Change search
Link to record
Permanent link

Direct link
BETA
Alternative names
Publications (10 of 45) Show all publications
Abuasbeh, M. (2018). Aquifer Thermal Energy Storage Insight into the future. Stockholm, Sweden
Open this publication in new window or tab >>Aquifer Thermal Energy Storage Insight into the future
2018 (English)Report (Refereed)
Abstract [en]

Underground Thermal Energy Storage (UTES) systems, such as Aquifer thermal energy storage(ATES) are used in several countries. The regulation and research on the potential impacts of ATESon groundwater resources and the subsurface environment often lag behind the technologicaldevelopment of an ever-growing demand for this renewable energy source. The lack of a clear andscientifically supported risk management strategy implies that potentially unwanted risks might betaken at vulnerable locations such as near well fields used for drinking water production. At othersites, on the other side, the application of ATES systems is avoided without proper reasons. Thisresults in limiting the utilization of the ATES technology in many occasions, affecting the possibilityto increase the share of renewable energy use. Therefore, further studies to characterizegroundwater resources, performance monitoring and identification of environmental impacts areneeded to understand the advantages and limitations of ATES systems.

The environmental impact and technical performance of a Low Temperature ATES (LT-ATES)system in operation since 2016 is presented. The system is called Rosenborg and is owned byVasakronan. It is located in the northern part of Stockholm, on a glaciofluvial deposit called theStockholm esker. The ATES system is used to heat and cool two commercial buildings with a totalarea of around 30,000 m2. The ATES consists of 3 warm and 2 cold pumping wells that are able topump up to 50 liters per second.

Analysis of groundwater sampling included a period of 9 months prior to ATES operation as well asthe first full season of heating and cooling operation. The sampling was conducted in a group ofwells in the vicinity of the installation and within the system. Means of evaluation constituted astatistical approach that included Kruskal-Wallis test by ranks, to compare the wells before and afterthe ATES was used. Then principal component analysis (PCA) and clustering analysis were used tostudy the ground water conditions change before and after the ATES. Aquifer Variation Ratio(AVR) was suggested as mean to evaluate the overall conditions of the aquifer pre- and post- ATES.

The results showed some variations in redox potential, particularly at the cold wells which likely wasdue to the mixing of groundwater considering the different depths of groundwater beingabstracted/injected from different redox zones. Arsenic, which has shown to be sensitive to hightemperatures in other research showed a decrease in concentration. A lower specific conductivityand total hardness at the ATES well compared to their vicinity was found. That indicates that theyare less subject to salinization and that no accumulation has occurred to date. It is evident that theenvironmental impact from ATES is governed by the pre-conditions in soil- and groundwater. ThePCA and clustering analysis showed very little change in the overall conditions in the aquifer whencomparing the ATES before and after operation. Temperature change showed negligible impact.This can be mainly attributed to the relatively small temperature change (+6 and – 5 degrees) fromthe undisturbed Aquifer temperature which is 10.5°C.

Performance of Aquifer Thermal Energy Storage (ATES) systems for seasonal thermal storagedepends on the temperature of the extracted/injected groundwater, water pumping rates and thehydrogeological conditions of the aquifer. ATES systems are therefore often designed to work witha temperature difference between the warm side and cold side of the aquifer without riskinghydraulic and thermal intrusion between them, and avoiding thermal leakage to surrounding area, i.e. optimize hydraulic and thermal recovery. The hydraulic and thermal recovery values of the first yearof operation in Rosenorg weres 1.37 and 0.33, respectively, indicating that more storage volume(50500m3) was recovered during the cooling season than injected (36900m3) in the previous heatingseason.

Monitoring the operation of pumping and observation wells is crucial for the validation of ATESgroundwater models utilized for their design, and measured data provides valuable information forresearchers and practitioners working in the field. After months of planning and installation work,selected measurements recorded in an ATES monitoring project in Sweden during the first threeseasons of operation are reported in this report.

