Energy Vault completed a gravity-based energy storage installation in Rudong, China, rated at 25 megawatts and 100 megawatt-hours of capacity. The facility operates by lifting and lowering over 12,000 concrete blocks inside a 148-meter-tall structure to store and discharge energy. The project was constructed in favorable circumstances, including access to established supply chains for materials and construction expertise, government backing, and coordination with local grid operators.
The Rudong facility demonstrates that gravity storage using stacked masses can be engineered at commercial scale. However, technical analysis reveals significant economic and practical disadvantages when compared directly against lithium-ion battery systems operating in the same market. A comparable 100-megawatt-hour battery installation requires substantially less space—roughly 1,200 square meters versus Rudong’s approximately 13,200-square-meter footprint. Capital costs for the gravity system are estimated at roughly eight times higher than equivalent battery storage, while operating and maintenance expenses are also considerably elevated.
The core technology offers certain theoretical advantages. The storage blocks can be manufactured from low-value mineral and waste materials and do not experience electrochemical degradation or thermal runaway events. However, the overall storage system requires extensive supporting infrastructure including deep foundations, multiple lifting systems, horizontal transport equipment, motors, generators, brakes, transmissions, controls, sensors and power electronics. The manufacturing and operational carbon footprint of this supporting infrastructure is substantial, comparable to natural gas generation on a per-kilowatt-hour basis.
Energy Vault’s corporate direction has shifted significantly since the project was conceived. The company transitioned from its original crane-based design to an enclosed architecture, pursued a public listing during the cleantech investment boom, and subsequently expanded into conventional lithium-ion battery projects. Gravity storage now represents a minor component of a broader portfolio that includes battery integration and hybrid energy systems.
The Rudong installation represents a legitimate engineering achievement in terms of structural design and mechanical coordination. However, utilities and investors face a central question regarding whether the added complexity and cost of gravity storage systems justify their deployment when battery systems already provide equivalent four-hour storage capacity in more compact, manufactured modules.
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