Renewable energy developer Seriti Green on November 26 officially handed over the Vunumoya Main Transmission Station (MTS) to State-owned power utility Eskom.

The infrastructure will now become an asset of Eskom subsidiary the National Transmission Company South Africa (NTCSA).

The Vunumoya MTS is a 400/132 kV 500 MVA substation, connecting the Ummbila Emoyeni wind farm to Eskom’s 400 kV transmission network.

It also has additional capacity for future feeders and transformers, with the potential to expand the station from 1 GW to 3 GW, Seriti Green CEO Peter Venn told Engineering News. “It’s our gateway to export our 900 MW of renewables into the South African electricity grid.” 

The Vunumoya MTS is a key part of Seriti Green’s Ummbila Emoyeni One Wind Energy Facility, which the company is developing in Mpumalanga.

The MTS provides the critical infrastructure needed to feed renewable energy into the national transmission network. The handover allows Seriti Green to start commissioning and exporting energy onto the grid, Venn explained to the publication.

“Within the next four to six weeks, the turbines will start turning and hot commissioning will start . . .”

The handover enables the first 155 MW of wind energy from Seriti Green’s Ummbila Emoyeni project to be fed into the system ahead of schedule, the start of a 900 MW programme that will progressively add further renewable capacity.

Originally scheduled for commissioning in March 2026, the project’s first phase has been accelerated and will now deliver energy into the grid from November 28.

The power produced in this first phase will be wheeled to coal miner Seriti Resources as part of the mining group’s commitment to decarbonising its operations. Seriti Green is subsidiary of Seriti Resources. 

NTCSA CEO Monde Bala explained to Engineering News that the MTS is a customer self-build project. It was a collaboration between Seriti Green and its contractors, with the NTCSA team providing technical assistance to ensure compliance in terms of quality and safety, he added.

He outlined that, as the substation is now an NTCSA asset, it would run and operate the infrastructure.

“Essentially, it is us integrating this wind energy into the rest of the grid. . . Energy from here would be transported through the grid, to other parts of the country. . .”

Venn acclaimed that the over R1-billion project was delivered in 17 months, on time and on budget.

Eskom Group CE Dan Marokane welcomed the on-time completion, noting that it allows Eskom to focus on other work, while renewable energy companies “put electrons into the grid”.

He told Engineering News that the handover of the MTS affirms the country’s recently launched Integrated Resource Plan (IRP) 2025, showcasing that the model of crowding in private sector resources and skills to assist on this national programme works.

Overall, the IRP 2025 envisages the introduction of 105 000 MW of new generation capacity by 2039, including 34 000 MW of onshore wind and 25 000 MW of utility-scale solar PV.

Marokane said Eskom would pursue a similar collaborative approach in other areas, while simultaneously focusing on the traditional model of building its own substations.

“We need all hands on to deliver on the about 14 500 km of transmission lines, and the associated substation capacity that goes with it, and you will see a blend of execution methods,” he averred.

“The Vunumoya project forms part of the commitment to enabling the efficient integration of renewable energy projects into the grid, strengthening grid reliability and supporting South Africa’s transition to a diversified, low-carbon energy mix,” Bala mentioned.

He pointed out this handover is one of the first steps in the NTCSA’s Transmission Development Plan, which projects that 56 GW of new generation capacity will be integrated between this year and 2035, which will require 14 500 km of new transmission lines, along with 210 transformers providing 113 000 MVA of capacity.

Bala said the NTCSA would continue to work with Seriti Green on the next phases of Ummbila Emoyeni.

Ummbila Emoyeni is a seven-stage, 900 MW hybrid energy facility in the Highveld area of Mpumalanga. The development would ultimately consist of 750 MW wind energy, 150 MW solar PV and 800 MWh of battery storage.

Venn told the publication that the broader project is progressing well and within budget.

Seriti Group CEO Mike Teke indicated that 15 wind turbines had already been constructed.

The benefits of the MTS and wind farm project to the surrounding community were also underscored.

Venn said the over 130 000 people living in close proximity to the project are the “most important stakeholders”, and emphasised the importance of bringing in meaningful jobs.

The project peaked at 1 000 jobs, he informed.

“This gateway of this MTS opens up the channel for all 900 MW of this project. During construction, I’m very comfortable to say we will continue to employ 1 500 people across the substation, and the wind farm,” Venn outlined, adding that there is a target of engendering 600 permanent jobs.

Electrical construction company Tractionel Enterprise CEO Neresh Pather pointed out that over R165-million of the MTS project spend was on local contractors, with about 53% of the workforce on site constituting people from the surrounding areas.

This was owing to skills development and localisation being prioritised from the onset of the MTS project. Tractionel oversaw the construction of the MTS project.

Pather highlighted localisation and skills development as key requirements to deliver on the country’s IRP.

Venn echoed this sentiment, noting that, of the 70-person Seriti Green team on site, only seven originally hailed from the renewable energy sector – showcasing that the skills needed to grow the green sector can be developed and brought in.