Micro fuel cell system start up and shut down systems and methods
Described herein are fuel cell systems and methods of using fuel cell systems. The systems include a fuel cell that generates electrical energy using hydrogen and a fuel processor that produces hydrogen from a fuel source. The fuel processor includes a reformer and a burner that heats the reformer. One heat efficient fuel cell system described herein heats internal portions of a fuel cell using a heating medium from a fuel processor. The heating medium may comprise gases exhausted at high temperatures from the fuel processor, which are then transported to the fuel cell. The heating medium may also include a gas that reacts catalytically in the fuel cell to produce heat. Systems and methods for expediting fuel cell system start up are provided. Methods for shutting down a fuel cell system are also described that reduce the amount of moisture and gases in the reformer and in one or more fuel cell components. One hydrogen efficient fuel cell system described herein transports hydrogen to an inlet of a burner. The hydrogen may comprise unused hydrogen from a fuel cell and/or hydrogen produced in a reformer. The burner comprises a catalyst that facilitates production of heat in the presence of the hydrogen.
1 . A method for starting a fuel processor including a reformer and a burner that provides heat to the reformer, the method comprising:
generating heat using an electrical heater that is configured to heat the burner or a fuel source provided to the burner;
supplying the fuel source to the burner;
catalytically generating heat in the burner to heat the reformer;
supplying the fuel source to the reformer; and
generating hydrogen in the reformer.
2 . The method of claim 1 wherein the heat is generated by the electrical heater for at least 50 milliseconds before the fuel source is supplied to the burner.
3 . The method of claim 1 wherein the heat is generated by the electrical heater until the burner reaches a threshold start temperature.
4 . The method of claim 1 further comprising mixing air with the fuel source before the fuel source reaches the electrical heater.
5 . The method of claim 4 wherein the electrical heater heats the air and the fuel source before the air and the fuel source enters the burner.
6 . The method of claim 1 further comprising turning off the electrical heater after the fuel source is supplied to the burner.
7 . The method of claim 1 further comprising providing hydrogen from the reformer to the burner.
8 . The method of claim 1 further comprising catalytically generating heat in the burner using the hydrogen.
9 . The method of claim 1 further comprising recharging a capacitor or battery that powers the electrical heater using electrical energy provided by a fuel cell that receives hydrogen from the reformer.
10 . The method of claim 1 wherein the electrical heater vaporizes the fuel source.
11 . The method of claim 1 wherein the fuel source comprises methanol.
12 . A system for heating a fuel source before catalytic heat generation within a burner included in a fuel processor, the system comprising:
a reformer configured to receive the fuel source, configured to output hydrogen, and including a catalyst that facilitates the production of hydrogen;
a burner configured to provide heat to the reformer; and
an electric heater configured to heat the burner or the fuel source provided to the burner.
13 . The system of claim 12 further comprising a capacitor or battery that is recharged by the fuel cell and that powers the electrical heater.
14 . The system of claim 12 wherein the electric heater is disposed in the burner.
15 . The system of claim 12 wherein air mixes with the fuel source before the fuel source reaches the burner.
16 . The system of claim 15 wherein the electric heater is disposed outside the burner.
17 . The system of claim 12 further comprising a catalyst disposed on an outside surface of the electric heater that facilitates the generation of heat in the presence of the fuel source.
18 . The system of claim 12 further comprising a boiler configured to heat the fuel source before the reformer receives the fuel source.
19 . The system of claim 12 wherein the reformer comprises a reformer chamber having a volume greater than about 0.1 cubic centimeters and less than about 50 cubic centimeters.
20 . A method for shutting down a fuel cell system comprising a fuel cell that received hydrogen from a fuel processor including a reformer and a burner that provided heat to the reformer, the method comprising:
stopping electrical energy generation in the fuel cell;
discontinuing a supply of a fuel source to the reformer, which is configured to receive the fuel source and output hydrogen;
generating heat in the burner to heat to the reformer after discontinuing the supply of the fuel source to the reformer;
discontinuing heat generation in the burner; and
flushing the burner with air.
21 . The method of claim 20 further comprising discontinuing hydrogen supply to the fuel cell.
22 . The method of claim 21 further comprising providing air to a cathode gas distribution system in the fuel cell after the discontinuing hydrogen supply to the fuel cell.
23 . The method of claim 20 further comprising cooling the fuel cell.
24 . The method of claim 23 wherein cooling the fuel cell comprises turning on a fan that moves air through the fuel cell.
25 . The method of claim 24 wherein the air moves across a heat transfer appendage included in the fuel cell, wherein the heat transfer appendage a) includes a portion arranged external to a fuel cell stack included in the fuel cell and b) is in conductive thermal communication with an internal portion of the fuel cell stack
26 . The method of claim 20 wherein heat is generated in the burner to heat to the reformer until for greater than about 30 seconds after discontinuing the supply of the fuel source to the reformer.
27 . The method of claim 20 wherein the burner includes an inlet to receive the fuel source from a second supply of the fuel source and the burner catalytically generates heat using the fuel source.
28 . The method of claim 27 wherein discontinuing heat generation in the burner comprises discontinuing the second supply of the fuel source.
29 . A fuel cell system for producing electrical energy, the fuel cell system comprising:
a fuel processor that includes
a reformer configured to receive a fuel source, configured to output hydrogen, and including a catalyst that facilitates the production of hydrogen;
a burner configured to provide heat to the reformer; and
a fuel cell including a fuel cell stack configured to produce electrical energy using hydrogen output by the fuel processor, and including a heat transfer appendage that a) includes a portion arranged external to the fuel cell stack and b) is in conductive thermal communication with an internal portion of the fuel cell stack; and
control logic configured to regulate heat transfer or temperature for one or more components within the fuel cell system.
30 . The system of claim 29 wherein the control logic is further configured to generate heat in the burner to heat to the reformer after discontinuing the supply of the fuel source to the reformer.
31 . The system of claim 30 wherein the control logic is further configured to discontinue heat generation in the burner.
32 . The system of claim 31 wherein the control logic is further configured to flush the burner with air.