Background Of The Invention [0002] There are several instances where an uninterrupted power supply (UPS) is desirable or needed, for example for use with electrical or electronic equipment (load) that has to be working regardless of whether the power grid (utility power, mains grid etc. ) is available. Traditionally, large capacity UPS systems have incorporated batteries complemented by an internal combustion (IC) engine powered generator. Once the power grid electricity is interrupted, for whatever reason, the UPS regulation device re- routes power to come from the batteries, and the IC engine is started and heated up to operating temperature. When this temperature is reached, the generator is used by the regulation device to charge the batteries and to supply the necessary electrical energy to the load. Apparent drawbacks of this type of UPS system are the pollution generated by the IC engine, typically a diesel engine, including air pollution and noise pollution, the dependence on non-renewable fuels and the limited operation time caused by the storage space requirements of this fuel.

[0003] Fuel cells have been proposed as a clean, efficient and environmentally friendly power source that has various applications. A conventional proton exchange membrane (PEM) fuel cell is typically comprised of an anode, a cathode, and a selective electrolytic membrane disposed between the two electrodes. A fuel cell generates electricity by bringing a fuel gas (typically hydrogen) and an oxidant gas (typically oxygen) respectively to the anode and the cathode. In reaction, a fuel such as hydrogen is oxidized at the anode to form cations (protons) and electrons by

the reaction H2 = 2H+ + 2e-. The proton exchange membrane facilitates the migration of protons from the anode to the cathode while preventing the electrons from passing through the membrane. As a result, the electrons are forced to flow through an external circuit thus providing an electrical current.

At the cathode, oxygen reacts with electrons returned from the electrical circuit to form anions. The anions formed at the cathode react with the protons that have crossed the membrane to form liquid water as the reaction by- product following _02 + 2H+ + 2e-= H20. On the other hand, an electrolyser uses electricity to electrolyze water to generate oxygen from its anode and hydrogen from its cathode. Similar to a fuel cell, a typical solid polymer water electrolyser (SPWE) or proton exchange membrane (PEM) electrolyser is also comprised of an anode, a cathode and a proton exchange membrane disposed between the two electrodes. Water is introduced to, for example, the anode of the electrolyser which is connected to the positive pole of a suitable direct current voltage. Oxygen is produced at the anode by the reaction H20 = _02 + 2H+ + 2e-. The protons then migrate from the anode to the cathode through the membrane. On the cathode which is connected to the negative pole of the direct current voltage, the protons conducted through the membrane are reduced to hydrogen following 2H+ + 2e-= H2.

[0004] It is well known in the art that one type of regenerative fuel cell system combines separated fuel cell and electrolyser units so that during the fuel cell mode of the system, the fuel cell unit generates electricity while consuming fuel gas (typically hydrogen) and oxidant (typically oxygen or air) and during the electrolyser mode of the system, the electrolyser unit generates the two process gases for consumption by the fuel cell unit, i. e. oxygen and hydrogen, while consuming electricity. Individual fuel cell and electrolyser cells are usually interconnected in a series arrangement, often called"stacks".

[0005] US Patents No. 5,376, 470 entitled"Regenerative Fuel Cell System"and No. 5,506, 066 entitled"Ultra-Passive Variable Pressure Regenerative Fuel Cell System", both issued to Rockwell International

Corporation, disclose such a regenerative fuel cell system. The regenerative fuel cell system comprises a fuel cell including an anode for receiving hydrogen and a cathode for receiving oxygen, an electrolyser for electrolyzing water to produce pure hydrogen and pure oxygen, storage tanks to respectively store hydrogen and oxygen. from the electrolyser, a water storage tank communicating with the fuel cell and the electrolyser. The fuel cell is located above the water storage tank while the electrolyser is located below the water storage tank. Hydrogen is supplied to the fuel cell during fuel cell mode or extracted from the cathode side of the electrolyser during electrolyser mode via a hydrogen line that is connected to the hydrogen storage tank and through a liquid-gas separator. Similarly, oxygen is supplied to the fuel cell via lines and through the water storage tank during fuel cell mode or extracted from the anode side of the electrolyser via an oxygen line and through the water storage tank. The oxygen, when reaching the water storage tank, bubbles up to the fuel cell via a supply line during fuel cell mode or to the oxygen storage tank, when in the electrolyser mode.

[0006] A conventional regenerative fuel cell system, for example, as disclosed in U. S. Patent 5,376, 470 is shown in Figure 1. The regenerative fuel cell system 110 comprises a fuel cell 112 including an anode for receiving hydrogen and a cathode for receiving oxygen, an electrolyser 116 for electrolyzing water to produce pure hydrogen and pure oxygen, storage tanks 124,126 to respectively store hydrogen and oxygen, and water storage tank 114 communicating with said fuel cell 112 and the electrolyser 116. The fuel cell 112 is located above the water storage tank 114 while the electrolyser 116 is located below the water storage tank 114; the actual location of these items can of course vary. Hydrogen is supplied to the fuel cell 112 during fuel cell mode or extracted from the cathode side of the electrolyser 116 during electrolyser mode via a hydrogen line 128 that is connected to the hydrogen storage tank 124 and through a liquid-gas separator 122. A flow valve 122 and a secondary water storage tank 118 are provided, for humidifying the hydrogen stream. Similarly, oxygen is supplied to the fuel cell 112 via lines 130 and 115 and through the water storage tank 114 during fuel cell mode or

extracted from the anode side of the electrolyser 116 via oxygen line 130 and 117 and through the water storage tank 114. In the electrolyser mode, the oxygen generated flows up to the water storage tank 114 and then bubbles up to the fuel cell via line 115 if the fuel cell is in the fuel cell mode or to oxygen storage means 126 via line 130 if the fuel cell is not operating.

[0007] However, these regenerative fuel cell systems cannot meet the increasingly demanding requirements for fuel cell stacks. The systems are usually large in size and heavy in weight and require complex plumbing and ancillary equipment such as valves and controls. As is known in the art, the performance of the fuel cell unit in this system cannot be optimized unless an additional humidification device is provided to humidify the process gases and an additional heat exchanger is included to facilitate the heat dissipation, all of which results in increased system size and weight. When switching from electrolyser mode to fuel cell mode, the fuel cell unit in the conventional regenerative fuel cell systems is cold and therefore is unable to achieve full power output until the stack is warm.

[0008] Moreover, at present there is an expanding interest in vehicular applications of fuel cell stacks, e. g. as the basic power source for cars, buses and even larger vehicles. Vehicular applications are quite different from many stationary applications. In stationary applications, fuel cell stacks are usually used as an electrical power source and are simply expected to run at a relatively constant power level for an extended period of time. In contrast, in a vehicular, particularly an automotive environment, the actual power required from the fuel cell stack can vary significantly. Moreover, the fuel cell stack is expected to respond rapidly to changes in power demand while maintaining high efficiencies. Further, for vehicular, particularly automotive applications, a fuel cell power unit is expected to operate under a disparate range of ambient temperature and humidity conditions. In addition, during regenerative braking period, the prior regenerative fuel cell systems are unable to capture the electricity to recharge the system due to their slow switchover times, making them less efficient. All these requirements are exceedingly demanding and

make it difficult to incorporate a conventional regenerative fuel cell system into a vehicle and operate efficiently.

[0009] In view of the disadvantages and drawbacks associated with conventional UPS systems, it is desirable to provide a UPS system utilizing a regenerative fuel cell system that enables improved fuel cell performance, including rapid switchover between fuel cell and electrolyser modes, substantially instantaneous full power operation, higher power density, less peripherals and hence higher system efficiency.

Summary Of The Invention [0010] In accordance with an aspect of the invention, there is provided a method of providing back-up electrical power for an external load connected to an external source of electricity during normal operation. The method comprises (a) initiating a generation mode by disconnecting the external load from the external source of electricity, and in a start-up submode of the generation mode, supplying electricity from an electrical storage module to the external load ; (b) during the start-up submode, starting up a fuel cell power module; (c) switching from the start-up submode to a normal operation submode of the generation mode; and, (d) supplying electricity from the fuel cell power module to the external load during the normal operation submode.

