Wind energy infrastructure being installed across Japan was found interfering with Self-Defense Forces radars for detecting missiles, prompting the Defense Ministry to call for changes in some projects, multiple sources related to the matter said Saturday.
In some instances, the ministry also called for such infrastructure not to be installed in areas that had been singled out by the government as favorable locations for offshore wind power generation, the sources said.
The government is now considering reviewing rules governing wind power installations.
While the ministry has not disclosed specific cases, more than 10 locations, including some offshore ones, have become subject to project changes or investigations, with some energy operators asked to revise their projects, according to the sources.
However, no legislation exists that allows defensive needs to be used as grounds for restricting the infrastructure from being built on land. That has left one government official commenting that the situation could be a "defect" undermining national security.
According to the ministry, SDF radars emit radio waves that reflect off objects, with the returning signal allowing those objects to be located. But large wind turbines sometimes block the radio waves or create larger reflected signals, making those reflected off objects like missiles and planes more difficult to detect.
Onshore wind power facilities are mostly located along coastlines or in mountainous areas, with some of them within detection range of SDF radars, according to the sources. The Air Self-Defense Force has warning radars at 28 locations nationwide.
Some wind turbines are over 100 meters tall and could have a particularly large impact on radars, with some known to have hindered weather observations by the Japan Meteorological Agency in the past.
"We are troubled now because we were suddenly told to change plans we had made according to the rules," one wind energy operator official said.
"The trade and industry ministry and the Defense Ministry should have coordinated on this."
Offshore wind power generation has been touted by the Ministry of Economy, Trade and Industry as a "trump card" for expanding renewable energy, which Japan more readily embraced following the 2011 Fukushima nuclear disaster, and designated five locations nationwide as favorable for harnessing winds offshore.
But the Defense Ministry called for some waters off the coast of Aomori Prefecture in the northeast to be left alone as wind turbines installed there could interfere with radars used with surface-to-air missiles.
Concerns over missile threats from North Korea are growing as the country has ramped up ballistic missile tests this year, including one that landed in waters off Aomori in March.
In addition to the missile tests, Chinese and Russian bombers flew over waters near Japan in May, which prompted the ASDF to scramble fighters in response.
"We want to consider reviewing the system design in order to achieve the introduction of wind power while balancing defense capabilities," said one Defense Ministry official.
According to the Japan Wind Power Association, a total of 2,574 wind power turbines had been installed in Japan at the end of 2021.