Hersh JalilMSC. Student

Renewable energyHydroelectric

Power

Hydroelectric power comes from flowing water … winter and spring runoff from mountain streams and clear lakes. Water, when it is falling by the force of gravity, can be used to turn turbines and generators that produce electricity

IntroductionIt is a form of energy … a renewable resource. Hydropower provides about 96 per cent of the renewable energy in the United States.

In the hydrologic cycle, atmospheric water reaches the earth is surface as precipitation. Water from rain and melting snow eventually reaches ponds, lakes, reservoirs, or oceans where evaporation is constantly occurring.

HOW HYDROPOWER WORKS 2 11

Water from the reservoir flows due to gravity to drive the turbine.

Turbine is connected to a generator.

Power generated is transmitted over power lines.

Hydro power is available by creating dams in stream and river flows. Hydro power generation is an established technology and maybe as much as one fifth of the world's electricity is generated this way, which is slightly more than by nuclear generation.

Hydroelectric dam in cross section

In electricity generation, an electrical generator is a device that converts mechanical energy to electrical energy, generally using electromagnetic induction. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy.

Pumped Storage

At night when customer demand for energy is lower, water is pumped to storage pool above the dam

At Day

When demand and heavy load is placed on the system is allowed to flow back through the turbine – generator

ADVANTAGES

1. Once a dam is constructed, electricity can be produced at a constant rate.

2 - Economics The major advantage of hydroelectricity is elimination of the cost of fuel. The cost of operating a hydroelectric plant is nearly immune to increases in the cost of fossil fuels.

3. If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when electricity demand is high.

4. When in use, electricity produced by dam systems do not produce green house gases.

They do not pollute the atmosphere.

5. The lake's water can be used for irrigation purposes

Although dams prevent the natural flushing out of a river during a flood, they also control flooding downstream in times of high rainfall and snowmelt.

Disadvantages

Usually a large area of land has to be flooded to ensure a continuous flow of water to the turbine. In some cases when a dam is built, large populations have to be relocated. In China, the Three Gorges Dam Project on the Yangtze River will displace more than 1 million people.

. Dams are extremely expensive to build and must be built to a very high standard.

Disadvantages

Hydroelectric projects can be disruptive to surrounding aquatic ecosystems. For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed.

Environmental damage

Population relocation

Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In many cases, no amount of compensation can replace ancestral and cultural attachments to places that have spiritual value to the displaced population. Such problems have arisen at the Three Gorges Dam project in China.

Dam failures Failures of large dams,

while rare, are potentially serious — the Banqiao Dam failure in Southern China resulted in the deaths of 171,000 people and left millions homeless. Dams may be subject to enemy bombardment during wartime, sabotage and terrorism. Smaller dams and micro hydro facilities are less vulnerable to these threats.

The end