Michigan Tech scientists look at abandoned mines for hydro pumped energy storage

via www.esru.strath.ac.uk This illustration shows a typical Pumped Hydro scheme, in which water is pumped from a water body uphill to a reservoir, which can later be reversed to flow downhill, spinning a turbine to generate electricity before being discharged back into the water body. This system can be adapted to perform the same function inside of abandoned mines, using old mines for hydro storage.

HOUGHTON — Energy storage is approaching a critical stage. It is as Timothy Scarlett, associate professor in the Department of Social Sciences at Michigan Technological University (Michigan Tech), remarked, a globally urgent, pressing technology problem that affects the majority of people in the world.

The most pressing challenge currently facing electrical grids everywhere, said Scarlett, is energy storage.

“It is the single biggest problem,” he said.

There is potentially, a way of addressing that problem.

Scarlett is one of a team of scientists looking at adopting existing hydropump energy technology to abandoned deep-shaft mines.

In 2019, the group of engineers and scientists began studying the potential reuse of the Mather B Mine, in Negaunee, as a facility for underground pump-hydroelectric energy storage–a system similar to the pump-hydro storage plant at Ludington, Michigan, but entirely underground.

Ludington’s Pumped Storage Plant is hailed as an engineering marvel. The 27 billion gallon reservoir, measuring 2.5 miles long and one mile wide, can generate up to 1,872 megawatts of electricity, enough power to serve a community of 1.4 million residential customers.

Consumers Energy and Detroit Edison, co-owners of the plant, upgraded to the Pumped Storage Plant to increase the generating capacity from 1,872 megawatts to 2,172 megawatts and replacing its six turbines with more efficient models. The six-year project was estimated to increase the plant’s generating capacity by 15%. It is expected to last another 50 years. The Lake Winds Energy Park constructed in Summit and Riverton townships just east of the plant also increased the pumped storage capacity,

While the Ludington plant pumps water from Lake Michigan to its reservoir, then allows it to drop, spinning turbines before returning to the lake, Scarlett said the technology can also be also installed in deep-shaft mines.

“Right now, the only place we can really develop (hydro pumping storage) within industrialized countries is in abandoned mines,” he said.

Scarlett said the technologies of electricity generation are changing, transitioning from large, centralized generation facilities, like coal-fired plants, nuclear-powered plants, and natural gas plants, to irregular generation, such as solar, wind, and other alternative power.

“But as the renewable energies, particularly like solar and wind, get added to the grid — because they are so cheap at this point,” said Scarlett, “people want to add them, but grids are not designed to handle the power, because you have to match the curves of fluctuating supply and demand.”

Even with coal-powered or nuclear powered plants, demand fluctuates more quickly than the power plants can respond.

“The system needs to have a way to shave the top off the demand peak and bank that energy when demand drops low when the system is producing more power than it’s designed to,” he said. “So, you have that need in the system already,” Scarlett said, “…that system copes with what are referred to as peaker plants.”

Science Policy Circle states that “peakers” are known as the last power plants to be turned on and last to be dispatched. Peakers usually turn on when energy demand is at its highest. A commonly used fuel source for peaking plants is natural gas, which is a fossil fuel. Peaker plants are relatively less efficient and could have more emissions per kilowatt hour of energy generated. Scarlett said peakers can be hydro-powered, or use some other type of power.

“These plants sit there, 20 hours a day and don’t do anything,” said Scarlett. “Then, as an example, when everybody starts to wake up in the morning at 5:30, as the power demand starts to ramp up, the power plants start to ramp up production too. But, those two curves can’t match each other.”

At some point, the demand surpasses the supply on the grid, and these peaker plants are designed to instantly, in a matter of seconds, kick on and pump electricity into the grid, supplying that peak bit of demand for electricity, he explained.

Scarlett compared the efficiency of peaker plants to a rapidly accelerating a car, where large amounts of fuel are consumed in a small amount of time as the car speed increases.

“So, these peaker plants are ridiculously inefficient, in a place like Ludington, water flumes can be opened, allowing turbines to spin and generate electricity, again in a matter of seconds,” Scarlett said, “it was more energy efficient and cost-effective to use pumped hydro storage to store electricity than it is to use peaker plants.

Science Policy Circle concurs, stating that there are hydropower stations that can reach maximum generation in 16 seconds. Further extension of this technology is pumped hydro power. Water is pumped to a higher position during the off peak and stores electricity generated to facilitate peak power later.

The city of Ludington’s website states that: “At night when the demand for electricity is low, the reversible turbines pump water uphill from Lake Michigan through six large pipes to the reservoir. During the day when demand for electricity is higher, water flows back down through the penstocks, turning turbines that produce power. This simple technology enables the plant to respond quickly to the highs and lows of Michigan’s energy demand.”

Scarlett said anyone who operates a car can understand that concept.

“When you run your car where it’s really energy efficient by maintaining a constant speed or slowly increasing your speed,” he explained, “or when you decrease your speed, it’s not so important to the gas engine, because you’re using your brakes.”

Someone who stomps on gas a lot, zooming around, then braking, the vehicle is being run inefficiently, burning gas less efficiently.

While peaker plants are inefficient and expensive, Scarlett continued, they are one of the leading ways of rapidly increasing the electricity supply to the grid. Hydro pumping storage, on the other hand, is far more efficient and cost-effective, as the hydro pump storage plant, in Ludington has been demonstrating for the past 50 years.


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