[0011] In accordance with a second aspect of the invention, there is provided an electrical power supply system for providing back-up electrical power for an external load connected to an external source of electricity during normal operation. The system comprises (a) a plurality of operating modules including (i) a fuel cell power module for generating electrical power; (ii) a fuel storage module for storing fuel for supply to the fuel cell power module; and (iii) an electrical storage module for storing electricity; and, (b) a control module for switching the plurality of operating modules between a plurality of operating modes and for connecting and disconnecting the external load from the grid, wherein the plurality of operating modes includes a generation mode for supplying electricity to the external load when the external load is disconnected from the external source of electricity, and the

generation mode comprises (i) a start-up submode for supplying electricity from the electrical storage medium to the external load ; and (ii) a normal operation submode for supplying electricity from the fuel cell power module to the external load.

Brief Description Of The Drawings [0012] For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made to the accompanying drawings which show, by way of example, preferred embodiments of the present invention, and in which; [0013] Figure 1 is a schematic view, which illustrates a conventional regenerative fuel cell system according to Prior Art; [0014] Figure 2 is a schematic view of an uninterrupted power supply apparatus (UPS) according to an aspect of the present invention; [0015] Figure 3 is a schematic view, which illustrates how the UPS of Figure 2 is connected to a power grid (in this case the load is a cellular telephone station); [0016] Figure 4 is a further schematic view, which illustrates how the UPS of Figure 2 is connected to a power grid (in this case the load is a cellular telephone station); [0017] Figures 5A and 5B are diagrams showing the power draw of the UPS of Figure 2 during testing; [0018] Figure 6 is a diagram showing the hydrogen discharge of the UPS of Figure 2 during testing; [0019] Figure 7 is a diagram showing the hydrogen generation of the UPS of Figure 2 during testing; [0020] Figures 8A and 8B are diagrams showing the quality of the supplied voltage and voltage THD of the UPS of Figure 2 during testing; [0021] Figure 9 is a diagram showing the transient response of the UPS of Figure 2 during testing;

[0022] Figure 10 is a diagram showing the accumulated run time of the UPS of Figure 2 during testing; [0023] Figure 11 is a diagram showing the process steps of the UPS of Figure 2 during stand by mode; [0024] Figure 12 is a diagram showing the process steps of the UPS of Figure 2 during electric power generation mode; [0025] Figure 13 is a diagram showing the process steps of the UPS of Figure 2 during hydrogen generation mode; [0026] Figure 14 is a diagram showing the process steps of the UPS of Figure 2 during emergency stop recovery mode; [0027] Figure 15 is a diagram showing the process steps of the UPS of Figure 2 during mode change sequence check mode; and [0028] Figure 16 is a diagram showing the process steps of the UPS of Figure 2 during off mode.

Detailed Description Of The Invention [0029] In the following description, for the purpose of illustration, fuel cells are described by taking PEM fuel cells as an example, and likewise, the process gases discussed hereinafter are limited to pure hydrogen and air.

However, it should be appreciated that the fuel cell in the present invention is not limited to PEM fuel cells and the process gases can be different; for example it is common to use air as a source of an oxidant gas.

[0030] A fuel cell power module (FCPM)/electrolyser HyUPSTM system 220 (referred to as HyUPSTM system 220) according to an aspect of the invention comprises the following different modules : a fuel cell power module (FCPM) 222, an electrolyser re-fuelling module (ERM) shown as electrolyser module 224 in Figures 2 and 3, a hydrogen storage module (HSM) shown as fuel storage module 226 in Figure 2 and as H2 storage module in Figure 3, a power conditioning module (PCM) shown as power electronics module 228 in Figures 2 and 3, and a control and instrumentation module (CIM) shown as

overall systems controller 230 in Figure 2. In one embodiment, the HyUPSTM 220 contains a 19 kW gross fuel cell power module (FCPM) 222, a 3 kW electrolyser re-fueling module (ERM) 224,50 kWh hydrogen storage module (HSM) 226 with metal hydride storage, a power conditioning module (PCM) 228and a control and interface module (CIM) 230. The FCPM 222 converts hydrogen and air (oxygen) into electrical power and heat. In a first phase of operation, the HyUPS system 220 powers the AC heating, ventilation and air conditioning ("HVAC") load 238 when the grid fails. During a second phase of operation the HyUPSTM system 220 powers the whole site when the power fails. When grid power is available, the HyUPSTM system 220 restores itself by recharging its batteries and by using its integral electrolyser 224 to refill the metal hydride storage with hydrogen. Periodic remote (or timed) start-up of the HyUPSTM system 220 will test the functionality and robustness of the unit in an accelerated manner.

The Fuel Cell Power Module 222 [0031] The fuel cell power module 222 is preferably self-contained in that all the components such as the stack, the balance of plant (BOP) and the controls are housed as a module in an enclosure or framework. A Proton Exchange Membrane type of fuel cell stack is used as the preferred fuel cell type, but other types may also be used as long as they can operate with a minimum of extraneous equipment. The specifications of the system are generally as follows.

[0032] The FCPM 222 interfaces the following other modules: FCPM Interface Interacting Module Hydrogen Gas Supply Hydrogen Storage Module (HSM) 226 Thermal Heat Rejection Ambient (AMB) Air Supply Ambient (AMB) Electrical Power Output Power Conditioning Module (PCM) 228 Ancillary Power Supply Power Conditioning Module (PCM) 228 Non Combustible Exhaust Ambient (AMB) DI-Water Supply Electrolyser Refueling Module (ERM) 228 Physical Interface FCPM/HSM/AMB/ERM/CIM FCPM Controller Control and Instrumentation Module (CIM) 230

[0033] Possible interface requirements for the FCPM 222 that may be used are (note: the requirements will vary according to the actual application of the UPS system, these figures are examples of a working unit of a certain capacity): Hydrogen gas supplied at a pressure of approx. 220 kPaA (absolute), a temperature of 5 to 80 degrees C, comprising 99.997 % hydrogen, maximum flow rate 210 slpm (less than one second step response) and having less than 1 ppm CO contamination. Thermal heat rejection specifications are coolant in temperature maximum 80 degrees C, coolant out temperature 70 degrees C and airflow rate of approx. 10,000 sipm. Air supply (ambient air) at a pressure of between 95 and 103 kPaA, a temperature between 5 and 40 degrees C and a maximum flow rate of 1,000 sipm. Electric power output at a voltage range of 72 to 45 VDC, maximum current draw 425 A, gross electric power 19 kW and a load profile with the HVAC 238 turned on 3 to 5 min after power outage (load following not required). Ancillary power supply at a voltage 12,24 or 48 V as needed, current range as needed with a total electric power of 2 kW. Non-combustible exhaust at a pressure above 104 kPaA, a temperature below 45 degrees C, a composition of less than 2 % H2 and a maximum flow rate of 550 slpm dry gas plus 150 slpm water vapor.

De-lonized water stored at ambient pressure, temperature between 5 and 40 degrees C, above 3 M_ purity and at a flow rate of less than 1 Ipm (approx.

100 I storage). Physical dimensions (WxDxH) approx. 17"x25"x24", maximum weight 500 Ibs (including stack and battery). FCPM controller connected via

serial interface (or appropriate other interface depending upon the control system used).

[0034] In one embodiment, the FCPM 222 is rated for an electrical output of 1 ukw net (15 kW gross) at 0.62 volts per cell. The stack will typically have 75 cells for a nominal OCV of 50 volts, depending upon the cell type used. The active area of the membrane is typically 500 sq. cm per cell. The stack operates at near ambient pressure or up to a maximum of 130kPa. The stack control temperature is typically between 70-75 degrees C.

