This is a cross-flow turbine, essentially a water wheel turned by naturally flowing water to produce energy. Unlike a dam, or a mill wheel this is very small, more used in smaller streams and such. This provides energy without the cost of fuel and the only time and energy used to work on it is set up and very occasional maintenance. This is used in developing areas around the world because it's much cheaper and less time consuming. This design takes it to the next level where the material costs of the wheel itself are significantly reduced using 3D-printing.