Osmotic power — prospect of sustainable energy, or water liability?
Today, Statkraft, a company in Norway, opened the world’s first osmotic power plant—a model of a sustainable energy system which uses osmosis to harness the energy of fresh water’s natural movement toward salt water through a membrane.
The idea for power generated through the movement of water, due to osmosis through a specially designed membrane, was conceived almost 40 years ago by an American named Sidney Loeb, though was eventually abandoned as prohibitively expensive. Advancements in the technology of the membranes—developed mostly by desalination plants—have spurred renewed interest in the possibility of osmotic power.
The system is completely carbon neutral, sustainable, and can run on its own 24 hours a day. Who could argue with that?
Except… where is all the water coming from? Statkraft mentions in a Q&A forum on their website that, “to achieve an output of 1 mW [their eventual goal], one cubic meter of freshwater (per second) must be mixed with two cubic meters of seawater per second.”
This equates to roughly 3,600 cubic meters per hour of fresh water, or about 1.5 Olympic-sized swimming pools; 86,400 cubic meters per day, or twice the volume of oil dumped into the Gulf of Alaska in the Exxon Valdez spill of 1989; and 31,536,000 cubic meters per year, or enough to give ten liters of water to every one of the 6 billion people on the planet who lack access to clean drinking water.
The current plant is small, in a modest testing stage—it adds about as much power to the energy grid as it takes to run a coffee maker, and uses a respective amount of water. But Statkraft plans the next stage to increase the energy output by a factor of 500 (from 2 to 4 kW, to 1000 to 2000 kW, or 1-2 mW). Ultimately, they argue on their website, osmotic power has the potential to create 1600-1700 terawatt hours annually, or about half of the current electricity consumption in the European Union.
The technology is new, and it is possible that in the future natural convergences of fresh and salt water, like deltas where rivers meet the ocean, or even man-made freshwater (treated water from a wastewater plant) and saltwater (waste from a desalination plant) could be maximized in an ecologically and water-friendly system.
The possibilities are exciting, but much like with the water-energy nexus controversies involved with solar power generation, I have yet to be convinced that this technology has the power to be implemented globally without severe environmental ramifications.
Osmotic Power Debuts in Norway (Greeninc, NYTimes.com)
World’s First Osmotic Power Plant Opens (Cleantechnica)
What is Blue Energy Anyway? Two Takes on Osmotic Power (treehugger.com)