Hydroelectricity refers to the generation of electrical power by the use of hydropower. Hydropower here mainly is the gravitational force of falling water. This does not use any water in energy production. In the previous article on the Thermal power plants, you learnt that steam was causing the movement in the turbines. Here the flow of the water from a height causes the rotation in the turbines, but more on that later. Coming back to hydroelectricity, it is the most widely used form of renewable energy accounting for 3% of the world’s total energy consumption. The cost of hydroelectricity is relatively low, giving it a competitive edge as a source of energy. The average cost of electricity for a large hydropower plant is very less. Energy production is dependent on the amount of water that is let out since this can be controlled, hydropower plants have the advantage of being flexible. The output can be controlled as required by the need.
Hydro Power Plant
Hydroelectricity is produced by utilizing the gravitational force of falling water. To this end, the hydropower plant requires a dam. This dam is placed on a source of water, preferably a river. The dam is a massive wall that blocks the flow of the river, therefore, a lot of water collects behind the dam. Near the bottom of the dam, there is an intake from which the water is let into the dam. This intake leads to a drop through the penstock inside the dam. The device used to obtain energy from the falling water here is a turbine. Thermal power plants also use turbines but there are some major differences between the steam turbines and hydro turbines. The turbine is connected by a shaft to the generator. When the water rotates the turbine, electrical energy is generated.
Hydropower plants also have a facility of pumped storage wherein water is kept as a reserve for periods of peak power demand. This is the hydroelectric equivalent of recharging your battery. When the power demand is low, say in the middle of the night, the dam uses a pump to pump the water back up to the reservoir behind it. This water is then used during times of peak power demands.
The production capacity of a dam is dependent on the water supply available. Once constructed, a hydropower plant will be operational for decades and provided its water sources don’t run out, it can produce electricity at a constant rate. As mentioned earlier, the output can be easily controlled. The reservoir that forms behind the dam can be used for irrigation or for leisure purposes. Also, once the construction is completed, there is a negligible amount of greenhouse gas emission.
Dams also have a couple of problems, though. Dams are very expensive to build and to last decades, they must be built to a high standard. Also in the case of dam breaches, the runaway water will cause significant flooding in the downstream regions. Also, the creation of a reservoir causes a massive tract of land to get submerged. This area is lost and people living in such areas are displaced. Sometimes they are compensated, sometimes not. This creates a lot of tension between the construction and the affected people. Also, the construction of a dam blocks the natural flow of water and severely reduces the flow downstream. Such situations can cause disputes between neighbouring countries and even neighbouring states such as Karnataka and Tamil Nadu.