Die PEFC in der Hausenergieversorgung

The » VNG-Verbundnetz Gas AG« of Leipzig proved with their project »natural gas house« the feasibility of a decentralized CHP-plant based on natural gas in a total energy compound. A gas-engine mini block-CHP was utilized. Since gas engines show the highest degree of efficiency during peak load, they are only suitable for base load coverage. Also the CHP coefficient of the gas engine lies mainly at 0.7 and is not changeable. The PE-fuel cell on the other hand reaches the highest electrical coefficient already well below partial load. During peak load, the efficiency degree even decreases slightly. Thus, fuel cells can be operated also based on heat over a larger load range with a good electrical degree of efficiency. While during the winter months the heat generated in the process can easily be used for the heat supply, the desired power coefficient during the summer months is >1, a relatively higher power generation. In order to realize this technologically, the HGC - Hamburg Gas Consult GmbH, Hamburg, developed a house energy center (HEC) based on a PE-fuel cell (figure 4). Here the above mentioned operational behavior of the fuel cell was taken into consideration. A catalytic burner, downstream from the anode is being supplied by the residue gas from the anode. With the conversion ratio of the H 2 in the fuel cell, a part of the heat extraction can also be regulated. Accordingly, the thermal load has to be adapted to the heat demand of the customers through the design of the catalytic burner. At the same time, the heat which is generated in the cellstack at an operation temperature of 60 to 80 °C as well as from the exhaust gas from the fuel regeneration, can be transferred as utilization heat. Possibilities and Technology of the HEC The HGC found a partner with the American Power Corporation (APC), Boston/USA, who has the necessary experience and knowhow to develop and produce PE-fuel-cell-stacks as well as fuel regeneration systems. The PEFC-power generation aggregate developed by APC was reconstructed into a CHP-system as a cooperation project with the HGC. The house energy center has a gross capacity of 3.5 kW. After deducting its own power demand and the inverter losses of appr. 0.5 kW, an electrical net capacity of 3 kW remains. With the aid of a battery storage a peak load coverage of max. 5 kW over a time period of 1 hour becomes possible. The max. electrical degree of efficiency is reached at 1 kW and amounts to 38 %. During peak load operation of 3 kW this value decreases to 32 %. Since the basic load of a one family house lies below 1 kW, the HEC will be operated mainly with the optimal degree of electrical efficiency. The technical data of the HEC are represented in table 1. Pilot project Natural-Gas-House The current plant technology of APC did not correspond with the demands of European customers. Only after APC and HGC developed a heat extraction system for the existing gas-operated power generation aggregate, a partner was found with the VNG, Leipzig, in order to test operate the aggregate in Europe. Together with VNG, the specific frame conditions of an Alpha-Test-Unit for the first project were laid down. The performance data of the HEC which was used for the first time, have been custom made to the demands of a gas-supplied one-family house.