Cultivating Biogas-Fueled Power: MTU introduces Series 4000 biogas engines for CHP applications by roberta prandi
When the profit margins from conventional agricultural crops, such as corn, cereals or potatoes, dropped in Germany at the end of the 1990s, many farming enterprises looked for alternative ways of doing business and increasing revenue. One avenue that gained
interest rapidly was the installation of biogas-fueled combined heat and power (CHP) plants. Further increasing interest were subsidies from the German government for producing electricity from biogas under specific conditions.
Reinhard and Hermann Gross, who owned a 1800 ha farm in Löningen, Germany, opted to expand their operation with a biogas CHP plant. In 2001, the brothers founded GF-Bio-Energie Hasetal GmbH, and built a biogas-operated heat and power plant, fueled by agricultural waste, manure and chicken dung. Initially, the power plant comprised 10 dual-fuel aggregates, each delivering a maximum of 80 kW power. At the same time, a biogas plant with five anaerobic digesters was built.
With time, the stringent emissions regulations and the need for higher efficiency pushed the two brothers to rethink the concept of their biogas plant and they switched to Otto gas engines. Thus, in 2008 three CHP modules by MTU Onsite Energy were installed, featuring the company’s 400 Series biogas engines with an electrical output of 350 kW each. Based on this experience, it was a short step for the two entrepreneurs to decide to try a pre-series unit of the new MTU 4000 Series biogas engines, which successfully completed practical trials at the farm, surpassing about 7500 hours of operation. In December, MTU announced the biogas Series 4000 engines would be available to market in March.
A CHP module with a 12-cylinder 4000 biogas engine rated for 1166 kW of electrical power and over 1300 kW of thermal output was installed in 2009. The GC 1166 B5 module produces electricity and heat, and has the same output as three of the previous modules operated by the 400 Series engines. MTU Onsite Energy also said the new unit registered an electrical efficiency of 42.5%. The manufacturer said the new 4000 Series biogas engines are based on the diesel engine from which a natural gas version was already derived.
Some design and manufacturing changes were introduced for use with biogas, such as more robust steel pistons and modified combustion chamber geometry. The engine control system was also adapted for biogas operation. After six months in operation, the engine was inspected at the MTU headquarters in Friedrichshafen, Germany. The company said all components, including the newly designed ones, showed virtually no sign of wear. Since October 2010, the CHP module with the 4000 Series biogas engine has been working as a baseload unit for the biogas plant, with the smaller 400 Series modules working as satellite units. These satellites
will produce power and heat for local use, optimizing the utilization of the produced heat.
The 12-cylinder 4000 Series biogas engine was also equipped with a catalyst that will reduce the emissions of formaldehyde. So the CHP plant by GF-Bio-Energie Hasetal GmbH will profit not only from the state contribution for biogas electricity production, but also from an additional formaldehyde bonus by the German government. MTU Onsite Energy announced
that the market introduction of the 4000 Series biogas engines for power generation will take place in stages from March 2011, with 8-, 12-, 16- and 20-cylinder versions covering
an output range from around 770 to 2000 kW.