| 1. |
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| 2. |
- Andersson, Anderz, 1953-, et al.
(author)
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Arbetsrätt
- 2021. - 7
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Book (other academic/artistic)abstract
- Syftet med den här boken är att ge läsaren grundläggande kunskaper i arbetsrätt och den svenska modellen. I fokus för framställningen står den arbetsrättsliga lagstiftningens framväxt, arbetsmarknadens parter, medbestämmande, anställningsskydd, arbetsmiljö och skydd mot diskriminering. Andra områden som behandlas är arbetstidsregleringen och ledighetslagstiftningen. Vidare behandlas EU-arbetsrättens inverkan på den svenska lagstiftningen.
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| 3. |
- Andersson, Staffan, 1952-, et al.
(author)
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Building performance based on measured data
- 2011
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In: World Renewable Energy Congress – Sweden, 8–13 May, 2011, Linköping, Sweden. - Linköping : Linköping University Electronic Press. - 9789173930703 ; , s. 899-906
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Conference paper (peer-reviewed)abstract
- With increasing liability for builders, the need for evaluation methods that focuses on the building’s performance and thus excludes the impact from residents’ behavior increases. This is not only of interest for new buildings but also when retrofitting existing buildings in order to reduce energy end-use. The investigation in this paper is based on extensive measurements on two fairly representative type of buildings, a single family building in Ekerö, Stockholm built 2000 and two apartment buildings in Umeå (1964) in order to extract key energy performance parameters such as the building’s heat loss coefficient, heat transfer via the ground and heat gained from the sun and used electricity. With access to pre-processed daily data from a 2-month periods, located close to the winter solstice, a robust estimate of the heat loss coefficient was obtained based on a regression analysis. For the single family building the variation was within 1% and for the two heavier apartment buildings an average variation of 2%, with a maximum of 4%, between different analyzed periods close to the winter solstice. The gained heating from the used electricity in terms of a gain factor could not be unambiguously extracted and therefore could only a range for the heat transfer via ground be estimated. The estimated range for the transfer via ground for the two apartment buildings were in very good agreement with those calculated according to EN ISO 13 370 and corresponded to almost 10% of the heating demand at the design temperature. For the single family building with an insulated slab and parts of the walls below ground level, the calculations gave slightly higher transfer than what was obtained from the regression analysis. For the estimated gained solar radiation no comparison has been possible to make, but the estimated gain exhibited an expected correlation with the global solar radiation data that was available for the two apartment buildings.
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| 4. |
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| 5. |
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| 6. |
- Andersson, Staffan, 1952-, et al.
(author)
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Thermal conductivity and heat capacity of amorphous SiO2 : pressure and volume dependence
- 1992
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In: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 4:29, s. 6209-6216
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Journal article (peer-reviewed)abstract
- The thermal conductivity (lambda) and heat capacity per unit volume (rho-c(p)) of amorphous SiO2 have been measured under hydrostatic pressure up to 1 GPa at room temperature using a transient two-strip method. The thermal conductivity was found to decrease slightly with increasing pressure. For the volume dependence of lambda expressed by the Bridgman parameter, g = -(partial derivative ln lambda/partial derivative ln V)T, we obtained g = -1.5. The experimental value of g is discussed in conjunction with predicted g-values based on theoretical models of lambda(T). The specific heat capacity (c(p)) calculated from measured rho-c(p) was found to be almost constant with increasing pressure.
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| 7. |
- Andersson, Staffan, 1952-
(author)
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Utvärdering av energieffektiva armaturer
- 2015
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Reports (other academic/artistic)abstract
- Rapporten redovisar en genomförd uppföljning av den erhållna minskningen av varm- respektive kallvattenanvändningen genom installation av energieffektiva armaturer. Utvärderingen baseras på 23 månaders mätningar av den individuella vattenanvändningen i sjuttiosju lägenheter (21 test-samt 56 referenslägenheter). Testlägenheterna utrustades först med en tidigare generations vattenarmaturer, FM Mattsson serie 9000, vilka senare ersattes med den senaste generationens armaturer FM Mattson serie 9000E. I fem av dessa lägenheter har dessutom komplementerande mätningar gjorts vid de olika tappställena, WC undantagen. Användningen av varm- och kallvattenanvändningen i varje lägenhet har loggats med en tidsupplösning om 10 minuter. För att undvika påverkan av boendes frånvaro från lägenheterna har uppföljningen baserats på den genomsnittliga dygnsanvändningen av vatten för de tider de boende har nyttjat lägenheten. Lägenheter där byte av hyresgäster har skett under utvärderingsperioden har lämnats utanför utvärderingen. De erhållna resultaten visar på en besparing om cirka 30% avseende varmvattenanvändningen samt 15% avseende kallvatten jämfört med referensgruppen. Den erhållna uppskattningen är också konsistent med en teoretisk uppskattning av besparingen baserad på den mätta förändringen av kvoten mellan varmvatten- och kallvattenanvändningen i testlägenheterna.
