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Renewable energy


Driving change trough renewable energy

• Stoelzle begins a collaboration with Finnish start-up Polar Night Energy
• Sand battery stores excess green energy in peak times
• Regaining green electricity from the storage is our next goal


In autumn 2022, Stoelzle participated in an innovation pitch, which was organised by the Austrian Chamber of Commerce. As an energy-intensive industrial company, Stoelzle is constantly seeking innovative ideas in which to help reduce energy consumption in all production processes, as well as increasing the use of green energy. As the glass manufacturer already gains green energy (waste heat from furnaces and green electricity from photovoltaic panels) the next step was finding a way to store excess green energy.

The innovation pitch came up with a couple of great ideas, and Stoelzle decided to take a closer look at Polar Night Energy; a small start-up company from Finland, founded by Markku Ylönen and Tommi Eronen.

This innovative company has developed a patented sand-based thermal energy storage. It is the world's first commercial solution to store electricity in the sand as heat to be used in a district heating network. “As a material, sand is durable and inexpensive and can store a lot of heat in a small volume at a temperature of about 500–600 degrees Celsius”, explains Markku Ylönen. The first storage of this kind has successfully been installed in the town of Kankaanpää, Finland. Heat storages can significantly help to increase intermittent renewables in the electrical grid. At the same time, waste heat can be used to heat homes. This is a step towards combustion-free heat production.

Niklas Zwettler, Head of R&D at Stoelzle Glass Group, continues to lead this project and further steps are being explored to extend the process. “Glass production is a very energy intensive process. We have set ourselves the target to halve our CO2 emissions by 2030, and become carbon-neutral by 2050. So far, Polar Night Energy has discovered a way of extracting heat to warm water and feed local heating systems. Now, we need to discover how to retrieve electricity from the energy that is stored in the sand, in order to have a reliable source of green electricity to fire our furnaces. We’re excited to see how this system will work for us”, Zwettler explains.

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