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