Imagine a giant brick of highly compressed dirt—the size of a pickup truck, but at 24 tons, about five times heavier. Powered by solar panels or wind turbines, the elevator lifts more than 300 feet up the side of a massive building, and a trolley stores it inside. But she is not alone. An automated system lifts and stores hundreds more bricks, like giant candy bees, as the sun shines and the wind blows.
Now imagine the building’s control system lowering hundreds of bricks one by one, spinning electrical power generators in the process. It goes down every evening as power demand rises but solar panel production is fading away.
In reality, the building full of bricks is a giant battery that stores energy with gravity rather than chemistry.
Gravity batteries are a potentially significant solution to a critical problem in the green energy revolution: making sure that electricity is available when we need it, not just during the times when the sun and wind supply it.
It is not just an idea. With two sites under construction — one in Rudong, China, just north of Shanghai, and the other in Snyder, Texas, about 250 miles west of Dallas — the startup Energy safe He will seriously begin to test the feasibility of gravity storage technology. A previous pilot generated 5 megawatts of power, but these two facilities and their expected successors will show whether gravity storage is economical and efficient enough to operate on a large scale.
power when the sun goes down
You may think that put Solar Panels Having your rooftop would help combat climate change, but without any form of energy storage in your home or on the grid, you’d likely rely on carbon dioxide and coal-emitting power plants to power your home’s lights, TV and dishwasher as the sun sets.
Energy Vault has tested its technology on a smaller scale in Switzerland, where the 170-person company is headquartered. The two EVx systems under construction are much larger. Chinese system designed for waste management and recycling company China Tianying, in a 400-foot-tall building and will have an energy storage capacity of 100 megawatt-hours. this enough for power 3,400 homes for a full day, and the system should be complete by June. The Texas system, in a 460-foot-tall (but narrower) building, would provide an energy company Enel With a capacity of 36 megawatts per hour.
Solar panels and wind turbines now generate power cheaper than coal and natural gas plants, making them an obvious choice in the push to replace fossil fuels. Solar costs fell 83% from 2009 to 2023 Wind costs fell 63% over the same period, according to the investment advisory and asset management firm Tracking Lazard. But in many parts of the country, new solar panels often provide plenty of power during the middle of the day without helping in the evening.
The mismatch between energy production and energy use is responsible for the notoriety.”duck curve,” a bird-shaped graph showing the increasing variability with each passing year. This variance makes it difficult for utilities to adapt to rapid changes in demand and means fossil-fuel energy sources such as natural gas “peak stations” supply power in the evening.
“If we want to wean ourselves more and more off fossil fuels and replace that with intermittent renewable generation, the only way to solve that is storage,” said Robert Piconi, CEO of Energy Vault.
Energy Vault is not alone. another startup, gravityhe built 250 kW demonstration system And it plans a larger system from 4MW to 8MW in an unused mine shaft.
Energy storage cost is key
Gravity storage is just one way to mitigate the rushes of wind and solar energy. Large batteries like Tesla Megapacks — industrial-scale versions of the same batteries that power your phone or electric car — are increasingly common in the power grid. “Water pumping,” an ancient form of gravity battery that pumps water into an elevated reservoir and then generates power as it flows downhill, has been in use for decades but is attracting new interest. Other methods include filling underground chambers with compressed air, storing hydrogen that later powers fuel cells, and developing different types of batteries, such as zinc batteries and flow batteries.
The Energy Vault’s EVx system lifts these 24-ton stones hundreds of feet to recover that potential energy by lowering them when the energy is needed. The bricks are made of dirt compacted with a polymer matrix and transported within the system using a trolley setup below the bricks.
Energy safe
Cost will be a major factor in determining the prevailing warehousing technology, including upstream manufacturing and continuous operations.
“At the end of the day, everything will come down to price,” said Celine Lu, an energy analyst at a consulting firm. Clinic Group. For gravity storage, she said, questions about the total cost still remain.
Indeed, A.J 2022 US Department of Energy Study concluded that gravitational energy storage is relatively expensive in smaller facilities. Where they are most economical is in high capacity systems that generate power for relatively long periods of time – 10 hours or more.
