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Publications (5 of 5) Show all publications
Fascì, M. L. & Lazzarotto, A. (2019). A novel model for the estimation of thermal influence of neighbouring borehole heat exchangers. In: EGEC (Ed.), EUROPEAN GEOTHERMAL CONGRESS 2019: THE HAGUE, 11-14 JUNE 2019. Paper presented at European Geothermal Congress 2019.
Open this publication in new window or tab >>A novel model for the estimation of thermal influence of neighbouring borehole heat exchangers
2019 (English)In: EUROPEAN GEOTHERMAL CONGRESS 2019: THE HAGUE, 11-14 JUNE 2019 / [ed] EGEC, 2019Conference paper, Published paper (Refereed)
Abstract [en]

Ground source heat pumps (GSHPs) connected to vertical boreholes are popular systems to provide heat and/or refrigeration in residential and commercial buildings. The diffusion of these systems poses the question on how to effectively and sustainably handle the underground thermal resource without overexploiting it. In particular, this question can rise in densely populated areas where either heat extraction or heat rejection is dominant.Although several models are available and used to estimate the thermal influence between individual boreholes or group of hydraulically connected boreholes, the development of models that can quantify the thermal influence of neighbouring boreholes having different boundary conditions (it is the case for individual GSHP installations located in the same neighbourhood) is still at its early stages. The availability of such tools is essential both to enable the legislators to set appropriate rules for the allocation of the underground thermal resource and to enable the designers to properly size these systems.In this paper, we develop a model based on the stacked finite line source method that is tailored to estimate the thermal interaction of neighbouring GSHPs. The model takes as input the heat load of each GSHP and imposes uniform temperature on every borehole. The model is applied to a fictitious densely populated area to calculate the temperature changes on the boreholes walls of the systems. The results are compared with the results obtained with another model previously proposed by the authors.

Keywords
Ground source heat pumps, thermal influence, neighbouring boreholes, stacked finite line source
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-255168 (URN)
Conference
European Geothermal Congress 2019
Note

QC 20190902

Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-09-02Bibliographically approved
Mazzotti, W., Jiang, Y., Monzó, P., Lazzarotto, A., Acuña, J. & Palm, B. (2018). Design of a Laboratory BoreholeStorage model. In: Jeffrey Spitler, José Acuña, Michel Bernier, Zhaohong Fang, Signhild Gehlin, Saqib Javed, Björn Palm, Simon J. Rees (Ed.), Research Conference Proceedings: . Paper presented at International Ground-Source Heat Pump Association Research Conference 2018 (pp. 400-410).
Open this publication in new window or tab >>Design of a Laboratory BoreholeStorage model
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2018 (English)In: Research Conference Proceedings / [ed] Jeffrey Spitler, José Acuña, Michel Bernier, Zhaohong Fang, Signhild Gehlin, Saqib Javed, Björn Palm, Simon J. Rees, 2018, p. 400-410Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the design process of a 4x4 Laboratory Borehole Storage (LABS) model through analytical and numerical analyses. This LABS isintended to generate reference Thermal Response Functions (TRFs) as well as to be a validation tool for borehole heat transfer models. The objective of thisdesign process is to determine suitable geometrical and physical parameters for the LABS. An analytical scaling analysis is first performed and importantscaling constraints are derived. In particular, it is shown that the downscaling process leads to significantly higher values for Neumann and convectiveboundary conditions whereas the Fourier number is invariant. A numerical model is then used to verify the scaling laws, determine the size of the LABS,as well as to evaluate the influence of top surface convection and borehole radius on generated TRFs. An adequate shape for the LABS is found to be aquarter cylinder of radius and height 1.0 m, weighing around 1.2 tonnes. Natural convection on the top boundary proves to have a significant effect on thegenerated TRF with deviations of at least 15%. This convection effect is proposed as an explanation for the difference observed between experimental andanalytical results in Cimmino and Bernier (2015). A numerical reproduction of their test leads to a relative difference of 1.1% at the last reported time.As small borehole radii are challenging to reproduce in a LABS, the effect of the borehole radius on TRFs is investigated. It is found that Eskilson’sradius correction (1987) is not fully satisfactory and a new correction method must be undertaken.

