Primary energy (PE) is an "energy form found in nature that has not been subjected to any conversion or transformation process. It is energy contained in raw "fuels, and other forms of energy received as input to a "system. Primary energy can be "non-renewable or "renewable.
Total primary energy supply (TPES) is a term used to indicate the sum of production and imports subtracting exports and storage changes.
The concept of primary energy is used in "energy statistics in the compilation of "energy balances, as well as in the field of "energetics. In energetics, a primary energy source (PES) refers to the energy forms required by the energy sector to generate the supply of "energy carriers used by human society.
The use of primary energy as a measure ignores conversion efficiency. Thus forms of energy with poor conversion efficiency, particularly the thermal sources, coal, gas and nuclear are overstated, whereas energy sources such as hydroelectricity which are converted efficiently, while a small fraction of primary energy are significantly more important than their total raw energy supply may seem to imply.
PE and TPES are better defined in the context of "worldwide energy supply.
Primary energy sources should not be confused with the "energy system components (or conversion processes) through which they are converted into energy carriers.
|Primary energy sources||converted
|Energy system component||to||"Energy carriers (main)|
|"Oil (or crude oil)||"Oil refinery||"Fuel oil|
|"Coal or "natural gas||"Fossil fuel power station||"Enthalpy, "mechanical work or "electricity|
|"Natural uranium[nb 2]||"Nuclear power plant ("thermonuclear fission)||Electricity|
|"Natural thorium||"Thorium breeder reactor||Enthalpy or electricity|
|"Solar energy||"Photovoltaic power plant (see also "Solar power)||Electricity|
|"Solar power tower, "solar furnace (see also "Solar thermal energy)||Enthalpy|
|"Wind energy||"Wind farm (see also "Wind power)||Mechanical work or electricity|
|Falling and flowing water, "tidal energy||"Hydropower station, "wave farm, "tidal power station||Mechanical work or electricity|
|"Biomass sources||Biomass power plant||Enthalpy or electricity|
|"Geothermal energy||"Geothermal power station||Enthalpy or electricity|
Primary energy sources are transformed in "energy conversion processes to more convenient forms of energy (that can directly be used by society), such as "electrical energy, refined "fuels, or synthetic fuels such as "hydrogen fuel. In the field of "energetics, these forms are called "energy carriers and correspond to the concept of "secondary energy" in energy statistics.
Energy carriers are energy forms which have been transformed from primary energy sources. Electricity is one of the most common energy carriers, being transformed from various primary energy sources such as coal, oil, natural gas, and wind. Electricity is particularly useful since it has low entropy (is highly ordered) and can be converted into other forms of energy very efficiently.
"Conversion efficiency varies; for thermal energy electricity and mechanical energy production is limited by "Carnot's theorem, and generates a lot of "waste heat. Other non thermal conversions can be more efficient, for example wind turbines do not capture all the wind energy, but generate very little waste heat, since wind energy is low entropy. In principle solar photovoltaic conversions could be very efficient, but current conversion can only be done well for narrow frequency ranges, whereas solar thermal is also subject to Carnot efficiency limits. Hydroelectric power is also converted very efficiently. The amount of usable energy is the "exergy of a system.
Energy accidents are accidents that occur in systems that provide energy or power. These can result in fatalities, as can the normal running of many systems, for example those deaths due to pollution.
Globally, coal is responsible for 100,000 deaths per trillion kWh.