Future research recommendations

As per the aim of this study and the conclusions drawn, it is suggested that the legislation applied to geothermal heat pump systems adapt to the current scholarly advancements. This can be in the form of imposing thresholds on groundwater flow, above which groundwater shall not be ignored. Such integration could be eased by the research community through finding simply applicable methods such as flow-dependant design factors or monograms. Likewise, the developments in computation techniques such as flow-heat coupled numerical models and more recent analytical solutions should be implemented in the process of designing BHEs.

Groundwater flow has been proven to be potentially one of the most influential factors on BHEs; it was also determined to be an even more effective factor during times when the BHE is not operational, i.e. thermal recovery. Hence, the possibility of

employing natural or artificial groundwater flow as a measure to improve the long-term thermal sustainability of closed loop geothermal heat pump systems needs to be further explored.

The effect of in-borehole factors, i.e. loop temperatures or grout thermal

conductivity, on the heat exchange efficiency has been examined under semi-steady state conditions; however, in reality the state of heat transfer inside a BHE is highly transient. Thus, for a more accurate estimation of in-borehole properties on BHE performance it is suggested to further study them under transient state replicating the real-world conditions.

The practice of freezing the ground and benefiting from the latent heat of icing has been stated, as a theoretically effective underground energy storage method. Due to the limitation of the model used in this study, simulation codes capable of accounting for latent heat during icing-thawing of the groundwater, e.g. SUTRA-ICE, should be used. This can ideally be accompanied by laboratory experiments especially to test the

practicality of this approach, e.g. damage from the ice expansion to heat exchanger pipes and the seal. Geotechnical concerns need also to be considered.

The dramatic effect of balance, or lack thereof, in system energy load, on the long-term performance and impact of multi-BHE systems has been observed almost at its extremes. It could be of interest to model some in-between cases in the future. It is also motivated to find the sensitivity of BTES systems to groundwater flow based on loop temperatures during storage and extraction phases, with non-storage ordinary multi-BHE systems with balanced energy load at one end.

Single borehole heat exchangers have been put in a number of heterogeneous environments with low complexity. As a future study proposal, multi-borehole systems could be placed in more complex settings. This could eventually demonstrate the amount of difference between an ideally laid out borehole array and a poor placement as well as the error emerged from not comprising the fracture hydraulic discontinuities.

This study sheds doubt on feasibility of thermal response testing for long-term planning of borehole heat exchangers in highly heterogeneous media like fractured rock. More research on interpreting TRT results in fractured rock is needed. This includes further computer simulation of hypothetical tests. Possibility of accurately estimating the apparent thermal conductivity of a borehole field through point measurements of thermal conductivity, and site investigation techniques is explorable.

Curriculum Vitae

Name: S. Emad Dehkordi

Post-secondary University of Western Ontario

Education and London, Ontario, Canada

Degrees: 2009-2013 Ph.D.

Royal Institute of Technology (KTH) Stockholm, Sweden

2007-2009 M.Sc.

Sharif University of Technology Tehran, Iran

2000-2005 B.Sc.

Honours and Western Graduate Research Scholarship (WGRS)

Awards: 2009-2013

Canadian Geophysical Union (CGU) Student Travel Award 2011

ERASMUS (EuRopean Community Action Scheme for the Mobility of University Students) grant

2008

Related Work Graduate Teaching Assistant

Experience: University of Western Ontario

2009-2013

Graduate Research Assistant University of Western Ontario 2009-2013

Related publications:

Papers and Abstracts:

• Dehkordi, S.E., R.A. Schincariol, and B. Olofsson. Effect of horizontal and

vertical fractures on borehole heat exchangers. Intended for The Bulletin of

Engineering Geology and the Environment (currently in manuscript format)

• Dehkordi, S.E., R.A. Schincariol, and B. Olofsson. Thermal Impact of

Groundwater Flow on Multiple Borehole Heat Exchanger Systems. Groundwater

• Nakevska, N., R.A. Schincariol, S.E. Dehkordi, and B.A. Cheadle. Geothermal

Waste Heat Utilization from In-situ Thermal Bitumen Recovery. Groundwater

(submitted 15 August 2013)

• Dehkordi, S.E., and R.A. Schincariol. 2013. Effect of Thermal-Hydrogeological

and Borehole Heat Exchanger Properties on Performance and Impact of Vertical

Closed Loop Geothermal Heat Pump Systems. Hydrogeology Journal (published

online 30 October 2013; to be published in the 2014 theme issue: Hydrogeology of Shallow Thermal Systems). DOI 10.1007/s10040-013-1060-6

• Dehkordi, S.E., and R.A. Schincariol. 2013. Impact of Groundwater Flow on

Thermal Energy Storage and Borehole Thermal Interference. Geophysical

Research Abstracts (Proceedings of European Geosciences Union General Assembly 2013), Vol. 15, EGU2013-7838

• Dehkordi, S.E., and R.A. Schincariol. Vertical Low Temperature Geothermal

Heat Pump Systems International Guidelines and Design Approach: Current

Status and Perspective. Canadian Geotechnical Journal (first submitted 31 May

2012; accepted with major revisions 14 February 2013; revision submitted 31 March 2013)

• Dehkordi, S.E., and R.A. Schincariol. 2012. Thermal Effect of Hydrogeological

Factors on Closed-loop Ground Source Geothermal Systems, In Proceedings of

3rd International FEFLOW® _{User Conference, Berlin, Germany}

Conferences and Meeting Presentations:

• Dehkordi, S.E., and R.A. Schincariol. 2013. Impact of Groundwater Flow on

Thermal Energy Storage and Borehole Thermal Interference. European

Geosciences Union General Assembly 2013, 7-12 April 2013, Vienna, Austria

• Dehkordi, S.E., and R.A. Schincariol. 2012. Thermal Effect of Hydrogeological

Factors on Closed-loop Ground Source Geothermal Systems, 3rd International

FEFLOW® _{User Conference, 3-5 September 2012, Berlin, Germany}

• Dehkordi, S.E., and R.A. Schincariol. 2012. Low-temperature Geothermal

Energy: Opportunities and Obstacles, Canadian Society for Civil Engineering (CSCE) and Canadian Geotechnical Society (CGS) monthly meeting, London, ON, Canada

• Dehkordi, S.E., and R.A. Schincariol. 2011. Regulations on Geothermal Heat

Pump (GHP) Systems – Thermal Impacts and Areas for Improvement in

Hydrogeological Context, Canadian Geophysical Union (CGU) annual meeting conference, Banff, AB, Canada