Intelligent Energy

Osmotic power pushes closer to reality

Osmotic power pushes closer to reality

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Norwegian utility lands major supply of membranes that generate electricity where fresh water meets salt water. NASA, DOE, Hydro-Quebec, post-nuclear Japan show interest in this CO2-free technology.

Norway’s state-owned power company Statkraft took a big step toward harnessing osmotic power today when it landed a partner and supplier for membranes, a key element in osmotic systems.

Japan’s Nitto Denko/Hydranautics has agreed to develop and make membranes for what would eventually be commercial-grade osmotic power plants, Statkraft said in a press release.

Osmotic power is a lesser-known form of alternative energy that, like wind and solar electricity, is carbon-free. It taps the kinetic push-and-pull that breaks out when you slip a semi-permeable membrane between river water and salt water. Abiding by the laws of osmosis, the fresh water forces its way through the membrane. (For those of you who haven’t re-read your old textbooks lately, in osmosis, a low concentration solution like fresh water will naturally push through a semi-permeable membrane to a high concentration solution like salt water).

Statkraft opened a small prototype osmotic plant along the Oslo Fjord in November 2009, where it funnels fresh water from the Tofte River into a chamber separated from a salt water chamber by a thin polymer membrane. The fresh water presses through to the saltwater side where the water rises, shoots through an outlet pipe, and drives a turbine.

The prototype works, but not economically enough to commercialize the technology. One of the biggest hurdles is the membrane. There are few manufacturers. That is a big impediment, because a commercial-grade osmotic plant will require a lot of it. By one estimate, a 25-megawatt plant would currently rely on around 5 million square meters (about 54 million square feet) at the least.

Today’s announcement goes a long way toward assuring a future supply. Nitto Denko/Hydranautics is a leading supplier of membranes for other purposes such as water treatment and desalination. Statkraft’s head of osmotic power Stein Erik Skilhagen (pictured), therefore hopes that Hydranautics - the Oceanside, California subsidiary of Nitto Denko that will make the osmotic membranes - has the economies of scale to produce affordable membranes tailored for osmotic power.

“This is the biggest breakthrough since the start of the prototype,” Skilhagen told me when I reached him by phone today.

The announcement should catch the attention of, among others, NASA, DOE, and Canadian utility Hydro-Québec, all of whom are investigating osmotic power or who have in the past. When I wrote about osmotic power for TIME Magazine late last year, NASA was exploring osmosis as a way to both treat water and generate electricity on spacecraft.

At the time, Michael Flynn, senior research scientist at NASA’s Ames Research at Moffet Field in California was among those concerned by a dearth of membrane supply. “If somebody comes up with a better membrane, we'll buy it,” he told me then.

In Canada, Hydro-Québec has identified 12 gigawatts of osmotic potential along the Hudson Bay, James Bay and St Lawrence estuary that would add 25% to its capacity.

Today’s announcement should also interest Japan, which is mapping out a non-nuclear energy future following the Fukushima disaster. A Japanese partnership of Kyowakiden Industry Co., Tokyo Institute of Technology and Nagasaki University are operating a prototype osmotic plant in Fukuoka City.

Back in Norway, Skilhagen said the goal in osmotic power is to generate 5 watts of electricity per square meter. He’s currently producing about 1.5 watts per square meter, so membranes have a way to go to become more permeable and durable.

The prototype plant on the Oslo Fjord has a capacity of about 10 kilowatts. Skilhagen wants to switch on a pilot plant of around 1-to-2 megawatts by 2015. That plant would likely be in Europe, but not necessarily in Norway he said.

He hopes to open a demonstration plant of about 25 megawatts by 2019, and a commercial plant of the same size running about 2 years after that.

Skilhagen thinks that globally, osmotic power could one day generate 1,700 terawatt-hours of electricity per year, which is about half the current consumption in the European Union. He envisions around 30 osmotic plant around the world by 2030.

Before osmosis gets to that stage, its proponents will have to find additional financing. Statkraft has spent about $25 million to date, about 30% of which has come from the Norwegian government and the EU. Osmotic developers are hoping for more funding, including government backing. Like the technology itself, that, too will be a story of pushing and pulling.

Photos: Cover, daviddarling.info. Above, Statkraft

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Mark Halper

Contributing Editor

Mark Halper has written for TIME, Fortune, Financial Times, the UK's Independent on Sunday, Forbes, New York Times, Wired, Variety and The Guardian. He is based in Bristol, U.K. Follow him on Twitter. Disclosure