Salt could shake up world energy supply

Only up to powering light bulbs so far, “salt power” is a tantalising if distant prospect as high oil prices make alternative energy sources look more economical.

Two tiny projects to mix sea and river water — one by the fjord south of Oslo, the other at a Dutch seaside lake — are due on stream this year and may point to a new source of clean energy in estuaries from the Mississippi to the Yangtze.
The experiments, which seek to capture the energy released when fresh and salt water are mixed, build on knowledge that has been around for centuries — in one case imitating the process of osmosis used by trees to suck water from their roots.

Although they are far from being economically viable, if eventually successful they might help a long-term quest to diversify away from fossil fuels such as coal and oil, widely blamed for stoking global warming.

“We might well be able to find new promising solutions such as generating power naturally from osmotic forces occurring when salt and fresh water are mixing,” Norwegian deputy Energy Minister Liv Monica Stubholt said in a speech earlier this month.

And rivers flow around the clock, an advantage compared to variable wind or solar power.
Oil, currently trading not far from a record $112 a barrel, is forecast to peak this year as a U.S. slowdown reduces demand, but analysts polled by Reuters in February still saw the average price above $80 in 2010.

The U.N. Climate Panel said in 2007 energy sources such as waves, tidal power or salt are a long way off — unlikely to make a significant contribution to overall power needs by 2030.

The science at the heart of the projects is the fact that when salt and fresh water mix at river mouths, they are typically warmed by 0.1 degree Celsius (0.2 Fahrenheit). Dutch scientists say such energy at all the world’s estuaries is equivalent to 20 percent of world electricity demand.

Guardian