Class Activity 4

Question 1

Explain why fuels(hydrogen and oxygen) for the alkaline fuel cell(AFC) must be very pure with respect to reactive contaminants, such as carbon monoxide and carbon dioxide ?

Answer 1

> Carbon dioxide will react with the electrolyte to give potassium carbonate, which will cause the efficiency of the AFC to deteriorate rapidly

> The cost of removal of carbon dioxide from the air source will render the AFC uneconomical for normal commercial reasons

Question 2

Discuss the advantages and disadvantages of Solid Polymer Fuel Cells(SPFC) and Molten Carbonate Fuel Cells(MCFC)

Answer 2

SPFC:

ADVANTAGES

• Can be started up quickly and reach full power in short time
• Respond very fast to changes in demand for power

DISADVANTAGES
-Electrode kinetics are slow and expensive noble metal catalysts are required

MCFC:

ADVANTAGES

• Improved efficiency
• They are more resistant to impurities(are not prone to carbon monoxide or carbon dioxide “poisoning”

DISADVANTAGES
-Durability: The high temperature at which these cells operate and the corrosive electrolyte used, accelerate component breakdown and corrosion, decreasing cell life

Question 3

State three objective of the Life Cycle Assessment

Answer 3

1. To provide as complete a picture as possible of the interactions of an activity with the environment
2. To identify major environmental changes and life cycle stages contributing to these impacts.
3. To compare environmental impacts of alternative products, processes, or activities.