Guardian: Damian Carrington  Tidal power is the only renewable source derived from the moon. Now an extraordinary array of devices promise to unlock this vital energy potential

Using giant kites, blades and paddles, and mimicking pogo sticks, blowholes and even the human heart, groups around the world are on the cusp of harnessing the colossal power of the oceans.

The challenge is huge – seas have been battering coasts and sweeping sailors to their doom for millennia – but so is the prize: huge amounts of clean, reliable and renewable electricity for an energy-hungry world. Taking on the challenge of operating in this savage, corrosive environment is not for the faint-hearted, and the costs remain worryingly high, as demonstrated by the government’s rejection on Monday of a £1.3bn tidal project at Swansea. “There is no doubt – shit happens during marine renewable energy projects,” says François Renelier at Bessé, a French insurance broker.

But the ocean energy sector is frothing with ideas, with hundreds of companies developing an extraordinary array of devices and backed by billions of dollars of investment. Among the serious contenders tapping rapid tidal flows are 12 metre-wide underwater kites that soar and swoop.

“We fly with the tides,” says Martin Eklund, at Minesto, which is installing a £25m array off Anglesey, north Wales. “The main advantage is we can harvest energy from very low currents. This resource is abundant – it is everywhere.” Click here to read more