Energy Vault’s Rudong project provides a practical test of gravity energy storage because it was built in China within an environment presumed to be favorable to this type of project: local supply chains for concrete, steel, motors, and power electronics; government support; grid coordination; and an experienced Chinese construction partner. Nevertheless, the analysis finds that the project’s economic outcome appears weak when compared with a modern Chinese battery system providing the same service.
Rudong has a capacity of approximately 25 MW and an energy capacity of 100 MWh, meaning it is designed to provide four hours of operation at maximum power. It includes a structure approximately 148 meters high, more than 12,000 blocks nominally weighing 25 tons each, along with 96 cranes and thousands of piles drilled beneath the facility. Energy Vault’s project page still describes it as being in the commissioning phase, despite indicating that full grid connection was expected by the end of 2023.
Comparison on the Basis of the Same Service
The importance of the comparison lies in the fact that four-hour batteries are not a rare experimental technology in China, but have become infrastructure purchased in a market moving toward greater standardization. The analysis cites a 100 MWh battery plant built using Sungrow PowerTitan 2.0 units; each 20-foot container-sized AC unit contains 5 MWh of batteries and a 2.5 MW power converter. According to Sungrow, a complete plant of this capacity requires approximately 1,200 square meters.
By contrast, the Rudong tower alone occupies approximately 11 times that area. The comparison published in the report also places the central estimate of the project’s capital cost at approximately eight times that of an equivalent contemporary Chinese battery system, with much higher operation and maintenance costs and embodied carbon emissions. This is not a comparison between a Chinese project and a high-cost Western battery, but between two technologies within the same Chinese industrial economy.
What Does Gravity Storage Actually Provide?
The concept has specific advantages at the level of the storage components. The blocks can be manufactured from low-value mineral materials and waste, with the need for bottom steel plates and a protective layer. They also do not chemically degrade in the same way as battery cells, do not face the risk of cell thermal runaway, and the storage medium may last for decades.
However, the blocks are not the entire storage system. For an inexpensive block to become useful to the grid, it must be integrated into a large structure with deep foundations, cranes, horizontal transport equipment, motors, generators, brakes, transmissions, control systems, sensors, and power electronics. Therefore, the lower carbon associated with the block material does not eliminate the carbon resulting from the civil engineering work and equipment required to move thousands of heavy objects repeatedly.
Why Does This Matter?
The Rudong case illustrates the difference between a technology’s technical feasibility and its ability to compete with alternatives at the full-system level. The project demonstrated that gravity block storage can be engineered at utility scale, but this does not prove that its complex structure justifies its cost when batteries provide compact units and four-hour discharge service.
The article also indicates that Energy Vault expanded its activities from the exposed six-arm crane concept to the enclosed EVx structure, then entered the public-company market during the special purpose acquisition company wave in the clean-technology sector. The company subsequently began announcing lithium-ion battery projects, and gravity storage became a small part of a broader portfolio that includes battery-system integration. These developments do not make the Rudong project an engineering failure; establishing a facility of this scale and coordinating lifting equipment is a significant engineering achievement. However, they bring the question back to whether purchasing additional complexity is worthwhile instead of using mature battery solutions.
Some comparisons still require independent scrutiny before they can be turned into a final judgment on the technology. A full assessment should define the boundaries for counting carbon, the equipment’s maintenance and availability requirements, and the nature of the required service. It should also compare battery lifetimes while accounting for their degradation and replacement, rather than treating them as a permanent asset. According to the article, these aspects determine whether the long-life advantage of gravity storage offsets its cost, space requirements, and complexity.