Over at Survival Resources, proprietor John McCann put together a distillation setup which makes for interesting reading. He does a good job showing the pros and cons of the system. Food for thought, as it takes considerable time and fuel to run one of these things.

No affiliation, though I am a customer at his site and I think he runs a good business.

I wonder how difficult it would be to use a solar hot water system to provide at least some of the heat required...

How about something like SODIS? http://www.sodis.ch/methode/index_EN

looks simple,cheap, and effective

Russ... I played around with some solar desalination proof of concept models several summers ago... it is pretty easy to get very small droplets of condensate, but much harder to actually collect them...a vertical glazing seemed like the answer... additionally I wanted to incorporate a "wick" absorption media... after a couple of models, the top pic is of the remnants of the most promising model... a small wash basin, with an inverted bowl to hold the black towel wick above the salt water level... the aluminum clothesline band at the edge of the basin to stand off the translucent leaf bag glazing... PVC fill tube for non potable water... a golf ball in each corner of the bag to hold the bags shape in the wind, and around which the condensate would puddle... I could get about 400ml in a 24hour period ... the bottom pic is of an earlier model with a hardware mesh screen to hold a larger wick... it was more complicated, but will give you some idea of the glazing...

Nice setup. I would be a bit concerned about water which was contaminated with petroleum products or other organic molecules. Some of them have boiling points very close to water and so would come over and be condensed with the steam.

If you know you don't have stuff like that in your water then this would be a good unit. Paint the pressure cooker black and stick it in a solar oven, running the copper tube out the side if you want to tap the sun.
-Blast

Worthwhile comment about boiling points. How might one get rid of such contaminants? I am usually dealing with spring water from wild sources,but in an urban setting, petroleum contamination is much more of an issue....

You can try running it through an activated charcoal filter but even that would be crude at best. It's a pretty tricky situation.
-Blast