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Advances in Geosciences An open-access journal for refereed proceedings and special publications
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Volume 45 | Copyright
Adv. Geosci., 45, 85-103, 2018
https://doi.org/10.5194/adgeo-45-85-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

  07 Aug 2018

07 Aug 2018

The effect of a density gradient in groundwater on ATES system efficiency and subsurface space use

Martin Bloemendal1,2 and Theo N. Olsthoorn1 Martin Bloemendal and Theo N. Olsthoorn
  • 1Delft University of Technology, Stevinweg 1, Delft, the Netherlands
  • 2KWR Watercycle Research institute, Groningenhaven 7, Nieuwegein, the Netherlands

Abstract. A heat pump combined with Aquifer Thermal Energy Storage (ATES) has high potential in efficiently and sustainably providing thermal energy for space heating and cooling. This makes the subsurface, including its groundwater, of crucial importance for primary energy savings. ATES systems are often placed in aquifers in which salinity increases with depth. This is the case in coastal areas where also the demand for ATES application is high due to high degrees of urbanization in those areas. The seasonally alternating extraction and re-injection between ATES wells disturbs the preexisting ambient salinity gradient causing horizontal density gradients, which trigger buoyancy flow, which in turn affects the recovery efficiency of the stored thermal energy.

This section uses analytical and numerical methods to understand and explain the impact of buoyancy flow on the efficiency of ATES in such situations, and to quantify the magnitude of this impact relative to other thermal energy losses. The results of this research show that losses due to buoyancy flow may become considerable at (a relatively large) ambient density gradients of over 0.5kgm−3m−1 in combination with a vertical hydraulic conductivity of more than 5mday−1. Monowell systems suffer more from buoyancy losses than do doublet systems under similar conditions.

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Aquifer Thermal Energy Storage Systems (ATES) save energy for heating and cooling. They are often placed in aquifers in which salinity increases with depth (in coastal areas where urbanization is high). The seasonally alternating extraction and re-injection between ATES wells disturbs the preexisting ambient salinity gradient which trigger buoyancy flow, which in turn affects the recovery efficiency of these systems. This paper shows under which condtions this is a threat for ATES systems.
Aquifer Thermal Energy Storage Systems (ATES) save energy for heating and cooling. They are...
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