Electricity has been generated from tidal power for decades. Large installations could supply entire towns and cities. However, tides are not the only forces moving water in our seas. Ocean currents also move huge amounts of water all around the globe. Is it worth exploiting this power source?

Under the influence of the Moon's gravity, the water of Earth's oceans rises and falls twice a day. Powerful forces are at work all over the globe between every low and high tide – forces that can be harnessed to generate electrical power. Just how mature is the technology and what is the potential that tidal power stations could unleash?