Page 33 - Vol 33 Issue 34 2021

Solar energy energy

you can. To achieve that you position the panel Atmosphere Africa is on a plateau between 1000-2000 metres
so that it blocks the path of as many photons as above sea level. For example, at 1750 m above
possible. That happens when the panel directly Unlike many of the world’s arid regions, like the sea level, the city of Johannesburg has about
faces the sun. Sahara and parts of central Asia, the southern 15% less atmosphere above it than a coastal
A panel lying flat on the ground therefore African dry areas experience comparatively low location. It means that even under the clearest
maximises its photon catch when the sun is di- levels of dust. One result is good long-range vis- sky conditions sites on the plateau receive slightly
rectly overhead. At noon the sun is closest to ibility: light is able to move through the at mos- more solar photons than coastal sites do.
over head in the tropics, so these latitudes also phere freely.
ge nerally have the warmest climate. Dust, smoke and haze in the atmosphere block Southern Africa - a solar
part of the sunlight, like clouds do. While some
Climate of these conditions do occur for limited periods, hot spot?
the atmosphere over southern Africa generally All these factors create excellent conditions
There is a common misconception that the has lower aerosol concentrations than in many for the generation of solar energy in much of
hottest areas are also most suited for solar power other parts of the planet. Southern Africa. Even the coastal, cloud prone
generation. But tropical regions often have a lot of This is partly due to the large oceans on three lo ca tions have enough sunshine to match
cloud as well. Coastal areas also tend to be more sides of the region, which limits the importation most of the solar power generating sites in the
cloud prone, and so some of the warmest cities of air contaminants from other continents. northern hemisphere industrialised countries.
in southern Africa, such as Durban (eThekwini) in And the western interior, with its extremely low
South Africa or Maputo in Mozambique, are not High altitude cloud cover, high altitude and low aerosol con-
top solar sites. centrations, offers some of the best conditions in
Around the northern and southern edges It is not only the contaminants in the air that block the world for solar energy.
of the tropics we find regions with some of the light, but to a small degree also clean air itself. Southern African countries have been slow in
driest climate, which normally implies less cloud About 20% of incoming photons from the sun’s embracing solar energy. Ten years ago, the cost
cover. In southern Africa, these arid regions are vertical beam that could be processed by solar was still prohibitive, but not anymore. Many new
the Namib, Kgalagadi and Karoo (semi)deserts panels do not make it all the way to the ground. initiatives are springing up in practically all parts of
and adjacent areas. These experience the sun The percentage gets even larger as the sun nears the region. It is a trend that is set to continue and
nearly overhead around noon in the summer. the horizon, when photons are taking a longer get even stronger. (Courtesy of The Conversation)
Solar devices here can catch more energy in path through the atmosphere.
winter by tilting slightly towards the equator. This is another reason why latitudes closer Hartmut Winkler, Professor of Physics, University of
In southern Africa, solar panels usually perform to the poles become ever less suitable sites for Johannesburg
best if they are tilted 20-30 degrees towards the solar energy generation. The sun there never
north, meaning that they directly face the noon gets close to a point vertically above. In southern
sun during the March and September equinoxes. Africa, however, with latitudes between about
Those angles also closely match the inclination 15 and 35 degrees south, the sun is on average
angles of a typical domestic roof - so solar panels closer to the zenith. That makes higher solar
lying flat on a north-facing roof are often already energy yields possible.
at their optimal tilt. Another advantage is that much of southern

AFRICAN POWER Mining & Oil Review Vol33 Issue 34 2021 | 33