Ships that harvest electrical power from ocean waves


Courtesy of GLOBE SERIES

Electrical power generation from ocean waves is possible from ships that harvests wave energy through daily trips to offshore locations and that return back to port for the delivery of energy to the grid.

Energy is stored locally on the vessel during harvesting phase and placed on the grid during periods of high demand (normally mid-day).

Unlike conventional wave-power devices, the ships would not need undersea cables to link to the electricity grid, says  Andre Sharon  at Boston University and the Fraunhofer Center for Manufacturing Innovation, also in Boston.

These cables typically cost more than $500,000 per kilometre and account for a significant fraction of the cost of conventional wave-generated electricity.

This idea of mobile wave energy harvesting is a simple one: you put wave energy harvesters on boats, send those boats out to sea, they sit out there for about a day riding the swell and charging their batteries, and then they come back in to shore and offload their electrical cargo.

There's no complex and expensive undersea construction, no need for cables to run back to shore (at $1 million per mile), you can move the generators around easily, and best of all, one can retrofit ships to do this relatively cheaply.

Each 150 foot ship (like the concept pictured above) would be able to harvest about one megawatt of energy per hour, which is enough to power about a thousand homes.

It would store up 20 megawatts in giant batteries over 20 hours at sea under average conditions, and then head back to port and pump all of that power into the grid. Once the transfer is complete, the generator can go back out again for another load.

The batteries are planned to have a capacity of 20 megawatt-hours, so the ships would have to stay at sea for at least 20 hours for a full charge. Sharon presented the concept at the  Clean Technology 2011  Conference and Expo in Boston.

Testing of scale models suggests that power produced this way could be as cheap as $0.15 per kilowatt-hour, which is half the cost of solar and between half and a third the cost of conventional (stationary) wave harvesters.

The residential consumers in the U.S. pay on average anywhere from $0.09 to $0.16 per kilowatt-hour, so this could definitely be a viable method for coastal areas.

Customer comments

  1. By Bruce Campbell Ogilvie on

    Would this method work in the Great Lakes? Is it a potential solution to the NIBY thinking about WECS offshore? What about the battery discharge/recharge during low wave action days - what level of rise and fall (in feet) required?

  2. By Ken Upton on

    Eureka Magazine Wave rockers and wave swingers have been invented years ago by the The swingers can look like swans ,so yes Bruce ! they would work in the great lakes . But you would be better to use our new REH principle of TAWT non stop REH in the streams going into the lakes . Tangential axis wet turbines .using wet kite kenapes rotors work in shallow running water ,rapids ,white water, sewers , tidal no size limit . Either static on the riiver bank ,dock ,bridge ,piers ,weirs etc or floating raft craft . That could also have storage ballast fitted or direct or over head shore output cables .

  3. By Evagelos Korais on

    In order to get the ship out there for 20hours, and bring it back u ll burn fuel. Also transferring the electricity to the grid afterwards will provide with energy losses. My question are you sure going through all that will actually have an effect on a reduced carbon footprint(for energy generation) and also, is it going to be financially feasible?

  4. By Ken Upton on

    this is where you new TAWT kenapes Scrap the ships in a intelligent way .as they are designed to rot. Use ecofrog floating reef bases in super-fused reuse ceramics and marine concrete near in shore .Ecoreef tunnel technology for the cables. Win Win win all the way ,food and power to cook it on and work for the unemployed

  5. By Michael Soldner on

    Is battery technology up to this? Surely if it was we would be storing excess from wind generation and feeding it back at peak times. Storage is the key. I love this idea but I think that costs and efficiency losses (and the embodied energy of the batteries) may show this to be a less attractive option than potrayed here. I love the sound of it but as always the devil is in the detail.

  6. By David Hunt on

    This is well worth exploring more, the Aegir Dynamo would be ideal as it converts 86% of the energy collected to grid compatible electricity, this efficiency allows it to be very cost effective and thus would collect more electricity in a shorter time than other technologies. it would easily be designed to work as part of the vessel. It is patented and Ocean Navitas would welcome enquires from intrested parties. check out for a breif overview of the technology.

  7. By David Hunt on

    Re last comment The ship could be electrically powered to maintain Co2 neutral emmissions.

  8. By Ken Upton on

    Wave go up and down to the wave height but using the pitch of the wave which on a rough average is about 30 times greater . This can be the deck length of a suitable craft ,if the design is right , a much bigger sea saw effect can be used to collect the wave energy . (watch some ocean racing of multi hulls) Weight on a craft deck near the waterline can be almost unlimited.Add a few mega EV wheels as it going to take a lot of stopping 14 times per min .If ships technology is used .it can be moved to anywhere you need REH and towed into port for servicing etc Fixed units in my opinion are a waste of time ,as there is not much the sea cant wreck But you will find its impossible to get any good funding for any idea that could effect the old school and their fossil fuels set ups .

  9. By Jacob Bitsadze on

    such trimaran was invented in 1997. This can be looked under link: