot cheaper to run. 1kg/second sounds pretty good too -- about 3600 litres per hour of sunlight. I'll see if I can find how that compares to desal/recycle/rain. Thanks for the great post.

I had in mind a chamber that is open to the ocean, so that water is free to come and go. There'd be a small entrance, to keep turbulance to a minimum, but the coming and going of water would take the salt. I also didn't see the chamber being heated up, which as you say would have build-up time. I'm thinking instead that it could focus the light so finely that you generate spontaneous evaporation at the point of contact with the water. Even with something as small as a magifying glass you can generate a lot of heat at the focal point, so I imagine that an array of mirrors focused tightly onto water should be able to evaporate it, even with the water moving around and even with salt in the water. If the focus is tight and water movement minimal then there shouldn't be too much wastage, and nothing is wasted building up heat in the system. As you say, this couldn't supply a town with water, but I'd be curious to know how what volume of water it could generate from a plant of a given size.

We have a bit of a water crisis developing here in Australia, and I had this idea: First, we allow the ocean to naturally flow into a small chamber, above which sits an array of mirrors that redirect and focus sunlight onto the smallest possible area* of the water's surface. The sunlight boils the water at the focal point, releasing steam which is allowed to condense into a collection pipe. Lots of details to work out, but I'm wondering whether (with fine-tuning) this has the potential to generate enough drinking water to make setup worthwhile? I don't expect it would be a great lone source of clean water, but maybe as an efficient top-up system. By its nature, it would work on the days when it's not raining. Rowan.