Hybrid heads for second try

Offshore oil contracting giant Modec remains on course to grid-connect its trail-blazing Skwid hybrid wind-marine energy concept by next September, alleviating fears that the project might be massively delayed after part of the unit was lost at sea off the coast of Kita-Kyushu city during a first installation attempt this autumn.

The Tokyo-based company has been angling to test the full-scale prototype –  which mates a three-bladed vertical axis Darrieus turbine with a Savonious ocean current device  –  in 50 metres of water off Karatsu, in Saga prefecture, and start selling produced electricity to regional utilty Kyushu Electric later next year.

The slimline unit, foreseen for powering remote islands, is calculated to have an ouput capacity of 500kW in winds of 13 metres per second (m/s), rising toward 1MW in velocities of 16m/s.

Original deployment plans were scuppered after the ocean current turbine component snapped off the rotor axis and sank in 60 metres of water as its U-shaped installation barge  tried to navigate under a low bridge in shallow water when passing through the Kanmon Straits on its way to the demonstration site  –  a technique which Modec has rethought for the second attempt.

The Skwid's 24-metre diameter turbine has been modelled to capture twice the energy from its swept area as a similarly dimensioned conventional horizontal axis onshore turbine. 

Its split-cylinder, bucket-shaped marine turbine does double duty, serving both to jump-start the device in currents as slow as 0.6m/s, as well as actiing as a self-righting ballast to keep the machine erect in operation.

The floater, moored via a six-line spread with drag-embedded anchors, houses its power generation assembly on a set of six rubber gimbals mounted at deck-levels to buffer it against wave motion.

The Skwid, which Modec aims in the first instance to lease to fisheries co-ops to power high-intensity lights used in catching the region's famed Yobuko squid, could be scaled up to 5-10MW models.