This is my first time on this forum so hi to all of you.

My query is based on the fairly topical subject of salts based on a growing trend of desalination and water filtration.
It seems to me that not much thought is being given to the end result of the purification process in that more filtration leads to more salt - and from what I have read there does not appear to be a great deal of thought being given to what we should be doing with this byproduct.

Any thoughts in Academia?

G

Gonzo,
The concentrated brines that can be a by-product of desalination of seawater or saline groundwater have a value all their own. One such value resides in their usefulness as a component of solar ponds. Solar ponds are amongst the most cost-effective solar heat collection and storage devices. A layer of dense highly saline water is insulated by a layer of less dense fresh water separated by a membrane. Solar radiation is trapped within the saline layer, which heats up. This heat is used to generate electricity in a conventional closed-cycle thermal power plant using a low poiling point working fluid. (A facility like this supplies electricity for Birdsville in SW Queensland; the only difference being that the source of the heat is hot artesian water, water heated by the natural nuclear fission occurring in subterranean granite masses.) Relative scarcity of dependable fresh water supply for even domestic purposes is frequently a feature of life in Australia. I can only wonder that this convergence of availability of resource and demand for both product (fresh water) and by-product (in the ultimate, electricity) both in near coastal and remote inland locations is not recognised as an ideal opportunity for the application and development of natural (or, to use the buzz-word, sustainable) energy sources.
Not only is the brine by-product useful in its own right, it is easy to handle and transport. It can be piped to a usage point, it can be piped back out to sea, or it can be piped and re-injected into an already saline aquifer. Given, with respect to seawater particularly, the absolutely miniscule quantities of water removed as fresh water in relation to the source, the return of relatively more concentrated salt water to the sea need not be an environmental impact problem: it is so inherently controllable on both the small scale and the large that I can only marvel at the seemingly uninformed objections being thrown up against desalination on this ground. Is there some other agenda or community perception at work producing such negativity?

Forrest:

This is good stuff. Part of the issue here is in the effect of changing the water chemistry on the remainder of the plant. Your suggestion for heat 'banks' has a lot of merit in that:
a. we have to have evaporation ponds anyway
b. we need the facility to generate additional heat to help process the waste stream through our Brine Concentrators.

Would appreciate continued discussion on this but am going to read up on your ideas thus far.

As for public perception I think any issue where a 'waste product' is generated causes issues through ignorance rather than actually being an issue. I also think that this has a historical basis from when waste WAS dumped and the implications of this ignored. Fortunately I work for a Co that cannot do this so I am comfortable with looking at "radical' alternatives.

If you have any links etc to this idea I would appreciate the info.

Thanks again.
Gonzo

Gonzo,
The net is positively redolent with information on this general subject, from the conceptual (eg. www.halfbakery.com as a collection, but be prepared to refine or focus your search within it, noting the credentials of some of its contributors and respondents in the process), to the experimental 'commercial' or 'serious' applications (eg. www.abc.net.au/landline/stories/s357323.htm), to the level of small scale hobbyist interest. For this type of background research I think it helps if you have the sort of mind that is good at amassing technical trivia from not obviously relevant sources, and then accessing it on demand like some sort of low-grade idiot-savant.
Given that development, at least to experimental or pilot plant level, is by no means really recent, one has to conclude that the economics of desalination, or more precisely in terms of your original post, the economics of disposal of what is described as a by-product or 'waste' in this context, is seen as uncertain or unviable. For example, I did not learn of solar pondage from the net: I read about an application of it for remote area power supply (RAPS) near Alice Springs in, if I recall correctly, the Omega Science Digest back in the early 80s.
It is my fear that concerns are being fanned with respect to such things as brine disposal as an outworking of that art form at which Australia has increasingly begun to excel, the creation of artificial shortage in a land of potential plenty. Google 'hot rock', look at the potential of the resource, look at how advanced the prospects are, then ask why so little has been heard of it. Could it be that there are established interests, and I don't necessarily mean commercial ones, that wish to be very selective as to which developments are allowed to proceed, or at what pace? It is interesting to note that perhaps the biggest take-up of a natural energy based technology in Australia has been at the domestic level, for hot water supply. Perhaps that's the level from which to expect future results.

