Renewables: Africa’s bold gambit

Solar thermal
There is currently very little concentrated solar power (CSP) generating capacity around the world but as with PV, plants are now under construction in both North and South Africa, and should become an increasingly popular option elsewhere on the continent, as construction and production costs fall.

CSP converts the sun’s heat rather than light into electricity via hundreds of mirrors deployed in a dish, trough or central receiver system. These mirrors concentrate sunlight to heat water or another liquid, to produce steam which is then used to drive a turbine, as in geothermal or traditional thermal power plants.

Such plants could be developed on the same scale as thermal projects and so would offer the same advantages and drawbacks of all centralised, large-scale generating capacity. Such centralised power generation is favoured by most power utilities, partly because it is easier for them to control.

Many analysts had expected that technological advances would eventually make CSP a more economically attractive option. However, PV costs have fallen rapidly in recent years and so the more established technology remains more popular.

Developers argue that CSP technology is superior because it does not rely on high-cost silicon but CSP projects do require aluminium, copper and steel, all of which fluctuate widely in terms of price.

Given the relative scarcity of operational CSP plants and the fact that economies of scale should reduce both construction and operating costs over time, it is difficult to compare the cost of producing electricity by the two technologies.

In addition, CSP has one advantage over PV in that heat stored in the liquid can be stored for some time after the sun’s rays stop heating the water. Heat storage of about three hours is now available and this period is increasing through new innovations.

In addition, solar thermal technology has long been used on a commercial basis with no state support in North Africa as a means of heating water. The sun’s heat is used to directly heat water for household use. Although no electricity is actually produced, this practices avoids having to produce the electricity required to heat water in the first place and as such can be seen as a form of energy efficiency.