Bolster Investment Partners has acquired a majority stake in Eternal Sun
May 2025 — Bolster Investment Partners, a Netherlands-based investment firm, has acquired a majority stake in Eternal Sun, a global technology leader in advanced solar panel testing equipment, from ABN AMRO Sustainable Impact Fund, a private impact fund based in the Netherlands, and Vermec, a Belgium-based investment firm.
This partnership marks the next phase of growth for Eternal Sun. With its long-term support and growth expertise, Bolster is the ideal partner to help Eternal Sun drive its buy-and-build strategy, accelerate international expansion and support the continued professionalization of the organization.
Founded in 2011 by Stefan Roest, Eternal Sun develops, manufactures and installs advanced testing equipment for solar panels. With a focus on innovative flash and steady-state simulators, the company helps customers around the world assess the performance and reliability of solar panels. Leveraging deep technical expertise and innovative strength, Eternal Sun has established itself as the global market leader in steady-state simulators, essential tools for accurate, long-term testing of solar panels. The company serves leading solar panel manufacturers and independent laboratories across 60 countries, operating from six locations in four countries. Its high-precision testing equipment plays a vital role in quality control, pricing and R&D. In addition, Eternal Sun provides import testing and factory inspection services to major importers and developers of solar energy projects. Following earlier strategic acquisitions, such as Spire Solar in the USA and SunChine in China, the company is well positioned to benefit from continued market growth and technological advancements.
Bolster Investment Partners is a long-term investment firm focused on partnering with founder-led and family-owned businesses through both minority and majority stakes. The firm’s long-term approach and experience align well with sustainable and technology-driven businesses such as Eternal Sun.
Our role in the transaction
Oaklins’ team in the Netherlands acted as the exclusive sell-side advisor to the shareholders of Eternal Sun on this transaction. The team in Germany provided support in the early stages of the transaction. The deal highlights Oaklins’ extensive expertise in the energy and sustainability sector, advising both management and private equity investors on value maximization strategies for industry-leading businesses.
Stefan Roest
Founder and CTO, Eternal Sun
Talk to the deal team
Bente Rasenberg
Oaklins Netherlands
Rainier Smeink
Oaklins Netherlands
Related deals
Mattina Holding has sold a 5% stake in Gens Aurea via accelerated bookbuild
Mattina Holding S.A. (DVC Partners) has sold a 5% stake in Italian company Gens Aurea S.p.A. through an accelerated bookbuild, raising approximately US$69.96 million.
Learn moreENGIE Énergie Services has sold Majorelle to Isospace
Majorelle, a pioneer in space planning in France for 40 years, has been sold to Isospace by ENGIE Énergie Services. The transaction marks a new chapter in Majorelle’s growth, bringing together complementary expertise in workplace design, space planning and fit-out while preserving its brand, teams and market positioning. Together, Majorelle and Isospace generate more than US$45 million in revenue, primarily in the Île-de-France region. The companies operate in a commercial fit-out market undergoing significant transformation, driven by evolving workplace needs, real estate asset repositioning, regulatory requirements and environmental and socioeconomic challenges. Philippe Savajols, president of Isospace and Majorelle, aims to ensure continuity for Majorelle and its teams while developing complementary capabilities and synergies across the group, preserving both companies’ respective cultures, expertise and client relationships.
Learn moreCibus has acquired Aweta from Standard Investment
Standard Investment has reached an agreement with Cibus Capital, advisor to the Cibus funds, on the sale of Aweta, a global leader in fruit and vegetable sorting, grading and packing equipment. Completion of the transaction is expected in the coming weeks. The transaction provides Aweta with a strong partner to support the company’s next growth phase. Under Cibus’ ownership, Aweta will pursue further international growth and accelerate investment in R&D, supporting the installed base and product innovation, including software and AI capabilities. Aweta’s leadership team will continue to lead the business.
Learn more