Gonzo,

A further innovative use of salt may derive from its property of being, typically, an hydrated crystalline solid. Heating will drive off the water of crystallization. The anhydrous sodium chloride resulting could be regarded as a dessicant. Once having cooled down, it will absorb water from its surroundings to re-crystallize. In places where there is just no liquid water, be it saline or fresh, but a suitable heat source is available, anhydrous sodium chloride could conceivably be used as an extractive medium to get water from atmospheric humidity or damp ground. The water could be driven off by heating the crystalline salt, and then condensed and stored as liquid water ready for use. The anhydrous sodium chloride (and/or other salts) could then be re-used to repeat the cycle.

Hydrated sodium chloride could also be viewed as an evaporation-proof storage for water in an extremely dry environment. Scattered rain showers falling under conditions where high and almost immediate evaporation is the norm could in this way come to be a usable resource.

It is not beyond the bounds of possibility that where there is a need to store heat, as in providing for the diurnal interruption of solar radiation in a solar/electric energy system, so as to permit round the clock generation of electricity, that sodium chloride could be the fuzed salt used. Condensed water of crystallization would be a by-product. Not exactly co-generation (another buzz-word), but certainly a complementary product.

It is difficult to see this particular use of salt becoming of wide applicability, but there are believably inhospitable locations within Australia at which such a system may prove viable. There is also often plenty of salt, with the prospect of more to come. You asked for innovation Gonzo. Here some is.

The real beauty of this proposal is that there is a real prospect that you could avoid perhaps not an Environmental Impact Statement, but the need for statement of any environmental impact within it. Nothing for the unproductive regulators to pontificate upon! What pure joy!

Well....

You can use salt to power a desalinator.

http://www.cryogenic.net/spdesalinator.html

Sylvia.

Sylvia:

My initial thought was "no way" but there may be some merit in this concept as a starting point.

A couple of queries -
1. if you have a spring overcoming the piston then it would need to be VERY light given that the osmotic effect would have very little inertia. Ever thought of having a double acting process.
2. I would imagine that the added salt could be achieved by having 'ordinary' water (that is the water going through a conventional RO) on the outside of the membrane and a waste stream from a conventional RO on the piston side.
3. There is no provision for the waste stream - any thoughts.

I can just picture a bank of these things chuffing quietly away producing reasonably low salt water.

Forrest:

I am not ignoring - just digesting. Been looking at a number of sites and need to consolidate in a way that my boss still thinks I am working...

Gonzo,

I don't know that the concentration gradient between RO input and RO brine output would typically be high enough to drive the design as it stands. The design could be modified so that the piston is split into two with each half having a different area, and then it could work, albeit at considerable extra complexity (high pressure piston seals, for example).

However, all that really amounts to is making the desalinator more energy efficient at the expense of additional hardware, which means more cost. There are already cost versus energy efficiency trade-offs in desalinator designs. If one wants a more energy efficient desalinator, then I imagine that there are cheaper ways of achieving it than by bolting on a variant of my non-patent salt-powered desalinator.

As with so many ideas, it's the economics that kills it, not the physics or the engineering.

Sylvia

Sylvia,

You haven't been reading my post on GrahamY's topic "James Pollack is driving a case, but does he drive a car?" have you? I confess to instantaneously thinking the worse of you that you were pulling my leg, because your invention does look horribly like a variant of a perpetual motion machine. I'm still not sure (mine is a pedestrian intellect-I will have to check the physics of it), but you just may be onto something. Should it be that there is a flaw in the theory (its not instantly obvious), then good one, you got me in!

Should it prove to work, would it detract too much from your right to have the device identified with you to suggest that you share the naming rights with James Watt of immortal memory? (You know, he of the steam engine and industrial revolution.) The device to become known as the Watt-Else salt powered desalinator.

And in the event of it being a vicious, wicked hoax, being named the "Else-what? green-baiting perpetual osmosis oscillator".

