Japan's busiest international travel hub is going green. Narita Airport near Tokyo says it will install a solar panel system that will eventually supply a big portion of its energy needs.

The initiative is a joint venture of Narita International Airport Corporation and Tokyo Gas.

They have created a firm that will install a vast array of solar panels next to runways and on building rooftops. The panels are expected to cover about 200 hectares by the time they are all in place at the end of fiscal 2045.

The system will generate 180 megawatts of power.

Narita officials say that's enough to provide 40 percent of the airport's annual energy needs.

The venture is expected to cost roughly 100 billion yen, or about 740 million dollars.