Hydropower, or hydroelectric power is a form of renewable energy that uses the power of moving water to generate electricity.

• The LARGEST source of renewable energy in the world

Approximately 71% of all of the renewable electricity generated is from hydropower.

• How it works:

To harness energy from flowing water, the water must be controlled. A large reservoir is created, usually by damming a river. A gate or valve controls how much water flows out of the reservoir. Engineers control the amount of water let through the dam. The process used to control this flow of water is called the intake system.

Water gains potential energy just before it spills over the top of a dam or flows down a hill. The potential energy is converted into kinetic energy as water flows downhill. Water is channelled through tunnels in the dam. The energy of water flowing through the dam’s tunnels causes turbines to turn. The turbines make generators move and generators produce electricity.  The water can be used to turn the blades of a turbine to generate electricity, which is distributed to the power plant’s customers.

When a lot of energy is needed, most of the tunnels to the turbines are open, and millions of litres of water flow through them. When less energy is needed, engineers slow down the intake system by closing some of the tunnels.

• One of the OLDEST power sources in the world

It generatespower when flowing water spins a wheel or turbine and was used by farmers as far back as ancient Greece for mechanical tasks like grinding grain. Egyptians used Archimedes water screws for irrigation during the third century B.C. The evolution of the modern hydropower turbine began in the mid-1700s when a French hydraulic and military engineer, Bernard Forest de Bélidor, wrote the Architecture Hydraulique.

• Types of hydroelectric plants
  • Impoundment facility: A dam is used to control the flow of water stored in a pool or reservoir. When more energy is needed, water is released from the dam. Once water is released, gravity takes over and the water flows downward through a turbine. As the blades of the turbine spin, a generator is powered.
  • Diversion facility: Does not use a dam, instead, it uses a series of canals to channel flowing river water toward the generator-powering turbines.
  • Pumped storage facility: The plant stores energy by pumping water uphill from a pool at a lower elevation to a reservoir located at a higher elevation. When there is high demand for electricity, water located in the higher pool is released. As this water flows back down to the lower reservoir, it turns a turbine to generate more electricity.

CHINA is the largest producer of hydropower

Where else is hydropower used?

• LARGEST  hydroelectric power plant in the world

The Three Gorges Dam in China is the largest hydroelectric dam in the world in terms of electricity production. The dam is 2 335 meters long and 185 meters tall, and has enough generators to produce 22 500 megawatts of power.

• Hydropower has among the BEST CONVERSION EFFICIENCIES of all known energy sources (about 90% efficiency, water to wire)

• Lesotho Highlands Water Project

The Lesotho Highlands Water Project (LHWP) is an ongoing water supply project with a hydropower component, developed in partnership between the governments of Lesotho and South Africa. It comprises a system of several large dams and tunnels throughout Lesotho and delivers water to the Vaal River System in South Africa.

• All shapes and sizes

While there is no internationally agreed upon definition for the different sizes of hydro-power, a generic distinction between ‘large’ and ‘micro’ hydro-power is that micro hydro-power usually refers to installations up to 10 MW of installed capacity. Micro hydropower could play a pivotable role in remote areas to provide access to electricity in stand-alone isolated mini-grids or as distributed generation in national grids. A good example is the gold mines at Pilgrims’ Rest that were powered by two 6 kW hydro turbines – as early as 1892. A 45 kW turbine was added two years later to support those turbines to power the first electrical railway in 1894.