Right or wrong, this will bring out the latent Luddite in every control freak. You will be put under a fatwah for daring to dream of such a thing! And as for doing it for your own amusement, well, what contempt for the suffering of parched, dehydrating humanity you display. What an insalt!

Forrest Gumpp, I promise you it's no hoax. That energy can be extracted from a combination of solutions at different concentrations is well established physics.

See http://exergy.se/goran/cng/alten/proj/97/o/ for a discussion about using salt to generate power.

My salt powered desalinator is simply using that energy in a particular way, to drive a RO desalinator. In the process it reduces the difference in the concentrations of the two input solutions by transfering water from the lower concentration to the higher one, which is why the input solutions have to be replaced after each cycle. The combination of input solutions is really just a kind of fuel, albeit an unusual one.

Now, someone might be tempted to try to run the thing off its outputs. Doing that would be as naive as trying to run an electric motor off the output from a generator that the motor drives, and would be equally unsuccessful. There are energy losses in the system, so it cannot be expected to work that way. Consequently, it does not even approach being a perpetual motion machine, any more than the motor-generator set up does.

Providing the high concentration input solution would involve either digging up salt lakes and transporting the salt to the coast where the desalinator was, or establishing huge evaporation ponds. Either way, the economics don't stack up. Perhaps it could be made to run off the brine output from a conventional RO desalinator as Gonzo suggested, thus increasing the net energy efficiency, but as I've said, there are surely cheaper ways of achieving that result.

Sylvia.

Sylvia, Sylvia,

You are right! Have just re-read (after over 40 years) the chapter on osmotic pressure in Booth & Nicol; Physics: Fundamental Laws and Principles, pp 151-157. "How the brain doth ossify, and the flex of thougt embrittle with the years! And now, to horse! Ere this day pass we shall have seized Es Salt. England shall yet outshine fair Aquitaine!" (Shakespeare, Richard I, Act III - perhaps more well known from the film "The Lion in Summer")

You may be a little hasty in suggesting the economics of it do not add up. I can think of one place where a shortage of fresh water, highly concentrated brine, high evaporation and the availability of seawater are in close proximity: the Dead Sea; Israel, and Jordan. Construction of a tunnel from the Mediterranean to the Dead Sea has, I think, been considered for hydro-electric generation alone (there is a drop of around 1,200 feet, if you know what they were): perhaps the prospect of salt powered desalination may move this project into viability, and the Med-Dead scheme come to life. Loch Haim!

This invention has started out a bit like the Light Horse charge at Beersheba in 1917. An eyewitness account has it that "at the start of the charge we were all laughing, the Bedouin were all laughing, even the Turks were laughing." At the end of the day the Light Horse held the wells, the Turks were gone, and the horses all got to have a drink. (Incidentally, the Light Horse took the town of Es Salt, located in either present day Jordan or Syria, during the two-pronged advance of 1918 under Viscount Allenby of Armageddon.) Sylvia, you may yet have a tree planted in your name in Jerusalem.

Gonzo,

Boy, are you in deep dudu! Here you were, surfing the net in the boss's time, and a world-shaking invention bursts on the scene right before your eyes. What are you going to do now? You need a good spin doctor, mate.

Forrest Gumpp

You mean that by publishing instead of patenting, I've forfeit my chance to become feelthy reech?

That'd be right :(

Sylvia.

Gonzo,

It appears as if we have been subject to a paradigm shift in topicality, rather than a thread hijack. Re-categorized. The thread has merely been displaced in the space-time continuum. I hope the transporter delivers you to this new location undisrupted. Everything looks the same, but do not be surprised if it turns out to be a different planet. Maybe the planet Halite, orbiting the star Academe, in that part of the galaxy reserved for the punishment and exile of heretics. Only time will tell. Hope you receive this message.

Sylvia,

Thank you for the URL on Osmotic Energy. I had never stumbled across it before. I have only just skimmed through it, and maybe I have missed something, but it was surprising to see no apparent recognition by the authors of the possibility of its use for desalination, as opposed to power generation. Amazing what a difference perspective can make: I guess they don't get too thirsty or dry in Sweden.

