Basics of Renewable Energy Supply - Renewable Energy: Technology, Economics and Environment - page 31

thus originates from the sun (over 99.9 %). Planetary gravitation and motion as
well as geothermal energy additionally only account for approximately 0.022 % of
the energy balance. The global use of primary energy from fossil biogenous and
fossil mineral energy reserves and resources adds a further 0.006 % or approxi-
mately 413 EJ (2005) per year (see /2-38/).
Sun radiation incident on the earth every year is around 5.6 10 24 J. Around
31 % of this radiation is directly reflected back into space at the surface of the
atmospheric rim. The remaining 69 % enters the atmosphere. A larger part reaches
the surface of the earth, whereas a smaller part is absorbed within the atmosphere.
A small part (on average approximately 4.2 %) of the radiation that reaches the
surface of the earth is immediately reflected back into the atmosphere. The major-
ity of the radiation that reaches the surface of the earth is available for evapora-
tion, convection and radiation. It is to this end turned into long-wave heat radia-
tion and as so, radiated back into space. A small part of the radiation reaching the
earth's surface is converted into organic matter through photosynthesis.

Solar radiation

Irradiation

5.6 10 J/a = 100 %

24

64.8 %
Long wave
irradiation

31 % Reflection

Upper limit of the atmosphere

69 %

Geothermal heat 0.02 %

Atmospheric absorption
17.4 %

Tides

Planet gravitation
and motion

0.002 %

4.2 % Reflection

0.006 %

Surface of the earth 47.4 %

14.4 %

33 %

b

Biomass

0.1 % Energy reserves

Fossil biogenous

21

approx. 32.9 10 J

Fossil mineral

Continents Oceans

24 a

approx. 4.4 10 J

2.7 %
17.8 %

12.5 %

5.4 %

Radiation 17.9 %
Evaporation 20.7 %
Convection 8.8 %

2.9 %

6.1 %

Fig. 2.6 Energy balance of the earth ( a for this example only nuclear fission using breeder
technology (1.5 TJ/kg uranium), additionally - not presented here - fusion would be possi-
ble; b global use of primary energy - i.e. fossil biogenous and fossil mineral energy carriers
- of approximately 413 EJ per year in 2005 /2-38/; according to different sources)

Thus, there is almost a balanced situation between the energy input and output
on the surface of the earth. But an insignificantly higher amount of energy is
added than withdrawn because part of the energy is stored as biomass. If this or-
ganic sub-stance is not decomposed organically, burnt or converted in any other
way by human beings it can be converted into fossil biogenous energy carriers