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| 8. |
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| 9. |
- Feng, Kailun, et al.
(author)
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Energy-efficient retrofitting with incomplete building information : a data-driven approach
- 2022
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In: E3S web of conferences. - : EDP Sciences.
-
Conference paper (peer-reviewed)abstract
- The high-performance insulations and energy-efficient HVAC have been widely employed as energy-efficient retrofitting for building renovation. Building performance simulation (BPS) based on physical models is a popular method to estimate expected energy savings for building retrofitting. However, many buildings, especially the older building constructed several decades ago, do not have full access to complete information for a BPS method. To address this challenge, this paper proposes a data-driven approach to support the decision-making of building retrofitting under incomplete information. The data-driven approach is constructed by integrating backpropagation neural networks (BRBNN), fuzzy C-means clustering (FCM), principal component analysis (PCA), and trimmed scores regression (TSR). It is motivated by the available big data sources from real-life building performance datasets to directly model the retrofitting performances without generally missing information, and simultaneously impute the case-specific incomplete information. This empirical study is conducted on real-life buildings in Sweden. The result indicates that the approach can model the performance ranges of energy-efficient retrofitting for family houses with more than 90% confidence. The developed approach provides a tool to predict the performance of individual buildings from different retrofitting measures, enabling supportive decision-making for building owners with inaccessible complete building information, to compare alternative retrofitting measures.
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| 10. |
- Lindh, Magnus, 1960, et al.
(author)
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Real-time Taqman PCR targeting 14 human papilloma virus types.
- 2007
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In: Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology. - : Elsevier BV. - 1386-6532. ; 40:4, s. 321-4
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Subtyping of human papilloma virus (HPV) may enhance the precision of vaginal cytological assessments and will be important for investigating the effect of the recently introduced vaccine against types 16 and 18. OBJECTIVES AND STUDY DESIGN: To evaluate an in-house real-time PCR targeting HPV types 16-18-31-33-35-39-45-51-52-56-58-59-6-11, by analysing 107 liquid-based cytology specimens representing various degrees of dysplasia. RESULTS: In all, 71 samples were HPV positive, with multiple types present in 37 (52%). Comparison with Roche Linear Array on a subset of 24 of these 71 samples showed a good agreement. One or several types were detected in 17/17 (100%) samples with cervical intraepithelial neoplasia grade 2-3 (CIN 2-3), 16/19 (84%) with CIN 1, 32/43 (74%) with Atypical Squamous Cells of Undetermined Significance (ASCUS), and in 6/28 (21%) with benign cytology. Estimates of mean viral load were lower in CIN 1-3 than in ASCUS ( approximately 4000 vs. approximately 25,000 copies/1000 cells), and clearly lower in samples with benign cytology ( approximately 50 copies/1000 cells). CONCLUSION: The HPV rates in groups with different degrees of dysplasia agrees with previous reports and support a strong link between types 16/18 and severe dysplasia. The high rate of multiple type infection might influence the outcome of HPV vaccination. The possible importance of viral load should be further studied.
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| 11. |
- Nydahl, Helena, et al.
(author)
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Building Refurbishment from a Life Cycle Perspective - An Environmental Return on Investment Approach
- 2018
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In: Cold Climate HVAC 2018. - Cham : Springer. - 9783030006617 - 9783030006624 ; , s. 253-263
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Conference paper (peer-reviewed)abstract
- This study applies an environmental return on investment approach to evaluate building refurbishment from a life cycle perspective. The used methodology focuses on the changes introduced by refurbishment, i.e. added embodied environmental impact and changed operational environmental impact, from a life cycle perspective with the technical service life of the refurbishment measure as a time limit. The methodology is applied to a case study in Umeå, located 455 km south of the Arctic Circle, with a unique set of data on reduction in operational energy. The result show the environmental impact, energy (Joule) and GWP (CO2-eq), in terms of environmental return on investment of the case study refurbishment measures. The case study shows that the methodology is a useable approach to compare refurbishment measures from a life cycle perspective. It is possible to use the methodology as a tool at an early stage in planning of sustainable building refurbishment from a life cycle perspective. For a widespread use of a tool based on an environmental return on investment approach, further research on guidelines for sustainable environmental return on investment values is required.
