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ELECTRIC POWER

 

Introduction

Electrical power or electricity is generated in power stations and transmitted to areas that need electricity through a grid. Many households, industries and businesses need electricity in order to operate appliances, equipment and machinery and to provide lighting, air-conditioning and heating. The electrical power industry is commonly split up into Generation, Transmission and Distribution.

 

Generation

An electric power station uses a turbine, engine, water wheel, or other similar machine to drive an electric generator that converts Mechanical Nuclear Wind Solar Tidal Wave or Chemical energy to generate electricity. Steam turbines, internal-combustion engines, gas combustion turbines, water turbines, and wind turbines are the most common methods to generate electricity Wind. Biomass, Tidal & Wave Energy, Solar, H2 Energy, and Fuel cells are the preferred new renewable energy Producers for the future.
Generally Alternating Current (AC) generation is used in Power plants.

 

Transmission

Electricity produced by generators first goes to a transformer at the power plant that boosts the Voltage(V) to different Higher voltages up to 400,000 volts. When electricity has to travels long distances it is better to have it at higher voltages as Current(I) required becomes smaller and hence the line losses (I*I*R where R is the resistance of the Transmission line) are lower. Another way of saying this is that electricity can be transported more efficiently at high voltages. The long thick cables of transmission lines are made of copper or aluminium because they have a low resistance and latter is cheaper. High voltage transmission lines carry electricity long distances to a substation. Here transformers change the very high voltage electricity back into lower voltage electricity. (33kv and 11kv) Both overhead lines and underground cables are used for long distance transmission Direct Current Transmission is used in very special; cases to Link two different systems.

Transmission lines can be classified as:
Extra High Voltage
         used for long distance, very high power transmission e.g. 50 kV, 440 kV (India)
High Voltage
         used for medium distance, high power transmission e.g. 220 kV, 132 kV, 33 kV
132 kV is used to transmit about 50 MW to a maximum distance of 100 km
33 kV is used to transmit about 5 MW to a maximum distance of 40 km

 

Distribution

From these substations electricity in different power and voltage levels is used to run factories, serve commercial institutions, light street lamps and sent to your neighbourhood.
In your neighbourhood, another small transformer some time mounted on pole converts the power to even lower levels (400/230 volts) to be used in your house for house hold appliances.
3-phase electricity is a common method of electric power transmission/distribution as it has properties that make it very desirable in distribution. The most important class of three-phase load is the electric motor. A three phase induction motor has a simple design, inherently high starting torque, and high efficiency.
High loads that do not require the revolving magnetic field characteristic of three-phase motors are also connected to three-phase systems not to over load the distribution system, especially in developing countries.
Generally over-head lines are used for transmission. In developed countries underground cables are also used for distribution and 33kv/11kv transmission mostly in cities. In open countries over-head distribution is common. Recently insulated cables are introduced for distribution in Sri Lanka to prevent pilfering of electricity. Finally electricity enters your home through a meter.
Because of the high cost of transmission/distribution lines many remote and rural areas are not connected to electricity in developing countries.
Single wire earth return (SWER) is a single-wire transmission line for supplying single-phase electrical power (33kv/11kv) to remote areas at low cost. It is principally used in rural electrification. This is being extensively used in New Zealand and Australia since 1925. Since last 10 years it is being used in Africa and India. It was used to a small extent in Sri Lanka also.

 

Electricity Generation Types

Using fossil fuel (67% of total world production)
  Coal fired Power Generators
Gas fired Power Generators
Oil fired Power Generators
 
Nuclear Power Generators (12% of total world production)
Renewable Energy  
  Hydro Power Generators
Wind Power Generators
Bio Mass Power Generators
Solar Power
Geo Thermal Power Generators
Ocean wave & Tidal Power Generators
(19% of total world production)

(2% of total world production)

 

Fossil fuelled Power Stations

Fossil fuel remains the most popular source for power generation essentially due its cheapness, ease of availability and easy setting up of a power plant. Considering the time and infrastructure needed to set up fossil fuel power stations, easiest to hardest is oil, gas and coal.

 

Coal fired power

This is the most common form of power generation. This is currently the cheapest source of electricity. It costs approximately 0.04 US$/kWh to produce. Cheapness is the significant advantage. Its major objection is being the environmental issues. Despite the objection, coal fired power station has to be the leading source of power for most of the developing countries. If Coal is not available locally, it has to be imported. In that case it is economical to set up the power plant close to harbour to reduce the transport cost of coal from harbour to power station.

 

Gas fired power

This is recently gaining popularity as source of electricity. It costs approximately 0.06 US$/kWh to produce. These power stations are compact, clean and efficient. These power stations are technically simple and quicker to construct. Gas fired power station can be second leading source of power for developing countries. Many countries are discovering gas fields in ocean beds and river basins. In India gas fields were discovered in Godavari and Kaveri basins in the south. Many gas fired power stations were setup close to theses fields and currently utilising the gas from these fields. Supply and price of gas is steadier than oil in the world market. If gas is not available locally it can be easily imported. Handling and storage units have to be set up and this is expevsive.

