From pv magazine USA
The gravity-based energy storage tower developed by Energy Vault has reached commercialization, with the company signing an agreement with DG Fuels to supply 1.6 GWh of energy storage.
The tower will be charged with solar photovoltaic energy. The dispatched storage will support the creation of renewable hydrogen, biogenic based, synthetic aviation fuel, and diesel fuel.
The agreement is estimated to provide Energy Vault with $520 million in revenues across three projects. The first, a 500 MWh storage tower in Louisiana, is expected to commence in mid-2022. Additional projects are planned in British Columbia and Ohio.
Energy Vault’s design includes a six-armed crane tower that lifts composite blocks using an electric (solar-powered) motor. The lifted blocks are stacked, which creates potential energy. As the blocks are lowered, the energy is harvested and dispatched for use.
The tower is controlled by computer systems and machine vision software that orchestrate the charging and discharging cycles. A range of storage durations from two to 12 hours or longer is achievable, said the company.
Energy Vault said the tower’s design is based on the physics of pumped hydroelectric energy storage. However, as a solid “mobile mass,” the composite blocks do not lose storage capacity over time. The company said the tower has an 85% round-trip efficiency and a 35-year-plus technical life.
The composite blocks can be made cheaply, said the company, using excavated soil from the construction site, waste materials like mine tailings and coal ash, and even fiberglass from decommissioned wind turbines.
DG Fuels will deploy the storage systems to power its carbon conversion fuel process. The company said it is targeting a 93% carbon efficiency rate for its aviation fuel. It will also use the tower’s energy to power water electrolysis for both hydrogen and oxygen feedstock production.
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It baffles me that no journalist calculates the physics of this thing and it still gets money from big companies. It is such an inefficient way of energy storage. A waste of money.
Actually, the efficiency of this storage is very good, with 90%+ round-trip efficiency. It doesn’t have very good specific energy (energy stored per weight) or energy dense (energy stored per volume) and you need to lift a lot of weight very high to store not much, but if you’ve got the space the simplicity and efficiency can be worth it.
What completely baffles me is they say they they are going to use it for carbon conversion and hydrogen electrolysis. Hydrogen has a round-trip efficiency of less than 50% and I think carbon conversion is about the same. Why bother storing energy at all when you are just going to throw half of it away converting it to another less efficient form of energy storage? Instead you could just directly run off the solar and just shut down during the night.
I wasn’t talking about round trip efficiency alone. The amount of materials needed, the limited durability and the high maintenance costs make for a very inefficient way of storing energy. People are opposed to windmills “close” to their homes, this ugly mastodont is far worse. The comments about hydrogen and carbon capture indeed make a bad thing even worse. This should not even be news at all.
It really bothers me that jounalists just copy paste a press release of a company without any critique. They should use their ‘power’ to uncover hoaxes like this. Now they are just puppets of dishonest companies.
500MWh? This must be typo!
100m tall tower needs to lift… 1.8 MILLION of metric tonnes (or however you call those in US). According to Wikipedia Empire State Building weights only 360 000 tonnes…
I tried several times to get a similar comment published. I finally guessed it was rejected because I had links to sources, mainly an online potential energy calculator.
Yes, you would have to lift half a billion tons of concrete the height of the Empire State to store 500GWh of energy. That doesn’t pass my back of an envelope test!
The problem is this thing is six high reach crane that should pack large, heavy blocks with precision continuously for tens of years. The maintenance will be not easy or cheap.
Also the blocks should be strong enough to be packed how high? You are building a large tower from them and then continuously assemble.and disassemble them and they want to make them from soil? The blocks will be not cheap. Each of them needs to hold maybe a hundred layer on top of it, and you will drop and lift them every day.
This thing will be expensive.
Why is my calculation not being published?
With a tower the height of the Empire State Tower (376m) a 1 ton weight will store 1MWh.
What is your definition of a 1 ton weight?
And also what equation do you use to get the result 1MWh.
I would use basic Wp=mgh. The result would be in Joule or watts per second.
I used an online potential energy calculator. omnicalculator-DOT-com/physics/potential-energy
My posts with the URL exposed were not published.
You are correct. The mass needed to store 500MWh of energy with 85%efficiency and a height of 100m is over 21 million tonnes! Cranes are expensive mechanical devices that need constant maintainence to have a safe, trouble free life. I find it hard to believe that this impractical device is taken seriously.