High-Temperature Aquifer Thermal Energy Storage
Thermal energy storage, and high-temperature thermal energy storage in particular, plays a key role in the energy system of the future. By making energy available at the right time, peaks and troughs in supply and demand can be managed more effectively. This not only makes the system more sustainable, but also more stable and efficient. This form of energy storage is often abbreviated as HT-ATES.
Thermal energy storage is playing an increasingly important role in the energy transition. High-temperature thermal energy storage enables geothermal energy to be used more effectively by temporarily storing surplus heat and making it available again during colder periods. This creates a flexible and efficient energy system that better aligns energy supply with demand.
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Developments in High-Temperature Aquifer Thermal Energy Storage
The development of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) has accelerated significantly in recent years. Energie Beheer Nederland (EBN) is closely involved in this development and contributed to the innovation programme WarmingUP. Within this consortium, research was conducted into how thermal energy storage can evolve into a proven and widely applicable technology.
As part of this work, quick scans were carried out at many locations to assess the feasibility of High-Temperature Aquifer Thermal Energy Storage. A number of promising projects were subsequently developed further. This resulted in pilot drillings and testing activities in, among other locations, Rotterdam-Nesselande, Leeuwarden and Delft. These practical experiences provide valuable insights into how thermal energy storage can be applied both technically and economically.
The knowledge gained is being further developed within WarmingUp GOO. This programme once again examines suitable locations for High-Temperature Aquifer Thermal Energy Storage and works on concrete system designs. At the same time, programmes such as NieuweWarmteNu! and Push-IT are taking further steps towards implementation. An important example is the development of a High-Temperature Aquifer Thermal Energy Storage facility in Delft, for which an investment decision was taken at the end of 2025.
Thermal Energy Storage in a Broader Perspective
In addition to High-Temperature Aquifer Thermal Energy Storage (HT-ATES), interest in Medium-Temperature Thermal Energy Storage (MTES) is also growing. Both forms of thermal energy storage use open-loop subsurface energy systems but differ in operating temperature levels. High-Temperature Aquifer Thermal Energy Storage focuses on higher temperatures, while MTES operates at slightly lower temperatures, bridging the gap between HT-ATES and conventional Aquifer Thermal Energy Storage (ATES) systems.
At present, MTES is primarily being explored for use in the greenhouse horticulture sector, although it also appears to have strong potential for the built environment. An important condition applies: buildings must be well insulated and suitable for heating at lower temperatures. This development highlights that thermal energy storage, in its various forms, is set to play an increasingly important role in a sustainable energy system.
From Research to Implementation
In addition to research, EBN is actively involved in project implementation. For example, it participated in pilot drilling projects in Leeuwarden and Delft and conducted additional research alongside the pilot drilling project in Rotterdam-Nesselande. The results from the first two locations showed that the subsurface is suitable for high-temperature thermal energy storage. In Rotterdam-Nesselande, however, it was decided to discontinue the storage project for several reasons.
A concrete next step is now being taken in Delft. The expectation is that the wells for thermal energy storage will be drilled by mid-2026, after which the above-ground installations will be constructed. If everything proceeds according to plan, the facility could be commissioned by the end of 2026 or early 2027. This project is supported by the European research programme Push-IT.
At the same time, efforts continue to further optimise the technology. This includes reducing the cost of pilot drilling and improving well designs to lower the overall costs of thermal energy storage. The potential application of high-temperature thermal energy storage within other geothermal energy projects is also being explored.
A notable example of innovation is a tool designed to optimise the use of geothermal energy, thermal energy storage and complementary technologies such as heat pumps. The tool also takes electricity consumption and grid congestion into account. Insights such as these support better investment decisions and help make thermal energy storage even more effective.
EBN’s Role in High-Temperature Aquifer Thermal Energy Storage
EBN actively contributes to the development of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) through research, pilot projects and collaboration with industry partners. In 2022, a study was conducted to assess whether storing heat at high temperatures is technically feasible and economically viable at specific locations. This study led to the development of a subsurface model that can calculate the efficiency of thermal energy storage under various heat supply and demand scenarios.
The analyses show that a good balance between heat supply and demand is essential. The amount of heat available in surplus during the summer must be utilised during the winter to cover seasonal mismatches between supply and demand. Only under these conditions can thermal energy storage become economically viable.
In addition, EBN collaborates with organisations such as TNO and IF Technology on studies into the role of thermal energy storage in the energy system of the future. These studies indicate that thermal energy storage, alongside natural gas storage and hydrogen storage, will become an important pillar of the energy system leading up to 2050. The most relevant reports resulting from this collaboration are listed below.