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As Gold Fields' landmark solar project at South Deep begins feeding power to the operations, the gold miner has offered to supply Eskom with surplus energy from the project.
As Eskom works to procure megawatts from independent producers to ease the national power crisis – subject to approvals from Nersa – South Deep has approached the utility about its surplus energy from its plant.
"We've written them a letter saying that we've got a bit of surplus right now. We've had a response, and they want to evaluate ... so hopefully we'll hear back from them," said Martin Preece, Gold Fields' executive vice-president for South Africa, adding that Eskom had been fairly responsive throughout the solar plant's development.
The landmark solar project 50km south-west of Johannesburg, known as the Khanyisa solar plant, was the first private self-generation project over 10MW to obtain a licence from the National Energy Regulator of South Africa (Nersa).
Roughly the size of 200 football fields, the "black sea" comprises 101 000 solar panels positioned facing 25 degrees north and expected to cater for at least 24% of South Deep's annual energy requirements – 103 gigawatt-hours (GWh) of South Deep's 430 GWh annual energy consumption.
The plant began generating green power in August this year, and by Tuesday this was feeding as much as 38MW to South Deep, and it's anticipated to reach 50MW (and possibly even more) in coming weeks as distribution improves.
"We are balancing demand," said Preece. "We are changing how we distribute power, so it's about putting it into the right places."
With a price tag of over R700 million, but estimated annual savings of R130 million, Preece said the solar plant was the easiest project he's ever had to motivate to the Gold Fields board for approval.
Despite the teething problems in relation to load curtailment, South Deep remains confident in the systemic benefits of the project, and others like it.
"From a national perspective, we are taking load off the grid, and the more of us doing that, the less probability of load curtailment," said Preece.
Battery storage for the solar power has so far proved uneconomical.
"We've done the numbers, we've looked at lithium-ion batteries, we've looked at vanadium flow batteries … we can't make the economics work," said Preece. "I think batteries are at the back end of our solution, as the technology improves and the cost of manufacturing comes down."
Preece is hopeful that President Cyril Ramaphosa's energy action plan to feed surplus energy into the grid will become a reality. "Hopefully, we can get some traction on that; that will be in my view a far cheaper and beneficial solution than trying to build your own storage," he said.
Interestingly, the addition of solar is having the unintended consequence of deeper than anticipated load curtailments for the gold mine, which in some instances has forced South Deep to start up diesel generators to power essential equipment.
While non-industrial users are faced with load shedding, industrial users are subject to load curtailment, which, in terms of Stage 1 and Stage 2 require industrial users to curtail their power use by 10% while Stage 3 and Stage 4 require they curtail use by 15% and 20%, respectively. Beyond Stage 4 industrial users must demand down to essential load, where in operations are essentially shut down.
Unlike the rotational nature of load shedding, load curtailment requires industrial users to curb their demand consistently and in line with the varying stages announced.
"If in the past two weeks we've been using 50MW and Eskom apply load curtailment of 10%. Then I've got to take 5MW out and use 45MW. So now I've got solar, so I'm not using 50MW, I'm using, say, 35MW. So now I take 3.5MW off that, and I get closer to 30MW, not 45MW [as would have been the case before the solar installation]," said Preece. "The problem that we have on that is when you cut 10% off that lower base, we go underneath what we need as a minimum to keep the mine running - the pumps, the fans, the fridges. So that's why we had to start the diesel gensets when the country hit Stage 6 load shedding a few weeks ago. Even though we had the solar running, we had to start the diesel just to top it up."
Preece said South Deep is engaging Eskom to resolve the matter. The mine is meanwhile also exploring wind power options, with a wind mapping effort currently under way on site.
