Many abandoned mines are being considered for pumped hydro to support renewable energy production. These are just a few examples
German Coal Mine
A coal mine that powered German industry for almost half a century will get a new lease on life when it’s turned into a giant battery that stores excess solar and wind energy. In the German state of North Rhine-Westphalia, a coal mine will close in 2018. Aging coal infrastructure, low wholesale power prices, and a move away from the highly polluting power source all make renewable energy an attractive alternative. However energy storage is an issue to help balance the grid during times of fluctuating power production that is associated with solar and wind.
The state is set to turn its Prosper-Haniel hard coal mine into a 200-megawatt pumped-storage hydroelectric reservoir, which acts like a battery and will have enough capacity to power more than 400,000 homes, said state governor Hannelore Kraft. The town of Bottrop, where people worked the 600-meter-deep mine (1,969 feet deep) since 1974, will keep playing a role in providing uninterrupted power for the country, she said.
Traditionally, pumped storage has required fairly specific terrain. But a used coal mine can offer the right environment for pumped storage without natural elevation differences and reservoir capabilities, although mines do require extensive analysis to make sure they’re geologically fit for pumped storage. The University of Duisburg-Essen (UDE) is working with mine owner RAG AG to complete the project, and, in a press release from August 2016, UDE professor André Niemann said the mine site is “suitable for the infrastructure to implement an underground pumped-storage power station as a closed system.”
“We assume a storage volume of 600,000 cubic meters,” Niemann added at the time. “This means that at full charge you would have an output of about 200 megawatts for four hours.” The mine itself is 600m (nearly 2,000 ft) deep and has been in operation since 1974. Initial development of the pumped-storage project is being supported by funding from the North Rhine-Westphalia government as well as the EU.
According to Bloomberg, North Rhine-Westphalia is the source of more than a third of Germany’s power generation, including many coal plants. But the state plans to make 30 percent of its power mix renewably sourced by 2025, so officials are seeking energy storage solutions.
Old Gold Mine Australia
Genex Power has been buoyed by a feasibility study which found its plans to convert a disused underground gold mine west of Townsville into a hydro storage plant or a “giant battery” was commercially viable, with plans to open the project in 2018.
The study lodged with the Australian Stock Exchange showed a $300 million 250 megawatt hyrdro plant with 1500 megawatt hours storage capacity could work on the site, with the company saying there had been strong interest from investors in what would become the third largest hydro-electric storage project in Australia.
The Australian Renewable Energy Agency – which has allocated $4 million to the Kidston pumped storage project, 400 kilometres west of Townsville – is hoping it will pave the way for a string of former underground mines being used to help bring more renewable energy on-line in northern Australia.
This includes a 50 megawatt solar farm being developed by Genex at the Kidston site with potential to use solar to power the storage plant’s water pumps,” he said.
“If everything goes to plan, Genex should reach financial close and start construction in 2017, an achievement that would pave the way for more large pumped hydro storage projects at disused mines to support our energy grid.”
The feasibility study by specialist power and water consulting firm Entura and their project partner HydroChina found the Kidston pumped storage project at the abandoned gold mine could provide six hours of continuous generation using two 125 megawatt fixed-speed turbines. The turbines would pump water into an upper-storage reservoir during the day or overnight when prices are low and then release it into a lower reservoir to generate power during periods of high demand or need.
Projects in the USA
The Elmhurst Quarry Pumped Storage Project (EQPS)
This is a conceptual underground pumped storage project that would utilize an abandoned mine and quarry for the both upper and lower reservoir. The project would be located in the City of Elmhurst, Illinois within 20 miles of downtown Chicago. EQPS is being developed by DuPage County, Illinois, and appears to be an attractive project due to its flood control capabilities, renewable generation opportunities and potentially low environmental impacts, and to its proximity to electrical transmission and a large load center. The project would divert and gravity-feed water from an above-ground source into an underground powerhouse, where it would travel through the pump-turbine. The power generated would be delivered to the power grid during peak demand periods. Once through the turbines, the water would then be temporarily stored in abandoned mine caverns before being pumped back to its original source using lower-cost (off-peak) power. The EQPS has an initial design capacity of between 50 MW and 250 MW with an estimated 708.5 GWh of energy storage potential.
Riverbank Wisacasset Energy Center (RWEC)
This is a proposed 1,000-MW pumped hydroelectric storage facility located 2,200 feet underground in Wisacasset, Maine. The RWEC project would divert water into its underground shaft down 2,000 vertical feet to drop into a powerhouse containing four 250-MW pump-turbines. Similar to the EQPS, the water passing through the pump-turbines would be stored in large underground reservoirs (caverns) before being pumped up using low-cost, off-peak power.
Gravity Power-Grid-Scale Electricity Storage System
Gravity Power, LLC, is also proposing to develop a grid-scale electricity storage system. The company’s Gravity Power Module (GPM) uses the established principles of pumped storage combined with a large piston that is suspended in a deep, water-filled shaft. Once the shaft is initially filled with water, no additional water is required. As the piston drops, it forces water down the storage shaft, up the return pipe and through the turbine, and spins a pump-turbine motor/generator to produce electricity. To store energy, power purchased off-peak drives the pump-turbine in reverse, spinning the pump to force water down the return pipe and into the shaft, lifting the piston.