Basics of Renewable Energy Supply - Renewable Energy: Technology, Economics and Environment - page 44

520 520

Maximum value
Standard deviation
Mean value
Standard deviation
Minimum value

Maximum value
Standard deviation
Mean value
Standard deviation
Minimum value 480 480

440 440

400 400

360 360

320 320

Hamburg Hamburg Braunschweig Braunschweig

W ürzburg W ürzburg Hohenpeißenberg Hohenpeißenberg

280 280

1961 1961 1966 1966 1971 1971 1976 1976 1981 1981 1986 1986 1991 1991 1996 1996

Time in years Time in years

Fig. 2.15 Annual totals of global radiation exemplarily for four different sites in Germany
between 1961 and 1998 (data see /2-12/)

Fig. 2.16 shows the course of the monthly mean totals of the global radiation over
thirty years, using the example of the stations shown in Fig. 2.15. With reference
to Fig. 2.15 the mean values, the standard deviation, as well as, the minimum and
the maximum values are also shown here. Together with the seasonal dependence
of the solar radiation supply, the summer months are mostly characterised by lar-
ger fluctuations in solar radiation supply than the winter months.
The solar radiation is additionally characterised by a distinctive daily course.
Fig. 2.17 therefore shows the mean diurnal course of the mean hourly radiated
power for various months, using the example of two sites in Germany for the av-
erage over 10 years.
The figure shows the known typical course of the day, with an increase in the
solar radiation supply during the morning hours, a maximum at mid-day and a
decrease in the hours of the afternoon and the evening. The radiation maxim, the
daily radiation time, and thus the areas surrounded by the curves showing the
incident daily radiation, are at the peak during the summer months. During the
winter, they are at a correspondingly low level. This characteristic might change
depending among others on the latitude of the site. Analyses of the global radia-
tion of locations in the southern hemisphere (e.g. Australia, Chile) reveal that
global radiation reaches its peak during the winter months and becomes signifi-
cantly lower during summer.