Where the gas is greener

11/30/2011 | Words: Katrin Beck | Pictures: Alexander Fischer

Combined heat and power plant, farm

MTU Onsite Energy biogas engines have entered a new power class. Previously it was primarily the smaller MTU engines with outputs up to 420 kilowatts that were used in biogas applications. But now the bigger and more powerful Series 4000 is entering the fray. It has been around as a diesel or natural-gas engine for a long time. From March 2011 it will also be available as a biogas unit. And where as the smaller engines can produce 420 kilowatts of power at most, the new Series 4000 model is capable of over two megawatts. A pilot series model of the Type 12V 4000 recently successfully completed a twelvemonth trial involving 7,500 hours of duty in a biogas plant in Löningen. Operating as the base-load engine, it now supplies heat to the biogas plant and public buildings in the small town of Löningen in the German state of Lower Saxony.

The Type 16V 4000 biogas engine produces 1.6 megawatts. The next larger model, the V20 version, is capable of two megawatts. That takes MTU Onsite Energy into a new power class.?
The Type 16V 4000 biogas engine produces 1.6 megawatts. The
next larger model, the V20 version, is capable of two megawatts.
That takes MTU Onsite Energy into a new power class.

Löningen is actually just a normal small town in Lower Saxony. Life goes on quietly between Oldenburg and Osnabrück, 40 kilometers from the Dutch border. In the summer it is a magnet for tourists wanting to cycle, canoe or ride in the Hase valley; locals and holidaymakers alike enjoy a stroll through the town center, and the surrounding countryside is important for its agriculture. It is where the brothers Reinhard and Hermann Gross grow maize and grain on roughly 1,800 hectares of arable land. They sell the major proportion of the harvest but use a part of the yield for their biogas plant. It is fed every day with renewable energy crops such as maize and grain, slurry and manure, which then ferment to form biogas.

So far so good – normal country life. Biogas plants are nothing unusual any more, especially in rural areas. Nevertheless, the Löningen biogas plant has something that none of the others has: the new Series 4000 biogas engine from MTU Onsite Energy. The Gross brothers use it to supply a large part of the small town with heat. “The biogas plant is a real bonus for Löningen. It makes the town somewhere special,” observes Mayor Thomas Städtler. Because when the town’s new district heating scheme is completed, most of the public buildings will be supplied with heat by the Gross brothers. And that will make Löningen unique in Lower Saxony. “I don’t know of any comparable project here in northwest Germany,” Städtler states.

The Gross brothers grow the renewable energy crops on their own farm.?
The Gross brothers grow the renewable energy crops on their own farm.

Fewer engines, more power
It all started in 2001. Because their earnings from agricultural products were steadily declining, the Gross brothers tried their luck in energy production with a modular biogas heat and power plant. They set themselves up as Gross-Förster-Bio-Energie Hasetal with Wilfried Förster as their managing director. Up until 2008, they ran their CHP plant with ten pilot injection engines that produced 80 kilowatts each. That was enough to supply their own farm and the biogas plant with electricity and heat. Surplus electricity was also fed into the local power grid and heat supplied to a school campus with three schools, an indoor swimming pool and a meeting hall in Löningen. But because servicing and maintaining ten engines was becoming too expensive, GFBioenergie Hasetal revised their business model.

The positive experience with MTU Onsite Energy and the Series 400 engines were instrumental in our decision to look for new solutions together.Reinhard Gross, biogas plant operator

In 2008, they changed over to three CHP modules supplied by MTU Onsite Energy. From that point on, only three Series 400 engines each producing 350 kilowatts supplied the necessary electricity and heat.

Brothers Reinhard and Hermann Gross run the Löningen biogas plant.?
Brothers Reinhard and Hermann Gross run the Löningen biogas plant.

