The oceans contain vast amounts of energy, yet hydropower technology has struggled to advance due to the engineering difficulties of creating turbines capable of resisting the huge forces that can be exerted on them. Water is 800 times denser than air, so hydro turbines must be able to withstand far greater pressures than wind turbines.

Hydro power from the oceans tends to be generated via tides, or waves.

Tidal currents are some of the most reliable and predictable source of energy on Earth, yet to make use of this energy in the past a large dam would have to be constructed in order to block the flow of water and make use of the tidal movements in that way.

Ocean Renewable Power Company (ORPC) designed the TidGen; a 98 foot by 31 foot structure that sits in free flowing bays of river, at a depth of around 60 to 150 feet. The company installed its first unit in Cobscook Bay in Maine last summer, where its permanent-magnet generator, located between four turbines, can produce up to 150 kilowatts, enough to power 25 homes. ORPC is now working to develop 5 megawatts of capacity over the next few years.

Wave energy is more common, as it doesn’t need special bays of river estuaries, and is basically available in any large body of water around the world. However it is also much tougher on the energy generating technology which can be thrashed around in the rough seas.

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40South Energy, of London, has developed a new way to take advantage of wave energy which avoids the violent abuse of the generator. Its product remains submerged under the surface the entire time, protecting it from the worst of the crashing waves the top half of the machine is then tugged and knocked around by the waves, causing it to pull against the bottom half which is attached to the seafloor. The first unit will be installed near to Tuscany, Italy, and will produce 150 kilowatts. 40South Energy is now working on creating a 2MW version.

By. James Burgess of Oilprice.com