As for forfeiting the chance to become feelthy reech, try not to feel too bad about it. All may not be lost. Indeed, the apparent forfeit may be to your ultimate advantage. You must remember how, throughout history, contemporaneously such visionaries have often been rewarded. Insalt and ingratitude oft has been the prize. This device of yours (can we call it the Watt-Else Salt Powered Desalinator? go on!) is so simple and scaleable up or down, and the small net energy input so amenable to being supplied by other natural energy sources available at the same place, that it may not have to wait for the large scale mobilization of capital to be put into production. Bear too in mind that by having put the device into the public domain you have destroyed the capacity of any large corporation to suppress the technology by buying up the patent. (Seen any Sarich orbital engines around lately?) You are now consequently probably safe from assassination or kidnap, at least from that quarter.

There are other implications of the device, but they'll await another post.

Sylvia,

You made an interesting observation in your third post on this topic about there being a need to dig up and transport salt from salt lakes and transport it to the coast in order to obtain the more highly concentrated brine necessary for the device. Why would you not go the other way, and pump the seawater to the salt lake?

The geography of South Australia lends itself to this approach. The large salt lakes, like Lakes Gairdner and Eyre constitute an enormous salt resource. The route of a seawater pipeline or aqueduct to them does not have to cross country that rises very far above sea level. Pumping would not appear to be inordinately difficult or demanding of a lot of energy. (Indeed it may be able to be achieved through wave power at the seaward end of the line.) Any eventual surplus of sea water and more concentrated brines could be disposed of by evaporation in an area already covered by salt. The land for this is plentiful and flat. There exists enormous scope for scaling up such an operation, and possibly associated solar pondage for power generation, in these sun blarsted barren wastes.

The desalted water would be piped to where it was required, presumably primarily the area around Adelaide and the nearby wine growing areas.

This approach would also overcome that enormous eco-legal roadblock that would doubtless be thrown up by the Greens, objection on the grounds of putting yet more salt into the sea. You would be taking salt and water together FROM the sea!

Sylvia,

Regret to report potentially enormous problems with respect to applicability of the Watt-Else Salt Powered Desalinator in the context of the Med-Dead Power/Water Scheme in Israel and Jordan.

Reports to hand indicate difficulty in the two states reaching agreement on the share of any net electricity surplus arising from the hydroelectric part of this scheme. The Israeli position is thought to be that since the declivity down which the seawater will fall to generate the power is all in Israel, so too should Israel be entitled to all electricity generated. It is difficult to resist this logic. The Jordanian view, on the other hand, is that the whole scheme is in a bit of a hole without their agreement. All of this, strictly speaking, has nothing directly to do with the desalinating device, except that it is because of the desalinator that the hydroelectric aspect of the scheme is viable. It gets worse.

It seems there is a much larger problem, an essentially theological one, anticipated. It is expected that the fact that this revolutionary salt powered desalinator was invented by a female nudist infidel Australian JUST FOR FUN will pose (no pun intended) a problem for some Islamic clerics. It is considered that such clerics will ensure that a problem is created for the Jordanian government with respect to its being able to use such morally tainted water from an infidel invention. From the Israeli point of view this could well be viewed as a positive development, in that Israel could agree to take all of the morally tainted water produced, as well as all the power. The question is, would the Israelis be smart enough to do this?

There is thus a basis for conflict. Perhaps you could pour water upon troubled oils by agreeing to submit to divine judgement; walking the length of the Arabah covered from head to toe in a burkhar as penance, to stand, at the end, where Lot's wife stood, look back, and see if you get turned into a pillar of salt!

Hi Forest, Gonzo & Sylvia,

Yes Solar ponds are an ideal form of renewable energy for Australia and fit in well with our situation (saline aquifers, lakes, cheap land etc). They have been overlooked in our national strategy (if there is one lol).

Our group www.gsen.org is working from a community approach (city country community partnerships) toward getting a large demonstration solar pond system up and going on saline water from the SA murray salt interception scheme. We are working with land holders to enhance their operations as well as solar desalinating our own water. We will be using both the raw heat for various projects as well as generating electricity with a rankine cycle engine

If you are interested in knowing more about the community approach and the solar ponds please email the address in 'contact us' on the website (web presence is still in early form - more effort being placed on the actual community network).