Pilot series model completes 7,500 hours
But the operators are not satisfied with successes so far achieved. Their plan for the future is one large engine to cover the base load demand and a few smaller ones to cope with the demand peaks. “The positive experience with MTU Onsite Energy and the Series 400 engines were instrumental in our decision to look for new solutions together,” relates Reinhard Gross. And MTU Onsite Energy made them a special offer: a pilot series model of the new Series 4000 biogas engine. “At first we had serious doubts whether it was the right decision. A pilot series model that nobody had any experience of was clearly a risk,” admits Reinhard Gross. Nevertheless, the team around the brothers and engineer Wilfried Förster stuck by their decision – and they haven’t regretted it so far. They built a new generator shed, and in 2009, MTU Onsite Energy engineers installed the CHP module with the new 12-cylinder biogas engine. Now they only have one engine to service in their plant and can save space into the bargain. Because, with an electrical output of 1,166 kilowatts and more than 1,300 kilowatts of heat output, this single engine replaces all three of the smaller Series 400 units. In its trial period between October 2009 and October 2010, the new biogas engine completed over 7,500 hours of duty. The verdict of the triumvirate: “Not everything was perfect, but when you look at the monthly averages for duty and down times, the engine was in use for nearly 90 percent of the time,” summarizes Wilfried Förster. “That is certainly better than we expected,” Hermann Gross adds.

More heat for Löningen
The Gross brothers were always confident their concept would bear fruit. Even before looking for a large-scale engine like the Series 4000, they and their managing director Wilfried Förster had decided together with Mayor Städtler that the existing Series 400 engines should be relocated as satellite CHP modules. As part of the new district heating scheme for the town of Löningen, work has been going on since October 2010 to install them near to public buildings to supply electricity and heat close to the point of consumption. The necessary biogas fuel from the plant is delivered to the satellite CHP modules via newly installed pipelines. That means that less heat is lost in transit. What is more, with the new district heating system, the people of Löningen will need less gas for heating and reduce the town’s carbon footprint by 1,255 tonnes of CO2 a year. To provide additional capacity, three more Series 400 engines will be installed in satellite CHP plants. “In that way, we will be able to bring in each engine individually as required and always guarantee sufficient electricity and heat,” elucidates Förster. In future, three more schools, a sports hall, the hospital, the old people’s home plus a garden center, two banks, the town hall and the open air swimming baths will be supplied. And they still won’t be at full capacity even then.

A MTU Onsite Energy fitter is mounting the mixture cooler on a biogas engine.?
A MTU Onsite Energy fitter is mounting the mixture cooler on a
biogas engine.

As they would have to pay compensation if they failed to supply heat, and they do not want to repair broken-down engines themselves, one thing was important to the operators from the start: “We need a reliable partner who deals with and solves any problems. We found that partner in MTU Onsite Energy,” Reinhard Gross reveals. The robust design and conservative tuning of the new biogas engine enable long-term troublefree operation. In other words the engine is idle much less of the time. A complete overhaul of the basic engine is not scheduled until around 64,000 hours of duty have been completed. That is more than seven years if the engine runs 24 hours a day.

We need a reliable partner who deals with and solves any problems. We found that partner in MTU Onsite Energy.Reinhard Gross, biogas plant operator

Benefits for all sides
Both GF-Bio-Energie Hasetal and the town of Löningen benefit from the business relationship. Under German law, the supplier receives payment for the electricity it feeds into the power grid. The town of Löningen, the hospital and other consumers benefit from the heat supply and save on heating costs. And the environment benefits. The operators have retrofitted their Series 4000 engine with a catalytic converter that lowers formaldehyde emission. Further investment in their biogas plant by GF-Bio-Energie Hasetal will be dependent on acquiring new heat consumers. “Responsible use of renewable energy crops such as maize and grain is very important to us. So we will only expand when the demand is there,” explains Wilfried Förster. As long as they don’t need any more themselves, they will again sell most of what they sow this spring. The rest goes in the biogas plant. Because they have always grown and harvested their own raw materials for producing biogas.

60 tonnes of renewable energy crops, 60 tonnes of slurry and ten tonnes of manure are fermented every day in the biogas plant.?
60 tonnes of renewable energy crops, 60 tonnes of slurry and ten
tonnes of manure are fermented every day in the biogas plant.

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