Nestled under a mountain range in South Africa lies a giant that is ready to come to life. It is a massive power house buried deep underground whose turbines will start generating electricity in a matter of months to help the country’s biggest utility meet the growing demand for power.
The utility, Eskom, has struggled to keep up with the demand. Although it has made great strides in reducing their frequency in recent years, blackouts still occur. So it is carrying out a plan to strengthen its network by increasing its production capacity by 10,932 megawatts (MW). The power house, located below the Little Drakensberg mountain range along the border of the KwaZulu-Natal and Free State provinces, is part of that plan. It and two other new plants are to add a combined 10,932 MW within 2022, expanding installed capacity by 23%.
Known as the Ingula Pumped Storage Scheme (IPSS), it will have a production capacity of up to 1,332 MW when it goes into operation in the second half of the year. «Ingula is a significant part of our massive infrastructure development programme», South African President Jacob Zuma once said.
Built by the CMI Joint-Venture with Italy’s Salini Impregilo as one of its partners, the IPSS comprises a power plant and a pumping station with a dam and accompanying reservoir on either side of it - one above an escarpment and another below it. Kilometres of tunnels, galleries and shafts make up the rest of the massive complex. Named after the area of the same name, Ingula, it is a virtual green giant. Its design and construction follows the principles of sustainability and are especially attentive to the surrounding environment. And when it eventually comes to life, it will be a virtuous producer of renewable energy by recycling the water that it uses.
«We are on the last stretch», says Avin Maharaj, senior project manager of the project. «Yet we are prioritizing safety and zero harm and quality standards… while sustaining mutually beneficial stakeholder relations.»
Although the IPSS, which uses a system known as Pumped Hydroelectric Storage (PHS), works much like a hydroelectric plant, it only produces electricity when the need arises. In the case of South Africa, that would be at peak hours of the day.
With hydroelectric energy stored in the form of water behind the upper dam’s reservoir, it can be put into action in less than three minutes. The reservoir’s storage capacity will be 21,000 MW hours once it is filled with water.
This ability to produce electricity at a moment’s notice contrasts with that of a thermal power station, which is not as nimble in starting and stopping its turbines. This makes the PHS system ideally suited to help Eskom handle the volatility that it experiences on its grid amid frequent changes between surpluses and shortages of electricity.
Another distinguishing feature of the PHS is its ability to recycle up to 80% of the water it uses, making it the most cost-effective way to store large amounts of hydroelectric energy.
It is the fourth of its kind to be built in South Africa, but it is the biggest in terms of generating capacity at 1,332 MW.
During peak hours when demand for power is strongest, the IPSS will draw water from the dam’s reservoir at the top of the escarpment and have it surge down two headrace tunnels to churn four 333 MW Francis turbines. The rated generating head – also known as hydraulic head or water drop - from the reservoir to the turbines is about 434 metres. After the water passes through the turbines and empties into the second dam’s reservoir below the escarpment, the IPSS can use the same turbines to pump it back up to the top during off-peak hours when demand is low and its services less needed.
Since it is 116 storeys underground, the IPSS will leave virtually undisturbed the surrounding area where more than 300 species of birds including the endangered Southern Bald Ibis and White-winged Flufftail come to nest. The only significant
sections that will remain visible will be the dams and their respective reservoirs, the capping structures of the surge shafts and the inlet and outlet structures.
With the help of conservationists, Eskom and the joint venture have taken great lengths to preserve the area as much as possible. The lower wetland and grassland at the top of the escarpment, for instance, are recognized by experts as two of the most fragile habitats in the world.
When the construction of the upper dam and reservoir deprived some birds of their nesting ledges, an artificial one was built to compensate for it. This and other efforts to protect the environment led the joint-venture to be named the Best Principal Contractor, Environmental Management by Eskom in 2013.
It was also the first Eskom construction site to receive ISO14001 certification in March 2011.
INGULA IS PART OF ESKOM’S PLAN TO INCREASE PRODUCTION CAPACITY TO MEET SOUTH AFRICA’S GROWING DEMAND FOR ELECTRICITY
IN 2013, THE CONSORTIUM THAT BUILT THE PLANT WAS RECOGNIZED BY ESKOM AS “BEST PRINCIPAL CONTRACTOR” FOR ITS ATTENTION TO THE ENVIRONMENT
ENVIRONMENTAL SUSTAINABILITY IS ONE OF THE PROJECT’S GUIDING PRINCIPLES
INGULA IS ONE OF THE FEW HYDROELECTRIC PLANTS THAT RECYCLES THE WATER IT USES
MOST OF THE INGULA PROJECT IS UNDERGROUND, LEAVING A GOOD PART OF THE SURROUNDING AREA UNDISTURBED
GREAT LENGTHS HAVE BEEN TAKEN TO PRESERVE THE ENVIRONMENT, ESPECIALLY THE NESTING GROUNDS OF HUNDREDS OF BIRDS
At the top is the Bedford Dam, whose reservoir is filled by a tributary of the Wilge River. It is a rock-filled, concrete-faced dam some 51 metres high and 810 metres long. Some 470 metres below and six kilometres away is the Bramhoek Dam. At the headwaters of a tributary of the Tugela River, it is made of roller-compacted concrete and has a height of 38 metres and length of 310 metres.
The reservoirs of the two dams can hold 22.4 million and 26.7 million cubic metres of water, respectively.
The excavation of the two inclined headrace tunnels one kilometre long was one of the joint-venture’s biggest challenges because it involved drilling and blasting on a 24-degree gradient to follow the slope of the escarpment.
Another feat was the machine hall, which was carved out of unstable soft rock. It has a vaulted ceiling spanning 24.5 metres with a length of 184 metres and a depth of up to 45 metres.
The joint-venture deployed an innovative way to erect a concrete frame in the machine hall to support a 400-ton gantry crane. Given the limited size of the tunnel and the cramped space inside the hall, it made 552 precast, hollow concrete pieces in the shape of columns, beams and corbels that were then assembled to make the frame inside the hall with second stage backfill concrete.
South African is ready to invest more than $50 billion during the next three years to develop the country’s public infrastructure. The announcement was made by Finance Minister Pravin Gordhan in his 2016 budget speech before parliament. For transport and logistics infrastructure, for example, the government is to invest nearly $17 billion. But Gordhan also spoke of the potential for private-sector participation. “In energy, transport, telecommunication and urban development, there are many opportunities for joint public and private investment and facilities management,” he said.