Bolster investment Partners acquires Eternal Sun

Name of the deal:           Bolster Investment Partners acquires Eternal Sun
Date announced:            Announced: May 6th 2025   Closed: July 1st 2025
Date closed:                      Announced: May 6th 2025   Closed: July 1st 2025
Published value:             Between € 5 mln and € 50 mln
Buyer(s):                            Bolster Investment Partners
Target:                                 Eternal Sun and Wavelabs
Seller:                                  ABN AMRO and Vermec N.V. (Belgian family office)

Involved firms and advisors
Involved firms and advisors buy side:
deBreij – Legal Advisory   SINCERIUS – FDD  Bolster Investment Partners – PE Management  JSA TAX – Tax Advisory

Involved firms and advisors target:
Oaklins – M&A Advisory  Huddle Law – Legal Advisory  Amstone Tax Lawyers – Tax Advisory

Involved firms and advisors sell side:
Oaklins – M&A Advisory  Huddle Law – Legal Advisory

Pitch

Deal Outline
In May 2025, Bolster acquired an 80% stake in Eternal Sun, a manufacturer of LED solar simulators for next-generation solar panel technologies. During this process, an unexpected and unique opportunity arose to acquire its German competitor, Wavelabs. Under Bolster’s leadership, Eternal Sun successfully completed the acquisition of Wavelabs on July 1, 2025. Together, they form the global market leader in LED simulators for solar cells and solar panels.

Why This Deal Should Win the Award for Best Deal Small-Cap 2025
About Eternal Sun Group
Founded in 2011 and headquartered in Delft, the Netherlands, Eternal Sun develops and manufactures advanced solar simulators and testing equipment for photovoltaic (PV) modules. The company serves research institutes, certification labs, and solar manufacturers worldwide, helping improve solar panel performance and reliability.

About Bolster Investment Partners
Bolster Investment Partners is a Dutch long-term private equity firm that supports ambitious, mid-sized companies with sustainable growth potential. It typically invests in firms with strong market positions and management teams seeking a long-term partner rather than a short-term exit.

Dear Jury,
Through this letter, we would like to nominate the investment in Eternal Sun by Bolster Investment Partners for the Best Small-Cap Deal 2025.

This deal stands out due to the following characteristics:

• Unique strategic opportunity: Bolster acquired Eternal Sun (a new portfolio company) and, under its leadership, Eternal Sun subsequently acquired its German competitor Wavelabs. Together they created the global market leader in LED solar simulators (panels & cells), reducing customer concentration and strengthening their position in next-gen solar energy
• Two parallel processes: acquisition of Eternal Sun and Wavelabs closed almost simultaneously
• Highly competitive environment: multiple bidders competed for Eternal Sun and Wavelabs
• Unexpected setback overcome: full financing package withdrawn due to sudden import tariffs
• Distressed M&A: rapid and complex acquisition of Wavelabs out of financial difficulties
• Creative approach: from invisible-ink NBO to inventive financing solutions
• Cross-border complexity: navigating legal, financial and cultural challenges across the Netherlands and Germany

In May 2025, Bolster acquired an 80% stake in Eternal Sun, a manufacturer of LED solar simulators for next-generation solar panel technologies, including perovskite. Eternal Sun, based in The Hague and formerly part of the ABN AMRO Sustainable Impact Fund portfolio, is the global market leader in this field and operates in more than 60 countries. During this process, an unexpected and unique opportunity arose to acquire its German competitor, Wavelabs. Wavelabs, headquartered in Leipzig, is the global market leader in LED solar simulators in the adjacent market for solar cells and operates in 40 countries. Eternal Sun successfully acquired Wavelabs on July 1st 2025, under Bolster’s leadership. This transaction was characterized by two simultaneous and intensive competitive processes (Eternal Sun & Wavelabs) running in parallel, while we had to navigate exceptional macroeconomic circumstances.

Acquiring a preferred position  The Eternal Sun process was competitive from the start. This sustainability profile made it a very popular asset, but client concentration in the US made it difficult to assess. We spoke to researchers at universities in Delft and China, solar experts from all over the world and other investors to understand the market better and so we became more educated than our competitors. Eternal Sun is active in the start of the international solar energy supply chain and is thus independent of Dutch demand for solar panels. After a very interesting management meeting where our profiles matched, we were even more enthusiastic, and we knew we needed to do more to acquire a preferred position in the process. Since Eternal Sun makes sunlight, we came up with the idea to submit the NBO on paper with a riddle:    ”Ik reis in het licht dat je dagelijks kent, maar zonder de juiste frequentie, blijf ik voor jou onbekend”

Sunlight consists of different light frequencies. We wrote our NBO with invisible ink, only revealed by UV light, which we delivered too. So a small riddle, a beam of creativity, and a lot of enthusiasm. It was very much appreciated, and helped to obtain the preferred position!

