Grid-Tied | Hybrid | Off-Grid
Grid-Tied Solar PV System
A pure grid-tied system with no storage or load management for a user with fixed rate power charges is a viable option for South Africa.
The system however will need to be significantly under sized to minimise the wasted energy generation as typically no surplus power can be exported.
Essentially the PV system has to be sized to generate only sufficient power for the base load during the day, i.e. the fridge, freezer, pool pump and other permanently on devices.
The low investment cost of a small Grid Tied PV system with a high self-consumption rate make them quite attractive especially for households where the family is at home during the day.
A PV array produces DC (Direct Current) power when exposed to sunlight. Grid inverters convert this fluctuating DC power to 240 or 380 volt AC (Alternating Current) grid connected power.
Most household electrical appliances use AC power. These systems do not store power and provide no back-up in the event of grid failure.
Hybrid Solar PV System (Grid-Backup)
If frequent load shedding continues each winter then there will be continued demand for grid-backup systems that can operate with no grid for prolonged periods of time.
Adding a battery or a hybrid inverter along with a battery makes it possible to combine the energy from the PV system with that from the stored battery to power at least the essential loads in the property.
The size of the battery required depends on the rating of the essential loads to be driven from it at times of no solar power being available.
Load shedding typically occurs during the evening peak in winter from 17:00 – 10:00. Therefor there will be little or no solar power available to supplement the battery.
An alternative solution for new installations is to use a combined PV and battery inverter, commonly referred to as a hybrid inverter.
Off-Grid Solar PV System
Operating totally off the grid requires a large capacity battery backup capable of powering the property during periods of low irradiance in winter and an inverter capable of supplying the maximum load ever required at one time.
This requires a significant investment in PV modules, inverters and especially batteries which cannot normally be justified if there is a good quality grid connection available at the property.
An off-grid system is well suited to rural areas with little or no grid connection but is unlikely to be a viable solution in a well-connected urban area.
However, due to Eskom’s current state of affairs, looming tariff increases and possible loadshedding, disconnecting from the grid becomes a viable option for the future.