Fuel cell

Question 1

What is a fuel cell and how does it work?

Answer 1

• The fuel cell is a device which directly converts the chemical energy of a fuel into electricity or electrical work. Not limited by Carnot efficiency
• A Fuel Cell works electrochemically, like a common battery, but with differences:
  o The battery is an energy storage system, and the amount of available energy is given by the quantity of chemical reactants stored inside
  o The Fuel Cell is an energy conversion device, which generates electricity as long as the electrodes are fed with fuel and oxidizer (air)

Question 2

What are the most important fuel cell features? (give 4)

Answer 2

• Production of electricity in direct current (DC): necessity of a DC/AC converter
• Static operation, without noise and vibrations
• “Modular” construction (large plants are composed by a number of small units; a single cell may have a power output between 10-100W up to 1-2 kW)
• Absence of combustion processes ≈ zero production of, classic pollutants (i.e. NOx) inside the fuel cell.

Question 3

What are the five fuel cell types?

Answer 3

• Alkaline (low temp)
• Polymer electrolyte (low temp)
• Phosphoric acid (low temp)
• Molten carbonate (high temp)
• Solid oxide (high temp)

Question 4

Where can hydrogen be produced?

Answer 4

1) Produced in centralized plants and distributed to FC systems (new pipelines, liquid transport …)
2) Produced locally, close to the FC plant or within the fuel cell package, depending on its origin (fossil fuels, biomass, renewables…).

Question 5

How is hydrogen generated in a low temperature fuel cell? And how in a high temperature fuel cell?

Answer 5

• In low temperature fuel cells, H2 must be generated by a dedicated plant section.
• In high temperature fuel cells, H2 can be generated with an internal reforming process, which:
  1. Exploits heat from thermal integration with the fuel cell, increasing the system efficiency
  2. Significantly simplifies the plant layout

Question 6

What is the role of the electrolyser in the Power to Gas (PtG) concept?

Answer 6

• Operating spinning reserve for electrical grid (demand site management, load balancing)
• Hydrogen production as fuel for FCEV
• Large-scale storage systems by gas injection to the NG grid grid or underground storage
• Hydrogen for industrial applications