Smart heat buffer with ATES technology

HTO Delft – seasonal heat storage beneath the TU Delft Campus

On the TU Delft campus, Gaia Energy is collaborating on an innovative pilot for underground High-Temperature Storage (HTS). By storing geothermal heat at 80–90°C during the summer and making it available again in the winter, a robust and flexible heating system is created for both the campus and the city.

Smart storage for the energy system of the future

A sustainable energy system requires not only clean heat sources but also efficient storage. Heat demand is seasonal: it is highest in the winter, while there is often a surplus of heat in the summer.

High-Temperature Storage (HTS) bridges this gap. Excess geothermal heat is stored underground during the summer and recovered in the winter. This:

• further reduces the use of fossil fuels
• lowers CO₂ emissions
• increases security of supply
• reduces grid congestion

HTO Delft thus forms an important building block in the decarbonization of urban heating networks.

How does underground seasonal storage work?

The system utilizes suitable water-bearing geological layers at a depth of several hundred meters. Hot water (40–90°C) can be temporarily stored here. During cold periods, this heat is recovered and fed into the heating network.

The storage is connected to the Geothermie Delft geothermal source and to ground-source energy systems on campus. This creates an integrated system in which production, storage, and distribution work together optimally.

The TU Delft campus serves as a living lab: a place where practice, research, and innovation converge.

European collaboration: PUSH-IT

HTO Delft is part of the European research program PUSH-IT (Piloting Underground Seasonal Heat Storage In geothermal reservoirs), funded by Horizon Europe.

Within this international consortium, universities and research institutions work together, including:

• TU Delft
• Fraunhofer IEG
• BRGM
• VITO
• TU Darmstadt

Gaia Energy acts as an operator and knowledge partner in this project. We contribute our expertise in geothermal energy and underground systems to ensure the technology is applied safely and scalably.

Innovation with impact

The pilot in Delft is one of the most advanced high-temperature heat storage projects in Europe. By combining heat production and storage, we create a more stable and efficient system that:

• better aligns with seasonal heat demand
• is less dependent on peak-load facilities
• is scalable to other urban areas

HTO Delft demonstrates that the combination of geothermal energy, storage, and heat networks is a viable path toward a future-proof heat supply.

Want to know more about the pilot project in Delft? Watch the video and read more on the website of PUSH-IT.

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