Are Fossil Fuels Efficient? (Coal, Oil, Natural Gas)

Are Fossil Fuels Efficient? (Coal, Oil, Natural Gas)

This is a short guide outlining the efficiency of the different types of fossil fuels (coal, natural gas, oil).

We also discuss what factors might contribute to the efficiency of fossil fuels.

 

Summary – Efficiency Of Fossil Fuels

  • Fossil fuels tend not to keep as much of their original energy input as renewables
  • Much of this has to do with the waste and inefficiencies involved with the energy conversion processes of fossil fuels (mining, refining, etc)
  • In addition, energy is used to mitigate or address the environmental and social problems caused by fossil fuels (and this energy is usually not reported on)
  • In comparison, modern renewable energy can be a lot more efficient to convert to usable energy sources like electricity
  • Efficiency numbers and %’s are usually provided as a national average, but can also vary from State to State depending on different variables and factors
  • Other analysis’ of energy efficiency mention that we have to take into account theoretical maximum efficiency, and the capacity factor of different energy sources. We also have to consider how each energy source operates in reality in a real energy system and power grid when other energy sources are also providing power to a grid. Economically, when we take into account these factors and consider efficiency, renewables still come out ahead because they don’t even have to be efficient … they just have to run enough over the course of time to pay for their capital costs … whereas the marginal operating costs of fossil fuels should place pressure on them to be efficient.

 

How Efficient Is Coal Energy?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Coal retains 29% of it’s original energy (this is a national average – so, the actual % can vary State to State)

– hortidaily.com

 

How Efficient Is Natural Gas Energy?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Natural Gas retains 38% of it’s original energy (this is a national average – so, the actual % can vary State to State)

– hortidaily.com

 

How Efficient Is Oil Energy?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Oil Energy retains 31% of it’s original energy (this is a national average – so, the actual % can vary State to State)

– hortidaily.com

 

Why Are Fossil Fuels So Inefficient?

Because of the inputs and resources required to turn fossil fuel into electricity. 

Processing, refining etc. actually requires other fossil fuels to turn a fossil fuel into electricity.

As described by Vox.com:

  • … fossil fuel combustion is wasteful [i.e. it wastes and uses a lot of energy across the conversion process]. Mining or drilling fossil fuels, transporting them, refining them, burning them, converting them to useful energy, using the energy, disposing of the waste and pollution — at every single stage of that process, there is loss. Burning fossil fuels, for electricity, heat, or transportation, inherently involves enormous levels of waste.

 

The Hidden Inefficiency Of Fossil Fuels

Something that isn’t talked about as frequently when it comes to efficiency (perhaps because it might be harder to measure), is that fossil fuels emit greenhouse gases, emit air contaminants, and have other environmental and social consequences.

These problems can use energy to either mitigate or clean up – adding to the potential inefficiency of fossil fuels.

 

How Energy Source Efficiency Numbers Are Calculated

Something that should be noted is that the numbers are based on economic efficiency:

  • Hortidaily.com explains the methodology of calculating the averages in their resource 

Borntoengineer.com also has some information on how to measure the efficiency of an energy generation method.

 

Some Other Notes On The Efficiency Of Energy Sources

Paraphrased and summarised from Michael Barnard on Quora.com, reappearing on Forbes.com:

  • Fossil fuel has to be paid for, where as the sun and wind are provided by nature for free
  • ‘Efficiency is explicitly a measurement of how much of a given resource’s energy potential gets turned into electricity’
  • ‘Solar turns around 20% of it’s energy potential into electricity’ [but the other 80% that is wasted is not expensive and is not really even a waste]
  • ‘Car engines only turn about 20% of the energy in gas into movement, with the rest being waste heat.’
  • ‘Coal plants achieve from 33% to 40% efficiency in the best cases, with the rest being just wasted heat.’
  • ‘Combined cycle gas plants, where the heat is used in addition to the mechanical energy to generate electricity manage to make it up to about 54% efficiency’
  • … with fossil fuels … we are paying for 100% of it plus the costs associated with addressing carbon emissions and other externalities … so it’s ‘arguable that we are paying for 300% of the fuel but only getting 20% to 50% out of it’
  • Each energy source has a Betz’ Limit theoretical maximum efficiency, and the theoretical maximum efficiency of wind energy isn’t that different from a combined cycle gas plant
  • … but, maximum efficiency has to be combined with the capacity factor (how much capacity for energy generation an energy source has in a given year) to determine the electricity generation potential of an energy source
  • Solar capacity factor ranges from 15% to 25%, and modern wind farms range from 40% for onshore to 77% one year for the best offshore site
  • In a real energy grid – renewable energy can be curtailed because they have to exist with nuclear and other baseload forms of generation can’t be turned down quickly
  • Nuclear and other baseload energy sources tend to have worse economics
  • Traditional/legacy forms of electricity generation tend to have low capacity factors … ‘Nuclear is high at 90% because it can’t actually run at less than that capacity factor and pay for itself’ … ‘Coal in the USA was at 60% or so a decade ago, but now it’s at 50% for the country because wind, solar and gas are cheaper so it can’t compete. Many gas plants are at 10% simply because they only turn them on to provide peak power at highest profit’
  • ‘So wind and solar don’t have to be efficient, they just have to run enough over the course of time to pay for their capital costs. Their marginal operating costs are dirt cheap, much cheaper than coal and gas plants.’

 

Sources

1. https://www.bettermeetsreality.com/renewable-energy-vs-fossil-fuels-vs-nuclear-comparison-guide/

2. https://www.hortidaily.com/article/6011458/us-what-is-the-most-efficient-source-of-electricity/

3. https://www.vox.com/energy-and-environment/2019/6/18/18681591/renewable-energy-china-solar-pv-jobs

4. https://www.bettermeetsreality.com/is-renewable-energy-efficient-solar-wind-hydro-geothermal-more/

5. https://www.borntoengineer.com/efficient-form-renewable-energy

6. https://www.forbes.com/sites/quora/2017/11/08/is-solar-energy-less-efficient-than-non-renewables/#7f8b511f4d4a

7. https://www.quora.com/If-solar-energy-is-inefficient-then-how-do-solar-energy-organizations-sell-their-products

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