<p>The efficiency of coal as a source of electricity is very low: typically of the order of 30%. So losses are of the order of 70%. But losses due to energy expended in the extraction of the coal itself only form a very small proportion of this.</p>

<p>Estimates for extractive losses tend to be <a href="http://dx.doi.org/10.3390/su3101796">of the order of 0.5-5%</a>. That's a huge relative range, because the energy density of different types of coal (J/kg) can vary by a factor of 5; the coal could come from a deep mine or an open-cast; and the amount and kind of mechanisation varies hugely.</p>

<p>But these huge <em>relative</em> variations are completely swamped in <em>absolute</em> terms by the other losses, which are at the very best 20%, and can be 65% or so. Which is why there's not a huge amount of literature on the energy inputs to coal extraction: it's such a small part of total losses, that it gets lost in the rounding.</p>

<p>In the British residential electricity supply, there's about 7% losses from local distribution (UK figure), 2-3% from transmission grid, and about 60% losses at the plant itself, in the form of heat (NB efficiencies here are multiplicative, rather than additive). The British average for 2013 was 64.2% losses in plant - see <a href="https://www.gov.uk/government/statistics/electricity-chapter-5-digest-of-united-kingdom-energy-statistics-dukes">DUKES 2014</a> table 5.9</p>

<p>CHP plants mitigate this by capturing a large share of the heat, for distribution in local heat grids. But they still have losses of 5-25% at the plant itself, and then further losses in the heat and electricity distribution system. Call it 20% losses in the best case. Denmark has a lot of high-efficiency coal plants and CHP, but still only managed 55% efficiency, so 45% losses (Danish Electricity Supply '08 Statistical Survey, Table 10).</p>

CC BY-SA 3.0
2014-08-24T14:34:54.217Z
2014-08-24T15:22:53.273Z
2014-08-24T15:22:53.273Z
410 gone
<p>Coal is still a major source of energy for generation of electricity. So how much energy is used to extract a unit (tonne/kilogram etc) of coal? And thus what is the efficiency of coal as a source of energy?</p>

CC BY-SA 3.0
2014-08-22T04:16:09.337Z
The answer would vary by country and mining method. Strip vs. longwall vs. drift vs. slope vs. mountaintop vs. open-pit... Do you use many Chinese miners or mighty German [Baggers](https://en.wikipedia.org/wiki/Bagger_293)?
Deer Hunter
CC BY-SA 3.0
2014-08-22T12:57:54.930Z
Also the coal deposit. Eg. quality of coal, is it heavily faulted, geological location, etc.
winwaed
CC BY-SA 3.0
2014-08-23T08:40:34.110Z
Given my lack of knowledge about mining/ coal types I'm looking for a best case / worst case scenario. The man vs mechanical power is an interesting one - in terms of energy efficiency is it better to use a massive machine or a mass of people!
Cycling Engineer
<mining><economic-geology><coal>
How many joules are required to mine a unit of coal?
Cycling Engineer
# How many joules are required to mine a unit of coal?

(Asked by: username_0 on 2014-08-21)

Coal is still a major source of energy for generation of electricity. So how much energy is used to extract a unit (tonne/kilogram etc) of coal? And thus what is the efficiency of coal as a source of energy?

**Tags:** mining, economic-geology, coal

> **Comments:**
> **username_1**: The answer would vary by country and mining method. Strip vs. longwall vs. drift vs. slope vs. mountaintop vs. open-pit... Do you use many Chinese miners or mighty German [Baggers](https://en.wikipedia.org/wiki/Bagger_293)?  
> **username_2**: Also the coal deposit. Eg. quality of coal, is it heavily faulted, geological location, etc.  
> **username_0**: Given my lack of knowledge about mining/ coal types I'm looking for a best case / worst case scenario. The man vs mechanical power is an interesting one - in terms of energy efficiency is it better to use a massive machine or a mass of people!  

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## 1 answers

### Answer by username_3 on 2014-08-24. Score: 12 | Accepted answer

The efficiency of coal as a source of electricity is very low: typically of the order of 30%. So losses are of the order of 70%. But losses due to energy expended in the extraction of the coal itself only form a very small proportion of this.

Estimates for extractive losses tend to be [of the order of 0.5-5%](http://dx.doi.org/10.3390/su3101796). That's a huge relative range, because the energy density of different types of coal (J/kg) can vary by a factor of 5; the coal could come from a deep mine or an open-cast; and the amount and kind of mechanisation varies hugely.

But these huge *relative* variations are completely swamped in *absolute* terms by the other losses, which are at the very best 20%, and can be 65% or so. Which is why there's not a huge amount of literature on the energy inputs to coal extraction: it's such a small part of total losses, that it gets lost in the rounding.

In the British residential electricity supply, there's about 7% losses from local distribution (UK figure), 2-3% from transmission grid, and about 60% losses at the plant itself, in the form of heat (NB efficiencies here are multiplicative, rather than additive). The British average for 2013 was 64.2% losses in plant - see [DUKES 2014](https://www.gov.uk/government/statistics/electricity-chapter-5-digest-of-united-kingdom-energy-statistics-dukes) table 5.9

CHP plants mitigate this by capturing a large share of the heat, for distribution in local heat grids. But they still have losses of 5-25% at the plant itself, and then further losses in the heat and electricity distribution system. Call it 20% losses in the best case. Denmark has a lot of high-efficiency coal plants and CHP, but still only managed 55% efficiency, so 45% losses (Danish Electricity Supply '08 Statistical Survey, Table 10).


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