The monitoring system consists of temperature sensors and flow meters placed at the pumpingwells, a distributed temperature-sensing rig employing fiber optic cables as linear sensor andmeasuring temperature every 0.25 m along the depth of all pumping and several observation wells,yielding temporal and spatial variation data of the temperature in the aquifer. The heat injection andextraction to and from the ground is measured using power meters at the main line connecting thepumping wells to the system. The total heat and cold extracted from the aquifer during the firstheating and cooling season is 190MWh and 237MWh, respectively. A total of 143 MWh of heatwere extracted during the second heating season. The hydraulic and thermal recovery values of thefirst year of operation was 1.37 and 0.33, respectively, indicating that more storage volume(50500m3) was recovered during the cooling season than injected (36900m3) in the previous heatingseason. The DTS data showed traces of the thermal front from the warm storage reaching the coldone. Only 33% of the thermal energy was recovered. These losses are likely due to ambientgroundwater flow as well as conduction losses at the boundaries of the storage volume. Additionally,the net energy balance over the first year corresponds to 0.12 which indicates a total net heating ofthe ATES over the first year. It is recommended to increase the storage volume and achieve morehydraulic and thermal balance in the ATES system. This can enhance the thermal recovery andoverall performance. Continuous monitoring of the ATES is and will be ongoing for at least 3 moreyears. The work presented in this report is an initial evaluation of the system aiming to optimize theATES performance.

Furthermore, data management and processing tool has been established for the ATES system in Rosenborg. Additionally, a conceptual model of the ATES area has been established. Current andfuture work is focussed on completing a full scale numerical model in FEFLOW and validated themodel (both hydraulically and thermally) with the available monitoring data. Furthermore,establishing recommendations for optimum design and operation of ATES system.

Abstract [sv]

Att lagra värme och kyla under markytan, exempelvis i grundvattnet i en akvifer, används världenrunt. Oftast arbetar dessa system med två brunnsgrupper, en kall och en varmgrupp, som viavärmeväxlare och eller värmepumpar till ett energisystem i en fastighet.

Syftet med ett säsongslager i en akvifer är oftast att arbeta inom rimliga temperaturer och vattenuttagoch garantera att det kalla och det varma lagret inte påverkar varandra, samt att systemet i sin helhetinte påverkar förhållanden i det omgivande grundvattnet.

Regelverk och forskning inom akviferlager ligger tyvärr några år bakom marknaden och dentekologiska utvecklingen, trots stort intresse för förnyelsebara energikällor. Bristen av vetenskapligtframtagen kunskap inom området medför därmed en ökad risk för fel i konstruktion, fel inom 

framtagning av underlag för bedömning av tillståndsansökningar samt för förorening avgrundvattnet. Det kan även hända att akviferlager förbjuds baserad på fel grunder. Eftersom dettakan resultera i en begränsad användning av denna förnyelsebara energikälla är det viktigt att utökakunskapsnivån inom karakterisering av grundvattenresurser, miljöpåverkan av akviferlager samtmätning och uppföljning av dessa system.

Miljöpåverkan och prestandauppföljning har under detta projekt utförts i ett lågt tempereratakviferlager, Rosenborg, som äggs av Vasakronan och som är i drift sedan 2016. Anläggningen ärplacerat i en del av Solnastad som passerar Stockhoms åsen.

Grundvattenkemi kan studeras med hjälp av regelbundna provtagningar och statistiska analyser.Provtagningar utfördes i observationsbrunnar placerade innanför och utanför lagret, och pågick frånoch med 9 månader innan anläggningen satts i drift till och med slutat av effsysprojektet, dvsprovtagningskampanjen inkluderade en helt kyl och värmelagringssäsong. Utvärderingen inkluderadeStatistiska metoder så som Kruskal-Wallis rangordningstester samt en data-driven metod så kalladPCA (från engelskan Principal Component Analysis) har använts, även klusteranalyser användes föratt studera och jämföra variationer i specifika kemiska komponenter i brunnarna före och efterdriftsättningen av akviferlagret. Varibeln AVR (Akvifer Variation Ratio) föreslogs som ett sätt attutvärdera kemisk påverkan i akviferen före och efter driftsättning på ett mer övergripande sätt.

Den kemiska analysen visade Redox variationer i de kalla brunnarna, som sannolikt berodde påblandning av grundvatten från olika djup (olika Redox potential). Arsenik, som är kännslig till högretemperaturer enligt tidigare utfört arbete, visade en minskning i koncentration. Akviferlagret visadeen lägre hårdhet (proportionell mängd kalcium och magnesium) och lägre konduktivitet än detomgivande grundvattnet, som betyder att lagret har varit mindre känslig till intrång av saltvatten frånomgivningen. PCA och klusteranalysen visade små ändringar före och efter driften. Detkonstaterades att temperaturändringarna (+6 K sommartid och -5 K vintertid) hade en försumbarpåverkan i relation till akviferens ostörda temperatur (10,5°C).

