Heating and cooling using aquifer thermal energy storage (ATES) has hardly been applied outside the Netherlands, even though it could make a valuable contribution to the energy transition. The Climate-KIC project “Europe-wide Use of Energy from aquifers” – E-USE(aq) – aimed to pave the way for Europe-wide application of ATES, through the realization and monitoring of six ATES pilot plants across five different EU countries. In a preceding paper, based on preliminary results of E-USE(aq), conclusions were already drawn, demonstrating how the barriers for this form of shallow geothermal energy can be overcome, and sometimes even leveraged as opportunities. Based on final pilot project results, key economic and environmental outcomes are now presented. This paper starts with the analysis of specific technological barriers: unfamiliarity with the subsurface, presumed limited compatibility with existing energy provision systems (especially district heating), energy imbalances and groundwater contamination. The paper then shows how these barriers have been tackled, using improved site investigation and monitoring technologies to map heterogeneous subsoils. In this way ATES can cost-efficiently be included in smart grids and combined with other sources of renewable (especially solar) energy, while at the same time achieving groundwater remediation. A comparative assessment of economic and environmental impacts of the pilots is included, to demonstrate the sustainability of ATES system with different renewables and renewable-based technologies. The paper concludes with an assessment of the market application potential of ATES, including in areas with water scarcity, and a review of climate beneficial impact.

Aquifer Thermal Energy Storage (ATES) system make use of the groundwater to exchange energy with the building: in winter, groundwater is pumped from the warm well to the buildings heat exchanger and the building extracts heat from the groundwater as energy source for the heat pumps, while the groundwater will be injected in the cold well at lower temperature; in summer, the direction will be reversed and groundwater will be pumped out of the cold well to the heat exchanger, where the building will gather cold from the groundwater. ATES combined with solar collectors at two sites in Belgium and the Netherlands proved to allow for additional efficiencies and energy savings. Pilot sites showed promising results for combining ATES with groundwater remediation by enhanced natural attenuation for chlorinated solvents. Pilot sites were also realized in two countries with a less mature ATES market, Spain and Italy. In Spain an innovative hybrid technology between a closed loop and an open loop system has been tested, allowing ATES to be used also in water scarcity conditions. In Italy, a small scale integration with a cold low temperature district heating system has been realized. Technical and economic performances of the pilots are briefly described. The lessons learnt in the pilots provide useful insights for the replication of these solutions.

A transition to a low carbon energy system is needed to respond to global challenge of climate change mitigation. Aquifer Thermal Energy Storage (ATES) is a technology with worldwide potential to provide sustainable space heating and cooling by (seasonal) storage and recovery of heat in the subsurface. However, adoption of ATES varies strongly across Europe, because of both technical as well as organizational barriers, e.g. differences in climatic and subsurface conditions and legislation respectively. After identification of all these barriers in a Climate-KIC research project, six ATES pilot systems have been installed in five different EU-countries aiming to show how such barriers can be overcome. This paper presents the results of the barrier analysis and of the pilot plants. The barriers are categorized in general barriers, and barriers for mature and immature markets. Two pilots show how ATES can be successfully used to re-develop contaminated sites by combining ATES with soil remediation. Two other pilots show the added value of ATES because its storage capacity enables the utilization of solar heat in combination with solar power production. Finally, two pilots are realized in countries with legal barriers where ATES systems have not previously been applied at all.

Our soils can provide sustainable energy. Aquifer Thermal Energy Storage (ATES) is a smart way to re-use heat and cold in buildings and it is widely recognized as promising technology for sustainable energy. Global demand for heating and cooling in the built environment accounts for about 40% of total primary energy consumption. ATES is a simple way of meeting that demand by using the soil. The Climate-KIC project ‘Europe-wide Use of Sustainable Energy from aquifers’ – E-USE(aq) – demonstrated how ATES systems can be implemented in several countries. It included six pilot projects in five countries that will generate a flywheel effect for the introduction of ATES systems throughout Europe.