🚀 go-pugleaf

Eunometic wrote:

> "Stan Pierce" <tpierce@bigpond.net.au> wrote in message news:<SF3fd.38430$5O5.269@news-server.bigpond.net.au>...
> 
>>"Sylvia Else" <sylvia@not.at.this.address> wrote in message
>>news:417cb994$0$32547$afc38c87@news.optusnet.com.au...
>>
>>>
>>>Sylvia Else wrote:
>>>
>>>
>>>>
>>>>Eunometic wrote:
>>>>
>>>>
>>>>>hubbca2003@yahoo.com.au (Carole) wrote in message
>>>>>news:<77ed1283.0410200711.bd4e58b@posting.google.com>...
>>>>>
>>>>>
>>>>>>bernxard@yahoo.com.au (The Enlightenment) wrote in message
>>>>>>news:<39556695.0410190559.643eb88f@posting.google.com>...
>>>>>>
>>>>>>
>>>>>>>Australia has always been a country sparse in water resources.  We've
>>>>>>>all known this since childhood and have always known that we need to
>>>>>>>manage the resource wisely. Why then have the Laboral elites been
>>>>>>>increasing Our population through immigraion at a rate of 130,000 per
>>>>>>>year?
>>>>>>
>>>>>>
>>>>>>There was a 4Corners show on Monday. Ticki Fullerton interviewed Bob
>>>>>>Carr and others and the show discussed feasibility of different
>>>>>>options from turning sea water into fresh water and recycling grey
>>>>>>water for human consumption which is being done successfully in some
>>>>>>countries.
>>>>>>http://www.abc.net.au/4corners/content/2004/s1220624.htm
>>>>>>
>>>>>>
>>>>>>
>>>>>>>The latest scheme is to divert millions of mega-litres of water from
>>>>>>>the shoalhaven river to Sydney (where 60% of migrants settle).  This
>>>>>>>is ofcourse not really Sydneys water but should belong to the region.
>>>>>>>
>>>>>>>We will go through a phase of diverting a few minor rivers (at great
>>>>>>>expense for little gain) the effect of which will be to further
>>>>>>>worseneing environmental flows and changing the ecology of these
>>>>>>>rivers, we are begining some farcical water conservation measures
>>>>>>>which will in general add progressively higher expenses for
>>
>> diminising
>>
>>>>>>>returns.  All of these measures will only stave of for a short time
>>>>>>>the increaes in annual water bills of possibly a thousand dollars per
>>>>>>>household that will be needed to support coal powered desalination.
>>>>>>>
>>>>>>>Immigraion has of course become a sacred cow: driven by ethnic
>>
>> special
>>
>>>>>>>interest groups and pandering politicians, driven by businesses who
>>>>>>>desire market growth and cheaper labour for their lacklustre
>>>>>>>management and owners.  Driven by wealthy pro-immigration post war
>>>>>>>Jewish immigrants such as Frank Lowey, Richard Pratt and Lou Solomon,
>>>>>>>driven by brain dead lunar leftists.
>>>>>>
>>>>>>
>>>>>>Carole
>>>>>>http://www.austarmetro.com.au/~hubbca/water_agenda.htm
>>>>>
>>>>>
>>>>>
>>>>>I had a look at hoth links that you provided.
>>>>>
>>>>>The first link, to the 4 corners site, starts of "once we had water to
>>>>>waste".  This is rubbish.  Australians DON'T waste water or use
>>>>>unreasonable quantities though there is room for improvement in
>>>>>substance there is not too much to be done.
>>>>>
>>>>>They are trying to put a guilt trip on Australians to distract from
>>>>>their own neglect and mismanagement of water resources and yes of the
>>>>>population they have irresponsbly doubled in Sydney over the last 25
>>>>>years and continue to do so.
>>>>>
>>>>>We are all going to pay and the quality of our lives will lower.
>>>>>
>>>>>Desalination is possible but at a great cost.  The price is 4-5 times
>>>>>that of rainwater collected in Dams and inevitably it requires energy
>>>>>that will only add to Greenhouse effects and our energy dependancy.
>>>>>The energy requirements are around 10kw.hr/kLitre for reverse osmosis
>>>>>and 4 kw.hr/kLitre for multistage flash distillation a process which
>>>>>while efficient requires expesnive decalcination.
>>>>
>>>>
>>>>Anyone calculated the minimum theoretical power requirement? I'm rather
>>>>surprised that reverse osmosis is that inefficient.
>>>
>>>OK, I did it. The figure I get is only 0.6 kWHr/kL, which is
>>>surprisingly low, and rather implies that the best technology currently
>>>available is only 15% efficient. It also seems to imply that reverse
>>>osmosis heats the water by 8 degrees celsius. Anyone know whether that's
>>>right?
>>>
>>>Sylvia.
>>>
>>
>>Dissipation of heat from the pump.
>>See section 4.  http://urila.tripod.com/Seawater.htm
> 
> 
> 
> The last time I checked the minimum requirements for seawater was
> about 8-10kw.hr per cubic meter.  The paper your link points to claims
> that the current state of the art is generally somewaht over
> 2kw.hr/cubic meter.  The best real world example I have found is
> around 3.4kw.hr cubic meter eg:
> 
> http://www.lifestreamwater.com/sw9264.html
> 
> However the manufacturers claims have to be taken a little carefully. 
> Seawater salinity varies quite a bit and I imagine they will base
> their specifications on rather low levels of sea water salinity.  Also
> there seems to be a need to add a considerable number of
> anticalicfication, descaling and pH adjustments both pre and post
> treatment that must add considerably to the energy costs (eg in
> synthesis): certainly the excellent article you provided points out
> that the whole cycle is designed around the need to preserve pre
> treatment chemicals.
> 
> I have come across multistage flash distilation systems that manage
> around 2.4kw.hr/cubic meter.  Their performance is good but the
> limitation is the more problematic descaling (some sea water minerals
> precipitate at raised temperatures) and the corrosion issues involved.
> 
> These generally use waste heat from a gas turbine to heat water while
> the motive power of the shaft is used to generate the succesively
> lower levels of pressure for the succesive reduced pressure
> distilations.
> 
> 
> The best material for these plants would be Titanium due to the
> corrosion issues: There may be progress in obtaining dramatic (4:1)
> Titanium refineg cost cutting driven by some British researchers who
> have found new ways of refininbg cheaper and more plentifull ores. 
> This would make these plants more attractive.

The figure I gave was based on purely theoretical considerations. There 
is a performance that cannot be exceeded no matter how clever you are 
because the osmotic process can be run the other way to create a power 
generator that runs on fresh water and salt water. It would clearly be 
nice to run a desalinator (of whatever sort) in conjunction with an 
osmotic generator to get a self contained source of power. Since this is 
presumed to be impossible, it must mean that desalination cannot be done 
by any method for less power than an osmotic generator could produce.

There's a paper about osmotic power generators somewhere on the net from 
ABB. Their conclusion was that it was tehcnically feasible, but not 
commercially viable.

Sylvia.