Fuel Cells - revisited

Mrs. Ullman - GE Fuel Cells - 3/1/16

Fuel cells make a useful electrical energy source or battery alternative for vehicles and homes. They benefit society by providing a method of very cleanly generating electricity using hydrogen.

Government/Economics Connections:
• Investment Tax Credit - Taxpayers can claim 30% credit of expenditures for fuel cell power plants, among others
• Fuel cells provide another government talking point for alternative energy
Presenter connections:
• Dr. Borton, Wei Ji, Scoavello  Scovello  - energy
• Dr. Borton, Dr. Katz - environment

Summary:
Mrs. Ullman talked about what fuel cells are, how they work, their history, why they are beneficial, and their different fuel sources. Fuel cells use hydrogen and oxygen along with an catalyst to influence a redox reaction that produces electricity, heat, and water. There are quite a few benefits to using fuel cells to generate electricity, including having low emissions, not being intermittent, having fuel flexibility, and being very efficient. They are quiet, run longer than batteries, don’t have to be recharged like batteries, and have high energy density. One added benefit can be “grid firming,” which essentially can create a less intermittent backbone for the renewable energy grid of the future, or even for renewable sources now.

There are quite a few different kinds of fuel cell technologies, all for different uses, that all have different advantages and disadvantages. Polymer Electrolyte Membrane (PEM) FCs have low temperatures, have solid electrolytes, and have quick startup times, to make them better suited for portable use, but they can have expensive catalysts. These can be used to power things like laptops and phones. Alkaline FCs have a wider range of stable materials, making them a cheaper alternative to PEMs, but are sensitive to CO2. These can be used to power 100kW cars and 200kW buses. Phosphoric Acid FCs are better for distributed generation, and have expensive catalysts, but an increased tolerance to impurities. Molten Carbonate and Solid Oxide FCs are great for electric utility and distributed generation, have high efficiencies, are suitable for CHP (combined heat and power), but have long startup times. Fuel cells in distributed power scenarios can be used for on-site power, substation power in the grid, power in developing regions without having to create a large network, and they can also be retrofitted for existing gas engine customers of GE.

Hydrogen can be made a number of different ways, including natural gas reforming, coal gasification, biomass gasification, renewable liquid fuel reforming, high temp water splitting, electrolysis, and through new photolytic processes. The most common method is steam methane reforming, which takes CH4 and H2O to make H2. Obviously these methods come with their own drawbacks, and they may contribute their own environmental effects. The logistics of hydrogen fuel also contribute, because refueling stations have to be built for vehicles, and fuel has to be bottled and transported. Overall, the fuel cell is a very interesting alternative energy source that has already made its way into many industries, and that will continue to grow in the future with GE’s help.

Terms:

• Fuel cell - converts chemical energy to electrical energy using a redox reaction that produces electrons and H2O
• Grid firming - account for energy changes due to intermittent energy sources such as wind and solar
• Electrodes - anode and cathode are negative and positive conductive terminals
• Electrolyte - carries charged particles from one electrode to the other
• Combined heat and power - fuel cell generating electricity as well as useful heat
• Reaction
o Anode Reaction: 2H2 + 2O2− → 2H2O + 4e−
o Cathode Reaction: O2 + 4e− → 2O2−
Overall Cell Reaction: 2H2 + O2 → 2H2O

Fuel Cells

  Fuel Cells 

   Engineers and manufacturers create fuel cells. Fuel cells are used to provide a more environmentally safe and cost effective way of powering electrical equipment than conventional batteries. In the specific case of fork lifts, fuel cells have 75% of the run time of a battery but are much quicker to fuel up then to change the batteries every few hours.  They also save space and reduce hazards at facilities that rely on fork lifts.Structure and Function:

  The membrane electrode assembly is made of 3 different layers. The MEA is sandwiched between two bipolar plates that conduct electricity between the cells and provide the cell with a strong structure. The MEA is made up of membrane, catalyst and gas diffusion layers. For the catalyst [D1] layer, platinum is applied across the polymer electrolyte membrane to facilitate the chemical reactions.  The platinum catalyst allows the hydrogen to be split into electrons and protons. The protons go through the MEA while the electrons go through a circuit where they are harnessed to do electrical work. The gas diffusion layers sit outside of the catalyst layer and  facilitate the removal of hat and water.

Fueling Stations:

-

- Most hydrogen in US comes from reforming natural gas

- Uses a small valve

- If pressure goes higher than 6600 psi, it needs pressure relief

- Made larger so they are easier to service

- Takes 2 minutes to refuel compared to 15 minutes to switch batteries

Skid

-Twenty feet skid outside at customer site -Tanks take liquid hydrogen out and compress it -All of the valving connects the tubes to the dispenser -Starts with lowest pressure first

Plastic water tank:

-Gets heavier as it runs

     -Hydrogen from tank and air from atmosphere, gains 10 lbs of oxygen while it runs

- Combines to make water

Maintenance:

- Every 6 months to a year

- Change the coolant every 10,000 operating hours

- Fix hydrogen leaks

Design verification testing

    -30*C to 40*C

    -22*F to 100*F

    -Fuel cells need to be heavy to help stabilize fork lifts (solid steel added)

Terms  :

Membrane electrode assembly

Bipolar plates

Lithium ion battery

Skid

Stacks

Fuel cells

Catalyst

Regulator

Coolant

Dispenser

Compresses

Valves

Electrolyzer

Hydroelectric

Voltage

Membrane

Diffusion

Connections:

Dr. Karatkar- lithium ion batteries

Dr. Katz- alternative energy

Dr. Borton- alternative energy

Dr. Ullal/ Palermo- polymers

Joe Imbrogno- made a membrane

Dr. Wei - conduction

Dr. Koratkar- lithium ion battery

Dr. Silva- chemical processes

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