Twenty-five windmills, each 1.1 metre in width, have been installed on a Tokyo building, situated on the banks of river Sumida. These windmills also have solar panels attached on them and are, therefore, capable of generating solar power as well. To date, this is the largest concentration of small windmills in Japan. Each windmill generates 400 watts of electricity per hour from winds blowing at the speed of 12 metres per second. The solar panels fitted on the mills generate around 20 kilowatts of electricity per hour. The facility has been designed to supply power to a nearby gas station, whenever natural disaster strikes. Spokesperson for the Tokyo-based Zephyr Corp., the private company supplying the windmills, claims, "With increased environmental awareness the demand for these gadgets is also on the rise.' The electricity generated is, at present, being used to power air conditioning systems.