Mumut,

You mention the intended use of hot saline solar pond water as feed water for what I presume to be relatively standard evaporative stills. Have you considered using the hot (50-65 degree C) saline solar pond water in a reduced pressure environment wherein the saline feed water will boil at, say 50 degrees C? The reduced pressure environment may be obtainable in a set up similar to that of an atmospheric engine. Steam from, for example, a concentrating solar collector boiler is used to fill the space above the saline feed water in the pressure reduction chamber. This steam is then condensed with cold water sprays, and the pressure in the space drops rapidly. Once the pressure drops below that at which the saline feed will boil, the energy required to supply the latent heat of vapourization comes from the feed water itself. The 'low temperature' steam is then removed and condensed, and the cycle repeated.

The bulk of the energy required in distillation is to supply the latent heat of vapourization. This is collected in the cost-effective solar pond. The high temperature (100 degree C+) steam is only required for the cyclic establishment of the low pressure condition within the pressure reduction chamber. The relatively cooler saline feed water, now more saline than before, is either collected or returned to the solar pond, and the next charge of hot saline water admitted to the chamber, and the cycle repeated.

In the ultimate, apart from the pure water distillate, the product from this arrangement is a relatively concentrated brine. The volume of saline water that has to be held in a basin is reduced. It may be that the brine itself has a value as the saline layer in the ongoing construction of solar pondage. It is relatively easily and cheaply transported if it can be piped to the location where it is required. Whilst ever there is any advantage in the construction of solar pondage, the brine containing the salt has become a product necessary to the completion of that pondage. A new use for salt.

Thanks Forest,
Would you think there is a medium cost feasible way for a medium sized adelaide engineering company to build equipment to allow the type of distillation you suggest. Any bright ideas on simple designs?

There are designs for multi stage flash distillation and multi effect distillation around but they are up front capital intensive to get into thus solar stills were more possible for us, even though not as efficient. (Land is cheap so area taken up is not a huge factor). Also we couldn't get CSIRO energy solar thermal group to be interested in providing some research size solar thermal collector add on for the high temperature portion of it (we could try again or else where).

Thanks for your description - it was clear :-)

Mumut,

This link may be of use. http://www.ida.net/users/tetonsl/solar/solarhom.htm

It is an instruction manual for a flat mirror array tracking solar concentrator. Like a Harley-Davidson, built in America. By Americans. Read the absolutely ripper disclaimers-I'd love to send them to Workcover. Essentially low tech, and amenable to construction from reclaimed automotive and structural steel components. The sort of thing that can be competently built in a reasonable farm workshop by experienced (probably retired) amateur mechanics. Very interesting what the copyright holder had to say about the 1970s 'oil shock'.

Another link in terms of contacting enthusiasts in steam engineering is http://www.steamengine.com.au

An entirely different approach may be to co-locate with some industrial activity that has waste steam at not much in excess of 100 degrees C and around atmospheric pressure. The only thing you need the steam for is to establish your reduced pressure environment in which a charge of 50-65 degree C saline feedwater can boil off around 2.5% of its mass per cycle as distillate. Of course, your waste steam source has to have reasonable prospects of staying in business for this approach to remain valid.

If you wish to start out with minimal capital outlay start identifying the really prospective applications for small scale installations, and develop dead simple low tech designs that utilize waste: waste heat, degraded land, saline water, scrap components, and scrap workshop, engineering, marketing, and financing skills. There are plenty of the four last mentioned in Australia today.

Try and combine these things in stand-alone installations with a round-the-clock electricity delivery capability, preferably of grid-interactive standard. Make them 'set and forget' products.

What is it worth to have a dependable supply of domestic fresh water of say 1000 litres per day 365 days of the year in a place where there is presently none? How much more is it worth if there is a round-the-clock domestic or small commercial electricity supply with it?

Thanks Forest,

The kind of thing you mention will be important for a rural and remote Australia transitioning to a changed climate. There are also more incentives coming on line such as for remote solar (to reduce dependence on diesel generators).

Yes an adaptable system of appropriate technology - Desalination, small-medium electricity supply, solar pond heat energy for use in add on rural industries such as 24 hour temperature control in aquaculture tanks, glass houses, farm buildings etc. We also have an idea of using the heat energy to maintain ideal methanogenic bacteria operating temperature in farm biogas collection systems to significantly increase their efficiency.

As we are operating as a community network input from someone such as yourself would be very welcome. If you wish to get in contact with us please use exec478i@gsen.org. Thanks for all the info.