Thanks for the great discussion and look forward to hearing from you if you are interested - Rob Paterson

Sylvia / Forrest:

Have been speaking to a few scientists at CSIRO about the viability of the "Sylvia Salinator" and they, whilst not overly excited, have pointed me toward the UNSW membrane research facility.

I am involved in a number of Industry steering groups and have a few contacts around the place and would like to advance this thing to a trial stage. the concept of 'perpetual flow' seems to have merit and, my idea, would be to have a number of these 'chugging' along producing small amounts of purer water - provided the capital investment does not become prohibitive.

Sylvia - I have/will not forget the fact that this is your baby and will run progress by you if/when it occurs for your comment and approval. Early days yet but we need to keep the acorn in mind.

Gonzo

Mumut (Rob):

this is good and will visit the site and contact you through this.

Gonzo.

Gonzo,

I still think it will be defeated by economics, at least in most places. The Dead Sea situation highlighted by Forest Gump may be an exception, but then you have the issue of the costs of developing a technology to the level of being a production system where there is only a narrow scope for its use.

Still, I'm happy to be proved wrong.

In the mean time, I'll have to go back through my list of wacky ideas to see whether any of them might stand up after all.

BTW, my realisation that a desalinator could be salt powered came after discussion in a Usenet NG about someone's [1] idea of desalinating sea water by immersing a long pipe with a RO membrane at the bottom end. It's another idea that sounds implausible at first, but the physics stand up. With a long enough pipe, you get freshwater at the surface because of the difference in density between salt water and fresh water.

Unfortunately, when you do the sums, it turns out this can only work in about one place in the world - Challenger Deep.

Sylvia.

[1] See Joon Cook's "Magic Technology" thread here at http://tinyurl.com/ychejh

Gonzo, Mumut, and Sylvia,

Good to see the continuing interest in this subject. An aspect of the Med-Dead or Red-Dead projects at the Dead end (yes, keep reading) is the trade-off possible between hydro-electricity generation and desalinated water production from reverse osmosis (RO) powered by the hydrostatic pressure at the Dead end of the penstocks. As with any hydro project, water flow, and therefore generation can be timed to match demand peaks. RO can be an off-peak application from essentially the same capital investment. This is of course already a planned feature of these projects. The limiting factor is of course the ability of the Dead Sea to accept seawater inflow on a continuing basis. This is determined primarily by the evaporation rate from its surface.

The relevance (Watt-Else?) of Sylvia's idea for the inverse of osmotic power generation in the Dead end context is that it permits more production of desalinated water from any given inflow of seawater to the basin. In the political context of the Med-Dead and/or Red-Dead projects it potentially permits Israel to proceed unilaterally with these projects because it can avoid raising of the Dead Sea level, and therefore the need to otherwise negotiate such possible rise with another riparian state, the Hashemite Kingdom of Jordan. It also preserves existing Israeli investment in such facilities as the Dead Sea Potash Works from threat of immediate inundation. That is not to preclude immense advantage being gained by both states from an agreement to raise the level of the Dead Sea significantly, thereby greatly increasing the area of evaporative surface, and, ultimately, the generating and RO capacity of the scheme. It would be very interesting to sea how the numbers stack up in relating hydrostatic RO to salt powered RO production; whether the project ends up in the Red, Dead in the water, or much more than mere vapourings.

But of Watt-Else than academic interest is this to us in Australia, where it has become a very dry argument around the bar (of Parliament)? More soon.

A Lofty Ambition: Desalinating, Naturally

In South Australia all of the factors but two that are present in the Med-Dead project are present near Adelaide. One that is missing is an international border, and that is no loss. The other is a hole in the ground the like of the Dead Sea basin. This latter deficiency can conceivably be compensated for by something that the sea south of Adelaide has. Waves. Most of the time reasonably big ones.

