Energy

Energy Vault to build grid-level, gravity-fed battery from a tower of concrete blocks

Energy Vault to build grid-lev...
Energy Vault has launched a new grid-level energy storage system that uses concrete blocks, stacked in a tower
Energy Vault has launched a new grid-level energy storage system that uses concrete blocks, stacked in a tower
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Energy Vault has launched a new grid-level energy storage system that uses concrete blocks, stacked in a tower
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Energy Vault has launched a new grid-level energy storage system that uses concrete blocks, stacked in a tower
In Energy Vault's new system, a six-armed crane lifts concrete blocks from the ground into a tower loaded with potential energy, which is unleashed by lowering the blocks back to the ground
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In Energy Vault's new system, a six-armed crane lifts concrete blocks from the ground into a tower loaded with potential energy, which is unleashed by lowering the blocks back to the ground
The Energy Vault system goes from fully charged (left) to empty (right)
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The Energy Vault system goes from fully charged (left) to empty (right)

Meeting our growing energy demands without continuing to destroy the planet might be one of the biggest challenges of our time, and it calls for some pretty creative solutions. Swiss company Energy Vault has just launched an innovative new system that stores potential energy in a huge tower of concrete blocks, which can be "dropped" by a crane to harvest the kinetic energy.

With a focus on storing energy from intermittent renewable sources such as wind and solar, the Energy Vault takes advantage of some fundamental physics. If you coil a spring, for example, you're packing it with potential energy – as soon as you let it go, that energy is unleashed as the spring extends itself back out. This new system scales that up to the grid level.

In this case, that potential energy is stored inside huge concrete blocks. To charge up this skyscraper-sized "battery," a six-armed crane lifts the blocks off the ground and stacks them up around its base, creating a tower. To discharge, the crane simply lower the blocks back to the ground, converting the kinetic energy from the descent into electricity. Proprietary algorithms calibrate and control the charge and discharge cycles to make it as efficient as possible.

The Energy Vault system goes from fully charged (left) to empty (right)
The Energy Vault system goes from fully charged (left) to empty (right)

According to the company, the general concept was inspired by pumped hydro plants, which also tap into gravity. In those systems, power is generated by water rushing downhill through turbines, and during times of low energy demand, that water is pumped back up to the higher reservoir to reset the energy potential.

The company says each tower can be built to have a capacity of up to 35 MWh and 4 MW peak power based on their size, with the modularity of the system allowing capacity to be increased by building more towers. While it might seem big and cumbersome, the crane can be generating power in as little as 2.9 seconds, and has a roundtrip energy efficiency of about 90 percent. And unlike chemical storage systems, once those bricks are stacked up, that energy won't "leak" out or degrade.

That said, Energy Vault claims that the concrete blocks don't degrade over time, but to us it seems like years of exposure to the elements could slowly wear away at them. Still, the company says the system should have a lifetime of 30 to 40 years.

In Energy Vault's new system, a six-armed crane lifts concrete blocks from the ground into a tower loaded with potential energy, which is unleashed by lowering the blocks back to the ground
In Energy Vault's new system, a six-armed crane lifts concrete blocks from the ground into a tower loaded with potential energy, which is unleashed by lowering the blocks back to the ground

Another possible argument against the system is that concrete is one of the most environmentally damaging materials to produce, so building the components in the first place could leave a big footprint. But Energy Vault says the blocks are made out of concrete debris that would normally be headed for landfill, reducing both cost and waste materials. It also says it will look at using various concrete-based composite materials to suit different regions around the world.

The ultimate goal of the system is to store energy produced by renewable sources like wind and solar, keeping the lights on even when the wind isn't blowing or the Sun isn't shining. It should be able to do so at a lower cost-per-kilowatt hour than other storage systems like Tesla's huge Li-ion battery in Australia, or the brine4power redox flow battery in Germany.

The first 35-MWh Energy Vault system is due to be deployed in India for The Tata Power Company in 2019.

Source: Energy Vault

19 comments
VincentWolf
I had this same idea and people thought I was a quack! But you can make solar barges to carry small mountains of heavy materials out to sea and drop them into deep Aleutian trenches which are 35,000 feet deep and harvest a huge amount of power from that then return on those solar barges to harvest more mountain and repeat ad infinitum. Of course in a few thousand years this might raise sea levels !!
Anne Ominous
This seems very much overly complex, when a similar system that simply drags heavy cars on rails uphill is much simpler and easy to construct, and therefore probably much cheaper to build and operate. And certain variations on pumped hydro storage are even simpler, and offer more promise.
SimonClarke
Excellent use of physics. you could do the similar thing with a house, you generate spare electricity you house would rise and as it is used it lowers. A vertical movement of only 0.3m 1ft would be sufficient to provide a back up as a typical UK house weighs around 60 Tonnes.
tomtoys
I asked a physics teacher friend 15 years ago if a radio could be powered by having it descend like a weight of a clock. Not enough power she said. Now they are manufactured for the Third World, with a heavy weight instead of just the radio. Living now on a canal boat. Going through locks I think of all that energy going from a higher level to a lower. A British narrow canal might hold a volume of more than 2X3X20 metres, i.e., around 120 cubic metres, around 120 tons. A turbine in the outflow?
Altronix
I'm afraid I can't understand this. As far as I can recall it would take as much energy raising the blocks as can be collected from their release, even at 100% efficiency. Unless renewable energy sources are used to raise the concrete, in which case it's more like a storage unit than a power generation device
michael_dowling
Altronix: Yes,this thing is meant to store excess power from renewable resources. The main stumbling block with renewables is there is no economical way to store excess power. VincentWolf: This is not the first gravity storage scheme I have heard about. There was a plan to dig a deep hole,and store power in a massive weight ,and return it by lowering the weight to the bottom of the hole.I bet this new proposal would be cheaper to construct than digging a hole 1/2 a mile deep. Anne Ominous: The problem is not every location has hills to store power in heavy cars pulled uphill.
mphase
SimonClarke: I think you might be surprised how high you would need to raise a 60 tonne house to store a single days worth of electrical use. Lets assume 4500 kwh/year which on average is about 12 kwh per day. If you raise a 60 tonne (60000 kg) house 0.3 metres the "stored energy" is equal to E=mass*gravity*height = 60000 kg*9.81 m/s2*0.3 m = 176 kilojoules = 0.049 kwh. So to get 12 kwh we need 245 times more height or we need to raise the house 73 metres (ignoring all efficiency losses). And this is why raised mass storage doesn't work. You need a lot of mass or a lot of height and typically this only works when you can pump a lot of water between very large reservoirs. Not to mention a giant tower of concrete blocks would be ugly and no one would allow the tower to be built anywhere close to them.
guzmanchinky
Doesn't India have a lot of earthquakes? Having concrete blocks up in the air isn't a bit unstable?
Username
Mphase, 12kwh per day is the equivalent of 500w continuously for 24h. This seems excessive to me for the average house. As for nobody would allow construction near them, the tower would most likely be placed near the power generation, i.e. windmill farm.(as illustrated).
ei3io
Let's imagine maintaining a single water cooled pump with its turbine drive for water weight gravity storage contained in enclosed pipes and tanks compared to all those cranes, booms, rotating bearings, cables, motors, block & tackle, etc with all its added material strength against wind & earthquake damage to store gravity energy.