Electricity: battery or capacitor charging or discharging – Wind – solar – thermal – or fuel-cell source
Reexamination Certificate
2001-02-08
2003-01-07
Toatley, Jr., Gregory J. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Wind, solar, thermal, or fuel-cell source
Reexamination Certificate
active
06504339
ABSTRACT:
BACKGROUND
The invention generally relates to a technique to control the charging of a battery using a fuel cell.
A fuel cell is an electrochemical device that converts chemical energy produced by a reaction directly into electrical energy. For example, one type of fuel cell includes a polymer electrolyte membrane (PEM), often called a proton exchange membrane, that permits only protons to pass between an anode and a cathode of the fuel cell. At the anode, diatomic hydrogen (a fuel) is reacted to produce hydrogen protons that pass through the PEM. The electrons produced by this reaction travel through circuitry that is external to the fuel cell to form an electrical current. At the cathode, oxygen is reduced and reacts with the hydrogen protons to form water. The anodic and cathodic reactions are described by the following equations:
H
2
→2H
+
+2e
−
at the anode of the cell, and Equation 1
O
2
+4H
+
+4e
−
→2H
2
O at the cathode of the cell. Equation 2
A typical fuel cell has a terminal voltage near one volt DC. For purposes of producing much larger voltages, several fuel cells may be assembled together to form an arrangement called a fuel cell stack, an arrangement in which the fuel cells are electrically coupled together in series to form a larger DC voltage (a voltage near 100 volts DC, for example) and to provide more power.
The fuel cell stack may include flow plates (graphite composite or metal plates, as examples) that are stacked one on top of the other, and each plate may be associated with more than one fuel cell of the stack. The plates may include various surface flow channels and orifices to, as examples, route the reactants and products through the fuel cell stack. Several PEMs (each one being associated with a particular fuel cell) may be dispersed throughout the stack between the anodes and cathodes of the different fuel cells. Electrically conductive gas diffusion layers (GDLs) may be located on each side of each PEM to form the anode and cathodes of each fuel cell. In this manner, reactant gases from each side of the PEM may leave the flow channels and diffuse through the GDLs to reach the PEM.
A fuel cell system may include a fuel processor that converts a hydrocarbon (natural gas or propane, as examples) into a fuel flow for the fuel cell stack. For a given output power of the fuel cell stack, the fuel flow to the stack must satisfy the appropriate stoichiometric ratios governed by the equations listed above. Thus, a controller of the fuel cell system may determine the appropriate output power from the stack and based on this determination, estimate the fuel flow to satisfy the appropriate stoichiometric ratios. In this manner, the controller regulates the fuel processor to produce this flow, and in response to controller determining that the output power should change, the controller estimates a new rate of fuel flow and controls the fuel processor accordingly.
The fuel cell system may provide power to an external load, such as a load that is formed from residential appliances and electrical devices that may be selectively turned on and off to vary the power that is consumed by the load. Thus, the power that is consumed by the load may not be constant, but rather, the power that is consumed by the load may vary over time and abruptly change in steps. For example, if the fuel cell system provides power to a house, different appliances/electrical devices of the house may be turned on and off at different times to cause the power that is consumed by the load to vary in a stepwise fashion over time.
The fuel cell system may include a battery to temporarily supplement the power that the fuel cell stack provides to the load during times when the fuel processor does not provide a sufficient level of fuel to the stack to maintain the above-described stoichiometric equations. The battery may frequently need to be charged. However, the battery may need to be charged during times when the fuel cell stack is already providing the maximum amount of power that is possible with a given level of fuel flow from the fuel processor.
Thus, there is a continuing need for an arrangement and/or technique to address one or more of the problems that are stated above.
SUMMARY
In an embodiment of the invention, a technique that is usable with a fuel cell stack includes providing a fuel flow and using at least some of the fuel flow to produce power with the fuel cell stack. A request is received to charge a battery. In response to the request, the technique includes determining if the remainder of the fuel flow is sufficient to produce additional power to charge the battery. Based on the determination, the remainder of the fuel flow is used to produce the additional power to charge the battery.
Advantages and other features of the invention will become apparent from the following description, drawing and claims.
REFERENCES:
patent: 6215272 (2001-04-01), Ohara et al.
patent: 6322917 (2001-11-01), Acker
Hardwicke Edward
Hoehn, Jr. James G.
Parks John
Skidmore Dustan
Plug Power Inc.
Tibbits Pia
Trop Pruner & Hu P.C.
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