Control of fuel cell power plant

#This invention relates to start-up of a fuel cell power plant at below freezing point.

#A fuel cell power plant is provided with a fuel cell stack that is a laminated body of plural fuel cells. The fuel cell uses a membrane electrolyte to generate power from electrochemical reactions mediated by hydrogen (H2) supplied to an anode and oxygen (O2) supplied to a cathode.

#In this fuel cell, the membrane electrolyte must be normally maintained in a humidified state in order to promote preferred electrochemical reactions. For this purpose, the oxygen and hydrogen supplied to the fuel cell stack are humidified in advance using water. Consequently when starting the power plant, it is necessary to warm up water used for humidifying operations in order to transform the water into a state for humidification, in other words, to transform the water into steam.

#FIG. 1 is a schematic diagram of a fuel cell power plant according to this invention.

#FIG. 2 is a flowchart showing a start-up control routine for a power plant executed by a controller according to this invention.

#FIG. 3 is a diagram showing the relationship between energy consumed and water temperature during start-up of the power plant.

#Referring to FIG. 1 of the drawings, a fuel cell power plant for driving a vehicle according to this invention is provided with a fuel cell stack 11 comprising a plurality of laminated fuel cells, a hydrogen supply unit 2 supplying hydrogen through a hydrogen supply passage 5 to an anode of the fuel cell stack 11 and an air supply unit 3 supplying oxygen in the form of air through an air supply passage 6 to a cathode of the fuel cell stack 11. The power generated in the fuel cell stack 11 is supplied through electrical wiring to a load such as an electric motor (not shown).

#The hydrogen supply unit 2 may be either a type which supplies hydrogen or a type which supplies a hydrogen-rich gas obtained by reforming gasoline or methanol in a reformer. The air supply unit 3 comprises an air compressor or the like.

#Electric power is generated between the electrodes by the reaction below between oxygen supplied to the cathode and hydrogen supplied to the anode. The reaction in the cathode below is an exothermic reaction.