Page 34 - Energize July 2021

VIEWS AND OPINION

Why southern Africa’s interior is an on three sides of the region, which limit the
This is partly due to the large oceans

ideal place to generate solar energy importation of air contaminants from other
continents.

by Prof. Hartmut Winkler, University of Johannesburg
High altitude
It is not only the contaminants in the air that
Southern Africa is popularly associated block light, but to a small degree also clean
with sunshine. Does that make the region air itself. About 20% of incoming photons
from the sun’s vertical beam that could be
exceptionally suited to solar energy processed by solar panels do not make it all
generation? the way to the ground. The percentage gets
even larger as the sun nears the horizon,
when photons are taking a longer path
through the atmosphere.
ith electricity shortages plaguing all parts of the sub- This is another reason why latitudes closer
continent, a plentiful energy source that is becoming to the poles become ever-less suitable sites
Wincreasingly affordable to tap into seems like an ideal for solar energy generation. The sun there
solution. Yet the rollout of solar power generating facilities has never gets close to a point vertically above.
been slow in the region. In southern Africa, however, with latitudes
Most solar power developments in the sub-continent have been in South Africa. But even between about 15 and 35° south, the sun is
here, solar farms account for only 2.5% of the total electricity generated. Compare that to on average closer to the zenith. That makes
some European countries that don’t have ample sunshine, such as Germany, where solar’s higher solar energy yields possible.
share of the total electricity generated rose above 10% last year. Another advantage is that much of
So is southern Africa, and in particular its dry interior, really among the world’s best sites southern Africa is on a plateau between 1000
for solar energy generation, as is often claimed? and 2000 m above sea level. For example,
at 1750 m above sea level, the city of
Harvesting solar energy Johannesburg has about 15% less atmosphere
Sunlight is ultimately a stream of photons. Think of photons as little arrows, each carrying a above it than a coastal location. It means that
small quantum of energy. Upon striking a solar panel or some other solar device, the photon even under the clearest sky conditions sites
will be annihilated, and a fraction of its energy will be converted to heat or electricity. on the plateau receive slightly more solar
To maximise the energy collected by the solar device, you try to intercept as many photons than coastal sites do.
photons as you can. To achieve that you position the panel so that it blocks the path of as
many photons as possible. That happens when the panel directly faces the sun. Southern Africa – a solar hot spot?
A panel lying flat on the ground therefore maximises its photon catch when the sun is All these factors create excellent conditions
directly overhead. At noon, the sun is closest to overhead in the tropics, so these latitudes for the generation of solar energy in much
also generally have the warmest climate. of Southern Africa. Even the coastal, cloud
prone locations have enough sunshine to
Climate match most of the solar power generating
There is a common misconception that the hottest areas are also most suited for solar power sites in the northern hemisphere
generation. But tropical regions often have a lot of cloud as well. Coastal areas also tend to industrialised countries. And the western
be more cloud prone, and so some of the warmest cities in southern Africa, such as Durban interior, with its extremely low cloud cover,
(eThekwini) in South Africa or Maputo in Mozambique, are not top solar sites. high altitude and low aerosol concentrations,
Around the northern and southern edges of the tropics we find regions with some of the offers some of the best conditions in the
driest climate, which normally implies less cloud cover. In southern Africa, these arid regions world for solar energy.
are the Namib, Kgalagadi and Karoo (semi)deserts and adjacent areas. These experience the Southern African countries have been
sun nearly overhead around noon in the summer. Solar devices here can catch more energy in slow in embracing solar energy. Ten years
winter by tilting slightly towards the equator. ago the cost was still prohibitive, but not
In southern Africa, solar panels usually perform best if they are tilted 20 to 30° towards anymore. Many new initiatives are springing
the north, meaning that they directly face the noon sun during the March and September up in practically all parts of the region. It is
equinoxes. Those angles also closely match the inclination angles of a typical domestic roof – a trend that is set to continue and get even
so solar panels lying flat on a north-facing roof are often already at their optimal tilt. stronger.

Atmosphere Acknowledgement
Unlike many of the world’s arid regions, like the Sahara and parts of central Asia, the southern This article was first published by The
African dry areas experience comparatively low levels of dust. One result is good long-range Conversation and is republished here under
visibility: light is able to move through the atmosphere freely. the Creative Commons licence.
Dust, smoke and haze in the atmosphere block part of the sunlight, like clouds do. While
some of these conditions do occur for limited periods, the atmosphere over southern Africa Send your comments to
generally has lower aerosol concentrations than in many other parts of the planet. rogerl@nowmedia.co.za

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