City-scale heating and cooling with Aquifer Thermal Energy Storage (ATES)
Abstract. Sustainable and climate-friendly space heating and cooling is of great importance for the energy transition. Compared to conventional energy sources, Aquifer Thermal Energy Storage (ATES) systems can significantly reduce greenhouse gas emissions from space heating and cooling. Hence, the objective of this study is to quantify the technical potential of shallow low-temperature ATES systems in terms of reclaimable energy in the city of Freiburg im Breisgau, Germany. Based on 3D heat transport modeling, heating and cooling power densities are determined for various hydrogeological subsurface characteristics and ATES configurations. High groundwater flow velocities of up to 13 m d-1 cause high storage energy loss limiting power densities to a maximum of 3.2 W m-2. Nevertheless, comparison of these power densities with the existing thermal energy demands shows that ATES systems can achieve substantial heating and cooling supply rates. This is especially true for the cooling demand, for which a full supply by ATES is determined for 92 % of all residential buildings in the study area. For ATES heating alone, potential greenhouse gas emission savings of up to about 70,000 tCO2eq a-1 are calculated, which equals about 40 % of the current greenhouse gas emissions caused by space and water heating in the study areas’ residential building stock. The modeling approach proposed in this study can also be applied in other regions with similar hydrogeological conditions to obtain estimations of local ATES supply rates and support city-scale energy planning.
Ruben Stemmle et al.
Status: final response (author comments only)
- RC1: 'Comment on hess-2023-62', Jannis Epting, 30 Apr 2023
- RC2: 'Comment on hess-2023-62', Anonymous Referee #2, 14 May 2023
Ruben Stemmle et al.
Ruben Stemmle et al.
Viewed (geographical distribution)
The paper "City-scale heating and cooling with Aquifer Thermal Energy Storage (ATES)" presented by Stemmle et al. represents an interesting case study that builds on previously developed methods. A new aspect is the simultaneous consideration of heating and cooling.
One major drawback is the missing information on the city-scale model (setup, parameterization, boundary conditions, calibration / validation, etc.). It is also not apparent whether this information has been published elsewhere.
The use of an “ambient temperature of 12 °C” should be justified. The use of an "ambient temperature of 12 °C" should be justified. In Freiburg, groundwater temperatures vary greatly, and the starting point will be different depending on the aquifer region.
The latter two aspects also lead me to decide that major revisions are needed.
More sepecific comments include:
p. 1, l. 13: provide information on the aquifer, unconsolidated gravel aquifer, …
p. 1, l. 13: specify «limiting power densities» aquifer
p. 2, l. 53: GWHP was already introduced, check whole text
p. 3, l. 65: “2D numerical box models” include: F. Bottcher, A. Casasso, G. Gotzl, K. Zosseder, TAP - thermal aquifer Potential: a quantitative method to assess the spatial potential for the thermal use of groundwater, Renew. Energy 142 (2019) 85e95.
p. 3, l. 76: GHG was already introduced, check whole text
p. 3, l. 94: specify “lower hydraulic conductivity”
Fig. 1a: missing scale bar (maybe zoom in, include Voges); m asl
Fig. 1b: flow direction of river Dreisam (maybe zoom in, show 10m equidistance); m asl
Fig. 1c: requires x-scaling, legend for lithologies, turn m asl 180°
Section 2.2.: Required? No new equations are developed. Reference could be sufficient.
Table 1: 4.4 E-3; 6 E-5 (reference personal communication?); References for standard values appropriate?
Fig. 2 could be merged with Fig. 1
Table 2: Value representation? Simplify & avoid repetitions.
p. 7, l. 170: Why estimated?
p. 7, l. 174.176: What is the difference between uniform and constant thickness?
p. 8, l. 193: Specify “substantial”
Fig. 4: turn labeling right axis asl 180°
p. 8, l. 211: When is thermal equilibrium reached? This measure maybe is more appropriate compared to the lifetime.
p. 10, l. 232-233: Discuss “ambient temperature of 12 °C”
p. 10, l. 249: Table 3?
p. 12, l.301: It would make sense to also calculate the SCOP as seasonal operation is investigated.
p. 13, eq. 14: see Epting et al. 2018
p. 17, l. 421-428: Compare to Epting et al. 2018 & 2020
Good luck and all the best,