Transforming Old Mine Shafts

Transforming old mine shafts into future storage sites
February 12, 2018 by Nancy Owano, Tech Xplore

Just as there is an interest in sources of energy, there is also an urgent keen interest in storage. What is viable, as in what can work efficiently and make economic sense?

“Companies around the world are pouring time and money into projects to develop large-scale batteries to store energy and release it when there is greater demand on the grid,” said Greig Cameron, Scottish Business Editor, The Times.

That is one focal point, but an innovative company called Gravitricity, reported on this month by The Times and several other publications, thinks of another way to store energy.

Gravitricity Managing Director Charlie Blair: “So far there is a lot of focus on batteries, but our idea is quite different.”

Mining Technology quoted him: “It’s a simple case of ‘What goes up, must come down’.”

Its system can operate for decades without any reduction in performance. The company said the system had a 50-year design life with no cycle limit or degradation.

So what is their technology? They want to use old mine shafts for energy stores. These would be disused mine shafts transformed into energy facilities through a system that uses gravity and massive weights.

ESI Africa said that according to Blair, the company was “keen to speak with mine operators in South Africa” to understand how they might work together.

The technology operates in the 1MW to 20 MW power range. (Each unit can be configured to produce between 1 and 20MW peak power, with the output duration from 15 minutes to 8 hours.) The company said their technology has similar advantages to pumped storage for networks up to 33kV, but it does not need any nearby mountain with a lake or loch at the top.

“A cylindrical weight of up to 3000 tonnes is suspended in a deep shaft by a number of synthetic ropes each of which is engaged with a winch capable of lifting its share of the weight. Electrical power is then absorbed or generated by raising or lowering the weight. The weight is guided by a system of tensioned guide wires (patents applied for) to prevent it from swinging and damaging the shaft. The winch system can be accurately controlled through the electrical drives to keep the weight stable in the hole.” That is how the company explains what the system is about.

Time of response is impressive. The system should be able to respond to fluctuations in demand almost instantly. The company stated response time as “zero to full power in less than one second.”

The company was awarded a £650,000 grant by the British Government agency Innovate UK.

A deep hole in the ground can be a disused mineshaft brought back into use, or a purpose-sunk shaft, said the company. Shaft depths can be from 150m for new shafts down to 1500m for existing mines.

Costs for such a system? Blair said the biggest single cost was the hole, “and that is why the start-up is developing their technology using existing mine shafts,” said ESI-Africa.

The company said they will prove the technology using existing mine shafts. “As our technology costs decrease, the costs of drilling will reduce significantly, opening the opportunity for purpose-built shafts.”

What’s left in the wake of South Africa’s abandoned gold mines – Green Biz
Mark Olalde
Friday, January 15, 2016 – 12:45am
The name is derived from “happy prospect” in Afrikaans, and once upon a time, life and the gold haul were both good at the Blyvooruitzicht Gold Mine, 50 miles west of Johannesburg.

But two years after the mine’s owners abandoned it because it was unprofitable, sewage runs in the streets of the old mining village, tailings impoundments cover nearby towns in dust and illegal miners rule the abandoned shafts.

“I’m just going to take one or two potshots at them to keep them at a distance,” said Louis Nel, head of security at the now-abandoned Blyvooruitzicht.

He raises his shotgun and shatters the afternoon calm with several blasts. A few zama zamas — illegal miners whose title means “We try! We try!” in Zulu — run for cover.

Blyvooruitzicht is but one of thousands of abandoned mines scattered across South Africa, many from the gold industry. With recently shuttered mines adding to the massive impact of those left derelict years ago, the country faces a growing environmental, health and social crisis created by a withering gold industry and inadequate oversight.

South Africa’s Department of Mineral Resources, or DMR, holds a list of 6,000 “derelict and ownerless” mines, which became the government’s problem over the years when the former owners disappeared. While the DMR slowly rehabilitates those mines — at a rate of about 10 per year — companies continue to walk away from operations such as Blyvooruitzicht, and both mining companies and the government are slow to accept responsibility.

In the meantime, millions of South Africans live around waste facilities and many deal with respiratory, skin and other health effects that they blame on the mine waste piled in and around their communities.

In 2013, mining companies produced 562,000 times as much waste as gold, according to the South African Chamber of Mines. A decade before, that same ratio was less than half as large, at 212,000-to-1.

Mining operations are generating increased waste because South Africa’s gold is running out, and the remaining resource only can be found several miles below ground. This produces more waste and leads to higher production costs, more mining debris and increased acid mine drainage. South African companies dig up waste weighing more than 15 million pounds — heavier than 38 Boeing 747s — in order to process one standard gold bar’s worth of final product.

