Biogas engine
A biogas engine is an engine that can be operated permanently with biogas as fuel. It is usually used as part of a block- type thermal power station to generate electricity and heat with bioenergy . Engines that run on biomethane ( purified biogas ) do not come under this designation, as they are technically the same as natural gas engines .
Motor types
Both pilot injection engines derived from diesel engines and gasoline-Otto engines converted to gas can be used as biogas engines .
The main challenge for biogas engines is that the combustible fraction in the biogas ( methane ) is only 50–75% and sometimes fluctuates significantly. In addition, there may be considerable amounts of ingredients that are potentially harmful to the engine (water, hydrogen sulfide ). While gasoline engines can burn biogas directly from a methane concentration of 45%, pilot injection engines always require a certain amount of pilot oil, but have a higher thermal efficiency than gasoline engines. In Germany, biogas engines may use a maximum of 10% ignition oil. Modern pilot injection engines, however, get by with 2% pilot oil. In systems that have been in operation since 2007, the ignition oil must also be made from renewable raw materials so that the electricity generated is remunerated in accordance with the Renewable Energy Sources Act (EEG).
In addition to these most widespread technologies, other types of engines are suitable for generating power and heat from biogas. The micro gas turbine , in which electricity is generated by a high-speed generator that is directly coupled to a turbine, requires less maintenance than classic combustion engines and generates a higher temperature level of the waste heat, but achieves comparatively low electrical efficiencies with high investment costs. The crank loop motor, a two-stroke engine with a scotch-yoke crank drive (crank loop) instead of connecting rods, has not been widely used in practice .
Areas of application
As a rule, biogas engines are operated as part of the combined generation of electricity and heat in block-type thermal power stations in close proximity to biogas plants. The electricity generated is fed directly into the public grid within the framework of the Renewable Energy Sources Act (EEG). Part of the heat is required as process heat for the operation of the biogas plant, but the majority is available as usable heat energy for the generation of hot water, heating, process heat or for air conditioning. If the heat consumers are not in the immediate vicinity of the biogas plant, biogas motors are operated up to several kilometers away from the biogas plant. In this case, the gas is transported to the biogas engine via a biogas line (micro gas network).
If biogas is used in engines to drive motor vehicles, it is treated biogas ( biomethane ). This meets the quality requirements for natural gas so that it can be used in conventional natural gas engines .
literature
- Agency for Renewable Raw Materials (NR), 2008: Biogas - An Introduction . 5th, revised edition. ( 6th edition 2009, online ; PDF file; 1.2 MB)
Individual evidence
- ↑ BHKW-Anlage.de - micro gas urine. ( Memento of the original from May 1, 2006 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved June 17, 2009
- ↑ Greenvironment - micro gas turbine ( Memento from July 9, 2009 in the Internet Archive )