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| 12. |
- Nydahl, Helena, 1990-
(author)
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Communication of life cycle assessment results : life cycle key performance indicators
- 2022
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Doctoral thesis (other academic/artistic)abstract
- The global warming that we are on track for will result in a severe loss of natural capital leading to significant losses in economic capital when urban infrastructure is destroyed, agricultural productivity declines and poverty spread among other disasters. Climate change due to emissions does not only affect the polluter, the hazardous effects becomes evident on a global level. An essential tool to enable decision‑making with concern to the welfare of the global commons is life cycle assessment (LCA). LCA compile and evaluate the inputs, outputs, and potential environmental impacts of a product system throughout its life cycle. The reviewed literature frames a gap regarding interpretation of LCA-results and inquire for guidelines that address a wide range of stakeholders to enable informed decision-making with regard to the welfare of the global commons. Some studies even argue that an apparent weakness of LCA-result communication is the understanding of what the results mean for the economic key performance indicators (KPIs) of the stakeholder. Thus, this thesis aims to contribute to the development of guidelines for interpretation of LCA-results by introducing an approach for communicating LCA-results that is compatible with the economically driven nature of stakeholders. The specific research questions (RQ) of this thesis are: (RQ1) How can well-established economic KPIs be utilised to quantify environmental impact? and (RQ2) How does incorporation of monetary valuation of environmental impacts and related environmental aspects affect the LCA-result and communication of results?These research questions have led to life cycle key performance indicators (LC‑KPIs) that quantify life cycle economic and environmental impacts in a way that take after the traditional economic KPIs of the stakeholders, which is outlined as essential to improve the understanding of LCA-results. The LC‑KPIs utilize the traditional economic KPIs of return on investment (ROI) and annual yield (AY). Additionally, to manage the large amount of non-commensurate units of holistic life cycle sustainability assessment, monetary valuation has been applied. Hence, contributing to the research area of monetary valuation in LCA by introducing and testing new approaches.The introduced LC-KPIs have been specified for building LCA and exemplified by applying them to a number of Swedish case buildings. The result show that the climate-economic assessment of building refurbishment differs compared to the traditional economic assessment when monetary valuation is utilized in LCA with the LC-KPI of ROIEconomy+. However, in the comparative assessment of building refurbishment and new construction, the LCA‑result does not change compared to the traditional economic assessment when monetary valuation is utilized in LCA with the LC-KPI of ELCCA. This is explained by the high costs associated with the investment and energy use of buildings and may not be the case if products with lower investment and energy use costs and high life cycle greenhouse-gas emissions would be studied. Still, if a purely environmental assessment of a product is wished for, the LC-KPI should only include monetary valuation of environmental impact factors and exclude traditional economic performance. Thus, the case study result defines further scope for research on the subject of monetary valuation in LCA and inquire for a wider spectrum of LC-KPIs that utilizes monetary valuation.The introduced approach of this thesis contribute to the development of guidelines for interpretation of LCA-results. Nevertheless, there are still challenges that needs to be addressed in the development of robust LCA-result interpretation. Still, the LC‑KPIs used in this thesis address the “cognitive logics” of a wide range of stakeholders and provide an approach for communication of LCA-results which improve the understanding of LCA-results.
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| 13. |
- Nydahl, Helena, 1990-, et al.
(author)
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Environmental Performance Measures to Assess Building Refurbishment from a Life Cycle Perspective
- 2019
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In: Energies. - : MDPI. - 1996-1073. ; 12:2
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Journal article (peer-reviewed)abstract
- Energy efficiency investments in existing buildings are an effective way of reducing the environmental impact of the building stock. Even though policies in the European Union and elsewhere promote a unilateral focus on operational energy reduction, scientific studies highlight the importance of applying a life cycle perspective to energy refurbishment. However, life cycle assessment is often perceived as being complicated and the results difficult to interpret by the construction sector. There is also a lack of guidelines regarding the sustainable ratio between the embodied and accumulated operational impact. The scope of this study is to introduce a life cycle assessment method for building refurbishment that utilizes familiar economic performance tools, namely return on investment and annual yield. The aim is to use the introduced method to analyze a case building with a sustainability profile. The building was refurbished in order to reduce its operational energy use. The introduced method is compatible with a theory of minimum sustainable environmental performance that may be developed through backcasting from defined energy and GHG emissions objectives. The proposed approach will hopefully allow development of sustainable refurbishment objectives that can support the choice of refurbishment investments.