Around Johannesburg, some 270 tailings piles, most of them unlined, contain that waste, which weighs in at an estimated 6 billion metric tons. According to the Department of Agriculture and Rural Development in Gauteng, the province that includes Johannesburg and Pretoria, toxic and radioactive mine residue areas cover 124 square miles.

“You don’t want big sinkholes, you don’t want underground fires burning forever, you don’t want kids falling down shafts,” said Caroline Digby, director of the University of the Witwatersrand’s Center for Sustainability in Mining and Industry. “All these things happen all the time because sites are not properly closed.”

In the Johannesburg area, with 10 million residents, at least 15 percent of the population lives in informal settlements, with many placed by the former apartheid government near or even on top of these dumps. At Blyvooruitzicht, about 11,000 people live around the abandoned mine, many of them unemployed miners unable to afford housing elsewhere.

Throughout its lifetime, the mine generated about 2.5 million pounds of gold, silver, uranium and other minerals, but now it is a volatile wasteland. Just outside the main mining village, unremediated tailings piles stretch like monstrous sandy beaches. Children are known to swim in puddles of water on the dumps. Residents live in constant fear of electricity and water shutoffs, and illegal miners frequently engage mine security in gun battles.

Sikeme Lekhooana, chairman of the Blyvoor Community Committee, said his 5-year-old son knows the sound of gunfire all too well. “My little boy will tell you, ‘Papa, that is a gunshot outside,’” he said.

Blyvooruitzicht operated from 1937 until 2013, when a slumping market and labor disputes forced it into liquidation 14 years ahead of schedule. Two companies — DRDGOLD and Village Main Reef — worked the mine toward the end of its life. But each company has walked away, claiming the other is the owner and therefore responsible for the cleanup.

Lekhooana worked at the mine for 32 years before being laid off when the operation was liquidated. More than 1,000 employees from the mine face the same situation, unable to find work in a shrinking industry.

As of 2007, the owners of Blyvooruitzicht had set aside a fund of around $1,000 to clean up the large amounts of mine waste. That fund has since been increased to around $3 million, but DRDGOLD said the true cost to rehabilitate would be at least three times that.

Said Nikisi Lesufi, senior executive for health and environment for the Chamber of Mines, “There’s always a shortfall.”

Even when mines are operational, the DMR and other agencies do not properly address environmental consequences. Between November 2007 and February 2008, for example, thousands of metric tons of tailings pond material spilled from Blyvooruitzicht on four occasions, some of the waste washing into a nearby residential area.

These spills occurred with relative frequency, and while mine reports from the time noted crews being sent to clean roads and calls being made to the proper authorities, they do not mention any other measures taken to protect the community.

One major environmental and health concern is the vast production of acid mine drainage, especially around Johannesburg, which the water department estimates at up to 92 million gallons per day. Acid mine drainage mobilizes heavy metals in the environment, creates sinkholes and pollutes water supplies.

The Council for Scientific and Industrial Research estimated that as early as 2000, up to 20 percent of the stream flow (PDF) around Johannesburg came from groundwater that was polluted, in part, by mines. Yet as of last year, at least 39 mining companies were operating without a water license, the South African Human Rights Commission found.

And the air is no cleaner. The district just west of the city recorded 42.24 metric tons of tailings-piles dust (PDF) blowing into the air daily, some of it taken up by livestock and food crops.

Residents say that these piles cause health problems ranging from rashes to asthma to cancer. The list goes on, but a lack of local epidemiological studies has made it nearly impossible for communities near mine dumps to pursue litigation against mining companies.

Tudor Shaft is one such community, an informal settlement sitting atop a partially removed tailings facility just west of Johannesburg. An estimated 1,800 people live in shacks built on the radioactive and toxic soil. An orange hill of mine residue marks the center of the community, and sludge washes through the settlement when it rains.

Heavy metals and other pollutants in mine waste pose the most immediate threat to human health, but experts say consistent exposure to large amounts of low-level radiation might have long-term effects, too.

“When you’re already in a stress-burdened community that’s exposed to a variety of environmental pollutants, even low radiation levels that might not be toxic to very healthy individuals might have a significant impact on people,” said André Swart, executive dean of the University of Johannesburg’s Faculty of Health Sciences.

Some Tudor Shaft residents mix the soil with lotion and apply it to their faces as a skin cream. Some are baptized in polluted streams, and others — often pregnant women — follow a traditional practice in which they eat cakes made from the toxic dirt.

“You can either inhale [pollutants], ingest it, or absorb it through the skin, so they’re actually exposing themselves to all three of those root-ways of the pollution,” said Swart. “As this accumulates, the exposure level gets higher and higher and there can be real health issues.”

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