[0035] The FCPM 222 data, as well as the operating conditions, may be 75 cells (depending on desired output), dimensions (WxDxH) under 17"x9"x20", weight preferably less than 150 Ib, maximum electric power preferably 19 kW, stack voltage preferably 45 to 72 V and maximum current preferably 425 A.

[0036] For the the fuel cell power module 222, eight interfaces (fluid interfaces, electrical interfaces and physical interfaces) have been defined (again, the values that follow are only an example of possible values-these values may vary according to different variants of the invention): I) Cathode inlet fluid, pressure approx. 150 kPaA, temperature less than 80 degrees C, humidified ambient air with all water vaporized, 50 to 75 % relative humidity (RH) at coolant outlet temperature and a flow rate of double the stoichiometric flow rate (0 to 1,000 splm dry air plus the water vapor).

II) Anode inlet fluid, pressure approx. 150 kPaA, temperature less than 80 degrees C, humidified 99.997 % hydrogen with all water vaporized, 50 to 75 % relative humidity (RH) at coolant outlet temperature and a flow rate of 1.2 times the stoichiometric flow rate (0 to 210 splm dry hydrogen plus the water vapor).

III) Coolant inlet fluid, de-ionized water, pressure less than 50 kPa, temperature approx. 70 degrees C, flow rate 22 to 44 Ipm, conductivity less than 1 uS/cm and a pH of approx. 7.

IV) Cathode outlet fluid, pressure drop from inlet less than 10 kPa, temperature approx. 80 degrees C, humidified nitrogen-rich air at a flow rate of double the stoichiometric cathode flow rate (0 to 550 sipm dry gas and 0 to 150 sipm water vapor).

V) Anode outlet fluid, pressure drop from inlet less than 10 kPa, temperature approx. 80 degrees C, humidified hydrogen at a flow rate of 1.2 times the stoichiometric anode flow rate (0 to 25 slpm dry hydrogen plus water).

VI) Coolant outlet fluid, atmospheric pressure, temperature approx. 80 degrees C, de-ionized water, flow rate 22 to 44 Ipm, conductivity less than 1 uS/cm and a pH of approx. 7.

VII) Electrical interface, stack voltage 45 to 72 V, stack current 0 to 425 A, stack electric power output 0 to 19 kW and single cell voltages 0.6 to 1 V.

Vlil) Physical interfaces, dimension (WxDxH) less than 17"x25"x12"and weight less than 150 lb.

[0037] The fuel supplied to the FCPM 222 is hydrogen gas preferably supplied at better than 99.99% purity and at a minimum of 15 psig. The oxidant to the stack is taken from the atmospheric air. To attain the desired inlet pressure to the stack, a blower is employed. The blower preferably supplies air at a maximum flow of 600 slpm and pressure of 130 kPa.

[0038] Pressure control for the anode and cathode streams is for example achieved through the use of dome-loaded back pressure regulators, or other suitable types of pressure regulators. The feedback signal is the inlet pressures and typically employs pressure transducers with either a voltage or current output signal.

[0039] Humidification of the anode stream is for example provided through a bubbler style saturator (or possibly dry or a membrane/enthalpy plate humidifier) and the cathode stream advantageously employs an energy wheel for heat exchange/humidification.

[0040] The stack is cooled preferably using de-ionized (DI) water in a closed circulating loop. The DI quality is advantageously monitored using a conductivity sensor. A minimum of approx. 3 M_ resistivity is maintained. The dew-point temperatures are controlled by adding either water or a water-glycol solution. Radiators with integral fans are advantageously used to radiate heat to ambient exterior of the system.

[0041] Exhaust moisture from the stack is advantageously recovered to provide self-sustained operation or to keep the water top up requirement to a minimum level. Thus, the FCPM 222 will not require extra water and makes use of re-circulated fuel cell product water. The electrolyser system is maintained separately and its water is also recovered from the process using, for example, an enthalpy plate transfer of excess heat/moisture after the energy wheel to the anode inlet.

[0042] The FCPM 222 advantageously employs a dedicated embedded controller. The controller handles all required analog and digital l/O plus at least some data processing. Individual cell voltages are advantageously monitored through the use of a Differential Voltage Monitor module. This module communicates with the FCPM controller using, for example, a 115kBaud RS232C link. The link is advantageously opto-isolated. The storage media is, for example, a solid state disk and a means to retrieve diagnostic information is provided, either via download to an external computer, or via TCP/IP to an internet monitoring and control interface. The controller also has a communication link to the data display interface, so that operating information and conditions can be displayed onto a system LCD. All safety checks are performed through software and the status of the FCPM is made available to the other component controllers in the system. Transducers are typically of either the 0-5V, 1-5V or the 4-20mA type.

The Hydrogen Storage Module 226 [0043] The hydrogen fuel in the fuel storage module 226 is stored, for example, in metal hydride cylinders. Alternatively, the hydrogen fuel can be compressed, in some cases up to 10,000 psi, and stored in compressed gas

cylinders. In a preferred embodiment, three metal hydride cylinders are used, but the number and sizes can vary according to system output demands. The specifications are as follows.

[0044] The hydride bed used is advantageously a Mg-Mn-Ni, specifically AB5, alloy. The storage capacity is typically a minimum of 1.4% by weight of the hydride. The total storage capacity is typically 50kWhe, for example made up of three separate metal hydride vessels, each vessel capable of supplying a minimum of 40 slpm of H2 over the full operating range (15 degrees C-45 degrees C). The metal hydride is preferably stored in canisters having integral cooling/heating coils. The nominal storage pressure is typically 800kPa. The nominal operating pressure is typically 300 kPa. Each 10 kWhe metal hydride storage item weighs about 80 kg.

[0045] The charging pressure is typically 11OOkPa. Charging temperature is preferably maintained below 50 degrees C, to prevent hydride damage, by using an integral cooling fluid system and a radiator. The lower the temperature (even sub zero) the lower the charge pressure required and the faster the unit will charge. The charging rate is typically a maximum of 4 hours from empty to 100% full canisters (less than 1 hour is expected during normal operation).

[0046] The fuel storage module 226 preferably provides a minimum of 200 sipm of total hydrogen flow over the full operating temperature range (15 - 45 degrees C). The hydrogen is provided at temperatures ranging from 15- 60 degrees C and pressures ranging from 200-1100 kPa.

[0047] During charge, the hydride bed is advantageously cooled using a circulating fluid (with typical maximum flow of 50 slpm for the whole storage bank) coupled to a radiator advantageously equipped with an integral fan.

During discharge, a portion of the heat generated by the stack is used to provide heat when required.

The Electrolyser Module 224 [0048] All control responsibilities during charge and discharge are performed by the electrolyser module's controller in communication with the master controller.

[0049] The electrolyser module 224 has the following operating parameters (again, as with the fuel cell power module 222 described above, the values that follow are only examples of possible values-these values may vary according to different variants of the invention). The electrolyser module 224 typically has a total rated electrical capacity of 6kWe. The stack advantageously operates at 2.4V per cell. The throughput of hydrogen is typically about 24 sipm. The hydrogen is typically delivered at 150 psig, for example provided by using a small hydrogen compressor if necessary. Inlet water is supplied at a temperature of typically 60 degrees C. The water flow rate is typically 0.3 liters per cell. The oxygen generated is vented to the atmosphere, unless there is a particular use for the oxygen depending upon where the system is located. The charge time for 50 kWhe at 24 sipm H2 is approx. 24 hours. Adding a larger electrolyser can shorten this time; however, the costs will also increase.

[0050] An electrolyser BOP comprises back pressure control, process water flow control, cell temperature control and cell power supply control. A dryer (for example a Pd filter) and a compressor are also part of the metal hydride charging system.

[0051] The electrolyser controller is responsible for temperature control of the inlet water as well as back pressure control of the product gases from the stack. For start-up, the controller assumes the responsibility of gradually ramping up the pressure so as not to exceed the differential pressure rating of the stack (across the membranes). The electrolyser controller monitors all the cell feed voltages as well as any safety parameters, such as outlet pressure, water content (dew-point), and input voltage. The status of the electrolyser sub-system is available to the Master Controller of the unit. The completeness of charge to the metal hydride is monitored, for example using a flow meter,

and a reduction in flow into the hydride bed below a certain level is the criterion for the charge to be complete.

