Aquifer thermal energy systems

Aquifer thermal energy is a source of renewable energy that is very much on the rise. It involves pumping a relatively large amount of groundwater, and raising and lowering the temperature, usually by small amounts. Deltares can draw on our knowledge of groundwater and piping systems to provide sound advice about complex challenges. Deltares does not install or manage aquifer thermal energy systems itself and that helps to keep our advice independent.

Research into the effects of subsurface energy

Thermal energy storage systems can affect the subsurface. The number of systems is now increasing rapidly. However, the hydrological conditions and properties of the systems determine the extent of any possible impact. Particularly in the research programme ‘More with Subsurface Energy’, Deltares worked with partners IF Technology, Bioclear and Wageningen University to measure and assess the effects. This knowledge is now being used by designers, policymakers and permit authorities to manage the negative impact of ATES. The effects of temperature variation and groundwater displacement that were studied are hydraulic head changes, interference, groundwater quality and groundwater ecology. The study has demonstrated, among other things, that the injection temperature can be raised from 25°C to 30°C in many situations.

ATES and soil remediation

ATES is being used increasingly in urban areas, which is where most soil pollution and/or remediation operations are located. ATES can have a positive or negative effect on the contaminants. The systems can contribute to the more efficient cleanup of locations by establishing a smart link between the two technologies. However, the higher intensity of the dynamics in the groundwater can complicate the cleanup, or the spread, of pollutants.

ATES and thermal energy from other sources

Deltares has explored the possibilities of combining ATES with other technologies. Examples are cooling water processes, the storage of fresh water and the use of surface water to transport heat or cold. We have also worked with TNO to examine the option of thermal energy storage in salt caverns. The European research project E-use (aq) has been established to investigate the options for the export of knowledge about ATES for combined concepts.

Troubleshooting and improved energy performance in ATES systems

Drilling for ATES is relatively expensive, which is why it is important to obtain the maximum amount of information from boreholes. Deltares borehole measurements provide detailed information about the lithology of the subsurface and groundwater. This makes it possible, for example, to optimise the filter systems, monitor clay seals and regulate fresh-salt transitions. The temperature distribution in the subsurface can be measured using fibre optic cables in monitoring wells (or probes). These are continuous measurements that create a dynamic picture of the development of the cold and hot zones. Modelling can be used with this monitoring technology to detect clogging in filters at an early stage and to optimise the efficiency of the source system.

Support for policy processes

We use our knowledge to help government authorities decide about granting permits for ATES. We conducted an evaluation for the provincial authority of Flevoland (NL) of the permit conditions for monitoring ATES in the light of the potential risks. In addition, we have also advised about complications and interference. Deltares has developed an approach to make an integrated assessment of the interests that play a role in the subsurface.

Optimal management of heating and cooling demand for clusters of buildings

If there is more demand for heating and cooling from several buildings in a given area, the management and coordination of the ATES plant become more complicated. The aim is to prevent disruptive interference, and to use the source systems as efficiently as possible in order to minimise the energy loss. Deltares is working on several projects to optimise and simulate the real-time management of large air-conditioning systems with multiple sustainable and conventional sources. That involves predicting demand for heat/cold on the basis of the weather forecast, after which the use of the various sources is optimised while the current situation is continuously updated.