In order to produce electricity by means of generators, we must provide a method of propulsion. This can be achieved in one of the following ways:
1. water power, or 2. steam power.
Where a natural and continuous flow of water is available (i.e. waterfalls or fastflowing rivers), its potential energy can be used to turn a waterwheel coupled to a generator. This method is obviously inexpensive due to the fact that no cost is involved in providing the propulsion. However, in the United Kingdom the number of sites available for such generation on any useful scale is limited, and such sites are usually to be found in mountainous areas such as Scotland and Wales.