[0052] The ERM 224 produces hydrogen at a desired pressure to be stored in the Hydrogen Storage Module (HSM) 226. The ERM module 224 interfaces the following other modules : ERM Interface Interacting Module Hydrogen Gas Output Fuel Storage Module (FSM) 226 Thermal Heat Rejection Ambient (AMB) Ancillary Power Supply Power Conditioning Module (PCM) 228 Non Combustible Exhaust Ambient (AMB) DI-Water Supply Electrolyser Refueling Module (ERM) 224 Physical Interface FCPM/HSM/AMB/PCM ERM Controller Control and Instrumentation Module (CIM) 230

[0053] Possible interface requirements for the Electrolyser Refueler Module are: [0054] Hydrogen gas supply at a pressure of 700 kPaA, temperature of 5 to 80 degrees C, composition 99.997% hydrogen, maximum flow rate 3 sipm and less than 1 ppm CO. Thermal heat rejection electrolyser waste heat approx. 2kW at 80 degrees C. Ancillary power supply 24 VDC, up to 120 A and total net power 3 kW. Non-combustible exhaust at a pressure of above 104 kPaA, temperature below 45 degrees C, less than 2 % hydrogen and a maximum flow rate of 550 slpm dry plus 150 slpm water vapor. De-ionized water storage at ambient pressure, temperature 5 to 40 degrees C, above 5 M_ purity and at a flow rate less than 1 Ipm (100 I storage). Physical dimensions (WxDxH) maximum 17"x25"x25", maximum weight 100 lb. ERM controller interface serial (or equivalent as dictated by control system used).

[0055] In one embodiment, the electrolyser module 224 data as well as the operating conditions are: 10 cells, dimensions under 160 mm diameter and 85 mm height, weight under 16 kg, maximum electric power 3 kW, maximum hydrogen output 3 Ipm, stack voltage 20 to 22 V and maximum current: 140 A.

[0056] According to another embodiment, five interfaces (fluid interfaces, electrical interfaces and physical interfaces) have been defined for the FCPM: I) Anode input fluid, pressure 700 kPaA, temperature approx. 70 degrees C, de-ionized water, flow rate 3 to 5 slpm, resistivity above 3 M_/cm and a pH of approx. 7.

II) Anode output fluid, pressure approx. 700 kPa, temperature approx. 80 degrees C, a saturated stream of oxygen and water at a flow rate of 1 sipm.

III) Cathode outlet fluid, pressure approx. 700 kPa, temperature approx. 80 degrees C, saturated stream of hydrogen and water at a flow rate of 2 slpm.

IV) Power output, required stack voltage 24 V, stack current 0 to 120 A, stack electric power input 0 to 3 kW and single cell voltages of 1.6 to 2. 4 V.

V) Physical dimensions 8"diameter by 8"tall, weight 12 kg.

[0057] The HSM stores hydrogen for use in the FCPM. In one embodiment, it can provide up to 50 kWhe of hydrogen. The HSM module interfaces the following other modules : HSM Interface Interacting Module Hydrogen Gas Input Electrolyser Refueling Module (ERM) 224 Thermal Heat Input Fuel Cell Power Module (FCPM) 222 Thermal Heat Rejection Ambient (AMB) Ancillary Power Supply Power Conditioning Module (PCM) 228 HSM Controller Control and Instrumentation Module (CIM) 230 Combustible Exhaust Ambient (AMB) Physical Interface FCPM/HSM/AMB/PCM/CIM Hydrogen Gas Output Fuel Cell Power Module (FCPM) 222

[0058] Possible interface requirements for the Hydrogen Storage Module 226 are (again, the values that follow are only an example of possible values-these values may vary in different variants of the invention): I) Hydrogen gas input, pressure approx. 700 kPaA, temperature 5 to 80 degrees C, composition 99.997 % hydrogen, maximum flow rate 3 sipm, less than 1 ppm CO.

II) Thermal heat input, pressure approx. 200 kPaA, temperature 20 to 80 degrees C, de-ionized water at a flow rate of 22 to 44 sipm.

III) Thermal heat rejection of 500 W waste heat during charging.

IV) Ancillary power supply, input power 200 W, input voltage 24 VDC and input current 8A.

V) HSM controller, serial connection (or equivalent depending upon control system used).

VI) Combustible exhaust, pressure approx. 230 kPa, temperature below 80 degrees C, humidified hydrogen at a flow rate of maximum 10 slpm.

Vil) Physical dimensions (WxDxH) 800 mm x 200 mm x 1000 mm, weight approx. 250 kg.

VIII) Hydrogen gas output, pressure 300 to 700 kPa, temperature below 80 degrees C, dry hydrogen at a maximum flow rate of 180 slpm.

[0059] Possible Metal Hydride Cylinder Operating Conditions are: 3 canisters (depending upon desired operating conditions of the system), dimensions under 800 mm in length and 25 mm diameter, weight approx. 70 kg each, maximum hydrogen output 100 Ipm each, discharging temperature above 20 degrees C to 80 degrees C, charging temperature below 50 degrees C.

[0060] For the HSM 226, five interfaces (fluid interfaces, electrical interfaces and physical interfaces) have been defined (again, the values that follow are only an example of possible values-these values may vary in different variants of the invention): I) Charging fluid, pressure approx. 700 kPaA, temperature below 50 degrees C, 99.997 % hydrogen, -50 degrees C dew-point at a flow rate of 2 sipm.

II) Coolant inlet fluid, pressure below 30 kPa, temperature between 30 and 80 degrees C, de-ionized water with conductivity below 1 pS/cm, pH approx. 7, at a flow rate of 25 to 50 Ipm.

III) Coolant outlet fluid, atmospheric pressure, temperature 30 to 80 degrees C, de-ionized water with conductivity below 1 uS/cm, pH approx. 7, at a flow rate of 25 to 50 Ipm.

IV) Hydrogen discharging fluid, pressure approx. 230 kPa, temperature below 80 degrees C, humidified hydrogen at a flow rate of 180 slpm maximum.

V) Electrical interface, 24 VDC, maximum current 25 A, electrical power 600 W.

VI) Physical dimensions (WxDxH) 600 mm x 150 mm x 1000 mm, weight approx. 210 kg.

[0061] In one embodiment, the ancillary DC-DC converter has the following desired properties: physical dimensions (LxWxH) under 150 mm x 100 mm x 10 mm, weight approx. 200 g each (4 units used for the tested embodiment), maximum power output per unit 500 W (nominal power output for whole converter is 10 kW), battery voltage input 21 to 48 V, voltage output 23 to 28 V regulated, fan cooled, efficiency approx. 89.5%.

[0062] In an embodiment, the AC inverter has the following desired properties: physical dimensions (LxWxH) under 500 mm x 170 mm x 170 mm, weight approx. 1.5 each (8 units used for the tested embodiment), maximum power output per unit 1500 W (power output for whole inverter is 12 kVA), voltage input from fuel cells 36 to 72 V, voltage output 120/240 VAC 1 or 3 _ (this might vary depending upon grid specifications), air cooled, efficiency approx. 83 % minimum, full load to half load.

[0063] The Controls and Instrumentation Module (CIM) 230 preferably uses two individual controllers for the FCPM 222 and ERM 224 and one overall supervisory controller to oversee the whole system.

[0064] The HyUPSTM system 220 preferably includes the following four control modules : I) HSM controller, il) FCPM controller, 111) ERM controller and IV) Overall system controller.

