Solar Energy Perspectives - IEA

Solar Energy Perspectives: The solar resource and its possible uses
Roughly half of the radiation scattered is lost to outer space, the remainder is directed
towards the earth’s surface from all directions (diffuse radiation). The amount of energy
reflected, scattered and absorbed depends on the length the sun’s rays must travel, as well as
the levels of dust particles and water vapour – and of course the clouds – they meet. Smaller
cosine effect and air mass make the inter-tropical zone sunnier than others. However, the
global radiation reaching the earth’s surface is much stronger in arid or semi-arid zones than
in tropical or equatorial humid zones (Figure 2.7). These zones are usually found on the west
sides of the continents around the tropics, but not close to the equator.
Figure 2.7 The global solar flux (in kWh/m 2 /y) at the Earth’s surface over the year (top),
winter and summer (bottom)
180 o
W 90 o
W 0 o
90 o
E
60 o
N
30 o
N
0 o
30 o
S
180 o
E
2 500 kWh/m 2 /y
2 250 kWh/m 2 /y
2 000 kWh/m 2 /y
1 750 kWh/m 2 /y
1 500 kWh/m 2 /y
1 250 kWh/m 2 /y
1 000 kWh/m 2 /y
750 kWh/m 2 /y
500 kWh/m 2 /y
60 o
S
40 80 120 160 200 240 280 320 40 80 120 160 200 240 280 320
December, January, February
June, July, August
Sources: (top) Breyer and Schmidt, 2010a; (bottom) ISCCP Data Products, 2006/IPCC, 2011.
Key point
Global solar irradiance is good to excellent between 45° South and 45° North.
The average energy received in Europe is about 1 200 kWh/m 2 per year. This compares, for
example, with 1 800 kWh/m 2 to 2 300 kWh/m 2 per year in the Middle East. The United
States, Africa, most of Latin America, Australia, most of India and parts of China also have
good-to-excellent solar resource. Alaska, northern Europe, Canada, Russia and South-East
China are somewhat less favoured. It happens that the most favoured regions are broadly
38
© OECD/IEA, 2011