Harnessing the ocean: Pioneering offshore electricity storage

TNO's OESTER project is charting new territories by targeting offshore electricity storage, a key solution to energy grid congestion and instability. As renewable energies like wind power flourish, the oversupply threatens to devalue energy investments, prompting innovative storage strategies. This project evaluates various technologies - from quick-fix battery use in wind turbine bases to long-term electrolyzer systems on offshore platforms.

Endorsed by the Netherlands Enterprise Agency and part of the Mission-driven Research agenda, OESTER leverages digital twins to refine storage strategies at a gigawatt scale. The ultimate aim is to establish next-generation energy farms capable of providing reliable baseload power, actively integrating renewable resources. With a horizon extending towards 2050 when renewable energy sources will dominate, this project stands as a beacon for future-ready energy systems.

Mismatch between production and demand

The integration of renewable energy sources with offshore storage presents unprecedented opportunities. The OESTER project aims to develop comprehensive storage solutions that could transform how we manage renewable energy. Key technologies under evaluation include short-term battery storage within wind turbine foundations, medium-term solutions like Compressed Air Energy Storage and Underground Pumped Hydro Storage, and long-term electrolyzer systems on offshore platforms. This multi-tiered approach addresses one of the most pressing challenges in renewable energy: the mismatch between production and demand. The global energy storage market is projected to grow at an impressive 21% CAGR by 2030, with annual additions expected to reach 137 GW.

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Storage technologies

A groundbreaking development in offshore storage comes from the Grid-Forming Undersea Pumped Storage System (GFM-UPSS), which demonstrates promising results for achieving 100% renewable offshore power systems. The system employs advanced control strategies using grid-side converters, machine-side converters, and reversible pump turbines to regulate frequency and voltage. Meanwhile, emerging technologies like seawater zinc batteries offer a sustainable alternative for offshore stationary energy storage. These batteries leverage natural seawater, which comprises approximately 96.5% of Earth's total water reserves, providing an abundant and cost-effective electrolyte source.

Combining different renewable sources within offshore energy parks presents compelling opportunities for efficiency gains. Studies show that adding solar capacity equal to installed wind power can increase annual exported production by more than 30% without export constraints. When export capacity equals installed wind capacity, production still increases by nearly 23%. This integration aligns with the ambitious targets set by the Energy Storage and Grids Pledge of COP29, which aims to improve global energy storage capacity to 1,500 GW by 2030. Such expansion requires significant infrastructure investment, including adding or refurbishing over 80 million kilometers of grid infrastructure by 2040.

Future-Proofing Energy Systems

The development of these storage solutions comes at a crucial time. China targets at least 40 GW of battery storage installed by the end of 2025, while the United States continues to expand its large-scale battery storage projects. The OESTER project's use of digital twins for simulating hybrid storage systems at a gigawatt scale represents a significant step toward optimizing these technologies. Breakthroughs in seawater battery technology show promising results, with charge gradient interface modifications enabling zinc electrodes to cycle beyond 1,300 hours - forty times longer than unprotected electrodes. These developments suggest a future where offshore renewable energy systems can provide reliable baseload power while maintaining grid stability.