Kopano Energy Holdings arrived with three adjacent farms outside Ventersburg, one grid allocation and a problem of arithmetic. The budget quote capped export at 45 MW at the 132 kV substation, while the offtake — a wheeling agreement with four industrial buyers on the Reef — needed closer to 128 GWh a year to stay ahead of its escalation clause. The land supported far more generation than the wire would ever carry. Two earlier developers had handed the allocation back rather than build against it, and the connection was six months from lapsing by the time the EPC contract was signed.
The Free State network is energy-constrained rather than capacity-constrained, so the connection carried a curtailment obligation rather than a firm cap: the system operator can instruct any setpoint at fifteen-minute resolution, with a five-minute response window, and the first eight per cent of annual curtailed energy is uncompensated. Construction then ran through the worst of the load-shedding schedule. Stage 4 and above pulled grid power off the local feeder for six to eight hours a day, in blocks that moved weekly — awkward when the batching plant, the pile driver and every commissioning test on the MV switchgear all want the same supply.
The solution
110,400 bifacial modules at 580 W on horizontal single-axis trackers, split across three sites of 52, 41 and 29 hectares and rated 64 MWp DC against 51 MW AC — a deliberate 1.25 ratio, sized for the curtailment profile rather than for peak yield. Each site runs its own 33 kV collector ring into a shared 132/33 kV substation carrying two 40 MVA transformers and a single revenue metering point. A 30 MW / 60 MWh containerised battery sits on the AC bus behind the same breaker, so it charges from clipped and curtailed energy and never draws from the network to do it.
A plant controller reads the dispatch setpoint and shares it across 148 string inverters in 200 kW steps, settling the point of connection inside its limit in under forty seconds. Surplus charges the battery until it is full; after that the inverters walk off the maximum power point and the rest is spilled as unharvested DC rather than dissipated as heat. Over the first twelve months the plant kept 96.4 per cent of theoretical generation through 340 hours of curtailment instruction. The build used the same asset early — block A was energised eleven weeks ahead of the others, and its first battery container carried the compound and the batching plant through every shedding block after March.
Annual yield
Metered at the 132 kV point of connection.
Curtailment capture
Generation retained under dispatch limits.
Storage buffer
Absorbs clipped output for the evening peak.
Build programme
Three sites energised through the shedding.
The first curtailment instruction came through on day nine of commercial operation and we lost 4 MW for two hours — I expected to be angry about it, but the plant had already moved most of it into the battery before anyone phoned me.
