Electrical power at work can be seen everywhere you go. In your home, office, entertainment areas and so forth. How is electrical power generated?
This is the first of 8 lectures that will discuss how power stations are used to generate electrical power. After this brief introduction, we look at the 5 (five) different kinds of electric power generating stations.
This lesson is an Introduction to electrical power generation. By the end of this lesson, the student is expected to be comfortable with the following:
- Definition of electric energy
- Definition of Calorie
- Energy relationships
- Calorific values
- Different sources of energy
- Electrical energy generation arrangement
- Basic power station design considerations
- The ability of electricity to do work. We use electricity in our day to day activities such as lighting, heating, lifting, etc...
Joule: (J, SI unit of energy)
- Work done by a force of 1 Newton, to move (unit mass) of anything a distance of 1 meter along the direction of the force.
Calorie: (cal, SI unit of heat)
- The amount of heat (energy) needed to raise the temperature of 1 gram (g) of water by 1 degree Celsius.
- The amount of heat (energy) needed to raise the temperature of 1 kilogram (kg) of water by 1 degree Celsius. 1 kcal = 1,000 cal = 4.184 kJ
- Material that can be burned to release energy (further reading on wikipedia).
Calorific value of fuels:
- Estimated amount of heat available from fuel.
These definitions are important as they will be used from time to time in this course. The student is encouraged to commit these to memory.
Energy is defined as the ability to do work. We can simplify the forms in which we encounter energy in our daily life into three forms as follows:
1 Mechanical energy (Measured in N.m → Newton-meter = Joule):
- Ability to move things.
2 Thermal energy (Measured in Cal or KCal → Calorie or Kilocalorie):
- Ability to heat things.
3 Electrical energy (Measured in Watt.sec → Watt-second):
- Ability to use electricity to do work.
All the above forms of energy are interchangable since they can be used to do work and thus can be expressed using the same unit of measurement. The Joule!. The following table summarizes the relationship among energy units
|Energy form Comparison||Unit||Calorie equivelence||Joule equivelence|
|Heat→Mech||.||1 calorie||4.18 Joules|
|Heat→Mech||1 C.H.U||453.6 calories||1896 Joules|
|Heat→Mech||1 B.TH.U||252 calorie||1053 Joules|
|Elec→Mech||1 Watt.sec||0.24 calories||1 Joule|
|Elec→Mech||1 Kwh||860 KCal||Joules|
Calorific value of fuels
The following list of external sites shows a comparison of various types of common fuels and their calorific value:
Comparison of Solid fuels v/s Liquid fuels
|Solid Fuels||Liquid Fuels|
|Minimal odours||unpleasant odours|
|Requires simple burners||requires sophisticated burners|
|No climate constraints||Cold climates need regulation|
The following table shows a comparison of the five most prominent sources of energy and how they measure up against each other.
|Particulars||solar power||Wind power||Hydro power||Fuel power||Nuclear power|
|Reserves||Day time only||permanent||permanent||limited||abundant|
It must be noted that besides the above energy sources there are some other less used energy sources as follows:
- Geothermal energy
- Tidal energy
- Wave energy
For electrical energy to be succesfully generated we need an efficient arrangement of the following parts or system.
1. Prime mover:
- The part of the electrical generating sytem responsible in converting other forms of energy into rotating mechanical energy. eg a steam turbine converts heat energy into mechanical energy.
- The part of the electrical generating sytem responsible for converting mechanical energy into electrical energy.
These working together in a closed system are called prime mover - alternator combination.
Electrical energy is the most used form of energy everywhere. As seen in part 3, electrical energy is a result of conversion from other forms of energy that are abundant in nature. Those other forms of energy are usually generated and utilised at will.
Unfortunately, bulk storage of electrical energy for a long duration is not possible yet. This is the fundamental problem in electrical energy generation.
Electrical energy must be generated and transmitted to the point of consumption at the instant of demand.
this instant is usually less than a second.
Electric power generating stations are used to provide bulk electric power economically. To achieve this goal careful consideration must be given to the following points when designing a power station:
- Selection and placement of power generating equipment for maximum return from minimal expenditure for the working life of the station.
- The plant designed must provide cheap; reliable and continous service.
When the above objectives are achieved by a power station design, good and reliable service can be guaranteed to the consumers by the utility company involved. ll