Essay on the Hydroelectric Power Generation

Better known as water power, hydroelectric power is known to be one of the oldest methods of producing electrical energy. This is usually the power that is harnessed from the energy of fast running or falling water to produce both mechanical and electric power (EDF Energy, 2017). To generate this power, a hydroelectric power station that converts the kinetic energy of falling water into electrical energy is used. The power generated is usable for both large scale and small scale purposes. Thus, this essay seeks to give an overview of the generation of hydroelectric power.

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In a hydroelectric station, power generation begins way before it could reach its consumers. Firstly, water is stored in large dams referred to as reservoirs, usually on an elevated ground. Since the water stored in these reservoirs contains potential energy, it is converted into kinetic energy, when it begins to flow from through a vertically elevated penstock, from the dam. As the water gradually flows, the initial potential energy that it possessed is converted into kinetic energy which is used to turn a hydraulic turbine. (Gessford, 1979). The falling water then strikes a series of blades that are attached to a shaft causing the turbine to spin which in turn, converts the kinetic energy of the falling water into mechanical energy. Many at times the scientific ideology behind the turning of a turbine is likened to that of a windmill, only that power on the turbine is provided by falling water and not wind.

Connected to the turbine through shafts and possibly gears, is a generator which spins alongside the spinning turbine. Since the energy produced by the falling water on the turbines is usually mechanical energy, the generator which serves as a transducer converts this mechanical energy from the turbines into electrical energy. The generator's operations are similar to that of any other generator in a power transmission plant. These operations are based on the principles that were discovered by Faraday. Faraday, an ancient scientist, found out that electric energy is caused to flow when a magnet is moved past a conductor. Thus in these large hydroelectric power generation generators, electromagnets are made by circulating direct current through wired loops that are formed around stacks of magnetic steel laminations which form field poles. The field poles around a rotor, which is attached to the shafts of the hydraulic turbine hence making it rotate at a fixed speed.

The spinning of the hydraulic turbine causes the rotor to turn causing the field poles, formed around the electromagnets, to move past electric conductors that are usually mounted in the stator. This process, therefore, causes the flow of electricity, and hence a voltage is developed at the generator output terminals. Normally, the type of voltage that is produced by the generators is usually low. Therefore, for the power transmission lines to carry this generated power over long distances and to reach different consumers, a step-up transformer, which converts the low generator voltage into increased higher transmission voltage is used (Grigsby, 2013).

From the generation plant, power is transmitted to various users through grid high-voltage transmission lines, which are usually supported by tall metal towers. These transmission lines are specially modified to carry high voltage electricity over long distances and into power terminal stations that control the flow of power on grid transmission lines by reducing the grid voltage into sub-transmission voltages (Kaltschmitt et al., 2000). At the transmission voltage, electricity is sold to users who operate their own transmission substations. However, many consumers prefer that the energy from the transmission substations is stepped down using transformers to lower but required voltages that are readily usable.

Scenario

The amount of hydroelectric power generated at a hydropower plant depends on two crucial factors;

The distance the water falls- The distance covered by the falling water directly affects the amount of power generated. This happens in the sense that, the farther the water falls, the more the power it produces. However, this distance is determined by the size of the reservoir dam that stores the water (Noyes, 1980). The higher the dam elevation, the further the water falls and the more kinetic power it has. Thus, in a nutshell, the power of the falling water is directly proportional to the distance it falls.

The amount of water falling- the volume of water falling through the turbine determines the power generated. In this case, the amount of falling water depends on the river flow, or the water flowing down the river. A plant that has a lot of falling water onto the turbine has the potential to generate more power (Tagare, 2011). Thus, in this regard, the power generated is said to be directly proportional to the river flow, or the water volumes.

Thus, based on these two determining factors, a formula that calculates the power that can potentially be generated by a dam is devised.

Hydropower = (Height of the dam) x (River Flow) x (Efficiency)/ 11.8

In this case:

Hydropower is the electric power in kilowatts

Height of the dam is the distance the water falls (measured in feet)

River Flow represents the water amounts flowing into the river and is measured in cubic feet per second.

Efficiency- this is how well the kinetic and mechanical energy of the falling water and that of the hydraulic turbines is converted into electric power, by the generator.

11.8- This is a constant that converts the units of Watts into seconds into Kilowatts.

References

EDF Energy. (2017). Hydro-electricity | EDF Energy. Retrieved from https://www.edfenergy.com/future-energy/energy-mix/hydro

Gessford, J. E. (1979). The use of reservoir water for hydroelectric power generation. New York: Arno Press.

Grigsby, L. L. (2013). Electric power generation, transmission, and distribution. Boca Raton, FL: CRC Press.

Kaltschmitt, M., Streicher, W., & Wiese, A. (2000). Hydroelectric Power Generation. Renewable Energy, 349-383. doi:10.1007/3-540-70949-5_8

Noyes, R. (1980). Small and micro hydroelectric power plants: Technology and feasibility. Park Ridge, NJ: Noyes Data Corp.

Tagare, D. M. (2011). Hydroelectric Generation-Pumped Storage, Minor Hydroelectric, and Oceanic-Based Systems. Electric Power Generation, 45-68. doi:10.1002/9780470872659.ch3