Fuel

A fuel is a chemical substance whose stored energy can be converted by combustion into usable energy.

Fuels are classified according to various criteria, such as according to their physical state into solid, liquid and gaseous fuels. Depending on the origin distinguishes between natural, refined or synthetic fuels. Fuels can be organic in nature, such as petroleum, natural gas or coal, or inorganic such as hydrogen or carbon monoxide. By type of energy release fuels are divided into chemical fuels that release thermal energy by oxidation and electrochemical fuels that are used for example in fuel cells to generate electricity. Fuels can also be present as fossil fuels or as fuels from renewable resources ( biomass fuels such as wood, biofuels, biogas). Nuclear fuel, such as enriched uranium and plutonium by nuclear fission or as deuterium and tritium, which can release energy through nuclear fusion, do not belong to fossil fuels.

The quality of a fuel is characterized by the heating value or calorific value. The calorific value also takes into account the use of the heat of condensation of the water present as vapor in the flue gas ( condensing technology ). When absolutely dry fuels that do not contain chemically bound hydrogen, calorific value and net calorific value are identical.

Fossil Fuels

Fossil fuels are usually built up over a long time, often lasting millions of years, bio - and geochemical processes. Solid fuels subject on the one coalification, the accumulation of carbon in soil layers completed by organic matter. The two main steps of coalification are the transition of organic matter, which consisted mostly of higher plant species such as woods or ferns, for lignite and the further transition of lignite to hard coal. The origin of petroleum lower marine animals and plants are suspected.

The entire existing fuel stocks are called resources. They are divided in suspected and proven resources. Demonstrated resources are further subdivided into degradable and non-degradable probably resources. Does the technical degradation of a resource secured, this resource is called a reserve.

The energy content of solid fossil fuels is often specified in so-called coal equivalent ( tce).

Fuel prices

The world price for fuels varies due to many factors. In terms of standard coal, the price fluctuated between 1970 and 2004:

• In oil by 900%
• For coal by 200%

The prices for the main fuels have a significant impact on national economies. Sharply rising prices can aggravate existing inflation, for example.

Physical state and use

Fuels are used in all three classical states of matter (solid, liquid and gaseous) are used. They are fed a wide variety of uses.

• Solid fuels, such as especially hard coal, brown coal and wood, are used today primarily for electric power generation in the steam power plant. In addition, solid fuels for process engineering and production of metal in the smelting of iron and steel are needed. The importance for the heating of buildings is only slight. The energy content is given in coal equivalent ( tce).
• Have liquid fuels as various petroleum products ( gasoline, diesel, heating oil) and a significant proportion of biofuels in transport and for heating buildings. They are also used as a raw material for products in the chemical industry. The energy content is expressed in oil equivalent ( dE ).
• Gaseous fuels such as natural gas and biogas are mainly used for building heating and power generation. They are also used in the chemical industry as raw material and fuel. Natural gas and fuel oil are burned in smaller and medium-sized steam boilers for generating steam. The energy content is expressed in kWh / kg.

Origin of fuels

Most of the fuels used in Germany have to be imported. This applies primarily to the liquid and gaseous fuels, as Central Europe in this area has only limited internal resources. Solid natural fuels are, however, encouraged in this geographic area, as Bodenschatz in larger amounts, the costs incurred in the promotion costs are supported by subsidies, in order to keep the domestic fuel compared to the prices paid on the world market competitive.

The provision of fuels from renewable raw materials ( biomass fuels ) has for the energy and transport sectors, a growing importance. In 2009, 5.5 % of the required final energy in Germany was provided by biogenic fuels (as bioenergy ). So they make up about 2/3 of renewable energy ( total 10.1%) out. The majority of the bioenergy accounts for heat. The total potential of bioenergy in Germany is limited, so that only a portion of the energy requirements can be met by them.