The Resources of the Earth - Thanatia: The Destiny of the Earth's Mineral Resources - page 134

Table 6.1 World energy use in 1984 (Hall et al., 1987)

Fuel
source

Current use
(EJ/y)

Proven re-
serves (EJ)

Resources
(EJ)

Resource
uncertainty

Coal 97.6 21,500 238,000 20%

Oil 127.3 4,300 10,000 -30% + 60%

Gas 63.1 3,700 10,000 -40% + 70%

Uranium 12.6 813 1,324 50%

- resource fi-
gure assumes
<$130/kg (re-
serves 20%)

Tar
sands+Oil
shale

- 550+ 1,600+ highly uncer-

tain

Approx.
total

300.6 30,850+ 260,900+

Fluxes
(EJ/year)

Practical Ultimate

potential

Hydro 21.7 100 200 little

uncertainty

Biomass 47 80 720 highly

uncertain

Wind v. small 30 100 speculative

Photovoltaic v. small infinite infinite rapidly

reducing price

Geothermal 0.1 large large

Approx.
total

63.8 210 1,020+

Overall
total

368.4

In the next sections, the numbers given in table 6.1 are updated and new figures
are provided for additional resources. The results are summarised in Sec. 6.7.

6.3 The energy balance

The sun is the main source of energy sustaining life on Earth. According to Skinner
(1986) and his later work (Skinner et al., 1999) the sun sends around 17:310 16 W
of power in the form of short-wavelength radiation towards the Earth. From this,
approximately 30% is directly reflected by clouds and the planetary surface. Most
rays thus pass through the atmosphere heating the Earth. These are responsible for
the generation of winds, ocean currents, rain and snowfall. Such phenomena lead
to a progressive depreciation of energy quality and therefore exergy losses. The
devaluated energy in form of heat is sent back to space and the Earth's surface re-
mains in thermal balance. A proportion of solar radiation is used for photosynthesis
and is temporarily stored in the biosphere as organic matter and eventually as a
fossil fuel: coal, oil or natural gas. Another small fraction of solar-derived energy
is stored in freshwater and saline reservoirs such as lakes, rivers and seas. But the