Fuel cell - electrolyzer or reversible fuel cell system and methods of operating thereof with a reduced carbon footprint

A method of operating a reversible fuel cell system, the method comprising:

• (A) determining a CO2 per kilowatt hour (kWh) power grid emission rate (GER) of a power grid electrically connected to the reversible fuel cell system;
• and
• (B) controlling the reversible fuel cell system based on a comparison between the GER, a CO2 per kWh hydrocarbon fuel emission rate of the reversible fuel cell system (NER), and a CO2 per kWh target emission rate (TER) that is less than the NER, wherein:
• if NER>TER>GER, operating the reversible fuel cell system in an electrolyzer mode using power received from the power grid to generate hydrogen, and storing the generated hydrogen;
• if NER>GER>TER, operating the reversible fuel cell system in a fuel cell mode using stored hydrogen to generate power that is provided to a load;
• and
• if GER>NER>TER, operating the reversible fuel cell system in the fuel cell mode using stored hydrogen and a hydrocarbon fuel to generate power that is provided to the load.

A power generation system that is configured to be electrically connected to a power grid and a load, the system comprising:

• an electrolyzer system configured to generate hydrogen using power received from the power grid;
• a hydrogen storage device configured to store the generated hydrogen;
• a fuel cell system configured to generate power for the load using at least one of hydrogen received directly from the electrolyzer system, hydrogen received from the hydrogen storage device, or a hydrocarbon fuel received from a hydrocarbon fuel supply;
• and
• a controller configured to:
• (A) determine a CO2 per kilowatt hour (kWh) power grid emission rate (GER) of a power grid electrically connected to the power system;
• and
• (B) control operation of the power generation system based on a comparison between the GER, a CO2 per kWh hydrocarbon fuel emission rate of the fuel cell system (NER), and a CO2 per kWh target emission rate (TER) that is less than the NER, wherein:
• if NER>TER>GER, control the power generation system to provide power from the power grid to the electrolyzer system to generate hydrogen, and provide the generated hydrogen to the fuel cell system to generate power for a load;
• if NER>GER>TER, control the power generation system to provide power from the power grid to the electrolyzer system to generate hydrogen (H2), and provide generated hydrogen and stored hydrogen that was previously generated by the electrolyzer system to the fuel cell system to generate power for the load;
• and
• if GER>NER>TER, control the power generation system to provide the stored hydrogen and a hydrocarbon fuel to the fuel cell system to generate power for the load.

A power generation system that is configured to be electrically connected to a power grid and a load, the system comprising:

• a hydrogen storage device configured to store generated hydrogen;
• a reversible fuel cell system configured to generate hydrogen using power received from the power grid in an electrolysis mode, and to generate power for the load using at least one of hydrogen received from the hydrogen storage device or a hydrocarbon fuel received from a hydrocarbon fuel supply in a fuel cell mode;
• and
• a controller configured to:
• (A) determine a CO2 per kilowatt hour (kWh) power grid emission rate (GER) of a power grid electrically connected to the reversible fuel cell system;
• and
• (B) control the reversible fuel cell system based on a comparison between the GER, a CO2 per kWh hydrocarbon fuel emission rate of the reversible fuel cell system (NER), and a CO2 per kWh target emission rate (TER) that is less than the NER, wherein:
• if NER>TER>GER, controlling the power generation system to operate the reversible fuel cell system in the electrolyzer mode using power received from the power grid to generate hydrogen, and storing the generated hydrogen;
• if NER>GER>TER, controlling the power generation system to operate the reversible fuel cell system in the fuel cell mode using stored hydrogen to generate power that is provided to a load;
• and
• if GER>NER>TER, controlling the power generation system to operate the reversible fuel cell system in the fuel cell mode using stored hydrogen and a hydrocarbon fuel to generate power that is provided to the load.