With the aid of hydraulic rams powered by wave energy, seawater could be pumped to reservoirs on the Mt Lofty ranges. The hydrostatic pressure at the bottom of penstocks from those reservoirs down on the plain could be used to desalinate some of this water by hydrostatic RO. Surplus more highly saline by-pass seawater could be either discharged back into St Vincent's Gulf, or accumulated for concentration in salt pans to the north along the gulf as brine to drive Watt-Else salt powered desalinators at near sea level. The brine ponds could be constructed and operated as solar pondage, generating the all-important non-fossil, non-nuclear sourced electricity for the grid that will help meet 'greenhouse targets' and make (South) Australia look to be a good environmental world citizen. (Bow, scrape, grovel.) Any surplus seawater pumped to Mt Lofty reservoirs could, of course, be used to generate hydro-electricity and/or be supplied under gravity flow to large salt pans like Lakes Torrens and Eyre for use in more extensive salt powered desalination and solar energy collection in solar ponds.

Such a plan would use low-tech simple componentry, and make extensive use of existing infrastructure assets. Its implementation could be modular. It would thus seem to be a project that could start out on a relatively small scale, even being amenable to being prescribed infrastructure for specific developments or development localities, investment in which may be a condition of the grant of development approval. I seem to keep coming to this same conclusion: who needs, even in SA, Malcolm Turnbull and his pipeline for Constitutional change?

Gonzo and Mumut,

You have probably picked up on this anyway, but, just for the record, it should be observed that one of the links that Sylvia supplied (in post 11 in this thread), deals with the inverse of the salt powered desalinator, that is, the use of osmotic energy to generate electricity (or for that matter hydraulic flow). It was an analysis in a Swedish context, and although the recommendation was that the electric utility that commissioned the study should not proceed to develop the concept, there may be factors in an Australian context that would, today, warrant an examination of this osmotic energy proposal.

My reason for raising it is that, just as the hydrostatic desalination/hydroelectric combination of the Med-Dead project is capable of being fine tuned for trade-offs between the two products, so too can there be power generation/desalination trade-offs with the Watt-Else salt powered desalinator. It is just possible that either remote area power supply requirements, or a requirement to pump away accumulated concentrated brine from the Murray salt interception scheme, may make viable this application used in combination where the economics of it might not warrant development individually.

In perusing the www.gsen.org website I did note that there existed some concerns as to the desirability of unlined collection basins for saline water. Should there be significant accumulation of brine, perhaps you should look at periodically pumping it to Adelaide (Mt Lofty storage specifically) as stage 1 of the Lofty Ambition hydrostatic RO project. If salt interception scheme brines can be piped to pumping stations on the existing water supply pipeline and there accumulated, it may be possible with the use of pipeline 'pigs' to periodically send batches of brine up the line for diversion to the appropriate reservoirs above the city.

Note also the round-the-clock generation possibilities in small-scale applications of osmotic energy electricity generation. There is thus the potential for overcoming the problem of intermittency associated with solar or wind power in RAPS applications.

Very interesting discussions, everyone.

Our network will be putting hot water from the solar ponds into conventional solar desalinators (increases their efficiency 2-3X). Your pressure desalination also sounds interesting.

The reference to poor salt disposal basins on the SA Murray Salt interception schemes on the gsen website refers to what is going on now.

Based on a flawed 1980s EIS, existing and planned basins are simply farming valleys where saline water is dumped and assumed to safely "leak" 70% of their water into a deep aquifer (MGA) and not cause problems for centuries. (This is proposed so as not to need so much land and increase community acceptability - lol).

The flaw is that there is no significant free capacity in the MGA and saline water is getting into local aquifers / water mounds - causing land desalination & rightly concerning locals (the latest basin is somewhat more acceptable - an old evaporation basin (Noora) below river level).

In the Riverena eg Wakool / Tullakool large proper basins have been constructed with low leakage rates - nearly 1000 Ha of them can be completely dried out so salt can be bulldozed away (the safest solution). Not in the SA instance though - no attempt at properly constructing basins - SA recalcitrant on this one.

Our project is a community attempt to use the saline water as a resource and thus make dealing with it properly palatable / profitable. regards Rob

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.