There is a need to start planning another pumped-storage scheme in South Africa. Much work has already been done at a site in Limpopo province and the project was very close to being put out to tender at one stage. In 2008/9, the National Energy Regulator of South Africa and Eskom announced the Tubatse pumped-storage scheme had been put on hold. Tubatse would be an essential part in providing more peak power and because of reasons set out below, it should be an independent power producer (IPP).

A pumped-storage scheme at present is the only practicable and economically viable way to store electrical energy in large quantities. Eskom carried out prefeasibility studies on seven sites in South Africa for pumped-storage schemes between 1987 and 1995. This was followed by a comparative study and ranking process. This resulted in the selection of three top schemes, namely Braamhoek, which became Ingula, Mutale and Lima.

Project Lima, which was renamed Tubatse, was revised and generation capacity increased by 50% in October 2007 after the Department of Water Affairs had decided to commence construction of the De Hoop dam, which is about 20 km from the proposed site of Tubatse. The De Hoop dam is now complete.

A pumped-storage scheme has other benefits apart from providing peak power. The first is a requirement for a backup solution that can respond quickly to sudden surges in demand or to the failure of a large baseload plant. Another benefit is that it can operate in synchronous condenser operation (SCO), when it is not used for pumping or generation.

During SCO in the generation direction, the units are available as spinning reserve, “spinning in air”, meaning they are able to very quickly respond to a change in the grid generation requirements. An example of the capability of SCO, which could be incorporated in the final design for Tubatse, is Britain’s Dinorwig power station, which has probably the fastest response time of any power system in the world, as it can provide 1 728 MW in just 90 seconds.

The Tubatse pumped-storage scheme has a rated head of 636 m and has a capacity of 1 500 MW. The underground powerhouse complex houses four pump turbines, each with a generating capacity of 375 MW. The principal other features of the scheme are the upper and lower dams.

There would be two large caverns, as opposed to three at Drakensberg, and there are no surge shafts, the four tailrace tunnels and the main access tunnel are shorter than those at Drakensberg or Ingula. It is possible that Tubatse could be completed in 60 months, compared with the 84-month programme for Ingula. During the final feasibility stage, the project was independently reviewed by the HSBC and Fichtner Consulting & IT consortium and found to be sound.

The need to proceed with construction is now very urgent. Since the electrification of 200 000 existing houses and the simultaneous plan to construct 200 000 new houses each year since 1994, the electrical peak power demand has grown from about 2 000 MW to 4 000 MW.

The experience in other countries regarding the introduction of renewable energy has shown a greater need than before for the storage of peak power. The UK publication the Engineer states: “The electricity sector is currently undergoing its biggest transformation for over a century. Energy storage is vital in the coming decades needing a large grid-connected electricity storage capacity.”

South Africa has had many conferences, studies and reports, but so far there are no signs of concrete action. The load-shedding in April may have been due to a number of reasons, but this underlines the need for the immediate commencement of the design and construction of Tubatse. There are very few financial options available to State-owned company Eskom or the National Treasury. The rates for borrowing for investment are not going to get any easier for many years ahead.

However, the Renewable Energy Independent Power Producer Procurement Programme (REIPPPP) has proved successful in bringing in the finance to construct and commission 64 power plants. More than R100-billion has been raised internationally to bring about an extra electrical capacity of about 3 600 MW, without the use of National Treasury funds.

Tubatse should be declared a potential IPP, which would be able to develop the scheme at a lower cost than Eskom. Most of the expertise required to construct the caverns and tunnels at Tubatse is available within South Africa’s tunnelling and construction industry. The experiences gained at Ingula can be fully exploited. With a two-year lead-in time for concluding agreements, and a six-year completion period for commissioning all the four pump turbines, in 2022, there would be 1 500 MW of additional peaking power capacity.

Tubatse should be ringfenced, so that the State only has to finance the building of roads and some other minor infrastructure. Eskom’s transmission division would construct the switchyard and transmission lines linking the grid to Tubatse.

Some of the considerable number of actions that have to be taken start with the process to invite competitive bids, as was done for the renewable energy projects, the REIPPPP method. The 64 solar and wind projects under construction at present have given the whole South African engineering, banking and legal professions a huge exposure to new forms of getting difficult power generation projects successfully negotiated and completed. The way forward is to complete the Tubatse pumped- storage scheme as an IPP.