Eftersom energiprestanda i ett akviferlager är beroende av hydrauliska och termiska aspekter hardessa studerats i projektet genom att jämföra volymmängder grundvatten som pumpades ut och insamt utifrån temperaturbalansen över året, båda med hänsyn till akviferens hydrogeologiskaförhållanden. Begreppen hydraulisk och termisk återhämtning har använts för kvantifiering avakviferens prestanda. Resultatet för det första året blev en hydraulisk återhämtning lika med 1,37 ochden termiska återhämtningen 0,33. Den hydrauliska återhämtningen av 1,37 betyder att en störreandel (37%) av lagrets vattenvolym återanvändes under kyluttaget jämfört med värmeuttagsperioden.Den termiska återhämtningen, som är relaterad till den önskade temperaturnivån (10,5°C) ellerbörvärde har det första året visar att 67% mindre kyla har plockat upp i relation till värmeuttaget.Det är viktigt att hålla i åtanke att denna indikatör är starkt beroende på börvärdet somdriftpersonalen bestämmer. Mer förståelse kring hur det hydrauliska och termiska prestanda kan tasfram i fortsättningsprojektet med hjälp av uppföljning av vattenflöden, nivåer ochgrundvattentemperaturer i systemet som utförs via en state of the art mätsystem som har applicerasunder projektet. Av speciell relevans är det fiberoptiska systemet som har installerats i samtligapumpbrunnar samt i ett antal observationsbrunnar i akviferlagret. Systemet mäter var 25 centimeteroch täcker det mesta av lagrets volym. Mätningarna kan i fortsättningen användas för att validera ennumerisk modell som har tagits fram inom projektet med programmet FEFLOW.

Place, publisher, year, edition, pages
Stockholm, Sweden: , 2018. p. 42
Keywords
Heating, Free cooling, Heat pump, Thermal Energy storage, Aquifer, ATES, Groundwater, Monitoring, DTS, Värme, kyla, akviferlager, Termiska energilager
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-243835 (URN)
Projects
Effsys Expand P22: Heating and cooling from aquifer layers an insight into the future/Värme och kyla från akviferlager en inblick i framtiden
Funder
Swedish Energy Agency, Projektnummer 40942-1 Effsys Expand P22
Note

QC 20190211

Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2019-02-11Bibliographically approved
Abuasbeh, M. & Acuña, J. (2018). ATES SYSTEM MONITORING PROJECT, FIRST MEASUREMENT AND PERFORMANCE EVALUATION: CASE STUDY IN SWEDEN. In: Proceedings of the IGSHPA Research Track 2018: . Paper presented at IGSHPA Research Track 2018.
Open this publication in new window or tab >>ATES SYSTEM MONITORING PROJECT, FIRST MEASUREMENT AND PERFORMANCE EVALUATION: CASE STUDY IN SWEDEN
2018 (English)In: Proceedings of the IGSHPA Research Track 2018, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Performance of Aquifer Thermal Energy Storage (ATES) systems for seasonal thermal storage depends on the temperature of the extracted/injected groundwater, water pumping rates and the hydrogeological conditions of the aquifer. ATES systems are therefore often designed to maintain a temperature difference possible between the warm side and cold side of the aquifer, without risking hydraulic and thermal intrusion between them or thermal leakage to surrounding area, i.e. maximize hydraulic and thermal recovery. Monitoring the operation of pumping and observation wells is crucial for the validation of ATES groundwater models utilized for their design, and measured data provides valuable information for researchers and practitioners working in the field. After months of planning and installation work, selected measurements recorded in an ATES monitoring project in Sweden during the first three seasons of operation are reported in this paper. The ATES system is located in Solna, in Stockholm esker, and it is used to heat and cool two commercial buildings with a total area of around 30,000 m 2 . The ATES consists of 3 warm and 2 cold pumping wells that are able to pump up to 50 liters per second. The monitoring system consists of temperature sensors and flow meters placed at the pumping wells, a distributed temperature-sensing rig employing fiber optic cables as linear sensor and measuring temperature every 0.25 m along the depth of all pumping and several observation wells, yielding temporal and spatial variation data of the temperature in the aquifer. The heat injection and extraction to and from the ground is measured using power meters at the main line connecting the pumping wells to the system. The total heat and cold extracted from the aquifer during the first heating and cooling season is 190MWh and 237MWh, respectively. A total of 143 MWh of heat were extracted during the second heating season. The hydraulic and thermal recovery values of the first year of operation was 1.37 and 0.33, respectively, indicating that more storage volume (50500m3 ) was recovered during the cooling season than injected (36900m3 ) in the previous heating season. The DTS data showed traces of the thermal front from the warm storage reaching the cold one. Only 33% of the thermal energy was recovered. These losses are likely due to ambient groundwater flow as well as conduction losses at the boundaries of the storage volume. Additionally, the net energy balance over the first year corresponds to 0.12 which indicates a total net heating of the ATES over the first year. It is recommended to increase the storage volume and achieve more hydraulic and thermal balance in the ATES system. This can enhance the thermal recovery and overall performance. Continuous monitoring of the ATES is and will be ongoing for at least 3 more years. The work presented in this paper is an initial evaluation of the system aiming to optimize the ATES performance.

