Hydroelectric power generation is one of the oldest ways of generating electricity and accounts for 16 percent of world’s electricity generation. Although age old, it is one of the renewable sources of energy. The projects are constructed across rivers or large water bodies that induce flow of water at very high speeds producing gusts of water. This motion of water is tamed to generate electricity. Since these projects depend on flowing water, lack of the same could turn them useless. The major threat to these projects is the changing weather patterns and other phenomena associated with global warming. Nevertheless there are a lot hydroelectric power projects running in several countries along with a good number of them under construction. Lets discuss the physics behind hydroelectric power generation.
Electricity generation from any source can be boiled down to law of conservation of energy; As mentioned during our A Level Physics tuition class, energy can only be converted from one form to another but cannot be destroyed. Hydroelectricity is, typically, generated through a process in which potential energy is converted into kinetic energy and eventually into electricity. In a reservoir water is stored and is let out through a dam. Since large amounts of water is obstructed and allowed to move through a small channel the water moves at rapid speeds and this moving water can be used to run the turbines, just like it is in the case of wind energy described in the previous articles, which leads to the generation of electricity. Alternatively the water that is stored in the reservoir falls down onto the turbines where potential energy of water initially gets converted into kinetic energy and eventually runs the turbines.
Hydroelectricity need not be generated from reservoirs or other stagnant sources of water alone. The kinetic energy of moving water in a river can also be used to generate electricity. When turbines are placed across a river the water hitting these turbines rotates them and cause the generation of electricity. This can be done in decentralised, small-scale fashion. In fact, if you are curious enough, you can construct a turbine, attach it to a dynamo, connect it to a light bulb and put it a moving water body. This should generate electricity and the light bulb glows.
Renewable nature of hydroelectricity puts it on the plus side but it comes with some drawbacks. Due to the large scale nature of these projects and the amount of geographical area they occupy, acquiring land and other bureaucratic procedures involved in the process make it a time-costly project. The large amounts of area that undergoes submersion, which is generally on riverside, due to the reservoir construction affects wildlife and at times the tribes living there. Nevertheless, a whopping 3400 terawatt-hours of hydroelectric power is generated globally (in the year 2010) and that sums the importance of hydroelectric power.