In 2015, electricity generation in the US was about 4 trillion kilowatts. The share of the energy sources were: Coal = 33%, Natural gas = 33%, Nuclear = 20%, Hydropower = 6%, Renewable sources (wind, solar, biomass, geothermal) = 7% and petroleum = 1%. Fossil fuel (coal, natural gas, and petroleum) contributes two-thirds of electricity generated in the US (AFDC, 2016).
The sources of mechanical energy used in the generation of electricity are:
|Source of mechanical energy||Prime mover|
|Coal||Pulverized coal is used in a steam boiler to heat water to produce high-pressure steam that turns a steam turbine||The steam turbine then turns an electrical AC generator coupled to it that generates electricity|
|Natural Gas||Natural gas is used in a steam boiler to heat water and produces high-pressure steam that turns a steam turbine||The steam turbine then turns an electrical AC generator that produces electricity|
|Nuclear||Uranium fission takes place in an enclosed steam boiler to heat water and produces high-pressure steam that turns a steam turbine||The steam turbine then turns an electrical AC generator that produces electricity|
|Hydropower||Water from a dam at an altitude travels downstream with a high kinetic energy and is directed to a hydraulic turbine which turns it at a high speed||The hydraulic turbine then turns a hydroelectric generator that produces electricity|
|Renewable Source (wind)||The strong wind that has kinetic energy is used to turn a wind turbine||The wind turbine then turns an electrical AC generator that produces electricity|
|Petroleum (Diesel)||Diesel is used to run a diesel engine which turns an electrical AC generator||The turning of the electrical generator produces electricity|
The electric generators produce an alternating current when they turn at high speed. The alternating current is produced when the armature of the generator rotates in a magnetic field thus making it keep on changing its polarity by cutting through the field. That change generates an electric charge that keeps on changing the direction thus forming a sinusoidal waveform courtesy of the slip rings on the stator end-point (Wood & Wollenberg, 2012). The AC power can be single or three phase depending on the stator coils which are normally at 120o to each other for three phase.
Power transmission in the US is in four major interconnections. These are the western, eastern, ERCOT grid and the Quebec interconnections. Power transmission is done at high voltage (115KV and above) to reduce the energy losses that occur over long distances (AFDC, 2016). The power is usually three phase, and the transmission is dominantly overhead although few instances of underground transmission can be done in sensitive locations that do not warrant overhead transmission.
Power for domestic use is stepped down using a transformer that reduces the high voltage to a low voltage value of 120V and 60Hz that is recommended for domestic use for single phase supply. The power enters the homes in insulated cables to a power meter where the distribution to the other sections of the house or home can be done with ease from a consumer unit (Wood & Wollenberg, 2012).
The division of the power within the home is done in three major ways. The lighting gets its supply from a consumer unit which has its circuit breaker rating. The sockets have their supply too with a circuit breaker of a higher rating than the lighting and the supply to heavy consumers like the heating appliances or cookers that have their circuit breaker also from the consumer unit. The rating of this circuit breaker is usually the highest. All the power supply to all sections of the home must pass through a regulation point that protects the home using circuit breakers in the consumer unit that trips in case of high demand beyond the allowable rating (Wood & Wollenberg, 2012).
In conclusion, power generation in the US is facing challenges that require the activity to embrace low-emitting energy-generation technologies that will reduce greenhouse gas emissions that have a great impact on the global climate.
- AFDC. (2016). Energy production and distribution. Retrieved June 29, 2016, from http://www.afdc.energy.gov/fuels/electricity_production.html
- Wood, A. J., & Wollenberg, B. F. (2012). Power generation, operation, and control. John Wiley & Sons.