South African independent power producer Mulilo, which announced at the recent South Africa Investment Conference that it would be investing R15-billion in new renewables and storage projects, has achieved financial close on the 76 MW/304 MWh Mercury Battery Energy Storage System (BESS) project.

Located near Viljoenskroon in the Free State, the Mercury BESS project was selected in December 2024 as one of eight preferred bidders under the second bid window of South Africa’s Battery Energy Storage Independent Power Producer Procurement Programme.

The preferred bidders selected during the round are expected to collectively build 615 MW/ 2 460 MWh of battery storage at a total investment value of R12.8-billion.

The Mercury BESS facility, which is one of five Mulilo projects selected during the bid window, is being developed under a 15-year power purchase agreement with the National Transmission Company South Africa (NTCSA).

Once operational, the BESS plant will connect to the Mercury Main Transmission Substation, which is one of eight transmission substations sites pre-selected by the NTCSA for the bid window.

Besides Mulilo, which has Copenhagen Infrastructure Partners and Norfund as shareholders, the other participants in the project consortium are black-economic empowerment group Reatile and a local community trust.

The project’s funding, legal and technical advisers include Standard Bank, Absa, Nedbank, Bowmans, ENS, Fasken, ARUP and Pepper Tree Capital.

Mulilo CEO Jan Fourie said that as battery storage became an increasingly important part of South Africa’s energy mix, projects such as Mercury would play a key role in strengthening grid stability and supporting continued renewables growth.

It also represented an important milestone in Mulilo’s own expanding BESS portfolio, which now comprises 3 508 MWh across nine awarded projects from the second and third public procurement bid windows.

Mulilo is also partnering with EDF on the three Oasis BESS projects in the Northern Cape, with a capacity of 257 MW/ 1 028 MWh, which are already under construction.