Environmental Engineering Reference
In-Depth Information
Final energy
electricity
34% (175 Wh)
Heating water
19%
(97 Wh)
Effective energy
Primary energy source
e.g. coal
100%
(3515 Wh)
Waste heat
of power plant
66%
(340 Wh)
Waste heat
of cooker
15%
(78 Wh)
Figure 1.3
Energy Conversion Chain and Losses for Water Heating with an
Electric Cooker
losses of the electrical transmission system (see Figure 1.2). Therefore, the
primary energy consumption of the electric stove of 515 Wh = 1980 kJ is 65
per cent higher than that of the gas stove, although the final energy
consumption is more than 30 per cent below that of the gas stove. This
example is summarized in Figures 1.2 and 1.3, in which the energy conversion
chain is compared for the electric and gas stove. The gas stove is the most
economical appliance when comparing the primary energy demand, and it is
the primary energy demand that determines the environmental impact.
E
VOLUTION OF
W
ORLD
E
NERGY
D
EMAND
Coal and crude oil were not relevant as energy supplies at the end of the 18th
century. Firewood and techniques for using wind and hydro power provided
the entire energy demand. Watermills and windmills were common features of
the landscape during that time.
In 1769 James Watt laid the foundations for industrialization by
developing the steam engine. The steam engine, and later the internal
combustion engine, swiftly replaced mechanical wind and water installations.
Coal became the single most important source of energy. In the beginning of
the 20th century, crude oil took over as it was needed to support the increasing
popularity of motorized road traffic. Firewood lost its importance as an energy
supply in the industrial nations, and large hydro-electric power stations
replaced the watermills.
The world energy demand rose sharply after the Great Depression of the
1930s. Natural gas entered the scene after World War II. In the 1960s, nuclear
power was added to the array of conventional energy sources. These relatively
new sources have not yet broken the predominance of coal and crude oil, but
gas is the energy carrier with the fastest growth. The share of nuclear electricity
of today's primary energy demand is still relatively low. The fossil energy
sources - coal, crude oil and natural gas - provide more than 85 per cent of
the world primary energy demand.
