The drive to decarbonize our economies through electrification and clean energy continues to gain momentum, with battery technologies playing a crucial role in enabling the green transition. Moonwatt, a clean tech startup founded in the Netherlands, is working on a battery-based energy storage system specifically designed for solar power plants to help regulate the variability of solar energy output.

The startup's system is co-located with solar power plants and optimized to store energy during daylight hours, allowing the stored power to be made available during periods of higher demand. This approach enables solar plants to increase their revenue by selling more solar energy, including during periods when the price of energy is more attractive, and decrease costs at the plant level by mutualizing some of the electrical infrastructure.

Moonwatt's system is built around sodium-ion cells, which offer a cost-effective alternative to lithium-ion batteries. The technology relies on cheaper and more readily available raw materials, making it an attractive option for stationary installations like solar power plants. Although sodium-ion batteries have size and weight challenges, they are gaining traction as a lower-cost storage option for renewables.

The startup claims that its energy storage system can increase the capacity factor of solar power plants up to 80%, allowing them to double their internal rate of return (IRR). According to co-founder and chief commercial officer Valentin Rota, "what we allow our partner to do is to double their return... an average PV asset is around 8% to 12% return, and we will bring the asset up to around 20%."

Moonwatt's founding team, which includes CEO Zukui Hu and CTO Guillaume Mancini, met while working on battery tech for Tesla almost a decade ago. They have continued to work together on various projects, including small-scale, off-grid solar storage. The founders saw an opportunity to combine their knowledge of battery hardware and apply it to power up solar storage gains, realizing that there was no dedicated product for solar storage yet.

Moonwatt's approach is centered around using sodium-ion battery technology, which offers better scalability, cost reduction, and carbon footprint reduction than lithium-ion. The design of their storage system also uses a distributed architecture, making it easier for plants to integrate. By connecting storage closer to panels at peak output, the approach allows for greater efficiency and a reduction in the cost of dispatchable electricity.

The startup has closed an €8 million seed funding round, co-led by Daphni and LEA Partners, to bring its storage tech to market. The funding will support a pilot installation planned for next year in Europe, with commercial deployments expected in 2027. Moonwatt's ambition is to become a gigawatt-hour player, making a significant impact on the industry.

The focus on solar energy is driven by its attractive economics and broad uptake, with solar being deployed in over 120 countries per year. By optimizing just for solar, Moonwatt can make design choices that help plants get the most out of their asset, including reducing the costs of connecting their energy to the grid.

Looking ahead, the startup's approach is expected to play a crucial role in reducing the overall balance of plant costs and optimizing the use of grid capacity. As the volume of solar energy being produced globally continues to surge, Moonwatt's bet is that the industry will start looking for dedicated storage solutions rather than making do with "cookie cutter" products.

With its innovative approach and focus on solar energy, Moonwatt is poised to make a significant impact on the clean tech industry, helping solar power plants increase their revenue and decrease costs while promoting a more efficient use of grid capacity.