I.                  Design Specifications

The purpose of our project is to design a testing and demonstration facility for Solid Oxide Fuel Cells (SOFCs). The unit will be designed to accommodate several fuel cells in series, called a fuel cell “stack”. This facility must provide a means to measure electrical output of each individual fuel cell and the fuel cell stack as a whole. It must also provide a visual demonstration of the electricity generated in a fuel cell by powering some sort of electrical device.  

A.      System Requirements

a.                  Housing:

The containment unit will be a combination of various materials, selected for their temperature resistance, cost, and manufacturing feasibility.

i.                     Temperature resistance: The unit will have to withstand extremely hot temperatures while providing mechanical support for the fuel cell, delivering the needed gasses, and providing adequate gas sealing to prevent hydrogen/oxygen reactions outside of the fuel cell.

ii.                   The inner unit must also provide a means for current collection from the each fuel cell individually and the stack as a whole

iii.                  Insulation: Insulation is needed on the inner unit to keep the fuel cells at high temperatures and to ensure a sufficient temperature drop to the exterior of the unit.

iv.                 Thermal stability: The entire unit must be designed to handle excessive thermal cycling, and to accommodate thermal expansion for temperatures ranging from room temperature to 1000°C.

v.                   Input/Output: The outer housing must support gas inlets and outlets, and all of the necessary electrical connections to perform measurements.

b.                  Gas Supply

The system needs to have a constant gas supply of hydrogen and oxygen. These gases will be used to create reactions at the anode and cathode of the fuel cell, which in turn create an electric current. This fuel cell testing device is unique in terms of SOFC (Solid Oxide Fuel Cell) systems, in that the seals must be gas-tight but not permanent. The entire multi-cell system must be capable of disassembly and reassembly in order to exchange fuel cell membranes for testing. This requirement combined with the requirement of high temperature seal functionality proves to be a challenging problem.

i.                     Seals: High temperature seals are needed to keep the hydrogen and oxygen from interacting in the hot zone of the unit. These seals must be functional up to the maximum operating temperature of 1000°C.

(1)   Fuel cell membrane (PEN) to gas delivery system: A seal must be made between the fuel cell membrane and the gas delivery system. The seal must be made on both sides of the PEN.

(2)   Gas delivery tubes to sub assembly: The gas delivery tubes must create a gas tight seal with the sub assembly, and with the other components of the gas delivery system.

ii.                   Temperature stability: All the components in the hot zone of the fuel cell must withstand temperatures up to 1000 °C.

(1)   Thermal cycling: Components in the hot zone must withstand repeated thermal cycling from room temperature to operating temperature for a maximum amount of cycles. 

(2)   Oxidation: Oxidation must be kept to a minimum and the usage of consumable parts must be avoided to keep costs down.

iii.                  Flow Supply and Regulation: The gas flow must be controlled and steady, and will be one of the variables in the experimental setup. The incoming gas must also be heated so as to avoid thermal stresses on the hot zone components.

(1)   Hydrogen Supply: Standard pressurized gas bottles will be used to supply the hydrogen.

(2)   Air Supply: Air will be supplied through the in-house compressed air supply.

(3)   Regulation: Flow will be controlled manually through flow regulators attached to the gas bottle and the air supply.

(4)   Monitoring: Flow meters are needed to monitor the gas flow to ensure the proper mass ratio of the reactants.

iv.                 Exhaust: An exhaust system is needed for all outgoing gases and by-products.

(1)   Heat Management: The exhaust leaving the reaction zone will be extremely hot, and must be cooled to an acceptable temperature before entering the surrounding atmosphere.

(2)   Reaction By-Products: The only by-product of a reaction between hydrogen and oxygen is water, which takes the form of steam in this case. The exit flow lines must be designed to accommodate moisture.

(3)   Un-reacted Fuel: Although the quantities of hydrogen used will be low, the system must not release combustible amounts of hydrogen in the exhaust.

c.                   Heating:

A heating device is needed to heat the incoming gas up to reaction temperatures.

 i.               Operating principles: The mechanism by which   a SOFC operates is ionic transport.

 ii.              Ionic transport in SOFC’s only occurs at high temperatures.

iii.             The heating system must provide uniform heating throughout the unit.

iv.              Temperature Measurement: Type K Thermocouples are needed to determine the temperature at the reaction zone, and at the gas inlets and outlets.

(1)   Must be able to measure temperatures in the range of 800°C-1000°C.

B.     Operational Requirements

a.                  Safety:

Whenever a highly combustible gas such as hydrogen is used in an engineering operation, safety should be the paramount concern.

i.                     Code Adherence: All of the safety regulations and codes regarding small-scale hydrogen use will have to be researched and followed.

ii.                   Fire Safety: The operating temperature of the unit is well above the auto-ignition temperature of hydrogen. Adequate sealing and cooling of exit gases is extremely important to the safety and success of the project.

 b.                  Life Span:

Operational life of the testing device should be as long as possible.

i.                     Timescale: Research efforts are planned to continue for a period of years

ii.                   Materials Considerations: Materials must be chosen to accommodate a sustainable life.

(1)   Most metals do not have a long life span at very high temperatures.

(2)   Ceramics are difficult to work with but have excellent temperature resistance.

 c.                   Demonstration:

The unit must be able to use the power it generates to operate some type of electrical device.

i.                     Type of Device: The device will have to have low power requirements

ii.                   Power Conditioning:  Depending on the device chosen, some conditioning of the generated power may be necessary, such as conversion to a specified current or voltage, or from DC output to AC.

iii.                  Visual Aids: May incorporate integrated measuring devices like dials indicating power or voltage output.

d.                  Data Acquisition:

Monitoring equipment is needed to determine the current and voltage produced by the fuel cell. 

i.                     Power Collection system: Current collection must first be done in the high temperature environment of the reaction using an appropriate temperature resistant, conductive material.

(1)   Both the cathode and anode side of each fuel cell must have electrical connections capable of withstanding an extremely high temperature.

ii.                   Data Acquisition system: Current and voltage will need to be measured using an external variable resistance to adjust the amount of current extracted from the fuel cell and record the corresponding voltage.

 C.     Cost Requirements

 a.                  Budget:

The final cost of the testing facility must not exceed $2000.00

i.                     Raw Materials: Ceramics, metals, wiring, insulation and other such raw materials not supplied by the customer will need to be purchased.

ii.                   Supplies: Goods such as gages, the demonstration device, and any other manufactured products that need to be purchased.

iii.                  Fabrication: Machining, and fabrication of any special parts such as the reaction chamber, fuel cell support structure, and seals.

  Back to the Top