Aquifer Thermal Energy Systems (ATES) show potential for sustainable cities by providing heating and cooling through the seasonal storage of thermal energy in underground aquifers. Two PhD studies examined the impacts of heterogeneity, thermal interference between systems, and opportunities for bioremediation of chlorinated ethenes in Aquifer Thermal Energy Storage (ATES). Modeling and monitoring of case studies in the Netherlands provided insights into thermal performance, heat transport, and the effect of heterogeneity. Combining ATES with bioremediation stimulated the degradation of contaminants like cis-DCE. Challenges remain in optimizing the integrated management of subsurface resources for sustainable energy and contaminated site remediation.

1. Aquifer Thermal Energy Systems
(ATES) for sustainable cities
interference and bioremediation opportunities
Pauline van Gaans
Wijb Sommer, Zhuobiao Ni
Johan Valstar, Tim Grotenhuis, Huub Rijnaarts

2. 5 Nov 2015 Infra for Water & Energy
2 PhD studies in MMB-project
2
Bioremediation of Chlorinated Ethenes
in
Aquifer Thermal Energy Storage
Zhuobiao Ni

3. Context (1)
sustainable energy demand
potential increase in NL to
≈ 20 000 systems in 2020
5 Nov 2015 Infra for Water & Energy
Source: CBS
Groundwater use in the
Netherlands (CBS, 2011)
Sector Volume (Mm3/yr)
Water companies 757
Industry 141
Agriculture 89
Food and beverage
industry 67
Chemical industry 12
3

4. Context (2)
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Bonte et al. PhD thesis (2013)

5. Thermal performance and heat transport in ATES
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Monitoring of Utrecht Uithof case study, operational data & subsurface temperature
(fibre optic cables)
comparison with ..
numerical modelling
8 wells, 15-50 m depth
operational since 2002
~ 500 000 m3/yr
~ 1700 MWh cooling
~ 1700 MWh heating
Thermal recovery:
• heat 68%
• cold 82%
Energy (im)balance:
• yearly 33%
• cumulative 0-18%
Well clogging:
Flow rates distributed unequally
More injection  more clogging

6. Thermal performance and heat transport in ATES
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Effect of heterogeneity on system performance, stochastic modelling
Heterogeneity reduces thermal recovery
When well spacing is sufficient (>Rth) effects are smaller
For smaller well spacing: uncertainty

7. Thermal interference, case study The Hague & optimisation
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Thermal recovery 70%-90%:
Interference -10% - +10%
overall improving performance!
Half of interference within single systems
Optimisation (cost reduction) most
sensitive to:
• Gas price
• ∆T cold well – warm well
3 Rth
R1 = 3 Rth
R2 = 0.5 Rthsensitivity analysis

8. ATES-ENA: Potential for subsurface conditioning
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Improving redox condition stimulates
biodegradation, but primary limitation is
abundance of proper microorganisms
Implementation of bioremediation
stimulation must be location specific
Prior monitoring of redox potential can be
advantageous in view of cost-effectiveness
• Low natural PCE biodegradation potential
• Redox condition is limiting (Fe(III) reducing)
 Redox improvement by electron donor

9. cis-DCE biodegradation under ATES and BTES conditions
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Both systems perform significantly better in cis-DCE
removal than natural situation (overall removal rates
for ATES 13x and for BTES 8.5x higher)
Dehalococcoides prefer to attach to sediments
In controls without Dehalococcoides, only limited
incomplete degradation till VC is observed

10. Microbial resilience to redox changes & clogging
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Microbial resilience of
DHC to nitrate is weak.
Recovery of reductive
dechlorination requires
extra effort and is difficult.
DHC prefers to attach to
the soil matrix. Under
harsh redox conditions,
DHC detach and are
flushed out.
Column resistance, as
indicator for clogging,
increases due to nitrate
addition (formation of
Fe2O3), but decreases
when lactate is added.
No increase is observed
along with total biomass
growth.

