Alfen plans a large sodium-ion battery energy storage system (BESS) demonstrator for the second half of 2027 to test technical operation, grid integration and its software, CEO Michael Colijn said in an interview published November 5, 2026.
The demonstration would put the system’s components and controls through integration checks. At the time of the interview, tests of inverter behavior with the sodium-ion chemistry and software settings for different response times were still ahead.
The 5 GWh plan covers a deployment across Europe
On July 16, 2026, Alfen announced a collaboration with CATL to deploy 5 GWh of CATL sodium-ion BESS across Europe. That figure is the planned scale of the deployment. Alfen said its long-term battery-supply partnership with CATL began in 2023 and expanded in 2024. Alfen’s announcement
The demonstrator is meant to test system integration
A BESS combines batteries with equipment and controls that connect stored energy to the grid. Colijn said Alfen intended the demonstrator to test the system’s technical operation, its grid integration and whether Alfen’s software works with it.
Colijn expected Alfen to reuse the transformer, inverter and software stack from its existing lithium iron phosphate (LFP) solution, making adjustments if needed. That was his expectation; the inverter and software checks he described had not yet been completed at interview time.
The planned demonstration’s key test is whether the battery, inverter and control software work together as a grid-connected system.
Sodium-ion brings a footprint trade-off
Colijn said sodium-ion solutions then cost more and had lower energy density than lithium-ion solutions. He estimated that the sodium-ion system would need roughly 20% more footprint for the same energy capacity and power output. That estimate makes physical space one of the practical factors Alfen’s system design must account for as it works toward the demonstrator.
