Norway's Solar Vault Could Heat Europe's Winters

Photoncycle raises €15M to store surplus summer solar as solid-state hydrogen, releasing it as heat and power through winter

15 Apr 2026

A Norwegian energy storage company has raised €15 million in Series A funding to bring a solid-state hydrogen system to residential markets in Denmark and the Netherlands, targeting a gap in Europe's clean energy infrastructure that conventional batteries cannot fill.

Photoncycle's technology converts surplus solar electricity into hydrogen, which is stored in a solid state inside a patented underground tank capable of holding up to 10 megawatt-hours of energy. In winter, a reversible fuel cell converts the stored hydrogen back into heat and electricity. Standard home batteries are designed for overnight use; this system holds energy across entire seasons.

The round was led by NordicNinja and Voima Ventures. Denmark is the initial target market, where around 300,000 homes rely on gas heating scheduled to be phased out by 2035, and where household energy costs rank among the highest in Europe. The Netherlands follows, where the removal of net metering in 2027 will alter the financial case for rooftop solar for millions of homeowners.

The company will offer its system on a subscription basis, covering hardware, installation, maintenance, and access to energy markets. It plans to scale manufacturing to 1.4 terawatt-hours of annual capacity by 2027, sufficient for approximately 140,000 homes.

Voima Ventures said seasonal storage had become a structural requirement as renewable capacity grows and electricity markets become more exposed to seasonal swings in supply and demand. NordicNinja cited energy sovereignty across Europe and Asia as the broader rationale underpinning its investment.

Europe spent roughly €396 billion on fossil fuel imports in 2025, a large share driven by winter heating. Distributed solid-state storage, if it scales, would reduce that dependence at the household level rather than through centralised infrastructure.

Whether residential uptake in two relatively small markets can support the manufacturing ambitions the company has set out remains to be seen.