Besides producing and storing fuel, the station 10 also generates electricity for a load 40 (a residential load (i.e., the electrical loads of a house) or the load presented by a commercial re-fueling station, as examples). In this regard, during peak pricing times or times when grid electricity is not available, the fuel cell-based power generator 30 of the station 10 uses fuel from the fuel storage tank for purposes of generating electricity for the load 40.
For purposes of maximizing the overall efficiency of the station 10 and minimizing emissions (such as carbon dioxide emissions, for example), the efficiencies of the fuel generator 12 and the fuel cell-based power generator 30 are of paramount importance. Although many possibilities may exist to raise the efficiency of the fuel cell-based power generator 30, one technique to raise the efficiency of the generator 30 is to increase the partial pressure of the reactant oxygen that is supplied to the generator 30. In this regard, the fuel cell-based power generator 30 produces electricity in response to an incoming fuel flow (received at its anode inlet 22) and an incoming oxidant flow (received at its cathode inlet 26).
For purposes of providing the oxidant flow to the fuel cell-based power generator 30, the station 10 includes an oxidant source 50. As described further below, the oxidant source 50 includes a thermal swing adsorber (TSA) 56 that enriches the oxidant flow to the fuel cell-based power generator 30 with oxygen.
More specifically, the oxidant source 50 includes, in accordance with some embodiments of the invention, an air blower 52 (a positive displacement type or centrifugal type blower, as examples) that, during the operation of the fuel cell-based power generator 30, furnishes a flow of air to the TSA 56 which enriches the flow with oxygen. The flow exits the TSA 56 and is routed to the cathode inlet 26 of the fuel cell-based power generator 30.
It is noted that the oxygen partial pressure from the flow that exits the air blower 52 may be near an atmospheric ambient partial pressure. Therefore, the efficiency of the fuel cell-based power generator 30 is not significantly enhanced by use of the air blower 52 alone. Although the air blower 52 may be replaced with another air source, such as a compressed air source, in lieu of the TSA 56, the efficiency of the station may not be increased, due to the electrical power consumption by the compressor.
The TSA 56 contains at least one fixed bed that enriches the incoming air flow with oxygen to produce the outgoing enriched oxidant flow. In accordance with some embodiments of the invention, the bed of the TSA 56 enriches the oxidant flow by capturing nitrogen from the incoming air stream when the bed is cold. However, regularly, the bed must be regenerated to release the captured nitrogen. This involves cycling the thermal state of the TSA 56 and subjecting its bed to a purge flow. More specifically, in accordance with some embodiments of the invention, the bed of the TSA 56 may be expected to be regenerated every one quarter or half a twenty four hour period of a given day. For purposes of performing this regeneration, the station 10 routes an exhaust flow from the fuel generator 12 through the TSA 56, in accordance with some embodiments of the invention.
More particularly, in accordance with some embodiments of the invention, the fuel generator 12 and the fuel cell-based power generator 30 do not operate simultaneously. Rather, the fuel generator 12 and the fuel cell-based power generator 30 operate pursuant to mutually exclusive schedules so that the fuel generator 12 operates during off-peak pricing hours (for the incoming hydrocarbon flow and for grid electricity), while the fuel cell-based power generator 30 is shut down; and the fuel cell-based power generator 30 operates during peak pricing hours (from the fuel that is stored in the storage tank 14) while the fuel generator 12 is shut down.
Due to the above-described timing of the operating schedules of the fuel generator 12 and the fuel cell-based power generator 30, the station 10 uses the operation of the fuel generator 12 to regenerate the bed of the TSA 56 while the fuel cell-based power generator 30 is shut down and thus, not consuming oxygen. In this regard, during its operation, the fuel generator 12 produces a heated exhaust flow that is routed to the TSA 56 during the shut down state of the fuel cell-based power generator 30 for purposes of regenerating the bed of the TSA 56. During this regeneration, the flow from the TSA 56 is isolated from the fuel cell-based power generator 30. During the operation of the fuel cell-based power generator 30, the fuel generator 12 is shut down and isolated so that no exhaust flow flows to the TSA 56; and in the operational state of the fuel cell-based power generator 30, the cathode inlet 26 of the generator 30 receives the oxygen-enriched flow from the TSA 56.
The exhaust flow from the fuel generator 12 performs two functions with respect to regenerating the bed of the TSA 56: the flow transfers thermal energy to the bed of the TSA 56 for purposes of causing the bed to transition to a state in which the bed releases captured nitrogen; and the gas of the exhaust flow purges the released nitrogen from the bed.
