Some research is paying off, it seems.
More here.A "field" of cylinders built on the sea bed over a 1km by 1.5km area, and the height of a two-storey house, with a flow of just three knots, could generate enough power for around 100,000 homes. Just a few of the cylinders, stacked in a short ladder, could power an anchored ship or a lighthouse.
Systems could be sited on river beds or suspended in the ocean. The scientists behind the technology, which has been developed in research funded by the US government, say that generating power in this way would potentially cost only around 3.5p per kilowatt hour, compared to about 4.5p for wind energy and between 10p and 31p for solar power. They say the technology would require up to 50 times less ocean acreage than wave power generation.
The system, conceived by scientists at the University of Michigan, is called Vivace, or "vortex-induced vibrations for aquatic clean energy".