Hydrogen
245
source of energy, but rather a convenient tool for handling energy. In many
respects an illustrative parallel may be drawn to electricity, which is also not
a source of energy, but instead an appropriate intermediate in energy transport and conversion.
The production of industrial hydrogen is currently based mainly on fossil
fuels, but to some extent electricity is also used. If considered as an alternative fuel, hydrogen should not be produced from fossil fuels, since this
would not lead overall to decreased emissions of greenhouse gases (GHGs).
Hydrogen is a very attractive transportation fuel in two important ways. It
is the least polluting fuel (as it does not contain carbon) that can be used in
an internal combustion engine (ICE), and it is potentially available anywhere
there is water and a clean source of power. Hydrogen-fueled internal combustion engines (H 2 -ICEs) operate as clean and efficient power plants for automobiles. Hydrogen produces water only when it is combusted in the ICE and
makes it a very environmentally clean fuel. Hydrogen combustion does not
produce any of the major pollutants such as CO, HC, SO x , smoke, lead, or
other toxic metals except NO x . Sulfuric acid deposition, benzene and other
carcinogenic compounds, ozone and other oxidants, are intrinsically absent
in a well-designed neat hydrogen engine.
A special reason for the technological interest in hydrogen is that hydrogen
works very well within fuel cells. Most fuel cells are basically powered by
hydrogen, even though the primary fuel is not always pure hydrogen. Using
hydrogen in a fuel cell leads to optimized energy efficiency (for the conversion of chemical to mechanical energy) compared with use of hydrogen in an
ICE. Conversion efficiencies approaching 70% may be possible (significantly
depending though on operation mode and conditions) and this is at least
two times better than the conversion efficiency observed for ICEs. In this
chapter the hydrogen production, fuel properties, how to use gaseous fuel in
vehicles, storage, safety, and challenges associated with hydrogen economy
are discussed.
9.2 Hydrogen: Energy Carrier
9.2.1 Need for energy Carriers
The available energy sources on earth are: nuclear reactions; sun radiation
(directly or indirectly considering that wind and water receive energy for
their movement by sun radiation); and fossil fuels. They are considered in
this document as primary energy sources. Hydrogen is not among them.
Potential energy from primary sources need to be converted into other
forms to be of use. The most important energy forms for their final use by
mankind are: thermal energy (used for heating); mechanical energy (for
245
source of energy, but rather a convenient tool for handling energy. In many
respects an illustrative parallel may be drawn to electricity, which is also not
a source of energy, but instead an appropriate intermediate in energy transport and conversion.
The production of industrial hydrogen is currently based mainly on fossil
fuels, but to some extent electricity is also used. If considered as an alternative fuel, hydrogen should not be produced from fossil fuels, since this
would not lead overall to decreased emissions of greenhouse gases (GHGs).
Hydrogen is a very attractive transportation fuel in two important ways. It
is the least polluting fuel (as it does not contain carbon) that can be used in
an internal combustion engine (ICE), and it is potentially available anywhere
there is water and a clean source of power. Hydrogen-fueled internal combustion engines (H 2 -ICEs) operate as clean and efficient power plants for automobiles. Hydrogen produces water only when it is combusted in the ICE and
makes it a very environmentally clean fuel. Hydrogen combustion does not
produce any of the major pollutants such as CO, HC, SO x , smoke, lead, or
other toxic metals except NO x . Sulfuric acid deposition, benzene and other
carcinogenic compounds, ozone and other oxidants, are intrinsically absent
in a well-designed neat hydrogen engine.
A special reason for the technological interest in hydrogen is that hydrogen
works very well within fuel cells. Most fuel cells are basically powered by
hydrogen, even though the primary fuel is not always pure hydrogen. Using
hydrogen in a fuel cell leads to optimized energy efficiency (for the conversion of chemical to mechanical energy) compared with use of hydrogen in an
ICE. Conversion efficiencies approaching 70% may be possible (significantly
depending though on operation mode and conditions) and this is at least
two times better than the conversion efficiency observed for ICEs. In this
chapter the hydrogen production, fuel properties, how to use gaseous fuel in
vehicles, storage, safety, and challenges associated with hydrogen economy
are discussed.
9.2 Hydrogen: Energy Carrier
9.2.1 Need for energy Carriers
The available energy sources on earth are: nuclear reactions; sun radiation
(directly or indirectly considering that wind and water receive energy for
their movement by sun radiation); and fossil fuels. They are considered in
this document as primary energy sources. Hydrogen is not among them.
Potential energy from primary sources need to be converted into other
forms to be of use. The most important energy forms for their final use by
mankind are: thermal energy (used for heating); mechanical energy (for