A team of researchers from Stanford University has estimated that rivers could provide about 13 percent of the world’s current energy needs, but they’re not talking about hydropower. Instead, they envision renewable energy based on the principle of entropy, as energy is produced when fresh water from rivers disperses into salt-laden seawater. While 13 percent might be something of an overreach given the current state of the technology, the team has developed a new entropy based system that could lead to the widespread use of river-generated renewable energy.
Renewable Energy when Salty Meets Fresh
The idea of using the interaction of salt water and fresh water to generate energy has been around for a while. In nature, the diffusion of river water into salty seawater leads to a slight rise in temperature, and this energy could be captured to generate electricity. The conventional means of capture has been through osmotic power. Fresh water and salt water are separated by a membrane, and the salt water draws fresh water through the membrane, causing an increase in pressure. The pressure can then be used in a variety of ways, for example to turn a turbine. The Norway-based company Statkraft is testing one such osmotic power facility.
Power from Entropy
Though promising, osmotic power does have one drawback, and that is the bulk of the membrane. The Stanford team approached the problem from a different angle and came up with a more compact system. As reported by Andy Extance at the Royal Society of Chemists, the Stanford system uses a battery to draw energy through a crystal lattice made of manganese dioxide nanorods, which pack a large surface area into a small space.
Salt and Sustainability
Salt is shaping up to play some interesting roles in the sparkling green future. Molten salt, for example, is being developed as a storage solution for solar power installations. Another exciting development is a fuel cell that combines desalination, wastewater treatment, energy generation and hydrogen gas production in a single process.
Image: Salt by genista on flickr.com.