Photoncycle – Norwegian energy storage scale up Photoncycle has raised €15 M in Series A funding as it seeks to tackle one of Europe’s most persistent renewable energy challenges: enabling households to store surplus summer solar power for winter heating and electricity.
Image Credit: Photoncycle
The round was led by NordicNinja and Voima Ventures, Nordic's leading deep-tech and energy transition investors, with participation from existing investors Lifeline Ventures, Eviny Ventures, Luminar Ventures, and Momentum. The funds will support commercial rollout in Denmark and the Netherlands and finance the first phase of an industrialization plan that includes a proposed 1.4 terawatt-hour annual manufacturing facility.
The investment comes as Europe continues to grapple with the structural vulnerabilities exposed by the 2022 energy crisis. The EU imported €396 bn of fossil fuels in 2025, around €880 per citizen, underscoring the bloc’s continued dependence on external supply even as renewable generation expands. Winter exposure remains particularly acute: space heating accounts for 62.5 percent of household energy use, while natural gas remains a significant component of residential consumption, leaving households sensitive to seasonal price swings in global gas markets.
At full industrial scale, Photoncycle’s proposed 1.4 TWh manufacturing facility would represent storage capacity equivalent to roughly 140,000 homes each storing 10,000 kWh of seasonal energy. Photoncycle’s distributed, household-level seasonal storage is designed to reduce the volume of imported gas required to meet winter heating demand, and consequently reduce Europe’s reliance on importing fossil fuels in winter.
Subscription to Lower Upfront Installation Costs
The company intends to offer the system under a subscription-based model covering solar panels, storage, servicing and access to energy trading markets, with the aim of lowering upfront costs for homeowners. By storing summer solar power for winter use, the model aims to provide households with more predictable year-round energy costs and lower exposure to volatile gas markets. Photoncycle has already seen strong early interest from households seeking alternatives to gas-based heating. In Denmark, for instance, where Photoncycle has a rapidly growing waiting list, energy prices are among the highest in Europe and 300,000 homes still depend on gas-based heating systems that are set to be phased out by 2035.
Bjørn Brandtzæg, founder and chief executive of Photoncycle, said the company was focused on moving seasonal energy resilience closer to consumers. “Europe is beginning to solve short-duration storage,” he said. “The remaining gap is seasonal. If households can store summer energy for winter use, they reduce exposure to imported fuel and price volatility as well as to increasing grid costs for consumers.”
Tomosaku Sohara, General partner at NordicNinja, said: “From our perspective of bridging Japanese capital and European startup expertise, we strongly believe energy sovereignty must be strengthened across both Europe and Asia. Photoncycle combines deep technical innovation with a clear, scalable path to global deployment. Long-duration energy storage is critical to building resilient, reliable clean energy systems in Europe, Japan and beyond. We’re excited to help introduce the team to global opportunities, building on our long experience in the energy sector.”
Inka Mero, Founder and Managing Partner at Voima Ventures, said: “As the share of renewable energy increases, structural price volatility in electricity markets is rising. Seasonal storage is therefore not a niche solution, but a systemic necessity. Photoncycle addresses this imbalance by enabling households to store energy across seasons and reduce their dependence on imported fossil fuels. This is an important building block for a resilient and sovereign European energy system.”
The Series A funding will now be used to scale manufacturing and early commercial deployment in Denmark initially, followed by Europe’s other large markets including the Netherlands. Beyond Europe, there are opportunities to scale Photoncycle’s breakthrough technology in Asia, including Japan, and in the US.