Suppose you have a typical coal mining process composed of the following steps:

(1) Excavation -> (2) Crushing -> (3) Storage -> (4) Rail -> (5) Power Station

The idea is the coal is excavated out of the ground, crushed and processed, stored, and finally transported by a diesel train to the power station. It is very simplistic and probably missing some steps, but it's just for ease of calculation purposes.

Now I'm interesting in finding the energy loss in each component of this process, scaled down to 1KW.

For example, if I start of with 1KW at the beginning of the process (step 1), how much usable power would be available for me at the end (step 5)?

  • 1
    $\begingroup$ So fuel consumption for all the machines used in the excavation process convert litres of fuel to an energy equivalent to match all the steps. Repeat for all steps. A common set of calculations often called grey energy. Usually set as a homework task for students in engineering, sustainability etc. $\endgroup$ – Solar Mike Nov 15 '20 at 7:12
  • $\begingroup$ If this is your homework, you need to show more of your work and narrow down the question. But it loks like you want to know the Energy return on investment (EROI) of coal so how about googling that. $\endgroup$ – mart Nov 16 '20 at 6:48

Given that Joules (J) is the SI unit for energy I would have thought it would be better to use Joules instead of Watts for the comparison.

From one website, the energy density of black coal varies from 13 to 30 MJ/kg (or GJ/t) of coal. It depends on the type of coal mined and the location of the deposit.

Now all you need to do is find the typical amount of energy used to process either a kilogram or tonne of coal from each of the process stages. Using consistent units subtract the energy usage per kilogram or tonne of coal processed from the energy density of coal. You might also want to include the energy efficiency of the electricity generating station.

Your stages 2 & 3, Crushing and Storage, might be combined into one stage called Processing which could incorporate crushing, washing, storage and reclamation from the store.

As for transportation, the energy usage will be determined by the transportation mode: truck, rail, barge, ship or conveyor belt.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.