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Would large-scale desalination become practical?

Posted: Thu Jul 05, 2007 8:08 pm
by JoeStrout
Again, suppose for the sake of this thread that p-B11 fusion becomes as practical and economical as Dr. Bussard projects. Would this make large-scale desalination of seawater practical?

There is currently a lot of concern about the global need for fresh water increasingly outstripping the supply. Wikipedia writes:
Fresh water is a renewable resource, yet the world's supply of clean, fresh water is steadily decreasing. Water demand already exceeds supply in many parts of the world, and as world population continues to rise at an unprecedented rate, many more areas are expected to experience this imbalance in the near future.
I see this as chiefly a problem of energy; there is plenty of water on the planet, and a lot of arid places are reasonably close to a sea or ocean. But desalination takes a lot of energy. How would polywell reactors change this equation? Can anyone estimate how much desalinated water would cost, if we assume that sea water, boron, and hydrogen are plentiful? Would it be cheap enough to irrigate deserts?

Posted: Fri Jul 06, 2007 11:53 pm
by dfryer
I guess the question is "how economical". At what price would water be affordable? Is the principle cost of modern desalination processes the energy bill or the capital investment in the facility & maintenance?

Posted: Mon Aug 27, 2007 7:38 pm
by jlumartinez
The consume to desalinate water (with Inverse Osmosis) plus pumping costs is 4 kWh per m3. A huge plant, which may involve a production of 600 Hm3 per year ( 600,000,000 m3/year), will require 2400 GWh of energy. Working continuously during the whole year is equivalent to a power plant of 2750 MW

The water consumed per Hectare depends a lot in the type of cultivated plant, the local climate (rate of rains during the year, temperature, humidity) and the method used to irrigate. As average we can estimate 5000 m3/Ha/year (even lower, 2500 m3/Ha/year, if it is only needed to supply the basic products in the 3rd world countries which doesn´t require as much water as other products). With this average basis we could irrigate 120,000 - 240,000 Ha ( 1,200 - 2,400 Km2 ) with 2750 MW !!!. ( 1 Hectare = 0.01 Km2 )

The problem for poor countries will be the capital cost of the installation. Irrigation of such a huge surface could be the starting spark for many countries to get rid of hunger.