Energy Vault did not disclose the cost of the two systems under construction, but agrees that the technology offers advantages for long-term energy needs.
Longevity is a cost factor over the life of the plant. Batteries lose capacity with use, the same way your phone doesn’t run for long after two years of ownership, but gravity storage components, like pulleys and generators, can be preserved.
“The key to our value proposition is the non-degradation of the storage medium,” said Marco Terozin, mechanical engineer and head of commercial products at Energy Vault. “We offer a warranty on the system for at least 35 years.”
Although Energy Vault has only taken its first steps in proving the value of the technology, two customers have concluded that it is worth paying for today. The company said the 100 megawatt-hour system in China is only the first there. The country expects to finance another 4 to 6 GWh later – 40 to 60 times more than the initial plant.
How does Energy Vault’s EVx work?
The Energy Vault’s EVx Gravity Storage System is a giant rectangular building that is largely automated. Here’s how it works.
The bricks at the core of the system measure 3.5 by 2.7 by 1.3 meters (about 11 by 9 by 4 feet) and weigh 24 metric tons. It’s made from 99% compacted dirt with some water and a polymer blend to set it in, using a recipe from a Mexican building materials company. cemex. It is 2.4 times denser than water and about the same as concrete.
The first large-scale gravity-based energy storage system from the Energy Vault in Rudong, China, is hundreds of feet high.
Energy safe
The bricks are stored side by side inside the building, like dominoes jammed together. Before it is raised or lowered, the trolley system conveys and rotates each brick to the elevator.
The bricks are located at the top eight levels of the building for energy storage and go down to the corresponding bottom eight levels for energy generation. Each brick, which is going down at 1.9 meters per second (6.23 feet), is about a megawatt, Troisin said. This is enough to power 2,000 refrigerators.
Once each brick reaches the bottom, it is automatically transported to the trolley system and moved towards the center of the building.
Making the building taller, with longer trolley tracks, meant more bricks could be stored for longer hours of power generation. Making the building wider, with more elevators, means the system can generate a higher rate of energy.
In terms of efficiency, Energy Vault guarantees that EVx systems will generate at least 80% of the energy required to lift and move bricks, including factors such as friction. This overall efficiency is comparable to pumping water.
The key to the Energy Vault’s functioning is the control system that decides when and where to place bricks for optimal storage and even energy production.
Bill Gross, CEO of Idealabs and co-founder of Energy Vault, said Climate Technology Conference in March.
The maximum output will be 25 megawatts in the China system and 18 megawatts in the Texas system.
Overcoming gravity storage challenges
Energy Vault settled on its current design after evaluating several other options—gravel in carts, water in tanks, concrete blocks suspended from cranes.
The EVx was designed to overcome the problems of those designs. It’s weatherproof, which means bricks don’t get wet or chipped away, for example.
The Energy Vault doesn’t put all of its energy storage eggs in the gravity basket. a Contract with Pacific Gas and Electric Company in California, could lead to a system to power the city of Calistoga for up to 48 hours with a mixture of hydrogen fuel cells and batteries. Hybrid systems with gravity and battery storage also make sense, Tyrosen said, as batteries can respond very quickly to a surge or spin.
With Energy Vault plants heading into production, we should start to get a better idea this year of how well gravity storage works. “This will be a critical year for Energy Vault,” said Cleantech Group Law. “The proof is in the dessert.”
The company is not profitable, reporting a Net loss of $78 million for 2022 On revenues of $146 million. And her The stock is down 89% year-over-yeara fate many startups have suffered due to economic troubles and skeptical investors.
Piconi of the Energy Vault is convinced the company is on the right track toward making energy storage more economical, though.
“Wind and solar are much cheaper than fossil fuels now…the problem is that storage is usually 10 to 15 times that,” Piconi said. “We have to get there.”
Correction, 9:26 a.m. PT: An earlier version of this story misstated Energy Vault’s 2022 financial results. It posted a net loss of $78 million on revenue of $146 million.
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