Stacking Blocks

Is low-tech the best bet for energy storage?


The science is simple. Lifting mass against gravity stores energy that can be released when the mass falls. An innovative energy storage system is putting that science to work today with cranes and concrete blocks.

The Energy Vault system, developed by entrepreneur Bill Gross and Swiss inventor Andrea Pedretti, can store a total of 20 megawatt-hours. The system is composed of concrete cylinders weighing 35 metric tons each that are positioned around a 120-meter crane. When there is excess energy on the grid, a computer algorithm directs the crane arms to locate and lift a concrete block. This action is driven by a motor that uses the surplus grid energy. The crane arm stacks the blocks on top of one another to create a tower.

Join us at the Leading Gathering of Distributed Generation and Microgrid Professionals at the 6th Annual HOMER International Microgrid Conference in San Diego, October 8-10thSecure Your Spot Today!

When the grid is experiencing high consumer demand and is depleted, the crane simply lowers the blocks to the ground. As it does so, the crane’s motors are driven in reverse by the gravitational energy, generating electricity.

According to Quartz, the round-trip efficiency of the system is about 85%. In comparison, lithium-ion batteries offer up to 90% efficiency. Whereas its simplicity and efficiency may be on par with pumped hydro, because the system is not reliant on water, it can be sited in any geographic region.

To date, the Energy Vault system has proven its energy storage capabilities at a test plant in Biasca, Switzerland. But developers explain that because it uses off-the-shelf commercial hardware that requires little maintenance and does not lose capacity over time, the system offers relatively low-cost storage and a long equipment life cycle.

What are your impressions? Do you think there’s value in considering simple solutions to modern-day energy issues?



  • I am concerned about the maintenance and the difficulty of stacking the blocks. After a while, I expect a few tumbles.

  • Jonathan McClelland.

    It sounds reasonable if sited correctly, i.e. low seismic likelihood, inexpensive land, available maintenance and monitoring workforce which presumably is already on site to manage the PV facility. Lithium Ion is more efficient, but it’s in increasingly higher demand due to expansion of the EV market and point of use backup for electricity needs. Mark’s concern about “expecting a few tumbles is realistic, but can be dealt with by proper siting (bedrock), and accurate monitoring of the stacking. The question remains, “How expensive is the initial construction, and what is the payback period in energy costs?”


Leave a Reply

Enter Your Log In Credentials