Japan’s unique terrain and conditions offer huge wind energy potential

Japan’s coastline stretches for almost 30,000 km, offering vast potential for offshore wind energy. According to the International Energy Agency (IEA), offshore wind farms could supply Japan with more than 8,000 TWh of energy per year — more than eight times the country’s current annual electricity demand.

So far, Japan’s exploitation of wind energy has been a fraction of that by wind power pioneers such as Denmark, the United Kingdom and Germany — which between them generate tens of gigawatts of low-carbon wind electricity annually. But the Japanese government increasingly recognises the potential value of its wind resources, says Hiroshi Imamura, director and co-founder of Tokyo-based Japan Wind Energy Consulting Inc (WINC).

“The Japanese government has set the big target of 10 GW of offshore wind installation by 2030, and 30–45 GW by 2040,” he says, so construction of one of the first commercial scale offshore wind farms in Japan is currently underway near Akita, off the northern coast.

Exploiting Japan’s rich wind energy resources will not be a simple matter of replicating the template established in Europe, either for offshore or onshore wind farms. Northern Europe’s flat lands — and particularly its access to the North Sea, with its shallow waters and steady, reliable winds — has been the ideal nursery for large-scale wind farm development.

Unique challenges

In contrast, Japan’s complex and mountainous terrain, its deep coastal waters, and its earthquakes and typhoon winds will need to draw on expert local knowledge to make the most of its wind energy resources.

Until now, Japan has been a follower in wind energy development, Imamura notes. But the country is investing in wind energy research, and could become a key player in aspects of wind turbine technology particularly relevant to Japanese conditions. For example, since 2013, Japan has been developing floating offshore wind turbines for deep water use, and could become a leader in this field.

The rapid development and scale-up of wind farm technology in Europe has pushed down the cost of wind power so quickly that it is now highly competitive with other forms of generation. Today, Japan is heavily reliant on expensive fossil fuel imports, such as liquified natural gas, for its electricity. “The electricity cost in Japan is high compared with European countries,” Imamura says.

As well as offering greener energy in line with Japan’s decarbonisation ambitions, wind power would slash the national fuel bill while enhancing energy security. Each 1 GW offshore wind farm would cut a US $300 million from Japan’s annual fuel import costs, the IEA has calculated. But, the cost of wind power generation in Japan is still high compared to Europe. “The Japanese government is supporting technical research into wind power, to reduce electricity cost,” Imamura says.

WINC is participating in several research projects funded by New Energy and Industrial Technology Development Organization (NEDO) to facilitate wind power uptake. The projects include mapping Japan’s offshore wind energy potential; floating offshore wind turbine demonstration projects; and efforts to improve offshore wind measurement.

“An area of wind-energy development led by Japan, is wind farms that can withstand earthquakes and strong winds, such as those from typhoons,” Imamura says. WINC was co-founded by Imamura, and fellow wind energy researcher, Yuko Ueda, in August 2019.

Wind farm planning

“Before we formed WINC, Yuko Ueda and I worked together 10 years ago as expert members of the International Electrotechnical Commission (IEC) to propose typhoon-class wind-turbine design requirements,” Imamura says. Today, WINC has grown to eight members, including two external collaborators, and a team of three wind engineers.

Since its founding three years ago, the company has contributed to around 100 onshore and offshore wind energy projects. “Wind resource assessment, consulting for wind measurement and planning are major parts of our work,” Imamura says.

Understanding the wind resources at proposed sites is a critical aspect of wind farm planning, but this process has become more challenging and costly as wind turbines have grown in scale, notes Ueda.

Today’s turbine hubs can be more than 100 metres high, with the blade tip height clearing 200 metres, and even larger machines are in development. “Taller turbines face more extreme wind conditions,” Ueda says. “Measurement at that height is not easy, especially for Japan, where the terrain is very complex, so measurement accuracy is not so good compared to flat terrain.” While it is important to optimize the layout of wind turbines to maximize power generation for large-scale offshore projects, it is also necessary to accurately assess the effects of turbine wake.

To help with this, researchers collaborated with a team, including researchers from the University of Tokyo, WINC and other partners using Japan’s fastest supercomputer, Fugaku, to apply simulation and AI tools. These help development and testing of software for the optimisation of offshore wind farm layout, which factor in complex aspects of terrain and turbine wake.

Remote measurement

Traditionally, meteorological masts have been used to gather wind data for wind farm planning. For Japan’s relatively small wind farm developers, the cost of these masts becomes prohibitively high for tall masts and for offshore deep-water sites, Imamura notes.

The alternative approach, proposed by Ueda, with a particular focus on offshore wind farm planning, is to collect wind speed and direction measurements remotely. Light Detection and Ranging (LiDAR) instruments use lasers to measure wind parameters based on light reflection from airborne aerosols and particles.

“Measurement of wind speed at locations up to about 5 km away is available from shore-based LiDAR systems — but at the moment, precise measurement is quite difficult,” Imamura says. In an ongoing NEDO project, Ueda is now developing guidelines for offshore wind-speed measurement using pairs of LiDAR instruments, which can obtain high accuracy readings by intersecting the beams of both instruments.

As well as developing wind power technologies, a key focus for Japan will be to develop the specialised workforce required to make the most of its natural wind assets.

“Many more colleagues will be needed, especially for wind farm design,” Imamura says. “Educating people in the specialist knowledge needed for wind resource assessment and wind turbine design will become an increasingly important part of our work.”