Kawasaki turbine details still under wraps

Kawasaki Heavy Industries has completed the front-end engineering design study for its tidal stream turbine, but details of a test deployment remain sketchy.

By Jason Deign on Mar 25, 2014

Kawasaki Heavy Industries (KHI) has moved closer to getting a machine in the water with the completion of a front-end engineering design (FEED) study.

The study, carried out by James Fisher and Sons and Mojo Maritime, was intended to provide detailed information around the installation, maintenance and decommissioning phases of KHI’s seabed-mounted horizontal 1MW turbine, which has been in development since 2010.

Sources close to the project are keeping tight-lipped over the exact details of the work, however.

In a brief press release announcing the completion of the FEED study, James Fisher Marine Services (JFMS) business development director Martin Dronfield went no further than to thank KHI for the contract.

“James Fisher is delighted to have been chosen to deliver this FEED study for KHI and to have worked alongside our key partner Mojo Maritime,” he said.

“The delivery of this FEED study demonstrates just how far the James Fisher group of companies has come in developing its integrated project solutions offering to the marine renewable energy market.”

Tidal energy aspirations

Richard Parkinson, managing director of Mojo Maritime, added: “We were highly pleased with the opportunity to participate in this project, allowing us to share our expertise with JFMS and supporting KHI in their tidal energy aspirations.

“The successful completion of this study yet again emphasizes the UK’s excellence in marine renewable energy.”

Sources at James Fisher have declined to comment further and a spokesperson for KHI simply says: “Currently, the company is working on design and cost reduction of tidal power generation systems. Kawasaki does not disclose further details.”

Artist impressions of the KHI device show a three-bladed horizontal-axis turbine design.

It has a seabed mounting and “probably a variable pitch set of high-lift prop blades and weather cocks to be dual-flow operating rather than single-flow directional,” according to Paul Hales, director of Hales Energy, a UK ducted side-drive waterwheel turbine developer.

The benefit of KHI’s approach, he says, is that it represents a “simple design format that the public, shareholders and investors can understand, seen as a standard wind turbine unit, water-proofed.”

Track record

In addition, he points out: “KHI has a track record in marine work and the many forms of heavy engineering work that is needed in the harsh world of marine energy. Kawasaki also has the financial and political clout to enter this new world.”

A further plus for KHI is a potentially significant home market in Japan. The country is currently one of the world’s largest importers of energy, having few land-based natural power resources.

With the Fukushima Daiichi nuclear disaster having caused the country to rethink its policy on atomic energy, Japan is now focusing on the development of marine renewables. Last year it began testing a 2MW floating offshore wind turbine designed by Marubeni Corp.

From a tidal perspective, Japan has a major ocean current system just offshore, with flow rates similar to those seen in the Gulf Stream and Agulhas Current.

This all bodes well for KHI’s entry into the tidal market, although Hales cautions that the company’s choice of turbine design may present a number of challenges.

“The basic physics of blade-foil lift devices used for most tidal stream devices give impressive turbine efficiency figures in smooth, fast-flowing test conditions,” he says. “However, in the real world such conditions are few and far apart.

“Tidal currents are turbulent over the majority of the water column. Also, the slightest marine growth on the lift surface will reduce the performance significantly.”

Water flow rates

Furthermore, he says: “Most horizontal axis propeller blade or foil tidal stream devices may be designed to cut in at relatively slow water flow rates but require normally 2.5 metres-per-second flows and above to produce their rated output.

“Only something like 5% of the world’s marine coastal waters have such flows, and often not at convenient locations.”

A final concern is that a bladed design such as KHI’s might injure marine life or become entangled in floating debris unless some form of screening is used.

With KHI reluctant to release further details of the project, the answers to these questions will have to await the arrival of sea trials.

KHI has had a full-scale test-site berth booked at the European Marine Energy Centre (EMEC) in Orkney since 2011. At the time, Scottish First Minister Alex Salmond said: “I am determined that we continue to encourage world-leading companies like KHI to work with us.”

As yet, though, there is still no news on when a KHI machine will be entering the water. “Kawasaki Heavy Industries is still contracted with EMEC to deploy a device at one of the berths at the Fall of Warness,” confirms EMEC’s commercial director, Oliver Wragg.

“There’s no device on site at present. As with all EMEC clients, it’s up to the developer to decide when the mobilisation date is.”