According to the Department of Energy, the annual 24-hour global solar radiation average is about 220 W/m2 for South Africa, compared with about 150 W/m2 for parts of the USA, and about 100 W/m2 for Europe and the United Kingdom, making South Africa’s solar resource one of the highest in the world.
Most areas in South Africa average more than 2500 hours of sunshine per year, and average solar-radiation levels range between 4,5 and 6,5 kWh/m2 in one day. These statistics cause many to support the development of a local solar industry, we must also remember that across wide stretches of our country, we have one of the highest lightning ground flash densities in the world. This therefore makes lighting protection of solar systems an imperative.
Photovoltaic (PV) systems have become a significant sector within the energy market in recent years and it is therefore important that the development of affordable, inexhaustible and clean solar energy technologies will, among other benefits, allow a country to increase its energy security, reduce pollution which is expected to play an important role in controlling climate change. However, because PV plants are subject to weather, it’s essential to protect sensitive electronic system components from failure due to lightning flashes and surges.
Lightning surges in a PV system can damage PV modules and inverters. In the event of a system failure, this can lead to profit losses in addition to the costs of repair or replacement. Therefore, one should aim to protect the solar plant from damage by fire, such as may be caused by a direct lightning strike, as well as protecting the electrical and electronic systems against the effects of lightning electromagnetic impulses (LEMP).
Steps which can be taken to protect the air-termination system and down conductor system, the earth termination system, the lightning equipotential bonding, the surge protection measures in the PV array and the surge protection measures for IT systems.
Air-termination system and down conductor system
For the protection of the PV array against direct lightning strikes, it is necessary to arrange the solar modules in the protection zone of an isolated air-termination system.
Earth-termination system
The earth-termination system of the PV system is designed as a ring earth electrode (surface earth electrode), while the earth-termination system of the operation building should be designed as a foundation earth electrode.
Lightning equipotential bonding
All conductive systems entering the operation building from outside must be generally included into the lightning equipotential bonding.
Surge protection measures in the PV array
To reduce the load on the isolation inside the solar modules at a lightning strike into the isolated air-termination system, thermally monitored surge protective devices are installed in a generator junction box as loosely as possible to the PV generator.
Surge protection measures for IT systems
The operation building provides a remote diagnostics system, which is used for the quick and easy function check of the PV systems, permitting the operator to recognise and remedy any malfunctions at an early stage.
Contact Hannes Ackermann, Dehn Africa, Tel 011 704-1487, hannes.ackermann@dehn-africa.com