New Wind Turbine Design for Offshore

Some innovative thinking here and it may end productively.  It certainly looks neat and the initial promise of avoiding cranes looks good.  Taking it further, we may be able to built it all in a normal dry-dock and then have it right itself after been moved.  That surely is an attractive design option.

Otherwise, as described it is only a good beginning.

This reminds us that there is plenty of design options presently unexplored in this very young industry..

Floating-axis wind turbine could cut offshore costs

Following Japan's decision to reduce its reliance on nuclear power after the problems at Fukushima in March, wind power is one prospective replacement. Since the nation has only a limited amount of flat land or shallow water available for installing kit, researchers have turned their thoughts to low-cost wind turbines for offshore use.

Floating-axis wind turbine

Nov 28, 2011

http://environmentalresearchweb.org/cws/article/news/47975

"A horizontal axis wind turbine on a high tower is the mainstream concept for wind turbines," Hiromichi Akimoto of Korea Advanced Institute of Science and Technology toldenvironmentalresearchweb. "However in the offshore environment we have to find another concept because it is not easy to provide a firm basis for a high tower there."

Increasingly, designers of future offshore wind systems have been moving away from horizontal-axis turbines and turning to vertical-axis machines installed on floats. According to Akimoto, many R&D efforts have attempted to stabilize offshore wind turbines so that they can keep upright in challenging environments. But he and colleagues Kenji Tanaka and Kiyoshi Uzawa from the University of Tokyo found that "discarding the idea of 'stable and upright' might lead to a new low-cost wind turbine concept".

The resulting floating-axis design contains a turbine that rotates about an axis that's roughly vertical but which tilts according to the wind. The turbine is supported on a float below, which rotates with the turbine. Swivel rollers in contact with the float pick up its motion; a generator then converts this rotation to electricity.

The roller-generator unit sits between the float and the rest of the wind turbine, above the water level. This makes it easy to access for maintenance. The researchers say their design does not need floating cranes and other specially designed vessels to install, and has a simple mechanism and low maintenance costs.

"The turbine axis is floating and its tilt angle is passively adjustable to wind force (both heave position and tilt angle are floating)," said Akimoto. "In the floater design, the restoring moment of tilt is proportional to the tilt angle. Therefore, if the device is designed for the large tilt angle, we can reduce the floater size and its construction cost."

The researchers compared the potential costs of a 3 MW version of their design, assuming a 30° tilt angle, with 5 MW horizontal-axis and vertical-axis floating wind turbines. The floating-axis wind turbine would have an installed cost per rated power 50% of that of the horizontal-axis floating turbine and 57% of the value for the vertical-axis turbine. When compared with a 3 MW shallow-water horizontal-axis turbine fixed to the sea bed, the energy produced by the 3 MW floating-axis wind turbine would be around 25% cheaper.

The team believes that the design could lead to both low-cost offshore wind-power generation and to very large next-generation offshore wind turbines.

The plan now is to accumulate information on the engineering and economic features of the concept. "I hope it will lead to the chance of constructing a small test plant," said Akimoto.

The team reported the work in Environmental Research Letters (ERL).