Keywords
Laboratory model, Borehole storage, Downscaling, Thermal response function, Experiment design
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-238595 (URN)
Conference
International Ground-Source Heat Pump Association Research Conference 2018
Projects
Deep boreholes for Ground-Source Heat Pumps
Funder
Swedish Energy Agency
Note

QC 20181106

Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2018-11-06Bibliographically approved
Malmberg, M., Mazzotti, W., Acuña, J., Lindståhl, H. & Lazzarotto, A. (2018). High temperature borehole thermal energy storage - A case study. In: Jeffrey Spitler, José Acuña, Michel Bernier, Zhaohong Fang, Signhild Gehlin, Saqib Javed, Björn Palm, Simon J. Rees (Ed.), Research Conference Proceedings: . Paper presented at International Ground-Source Heat Pump Association Research Conference 2018, March 27-29 (pp. 380-388).
Open this publication in new window or tab >>High temperature borehole thermal energy storage - A case study
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2018 (English)In: Research Conference Proceedings / [ed] Jeffrey Spitler, José Acuña, Michel Bernier, Zhaohong Fang, Signhild Gehlin, Saqib Javed, Björn Palm, Simon J. Rees, 2018, p. 380-388Conference paper, Published paper (Refereed)
Abstract [en]

Combining High-Temperature Borehole Thermal Energy Storages (HT-BTES) with existing Combined Heat and Power (CHP) systems running on waste fuels seems to be a promising approach to increase the energy efficiency of district heating systems through recovery of excess heat summertime from the waste-to-energy operation. This paper presents a case study from Sweden where the potential for charging and discharging waste heat at 95°C from a CHP-plant in summer into and from a HT-BTES is investigated. The interaction between the HT-BTES and the CHP-plant has been simulated with the software tool TRNSYS using the DST (Duct Ground Heat Storage Model) and a number of other TRNSYS tools. The aim of the study has been to design the size and operation of the HT-BTES with regard to energy and power coverage. Several different potential system configurations are presented in this paper, with 1 300 to 1 500 boreholes of 300 m depth. The result shows that it is possible to retrieve around 93 GWh/year of stored heat winter time, with the use of heat pumps using ammoniac as refrigerant. The discharge temperatures from the BTES range between 40-60°C, and up to 70°C in the initial discharge period.

Keywords
High Temperature borehole thermal energy storage, HT-BTES, Ground Source Heat Pump, GSHP, TRNSYS, Combined Heat and Power, CHP
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-238596 (URN)10.22488/okstate.18.000036 (DOI)
Conference
International Ground-Source Heat Pump Association Research Conference 2018, March 27-29
Note

QC 20181106

Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2018-11-06Bibliographically approved
Fasci, M. L., Lazzarotto, A., Acuña, J. & Claesson, J. (2018). Shallow Geothermal Heat Pumps: a study of the resource potential at a neighbourhood scale.. In: : . Paper presented at ICNTSE 2018.
Open this publication in new window or tab >>Shallow Geothermal Heat Pumps: a study of the resource potential at a neighbourhood scale.
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The residential sector accounts for a relevant share of global energy use; therefore it is important to use as much renewable energy as possible to satisfy its demand. Geothermal energy, among others, is nowadays used for this scope: more and more buildings in several countries are exploiting the underground to satisfy domestic heating, cooling and hot water demand by means of ground-source heat pumps. On the long run heat extraction/injection can lead to depletion of the ground as heat source/sink. Current tools only allow a designer to take into account the depletion of the ground caused by the system she or he is designing. However, the actual total heat depletion is also influenced by the surrounding systems. With the growing diffusion of ground-source heat pumps the ability of estimating the total underground heat depletion is of paramount importance. The aim of the article is to give an insight of the problem: the goal is to show what will happen in the underground if residential ground source heat pump systems are designed without taking into account the presence of neighbouring installations. The study is performed for different types of soil and borehole heat exchangers designs.

Keywords
Ground source heat pumps, thermal influence, neighbouring boreholes, geothermal sustainability
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-246395 (URN)
Conference
ICNTSE 2018
Note

QCR 20190402

Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-04-02Bibliographically approved
Fasci, M. L., Lazzarotto, A., Acuña, J. & Claesson, J. (2018). Thermal influence of neighbouring GSHP installations: Relevance of heat load temporal resolution. In: Proceedings of the IGSHPA Research Track 2018: . Paper presented at International Ground Source Heat Pump Association Research Track 2018.
Open this publication in new window or tab >>Thermal influence of neighbouring GSHP installations: Relevance of heat load temporal resolution
2018 (English)In: Proceedings of the IGSHPA Research Track 2018, 2018Conference paper, Published paper (Refereed)
Abstract [en]

In densely populated areas where many ground source heat pump (GSHP) systems are present, it becomes important to consider the thermal influence ofneighbouring GSHP installations while designing these systems. This question has started to become frequent in cities like Stockholm in Sweden. For thedesign and performance analyses of the GSHP systems, simulations at different detail levels regarding time step are used. Borehole heat loads of realinstallations can be estimated with different time resolution from case to case. This article presents a first step towards the development of a model to calculatethe mutual influence of neighbouring GSHP installations: a first elementary model is developed to quantify such influence, then the error introduced whenperforming simulations with different heat load steps, i.e. annual and hourly, is analyzed from a perspective of multiple neighbouring GSHP installations.It is found that a negligible error is derived when considering low temporal resolution data.

National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-255257 (URN)10.22488/okstate.18.000019 (DOI)
Conference
International Ground Source Heat Pump Association Research Track 2018
Note

QC 20190902

Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-10-02Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0550-2769

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