Energy Storage No. 1

Executive Overview

Energy Storage No. 1 (CAES No.1) is a 300 MW / 1,500 MWh advanced compressed air energy storage (CAES) power station in Yingcheng City, Hubei Province, China, developed by China Energy Engineering Group (CEEC). The facility achieved full-capacity grid connection on January 9, 2025, and was at the time the world's largest CAES project in commercial operation. Storage medium is two abandoned underground salt mine caverns at depths of up to 600 metres, with a combined gas storage volume of approximately 700,000 cubic metres. The project was built in approximately two years at a total investment of approximately 1.95 billion yuan (approximately $270 million). In January 2026, a 600 MW / 2,400 MWh CAES plant in Jiangsu Province superseded it as the world's largest.

How It Works & Differentiation

The system stores electricity by running surplus power through a compressor train that pressurises air into the salt caverns during low-demand or high-generation periods (up to 8 hours of charge). During discharge, the compressed air is released, heated using thermal energy recovered from compression, and expanded through a turbine set to generate electricity — 5 hours of discharge per cycle at 300 MW. System conversion efficiency is approximately 70%, without combustion or fossil fuel input. Salt cavern geology provides inherent sealing and pressure stability that porous rock storage cannot match, and the Yingcheng site uses abandoned cavities from legacy salt extraction, reducing development cost and environmental footprint. All core CAES equipment was domestically sourced, achieving 100% localisation. The project set three simultaneous world records at commissioning: single-unit power output, energy storage scale, and conversion efficiency.

Commercialization & Traction

CEEC's successful build-out of the Yingcheng project has positioned it as the reference design for China's rapidly expanding CAES pipeline. Over 50 CAES projects are currently under construction across China, targeting provinces including Hunan, Henan, Jiangsu, Jiangxi, Yunnan, Shaanxi, and Shandong, with cumulative planned capacity exceeding 1,950 MW. CEEC signed a memorandum of understanding with Kazakhstan's Ministry of Energy following the Yingcheng commissioning, demonstrating early international commercial interest. The project's approximately two-year construction timeline and domestic equipment base give it a cost and delivery speed advantage that is attracting government and utility procurement well beyond Hubei Province.

Scalability & Strategic Context

Yingcheng establishes the salt cavern CAES technology platform for China's grid-scale storage buildout, which operates alongside lithium-ion and pumped hydro in the country's storage strategy. China is conducting R&D for 600 MW to 1,000 MW CAES units targeting 72–75% conversion efficiency, building on the Yingcheng platform. The January 2026 commissioning of the 600 MW / 2,400 MWh Jiangsu CAES plant — which replaced Yingcheng as the world's largest — confirms that the technology is scaling rapidly across multiple provincial markets simultaneously. With suitable salt cavern geology covering major portions of central and eastern China, CAES is positioned alongside pumped hydro as the primary long-duration storage technology in China's national grid expansion plan.