The demand for electricity varies at different times of a year. One big disadvantage is that the wind, waves and tides do not occur at all time and hence cannot guarantee steady production of electricity. Hydroelectric power stations can solve this problem. When the demand is low, excess power generated from other stations can be used to pump water back up into the high reservoir.
When there is a demand some of the water can be released to generate electricity. This is called a 'pumped storage scheme'.
Hydroelectric Power Station
It is a renewable source of energy and free of pollution, less expensive, long lasting and easy to maintain.
Large dams must be built to hold the water before it flows to the turbine. This causes ecological imbalance. At times small pieces of earth get trapped at the bottom of still water in the reservoir. As these deposits build up the capacity of the reservoir reduces.
