Water Energy

Non-renewable resources are natural resources that exist in fixed amounts and can be used up. Examples include fossil fuels such as oil, coal, and natural gas. These fuels formed from the remains of plants over hundreds of millions of years. We are using them up far faster than they could ever be replaced. At current rates of use, oil will be used up in just a few decades and coal in less than 300 years. Continued reliance on fossil fuels as a source of energy is not sustainable. Burning fossil fuels to generate energy also has a huge environmental impact and is a major contributor to global warming. 

Renewable resources can be replenished by natural processes as quickly as humans use them. Examples include sunlight and wind. They are in no danger of being used up.

 Water Energy

Hydroelectric energy is a form of energy that harnesses the power of water in motion, such as water flowing over a waterfall, to generate electricity. 

Hydropower (hydroelectric) relies on water to spin turbines and create electricity. It is considered a clean and renewable source of energy because it does not directly produce pollutants and because the source of power is regenerated. 

Most types of hydroelectric power plants have a reservoir of water, a gate or valve to control how much water flows out of the reservoir, and an outlet or place where the water ends up after flowing downward. 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. The water can be used to turn the blades of a turbine to generate electricity, which is distributed to the power plant’s customers.

There are three different types of hydroelectric energy plants, the most common being an impoundment facility. In an 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, they power a generator.

Figure 2: The typical layout of a hydroelectric power plant and its basic components.

Dam and Reservoir: The dam is constructed on a large river in hilly areas to ensure sufficient water storage at height. The dam forms a large reservoir behind it. The height of water level in the reservoir determines how much of potential energy is stored in it.

Control Gate: Water from the reservoir is allowed to flow through the penstock to the turbine. The amount of water which is to be released in the penstock can be controlled by a control gate. When the control gate is fully opened, maximum amount of water is released through the penstock.

Penstock: A penstock is a huge steel pipe which carries water from the reservoir to the turbine. Potential energy of the water is converted into kinetic energy as it flows down through the penstock due to gravity.

Water Turbine: Water from the penstock is taken into the water turbine. The turbine is connected to an electric generator. Kinetic energy of the water drives the turbine and consequently the generator gets driven. 

Generator: A generator is mounted in the powerhouse, and it is connected to the turbine shaft. When the turbine blades are rotated, it drives the generator and electricity is generated.

Another type of plant is called a pumped-storage facility. This plant collects the energy produced from solar, wind, and nuclear power and stores it for future use. 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.

Hydroelectric energy is the most commonly used renewable source of electricity. China is the largest producer of hydroelectricity. Other top producers of hydropower around the world include the United States, Brazil, Canada, India, and Russia. Approximately 71% of all the renewable electricity generated on Earth is from hydropower.

The Three Gorges Dam in China, which holds back the Yangtze River, 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.

Hydroelectric energy is fairly inexpensive to harness. 

Rivers flow all over the world, so the energy source is available to millions of people. Hydroelectric energy is also reliable. Engineers control the flow of water through the dam, so the flow does not depend on the weather unless there is a long drought. 

However, hydroelectric power plants are damaging to the environment. 

• When a river is dammed, it creates a large lake behind the dam. This lake drowns the original river habitat underwater. Sometimes, people build dams that can drown entire towns underwater so people must move to a new area.  
• It alters the natural movements of nature: Although modern technology allows for hydroelectric plants to accommodate wildlife movement as best as possible, using salmon runs or alternative migration paths, it isn’t a perfect system. The filling of a reservoir destroys the habitats of certain animal species as well, no matter how careful the construction efforts might be.
• Hydroelectric power plants don’t work for a very long time: Some can only supply power for 20 or 30 years. Silt, or dirt from a riverbed, builds up behind the dam and slows the flow of water.