Coal

State Coal Mine, Wonthaggi - From avlxyz on Flickr. Click the image to view a larger version of it (2048 x 1536).

Coal is a combustible rock which is extracted from the earth and is often burned in furnaces to produce heat to heat water, cook, and generate electricity.

  1. Coal Power Plants
  2. Classification of Coal Power Plants
  3. Efficiency of Coal Power Plants
  4. Energy Content of Coal
  5. Economic Characteristics of Coal
  6. Sustainability of Coal
  7. Income of Miners
  8. Environmental Impact and Safety of Coal As An Energy Source
  9. Human Cost of Coal
  10. Can Coal Be Clean?
  11. Carbon Capture and Storage
  12. Lifespan of Coal Power Plants
  13. Mountaintop Removal Mining (MTR)
  14. Longwall Mining

Coal Power Plants

Coal is widely used to generate electricity via the following process:

Coal, being a combustible rock, is burnt, the heat from the combustion of the coal is used to power a boiler. The boiler produces steam as the fluid boils, and that steam is passed through steam turbines at a high pressure, it is the expansion of gas (steam) that turns the turbine blades.

Coal power plants are classified as base load power plants because they are constructed to meet or come close to meeting continuous electricity demand all day and without interruption. Other peaking generators may be used to assist them if they are unable to meet demand, but peaking generators cost significantly more to operate than most base load power plants. Base load power plants such as steam-powered ones, are operated at their most efficient speed all the time, so their power output stays the same. The problem with baseload plants such as nuclear (steam), coal (steam), and geothermal (steam), is that electricity demand is much lower during the night than it is during the day, and these power plants can't be turned up or down much to meet electricity demand.

Coal Fired Generation - How It's Done


Classification

Coal power plants are classified as base load fossil fueled power plants. They are classified as fossil fueled because the fuel is coal, and coal is a fossil fuel. A base load power plant is one which reliably (and typically economically) provides electricity all day and continuously to everyone. [Source].


How Efficient Are Coal Power Plants?

The efficiency of these power plants is between 30% and 38%.


How Much Energy Does Coal Contain?

Units Used:

  • kJ: Kilojoule.
  • MJ: Megajoule.
  • GJ: Gigajoule.
  • Wh: Watt-hour.
  • kWh: Kilowatt-hour.
  • MWh: Megawatt-hour.
  • GWh: Gigawatt-hour.
  • TWh: Terawatt-hour.
  • L: Litre.

1 Wh = 3.6 kJ or 3600 Joules. 1 kWh = 3,600 Kilojoules. 1 MWh = 3,600,000 kJ, 3600 MJ, or 3.6 Gigajoules.


In the U.S, the average short ton of coal contained the equivalent of 19.753 million BTU hours of heat energy or or 5.789 million Wh. [Source] 1 BTU = 0.29307107 watt hours.

The electricity that can be generated from that is up to 38% of the 5.789 million watt hours which is 2.199 million Watt-hours.

A short ton is 2,000 pounds. A metric tonne is 2,204 pounds or 1,000 kg.

  • Gasified Coal (Town Gas/Coal Gas): 20.5 kj/L (5.7 Wh) of gas burned.
  • Water Gas: 11.2 kJ/L (3.1 Wh) of gas burned.

Economical Characteristics

Levelized Cost of Electricity From Coal Power Plants

2009 (USD): A low 6.2¢/kWh excluding carbon charges. [Source]

2013 (USD): 9.7 ¢/kWh.

Is Coal Sustainable?

If an energy source is economically sustainable, then it can be used to supply electricity economically for an extended period of time. (hundreds of years)

This is a non-renewable source of energy, and as the amount of coal available dwindles, the cost of it increases, the result of that is: this fuel will become very expensive and will no longer be economically viable, and since such a significant percentage of the world's electricity comes from it, the economic consequences of that would be dire.


What Is The Income of Coal Miners?

Average Income In:

  • United States: $1,140 per week. That translates to $4,560 per month if the miner works 4 weeks per month. [Source: U.S. Bureau of Labour Statistics]
  • China: $1,800 annually (an average of $150 per month). [Source: Long Island University].