[0065] The following section describes a sequence of operations that, in one embodiment, allows the HyUPS system 220 to function. Grid power initially powers the system, feeding power to the rectifiersthat charge the traditional back-up power supply (battery bank), and other equipment, consisting of 10 kW of AC power, power to the HVAC system as required (one or two units are utilized, depending on the heat load) each unit requiring 5 kW of DC power, and possibly lights in the enclosure in which the system is housed (roughly 1 kW of AC power). The HyUPST system 220 will be in standby mode during this time, monitoring the state of grid power. If the HyUPSTm system 220 is not in the fully charged state of 100 kWh (electric

equivalent) of hydrogen and 1 kWh of battery bank storage then the system is recharged via the electrolysis method described above. The grid is constantly monitored during this time. If the voltage on the grid sags below 205 VAC (or another pre-set value depending upon the specifications of the grid), the battery system will provide the initial AC power to the grid. The battery voltage is constantly monitored to ascertain it will be in good condition (unless batteries are depleted from a previous brown-out or black-out.) [0066] The system controller 230 is constantly operating during this time and the unit rests in standby mode (see Figure 11). If the voltage drops to below 205 V AC (or a desired switch-on voltage depending upon the specifications of the grid) the automatic transfer switch (ATS) (shown as X-fer switch 236 in Figure 3) checks the voltage of the unit (which will be above 205 V coming from the inverters) and switches its internal relay to feed power from the HyUPSTM system 220. Immediately the HyUPS system 220 goes through the start up procedure and prepares the FCPM for operation. After a first time period, during which the battery allows initial start-up (for example one minute), the FCPM 222 is in a state which is capable of maintaining the load. Any state of charge lost on the battery is also recharged via the FCPM 222. The FCPM 222 then provides enough power to recharge the internal battery bank in the control and instrumentation module 230, as well as the external rectifier load for the batteries. After a second time period, for example 5 minutes from start, power is provided to the first HVAC unit. After third period of back-up operation, for example 5 minutes, the second HVAC unit is powered (if the HyUPS is capable). Power is maintained by the HyUPSTM system 220 until either the grid power returns or the HyUPSTM system 220 reaches a critical low hydrogen storage level. When grid power returns, the unit stops providing power to the site. At this point, internal battery charge level is checked. Low internal battery power will be checked prior to HyUPSTM system 220 shutdown. This is followed by shutdown of the HyUPSTM system 220. After a successful shutdown the unit returns to standby operation prepared for another test or grid failure.

[0067] Electronic Instrumentation is installed to provide the operator and control and instrumentation module (CIM) 230 with information about the process.

[0068] The control and instrumentation module 230 sends output signals to various discrete and analog devices to effect control of the HyUPSTM.

[0069] The following section describes in detail the operation of the fuel cell power module (FCPM), electrolyser recharge module (ERM) 224, power conditioning module (PCM) 222, control and instrumentation module (CIM) 230 and hydrogen storage module (HSM) 226 during different modes of HyUPSTM system 220 operation in accordance with an aspect of the invention.

Start-up Mode [0070] 1. The unit is ON in Standby Mode and has initialized the control and instrumentation module (CIM) 230. The automatic transfer switch (ATS) 232 transfers power from the grid 234 to the HyUPS unit 220. The power conditioning module (PCM) 228 includes a relay battery bank and Primary Inverters. Power is supplied via the relay battery bank and primary inverters to support the 10 kW load of the radio rectifier 240 linked to base radio equipment 242.

[0071] 2. FCPM 222 starts up. The air compressor turns ON at 20% of rated power. A hydrogen solenoid OPENS and a mass flow controller turns ON to 20% of rated flow. A first relay changes auxiliary power from the battery bank to a DC-DC converter to run auxiliary power. After 30 seconds of operation, a second relay switches auxiliary power from the battery bank to the fuel cell stack.

[0072] 3. After one minute of operation (for example), a third relay switches the inverter feed power from the battery bank to the fuel cell stack.

After five minutes of operation (for example), a first timer turns on a fourth relay to the primary HVAC unit. After 10 minutes of operation (for example), a second timer turns on a fifth relay to the secondary HVAC unit.

[0073] 4. The FCPM 222 continues to operate to operate until steady state operation is achieved.

Normal Operation [0074] 1. The HyUPS system 220 is in start-up mode and the control and instrumentation module (CIM) 230 is monitoring temperature, relay position and state of charge of the hydrogen storage module (HSM) 226 and power conditioning module (PCM) 228 (see Figure 12, electric generation mode, and Figure 13, hydrogen generation mode). Once all steps in start-up mode are completed and a first temperature sensor indicates the operating temperature has reached 80 degrees C the HyUPS system 220 is in Normal Operation Mode.

[0075] 2. The FCPM 222 powers the load (for example a cell telephone central 244 as shown in Figure 4).

[0076] 3. A first pressure Sensor and a second temperature Sensor monitor the HSM module 226 coolant outlet temperature and cylinder pressure. The CIM 230 uses these values to compute the instantaneous fuel reserves (for example through a calibrated data base for the MH units) and determine if the unit should be turned off. If the condition above is satisfied, the HyUPS reverts to shutdown mode.

[0077] 4. A first voltage sensor is monitored by the CIM 230 to determine when the power has been returned from the grid. The CIM 230 will recharge the battery bank when grid reconnection is recognized. A sixth relay connects the battery bank to the fuel cell stack. When a second voltage sensor reads low battery voltage (for instance under 52 V for battery bank voltage), the HyUPS 220 enters Shutdown Mode.

[0078] 5. There are faults that will trigger an emergency shutdown of the unit. These are listed in the following table. Instrumentation Fault I/O Action Hydrogen sensor HS-High 0 (open circuit) Emergency Shutdown 101 Stack Temperature High TC-101 > 90 deg. C Stack Temp Emergency Shutdown

[0079] 6. The HyUPSTM system 220 is ON in Standby Mode.

Shutdown Operation [0080] 1. Figure 14 shows the E-stop recovery mode operation.

[0081] 2. The CIM 230 changes state to Standby Mode. A seventh relay is closed to provide AC power to the HyUPST system 220.

Standby Operation [0082] 1. The HyUPS system 220 is in alert mode waiting to provide back-up power. The CIM 230 monitors the ambient temperature and turns on a process heater if the temperature drops below 10 degrees C (for example). The CIM 230 monitors the HSM 226 for fuel reserve is adequate.

The CIM 230 switches to recharging mode if the reserve is low.

[0083] 2. The CIM 230 changes state to Standby Mode.

[0084] After the CIM 230 gets powered on the system will go into OFF Mode. The CIM 230 monitors mode change requests, see Figure 16.

[0085] Standby Mode is the normal operating condition. The CIM230 monitors tank pressure and grid presence (Figure 11).

[0086] Gen Mode: The FCPM 222 powers everything after a grid power failure (Figure 12).

[0087] Regen Mode: The Electrolyser module 224 refills the H2 tank (Figure 13).

[0088] E-Stop Recovery Mode: Safety sequence, which can be triggered by external (outside the CIM 230) and internal events (Figure 14).

[0089] Figure 15 shows the mode change sequence check performed at mode change requests. Figure 16 shows the off mode operation.

[0090] Thus, the UPS system is either recharging or discharging hydrogen. In recharge condition, the hydrogen storage tanks are empty or depleted (as detected by FSM sensors), the grid is present and powers the electrolyser module and the fuel storage module (hydrogen storage module), the electrolyser is enabled and produces hydrogen (typically at a rate of 6 g/min) and the fuel storage module compresses the output hydrogen gas to a pressurized storage tank (typically, the hydrogen storage is fully replenished within 8 to 10 hours). In discharge condition, either caused by grid failure or during testing, the transfer switch directs power flow from the UPS system to the load (for example a cellular phone station), the FCPM enters the start-up mode and begins to generate electric power to ramp up backup power within a certain time period, typically 1 to 2 minutes, full capacity fuel storage tanks will supply typically approximately 2 hours of hydrogen fuel consumption for backup power generation. If the grid returns for a predetermined period of time, the transfer switch reconnects the grid to the load and the hydrogen tanks are refilled as described earlier in conjunction with the recharge condition.

