New trends in physics teaching, v.4; The ... - unesdoc - Unesco

The energy cris@
TABLE 7. United States coal resource. Units are lo9 tonnes.
Ultimate total production [6]
High estimate 1486
Low estimate 390
Produced through 1972 (My estimate from Hubbert’s Figure 22)
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Percentage of ultimate production produced through 1972
Percentage of high estimate 3%
Percentage of low estimate 13%
Coal resource remaining
High estimate 1436
Low estimate 340
Annual production rate, 1972 0.5
Rate of export of coal, 1974
0.06
Annual production rate, 1974 0.6
Annual production rate, 1976 0.665
Table 8 shows the EETs of the high and low estimates of United States coal reserves for various
rates of increase of the rate of production as calculated from Eq. (6). If we use the conservative
smaller estimate of American coal reserves, we see that the growth of the annual rate of consumption
will have to be held below 3 per cent if we want coal to last until 2076 A.D. If we want coal
to last 200 years, the rate of growth of annual consumption wil have to be held below 1 per cent.
TABLE 8. Lifetime in years of United States coal (EET). The lifetime (EET) in years of United States coal
reserves (both the high and low estimate of the United States Geological Survey - USGS) are shown
for several rates of growth of production from the 1972 level of 0.5 X lo9 tonnes per year.
Zero
1%
2%
3%
4%
5%
6%
7%
8%
9%
1 W O
11%
12%
13%
High Estimate (yr)
2872
339
203
149
119
99
86
76
68
62
57
52
49
46
Low Estimate (yr)
680
205
134
102
83
71
62
55
50
46
42
39
37
35
One obtains an interesting insight into the problem if one asks how long beyond the year 1910
could coal production have continued on the curve of exponential growth at the historic rate
6.69 per cent per year of figure 3. The smaller estimate of United States coal would have been
consumed around the year 1967 and the larger estimate would have expired around the year
1990. Thus it is clear the use of coal as an energy source in 1980 and in the years to come is
possible only because the growth in the annual production of coal was zero from 191 0 to about
19 72!
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