The TSA's bed is not the only bed of the station 10 that may be regenerated in accordance with some embodiments of the invention. For example, in accordance with some embodiments of the invention, one or more fixed beds of a pressure swing adsorber (PSA) 80 of the station 10 may be regenerated in accordance with some embodiments of the invention. More specifically, the PSA 80 has at least one fixed bed that removes one or more components from the incoming hydrocarbon stream. For example, the PSA 80 may include one or more beds that remove water and carbon monoxide from the incoming hydrocarbon flow. The bed(s) of the PSA 80 need to be periodically regenerated to remove the trapped water and carbon monoxide; and, as further described below, in accordance with some embodiments of the invention, fuel that is stored in the fuel storage tank 14 is used to flow through the PSA 80 to regenerate the bed(s).
More specifically, for the case in which the fuel that is stored in the fuel storage tank 14 is purified and dry hydrogen; this hydrogen is routed to the PSA 80 to purge the bed(s) of the PSA 80. The regeneration occurs when the fuel generator 12 is shut down and the fuel cell-based power generator 30 is operational, in accordance with some embodiments of the invention. As further described below, the fuel flow that passes through the PSA 80 may be either an exhaust flow from the fuel cell-based power generator 30 or may be an incoming reactant flow to the fuel cell-based power generator 30, depending on the particular embodiment of the invention.
The station 10 includes various valves to control the above-described flows in connection with the fuel generation, power production and regeneration operations. For example, in accordance with some embodiments of the invention, a valve 60 is selectively opened and closed to regulate the flow from the TSA 56 to the cathode inlet 26 of the fuel cell-based power generator 30. Additionally, a valve 54 regulates the flow of air from the air blower 52 to the inlet of the TSA 56. Therefore, when the TSA 56 is being regenerated, the valves 54 and 60 may be closed for purposes of isolating the TSA 56 from the incoming air flow from the blower 52 and isolating the fuel cell-based power generator 30 from the purge flow.
For purposes of controlling the regenerating exhaust flow to the TSA 56, the station 10 includes a valve 70 that is located between an exhaust outlet of the fuel generator 12 and an inlet of the TSA 56. When the valve 70 is closed during the normal operation of the fuel cell-based power generator 30, the TSA 56 is isolated from the exhaust flow from the fuel generator 12. Similarly, a valve 72 that is connected to an outlet of the TSA 56 is closed. However, during the regeneration of the TSA 56, the valves 70 and 72 are open to route the exhaust flow through the TSA 56.
The station 10 also includes valves for purposes of controlling the regeneration of the PSA 80. More specifically, in accordance with some embodiments of the invention, a valve 82 is located between an outlet of the PSA 80 and an inlet 11 of the fuel generator 12. The valve 82 is open during the operation of the fuel generator 12 so that the fuel generator 12 receives the hydrocarbon flow from the PSA 80. However, during the regeneration of the PSA 80, the valve 82 is closed.
For embodiments of the invention in which fuel from the fuel storage tank 14 passes through the PSA 80 and then into the anode inlet 22 of the fuel cell-based power generator 30 during the regeneration of the bed(s) of the PSA 80, the station 10 includes a three-way valve 20 and a valve 71. The three-way valve 20 controls communication between an outlet of the fuel storage tank 14, an inlet of the PSA 80 and the anode inlet 22 of the fuel cell-based power generator 30. More specifically, during operation of the fuel cell-based power generator 30, the valve 20 is configured to establish communication between the outlet of the fuel storage tank 14 and the anode inlet 22 so that a blower 19 (connected to the outlet of the fuel storage tank 14) establishes a flow of fuel into the anode inlet 22. However, during the regeneration of the PSA 80, the valve 20 is configured to establish communication between the outlet of the fuel storage tank 14 and an inlet of the PSA 80. Thus, purified and dry hydrogen (for example) flows from the fuel storage 14 and through the PSA 80.
An open valve 71 (which is normally closed when the PSA 80 is not being regenerated) communicates the flow from the PSA 80 to the anode inlet 22. Thus, in this configuration, purified and dry hydrogen flows from the fuel storage tank 14 through the bed(s) of the PSA 80 and enters the fuel cell-based power generator 30. As noted above, the flow through the PSA 80 may also be directed to the cathode inlet 26 of the fuel cell-based power generator 30; and additionally, an exhaust flow of the fuel cell-based power generator 30 may be used to regenerate the bed(s) of the PSA 80 in accordance with other embodiments of the invention.
