Waves - unharness-able?

Waves? Can we ever harness the power of the sea? Perhaps a new system can just do that. A Wave Power cynic thinks this might, finally, be possible.

Waves - unharness-able?

Waves; the result of the interaction of the wind against a water body over time. How many of us have stood at the coast and wondered at the power of the waves and contemplated how great it would be if you could harness that awesome power? Most of us I suspect. 

Up until now I have been very cautious about wave power. Frankly I have never thought it a viable option purely because of the immense destructive power of the sea. Remember Dawlish Warren and how it was severely damaged by a single winter storm? Waves are deceptive in their power and are more than capable of destroying any manmade structure. I have been at sea in some frightening conditions; 30m waves smashing into oil platforms making them sway like a sapling in a breeze, waves crashing through gratings and lifting them off the deck, winds of 100mph+ howling through the superstructure like a banshee. Thankfully the platforms are designed and built to withstand this sort of conditions but even so from time to time they are shutdown and downmanned if the forecast is too bad. 

The sea is a brutal Mistress, disrespect her at your own peril.

And there in lies the problem with wave power systems. In order to withstand the harshest conditions the sea can throw at them they have to be engineered in such a manner that they are either too big and heavy to work efficiently or are simply too expensive. Several experimental systems have been tried but failed for this reason.

So it was with some interest that I read about a “new” system from Denmark called Wave Star, that approaches the challenge in a slightly different way. By using floats mounted on hydraulic arms and clever one way bearings they have been able to harness the vertical motion of the waves into rotary motion to turn a generator. Initially I was sceptical about its survivability in North Sea storms but it seems they have developed it with a “storm safe” system and the prototype has been operating for some time so already survived some pretty harsh conditions albeit in sheltered locations.

Perhaps this is the key to harnessing wave power after all. Especially if, as the company suggest, it is tied in with other technologies (like offshore wind turbines). Imagine instead of just the wind turbine sticking out of the sea there are 3 of these units on each pylon as well harnessing the waves and below the surface a tidal stream turbine harnessing the tides as well. 3 bangs for your buck and only a single infrastructure install (cables etc). I can see that working especially if the offshore Wave Star can be made strong enough to withstand offshore storms. Smaller units could be installed in sheltered areas where waves in excess of 5m are extremely rare, say at the end of harbour walls or piers.

I for one will watch with interest to see how the full scale model works out.

This also got me thinking about other ways in which wave power could be harnessed but without actually using the waves themselves, at least not directly. I recall many years ago a system that used the “blow hole” principle so instead of using the waves it used the air in a “chimney” as it was forced up and sucked down by the motion of the waves in a cave below. As the water level in the cave rose and fell the air movement turned a bi-directional fan which turned the generator. Could this principle be built into the pylon of a wind turbine? Could this be built into sea defences?

Another alternative way would be to use buoys attached by cable to a drum on a generator. As the buoy rises and falls as the waves pass the cable is pulled out and reeled in by the drum which turn the generator shaft. I've used a similar system to measure distance moved by the hoisting system on a drilling rig, it's relatively simple and works very well but you do need a strong spring to reel the cable back in. Again could something like this be built into sea defences or built “upside down” on piers or bridge supports (tidal rivers)?

Water, I believe, is the key to clean, sustainable energy. Tides, Tidal Streams, Rivers, traditional Hydro and Pumped Hydro along with Water Source Heat Pumps. Perhaps we can now add Waves into that mix and start to harness the immense power reserve that surrounds our island and with a minimal impact on the visual environment.


Topics: Renewables
Tags: | Infrastructure | offshore | offshore wind | water | wave power | wind turbines
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