Water Education Foundation
This is just one post in the Desalination Category
Click here to view all posts

Peter Gleick: Salt from water – the question of energy

Posted by: Aqua Blog Maven on June 3, 2009 at 8:09 am

From Peter Gleick’s City Brights blog:

Following up on my last post, on the cost of desalination, I thought I’d tackle a second key issue that seems to interest people: how much energy it takes to desalinate seawater.

The short, non-technical answer is, a lot. And the more salt there is in water, the more energy is needed to remove it. This is one of the reasons desalination is expensive. The other is that the equipment itself is costly – this is a high-tech, capital-intensive way to produce fresh water.

When salt is dissolved in water, it breaks the ionic bonds that hold salt crystals together. Removing those salt ions from water takes substantial amounts of energy. This is today’s Water Number:

Water Number: 0.7. In an ideal reversible thermodynamic process, a minimum of around 0.7 kilowatt-hours of energy are needed to desalinate a cubic meter (cu.m) of seawater (a cubic meter is 1000 liters, or 264 gallons). Current state-of-the-art reverse osmosis (RO) desalination plants use 2.5 to 7 kWhr/cu.m.

Read the rest of this post from Peter Gleick at the City Brights blog by clicking here.

June 3, 2009 · Filed Under Desalination

Comments

Leave a Reply