About 200–400 large merchant ships are decommissioned and scrapped every year. In addition, the US Navy decommissions tens of naval vessels every year. In 2002/2003, the average cost of custody for a ship to be decommissioned was $25,000 per year, and $2.5 million to scrap it. The US Navy budget to scrap naval vessels in 2002 was $33.4 million. Now apparently the Navy sinks naval vessels by bombs and torpedos. Scrapping can cause pollution, health hazards, accidents and threat to the ecosystem. Can a “polluting” ship about to be scrapped be used to generate clean wave energy? Maybe! It is possible to place the ship (unmanned) in about 50 m of water where deep-water swells may have an average wave period of 6–15 s. The ship would be “tuned” to have large motion response, particularly in heave and pitch. In short waves, the ship could serve as a platform for secondary energy absorption. The idea is to tune the ship to have rigid body resonance, or close to it, and resist that motion to absorb power. A hydraulic ramp connected to an accumulator feeding a hydraulic motor that generates power is one possibility. Several other energy extraction mechanisms such as turbines connected to oscillating water columns are possible devices. These concepts together with a few preliminary numerical analyses are presented and discussed.
Ships and Offshore Structures, 2013, Vol 8, Issue 5, p. 504-516
renewable energy; Wave energy; Decommissioned ships; Wave energy extraction system; Ocean wave energy device