When we think about concrete, our minds jump to the usual suspects – sidewalks, buildings, bridges, and roads. But what if concrete also holds the key to affordable, renewable energy storage?
André Gennesseaux is the founder of Energiestro, an energy storage company that uses prestressed concrete in flywheels to store renewable energy safely and affordably. Founded in 2001, Energiestro’s mission is to provide energy storage at a fraction of the cost of batteries. According to Gennesseaux, energy storage is the biggest barrier to expansion of widespread renewable energy production and usage.
“Moving away from fossil fuels is not a technical problem because we have a lot of renewable energies,” he said. “The problem is cost. People will switch when the price is right.”
Energiestro’s storage solution is a flywheel that relies on prestressed concrete. Flywheels are cylinders that rotate at high speeds to store kinetic energy. Energiestro’s flywheel is designed to be used in conjunction with solar panels, storing solar energy safely so that consumers can tap into this energy at any time of day.
According to Gennesseaux, flywheels could solve the shelf-life problem faced by batteries. The materials could also be easily recycled, unlike many batteries. Earlier in his career, he wanted to explore how flywheels could serve as energy storage solution and pitched his idea to his employer. When they were not ready to fund the idea, he decided to quit and found Energiestro.
Developing the flywheel as an energy storage solution was an iterative process. Over the course of the next decade, the Energiestro team tried again and again to make this solution work.
“First we tried steel but we found that the cost of steel was too high,” he said. “And then we tested cast iron, which is cheaper than steel but still too expensive. Finally, we decided to think about something really different. We’ve tried all of the classic materials. What’s next?”
Gennesseaux decided to give concrete a shot. Concrete is cheap and readily accessible but posed one significant problem – it doesn’t work well with flywheels. Gennesseaux thought he could adapt both concrete and the flywheel to work together. He decided to try prestressed concrete, which is extremely compressed concrete. He then adapted the flywheel to access the energy by reducing the compression rather than pulling on the material. To Gennesseaux’s surprise, concrete not only worked but it far exceeded expectations.
“Not only did it work, the concrete flywheel stored energy at one-tenth of the cost of batteries,” he said. “I didn’t trust the results at first. I had to check it many times before I was convinced!”
With this breakthrough under his belt, Gennesseaux turned his attention to developing prototypes and attracting investors. In a fortuitous turn of events at the time, a former classmate appealed to Gennesseaux to serve as a presenter for a 2015 TED talk series in France.