Back to Basics: Direct Hydropower
In a modern hydropower installation, a water turbine converts the energy in the moving water into rotational energy at its shaft, which is then converted into electrical energy by the generator that is coupled to the turbine. Next, the electrical energy is converted back into rotational energy by the electric motor of the machine that is being powered. Every energy conversion introduces energy loss.
In an old fashioned hydropower installation, there was only one conversion of energy; A water wheel converted the energy inherent to the water source into rotational energy at its shaft. The same shaft also moved the machinery, so that the only source of significant energy loss occurred in the water wheel itself.
Some small direct hydro powered systems in South America present a strong case for combining the use of modern materials with old fashioned methods of water power mechanization. The higher efficiency of this approach means that less water is needed to produce a given amount of energy. This lowers the cost of hydropower and enables power to be produced by the use of very small streams.