Fuel Cells Explained


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Balance of Plant

Balance of plant refers to supporting and/or auxiliary components based on the power source or site-specific requirements and integrated into a comprehensive power system package.


Filters remove solid material from a medium, such as a gas (air) or fluid. In the case of air, filters can be installed as part of a heating/cooling system through which air flows for the purpose of removing particulates before or after the air enters the mechanical components. In the case of a liquid or gas, it could be a pre-step to reformation (e.g. sulfur removal).

Filtration is important for all applications, particularly for sulfur removal in the case of transportation. Some of the key areas of development include

  • Sulfur removal
  • Diesel filtration (transportation)
  • Natural gas / propane (power generation)
  • Liquid filters (transportation)
  • Housing for filters and catalyst beds
    • Fuel processor gas clean-up (transportation)
    • Steam reformers (power generation)
    • Metal hydrides (portable power)

Seals and Gaskets

A gasket or seal is used to prevent the leakage of fluids and to maintain the pressure in an enclosure. Specifically, a gasket is used between two static surfaces to provide a seal. Sealing is an important issue for all applications. Some of the developmental areas today include:

  • High temperature seals
    • SOFC and MCFC applications
    • Fuel processing components
  • Good performance versus:
    • Load swings
    • Thermal gradients
    • Rapid transients (pressure, temperature)
    • Multiple cycles
  • Corrosion resistant
  • Hermetic seals
  • Solid state seals
  • Glass seals


A device used in piping to control the fuel supply to any section of a system of piping or to fuel utilization equipment.

Automatic. A device consisting essentially of a valve and operator that controls the fuel supply to the burner during normal operation of the equipment. The operator may be actuated by application of fuel pressure on a flexible diaphragm, by electrical means, by mechanical means or by other means.

Diaphragm Type. A device consisting essentially of an automatic valve actuated by means of the application of fuel pressure upon a flexible diaphragm.

Electric Type. A device actuated by electrical energy for controlling the fuel supply. These consist of the following:

Modulating. A valve designed so the valve opening is controlled within narrow limits throughout the entire range from the "full open to the "closed" position.

Motor. An electric control valve that is automatically closed by a spring or other mechanical means in the event the electric circuit is broken.

Solenoid. A valve that is opened or closed by the action of an electrically excited coiled wire magnet upon a bar of steel attached to the valve disc.

Step (Manual). A valve having a rotating plug usually with three positions and different rates of fuel flow for each. The plug is actuated by a solenoid or motor-driven rack and pinion and a cam arrangement. This apparatus and a combination push-button switch determine the position assumed by the plug.

Burner. A manually or mechanically operated valve which permits control of the flow of fuel.

Combustion (input) Control. An automatic control valve for regulating fuel input.

Latching Type. A manual gas valve which requires at least two separate actions or movements to turn the valve on, as for example, pushing in on the valve handle to unlatch the valve before the valve handle can be rotated to turn on the fuel.

Lubricated Plug. A valve of the plug-and-barrel type that has bearing surfaces designed to be re-lubricated without disassembly of the valve.

Main Burner, Individual. A valve that controls the fuel supply to an individual main burner.

Semi-Automatic. A valve that is opened manually and closed automatically, or vice versa.

Shutoff, Manual. A manually operated valve in a fuel line for the purpose of completely turning on or shutting off the fuel supply to fuel utilization equipment.

Shutoff, Manual Main. A manually operated valve in the fuel line for the purpose of completely turning on or shutting off the fuel supply to fuel utilization equipment, except to a pilot provided with independent shutoff valves.

Shutoff, Safety. A valve that is automatically closed by the safety control system or by an emergency device. Such valve may be of the automatic or manually opened type.

Spray Nozzles

  • Most important for transportation applications
  • Liquid fuel injectors
  • Humidifier sprays
  • Also applicable to remote power and back-up power applications
    • Diesel, or other liquid fuel spray
  • Need good mixing / vaporization characteristics
  • Small component size (vaporizers)
  • Low emissions / contaminants
  • Consistent performance over wide operating range
  • Consistent performance versus transients



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Fuel Cells Explained


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