South Africa’s state-owned power utility, Eskom, has announced the initiation of one of the most unconventional energy ventures in recent years: the construction of an industrial gravity energy storage system in partnership with the American-Swiss firm Energy Vault. Electricity generated by solar farms will be utilized to elevate 30-tonne blocks, which will then be lowered to reintroduce power back into the grid.
The decision has been made to situate this facility at the site of the defunct Hendrina coal-fired power station in the Mpumalanga province. This undertaking is slated to become an integral component of the national grid modernization program, as the country grapples with persistent electricity supply disruptions and requires substantial storage capacity to effectively balance the growing share of solar and wind power in its energy mix.
The technical specifications for this inaugural unit are quite substantial: it will boast a power output capacity of 25 MW and an energy storage capacity of 100 MWh, capable of providing roughly four hours of autonomous power delivery at peak output. The system will be built upon the EVx 2.0 GESS (Gravity Energy Storage System) platform. Its fundamental principle involves converting electrical energy into potential energy: specialized lifting machinery hoists massive composite blocks to the apex of a tower structure, and when power is required, the blocks descend, spinning generators to feed electricity back into the network. Unlike pumped-storage hydroelectric facilities, this technology eliminates the need for large volumes of water and potentially utilizes industrial waste, including coal byproducts, for the manufacture of the gravity blocks.
Furthermore, the agreement includes a clause allowing for the deployment of up to 4 GWh of storage capacity across the Southern African Development Community (SADC) member states, encompassing 16 regional nations such as Zimbabwe, Mozambique, Angola, Botswana, Tanzania, and Zambia, among others. The engineering blueprint also incorporates plans for localizing a portion of the manufacturing, transferring relevant technology, providing training for Eskom personnel, and ensuring seamless integration with the existing transmission infrastructure.
For the Republic of South Africa, this project carries strategic significance. The nation remains heavily reliant on coal-based generation, and its power system frequently experiences capacity shortages. Gravity storage units offer the capability to bank surplus energy from solar and wind sources during periods of low demand and swiftly release it to the grid during peak consumption times. Should this pilot installation validate its projected performance metrics—such as high cycle life, minimal degradation, and effective long-duration storage—this technology could emerge as a crucial alternative to lithium-ion batteries for large-scale grid applications, thereby accelerating the region’s energy transition toward a more sustainable and low-carbon power supply model.
As of the present time, it appears that Energy Vault has fully commissioned only one comparable project globally, located in China. A gravitational accumulator similar in scale and capacity to the South African endeavor was connected to the Chinese grid in August 2024. Also during 2024, construction commenced on a gravity battery project in Texas, USA; however, this U.S. effort remains unfinished, and its current operational status is uncertain.
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