Electricity generation By different Prime Mover/ By different Source of Energy, Emgineer Mir Akter Hossain, Toronto
Electricity generating industry or Electrical power station is a key industry among all the industries as the operation of all other industries depends on the operation of power station but operation of power station does not depend on the operation or function of other industries. So a power station can be compared with the heart of human being as all the organs of human body depends on proper function of heart. & when heart stop functioning then human being collapse . Similarly if a power station faces shut down then all other industries will also follow shut down. Electricity can be generated from heat accumulated in the form of chemical energy in petroleum (Coal, Oil, natural Gas ) by millions of years of transformation of bodies of animal, plants under ocean, Earth crust etc. Electricity may also be generated from energy stored in the form of gravity from natural water reservoir located at very high height of mountain, or erecting dam in the flow of river in hilly area & finally by passing it through hydraulic turbine which is coupled with an alternator . It may also be generated by converting nuclear energy stored in the nucleus of atom to heat energy, then by this heat energy steam is produced, then steam is used to drive steam turbine coupled with an alternator to transform mechanical to electrical energy. Sometimes diesel is used as fuel to drive engine which finally convert heat energy accumulated in the form of chemical energy stored in diesel oil to electrical energy. Natural gas may be compressed by a compressor , then mechanical energy stored in gas is converted to velocity energy by passing it through nozzles & this high velocity of gas is absorbed by blades of gas turbine which is coupled with alternator to produce electricity .
For uninterrupted power supply there should be a common or national grid circuit where multiple power plants should be connected instead of one power station only & different type of power stations should be connected to national grid circuit. To have uninterrupted, stable & low cost power supply, the national grid should have connection with steam turbine power plant, gas turbine power plant, hydraulic turbine power plant, Nuclear power plant etc.
Electrical load on alternator sometimes varies daily , sometimes seasonal change happen (In summer, winter ) , sometimes a sudden change or step change of load appears due to total shutdown of a power plant during transient , steady state fault developed in electrical circuit, lightning discharge etc. A gas turbine may pick up the load in this situation as it can start very quickly (May be even in few minutes ) & stop quickly. A Gas Turbine Power Plant should be installed in the immediate neighbourhood of gas field or at a very short distance from gas field to get continuous supply of natural gas which imposes limitation of its use as prime mover. A steam turbine power plant which uses coal as fuel takes several hours to start & take full load . Also coal is cheaper than gas, which makes a steam turbine power plant as base load power plant & gas turbine power plant as peak load power plant. But steam condenser which is used for Steam Turbine needs enormous & continuous supply of cooling water from free flow of river under open atmosphere that prevents to use Steam Turbine as prime mover , as river is not available in many situations.
A hydraulic turbine driven alternator can take load very quickly even in few minutes but its generation capacity depends on height of water column in natural water reservoir which varies according to rate of rain fall, rate of melting of ice on the top of mountain due to daily & seasonal variation of temperature etc. But its greatest advantage is the no fuel cost at all.
In case of nuclear power plant, nuclear energy is converted to heat energy, then steam is produced in boiler by this heat energy & produced steam is used to drive steam turbine coupled with alternator to generate electricity. In this situation cost of electricity production / Kwh is very low but recovery of construction cost is much more expensive . One of the main disadvantage is the difficulty in the management of nuclear waste . It takes many years to eliminate radio activity & risk . Also there is possibility of accident in nuclear reactor which can kill several thousand people in very short time . Health hazard may appear for human being even for several decades from radio activity of disposed material & after any accident that may occur in nuclear reactor.
Comparison of Pollution by burning Gas, Oil ,Coal to produce electricity
Emission of CO₂, , is maximum by burning coal , it is more than the emission of above gases by burning Natural gas & oil. Emission of CO₂, ,is minimum by burning of natural gas. Emission of CO₂, ,by burning oil is in between the waste products ejected by burning of natural gas & coal, which means pollution by burning coal is maximum, pollution by burning of natural gas is in minimum & pollution by burning oil is medium.
Comparison of cost by using Gas, Oil or Coal as fuel to generate electricity.
There is no fuel cost for generating electricity from hydro power station, wind power etc. Fuel cost is lowest to produce electricity from Nuclear Power station. Next higher price for fuel is coal fired station. Fuel price is higher for natural gas fired station than the price of fuel for coal fired station. Oil fired station is more expensive than the natural gas fired station related to cost of fuel.
Comparison of cost related to construction of different type of power stations.
The construction cost is lowest to erect natural gas fired station. Next higher price for construction is coal fired station. Hydro& Nuclear power station is most expensive related to construction cost of power plants among all the power stations.
Calorific value of different fuels by KJ/KG
Coal 15 000 – 27 000 , Natural Gas 43 000 ,Diesel 44 800, Petroleum 43 000 , Gasoline 47 300
Largest Coal Fired station of World is 6720 MW in China, Largest Oil fired station 5600 MW in Saudi Arabia, Largest Natural Gas Fired Station 5597 MW in Russia, Largest Nuclear Power Station 7965 MW in Japan, Largest Hydro Station 22 500 MW in China.
Electricity generation Capacity by MW of different country :
China 16 46000, USA 10 74000, E. Union 9 75000, Japan 3 22200, India 3 08800 ,Russia 2 63500 , Germany 2 04100, Brazil 1 50300 ,
Canada 1 47600, France 1 29300 ,Italy 1 17000, Spain 1 06700, UK 94600, S. Arabia 69 050, Australia 67 030,, Mexico 65 450, Indonesia 54 580, Vietnam 45 410, Thailand 39 670, Bangladesh 11 840
Largest single Generator capacity is 2000 MW which is manufactured by Siemens for Finland.
Among top 20 largest Power Stations of the World 12 are Hydro Power Stations. Among 12 hydro stations , 6 hydro stations are in China.
Hydro power generation capacity by country in Terawatt (2017) : China 1194.5,Canada 403.35, Brazil 401.06, USA 322.39, Russia 178.9, Norway 143, India 135.54, Japan 92.55, Venezuela 72.09, Paraguay 59.29
Price of electricity in U. S $ /Kwh by Region/Country
Burma has got lowest electricity price , which is 0.04, followed by S. Arabia 0.05,Bangladesh 0.06,Russia 0.06, Pakistan 0.07, Vietnam 0.07 ,Sri Lanka 0.08, China 0.08, India 0.08, Canada 0.10, USA 0.13,France 0.18,UK 0.21, Spain 0.25 ,Australia 0.26, Japan 0.26, Germany 0.33, Denmark 0.34