Gravity and renewable energy

Energy Vault’s energy storage system in the Swiss town of Arbedo-Castione. (Source: CNN)

In the Swiss town of Arbedo-Castione, there is a giant crane tower up to 70m high. Six crane arms reached out, lifting giant squares into the sky. But these are not construction concrete blocks, this tower crane does not serve the construction.

It’s a giant energy storage system, designed by the US-Swiss company Energy Vault, that relies on gravity and 35-ton concrete blocks (made from recycled materials) to store and release energy. discharge electricity.

When power demand is low, the crane uses excess electricity from the national grid to lift the concrete blocks to the top of the tower. As power demand increases, these blocks are lowered, kinetic energy is converted into electricity. With this design, the system can store energy for many years.

Environmentally friendly solution

“Companies are under increasing pressure from governments and investors to reduce carbon emissions from fossil fuels,” said Robert Piconi, founder of Energy Vault.

Relying on renewable energy for a stable source of electricity is important. Unlike fossil fuel power plants that can operate day or night, solar and wind power operate intermittently. If there are clouds blocking the sun or the wind is calm then power generation will decrease, Mr. Piconi said.

According to him, to compete with fossil fuels, renewable energy needs to have reserves to use when needed.

One solution to this problem is lithium-ion batteries, which are connected to power grids around the world. They can be charged with electricity generated from wind and sunlight and release energy on demand.

According to Dan Shreve, energy storage expert at Wood Mackenzie, an energy research and consulting firm, the technology has evolved rapidly in recent decades. They are mostly used for short-term energy storage (about six hours) and as decarbonization activities increase, the need for longer-term storage will increase.

On the downside, lithium is a limited resource, only found in certain areas of the world, and its extraction can be harmful to the environment. Despite the sharp decline in production costs over the past decade, battery prices will start to soar in 2021 as demand for lithium outstrips supply.

For these reasons, Mr. Piconi said, while batteries are great for electric cars, they are “not ideal on a large scale.”

The Energy Vault decided to rely on a method developed more than 100 years ago: pumping water to store hydroelectricity. During off-peak times, the turbine pumps water from a lower-level storage tank to a higher-level storage tank, and during high demand, the water is let down to the turbine, generating electrical energy.

Mr. Piconi said Energy Vault also relies on gravity but “instead of using water, we use heavy concrete blocks”.

In this way, the company’s operations are independent of the terrain, do not have to dig reservoirs or build hydroelectric dams or things that can harm the environment.

Simple, elegant

Since Energy Vault successfully established a prototype in Switzerland in 2020, the company has shifted its design from a tower model (which can be as high as 200m), to 20-story buildings called “centers”. energy storage”.

The “energy recovery center” buildings about 100 meters high use the same concrete made from soil and waste. Artificial intelligence will control these heavy blocks to move up and down inside the building, helping to determine the optimal energy “charging or discharging” time depending on needs.

Centers vary in size, ranging from 1.5 to 20 acres depending on the amount of storage. They can be built near solar or wind power plants.

Mr. Shreve commented that Energy Vault’s technology is “simple and useful”, but the system may not yet be able to compete on cost with lithium-ion batteries.

Even so, the market is lacking in battery alternatives. Several other companies, such as UK-based Gravitricity, are also exploring gravity-based energy storage, but not yet on the scale of Energy Vault.

This year, Energy Vault will start building “energy recovery centers” for fuel company DG, to continuously provide green energy to the aviation industry. The company also signed contracts worth up to $880 million with the world’s largest oil producer – Saudi Aramco, metallurgical company Korea Zinc, and mining giant BHP.

Mr. Piconi is confident that this technology will help accelerate the transition from fossil fuels to renewable energy.