The energy plan was developed by ARGE HafenCity whose major partners are Vattenfall Europe Hamburg, Heat Division and Vattenfall Europe Contracting. ARGE has put its weight behind a future-oriented ecological heat supply which brings together local area heating, engine-driven combined heat and power (CHP) plants, solar heat installations and the HotModule. It’s a tribute to this blend of technologies that, in HafenCity, a kilowatt-hour of heat energy releases only 160 grams of carbon dioxide – about 20 per cent lower than the level specified by the client, HCH HafenCity Hamburg GmbH. 
HafenCity’s heating requirements will chiefly be met by Vattenfall’s Tiefstack and Wedel heat plants, plus the HafenCity district heating station and the Borsigstraße refuse recycling plant. These mostly generate electric power and heat as CHP systems – as do the planned cogeneration plants with their gas engines and fuel cell. The HotModule in HafenCity’s district heating station is Vattenfall’s first in Europe. Its location on the power station site will give Vattenfall staff the chance to gain experience in operating the fuel cell. It will provide up to 245kW of electric power and 170kW of thermal power.

“Our HotModule fits perfectly into this innovative urban construction project,” says Michael Bode, Managing Director of MTU CFC Solutions GmbH. “Because the construction and infrastructure are being matched to complement each other, this future-oriented energy technology can reach its full potential here.” The MTU CFC Solutions high-temperature fuel cell will operate as a pilot within the project for the time being. “If the HotModule is fully market-ready by the time the planned cogeneration plant is due to be built in 2009, we can foresee an opportunity to install fuel cells instead of the gas engines that are currently planned,” explains Jesko Mohr of Vattenfall Europe who is in overall charge of the project.

From the technical point of view, the HotModule is already a mature product which, for example, is reliably powering a local heating system in Krefeld. Compared with conventional technologies, HotModule boasts an electricity yield of 47 per cent at an overall efficiency of 90 per cent. In terms of noise emissions, the fuel cell has a clear advantage over engines and turbines because the electrochemical process produces virtually no noise and the auxiliary machinery operates very quietly. The HotModule is therefore predestined for inner-city applications and is even suitable for direct installation within a building where heat is needed. Installation of miniature power stations close to the end user has the effect of reducing transport losses in the power and heat network, which makes a further contribution to energy efficiency.

“This innovative technology allows new avenues in energy supply to be opened up because decentralized energy supply will have an ever greater part to play in the future,” says Bode, emphasizing the role of the HotModule. Because the molten carbonate fuel cell can operate on biogas and sewage gas as well as natural gas (as planned in Hamburg for the immediate future), there is even an opportunity for carbon neutral energy provision.

Operation of the HotModule

HotModule is a molten carbonate fuel cell (MCFC) consisting of a cylindrical steel container with a horizontally arranged fuel cell stack, starting equipment, catalytic burner and mixing chamber. Then there is the media supply module with fuel and water treatment, and an inverter which converts the direct current generated in the plant ready to be fed into the AC grid. A further element in the plant takes care of heat extraction.

Suitable fuels include gases with high methane content such as natural gas, biogas and sewage gas, but also liquid fuels like methanol. As in all fuel cells, the electrochemical process is based on a reaction between hydrogen and oxygen which liberates electric power and heat. Methane (e.g. natural or biogas) and water vapor are fed to the anode. Here a catalytic reaction produces hydrogen. This then reacts with the carbonate ions in the electrolyte to form water and carbon dioxide. During this process, electrons are liberated at the anode and flow via a consumer (in this case the grid) to the cathode. On the cathode side, carbon dioxide and atmospheric oxygen react with the electrons liberated in the anodic reaction to form carbonate ions. Finally these migrate through the electrolyte to the anode concluding the electrochemical cycle.

Exhaust air from the fuel cell contains water vapour and carbon dioxide. Pollutant emissions are negligible; in particular no traces of either SO2 or NOx are detectible.

The molten carbonate fuel cell is suitable for continuous supply of electric power and heat. The elevated supply temperature also enables efficient year-round operation of absorption refrigeration equipment (cooling-heating-power system).