SWER stands for Single Wire Earth Return. There are many remote Eskom customers using this type of overhead power transmission line, where there is only one conductor on the poles. The return current passes through the ground to the main substation, which is quite interesting! This design reduced the cost of connecting rural or remote users.
Here is a schematic of how it works:
The user has two phases of Line to Neutral of 240V each. This means it is not possible to use a three-phase inverter. Johan du Preez from ARW Solutions came up with a great solution in collaboration with Freedom Won. He uses single phase hybrid inverters connected to each of the two phases that are all connected to the same battery bank. This means he can maximise the use of both phases from Eskom at any time while feeding separate single-phase power to distinct parts of the property. The hybrid inverters supply power to the loads they are connected to, and/or to the common battery bank. The Freedom Won batteries are able to communicate with all the master inverters in the system.
Some of Johan’s sites with this system installed include:
- Nkoro bush lodge with 96 kW total inverter power with 117kWp solar panel power and one Freedom Won LiTE Commercial 200/160 52V battery.
- Chitwa Chitwa game lodge with 160kW inverter power and 196kW solar panels and two Freedom Won LiTE Commercial 200/160 52V batteries (see photos).
Eskom customers on SWER lines should explore options for connecting their properties to solar and battery storage while maintaining access to SWER line support.
Advantages include:
- Battery backup with solar can support loads when the SWER line is off – this can be very common on these lines,
- The inverters can limit the draw from the SWER line to the design limit or a lower value while still supplying higher power levels to the loads by using solar and battery for support,
- The overall cost of energy will be greatly reduced,
- Both SWER phases can be used optimally by feeding into one battery bank.
