Wave Energy Research and Development at JAMSTEC

Offshore Floating Wave Energy Device Mighty Whale



Wave energy is an indirect and condensed form of solar energy. Several challenging engineering problems need to be solved before this nonpolluting renewable energy source can be utilized on land and/or at sea. Over the past few decades, however, considerable progress has been made worldwide, through research and developmental work on conversion technologies.

Developments in Japan began with Yoshio Masuda's experiments in the 1940's. These reached significant scales in the 70's, and since then, a number of prototypes have successfully been tested around the islands. In the 70's, the wave-energy group at JAMSTEC developed a large-scale floating prototype named Kaimei. That device was tested in the Sea of Japan, off the town of Yura in Yamagata Prefecture. Two series of tests were completed, one of these under the auspices of the International Energy Agency. In the early 80's, JAMSTEC developed a shore-fixed device for tests near Sanze, also in Yamagata Prefecture.

Since 1987, the focus has been on another floating device named Mighty Whale. Projected applications for a row of such devices include energy supply to fish farms in the calm waters behind the devices, and aeration/purification of seawater. The picture below shows an artist's impression of the proposed applications for the Mighty Whale system.

This and following images: Click to enlarge

Theoretical calculations and model tests in 2 and 3 dimensional wave tanks clarified the hydrodynamic behavior of the device, and provided information necessary for safe and economical design of the open sea prototype. The prototype dimensions were chosen to be 50 m (Length) X 30 m (Breadth) X 12 m (Depth). The design called for it to float at even keel at a draft of 8 m. The overall rated power capacity was set at 110 kW.

The operating water depth at the test site is 40 m, and the prototype is to be moored facing the predominant wave direction as illustrated below. The prototype is based on the oscillating water column, and contains three air chambers that convert wave energy into pneumatic energy. Wave action causes the internal water level in each chamber to rise and fall, forcing a bi-directional airflow over an air turbine. All three turbines on Mighty Whale are self-reciprocating, and each turbine has two rotors in tandem configuration. The turbines drive three induction generators to produce 3-phase AC output at 200 Volts.

As shown in the General Arrangement View, three buoyancy chambers are provided directly behind the air chambers, two each along the device sides, and three in the aft-most region. Two vertical fins near the two aft corners provide lateral stability to the device. In the forward central buoyancy chamber is housed a Control Cabin which serves as an onboard Measurement Station. This space also contains the control system for the air turbines and generators.

To the left is one of the turbine rotors installed on the prototype.

Shown here is a partial view of the turbine-generator system as installed on the prototype.

Prototype construction is nearing completion at the Ishikawajima Harima Heavy Industries (IHI) shipyard in Aioi City, Hyogo Prefecture. Outfitting operations are currently in progress, following which the prototype is to be towed to its test location just outside the mouth of Gokasho Bay off Mie Prefecture. Tests are scheduled to begin in July 1998, once final positioning and mooring operations are completed. Tests are expected to continue for approximately two years.

Shown below is a photograph taken during the Launch, which took place on March 24,1998.

The photograph below shows the prototype prior to ballasting.

During the forthcoming open sea tests off Mie Prefecture, a total of 48 quantities will be monitored. For the most part, the data will be recorded and analyzed on board. Many of the observed and analyzed quantities will be transmitted to a shore-based Control Room to allow monitoring of device safety and instrument operation.

Specific aims for the open sea experiments include:

These developments are funded by the Science and Technology Agency (STA).

For further information on Mighty Whale contact Project Director

Yukihisa Washio, Marine Technology Department, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Japan, 237

Tel: +81-468-67-5576, Fax: +81-468-66-5746

E-mail: washioy@jamstec.go.jp


Researchers currently associated with the Mighty Whale group are Yukihisa Washio, Hiroyuki Osawa, Masaaki Imai, and Umesh Korde. Recent Mighty Whale researchers include Former Project Directors Takeaki Miyazaki and Hitoshi Hotta, and former group members Hitoshi Yokozawa and David Pizer. Thanks are due to a number of former student researchers from Tokai University and Chalmers University of Technology, Sweden. Umesh Korde prepared this report in consultation with Takeaki Miyazaki and Yukihisa Washio; and with assistance from Yasuko Egawa, Hisae Kume and Hitomi Iizuka. Webmaster Yoshihito Arai optimized these pages.

Last modified June 5, 1998