Hydropower uses the power of moving water to generate electricity. It is currently the world’s largest source of renewable energy, contributing towards nearly 20% of global electricity.
WHY IS IT RENEWABLE?
Water is constantly moving in a cycle known as the Water Cycle. Evaporation (water turned into vapour) and condensation (when vapour cools into a liquid) are both processes that change water into different forms. These forms include solid, liquid and gas states and may be stored in clouds, oceans, rivers and even underground.
Whilst the water passes through the Cycle in lots of different forms and is stored in many places, it never actually leaves the Cycle. This means that water is renewable: we can use water as a source of energy for a very long time without any fear of using it up!
HOW DOES IT WORK?
Hydropower plants are buildings where electricity is generated using the energy of moving water.
These hydropower plants use a wall as a barrier to hold back water, known as a dam. The water that is held back creates what is known as a reservoir, which is similar to a lake but is made by human influences.
The water that is stored in the reservoirs is channelled through tunnels in the dam. Within these tunnels are turbines are spun by the water that passes through. Generators in the hydropower plant convert this movement of the turbines into energy that can be used in homes.
WHY AREN’T PLANTS BUILT ON OCEANS OR LAKES?
Hydropower requires a moving source of water. This is often found in areas where there is high to low elevation as well as gravity. These conditions provide greater energy potential. There is often less elevation in lakes and oceans which means less energy potential.
Some attempts have been made to use the energy of ocean waves and currents, although this work is still in its early days!