[0091] The following controls are made and monitoring performed to ensure safety standards are met: All relevant FCPM parameters are monitored and logged (temperature, gas flows and pressures) for optimal performance of the fuel cell via the ECU. The CIM 230 acts as a supervisory controller, handling all data from the ECU and monitors all other modules for emergency stop conditions. The CIM 230 acts as an intermediary for data retrieval and remote HyUPS control. Preferably, a hard-wired safety line connects all modules and can be engaged by any module. The FCPM safety considerations include hydrogen leaks, over-temperature conditions, over- pressure conditions and under-voltage conditions.

TESTS [0092] The HyUPSTM system 220 according to an aspect of the invention was tested to demonstrate the feasibility of fuel cell power as an alternative to battery backup systems for communications cellular sites. A 25 kVA HyUPSTM fuel cell backup power system was used. The test lasted for a period of approximately 2 months, and yielded very impressive results.

[0093] The HyUPS system 220 is designed to provide a source of backup power when the electrical grid fails. There is enough hydrogen storage on-board to fulfill the requirements of 25 kW for 2 hours at full load. In the case of this test, the load was typically less than 11 kW. Therefore, the scalability of the system allowed for a 4 hour discharge time. It is important to note that the HyUPSTM provided site power, as though from grid (AC & DC), and therefore was subject to the cycling of the installed high voltage AC (HVAC) unit. The HyUPSw system 220 is also regenerative, in that it is able to refill its hydrogen storage tanks, when grid power is present. This is typically performed at off-peak hours. The rate of charge is dependent on the power provided to the charging subsystem; in this case, the charge time was found to be approximately 18-20 hours. Under full power draw, this can be reduced to between 6 and 8 hours.

[0094] The HyUPSTM system 220 is based on the integration of several different modules. The modules are: the electrolyser module (EM) 224 used in charging the storage tanks of the fuel storage module (FSM) 226, the power electronics module (PEM) 228, the thermal module (TM), the overall system controller (CIM) 230, and the fuel cell power module (FCPM) 222. The overall system diagram is shown in Figs. 2 to 4. Note that the only electrical interfaces to the user are the 208 VAC, 3-phase input and output (or similar, depending upon grid specifications).

[0095] For the test there was already an existing diesel generator on- site, and electrical interfaces to accommodate it, so the HyUPSTM system 220 was set up and connected to the identical connection points used for the

traditional generator. Grid power and alternate power was switched via a transfer switch, which allowed the simulation of grid failures, in addition to being available in the case of a true grid failure.

[0096] The data obtained from the test focus on two key aspects: system operational observations during typical charge and discharge cycles, and system overall performance over the duration of the test. For typical charge and discharge cycles, of which there were many throughout the test, data is presented showing typical site power draws from the HyUPSTM system 220 versus time, hydrogen consumption and production rates versus time, electrical power production and consumption levels, and key measures of power quality. For overall system performance throughout the duration of the test, data is provided on accumulated run-time (both charging and discharging) vs. time, up-time vs. downtime, measured overall system efficiencies, and facility usage.

[0097] As discussed, there were numerous charge and discharge cycles throughout the test, mostly simulated. In fact, there was not one true grid failure throughout the two month period that the Hydrogenics HyUPSTM system 220 was present on-site. The discharge tests typically lasted for 4 to 4.5 hours at a time, although some were pre-set at 1/2 hour each. The HyUPSTM system 220 is designed to monitor the storage tank pressure, and will enter'regeneration'or recharge mode if the tank pressure dips below a pre-set limit, following a partial or complete discharge (ie. discharging/ providing backup power takes priority). In this case, the limit was set to 4000 psi.

[0098] The discharge power developed by the fuel cell within the FCPM 222 was recorded as varying between 10.5 kW and 16.5 kW gross (this load would be inclusive of the HyUPSw system 220 own parasitic losses, for example blowers and pumps), depending on the cycling stages of the HVAC system. As mentioned, the HVAC system would cycle on and off depending on the temperature inside the site. The parasitic losses ranged from approx.

4.5 kW at the low power discharges to approx. 6 kW at the higher discharge

power levels. This would imply true net AC power delivered (which was also measured current-wise) to the site of 6 kW to 10.5 kW. Obviously during hotter days, when most of the data was gathered, the system would spend more time at the 10.5 kW level, being a load-following unit. This power was verified by measuring site phase currents. A plot of site load (power delivered) for each of the three phases of the 208 VAC 3-phrase output versus time, during one of the four hour discharge runs is shown in Figures 5A and 5B.

[0099] The observed 4 to 4.5 hour discharge cycles were based on the 5000 psi (140 liquid liters or 3.14 kg gaseous hydrogen) storage tank used in this test. The hydrogen usage from this tank was seen to be linear, implying that a tank of double the liquid volume would be able to provide 100 kWh as compared to the 50 kWh observed using the present tank. It is possible to use a larger volume tank, which will operate at lower pressure that that of the test.

For this test, a plot of hydrogen consumed versus time is shown in Figure 6.

[00100] In order to charge the hydrogen storage module 226, the electrolyser module 224 used between 30 and 32 A at 208 VAC 3-phase to power its stack power supply (equivalent of approx. 10.5 kW), and about 100 A at 12 VDC (approx. 1.2 kW) for parasitic loads. Therefore, the total power required for charging was approx. 11.7 kW for 18 hours (the complete charge time). Note that if a large breaker is provided, it is possible to run the electrolyser at a higher power level. By doubling the 3-phase power, one actually halves the charge time (in effect more than half since the total charge time running at 65 A 3-phase current is only 8-9 hours). Power consumed during the charge cycles will be discussed further in the section below dealing with system efficiency. A graph showing the rate of hydrogen generation observed during the test is shown in Figure 7.

[00101] Power quality was assessed and overall the power quality was deemed superior, with no complete voltage drop-outs or abnormal voltage swells. Slight (approx. 10 %) transient voltage dips were observed periodically at the point where the site HVAC systems powered on. This was considered to be normal, due to the inductive loading of these systems. Phase voltages

were sustained within 5% of 120V, 99% of the time. Voltage total harmonic distortion was minimal, but slightly noticeable, with high frequency spikes being observed, and translated into occasionally flickering site lighting. The results of the power quality analysis are summarized in Figures 8A and 8B.

That is, Figure 8A illustrates in a histogram the variation in output voltage for each of the three phases. Figure 8B shows the same information for total harmonic distortion (THD). As can be seen from these figures, the variation is greatest for phase B; however, even this variation falls well within acceptable limits. Figure 9 shows the system response when triggering upon an event, which, in this case, is the powering on of the site air conditioning unit. Both current and voltage responses to this transient load are shown.

[00102] As a mobile backup power system, the HyUPSTM system 220 performed very well during the two month test. A remote alarming and telemetry system was also integrated into the system. This system allowed the remote monitoring of system performance and modes. This was done using a wireless modem connected to the telephone network (wire or cellular), which would feed HyUPS data to a web site. For a total of 8 weeks, the system was run for a total of 2,016 minutes, or just under 34 hours in power generation mode, and 14,427 minutes, or 240 hours in regeneration or recharge mode. A graph showing accumulated site discharge minutes versus week is shown in Figure 10.

[00103] Overall, throughout weeks 2 though 7 (i. e. not including set up and decommissioning of the system) the HyUPSTM system 220 availability averaged 95. 2%. In this instance, system availability is defined as the percentage of time during the period in question, where the HyUPSTM system 220 was both able and ready to provide a minimum of 2 hours of backup power. Availability was limited during weeks 1 and 8 due to set up time and durability issues with a power electronics component respectively. Both the fuel cell power module 222 and fuel storage module 226 averaged well over 99% availability, following initial set up during the entire 8 weeks.

