Future Transportation Systems - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 270

Table 17.3 Full chain consideration of energy production for vehicles
Well-to-wheels
Well-to-tank
(WTT, fuel chain)

Tank-to-wheels
(TTW, vehicle)

Production Transportation Fuel processing Transport Distribution End use

Crude oil
drilling
and
pumping

Crude oil
pipelines,
tankers,
trains, and
trucks

Petroleum
refineries

Gasoline
pipelines,
tankers,
and tanks

Trucks and
refueling
stations

Internal
combustion
engine
vehicles

Wind
energy
station

Frequency
rectifiers

H 2 production
and storage
systems

Electric grids Connectors Electric

motor
vehicles

oxygen. Experimental electric cars with hydrogen fuel cells and electric motors
produce 100 kW (94.79 BTU s -1 ) and have a range of 450 km (280 mi). The
current is stored in a lithium-ion battery which powers an electric motor. A tank
holds about 4 kg (8.31 lb) of compressed hydrogen [ 23 ].
Hydrogen has two main benefits. Its mass-specific energy content is three times
higher than gasoline and it produces water in the exhaust of the combustion.
However, production of pure hydrogen from water through hydrolysis requires
high energy. Hydrogen produced from natural gas by hydrocracking is not an
environmentally friendly production process.
Future generations of alternative energy will also improve hydrogen produc-
tion, primarily through the use of wind power; see Table 17.3 [ 24 ].
The range of hydrogen-powered cars is further and the refueling time is shorter
than of average battery powered electric cars. However, the storage of hydrogen is
difficult and dangerous because its tiny molecules escape from almost every
pressure vessel. These problems do not exist with liquid hydrogen. Hydrogen
becomes liquid at minus 253C(-487F). This very low temperature is produced
by cryogenization, which is an expensive energy-consuming process.
Hydrogen fuel cell technology needs a few more years of development until the
cells are cheaper and convenient enough to be mass marketed. The attainable energy
densities of electricity stored in batteries or of hydrogen stored in fuel cells cost about
0.01 kWh Euros -1 , i.e., 0.009 BTU s -1 Euros -1 . In comparison, the gasoline
energy density costs approximately 6 kWh Euros -1 , i.e., 5.69 BTU s -1 Euros -1

[ 25 ], i.e., it is more economic.
According to experiences, it is not possible to replace fossil fuels such as
gasoline, diesel, kerosene, or heavy marine diesel oil in the transportation of
passengers and goods by known alternatives within the next decades. Alternative
energy carriers and fuels will come slowly and replace fossil fuels only in a small
sector of the market.