Earlier this year the German federal minister of Economics and Technology, Karl-Theodor zu Guttenberg, unveiled a new cogeneration fuel cell system from MTU Onsite Energy (a Tognum brand) at the Weißbräu brewery in Erdinger. The unit, a HotModule HM300 distributed energy system, generates electrical power and heat from biogas – the power output is about 240 kW while the thermal output is better than 200 kW. The Erdinger Weißbräu brewery uses the latter to heat the brewery buildings and to heat water for the process.

“This innovative fuel cell serves to combine what is sensible in terms of energy policy with what is necessary for climate protection. Global warming and the decline in fossil fuels not only require a steady expansion in the use of renewable energy sources, but, to an even greater extent, an increased utilisation of efficient and innovative technologies. Here is where our future prospects lie – particularly for the overall German economy” said the minister. “The brewing industry is an intensively energy-consuming business. For this reason, we are continuously looking for possibilities to use energy more efficiently and to become less dependent on fossil fuels“, said Peter Liebert, managing director of the brewery’s engineering division.

The system

Erdinger uses vast quantities of water at various temperatures for the brewing process and to clean the equipment. Before being flushed into the public sewage system, the waste water is pre-conditioned via an in-house anaerobic pre-sewage treatment system. A by-product of this process is biogas with an 85 % methane content, making it an excellent energy source for the fuel cell – a regenerative and almost cost-free waste product facilitating annual CO2 reductions of up to 1200 tons. A gas cleansing system (also developed by MTU, in Ottobrunn, near Munich) removes any sulphur residues from the biogas which would otherwise be detrimental to the fuel cell stack. At a temperature of about 650°C the biogas is reformed into hydrogen which reacts electrochemically with the airborne oxygen. Almost 50 % of the biogas energy content is converted into electrical power, while more than 40 % translates into waste heat. Taken together, the two streams result in a system overall efficiency of more than 90 %. Apart from its high degree of efficiency, the fuel cell’s particular forté is its emission levels, which are negligibly low. Nitrous and sulphur oxides are nearly non-detectable, and carbon monoxide emissions are almost ten times lower than in engine-powered cogeneration systems.

The brewery’s heat requirement levels, which are high throughout the year, make the HotModule a good fit for this type of application, since its inherent advantages are shown to best effect in continuous operation.