as long as it rains, and water is stored at a higher elevation than the turbine or impeller shaft of a machine. The power is stored as potential energy and is converted to kinetic energy by the power generating station. This station may convert this potential energy into electricity, in the case of a electrical generator, or the power can be used to directly power a shaft that will run machinery.

In current power plants, the same as coal or gas, the heat is used to boil water inside of a 'pressure vessel'. The steam from the boiling water passes through a turbine, which causes a shaft to rotate. The shaft is also connected to a generator which generates the electricity.

Axle shaft, steering shaft, drive shaft, distributor shaft

A regular shaft has regular flex.