Keywords
Heat Pump, Heating, Free Cooling, DTS, Thermal energy storage, Aquifer, ATES, monitoring
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-243836 (URN)10.22488/okstate.18.000002 (DOI)
Conference
IGSHPA Research Track 2018
Funder
Swedish Energy Agency, Projektnummer 40942-1 Effsys Expand P22
Note

QC 20190211

Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2019-02-11Bibliographically 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
Show others...
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
Show others...
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
Mazzotti, W., Firmansyah, H., Acuña, J., Stokuca, M. & Palm, B. (2018). The Newton-Raphson MethodApplied to the Time-Superposed ILS for Parameter Estimation in Thermal Response Tests. In: Jeffrey Spitler, José Acuña, Michel Bernier, Zhaohong Fang, Signhild Gehlin, Saqib Javed, Björn Palm, Simon J. Rees (Ed.), Research Conference Proceedings: International Ground-Source Heat Pump Association Research Conference 2018. Paper presented at International Ground-Source Heat Pump Association Research Conference 2018 (pp. 208-218).
Open this publication in new window or tab >>The Newton-Raphson MethodApplied to the Time-Superposed ILS for Parameter Estimation in Thermal Response Tests
Show others...
2018 (English)In: Research Conference Proceedings: International Ground-Source Heat Pump Association Research Conference 2018 / [ed] Jeffrey Spitler, José Acuña, Michel Bernier, Zhaohong Fang, Signhild Gehlin, Saqib Javed, Björn Palm, Simon J. Rees, 2018, p. 208-218Conference paper, Published paper (Refereed)
Abstract [en]

Thermal Response Testing is now a well-known and widely-used method allowing the determination of the local thermal or geometrical properties of aBorehole Heat Exchanger (BHE), those properties being critical in the design of GSHP systems. The analysis of TRTs is an inverse problem that hascommonly been solved using an approximation of the ILS solution. To do this, however, the heat rate during a TRT must be kept constant, or least be nontime-correlated, during the test, which is a challenging constraint. Applying temporal superposition to the ILS model is a way to account for varying power,although it requires the use of an optimization algorithm to minimize the error between a parametrized model and experimental values.In this paper, the Newton-Raphson method is applied to the time-superposed ILS for parameter estimation in TRTs. The parameter estimation is limitedto the effective thermal conductivity and the effective borehole resistance. Analytical expressions of the first and second derivatives of the objective function,chosen as the sum of quadratic differences, are proposed, allowing to readily inverse of the Hessian matrix and speed the convergence process.The method is tried for 9 different TRTs, 2 of which are reference datasets used for validation of the method (Beier et al., 2010). Differences betweenestimated and reference thermal conductivities are of 3.4% and 0.4% for the first and second reference TRTs, respectively. The method is shown to be stableand consistent: for each of the 9 TRTs, 11 realizations are performed with different initial values. Convergence is reached in all cases and all realizationslead to the same final values for a given TRT.The proposed convergence method is about 70% to 90% faster than the Nelder-Mead simplex and require about 8 times less iterations in average. Theconvergence speed varies between 0.3 to 13.6 s with an average of 3.7 s for all TRTs.