 

Oil fired power

This is the common source of electricity in countries where demand is not high. It costs approximately 0.10 US$/kWh to produce. These power stations are technically simple and quicker to construct. Hence it is the common form of power generation in small developing countries. Its capacity can range from 1 to 300 MW. Further when the power stations were originally built oil was cheap. But it is still the best short term solution to solve the urgent surge of power need.

There are barge-mounted power stations, which can produce power even up 300 MW. At present there is a 60 MW barge mounted diesel generator anchored in Colombo harbour supplying power to Colombo. This supplies approximately 5% of the Sri Lanka’s total electricity demand. Barge mounted oil fired generators are ideal to meet unexpected electricity demand in short duration.

In India GMR Energy Limited, is supplying power to the grid from 220MW Barge Mounted power plant in Mangalore.

 

Nuclear Power stations

Even though Nuclear power constitutes 12% of the world power production, only a few developing countries like Brazil, China, India and Pakistan have the nuclear capability. Further their current production constitutes less than 2.5% of their total production. This is not a viable option in the developing countries in general.

 

Power from Renewable Energy

Hydro Power stations

Hydro Power stations are very popular in developing countries. After the initial capital expenditure the maintenance expense is minimal. It is very reliable in terms of operations. The hydro power potential if available should be fully exploited.

 

Other Renewable

Wind, Biomass, Solar, Geothermal, Waves and tides are the major forms of renewable energy. Despite its advantage on environmental issues, renewable energy it contributes only 2% of the world production. Three countries whose renewable energy component is greater than 2% is given below:

 

Denmark 23% (mainly wind power)
Germany 10% (mainly wind power)
Brazil 5% (mainly biomass power)

 

Wind power

It costs approximately 0.05 US$/kWh to produce in areas where the wind speed is greater than 3.5 m/s throughout the year. The cost increases if the required wind speed is not available throughout the year. In Kaniyakumari district in India wind farms are producing electricity. Countries with long coastlines should evaluate the potential of wind power. In order to make full use of this potential wind data has to be gathered for a period of minimum one year. India wind power generation capacity is nearly 6,000 MW. Denmark meets 20% of the electricity need through wind generation.

 

Biomass power

Biomass power generation is getting popular in developing countries because of the rising price of fuel. Most common method is to grow nitrogen rich plants and use their stem as fuel for gasifier and green foliage as fertiliser. These trees can be grown as inter crops with the coconut trees. The investment cost will less than that of solar energy. The land requirement will be greater than other methods of power generation. Participatory programme where villagers provide the fuel and in return they get electricity and an additional income works well in villages. Biomass does not pollute as it emits carbon dioxide, which was absorbed during the time of growth. It costs approximately 0.06 US$/kWh when done in small scale. The cost increases, as size of the project gets larger.

 

Solar power

Electricity is produced from solar power by two methods namely solar thermal energy and solar cells. Solar energy is available in many developing countries. The technology is still expensive. Because it is expensive, its usage is very much limited and mainly used in remote areas where other form of power is expensive. But recent development in Photovoltaic (Solar cell) technology has made it more competitive.

 

Solar power plant

Some solar power plant, use a highly curved mirror called a parabolic trough to focus the sunlight on a pipe running down a central point above the curve of the mirror. The pipe gets so hot that it can boil water into steam. That steam can then be used to turn a turbine to make electricity. It costs approximately 0.15US$/kWh to produce.

Ausra Inc., a developer of utility-scale solar thermal power, has a new system which uses flat mirror solar collectors focus the suns rays on tubes filled with water, directly producing steam to power steam turbine generators. Storage of heat from solar power plants can allow solar power plants to operate around the clock. Solar-thermal plants capable of storing 16 hours' worth of heat could provide power at prices competitive with coal and natural gas. Ausra claims that It can generate electricity for 10 cents/kWh now. One-square-mile land will be required to establish 175 MW solar thermal power plant.

 

Solar cells (Photovoltaic cells)

The electrical energy from solar cells can then be used directly. It can be used for lights and appliances. Solar energy can be stored in batteries to light a roadside billboard at night. Or the energy can be stored in a battery for an emergency roadside cellular telephone when no telephone wires are around. It costs approximately 0.30 US$/kWh to produce. Price is coming down.

 

Others

Geo Thermal Power, Ocean wave & Tidal Power makes minimal contribution to the power production.

 

 

 

 

 

 

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Wikipedia

Electricity
Electric Power
Electric Power Generation
Electric Power Transmission
Electric Power Distribution
Fossil-fuel power station
Nuclear Power
Hydro Electric Power
Wind Power
Biomass Power
Solar Power