Page 74 - Energize July 2022

TECHNICAL

Fuel cells offer reliable, high quality

power today and for the future

With the increasing use of natural gas as a lower carbon energy source and the future potential of
readily available green hydrogen, fuel cells have become an important component in the energy sector,
both for energy generation and transport. Fuel cells are used for both primary and standby power

generation, in systems requiring reliable power.

by Mike Rycroft, Energize

ydrogen is the ultimate choice of fuel for fuel cells and is
considered a clean technology since it has a less polluting
Hnature and produces water, an environmentally benign
product. Hydrogen may be stored for prolonged periods of time,
making it ideal for use as a balancing power source for intermittent
renewable energy. Fuel cells are a more efficient converter of
hydrogen to energy than internal combustion engines.
Green hydrogen is still a way off in the future, and at the
current state of development, natural gas is the fuel of choice for
all types and usage of fuel cell, due to the increased availability of
gas and the development of integrated reforming devices which
produce hydrogen from natural gas at the fuel cell level.
The use of fuel cells as a reliable clean power source in
industrial and commercial applications is increasing. Some
countries are promoting the use of natural gas fuel cell /CHP
(FC-CHP) systems for domestic use and have developed specific
systems with this application in mind.
Figure 1: Basic fuel cell structure
Structure
The basic structure of a fuel cell is shown in Figure 1. Reactions
The basic reaction in a fuel cell is that of combining hydrogen
Fuels cells contain three components: and oxygen to form water. The reaction is exothermic, i.e., it
• The anode, (negative terminal) consisting of catalytic conductive produces heat, which may be discarded, used in the conversion
material or fuel reformation process, or used in other processes. The
• The cathode, (positive terminal) consisting of catalytic conductive fact that heat is produced as part of the reaction results in a
material low electrical efficiency, typically below 60%. When used in a
• The electrolyte, which can have one of four forms, and which combined heat and power (CHP) application, overall efficiency
defines the type of fuel cell: can exceed 80%.
- Liquid conductive solution at low temperature (<100°C)
- Proton exchange membrane (PEM)
- Conductive molten salt at a high temperature
- Conductive solid oxide at a high temperature

The type of electrolyte determines the ion transfer mechanism in
the fuel cell.
Fuel cell units will typically consist of a stack of cells combined
in series and parallel to give the required voltage and current.
Figure 2 shows a typical fuel cell stack. Figure 2: Fuel cell stacks (Fuelcellstore)

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