Among the other features of the station 10, in accordance with some embodiments of the invention, the station 10 includes a controller 90 (one or more microprocessors and/or microcontrollers, as examples) to coordinate the above-described operations of the station 10. In this regard, the controller 90 may control the operating schedules of the fuel generator 12 and fuel cell-based power generator 30, control the operations of the various valves, control the motors and pumps of the station 10, etc., depending on the particular embodiment of the invention. Thus, the controller 90, various conduits and the above-described valves form at least part of a control subsystem for purposes of controlling operation of the fuel generator 12, operation of the fuel cell-based power generator 30 and regeneration of the beds of the PSA 80 and TSA 56. The controller 90 includes various input terminals 92 that receives status signals, messages, commands, indications of sensed values, etc., from the station 10 and possibly other entities; and includes output terminals 94 for purposes of controlling valves, motors, communicating messages and commands to the station 10 and other entities, etc., depending on the particular embodiment of the invention.
To summarize,
Pursuant to the technique 150, the controller 90 determines (diamond 152) whether the fuel cell-based power generator 30 is shut down. If so, then the controller 90 determines (diamond 154) whether the fuel generator 12 is on, or operating. If the fuel generator 12 is operating, then the controller 90 causes the exhaust flow from the fuel generator 12 to be routed through the bed of the TSA 56. For example, pursuant to block 156, the controller 90 may open the valves 70 and 72. After the controller 90 determines (diamond 158) that the TSA bed has been regenerated, then the controller 90 isolates (block 160) the exhaust flow from the fuel generator 12 from the TSA 56. Thus, pursuant to block 160, the controller 90 may close the valves 70 and 72 (
In accordance with other embodiments of the invention, the TSA 56 may enrich the oxygen flow to the fuel cell-based power generator 30 by using an alternative adsorption bed in which the bed captures oxygen when cold and releases oxygen when hot. Therefore, during the normal operation of the fuel cell-based power generator 30, the bed of the TSA 56 must remain relatively hot; and when the fuel cell-based power generator 30 is shut down, a relatively cold flow is routed through the TSA 56 for purposes of regenerating its bed. For these embodiments of the invention, the fuel generator 12 and the fuel cell-based power generator 30 may be operating concurrently in that the exhaust flow from the fuel generator 12 is routed through the TSA 56 for purposes of causing its bed to release oxygen.
Referring to
In general, the station 10 may use a technique 250, which is depicted in
Referring to
The reactant inlet of the fuel cell-based power generator 30, which receives the flow from the PSA 80 during its regeneration may either be the anode inlet 22 or the cathode inlet 26, depending on the particular embodiment of the invention. In the case of a PSA that removes only water, the flow from the PSA 80 may be routed to the anode inlet 22 for such cases as when the membranes of the fuel cells of the fuel cell-based power generator 30 uses a low temperature Nafion PEM membrane. Next, the controller 90 isolates (block 316) the PSA 80 from the fuel cell-based power generator 30 and configures the PSA 80 to operate with the fuel generator 12. Thus, pursuant to block 316, the controller 90 may configure the valve 20 (see
It is noted that the reactant inlet of the fuel cell-based power generator 30, which receives the flow from the PSA 80 during its regeneration may either be the anode inlet 22 or the cathode inlet 26, depending on the particular embodiment of the invention. In the case of a PSA that removes only water, the flow from the PSA 80 may be routed to the anode inlet 22 for such cases as when the membranes of the fuel cells of the fuel cell-based power generator 30 uses a low temperature Nafion PEM membrane. In the case of a PSA that removes water and carbon monoxide, the flow from the PSA 80 may be routed to the anode inlet 22 if a PBI membrane is used in the fuel cells of the generator 30. Additionally, if a humidity transfer device such as an enthalpy wheel or membrane humidifier is used, the water from the PSA may be transferred to the cathode inlet 26 to perform stack humidification.
In other embodiments of the invention, the controller 90 may perform a technique 350 that is depicted in
The cathode inlet 404 of the fuel cell stack 400 is in communication with the cathode inlet 26 (see
In accordance with some embodiments of the invention, the anode exhaust from the fuel cell stack 400 may be routed to an oxidizer 412, an oxidizer that may be part of the fuel generator 12 in accordance with some embodiments of the invention. Additionally, although
Among the other features of the fuel cell-based power generator 30, in accordance with some embodiments of the invention, the generator 30 includes a temperature regulation subsystem 420 that may, for example, circulate a coolant through the fuel cell stack 400 for purposes of regulating the stack temperature. Additionally, the fuel cell-based power generator 30 may include power conditioning circuitry 430 that is in communication with DC stack terminals 424 for purposes of conditioning the power received from the fuel cell stack 400 into the appropriate form (AC or DC) and level for the load 40 (see
In addition to the reformer 450 and the purifier 460, the fuel generator 12 includes a compressor 470 and a valve 472. In this regard, during operation of the fuel generator 12, the valve 472 is open and the compressor 470 operates to store pressurized gas in the fuel storage tank 14 (see
While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.