SA’s big rooftops could power 6 million homes

SOUTH AFRICA has many factories, warehouses, schools and hospitals—big buildings with large rooftop spaces.

- MAMAHLOKO SENATLA JAANE

In such a sunny country, these flat surfaces would be perfect for large photovoltaic solar systems that could generate enough renewable energy to supply themselves, and feed into the national grid. This would reduce the amount of coal that South Africa’s national electricity provider would need to burn.

The author, a renewable energy engineer, was part of a team who researched how commercial buildings could be set up to serve as strategic assets for decarbonisation and increase the security of South Africa’s power supply.

How much space is available, and how suitable is it?

We calculated that 111 million square metres (m²) of rooftop space is available on the roofs of universities, schools, hospitals, and commercial buildings such as shops, warehouses, office blocks, and factories.

Our research also found that 80% of these roofs were highly suitable for solar panels. The amount of electricity that commercial building rooftops could hold is 12 gigawatts, or roughly enough to power about six million homes of six people each per year.

There is currently no public record of the number of commercial buildings and individual size (square metres) of their roofs, so we used publicly-available statistics about floor space to calculate the roof space using a floor-space to roof-space conversion factor.

A square metre built does not translate to a square metre of roof availability. We calculated that for warehouses and shopping centres that are not high-rise buildings, the ratio of floor space to roof space area is roughly the same. For high rise shopping malls, the roof space is about one third of the floor space.