Amsterdam-based startup Moonwatt has recently raised €8 million to develop energy storage systems (ESS) using sodium-ion technology.
The rapid growth of renewable energy over the past decade has increased the need for higher‑performance storage solutions. Although lithium-ion (Li-ion) technology still dominates the market, sodium-ion is emerging as a promising alternative, especially for projects where cost is critical. Founded in September 2024, Moonwatt aims to make clean energy competitive and available around the clock by compensating for the intermittent output of renewable sources. Its founders – Zukui Hu (CEO), Guillaume Mancini (CTO) and Valentin Rota (Sales Director) – previously worked together at Tesla Energy.
Why choose sodium?
Whether semi‑solid or solid‑state, sodium-ion batteries are gaining ground over lithium‑ion thanks to their improved safety, energy density and production cost advantages.
“Each technology has its strengths and weaknesses. For example, lithium iron phosphate (LFP) has overtaken nickel manganese cobalt (NMC) in stationary storage because it is cheaper and more durable,” explains Valentin Rota.
Despite their lower energy density (140–160 Wh/kg), sodium‑ion batteries are perfectly suited to ESS where space is not a major constraint. Their safety profile, comparable to or even better than LFP, reduces the risk of fire. Their service life – 1 to 1.3 cycles per day over 20 years – matches the needs of solar power plants very well.
The strategic alliance between solar and storage
Global solar capacity is expected to increase tenfold by 2030. Combining solar with storage has become essential to prevent grid overload and maximise the profitability of installations. Moonwatt designs decentralised low‑voltage DC ESS that are directly integrated into solar PV farms, reducing infrastructure costs and improving energy efficiency.
Unlike standardised containers, their modular architecture can be scaled to projects ranging from a few hundred kW to several GW. “We are targeting independent power producers and grid operators in Europe and worldwide, focusing on new installations and the upgrade of existing sites,” Rota says.
Challenges and outlook for sodium‑ion
While sodium is abundant and inexpensive, the ongoing decline in lithium prices remains a hurdle. “The sodium‑ion supply chain is still young, but as it matures it will help stabilise costs over the next few years. Some chemistries such as NFPP (polyanions) are particularly well suited to stationary storage,” adds Rota.
According to Yole Intelligence, the market will reach 40 GWh by 2029, but Moonwatt is expecting faster adoption. Currently in the prototyping phase, the startup is planning pilot projects within a year and is aiming for commercial production (>1 GWh/year) by 2027.
Ambitions and development
Moonwatt currently has seven employees and is actively recruiting to strengthen its technical team. Although no European research project has yet been launched, the company hopes to work with the local ecosystem to accelerate its growth and innovation.