[00104] Despite the harsh duty cycles used in the testing (simulating probably 5 years worth of grid failures in two months), it is clear that in future iterations, durability must be a key factor in the design. This is most obvious in the electrolyser module 224 and the power electronics module 228. Very little maintenance was required for the fuel cell power module. In addition, the fuel storage module, being a very simple device, had no issues whatsoever.

[00105] The electrical and mechanical interfacing of the HyUPS system 220 is quite simple in that the only inputs are 208 VAC 3-phase electrical power (or equivalent depending upon power grid specifications), and water. It is possible to make the system close to water-neutral, as the fuel cell produces large amounts of water at full load, thereby eliminating a large portion of the second requirement. There is only one output, that being 208 VAC 3-phase, or site backup power. During the test, a water tank (500 gallons) was used to fulfill the requirement for water. A filtering bank (which was for this test external to the UPS) was used to filter and polish the stagnant water from the tank. The total amount of water consumed during the test period was approximately 110 gallons. Note that a water-recovery subsystem was added halfway through the test to recover excess water from the cathode of the fuel cell (which was not re-circulated to the fuel cell itsel0.

This water was fed back into the tank during each discharge cycle.

[00106] Electrical consumption can be calculated from the measured power draw observed during system charging. For one full system charge (i. e. for this test 300 psi to 5,000 psi), the electrical power required was approximately 11.7 kWx 18 hours = 210.6 kWh. From this number, and both the fuel cell and site output power measurements taken during the test, electrical efficiency figures can be generated. One such figure, which focuses on fuel cell power itself, is the electrical efficiency of the fuel cell power module. This assumes there is a supply of hydrogen available, and does not take into account the energy required to create the hydrogen (similar to the case of purely focusing on the engine portion of a diesel generator). As discussed previously in the discharge cycling section, using the time-average

measured gross fuel cell output power of 14 kW, and the net time-averaged 9 kW delivered to the site, one arrives at a fuel cell power module 222 efficiency of 64.2%. This number includes parasitic power used by the FCPM 222 as well as inefficiencies in the power electronics module, whose efficiency figure was measured to be 86%.

[00107] With respect to the electrolyser module 224, it is known that using"ideal gas"hydrogen as a fuel, 15.24 kWh can be produced by 1 pound of hydrogen. Given the fuel storage module 226 capacity of 6.92 pounds, and the electrical consumption during one complete charge of 210.6 kWh, one arrives at an electrolyser efficiency of approximately 50. 1 %. On a higher level, for the ratio of fuel cell energy produced (ignoring the parasitic loads) to energy required to generate the hydrogen, the number is (approx. 63 kWh/ approx. 210 kWh) 30. 0%. Inclusive of parasitic loads, one arrives at the true measured electrical output/electrical input efficiency number for the test. For one of the standard runs of 4.5 hours, and using a time-averaged power delivered of 9 kW, the overall electrical efficiency is 19.2%, based on a 210.6 kWh charge power requirement.

[00108] The test clearly reveals the feasibility of hydrogen fuel cells as an alternate source of backup power. A successful simulation of over 33 hours of grid failure over the course of two months (equivalent of 2 to 5 years of"real-world"grid failure) was performed, and this demonstrated the ability to generate fuel through the use of electrolysis. Durations for complete discharge and charge for this particular site load were determined to be 4.5 and 18 hours respectively. The power provided met the needs of the entire site, both AC and DC, and power quality was verified as being excellent.

Efficiency numbers were surprisingly very strong for an initial prototype system. In addition, there exist the"hidden"benefits of charging during off- peak hours, peak shaving, and discharging during'peak power'situations in a grid-tie configuration. These benefits coupled with the lack of emissions, major noise reductions, when compared with comparable diesel generators, make fuel cell backup power a truly viable alternative. Referring to Figures 11-

16, the various operating modes described above are described in more detail.

[00109] Referring to Figure 11, the process flows by which the HyUPS system 220 changes from standby mode are illustrated in a process flow diagram. In standby mode, the control and instrumentation module 230 continuously monitors tank pressure within hydrogen storage module 226, using a fuel storage sensor (not shown), as well as whether grid power is present, using a grid sensor (not shown). If the voltage on the grid falls below 205 VAC, or another pre-selected value, then the control and instrumentation module 230 will infer that the grid is no longer present (i. e. , the grid is no longer supplying electricity). Logic circuit 254 receives inputs 250 and 252 representing tank pressure within hydrogen storage module 226, and a low limit or a threshold for this tank pressure respectively. Logic circuit 254 then determines whether the tank pressure is below the low limit. If the tank pressure is not below the low limit, then the control and instrumentation module 230 proceeds, via logic circuits 254 and 256, to decision 258, in which the control and instrumentation module 230 decides to remain in standby mode. If, on the other hand, the tank pressure provided by input 250 has fallen below the low limit specified by input 252, then logic circuit 256 checks input 260 to determine if the grid is present. If input 260 indicates that the grid is present, then logic circuit 256 returns decision 262, in which the control and instrumentation module 230 switches HyUPSTM system 220 from standby mode to regeneration mode. In regeneration mode, the electrolyser module 224 is turned on, using power from the grid, to recharge the hydrogen storage module 226. The control and instrumentation module 230 checks if the grid is present, via input 260 and logic circuit 256 as electrolyser module 224 is run using power from the grid. If input 260 indicates that the grid is not present, then the control and instrumentation module 230 proceeds to decision 258, in which, as described above, HyUPSw system 220 remains in standby mode.

[00110] On the right hand side of Figure 11, a possible shift from standby mode to generation mode is illustrated. Specifically, logic circuit 266

receives inputs 250 and 264 indicating, respectively, (i) tank pressure for the hydrogen storage module 226, and (ii) a lower limit for this tank pressure plus a hysteresis factor or a buffer. If the tank pressure indicated by input 250 is below this combined low limit and hysteresis factor indicated by input 264, then logic circuits 266 and 268 return decision 270, such that the control and instrumentation module remains in standby mode. If, on the other hand, logic circuit 266 determines that the tank pressure exceeds the low limit plus the hysteresis factor, then logic circuit 268 will determine if the grid is not present by checking input 272. If the grid is not present and the tank pressure is above the low limit plus the hysteresis factor, then logic circuit 268 will return decision 274, in which control and instrumentation module 230 switches HyUPSTM system 220 from standby mode to generation mode. Input 264 specifies the hysteresis factor as it is important that the tank pressure exceed the low limit by a certain amount; otherwise, as soon as the HyUPSm system 220 switches to generation mode and begins to consume hydrogen, the tank pressure in hydrogen storage module 226 will fall below the low limit, and the control and instrumentation module 230, as described in more detail with respect to Figure 12, will go back to standby mode.

[00111] Referring to Figure 12, mode switches beginning from a generation mode are illustrated in a process flow diagram. In query 280, the control and instrumentation module 230 checks whether the power electronics module 228 is ready to move to generation mode SA (SA stands for"stand alone"meaning that the load supported by the HyUPSTM system 220 can continue to operate without power from the grid. That is, the generation mode involves two submodes: (i) a start-up submode in which electricity is supplied from the battery to the external load while the fuel cell power module is brought online, and (ii) a normal operation mode in which electricity is supplied from the fuel cell power module to the external load. If the battery is unable to supply enough electricity during the start-up submode, then the generation mode cannot commence). Thus, query 280 will involve checking the battery within the power conditioning module 228 using a state-of-change

sensor to see if it has sufficient charge to begin supplying electricity to the external load. If query 280 returns the answer FALSE, then clearly, as described above, the generation mode cannot begin and in decision 282, the control and instrumentation module 230 goes to emergency stop recovery mode. If, on the other hand, query 280 returns the answer TRUE, then the control and instrumentation module 230 goes to decision 284 in which the fuel cell power module start sequence is initiated. If this fuel cell power module start sequence is successful, then the control and instrumentation module, in decision 286, begins the generation loop. If, on the other hand, the FCPM start sequence is unsuccessful, then the control and instrumentation module 230 proceeds to decision 288, in which the HyUPSw system 220 goes to emergency stop recovery mode.

