Development of a 400 W High Temperature PEM Fuel Cell Power Pack: Fuel Cell Stack Test

Søren Juhl Andreasen, Mads Bang, Anders Korsgaard, Mads Pagh Nielsen, Søren Knudsen Kær

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Abstract

When using pressurized hydrogen to fuel a fuel cell, much space is needed for fuel storage. This is undesirable especially with mobile or portable fuel cell systems, where refuelling also often is inconvenient. Using a reformed liquid carbonhydrate can reduce this fuel volume considerably. Nafion based low temperature PEM (LTPEM) fuel cells are very intolerant to reformate gas because of the presence of CO. PBI based high temperature PEM (HTPEM) fuel cells can operate stable at much higher CO concentrations. This makes the HTPEM very suitable for applications using a reformer, and could simplify reformer design because CO removal is not needed. A fuel like methanol would be a preferable choice for reforming when using HTPEM fuel cells because of its high energy density and low reforming temperatures. The thermal integration and use of HTPEM fuel cells with methanol reformers show promising results. This work demonstrates the use of HTPEM fuel cells (HTPEM) in a 400 W fuel cell power pack. The fuel cell system concept uses a 30 cell HTPEM fuel cell stack designed at the Institute of Energy Technology, Aalborg University. The MEAs employed are Celtec P-series by Pemeas, with an active area of 45cm². The development of the bipolar plates and the stack design itself is an ongoing activity using CFD and optimizing for low pressure drop. Later versions of the stack design is expected to result in a much shorter stack. When using pure H2, the hydrogen circuit is running dead end with occasional purging. Single cell life time tests indicate that very infrequent purging does not accelerate degradation severely. This is a great advantage compared to the LTPEM which often has problems with flooding when not purged. The air supply is realized using a low power axial fan with a high turn down ratio. The stack is placed in an insulation box and the temperature controlled by electrical heating elements. When loading the stack at its nominal load of 400 W it produces enough heat to keep this temperature. For control system design and location of optimal operating conditions, a system model is made, including a HTPEM fuel cell model, expressing the cell voltage as a function of the current density, temperature, CO concentration and stoichiometries. Simulation results from this model are shown. The system model and control design is verified with the actual setup in the lab. For the use of the fuel cell stack in a power pack, a high efficiency DC/DC-converter is designed. The overall control of the power conditioning and the power pack itself is also derived from modelling of the DC/DC converter. Comparing the LTPEM and the HTPEM, the HTPEM fuel cell has a lower cell voltage than the LTPEM, but the developed power pack demonstrates some of the advantages by using a HTPEM fuel cell. This initial system is very simple and there is no need for humidification of the species like in a LTPEM fuel cell system. The use of the HTPEM fuel cell makes it possible to use reformed gas at high CO concentrations without, still with a stable performance.

OriginalsprogEngelsk
TitelProceedings of the Fuel Cell Seminar 2006 Conference
ForlagFuel Cell Seminar
Publikationsdato2006
StatusUdgivet - 2006
BegivenhedFuel Cell Seminar 2006 Conference - Honolulu, Hawaii, USA
Varighed: 13 nov. 200617 nov. 2006

Konference

KonferenceFuel Cell Seminar 2006 Conference
Land/OmrådeUSA
ByHonolulu, Hawaii
Periode13/11/200617/11/2006

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