Hydrogen
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Finally, there is no longer the need for FC optimization during the cycle
because the generator efficiency curve matches in a better way to the energy
use during urban cycles. Indeed, in comparison to a thermal motor, the peak
is more toward the middle–low power and therefore it is better adapted to
urban cycles. However, the fuel–cell system could still benefit from some size
reduction to prevent excessive operation at light load or on/off operation due
to minimum power requirements.
In conclusion, if the power required by the motor is shared between
two devices, an economic benefit from cost reduction exists as storage
devices are heavier but cheaper than fuel cells, particularly when the ratio
of peak power/average power is high. The management (fuel) cost also is
reduced when compared with a full-power system since braking energy
recovery can also be performed. This is particularly true in those applications (urban transportation) where braking is very frequent and therefore
the braking energy recovered is likely larger than the energy loss of the
storage.
9.10 Hydrogen in Spark Ignition Engines
Hydrogen can be used in spark-ignition ICEs in a way that is very similar to
gasoline use in ordinary engines. The use of ICEs with hydrogen produces
very few pollutant emissions. This is due to two factors:
• In theory, nitrogen oxides (NO x ), coming from the oxidation of atmospheric nitrogen are the only undesirable emissions produced by
this engine.
• Low explosion limit of hydrogen allows a stable combustion, even
under diluted conditions. Even with a mix of a small percentage
of hydrogen with air, the temperatures of combustion are low and
the speed of NO x formation is low. The explosion limit of hydrogen
also contributes to good engine output with hydrogen under weak
loads.
Moreover, H 2 ICEs seem to be efficient. BMW obtained an efficiency of 37.5%
with its car. Therefore, the characteristics of hydrogen combustion seem
to allow an efficient and environmental friendly propulsion system. This
advantage could be obtained with very reasonable costs, at today’s prices
well below those of fuel-cell based electricity generators. Current research
efforts aim at developing hydrogen ICEs with improved power densities and
reduced NO x emissions under higher loads.
267
Finally, there is no longer the need for FC optimization during the cycle
because the generator efficiency curve matches in a better way to the energy
use during urban cycles. Indeed, in comparison to a thermal motor, the peak
is more toward the middle–low power and therefore it is better adapted to
urban cycles. However, the fuel–cell system could still benefit from some size
reduction to prevent excessive operation at light load or on/off operation due
to minimum power requirements.
In conclusion, if the power required by the motor is shared between
two devices, an economic benefit from cost reduction exists as storage
devices are heavier but cheaper than fuel cells, particularly when the ratio
of peak power/average power is high. The management (fuel) cost also is
reduced when compared with a full-power system since braking energy
recovery can also be performed. This is particularly true in those applications (urban transportation) where braking is very frequent and therefore
the braking energy recovered is likely larger than the energy loss of the
storage.
9.10 Hydrogen in Spark Ignition Engines
Hydrogen can be used in spark-ignition ICEs in a way that is very similar to
gasoline use in ordinary engines. The use of ICEs with hydrogen produces
very few pollutant emissions. This is due to two factors:
• In theory, nitrogen oxides (NO x ), coming from the oxidation of atmospheric nitrogen are the only undesirable emissions produced by
this engine.
• Low explosion limit of hydrogen allows a stable combustion, even
under diluted conditions. Even with a mix of a small percentage
of hydrogen with air, the temperatures of combustion are low and
the speed of NO x formation is low. The explosion limit of hydrogen
also contributes to good engine output with hydrogen under weak
loads.
Moreover, H 2 ICEs seem to be efficient. BMW obtained an efficiency of 37.5%
with its car. Therefore, the characteristics of hydrogen combustion seem
to allow an efficient and environmental friendly propulsion system. This
advantage could be obtained with very reasonable costs, at today’s prices
well below those of fuel-cell based electricity generators. Current research
efforts aim at developing hydrogen ICEs with improved power densities and
reduced NO x emissions under higher loads.