[00112] In the generation loop, illustrated in Figure 12, logic circuit 292 first checks whether the tank pressure provided by input 290 is below a low limit specified by input 294. If the tank pressure is below the low limit, then there is not enough fuel stored to continue running the fuel cell power module 222, and the control and instrumentation module 230 will simply switch the HyUPSTM system 220 to standby mode in decision 296 (this process is outlined in detail in Figure 15). If, on the other hand, the tank pressure specified by input 290 is above the low limit specified by input 294, then project circuit 298 checks input 300 to determine if the grid is supplying power at an acceptable level. If the grid is providing power at an acceptable level, then there is no reason to remain in generation mode, and the control and instrumentation module 230 switches the HyUPSTM system to standby mode in decision 296. If, on the other hand, input 300 indicates that the grid is not providing electricity at an acceptable level, then the control instrumentation module 230 will, in decision 302, maintain the HyUPS system 220 in generation mode.

[00113] While in generation mode, the control instrumentation module 230 constantly monitors itself as well as all of the operating modules-i. e. the fuel cell power module 222, the electrolyser module 224, the hydrogen

storage module 226 and the power conditioning module 228-for emergency conditions. If emergency conditions arise with respect to any of these modules, as shown on the right hand side of Figure 13, then this will trigger an emergency stop described below in connection with Figure 14.

[00114] Referring to the right hand side of the loop of Figure 12, the control and instrumentation module 230 checks input 304 to see if an E-stop has been triggered. If so, then in decision 306, the control and instrumentation module goes to emergency stop recovery mode. If input 304 does not indicate that an E-stop has been triggered, then in decision 308 the control and instrumentation module 230 maintains the HyUPSTM system 220 in generation mode.

[00115] Referring to Figure 13, the process flows by which the HyUPSTM system 220 switches from regeneration mode are illustrated in a process flow diagram. The regeneration mode begins with the electrolyser start sequence of step 310. If this electrolyser start sequence is not completed successfully, then in decision 312, control instrumentation module 230 moves to emergency stop and recovery mode. If, on the other hand, the electrolyser start sequence is completed successfully, then the control and instrumentation module 230 proceeds, via decision 314 to look for conditions in which the regeneration mode should be halted. That is, logic circuit 316 receives inputs 318,320 representing tank pressure within hydrogen storage module 226 and a high limit or upper threshold for this tank pressure respectively. Logic circuit 316 then determines whether the tank pressure provided by input 318 exceeds the high limit provided by input 320. If the tank pressure exceeds the high limit, then hydrogen storage module 226 is effectively full, and in decision 322 the control and instrumentation module 230 switches HyUPSTM system 220 from regeneration mode to standby mode, as there is no longer a need to generate fuel. If, on the other hand, logic circuit 316 determines that the tank pressure does not exceed the high limit, then logic circuit 324 checks input 326 to determine whether the grid is present-i. e. whether the grid is providing electricity at an acceptable level. If

the grid is providing electricity at an acceptable level, and the hydrogen storage module is not yet full, then there is no reason to leave the regeneration mode, and in decision 328, the control and instrumentation module maintains the HyUPS system in regeneration mode. On the other hand, if the grid is not present-i. e. supply of electricity has fallen below an acceptable level-then even if the tank pressure provided by input 318 is still below the high limit provided by input 320 (i. e. the hydrogen storage module 226 is not yet full), the regeneration mode must be halted as electricity can no longer be supplied to the electrolyser module 224 on a sustainable basis.

Thus, in step 322, the control and instrumentation module returns the HyUPS system 220 to standby mode.

[00116] As described above in connection with input 304 of Figure 12, which input is provided during the generation mode, the control and instrumentation module 230 constantly monitors itself as well as all of the operating modules during the generation mode. This also holds true during the regeneration mode. That is, input 330, which is provided during the regeneration mode, may indicate that emergency stop conditions exist. If so, then in decision 332, the control and instrumentation module 330 switches the HyUPS system 220 to standby mode. If input 330 does not indicate the existence of emergency stop conditions, then in decision 334 the control and instrumenation module 230 maintains the HyUPSTM system 220 in regeneration mode.

[00117] In Figures 11-16, queries ask whether the grid is, or is not, present. The criteria for determining whether the grid is, or is not, present will vary depending upon the particular circumstances in order to obviate hysteresis effects. That is, to avoid hysteresis effects, it is desirable that a slightly higher threshold in VAC be used to determine when to switch from regeneration mode to standby mode, then when determining when to switch from standby mode to regeneration mode. Similarly, a slightly higher VAC threshold should be used when determining whether to switch from standby

mode to regeneration mode than when determining whether to switch from regeneration mode to standby mode.

[00118] Referring to Figure 14, a process flow by which the HyUPSTM system 220 switches to emergency stop recovery mode is illustrated in a process flow diagram. That is, as described above in connection with the generation mode and regeneration mode of Figures 12 and 13 respectively, an emergency stop may be invoked in any one of these modes. In such case, in step 336 the HyUPSTM system 220 shuts down for 5 seconds. As indicated in step 338, this shutdown is maintained until the E-stop signal clears. At that point, as indicated in step 340, the control and instrumentation module 230 switches the HyUPSw system 220 from emergency stop mode to standby mode.

[00119] Referring to Figure 15, the sequence by which the HyUPSTM system 220 changes to standby mode is illustrated in a process flow diagram.

First, in query 340, the control and instrumentation module 230 checks the power electronics module 228. Among other things, the control and instrumentation module 230 checks whether the power electronics module 228 and fuel cell power module 220 are synchronized-that is, are in the same operating mode. That is, the fuel cell power module 220 has been switched to standby mode, and, therefore, the power electronics module 228 should also switch to standby mode in which the battery is charging. If the power electronics module 228 is not in standby mode, then in decision 342, control and instrumentation module 230 switches the power electronics module from standalone (generation) mode to a charge sequence in the standby mode, in which the battery is charged. If, on the other hand, the power electronics module 228 is already in standby mode and the battery is being charged, then in decision 344, the control and instrumentation module 230 leaves the power electronics module 228 in this mode. Following each of decisions 342 and 344, the power electronics module 228 is reinitialized in step 346.

[00120] If an emergency stop is triggered in input 348, then HyUPS system 220 will switch to emergency stop and recovery mode in decision 350.

If, on the other hand, an emergency stop is not triggered by input 348, then the HyUPS system 220 proceeds to standby mode in decision 352.

[00121] Referring to Figure 16, the process flows by which the HyUPSTM system 220 changes from off mode to standby mode is illustrated. In step 54, the HyUPSTM system 220 is turned on-in the ON state it immediately moves to standby mode as indicated in step 356. If not turned on, then as indicated in step 358, nothing happens.

[00122] It should be appreciated that the spirit of the present invention is concerned with the novel structure of the regenerative fuel cell system and the regulation of the system. The internal structure of the fuel cell portion and the electrolyser portion does not affect the design of the present invention. In other words, the present invention is applicable to various types of fuel cells and electrolysers. In applications where fuel gas is not pure hydrogen, reformers may be added before the inlet of the fuel gas for the fuel cell portion. In this case, the structure of the present system does not need to be changed.

[00123] It is to be anticipated that those having ordinary skill in this art can make various modification to the embodiments disclosed herein. For example, the shape of the fuel cells, electrolyser cells or the entire system might be varied, the electrolyser and the fuel cell portion might not necessarily be stacked one on top of the other. But rather they can be in juxtaposed position or even connected via conduits as needed in the situation. Further, instead of a battery, power electronics module 228 may include any suitable electrical storage medium, such as, for example, an ultra capacitor. Further, while in preferred embodiments, the HyUPSTM system 220 is regenerative, and thus includes an electrolyser module 224, this is not strictly speaking necessary. Instead, hydrogen or other suitable fuel could simply be supplied from an external source. However, these modifications should be considered to fall under the protection scope of the invention as defined in the following claims.