Why high energy is the future of storage

Hervé Amossé, Executive Vice-President at Saft’s Energy Storage & Mobility division explains the growing role for high energy lithium-ion (Li-ion) batteries to integrate renewable energy in applications that need discharge times of more than two hours.

Energy storage has a vital role to play in the energy transition. As we shift from coal-fired power stations to wind and solar farms, utility-scale batteries will smooth out the natural variability of the wind and sun. In addition, battery energy storage can enhance the flexibility of the grid, reduce infrastructure investment and optimise power flows.

The first generation of energy storage systems provided high power over a short duration, typically of minutes to hours. Many of these were deployed on remote and island communities to support the integration of renewables and reduce the reliance on costly imported diesel.

However, mass adoption of the technology requires an energy storage system (ESS) that can provide consistent power over longer duration. This will enable other applications, such as frequency response, where energy is absorbed and injected to maintain grid stability by delivering power consistently over two to four hours.

This is important for integrating renewable energy, balancing the grid, providing stability and resiliency for microgrids and maximising self consumption and optimising the energy efficiency of commercial and industrial facilities.

Finnish wind farm

One operator that has adopted high energy ESS units is TuuliWatti, the Finnish wind energy developer. It has invested in three Saft Intensium Max 20 High Energy (HE) containers to support frequency regulation at its new 21 megawatt (MW) wind farm in northwestern Finland.

The lithium-ion (Li-ion) ESS is the largest in the Nordic countries and provides a total energy storage capacity of 6.6 megawatt-hours (MWh) and deliver up to 5.6 MW of power.

Saft introduced the high-energy containers in May 2019 to build on the success of its Intensium Max 20 Power containers. The high energy version more than doubled the capacity of its previous generation of units, which has been deployed around the world with a combined total capacity of more than 100 MW.

Energy storage applications

Our objective was to create a package to provide renewable energy developers with a large-scale energy storage container designed to sustain multiple daily cycles with typical discharge times of two to four hours.

While one application can be frequency regulation, the ESS has got potential to provide peak shaving, where energy is stored during times of congestion on the grid before being released when peak demand passes, or time shifting, when the output of a wind or solar farm is stored at times of peak generation and saved until peak demand.  

It can also be deployed in virtual power lines and ‘behind the meter’ applications for industrial sites and commercial premises.

Success factors

What operators need is energy storage that provides high levels of safety, reliability and ease of maintenance, as well as straightforward installation and delivery. These are essential factors in ensuring continuity of service and safety.

However, from a performance perspective, energy density, energy efficiency and long lifetime are also essential. These are critical to return on investment.

Energy density denotes how much energy storage capacity can be packed into a container – and therefore controls the duration of a discharge cycle from the battery and also maximises the energy storage that can be integrated into the standard 20 foot shipping container.

Energy efficiency and long lifetime are also important for optimising costs over the long term. Having high efficiency allows other grid resources to operate optimally.

Best in class performance

For the Intensium Max 20 HE, Saft has provided a ‘best in class’ across these, with 1.2 MW power and 2.5 MWh energy storage in each container. The containers also power management and power conversion technology, as well as control, communication, thermal and safety management functions and can be used as building blocks to create large-scale installations of up to 100 MW.

This scalability is vital for customers, who want a scalable and modular approach to closely match their requirements from a few kilowatts to hundreds of megawatts.

Safety and capacity are both enhanced with an unmanned approach, where operators can access energy storage modules from the exterior walls of the unit with no need to enter the container through a central corridor. Inside, the modules are larger with advanced design to enable high energy storage capacity.

Taking responsibility for every aspect

Saft fully fits out and tests its containers at its factory sites in North America, Europe and the Far East. The units are then delivered to site ready to ‘plug and play’ to ensure simple installation on a concrete pad and straightforward commissioning.

This combination was important for TuuliWatti in Finland. Its Portfolio Manager for Power said: “TuuliWatti’s goal is to be the leading wind power developer and producer in the Arctic region. Saft’s high-energy containers will help us achieve this at Viinamäki by improving the competitiveness of wind power. They provide a fast response in challenging environmental conditions, as well as the energy storage capacity to support grid stability, allowing us to adjust the output of our wind farm immediately.”

Because we take responsibility for every aspect of design, manufacture and integration, it provides buyers with long-term warranties. This is particularly important when operators want confidence that their ESS will work reliably from day one until the day it retires from service.

Successful energy storage requires technical knowhow to formulate electrochemistry, size the project to and integrate power conversion, and power management systems.

During installation and commissioning, customers also require support with architecture and civil engineering design, installation, establishing a grid connection and successful commissioning, training and handover to local operators.

Finally, once in operation, operators often require support with further training, remote electronic supervision and data management, as well as delivery of maintenance services.