Huai’an Salt Cavern project

Executive Overview

The Huai'an Salt Cavern Compressed Air Energy Storage (CAES) project is a 600 MW / 2,400 MWh advanced adiabatic CAES facility in Huai'an, Jiangsu Province, China — the world's largest operational CAES facility as of March 2026, superseding the 300 MW Yingcheng (Hubei) plant commissioned in January 2025. The project comprises two 300 MW non-supplementary combustion CAES units stored in approximately 980,000 cubic metres of salt caverns at depths of 1,150–1,500 metres. Unit 1 reached full-load operation in December 2025; Unit 2 was commissioned in early 2026 to complete the full 600 MW capacity. Core equipment — air turbine units, generators, electric motors, and molten salt storage tanks — was supplied by Shanghai Electric and Harbin Electric Corporation. Total project investment was approximately $520 million. Annual electricity generation is expected to reach approximately 792 GWh, sufficient to power approximately 600,000 households, with annual CO₂ emissions reductions of approximately 600,000 tonnes.

How It Works & Differentiation

The Huai'an system uses a proprietary 'molten salt + pressurised thermal water' high-temperature adiabatic compression process: during charging, surplus grid electricity drives compressor trains that pressurise ambient air; the heat of compression is captured and stored in molten salt thermal storage tanks rather than being vented to atmosphere. During discharge, the stored thermal energy reheats the expanding compressed air before it passes through turbine generators, eliminating natural gas combustion. System conversion efficiency is approximately 71% — materially higher than conventional CAES systems. The salt cavern storage volume of approximately 980,000 cubic metres provides the pressure reservoir at depths where rock stress maintains cavern integrity.

Commercialization & Traction

The Huai'an project is already providing commercial grid services — peak shaving, frequency regulation, and load balancing — to the Jiangsu grid, which has among the highest renewable penetration rates in China. The project is one of over 50 CAES facilities currently under construction or development across China, and its commissioning at 600 MW / 71% efficiency sets a new commercial benchmark for the technology. A 700 MW / 4,200 MWh project is already in development in Sanmenxia's Shanzhou district, indicating that Chinese developers are targeting continued scale-up. The domestically manufactured equipment platform and proven salt cavern geology are being applied across multiple provincial markets simultaneously.

Scalability & Strategic Context

The Huai'an project demonstrates the pathway from the Yingcheng 300 MW platform to 600 MW in a single step, confirming that the Chinese CAES technology stack scales linearly with cavern volume and turbine capacity. The 71% efficiency figure is the highest published for any large-scale CAES project globally, and the non-combustion adiabatic process makes the output genuinely zero-carbon. China's CAES pipeline now represents the world's fastest-scaling long-duration storage deployment programme by installed capacity. The next development step — the 700 MW Sanmenxia project — would represent another 17% capacity increase over Huai'an, suggesting Chinese developers have a clear multi-year roadmap for continued record-setting.