DOCOMO Field Testing Solar Communications Stations

Japanese mobile phone operator DOCOMO has begun begin field testing mobile network base stations powered by solar panels.
Following the Great East Japan Earthquake in 2011 that triggered the massive tsunami, communications in affected areas were severely hampered, which impacted on rescue and recovery efforts. Even in Tokyo, the mobile phone network was shut down and landline phone services were severely disrupted. 
A full day after the event, cell phone service across a wide swathe of eastern Japan remained unavailable or severely degraded.
DOCOMO set about developing disaster-proof base stations to cope with similar situations, which it has been testing at its research and development center. 
10 of the solar powered base stations will now be rolled out in the Kanto-Koshinetsu region of Japan; with the first three to appear in Tokyo, Kanagawa and Yamanashi prefectures.
If mains electricity supply is cut off during a disaster, the station can switch to battery power to run communication equipment. The base stations connect to the telecommunications network through a satellite link.
Each base station has a 4.19 kW solar panel array, more than enough to provide the stations’ maximum power consumption of 2.0 kW. The deep cycle battery banks store 14-16 hours’ worth of power that can be tapped when solar resources are not available.
The batteries can also be charged with mains electricity purchased at night-time, when costs are relatively low. 
Aside from the disaster-proofing aspect; these green base stations use less power when connected to mains. DOCOMO says it is also making progress in developing an efficient power distribution network for all base stations nationwide and an internal smart grid framework to control the distribution of power among multiple green base stations.
DOCOMO says its green base station development program may also include the use of fuel cell technologies and wind-powered base stations.
NTT DOCOMO is Japan’s largest mobile service provider, serving more than 60 million customers.