Basics of Renewable Energy Supply - Renewable Energy: Technology, Economics and Environment - page 43

because both cities are close to the equator. But the level of the measured global
radiation is different because of unequal micro-meteorological condition.

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1 2 3 4 5 6 7 8 9 10 11 12

Time in month Time in Months

Stockholm, Sweden (59°20'N 17°03'E) Béchar, Algeria (31°38'N 2°18'W)

Kuala Lumpur, Malaysia (3°38'N 101°41'E) Manaus, Brazil (3°00'S 60°00'W)

Victorica, Argentina (36°20'S 65°30'W)

Fig. 2.14 Annual curves of measured global radiation at different sites throughout the
world (data according to different sources)

The solar radiation supply is also characterised by clear variations over several
years. This becomes apparent in Fig. 2.15 showing the annual totals for global
radiation, exemplarily for four sites in Germany, in the course of the last decades.
Additionally, the mean global radiation, the corresponding standard deviation, and
the minimum and the maximum global radiation total, are shown. From the figure,
the following conclusions can be drawn.
− Of the represented sites, the southernmost station, Hohenpeißenberg, shows the
largest mean global radiation total over several years, whereas in Hamburg, the
northernmost site, the lowest mean annual global radiation was recorded. The
high radiation total on the Hohenpeißenberg is not only due to its southernmost
location compared to all other stations, it is also due to the exposed position of
the test station (mountain station).
− Only the comparison of the standard deviations of the annual global radiation
totals at the four sites, with regard to the respective mean value of global radia-
tion, is meaningful. This shows that they are relatively similar at the four sta-
tions, with a maximal standard deviation of +/-10 %. Within Germany, the rela-
tive standard deviation of the annual global radiation totals is almost independ-
ent of the annual totals of global radiation. In principle, this is not only true for
the standard deviations, but also for minimum and maximum values.