More Water Desalination thoughts

http://www.zonnewater.net/

 

Solar Thermal Water Desalination

 

http://www.theoildrum.com/node/3926

 

I was talking with Tony Maul on cleantech topics, and stated that solar thermal coupled with desalination of water is probably the biggest opportunity right now.

 

Essentially storing the Energy of solar thermal as Clean Water.  

Then I get the great idea to look on Google.

 

and find this article from the oildrum cross posted with peak energy.

 

And then I find this quote:

ex-NSW Premier Bob Carr used to refer to water from desalination plants as "bottled electricity"

 

I'm OK with that idea.  One of the challenges with Solar thermal is that it can scale up well, but then you've got to USE it.  And in parts of the world without an electrical grid, you're stuck with the immediate area.

 

But Water is a big need.  And creating "Bottled electricity" is an acceptable result. You are storing the solar power as clean water.  And since water is a vital resource and would be created with energy in any case, this is a reasonable form of storage. Especially as today, we have more people living in urban than rural areas.  Recognize that the nice word "urban" really means "slum" for most of the population.   As far as a social crisis, clean water can solve many problems: sanitation, health, etc.

 

Along this line of thinking, and doing some bad math:

 

http://wedc.lboro.ac.uk/WHO_Technical_Notes_for_Emergencies/09-Minimum_water_quantity_needed_for_domestic_use/images/hierarchy3.jpg

 

presume we're just trying to get to 30 liters of water per person per day.

1 cubic meter of water is = 100 liters (bad math here, go with rough of 1 cubic centimeter of water is 1 milliliter of water, and yes, I'm not going to say it has to be a 4 degrees centigrade)

 

So that's 3 people for every cubic meter of water.

 

If a city/slum holds 600,000 people (again to make the math easy)

 

http://en.wikipedia.org/wiki/Desalination

 

and we presume a price like Israel's $0.53 per cubic meter.

 

Then the 600,000 people need 200,000 cubic meters of water per day.

At the Israeli price, that's $106,000 per day.

 

At 365 days per year.

 

That's $38.7 mil per year to keep all those people with 30 liters per person.

We are obviously not doing that today.  So it means the price point must be lower.  Not just 1 or 2 cents, but significantly lower.

My current thinking is:  Why store the water on site?

If we site the purification plant near the city, near the slum, where the water demand is so great there there's no real reason to store the water itself.  You could send it, as is, when available, down the pipes to the people below. 

If done correctly, this could be a gravity based process.  It should be a gravity based process, it will reduce the power requirements, and since hot air/steam rises, you can already have the condensed water at a higher elevation.

But these systems are not out there.  And there's gotta be a good reason why not.  It can't be this simple.  So what am I missing?