Just five years after graduating from the YES!Delft start-up incubator, Eternal Sun BV has acquired Spire Solar, the solar-testing division of its U.S. competitor, Spire Corp.

Both companies focus on sun-simulation technologies that allow solar panel developers to test the power, efficiency, and reliability of their products, with Spire Corp having been in the business for more than 40 years versus the much younger Eternal Sun. The latter hopes that this acquisition will support its efforts to work across the entire solar industry value chain. 

Eternal Sun’s business focuses on testing solar panels using a solar simulator – essentially a testing rig that can simulate sunlight really really well. As one can imagine, this capability can be quite valuable for solar panel researchers and companies who want to test their designs and equipment in terms of solar degradation and lifetime performance. 

The rig itself was designed by the company’s founders - Chokri Mousaoui and Stefan Roest - in late 2010. The pair had been developing a new solar panel design at the Delft University of Technology (TU Delft) and wanted to test its performance. According to Mousaoui, he and Roest were unable to find accurate testing and measurement equipment to test their design across the full spectrum contained in sunlight. In turn, they developed their own testing rig that quickly became much more interesting than their solar panel.

Today, Mousaoui and Roest hope to support informed investments in solar power technologies by providing a reliable way to test the performance of solar panel technologies. While their business to date has focused on testing solar technologies in the R&D stage, their recent acquisition will allow them to expand their work through the entire manufacturing supply chain.

I spoke with Mousaoui, who serves as Eternal Sun’s CEO, while he was in Boston to facilitate the transition of Spire Corp’s solar-testing division into their new Eternal Sun facility in the United States. Below is an edited and condensed version of that discussion.

Eternal Sun CEO Chokri Mousaoui by Eternal Sun (used with permission)

Melissa C. Lott: You have said that Eternal Sun’s sun-simulation technology was born out of necessity. Can you tell me more about the state of the industry in late 2010, when you and Stefan built your first rig?

Chokri Mousaoui: My co-founder, Stefan, and I were developing a new type of thin-film solar module – a combination of a hybrid thermal solar collector – where you had thin-film solar modules on the front to generate electricity and then canals of water running along the back to collect the heat. We knew that flashing – where you flash the solar panel with light for a fraction of a second and the module responds to the light – wasn’t going to be sufficient to test the full capabilities of the thin-film modules. That was, I think, October 2010. 

As such, we developed a prototype that was just meant to validate our module. In the beginning of 2011, we finally developed the prototype and received the results on our solar module that we could use. Then, a Professor visited us and said ‘folks – you have reached a very interesting standard with this sun simulator – you have reached the highest norm of testing for solar modules. You should patent this’.

At about the same time, there was a scientific conference at TU Delft and researchers there started recognizing the prototype and asking ‘who built this?’. The first question they had was if we sold the design.

That was actually our launch as a company. One of our first companies was the TU Delft and they published results from their research by applying our machine. That created a lot of buzz within the research community around the world. We sold our first two machines in the Netherlands, the third went to Korea, and the fourth to India. It went very fast.


Lott: How has your company developed since then? Are researchers still your main customers and do you expect this to change with the acquisition of Spire Solar?

Mousaoui: As Eternal Sun we have mainly sold our machines to research institutions, scientific bodies, and technical universities for conducting degradation studies and for long-term accelerated life testing studies on solar panels and their behaviour. That’s what we did until January of this year.

The Spire Solar acquisition will make it so that we now cover the entire solar value chain, which is defined as follows:

  1. R&D institutions – they start with developing new types of solar cells and would like to test them on their performance, reliability, degradation, etc. to validate and then go into…
  2. Mass production – cell manufacturing and module manufacturing. And then it goes to…
  3. Certification authorities and institutions – who test the specific module that is produced

With Eternal Sun, we were involved in the first and last step. Now with the Spire Solar acquisition, we cover the entire solar value chain.

At Eternal Sun, we currently have around 30 rigs in operation around the world. With Spire Solar, we have over 700 machines. It was a bit of a David and Goliath move.


Lott: Manufacturing for Eternal Sun equipment is done in the Netherlands and Spire Solar is in the US – do you expect to maintain the two bases as part of your expansion?

Mousaoui: Yes, and at the same time, we are asking ourselves two strategic questions.

First – Should we have all of our manufacturing together in the same place?

Second – Should we move some or all of our manufacturing to Asia?

For the first question, we really like that Spire Solar is a strong brand name with US-made products and customers trust this. I have been visiting customers in six continents in the past two months for Spire Solar and believe that it’s important that we should leave this business in Boston.

For the second question, we realised that we are a low-volume, high-quality and high-specialized products. China is a good fit if you have high-volume, low-tech instruments or components. So, we decided not to outsource anything in terms of manufacturing for now and are working to become leaner.


Lott: What part of this work is most exciting for you?

Mousaoui: That’s a very interesting and tough question to answer. What really excites me is that we are working on the frontline – on the forefront – of innovation. That’s what really really excites me and motivates me. With Eternal Sun, we have different types of applications in addition to solar including automotive and electronic devices and the chemical industry.

It’s really cool to walk into a large automotive company to their special testing lab – where you leave your mobile phone and laptop in the car because you aren’t allowed to take them with you – and see their latest car that they will show the world next year. Also, when I was at a large electronics company two years ago to visit their labs, we got to see some phones that weren’t every out there yet that they wanted to test. It is really cool to see how we are working at the forefront of innovation in so many industries.


Lott: On that topic – if I was in your shoes, I think that one of the challenges I would face is the large number of things that your technology can do. The large number of potential applications. How do you manage this challenge in your own growth as a company?

Mousaoui: Truth is that we have never called a company out of nothing to talk about selling our technology. We receive at least a dozen requests per month of companies in different industries and we tell them the price and timeline and focus on low-hanging fruit like solar.

But, now that we are expanding, we have been developing a strategic roadmap for our growth looking at the different industries. We are taking it an industry at a time – right now, we have the solar industry and are trying to consolidate the value chain there in 2016. Next year, we are looking at the automotive industry.