Tower of power: gravity-based storage evolves beyond pumped hydro

Energy Vault has created a new storage system in which a six-arm crane sits atop a 33-storey tower, raising and lowering concrete blocks and storing energy in a similar method to pumped hydropower stations. How does the process compare to other forms of energy storage, such as batteries and pumped-storage hydro?

The influx of renewable energy to national power grids has hit something of a bottleneck. While technological innovation in energy storage has taken off, the current infrastructure is limited in the amount of energy that can be stockpiled from intermittent sources such as solar and wind power.

Renewable energy is becoming more affordable, but the unstable nature of production and reliance on the right solar and wind conditions has held back renewables in the quest to replace fossil fuels.

Taking its inspiration from hydropower, Switzerland-based start-up company Energy Vault has developed a new kind of storage method. The system essentially harnesses the power of the Earth’s gravitational pull, using concrete bricks that are raised and lowered automatically by a crane.

How does the technology work and how does it compare to other forms of energy storage?

Modernising a time-honoured technique

The storage technology incorporates basic principles of physics that have been used in the production of pumped hydropower plants for years. In pumped hydro systems, water flows down from an upper reservoir to a lower reservoir, passing through and rotating a generator or turbine. Water is then pumped back up from the lower to the upper reservoir, at some electrical cost, which again rotates the turbine and the system is repeated, thus generating and containing electricity.

In a similar vein, Energy Vault has developed a six-arm crane to lift 5,000 concrete blocks – weighing 35t in total – up and down a 33-storey building, which store gravitational potential energy when they are raised, and release it as they are lowered.

“In each gravity-based energy storage, a certain mass is moved from a lower point to an upper point – with the use of a pump, if water for example – which represents ‘charging’ the storage, and from a higher to a lower point which creates a discharge of energy,” says Energy Vault CEO and co-founder Robert Piconi.

“Increasing the height of a large mass implies storing electricity in the form of potential energy. On the other hand, in order to release the power, kinetic energy is created from the downward movement of the mass, thereby creating the electricity.”

The innovation comes in its application of cloud-based automation software, which operates the six-arm crane mechanically, and manages the distribution of power to either store energy from solar and wind assets, or discharge it to the grid when needed.


Source :

Smart Grid Bulletin May 2019

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