The Firm

For his graduation project, Stefan Roest developed a solar panel. When he wanted to test it, the sun was nowhere to be found. There was no artificial sun available for sale, so he built his own. He had identified a gap in the market, as the success of Roest’s company Eternal Sun demonstrates.

Roest can well remember walking around the car park behind the faculty of Electrical Engineering, Mathematics and Computer Science in 2010. He was in search of sunlight, pulling a cart with his self-designed solar panel and measuring equipment. He knew he had a success on his hands: a solar panel that can generate electricity and hot water. All he needed to do was prove it. But it was the start of autumn and the sky was overcast. “On the only sunny day there was, a crane was blocking out the sunlight. How can I ever get any good test
results?”

“I need an artificial sun,” replied Roest to his own question. Now, over four years later, he tells his story, standing by just that kind of simulator. It is a three-by-two metre colossus that mimics sunlight with 98 percent accuracy. In 2014, Eternal Sun achieved an annual turnover in the region of a million euros and he has big ambitions. With good reason: the solar energy market is booming and new products need to be tested.

Before Roest had even graduated, it was already clear that his artificial sun would fill a gap in the market. As he was working on it, he was contacted by someone from TNO, asking if he could have a simulator like that. With a friend from the Virgiel student association, SEPAM student Chokri Mousaoui, he drew up a quotation and quickly set up his own company. It was the right move. “We had two more customers in no time. We joined up with YesDelft (the TU Delft incubator for start-ups) and hired two people.” Things continued to move fast. “We received an order for three units from South Korea. It took nine of us eight months to build them.”

Business then started to go quiet. “We had not focused enough on marketing. It was touch-and-go for a while. Fortunately, new projects quickly emerged in Turkey, India and the Netherlands.” Last year, the company struggled to deal with the sheer number of requests. That was why Roest and Mousaoui decided to look for an investor.

The resulting two million euros have enabled Eternal Sun to hire staff, move to a bigger location and update the product. “Every unit we build is slightly better. I would recommend that to everyone: do not wait until your product is fully developed. Always try to deliver something, even if it is just a prototype. Often that is already enough for the customer. And always discuss with customers what they need. They are what keeps you in business.”

Name: Stefan Roest (30) Studied: Sustainable energy technology Company: Eternal Sun Established in: 2011 Product: Solar simulator Mission: Contribute towards renewable energy/sustainable products Sales: Around a million euros in 2014 And in five years?: "Eternal Sun will be at least ten times the size it is now." (Photo © Sam Rentmeester)

Name: Stefan Roest (30)
Studied: Sustainable energy technology
Company: Eternal Sun
Established in: 2011
Product: Solar simulator
Mission: Contribute towards renewable energy/sustainable products
Sales: Around a million euros in 2014
And in five years?: “Eternal Sun will be at least ten times the size it is now.”
(Photo © Sam Rentmeester)

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