Fuels to Generate Motion
A fuel is a liquid, solid or gaseous product used to generate heat, in the heat and electricity generation sectors, or motion in the mobility sector. In this glossary article, we refer to fuels that are used to generate motion. For a description on fuels to generate heat and/or electricity, please see separate glossary article.
Fuels to generate motion are defined as chemical substances whose energy content is utilized in technical systems to generate force or create propulsion, usually by combustion or other means of converting energy.
Fuels are distinguished as follows:
- Fuel to generate motion: a substance used for direct combustion in a combustion engine, as in automotive engineering. There are essentially three types of fuel to generate motion:
- Solid fuels (e.g. coal, biomass)
- Liquid fuels (e.g. gasoline, diesel fuel, biodiesel/FAME)
- Gaseous fuels (e.g. natural gas (CNG), biogas (Bio-CNG))
- Fuel to generate heat: a liquid, solid or gaseous product used to generate heat
While liquid fuels to generate motion are highly flammable at room temperature, natural gas only becomes flammable at 600°C and under high pressure.
Classic fuels to generate motion, such as gasoline and diesel fuel, are produced from crude oil through fractional distillation in oil refineries. Besides these, there are alternative fuels such as bioethanol and rapeseed oil, created by alcoholic fermentation, transesterification or in oil mills, for example.
Beyond “natural” components, additives may be mixed in. These additives serve various functions, especially to improve properties, e.g. to increase knock resistance, improve cold starting, and clean the intake system.
A physical comparison of the calorific values (kWh/cbm) of fuels to generate motion shows that the fuel consumption (e.g. in liters per 100 km) benefits of certain fuels to generate motion are not based on their energy content per kg, but on their higher density and correspondingly higher weight per liter. Examples include:
“Super-grade” gasoline: Density 740 kg/cbm, calorific value (in kWh/kg) 12.00 = 8.9 kWh/l
Diesel: Density 830 kg/cbm, calorific value (in kWh/kg) 11.80 = 9.8 kWh/l
In gases, energy content depends strongly on the pressure. The range of a vehicle is determined among other things by the efficiency of its power units, the volume of the tank, and the energy stored in it.
Fuels to generate motion have to meet numerous requirements and in Germany are subject to the 10th BImSchV (Federal Emissions Protection Act), which implements European Directive 98/70/EC (Directive relating to the quality of petrol and diesel fuels). Standards for fuel quality are DIN EN 228 (Automotive fuels - Unleaded petrol - Requirements and test methods), DIN EN 590 (Automotive fuels - Diesel - Requirements and test methods) and DIN EN 589 (Automotive fuels - LPG - Requirements and test methods).
In the case of biofuels, fuel quality and properties are defined in DIN EN 14214 for biodiesel/FAME and in DIN EN 15376 for bioethanol, for example. These biofuels may be added to fuels to generate motion such as diesel and gasoline in proportions defined in DIN EN 590 and DIN EN 228. For example, gasoline is marketed as E5 and E10, with the numbers indicating the respective percentage of ethanol. In accordance with DIN EN 590, up to 7% vol.-% of biodiesel/FAME can be added to mineral diesel fuel, in which case the fuel is called B7. Since 2009, B7 has been the standard fuel for motor vehicles with diesel engines in Germany.
The quality requirements of CNG/compressed natural gas are regulated throughout Europe in DIN EN 16723-2 (Natural gas and biomethane for use in transport and biomethane for injection in the natural gas network - Part 2: Automotive fuels specification).
As a resource-poor country, Germany, for example, has to import most of its fuels to generate motion. Crude oil comes mainly from Russia, the North Sea (primarily from the offshore production fields of the Netherlands and the United Kingdom), and North Africa. Natural gas also comes from Russia and the North Sea. Natural gas is produced in Germany, but not in sufficient quantities, so that most of the demand must be covered by imports from Russia and Norway.
An exception to this are biofuels, which are also produced domestically, especially biodiesel from rapeseed and bioethanol from cereals, and therefore only imported in small quantities. Germany is a very heavily forested country, so a large proportion of the resources required for wood-based fuels can be covered by domestic production. Biogas (bio-CNG) can also be produced regionally at biogas plants, and then supplied to distributors or consumers (e.g. at a filling station pump).
In Germany, fuels to generate motion are taxed under the Energy Tax Act (EnergieStV). It implements the provisions of the European Energy Tax Directive (Directive 2003/96/EC) and emerged from the 2006 Oil Tax Law. This consumption tax is based on the volume/weight or unit of energy (MWh) of the fuel to generate motion. The tax rate depends on the type of fuel to generate motion. At this time, diesel fuels are taxed at lower rates than gasolines in Germany, and natural gas for the propulsion of vehicles is also taxprivileged.
Germany has also set reduced tax rates for fuels to generate heat as compared to fuels for generating motion. Heating oil and diesel fuel are very similar in many ways. So because heating oil is taxed at a lower rate in Germany than diesel fuel, its use as a vehicle fuel to evade taxes is illegal. To avoid confusion, heating oil (and low-sulfur heating oil) is labeled with heating oil dye (HKZ, also known as Euromarker) consisting of a red dye and a marking substance known as Solvent Yellow 124.
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Status: December 2015
All information subject to change. Errors and omissions excepted.