NHK Builds 2MW Solar Plant, Cuts CO2 Emissions at Its Broadcast Station

As you drive 50km from central Tokyo through an area filled with logistics warehouses and roughly 20 minutes from JR Kuki Station, tall towers standing out from their surroundings will come into view.
It takes a while before the car actually gets near the towers after you see them.
These are antennae of Japan’s largest AM radio broadcasting site “Shobu Kuki Radio Station,” built by NHK (Nippon Hoso Kyokai/Japan Broadcasting Corp). The 594Hz Radio 1 antenna reaches 245m while the 693Hz Radio 2 antenna reaches 215m, which is also the highest of this kind in Japan. Their capacities are 300kW and 500kW, respectively.

Programs transmitted via two wireless networks from the NHK Broadcasting Center in Shibuya, Tokyo, are aired in a medium wave band to approximately 20,000,000 households, equivalent to about 40% of all households across Japan, primarily in the Kanto-Koshinetsu region.

Radial earth – part of radio transmission antenna

The site of this radio station is approximately 95,000 tsubo (about 310,000m2). Such a huge area is required because, in order to efficiently transmit, copper wire called “radial earth” needs to be radially buried in the ground across a large area at the bottom of a high steel tower set up on flat land. Radial earth plays the role of boosting the radiation efficiency of radio waves as part of the radio transmission antenna rather than working as a safety measure for releasing electricity.

Excluding areas on which a ballpark and tennis courts were built, most of the radial earth site was left as grass, and NHK was looking for an effective way to use it. What came about was an idea to construct a mega- (large-scale) solar power plant. NHK started considering a mega-solar power plant in 2008, and constructed and started operating a plant with an output of about 2MW in August 2012 after overcoming various technical challenges

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