Page 20 - Geothermal Energy Renewable Energy and The Environment

2 Geothermal Energy: Renewable Energy and the Environment

The use of fire to support life and industry is dependent upon a fuel source. The ability to access,
control, and maintain a source of fuel is a prerequisite for supporting industrial activity and economic
growth. As a result, discussions about energy have become inextricably linked with the necessity
that a fuel source exists to support energy production. When fuel is readily available and the popu-
lation competing for it is relatively small, growth and development are not constrained by the fuel
source. Population growth and technological evolution, however, have changed this condition.

The impacT of populaTion GrowTh and per capiTa enerGy use
Plotted in Figure 1.1 are two trends that demonstrate the nature of the challenge posed by
population growth and energy demand. One important fact is that the population of the planet
has been growing exponentially. Between 1850 and 2006, the population increased from about
1.3 billion to about 6.5 billion, an increase of five times. Current estimates are that, between the
years 2000 and 2050, the population will grow from about 6.1 billion to about 8.9 billion, an
increase of 47% in 50 years (United Nations 2004). Although this projected growth rate is slower
than it has been historically, it does demonstrate that the population of the planet will continue
to grow at a fast pace.
The other part of Figure 1.1 shows the average use of energy per person on the planet per year.
Between the years 1850 and 2006 the average per person energy consumption increased from about
4.85 × 10 J/person/yr to over 76.2 × 10 J/person/yr, an increase of more than 15 times. In other
9
9
words, not only is the population of the planet growing rapidly, the average person is using more
energy each year than they used previously.
8.0
7.0

Joules/person/yr (×10 10 ) 6.0 8.0

5.0
4.0

3.0
7.0
2.0

1.0 6.0
5.0
(b)
0 4.0
1650 1750 1850 1950 2050 Global population (×10 9 )
Year
3.0
2.0
1.0
(a)
0
1650 1750 1850 1950 2050
Year
FIGUre 1.1 (a) Population of the planet since 1700. Population estimates for 1950 through 2006 from the
U.S. Census Bureau Web site (http://www.census.gov/ipc/www/idb/informationGateway.php). Earlier popu-
lation estimates were derived from data in Grübler, 1998. (b) Energy consumption per person since 1700.
Energy consumption through 1979 is based on data from Hafele and Sassin (1977). Data for 1980 through
2006 are from the United States Energy Information Administration, International Energy Annual 2006.