Keywords
Thermal Response Test, Borehole Heat Exchanger, Inverse problem, Optimization, Newton-Raphson method
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-238586 (URN)10.22488/okstate.18.000039 (DOI)
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
Monzó, P., Lazzarotto, A. & Acuña, J. (2017). First Measurements of a Monitoring project on a BTES system. In: IGSHPA Technical/Research Conference and Expo, Denver, March 14-16, 2017: . Paper presented at IGSHPA Technical/Research Conference and Expo, Denver, March 14-16, 2017. International Ground Source Heat Pump Association
Open this publication in new window or tab >>First Measurements of a Monitoring project on a BTES system
2017 (English)In: IGSHPA Technical/Research Conference and Expo, Denver, March 14-16, 2017, International Ground Source Heat Pump Association , 2017Conference paper, Published paper (Refereed)
Abstract [en]

Performance of Borehole Thermal Energy Storage (BTES) systems depends on the temperature of the secondary fluid, circulating through the ground-loop heat exchangers. Borehole systems are therefore designed in order to ensure that inlet and outlet temperatures of the secondary fluid are within given operational limits during the whole life-time of the system. Monitoring the operation of the bore fields is crucial for the validation of existing models utilized for their design. Measured data provides valuable information for researchers and practitioners working in the field. A first data-set from an ongoing monitoring project is presented in this article. The monitoring system comprises temperature sensors and power meters placed at strategic locations within the bore field. A distributed temperature sensing rig that employs fiber optic cables as linear sensors is utilized to measure temperature every meter along the depth of nine monitored boreholes, yielding data regarding both temporal and spatial variation of the temperature in the ground. The heat exchanged with the ground is also measured via power meters in all nine monitored boreholes as well as at the manifold level. The BTES system is located at the Stockholm University Campus, Sweden, and consists of 130 boreholes, 230 meters deep. After more than a year of planning and installation work, some selected measurements recorded in the BTES during the first months of operation are reported in this article.

Place, publisher, year, edition, pages
International Ground Source Heat Pump Association, 2017
Keywords
ground source heat pump, monitoring project, BTES
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-202532 (URN)
Conference
IGSHPA Technical/Research Conference and Expo, Denver, March 14-16, 2017
Note

QC 20170330

Available from: 2017-02-26 Created: 2017-02-26 Last updated: 2018-02-28Bibliographically approved
Ignatowicz, M., Mazzotti, W., Acuña, J., Melinder, A. & Palm, B. (2016). Alternative alcohol blends as secondary fluids for ground source heat pumps. In: Refrigeration Science and Technology: . Paper presented at 12th IIR Gustav Lorentzen Natural Working Fluids Conference, GL 2016, 21 August 2016 through 24 August 2016 (pp. 610-617). International Institute of Refrigeration
Open this publication in new window or tab >>Alternative alcohol blends as secondary fluids for ground source heat pumps
Show others...
2016 (English)In: Refrigeration Science and Technology, International Institute of Refrigeration , 2016, p. 610-617Conference paper, Published paper (Refereed)
Abstract [en]

The most common secondary fluid used for the borehole heat exchangers in Sweden is an aqueous solution of ethyl alcohol (EA) due to its relatively good thermophysical properties and low toxicity. Commercially available ethyl alcohol based fluids in Sweden contain up to 10 wt-% denaturing agents in form of propyl alcohol (PA) and n-butyl alcohol (BA). The aim of this paper was to investigate the performance of the existing ethyl alcohol blend containing two denaturing agents and alternative alcohol blends in terms of the pressure drop and heat transfer in the BHE and comparison with ethyl alcohol based secondary fluid. Experimental results showed that the presence of these denaturing agents improves thermophysical properties such as specific heat capacity, thermal conductivity and dynamic viscosity when added in small concentration. EA18 + PA1.6 + BA0.4 and EA18.4 + PA1.6 present the best characteristics in terms of the heat transfer and pressure drop. Both blends are giving higher heat transfer coefficient by 9.4 % (EA18 + PA1.6 + BA0.4) and 8.11 % (EA18.4 + PA1.6) than pure EA20. Both blends are giving as well lower pressure drop than EA20 by up to 2.7 % (EA18 + PA1.6 + BA0.4) and 3 % (EA18.4 + PA1.6). EA18 + PA1.6 + BA0.4 gives 1.4 % higher heat transfer coefficient and EA18.4 + PA1.6 gives lower pressure drop by up to 0.4 % when these two blends are compared.

