Despite being the most widely used form of renewable energy worldwide, hydroelectricity is generally reserved for large-scale commercial installations built around massive dams. Japanese company Ibasei has shrunk things down and removed the need to build a dam with its Cappa compact hydropower generator – a system that's designed to be installed along a river or waterway.

The basic design of the Cappa is nothing new – blades rotate as the water flows through the unit, which drives a turbine to generate electricity. However, the unit is encased in a special diffuser that is designed to increase the velocity of the water at the point where it passes over the blades, thereby increasing the unit’s electrical output.

A company spokesman tells DigInfo that a water flow of 2 m/s (6.5 ft/s) will see one unit produce 250 W of electricity, while five units together will generate about 1 kW, taking control losses into account. The unit produces 100 V AC electricity at 50/60 Hz, so it can be used to power appliances around the (Japanese) home. The unit itself is also 100 percent recyclable and has an uptime of virtually 100 percent.