ENERGY MANAGEMENT OF FUEL CELL SYSTEM AND SUPERCAPS ELEMENTS S.Caux, J.Lachaize, M.Fadel,

The use of Fuel Cell and Supercaps as energy elements in transport application is now a reality. Having two power sources on board allows a certain energy management strategy. Defining this strategy some iteration must be made with an accurate model to extract the optimal solution. In order to reduce computation time consumption, a simplified physical fuel cell model is proposed. This model is used in algorithms to compute the two power references of the two sources allowing the minimum hydrogen consumption and maximum braking energy absorption for a tramway following an actual power demand. Copyright © 2005 IFAC Keywords—Circuit Model – Power management Optimisation constitute the based-cell. With serial and parallel connections a more powerful fuel cell is build to have the fuel cell needed in transport application (tramway in this study described in Lachaize2003). The chemical to electrical behavior starts to be well known for PEMFC and complex model can be found in: Amphlett(1995) and Alstom-CEA-LEEI(2002). The FC voltage Ufc, depends on the current in the fuel cell I, the partial pressures (of hydrogen PH2 and oxygen PO2), the temperature of the reaction Tfc, and the hydration of the membrane λH2O. ) , , , , ( 0 2 2 2 H fc T PH PO I f Ufc λ = (1) Assumptions: Non significant Anode activation voltage Uniform current density and temperature. The voltage variations of the fuel cell are computed with a quasi-static model, because the dynamics of the chemical reactions is faster than the system dynamics. The output voltage expression is: j R E Ufc m act rev ⋅ − + = η (2) Where, the reversible voltage Erev is: ( )       + ⋅ ⋅ ⋅ + − ⋅ + = 2 2 ln ln 2 1 15 . 298 3 2 1 H O fc fc rev P P T T E α α α The cathode activation over voltage ηact is: 2 ln ) 10 . 5 ln( 4 3 3 2 1 O fc fc act c T j T T ⋅ ⋅ + ⋅ ⋅ + ⋅ + = − β β β β η Where cO2 the concentration of dissolved oxygen, can be defined by henry’s law (mol/m) according to:         − ⋅ ⋅ =