By Caspar Birk, AAU Kommunikation og Public Affairs
Photo: Astrid Helene Mortensen

One of the biggest challenges in the green transition is the ability to store excess electricity from solar panels and wind turbines to be used on calm, overcast days.

Now, researchers from Aalborg University have brought us closer with an advanced technology that has just been published in the scientific journal Cell Reports Physical Science.

“We have created a thermal emitter that not only survives extreme temperatures but also operates stably for over six months. This represents a major step towards practical thermal batteries,” says associate professor Manohar Chirumamilla from the Department of Materials and Production at Aalborg University.

Instead of storing energy in chemical form (like batteries), thermal batteries store excess renewable electricity as heat in inexpensive and scalable materials. That stored heat can be converted back into electricity when demand rises using thermophotovoltaic cells-specialized devices that convert infrared radiation into electricity.

Over 10 years of work

The newly developed nanostructured emitter from Aalborg University is a 2D photonic crystal that functions as a high-temperature light source. When heated up to 1400 °C, it emits tailored electromagnetic radiation that is precisely matched to the spectrum solar cells can utilize.

The emitter’s nanostructure is built from yttria-stabilized zirconia particles on a tungsten reflector, which provides exceptional thermal stability and makes it suitable for both long-term storage of green energy and recovery of waste heat in industrial processes.

“Up to half of the energy in industry is lost as heat. With our technology, a large portion of that can be recovered – and either used directly or converted into electricity,” says Manohar Chirumamilla.

He has worked on this technology for over 10 years.

“In the beginning, we worked with a temperature around 600 °C. In the past six years, we’ve gone from 1000 °C to up to 1400 °C, which has increased the emitter’s power density by a factor of 13,” explains Manohar Chirumamilla.

Ready for the next step – and close to market

The emitter system has been developed in collaboration with Technische Universität Hamburg, Universität Hamburg, and Helmholtz-Zentrum Hereon (a German research center), and is now mature enough to be scaled up for industrial use. The next step is to collaborate with companies to test the technology in practice.

“We’ve shown that the emitter can withstand extreme temperatures over long periods. Now it’s about building the full system and demonstrating how it can work in real-world scenarios – for example, in a Danish industrial company,” says Manohar Chirumamilla.