By Carl Vansant, Editor-in-Chief
I’d like to share some thoughts about the hydrologic cycle, seawater, and innovative hydropower possibilities:
Hydrologic cycle
All types of renewable energy employ the principle of intervening in a natural process to extract useful energy. In the case of hydropower, the “natural process” is the hydrologic cycle. Through strategic placement of hydroelectric facilities, a portion of the cycle’s energy is captured for delivering benefits to mankind.
Seawater
In the context of hydropower, the role of seawater in the hydrologic cycle has been largely ignored. Yet, in the cycle, most of the water evaporated comes from ocean surfaces. During evaporation, substantial energy is required to separate the water from the salt. It’s a reversible process and, as a consequence, when fresh water and salt are rejoined, energy is released.
Hydropower possibilities
Scientists have long recognized the possibility of extracting useful energy from the energy released during the mixing of fresh water and seawater. Concepts for capturing a portion of this energy are variously referred to as “salinity power,” “saltwater power,” and “osmotic power.”
Statkraft of Norway — a major hydropower producer and the leader among today’s efforts on salinity power — is pursuing development of osmotic power. Statkraft is building upon a decade of Norwegian research and is focusing on a process called “pressure retarded osmosis” (PRO). The PRO process takes advantage of the osmotic pressure difference between fresh water and seawater.
Having a suitable osmotic membrane is essential for the PRO process to work. Consequently, an important objective of current efforts is to develop membranes that are effective and, ultimately, economical.
There’s much reason to be optimistic. In recent years, huge improvements have been made to membranes used for reverse osmosis (RO) water desalination — and RO membranes have many similarities to what’s needed for the PRO process.
The progress made in the desalination field since the 1990s is striking: potable water production costs have been driven down 100-fold! Better and cheaper RO membranes have contributed to this enormous cost reduction … and excitement abounds about possibilities that nanotechnology holds for future improvements.
Salinity power is a futuristic idea, and moving from the laboratory to commercial reality should not be expected to be quick or easy. Major hurdles will undoubtedly need to be faced and overcome. Still, Statkraft — and others supporting and pursuing salinity power — deserve great credit for leading the way on this new frontier. And, their examples as innovators can encourage all of us!