Due to sudden tariffs, financing package was pulled  It was a competitive process until the final stage, as the Sellers were unwilling to grant exclusivity due to uncertain market conditions. After tough negotiations with Sellers, Bolster managed to secure the Eternal Sun deal by acting faster and more convincingly than the competition. However, on the very day a renowned Dutch bank was scheduled to approve our acquisition financing, Donald Trump unexpectedly announced the immediate introduction of a 125% import tariff on all Chinese goods (where 80% of the world’s solar panels are produced) and a 20% tariff on European goods. As the United States is a key market for Eternal Sun, the bank informed us that under these ‘unprecedented’ circumstances it would not merely reduce the financing, but instead withdraw entirely from providing any form of financing. Other banks were also surprised by the tariffs and not happy to jump in. In addition, we needed to complete the Eternal Sun closing as quickly as possible to enable the Wavelabs transaction. We started brainstorming with Sellers and negotiated for a solution again. The solution became a complex convertible vendor loan which had to be refinanced as soon as possible. The good news: We became the shareholder next to management!

Extra complexity from a buy-and-build opportunity with insolvency problems  During the transaction process of Eternal Sun, Bolster and the management of Eternal Sun were intensively engaged in the acquisition of Wavelabs, while Bolster was not a shareholder yet. But we wanted to invest time and effort. Wavelabs had fallen into significant financial difficulties due to mismanagement, yet unexpectedly became the subject of a highly competitive sales process with five other bidders from Europe, China, and the United States. As the market was aware of Wavelabs’ financial situation, it became a race against time to acquire the company (through an asset deal) as quickly as possible to ensure the continuity of its operations. However, the restructuring of Wavelabs has to already start before the transaction. For Bolster and Eternal Sun, the acquisition of Wavelabs was of great strategic importance, not only from a defensive perspective, but it also provided access to Wavelabs’ highly reputable customer base and one of the strongest R&D teams in the field of solar simulators. It was a once-in-a-lifetime-opportunity to move to the adjacent market of solar cells (next to panels) and dilute client concentration. While the Bolster team was driving to and from Leipzig to negotiate with Wavelabs, the car functioned as a mobile office, maintaining a constant connection with Oaklins for the final negotiations regarding the investment in Eternal Sun.

Concluding the deals  On 6 may 2025 we managed to close the Eternal Sun deal and within a month we were on our way to Germany to sign the Wavelabs deal at the notary. This was not a given at all. The night before the signing of Wavelabs we had negotiated until 3 am and made the call to jump into the car a few hours later and drive to Germany, while the final negotiations needed to be done from the car and in the end in the office of the notary. After spending all day at the notary, the notary finished reading the transaction documentation at 11pm and we ended up singing. The next day, the restructuring and improvement of Wavelabs had to begin.

Luckily, as the tariffs normalized, we managed to refinance the convertible vendor loan by a Dutch bank, and Eternal Sun and Wavelabs have already made strong progress (above investment case performance already). The solar energy market has responded enthusiastically to Eternal Sun’s acquisition of Wavelabs, and synergies are already delivering results. The outlook is promising. We would be happy to elaborate further on this remarkable deal in a pitch.

Kind regards,
Mark van Rijn, Martijn Fakkert and Willem de Rooij  | The Etenal Sun and Wavelabs dealteam.

*We have emailed Elisa and Laura from the M&A Awards organisation a PDF-file in which we further outline our enthusiasm for this deal, including an image from our NBO. Only the text is provided below.

Impact of This Deal on the Company
For Eternal Sun, the impact of Bolster’s investment is significant. Thanks to the support and capital provided by Bolster, they were able to complete the acquisition of Wavelabs. This has given them a 50% increase in sales, access to a portfolio of renowned customers, one of the world’s leading R&D teams, and a significant reduction in customer dependency. In addition, they are entering a large new market with substantial cross-selling opportunities and strong synergies.

For Wavelabs, the acquisition is even more important. Competing bidders in the process included an American and a Chinese party. Their sole interest was to acquire the technology and relocating operations to China or the United States without retaining the current employees. The entry of Eternal Sun and Bolster has instead brought stability and created opportunities for the company that otherwise would not have existed. This also prevented valuable knowledge and technology from leaving Europe for China or the United States and falling into the hand of competitors.

Impact of This Deal on Direct Stakeholders
This deal means long-term stability and signigicant growth opportunities for Eternal Sun and Wavelabs. The combination offers customers, for the first time, an integrated platform that produces testing equipment for both solar panels and solar cells. This results in greater reliability of test data and easier integration of data across the different value chains—something highly valuable to them. The solar energy market has responded with great enthusiasm to this deal.

For Bolster and its underlying investors, this deals represents a opportunity for genuine sustainable value creation.

Impact of This Deal on Society
The machines of Eternal Sun and Wavelabs are used for groundbreaking research into new solar technologies, such as perovskite. Perovskite solar panels are up to 50% more efficient than existing panels and significantly cheaper. The development of perovskite solar panels is a crucial step in meeting global climate targets. At present, no other companies are capable of building testing equipment at this level, and without Eternal Sun – Wavelabs, this research would, to a significant extent, not be possible. Therefore, the Eternal Sun Group plays a crucial role in the advancement of solar technology and in the energy transition as a whole.

Most Complex Aspect of This Deal
The most complex aspect of this deal was managing two highly competitive processes in parallel without exclusivity, while simultaneously navigating the import tariff war and continuously demonstrating to our investment committee and investors the value of this transaction.