From Stack to Fuel Cell System Level

Question 1

BoP (Balance of Plant) systems required

Answer 1

1. Thermal management
2. Reactant Supply
3. Power management
4. Water management

Question 2

Influence of Temperature in the different properties of a cell

Answer 2

1. If we increase temperature, also increase:
   A. Kinetics (reduction of activation losses)
   B. Ionic Conductivity (reduction of ohmic losses)
   C. Corrosion
2. If we increase temperature, decrease:
   A. Nerst voltage

Question 3

Liquid cooling: Layout, properties and requirements for coolant

Answer 3

1. Layout: Presentation 2 Slide 81
2. Properties:
   A. Wasted heat transferred to coolant
   B. Coolant flows through cooling channels between cells
   C. Effective cooling
3. Requirements for coolant:
   A. High heat capacity and thermal conductivity
   B. Needs to sustain full range of application

Question 4

Air cooling: properties

Answer 4

1. Wasted heat transferred to air flow
2. Lightweight
3. Less effective than liquid cooling

Question 5

Phase Change Cooling: properties

Answer 5

1. Coolant absorbs latent heat during phase change
2. Simple system

Question 6

Name the 3 types of cooling in a Fuel Cell System

Answer 6

1. Liquid cooling
2. Air cooling
3. Phase change cooling

Question 7

When increasing the pressure, what happens with the next of the properties in a Fuel Cell System?

Answer 7

All of them increase

Question 8

Definition and formula of ‘fuel efficiency’

Answer 8

Definition: How much of the energy stored in the fuel is actually used for generating electrical energy.

Formula: cell efficiency x fuel utilization = cell efficieny/stochiometry

–> Basically in here is the same as in past topics; fuell efficiency = output(electrical energy)/Heat Value (LHV or HHV)

Question 9

Water management in PEFC
Why is it produced and for which goal?
Important things to take into account.

Answer 9

1. It is produced in the cathode, as a product
2. The proton exchange membrane in the PEFC needs to be humid for adequate proton conductivity
3. We need to ensure:
   A. Enough water at every point of the membrane
   B. Avoidance of flooding of electrode pores due to excess water
   C. Avoidance of humidification gradients through cell

Question 10

Relative Humidity. Definition and formula

Answer 10

Defintion: Ratio of partial pressure of water and saturation water pressure at given T
RH = p(H2O)/p(H2O,sat)

–> It is really dependant on T

Question 11

Reactant Management vs. Fuel Cell Type

Answer 11

Table