What is the Environmental Impact of Coal? And How Safe Are Coal Miners?

These power plants produce and liberate greenhouse gases and other highly toxic substances such as mercury, lead, cadmium, sulfur dioxide, and carbon monoxide. The greenhouse gas of concern that they exhaust is carbon dioxide (CO2). Carbon dioxide is non-toxic, but it is a greenhouse gas that causes global warming. Global warming causes drought, and drought causes water shortages. Water shortages cause food prices to increase sharply, and in an economically detrimental manner.

It is unwise to continue to burn coal until a comparably cheap source of energy becomes available (although combined cycle natural gas is comparably cheap, this could replace coal for now), because it is already a costly source of electricity in more ways that one in widespread use, and also because the consequences of global warming remain and actually worsen for years.

These power plants emit sulfur dioxide (SO2), carbon monoxide (CO), mercury (Hg), lead (Pb), cadmium (Cd), as well as lung cancer causing soot and other chemicals, but the chemicals I mentioned are particularly toxic and harmful. Coal power plants also emit carbon dioxide, which is not toxic, but it causes global warming.

Human Cost of Coal

Of all the 69 mining deaths in the United States, including all non-coal such as metal mining, coal mining accounts for usually more than 30 of these deaths, that is in excess of 40% of all mining deaths in the U.S alone (Based on 2007 statistics). [Source]

Public Health

In the environmental impact section of coal power plants mentioned above, I mentioned the harmful substances emitted by coal power plants, and they are partly responsible for the human cost of both mining and combustion. Miners are exposed to those chemicals because they are literally in the coal mines, on the coal itself, and also, the soot emitted by coal power plants is inhaled by people and it tends to stay there and cause lung cancer, which is life threatening. The other substances are harmful in different ways due to their toxicity. They cause poisoning, which is life threatening in the case of carbon monoxide for example.

Mining

  • Destroys existing vegetation.
  • Destroys wildlife habitats.
  • Liberates methane from mines, and methane is a potent greenhouse gas that causes global warming.

Can Coal Be Clean?

There are technologies whose proponents claim are able to use coal to generate electricity cleanly by either sequestering carbon dioxide or washing/gasifying coal before burning it. This is often referred to as clean coal.

Carbon Capture and Storage (CCS)

Carbon capture and storage involves pumping power plant emissions into a storage chamber underground and compressing it so that it will not pollute the air or contribute to global warming. One significant challenge facing such technologies is the fact that compression is energy intensive.

More information coming soon.

PDF File: IPCC: CCS


Lifespan

A coal power plant can last 40-75 years.

Using Coal For Now Until It Becomes Expensive

If coal were to become very expensive in the near future, and even if governments were to ban the construction of new coal power plants, people would be stuck with high electricity prices as long as existing plants are in operation, leading to economic hardship because of the significance of the cost of electricity to manufacturing and the provision of services.

When the cost of coal eventually becomes high, people will be stuck with it for many years because of the lifespan of coal power plants, unless the government were to hastily shut down existing coal power plants prematurely, which would be a sudden shock to the economy because of the size of the coal industry (it hires plenty of people). A gradual transition to alternative sources of energy which are cheap, or of which the cost has been continually dropping because production scale increases is what they need is a good idea.

Coal Mining

Mountaintop Removal Mining (MTR)

Mountaintop removal mining is a more recent mining method than the traditional deep mining method (which involves extracting coal from underground) .

MTR involves extracting coal from above the surface of the earth, which is made accessible by blowing off mountaintops.

MTR facilitates coal extraction using fewer employees [source at the bottom of the PDF]. This is beneficial to coal mining companies due to the fact that fewer employees cost less money, but in the case of employment, it is the opposite, so it is not economical overall.

From a safety standpoint: Mountaintop removal mining facilitates avoidance of the dangerous explosions that take place in underground mines.

From a public health standpoint: Mountaintop removal coal mining involves blasting off mountaintops, this scatters coal into the surrounding environment, which sometimes consists of rivers, as well as residents. Coal contains cadmium, radioactive substances such as uranium and thorium [source], lead, and mercury.

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