Solar Water Distillation

[Peter Clements]

Has anyone heard of a method for solar distillation of drinking water? After reading about experiments done by the Gaviotas community in South America, where they rigged a solar hot water heater up to a distillation rig, has anyone seen some details on how it's done?

[Richard on Maui]

I have seen it done once or twice Peter. Basically, a sheet of plastic is set over an evaporation pan which is filled with water. The sun heats the water up until it becomes vapour, then the vapour condenses on the plastic and runs down to gutters where it is collected. The kinds that I have seen have been setup to demonstrate that it is possible, but wouldn't be all that practical to purify water on a very large scale. but it would simply be a matter of making the unit a lot bigger I guess.

[christopher]

Hi Peter,

Try http://www.solaqua.com/solstilbas.html They have a few models.

Its ot that hard. I know people who have done it here with sea water on the cayes, making salt and water.

Good luck!

C

[Michaelangelica]

If you google "Solar still" in the pictures section of Google Search Engine (use the "")you should get about 100 photos.

I am working on a design myself.

The Federal Government gave $150,000+ to a comapany called Eyre Enterprises in SA to market a solar still in some environmental awards a few years ago.
They seem to have disappeared with the money and the still design.
Anyone heard of them?

[blackash]

Heard this guy on the radio national,
He made an Solar Water Purifier
His name is John Ward
This is the last bit of the interview. John is talking.
"My original thought was totally based upon humanitarian views which I’ve got and I wanted to cater for individual families, living under very poor conditions with effectively no money, barely living from day to day, having no access to electricity or a government-organised reticulated water system, so I thought I’d start at the very bottom end with a family that might need around 10 litres of water per day, of pure water which wouldn’t give them any more diseases than they’ve got already. So my target I think, has been achieved. It’s something which is portable, it has a handle on it just like a suitcase, you can set it up in any sunny location, you can fill it with bore water, sea water, urine, effluent, radio-active water and drink with equanimity what comes out of it."
Here a link to the transcript.
http://www.abc.net.au/ra/innovations/st ... 102910.htm
Here is a link to his web site
http://www.solarwaterpurifier.com

[Jez]

Thanks Blackash - it's definitely very interesting technology.

From what I've heard he's going to be on The New Inventors soon so it will be worth keeping an eye out for anyone wanting to see this unit in more detail.

Does anyone know what exactly is the difference between this unit and 'solar pasteurisation' - as in these units which are very cheap and would (at least at face value) produce a lot more 'clean' water a day for your initial outlay.

I assume pasteurisation would just kill bacteria when you're starting with bacteria laden water - so you couldn't start with effluent,remove mineral content, radiation etc.

Anyone able to clarify the distinction between pasteurisation and the end product from the solar water purifier?

[Jim Bob]

Interesting, the guy says on his website it's really cheap, but gives no price for it

Jez, the difference between pasteurisation and distillation is this.

In pasteurisation, the water is boiled, but stays in one vessel/bag/pot/whatever. So bacteria are killed, but any minerals, etc stay in there.

In distillation, the water is evapourated. This may, or may not, kill any bacteria (needs to be over 85 degrees for ten minutes to kill most bacteria). But it removes the mineral content, and/or oils, soaps, etc. To get an idea of what happens, put a pot of water on the stove, pour in a heap of salt. Then boil away the water. You'll see that salt gets left behind. (Just don't add water to the hot pot later, instead leave it aside to cool, the sudden water on it will give you a steam blast which could burn you.)

So pasteurisation is good for killing poisonous bugs, but won't turn salt or bore water into fresh drinking water. Whereas distillation usually won't kill bugs, but will remove the minerals, etc.

Distillation can be done really hot, and this'll kill the bugs - but solar distillation won't be that hot. It won't achieve that 85+ degrees for ten minutes which you need to kill (most) bugs.

[Jez]

Thanks Jim Bob, I figured that was the difference but I wasn't entirely sure.

I assumed he doesn't have a price for the unit because he mentions on the site that they need to raise about a million dollars to start manufacturing them in bulk cheaply...seems (quite rightly IMO) disappointed he's received no development funding whatsoever from the government.

[Arby]

Distillers are actually considered "purifiers" and from every thing I have read, they do take care of microorganisms...and in the same way they take care of other contaminates.

Here's a decent link with additional links at the bottom:

http://www.motherearthnews.com/Alternat ... lar_Stills

Arby

[Jim Bob]

It depends on the temperature they reach, Arby.

If you put a dish on top of a bowl of water on your back porch, you'll get water condensing on the dish. But that water won't be sterile. It's only sterile if it reaches a temperature of above 85 degrees for ten minutes. By comparison, a shower is 50-60 degrees, more than that burns you.

If you're sure that a regular solar distiller will get rid of microrganisms, then try this experiment. Poo in a bucket, mush it up with some water, then put that water through a distiller. If the water makes you sick, it wasn't sterile. And if you're not willing to try the experiment, then I guess you've not that much faith in the distillation, yeah?