Moonwatt raises €8 million to transform solar power with novel sodium-ion batteries

Amsterdam-based Moonwatt, an energy storage startup, has raised €8 million to innovate solar power with its sodium-ion battery system.

The funding round was co-led by daphni and LEA Partners, Founders Future, AFI Ventures (by Ventech) and Kima Ventures also participated alongside strategic business angels and customers.

The funding will be used to accelerate the development and deployment of Moonwatt’s hardware and software technology, expand the team and drive the shift toward a cleaner, more resilient global energy ecosystem.

Zukui Hu, CEO and Co-founder of Moonwatt, said: “We started our product design from a blank sheet of paper, freeing ourselves from legacy features inherited from other segments of the battery industry, with the goal of designing a system from scratch that is fundamentally cheaper, safer and more reliable. Our vision is a product that can be deployed anywhere, and that can be scaled up multiple orders of magnitude without facing raw materials scarcity.”

After more than a decade in energy innovation, Co-founders CEO Zukui Hu, CTO Guillaume Mancini, and CCO Valentin Rota launched Moonwatt in 2024 on the belief that clean energy only succeeds if the systems that power it are scalable, sustainable and competitive. In line with this, Moonwatt is developing the “world’s first” energy storage solution specifically for solar power.

The founders all met during their time at Tesla Energy, with a diverse se of skills and experiences in the storage, solar, wind and power sectors, they have developed a deep renewable power expertise.

According to comments by Moonwatt, solar has scaled faster than any energy source in history, with capacity set to increase tenfold by 2030. But despite being affordable and abundant, it isn’t dispatchable 24/7. Power floods the grid during daylight hours when demand (and prices) are low, but when the sun sets, the infrastructure isn’t in place to keep it flowing.

This intermittency causes congestion and price cannibalisation; over 3,000 GW of renewable projects are currently stuck in grid backlogs while wholesale prices regularly plunge below zero due to the excess, forcing plant owners to shut down production or sell at a loss.

Paul Bazin, Partner at daphni, said: “Renewable power growth has exceeded all expectations, but we’re approaching a tipping point where it won’t be able to scale further without better energy storage. Created by industry veterans, Moonwatt is solving this with a differentiated storage product built specifically for solar – this is the breakthrough the industry has been missing.”

Moonwatt believes storage holds the key but remains the sector’s biggest bottleneck. Today’s lithium-based batteries haven’t been specifically built for solar or optimised for very large-scale storage – they rely on scarce, costly materials, and are built on adapted legacy tech designed for EVs.

According to Moonwatt, the only way to solve this is to make solar storage more competitive, which relies on finding a sustainable, scalable, and cost-effective alternative. It’s a challenge that has created a €379+ billion market opportunity, and it’s an opportunity Moonwatt is uniquely positioned to lead.

Moritz Pagel, Investor at LEA Partners, said: “By focusing on sodium-ion, Moonwatt represents a paradigm shift, finally making 24/7 renewable power truly competitive and unlocking massive value for operators and consumers. We’ve been amazed by the complementary skillset and execution power of the team and are excited to back Moonwatt.”

Instead of retrofitting legacy technology or settling for a one-size-fits-all approach, Moonwatt’s battery energy storage system is built from the ground up to not only meet solar’s specific intermittency, price and congestion challenges but to work anywhere in the world from day one.

Moonwatt’s energy storage systems ditches lithium-ion for sodium-ion – a 1000x more abundant, a third cheaper and safer alternative which is better suited to building scalable, sustainable, and cost-competitive stationary storage.

When deployed, the systems will co-locate storage with solar plants to increase their capacity factor from 15-20% to up to 80% to reduce the need for costly grid upgrades, all while cutting congestion, stabilising prices and making round-the-clock clean energy a reality. This is part of Moonwatt’s mission to build a truly-optimised solar system to unlock solar’s potential and make it the dominant power source worldwide.

At full potential, this approach has the potential to help the industry abate up to 14 GtCO2 per year by 2050.

Marc Menasé, Founding Partner at Founders Future, said: “At the heart of every game-changing innovation is an exceptional team. Moonwatt combines world-class expertise with relentless execution to tackle one of the biggest challenges in renewable energy: scalable and cost-efficient storage. Their visionary approach and breakthrough technology have the potential to transform how we store and distribute clean energy, and we’re proud to support them on this journey.”