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:
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- 1 calorie = 4.1868 Joules
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- 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.
| Fuel | NCV (Mcal/tonne) | Joules (GJ/tonne) | Btus (MBtu/tonne) | Watt Hours (kWh/tonne) |
|---|---|---|---|---|
| Crude Oil | 10,366 | 43.40 | 41.14 | 12,056 |
| Heavy Fuel Oil | 9,690 | 40.57 | 38.45 | 11,269 |
| Light Fuel Oil | 9,840 | 41.20 | 39.05 | 11,444 |
| Burner Oil | 10,070 | 42.16 | 39.96 | 11,711 |
| Gas/Diesel Oil | 10,450 | 43.75 | 41.47 | 12,153 |
| Natural Gas | 9,052 | 37.90 | 35.92 | 10,527 |
| Butane/Propone | 10,963 | 45.90 | 43.50 | 12,750 |
| Ethane | 11,130 | 46.60 | 44.17 | 12,944 |
| Aviation turbine fuel | 10,485 | 43.90 | 41.61 | 12,194 |
| Petroleum Coke | 5,923 | 24.80 | 23.5 | 6,888 |
| Average | 9,797 | 41.00 | 38.88 | 11,394 |
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.
| Fuel | NCV (Mcall/tonne) | Joules (GJ/tonne) | Btus (Btu/tonne) | Watt hours (kWh/tonne) |
|---|---|---|---|---|
| Peat | 4,371 | 18.30 | 17.35 | 5,083 |
| Lignite/Brown Coal | 5,493 | 23.00 | 21.80 | 6,388 |
| Sub-bitumous Coal | 5,828 | 24.4 | 23.13 | 6,778 |
| Bitumous | 6,162 | 25.8 | 24.45 | 7.167 |
| Dry Steam Coal | 6,329 | 26.50 | 25.12 | 7,361 |
| Anthracite | 7,404 | 31.0 | 29.38 | 8,611 |
| Average | 5,931 | 28.75 | 27.25 | 7,986 |
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.
| Fuel | NCV (Mkcal/tonne) | Joules (GJ/tonne) | Btus (MBtu/tonne) | Watt Hours (kWh/tonne) |
|---|---|---|---|---|
| Wood | 2,914 | 12.2 | 11.56 | 3,389 |
| Wood Pellets | 4,013 | 16.8 | 15.92 | 4,667 |
| Straw | 3,201 | 13.40 | 12.70 | 3,722 |
| Poultry Litter | 1,815 | 7.60 | 7.20 | 2,111 |
| Meat and Bone | 4,013 | 16.80 | 15.92 | 4,667 |
| Industrial Waste | 3,630 | 15.20 | 14.41 | 4,222 |
| Hospital Waste | 3,177 | 13.30 | 12.61 | 3,694 |
| Tires | 7,261 | 30.40 | 28.81 | 8,444 |
| Biodiesel | 8,885 | 37.20 | 35.26 | 10,333 |
| Bioethenol | 6,401 | 26.80 | 25.40 | 7,444 |
| Average | 3,982 | 16.67 | 15.80 | 4,631 |
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.