How RTE is using Li-ion energy storage to build grid flexibility

• French transmission grid operator RTE has adopted a Saft lithium-ion (Li-ion) energy storage system (ESS) in the ground-breaking RINGO project. The trial project is using energy storage to boost the grid’s flexibility to prepare for growing deployment of renewable energy in France’s electricity mix.

OVERVIEW

Greater flexibility will enable RTE to adapt to the changing power landscape, optimize its assets and maximize use of renewable energy. Because wind and solar farms are often located at the edge of the grid, energy can be lost when transmission lines do not have enough capacity to carry their full output.

Rather than upgrading the grid, RTE is using the RINGO project to explore the innovative approach of using digitally controlled energy storage to absorb and release energy simultaneously at different sites located up and downstream of grid bottlenecks. This way, renewable energy can be managed by RTE’s pilot system and thereby delivered, overcoming locations of limited peak transmission capacity. This will not interfere with competitive energy trading markets, providing flexibility without breaching RTE’s regulatory requirements.

Ringo project goals :

• Reduce intermittent congestion and provide flexibility on grid transmission lines
• Maximize usage of renewable energies – reduce curtailment of wind and solar generation
• Defer investment in grid infrastructure upgrades
• Evaluate three technology approaches
• Support the development of France’s energy storage industry

THE CHALLENGE

The RINGO project calls for deep charge and discharge cycles of up to 70 percent of the energy storage capacity. This is challenging as batteries age more quickly when used for deep cycling.

An additional requirement after the first three years is for the batteries to provide grid services such as frequency regulation. This requires shallow and frequent cycling as well as the ability to respond within milliseconds. Therefore, the ESS needs to be flexible to adapt to changing charge and discharge patterns and potentially stack multiple different services at once.

THE SOLUTION

Saft and its consortium partner Schneider Electric are delivering a turnkey system with 12 of Saft’s Intensium® Max 20 High Energy 1500V containers, six inverters and four high-voltage transformers. Each container provides 2.5 MWh energy storage and 1.2 MW power with control, thermal management, and safety systems in a standard 20-foot shipping container. These are designed as building blocks to create large-scale installations up to 100 MW and provide best-in-class performance across energy density, energy efficiency, lifetime and performance. They are manufactured at Saft’s plant in Bordeaux, France. 

To size the ESS, Saft carried out extensive modelling of different operational scenarios. Special attention was given to the system’s energy efficiency, considering AC/DC conversion efficiency, thermal behaviour, cooling and heating efficiency and auxiliary energy consumption. In addition, Saft provided an exhaustive environment and life cycle assessment study, enabling RTE to evaluate the global environmental performance of the RINGO project.

Flexibility is also supported by the modular nature of the ESS as RTE could move some or all the ESS containers to other locations if needed.

Features :

• 30.8 MWh energy storage capacity
• Delivers 10 MW over two hours, with peak power rating of 20 MW
• Containerized, factory tested DC and AC building blocks for plug-and-play installation on-site
• Seamless communication between Saft and Schneider systems
• Known carbon footprint thanks to Life Cycle Analysis

Key benefits :

• Avoid curtailment and re-dispatching of wind and solar generation
• Optimize utilization of existing grid assets under changing generation conditions
• Defer investments in the grid
• Develop knowledge on how to best use battery energy storage for grid flexibility
• Experiment and evaluate multiple storage services