Power Plant Engineering

NON-CONVENTIONAL ENERGY RESOURCES AND UTILISATION 73

2.17 Electrochemical Effects and Fuel Cells

Fuel cells produce electricity from an electrochemical reaction between hydrogen and oxygen.
Fuel cells are efficient, environmentally benign and reliable for power production. The use of fuel cells
has been demonstrated for stationary/portable power generation and other applications.
Fuel cell is device that converts the chemical energy stored in a fuel directly to electrical energy.
Fuel cell is an open system.

+

H 2

O 2

HO 2

Fuel

Cell

Fig. 2.16

Some similarity to a battery except that energy must be stored or built into a battery. Batteries

are closed systems.

Battery

+

Fig. 2.17

There are two Principles of the fuel cell

1. Chemo electricity
   — Chemistry must occur before energy flows
   — F/C system like an entire chemical plant


2. Match Energy Source to Application
   — Stationary/Vehicle/Portable
   — Sometimes F/Cs won’t work.

2.17.1 Reversible Cells

Since oxidation and reduction are physically separate, two things must happen to complete the

reaction in a fuel cell:

1. Ions travel through electrolyte:
   — acidic f/c: cations to cathode
   — alkaline f/c: anions to anode


2. Electrons travel anode to cathode electrons fall through ‘‘potential gradient’’ and thus do
   work.