Rooftop photovoltaic (PV) systems are extremely exposed and therefore especially vulnerable to damage caused by the direct and indirect results of lightning strikes. Since the PV system is directly connected to the electrical installation of the building, lightning strikes can have severe consequences for people inside the building, as well as the structure itself and the electrical devices contained inside it.

It is crucially important to protect rooftop PV systems from lightning and surges, especially as rooftop PV installations in South Africa grow in popularity and their installations across the country continue to increase.

Multinational company DEHN Africa renewables business development manager William van Wyk says DEHN Africa has been involved in a number of commercial rooftop PV projects over the past few years and it can see that this industry is rapidly expanding. The owners and managers of commercial entities like shopping malls and office parks are becoming increasingly aware that it makes sense, over time, to supplement their electricity requirements through the self-generation possibilities offered by rooftop PV installations.

“However, lightning strikes can cause considerable damage to PV systems, both directly from a strike itself, as well as indirectly as a result of related electrical surges. The resulting repair and replacement costs are high, and this consequently delays the return on investment of the PV installation, and postpones the break-even-point of the investment. A lightning and surge protection concept to protect your PV system is therefore crucial.”

The Green Cape ‘Energy Services Market Intelligence Report 2019’ reports that the national embedded generation market for installations, operation and maintenance of rooftop solar PV has grown locally in the last two years. GreenCape is a non-profit organisation dedicated to driving the adoption of economically viable ecofriendly solutions from the Western Cape.

The 2019 report notes that: “The total annual available market could grow to a saturation point of 500 MWp installed a year on an ongoing basis. This market could reach a total of 7.5 GW of installed capacity by 2035. At a cost of R10/Wp this installed capacity growth represents a total available market of R5-billion a year and a total available market of R75-billion by 2035.”

The organisation also clarifies that the market in installation, operation and maintenance of rooftop PV systems was estimated at R2-billion over the period 2016 to 2019, with more than 94 MW of installed rooftop PV capacity currently in South Africa.

“With the local rooftop PV industry expanding rapidly, and with all the benefits this can bring – including the potential for reduced electricity bills for the organisation or business over time, lower maintenance costs and of course job creation – it is imperative that PV installations are properly protected from the direct and indirect consequences of lightning strikes,” notes Van Wyk.

He explains that a professional lightning protection system consists of external lightning protection with air-termination systems, down conductors and an earthing system. It also consists of internal lightning protection for lightning equipotential bonding and surge protection. Lightning equipotential bonding reduces the potential differences caused by lightning currents and is achieved by interconnecting all isolated conducting parts of the installation by means of conductors or surge protective devices.

“When we look at the different applications for PV installations on buildings, we find three different potential scenarios, namely: buildings with PV systems installed but without external lightning protection; buildings with PV systems installed, with external lightning protection and sufficient separation distance; and buildings with PV systems installed, with external lightning protection, but without sufficient separation distance," he explains.

Further, Van Wyk points out that DEHN Africa works with all three scenarios in order to make sure that a client's PV investment is completely safeguarded, as well as the building to which it is connected, the electrical components inside the building, and of course the safety of the people working inside the premises.