sustainability - SUNY College of Environmental Science and Forestry

Sustainability 2011 , 3 1982

Figure 10.Depletion curve for the solar resource in the United States ranked by energy flux

density (Wh/m^2 /day) as a percentage of total land area. The quality of the solar resource

decreases exponentially.

10,000

0 10 20 30 40 50 60 70 80 90 100

2

Percent of sites

Energy Flux Density (W

h/m /day) 8000

6000

4000

2000

If we imagine the total resource being populated with identical turbines, each with a nominal constant
embodied energy cost,κ[GJ/MW] and a nominal lifetimetL[yr] in such a way as to exploit the best
sites first, the pattern of decline of the EROI as a function of total capacity installed [MW], will follow
the pattern of the power density of the sites. An analogous case may be made of the solar resource.
Brandt (in press) [10] has made a long-term study of the EROI of oil production in California between
1955 and 2005. The EROI of this oil at the mine-mouth is shown in Figure 11. An exponentially
decreasing curve is shown for comparison. The initial decline is greater than exponential.

Figure 11. EROI at the mine-mouth for California oil production between 1955 and 2005

plotted as a function of cumulative production.

0

10

20

30

40

50

60

70

80

90

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800

EROI

Cumulative Production (Mbbl)

Brandt (2010) [Mine mouth]

Error = range

Expon. (Brandt (2010) [Mine

mouth] Error = range)

G