Place, publisher, year, edition, pages
International Institute of Refrigeration, 2016
Keywords
Borehole heat exchanger, Denaturing agents, Ethyl alcohol, Ground source heat pump, Propyl alcohol, Secondary fluid, Denaturation, Drops, Ethanol, Fluids, Heat exchangers, Heat pump systems, Heat transfer, Heat transfer coefficients, IIR filters, Pressure drop, Solutions, Specific heat, Thermodynamic properties, Borehole heat exchangers, Dynamic viscosities, Heat transfer and pressure drop, N-Butyl alcohols, Propyl alcohols, Secondary fluids, Small concentration, Geothermal heat pumps
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-207532 (URN)10.18462/iir.gl.2016.1098 (DOI)000402544400074 ()2-s2.0-85017581159 (Scopus ID)9782362150180 (ISBN)
Conference
12th IIR Gustav Lorentzen Natural Working Fluids Conference, GL 2016, 21 August 2016 through 24 August 2016
Note

Conference code: 126956; Export Date: 22 May 2017; Conference Paper; Funding details: Energimyndigheten; Funding text: The Swedish Energy Agency, Effsys Expand project and all industrial partners are greatly acknowledged for financing this project. QC 20170531

Available from: 2017-05-31 Created: 2017-05-31 Last updated: 2017-06-30Bibliographically approved
Monzó, P., Lazzarotto, A., Mazzotti, W. & Acuña, J. (2016). Borehole ThermalEnergy Storage: First stages of a monitoring  project. Geo Outlook, 13(3), 14-20
Open this publication in new window or tab >>Borehole ThermalEnergy Storage: First stages of a monitoring  project
2016 (English)In: Geo Outlook, Vol. 13, no 3, p. 14-20Article in journal (Other (popular science, discussion, etc.)) Published
Place, publisher, year, edition, pages
Oklahoma State University and the International Ground Source Heat Pump Association (IGSHPA), 2016
Keywords
ground source heat pump, borehole thermal energy storage, monitoring installation
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-193023 (URN)
Note

QC 20160928

Available from: 2016-09-26 Created: 2016-09-26 Last updated: 2016-09-28Bibliographically approved
Monzó, P., Lazzarotto, A., Acuña, J., Tjernström, J. & Nygren, M. (2016). Monitoring of a borehole thermal energy storage in Sweden. In: Per Kvols Heiseberg (Ed.), CLIMA 2016-proceedings of the 12th REHVA World Congress: volume 3: . Paper presented at 12th REHVA World Congress CLIMA, 22–25 May 2016. Aalborg University, Department of Civil Enginnering, 3
Open this publication in new window or tab >>Monitoring of a borehole thermal energy storage in Sweden
Show others...
2016 (English)In: CLIMA 2016-proceedings of the 12th REHVA World Congress: volume 3 / [ed] Per Kvols Heiseberg, Aalborg University, Department of Civil Enginnering, 2016, Vol. 3Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the description of the first stage of a project consisting on the monitoring of a newly installed borehole thermal energy storage (BTES) system that started to operate during the autumn of 2015. The BTES system is designed for approximately 4 GWh per year of heat injection and 3 GWh per year of heat extraction and will provide heating and cooling to a set of institutional facilities at Stockholm University, Sweden. The energy storage system consists of a set of 130 borehole heat exchangers, 230 meters deep. Strategic locations within the bore field have been selected to carry out the measurements. The monitoring system comprises temperature and energy flow meters. The temperature measurements are performed using a distributed temperature sensing set-up which allows to measure temperature along the depth of the boreholes, providing a large amount of data for the characterization of the thermal processes in the ground. During the upcoming years, the measured data will be utilized to evaluate and optimize the actual operational condition of the system, and to test the validity of assumptions made during the design phase. Moreover, the measured data will be utilized for validation of current bore field design methods and to have a better understanding of the thermal interaction between neighboring boreholes.

Place, publisher, year, edition, pages
Aalborg University, Department of Civil Enginnering: , 2016
Keywords
ground-coupled heat pump; multiple bore field; borehole heat exchanger; monitoring system
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-187482 (URN)87-91606-28-4 (ISBN)87-91606-36-5 (ISBN)
Conference
12th REHVA World Congress CLIMA, 22–25 May 2016
Funder
Swedish Energy Agency
Note

QC 20160603

Available from: 2016-06-02 Created: 2016-05-24 Last updated: 2019-08-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3490-1777

Search in DiVA

Show all publications