11. Reactive transport modelling
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Mathematical framework developed by Malaguerra et al. (2011)
Calibrated to laboratory studies of Scheutz et al. (2008)
Temperature dependence following Friss et al. (2007)
Double axi-symmetric flow tube model (DAFT, Bonte et al., 2014)
Malaguerra et al. (2011)

12. Challenges for urban sustainability
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• Integrated local management of the subsurface
• optimisation of sustainable energy potential
• more active regional management of contaminated urban aquifers
• ecosystem services approach
• Improved long term perspective in risk assessment of ATES in
contaminated aquifers
• Improved coupling in modelling of ATES systems
• above ground system – subsurface system
• flow and transport – reactive chemistry
• Well-monitored ATES pilots
• More and smarter use of operational monitoring

13. Publications
Sommer, Wijbrand, (2015). Modelling and monitroing of aquifer thermal energy storage. Impacts of heterogeneity, thermal
interfenrence and bioremediation. PhD Thesis Wageningen University, June 4, 2015.
Sommer, W.T., Drijver, B.C., Verburg, R., Slenders, H., de Vries, E., Dinkla, I., Leusbrock, I. and Grotenhuis, J.T.C. (2013). Combining
shallow geothermal energy and groundwater remediation. In Proceedings of the European Geothermal Congress 2013, 03-07 June
2013, Pisa, Italy.
Sommer, W.T., Valstar, J., van Gaans, P.F.M., Grotenhuis, J.T.C., and Rijnaarts, H.H.M. (2013). The impact of aquifer heterogeneity on
the performance of aquifer thermal energy storage. Water Resources Research 49(12), 8128-8138.
Bakr, M., van Oostrom, N., and Sommer, W.T. (2013). Efficiency of and interference among multiple aquifer thermal energy storage
systems; A Dutch case study. Renewable Energy 60, 53-62.
Sommer, W.T., Doornenbal, P.J., Drijver, B.C., van Gaans, P.F.M., Leusbrock, I., Grotenhuis, J.T.C. and Rijnaarts, H.H.M. (2014).
Thermal performance and heat transport in aquifer thermal energy storage. Hydrogeology Journal, 22(1), 263-279.
Sommer, W.T., Valstar, J., Leusbrock, I., Grotenhuis, J.T.C. and Rijnaarts, H.H.M. (2015). Optimization and spatial pattern of large-scale
aquifer thermal energy storage. Applied energy, 137, 322-337.
Zeghici, R., Oude Essink, G., Hartog, N. and Sommer, W.T. (2015). Integrated assessment of variable density-viscosity groundwater flow
for a high temperature mono-well aquifer thermal energy storage (HT-ATES) system in a geothermal reservoir. Geothermics, 55,
58-68.
Sommer, W., Ni, Z., Valstar, J., van Gaans, P., Grotenhuis, T., Rijnaarts, H. Reactive transport modeling of TCE bioremediation
combined with aquifer thermal energy storage. (to be submitted).
Ni, Zhuobiao, (2015). Bioremediation of Chlorinated Ethenes in Aquifer Thermal Energy Storage. PhD Thesis Wageningen
University, December 8, 2015.
Ni, Z.; Smit, M.; Grotenhuis, T.; van Gaans, P.; Rijnaarts, H. (2014). Effectiveness of stimulating PCE reductive dechlorination: A step-
wise approach. Journal of Contaminant Hydrology, 164(0), 209-218.
Ni, Z., van Gaans, Pauline; Smit, Martijn; Rijnaarts, Huub; Grotenhuis, Tim, 2015. Biodegradation of cis-DCE in Simulated Underground
Thermal Energy Storage Systems. Environmental Science & Technology, (accepted) Manuscript ID: es-2015-030687.R2
Ni, Zhuobiao; Smit, Martijn; van Gaans, Pauline; Rijnaarts, Huub; Grotenhuis, Tim, Combination of Aquifer Thermal Energy Storage and
Enhanced Bioremediation: Resilience of Reductive Dechlorination to Redox Changes. Submitted to Applied Microbiology and
Biotechnology.
Ni, Z.; van Gaans, P.; Rijnaarts, H.; Grotenhuis, T., Combination of aquifer thermal energy storage and enhanced bioremediation:
biological and chemical clogging. (to be submitted).
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Questions?