STOCKHOLM, Sweden — As the waters rush together in a torrent, the fresh is drawn toward the salty in a chemical reaction that creates pressure powerful enough to move turbines.

For now, they are little turbines. But they demonstrate the enormous potential for generating energy where river meets sea.

When researchers at the Norwegian Institute of Technology (NIT) started the hunt for new and revolutionary power sources more than a decade ago, they turned to their country’s 155,000 miles of coastline. In 2009, Crown Princess Mette-Marit inaugurated the world’s first seawater power plant, by drinking a cup of tea boiled in a kettle fuelled by osmosis — or, more precisely, osmotic power.

“The potential could cover 50 percent of the current energy consumption of the European Union,” said Stein Erik Skillhagen, director of the seawater power plant that sits on a fjord 37 miles south of Oslo.

The plant uses osmosis to generate electricity: Freshwater and saltwater are guided into separate chambers divided by an artificial membrane, where the freshwater is drawn toward the seawater. That exerts pressure on the saltwater chamber, and that pressure moves turbines that generate electricity.

“The seawater draws the freshwater toward it, and reaches balance between the two fluids,” said Skillhagen. “This increases the seawater level, producing pressure.”

The concept of osmotic power was discovered in the 1970s by American chemical engineer Sidney Loeb of the University of California, Los Angeles. He died in 2008, one year before his invention finally was translated into the world’s first seawater power plant.

NIT has partnered with Statkraft, the Norwegian state-owned energy company. Statkraft is Scandinavia’s third-largest energy purveyor, producing 43 terawatt hours a year. The seawater facility produces a very small amount of power: four kilowatts, enough to power a coffee maker. But by 2012 the target is 25 megawatts, the same as a small wind farm that can electrify 30,000 households.

The main draw of osmotic power is that there are virtually no side effects from using it to generate electricity — no pollution and no drag on resources. Proponents claim the seawater energy source has almost unlimited potential. It just needs a coastline close to a lake or a river.

But all alternative energy solutions bring out skeptics, and seawater power is no exception. Three criticisms have been raised: seawater power is expensive because of the advanced technology and pricey membranes; the membranes (mostly of polyethylene plastic) remain inefficient; and the small number of membrane manufacturers poses a business threat.

Statkraft claims it can break even if the electricity price reaches at least $100 a megawatt hour, but the current Norwegian price is not more than $57. Statkraft also admits that the membranes need to be five times more efficient than they are now. And since the seawater power-plant market still is very limited, there are too few membrane manufacturers to increase quality and decrease price. Statkraft built the current power plant membranes itself.

But the plant's boosters said that if Norwegians can successfully develop osmotic energy into a commercial hit, it can be a major breakthrough in the global energy challenge.

“We really need to increase the speed to bring this technology into the market,” Skillhagen said. “We ought to do this much quicker than we did with solar power and wind power.

“Seawater power is an energy source that can deliver stable amounts of energy that, for example, wind and waves cannot, because of their variation due to weather conditions. If you combine these sources, you can get an energy mix that can be of major significance in the future,” he added.

Following the discovery of large oil deposits in the 1970s, Norway experienced rapid economic growth. Being the world’s seventh-largest oil exporter and the second-largest seafood exporter, the Scandinavian kingdom ranked as the wealthiest country in the world with the largest capital reserve per capita, according to the International Monetary Fund’s World Economic Outlook 2009 report. But Norwegian oil production reached its peak in 2000 and has since slowly decreased, creating interest in alternative energy sources — such as the sea.