LMS Master's student awarded the 2022 RIE Prize.

© 2022 EPFL

© 2022 EPFL

Annik Schaufelberger has received the 2022 RIE Prize for her Master’s thesis in Civil Engineering at EPFL on storing thermal energy in the ground using underground infrastructure.

The Laloui Group continues to gain recognition for its expertise in sustainable geo-energy structures and thermal energy recovery. This time, a Master’s student Annik Schaufelberger has been recognized for her contributions to the subject receiving the RIE prize for 2022.

Annik Schaufelberger won the award for her thesis, which focused on the thermal energy storage potential of energy tunnels, that is, tunnels equipped with ground heat exchangers inside the concrete lining. The concept behind energy tunnels serving as sustainable underground thermal energy storage systems is based on injecting thermal energy (harvested through thermal solar panels) over the heat exchangers inside the tunnel into the surrounding ground during summer; in winter, the heat is extracted again and can be enhanced through a heat pump to allow its usage in a heating system. The ground around the tunnel is thus used as a “thermal battery,” reducing the reliance on traditional thermal energy sources, which are often heavy emitters of greenhouse gasses while applying a practical solution to heat energy storage – a challenge for most renewable energy platforms.

A previous study has demonstrated that an energy tunnel serving as an underground thermal energy storage system can reach efficiencies of up to 70% - that is, 70% of the previously injected heat can later be extracted and used for heating.1 Under the supervision of Professors Lyesse Laloui from EPFL and Alessandro Rotta Loria from Northwestern University, the goal of Schaufelberger’s work was to numerically investigate how groundwater flow and the heat exchange with the tunnel air influence the performance of a tunnel thermal energy storage system.

Using the Turin metro system, Ms. Schaufelberger showed that thermal losses increase with increased air and groundwater flow velocity and reduced thermal insulation. These results suggest tunnel environments without groundwater flow, with high air temperatures inside the tunnel and the addition of more thermal insulation on the tunnel lining is the most effective means of ensuring high thermal efficiencies in energy tunnels.

The Association of Research and Innovation in Energy (RIE) awards prizes to bachelor’s and master’s students in Western Switzerland for innovative work in the energy technology sector. Speaking after the award ceremony, Schaufelberger said she felt very honored. ” It really means a lot to me. I had moments when I thought I would not get meaningful results in the given time frame. When I finally got some results, I was a little disappointed because they showed that the applied storage concept is not implementable under certain circumstances due to great heat losses. In the end, and with the help of Professors Laloui and Rotta Loria, I had to accept that acknowledging rather discouraging results is also an important part of research and that it is not always possible to get a spectacularly good outcome in the investigations.”

Ms. Schaufelberger is currently working as part of the Laloui Group at the LMS to deepen her understanding of thermal energy storage employing an energy tunnel to publish the results of her Master’s thesis in a scientific paper. At which point, she plans to work as a civil engineer in underground construction and geotechnics.


1. Rotta Loria, A. F. 2021. “The thermal energy storage potential of underground tunnels used as heat exchangers.” Renewable Energy, 176: 214–227. https://doi.org/10.1016/j.renene.2021.05.076.