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