Energy Content of Fuels

Energy Content Explained

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The energy content of any organic fuel is defined as the fuel’s primary energy.  Primary energy is measured given the fuels calorific value or the heat generation from the complete combustion of one unit of fuel under well-defined conditions.  The calorific value can be a gross or net number, depending on whether the combustible heat released takes into account the vapor condensation of water.  Power production efficiency is typically calculated using Net Calorific Value (NCV) after water vaporization.

The solid, liquid or gaseous fuels used in thermal power plants are mainly coal, lignite, natural gas, and petroleum oils (such as crude oil, fuel oil and heating oil). However, there is quality variation within the fuel types and additional fuels available.  The following tables compare the average energy content of the common fuels using different units of measure: NCV, joules, Btus and Watt hours.

Energy Conversion Factors

The following conversions were used to generate the energy content tables:

  • 1 calorie = 4.1868 Joules
  • 1 Btu = 1.055 055 852 62×103 Joules
  • 1 kWh = 3.6×106 Joules

Oil and Gas Products

Oil products have the highest energy density among the potential fuels for power generation, but they also have the highest prices.

FuelNCV
(Mcal/tonne)
Joules
(GJ/tonne)
Btus
(MBtu/tonne)
Watt Hours
(kWh/tonne)
Crude Oil10,36643.4041.1412,056
Heavy Fuel Oil9,69040.5738.4511,269
Light Fuel Oil9,84041.2039.0511,444
Burner Oil10,07042.1639.9611,711
Gas/Diesel Oil10,45043.7541.4712,153
Natural Gas9,05237.9035.9210,527
Butane/Propone10,96345.9043.5012,750
Ethane11,13046.6044.1712,944
Aviation turbine fuel10,48543.9041.6112,194
Petroleum Coke5,92324.8023.56,888
Average9,79741.0038.8811,394

Coal Products

Coal products are among the best value from an energy density and price standpoint, but new regulations to control emissions are making the fuels inherently more expensive.

FuelNCV
(Mcall/tonne)
Joules
(GJ/tonne)
Btus
(Btu/tonne)
Watt hours
(kWh/tonne)
Peat4,37118.3017.355,083
Lignite/Brown Coal5,49323.0021.806,388
Sub-bitumous Coal5,82824.423.136,778
Bitumous6,16225.824.457.167
Dry Steam Coal6,32926.5025.127,361
Anthracite7,40431.029.388,611
Average5,93128.7527.257,986

Biomass & Renewable Fuels

Biomass and other renewable fuel sources can offer among the best value from a price and environmental standpoint.  However, not all renewable fuel sources are clean and reliable supply sourcing can be difficult.  At the same time, furnace residues from many biomass products can harm generation equipment and increase O&M costs.

FuelNCV
(Mkcal/tonne)
Joules
(GJ/tonne)
Btus
(MBtu/tonne)
Watt Hours
(kWh/tonne)
Wood2,91412.211.563,389
Wood Pellets4,01316.815.924,667
Straw3,20113.4012.703,722
Poultry Litter1,8157.607.202,111
Meat and Bone4,01316.8015.924,667
Industrial Waste3,63015.2014.414,222
Hospital Waste3,17713.3012.613,694
Tires7,26130.4028.818,444
Biodiesel8,88537.2035.2610,333
Bioethenol6,40126.8025.407,444
Average3,98216.6715.804,631

The biomass table makes clear that the water content of the fuel is important in determining the realized energy content since water vaporization in a furnace will consume large amounts of energy.

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