Compared to wind and solar, tidal power is still regarded as a renewable energy technology that remains unviable on a large scale. But throw together climate change, political will in the UK and the US, entrepreneurial enthusiasm and academic research - with some significant investment - and a new mood of optimism is starting to pervade the sector.
Tidal current power, sometimes called tidal stream power, is the process of converting the kinetic energy of the tide – whether in tidal rivers (think London's Thames or New York's East River), streams or ocean waters, into useable power in the form of electricity.
The process typically involves an underwater turbine, and a plethora of devices are being developed – some in rivers or streams and others offshore. While a few technologies are past the testing stage and now feeding the grid, no company in the world has actually reached the commercial stage, delivering “proven technology”.