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| 14. |
- Nydahl, Helena, 1990-, et al.
(author)
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Extended building life cycle cost assessment with the inclusion of monetary evaluation of climate risk and opportunities
- 2022
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In: Sustainable cities and society. - : Elsevier. - 2210-6707. ; 76
-
Journal article (peer-reviewed)abstract
- The buildings and construction sector account for a significant part of the total energy use and related greenhouse gas emissions. However, climate change mitigation often becomes secondary or completely disregarded in building design assessment as the primary concern of building owners are economic tenability. Therefore, this study introduces an Extended Life Cycle Cost Assessment that include monetary evaluation of climate risk and opportunities in terms of Social Cost of Carbon (SCC). SCC could function as a tax to promote climate change mitigation within e.g. the construction industry. The purpose is to provide a more holistic assessment approach that is easy to relate to if economic tenability is of primary concern in decision making, which can be used to assess building design. Return on invested greenhouse gas emissions is used as an additional or standalone indicator for climate change mitigation. The introduced approach is exemplified by a case study where renovation and new construction are compared with keeping buildings in its original design. The case study show that with or without a flat greenhouse gas tax, renovation is the most climate and cost efficient alternative.
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| 15. |
- Nydahl, Helena, 1990-, et al.
(author)
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Including future climate induced cost when assessing building refurbishment performance
- 2019
-
In: Energy and Buildings. - : Elsevier. - 0378-7788 .- 1872-6178. ; 203
-
Journal article (peer-reviewed)abstract
- Improving energy efficiency in the existing buildings stock is essential to limit climate change and the economic assessment of measures are traditionally only based on the reduction of energy costs: However, future financial benefits of limiting climate change are rarely included in the evaluation of refurbishment investments. Although, the costs associated with global warming are expected to be extensive. This study introduces a method for the financial evaluation of energy efficiency investments that merge the reduction of life cycle energy costs with the reduction of future climate induced costs. A case study is used to exemplify the method. The case study shows that when reduced future costs due to mitigated life cycle greenhouse gas emissions are included in the analysis, the ranking between different measures can change and traditionally non-profitable measures may become financially sound investments. The introduced Economy+ indicator is shown to be an accessible performance measure to assess building refurbishment and may also be used in the design stage of new construction. (C) 2019 The Authors. Published by Elsevier B.V.
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| 16. |
- Olofsson, Thomas, 1968-, et al.
(author)
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A method for predicting the annual building heating demand based on limited performance data
- 1998
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In: Energy and Buildings. - : Elsevier. - 0378-7788 .- 1872-6178. ; 28:1, s. 101-108
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Journal article (peer-reviewed)abstract
- In this paper, we present an investigation of the possibility to use a neural network combined with a quasi-physical description in order to predict the annual supplied space heating demand (P) for a number of small single family buildings located in the North of Sweden. As a quasi-physical description for P, we used measured diurnal performance data from a similar building or simulated data from a steady state energy simulation software. We show that the required supplied space heating demand may be predicted with an average accuracy of 5%. The predictions were based on access to measured diurnal data of indoor and outdoor temperatures and the supplied heating demand from a limited time period, ranging from 10 to 35 days. The prediction accuracy was found to be almost independent of what time of the year the measurements were obtained from, except for periods when the supplied heating demand was very small. For models based on measurements from May and fo some buildings from April and September, the prediction was less accurate.
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| 17. |
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| 18. |
- Olofsson, Thomas, 1968-, et al.
(author)
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Energy load predictions for buildings based on a total demand perspective
- 1998
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In: Energy and Buildings. - : Elsevier. - 0378-7788 .- 1872-6178. ; 28:1, s. 109-116
-
Journal article (peer-reviewed)abstract
- The outline of this work was to develop models for single family buildings, based on a total energy demand perspective, i.e., building-climate-inhabitants. The building-climate part was included by using a commercial dynamic energy simulation software. Whereas the influence from the inhabitants was implemented in terms of a predicted load for domestic equipment and hot water preparation, based on a reference building. The estimations were processed with neural network techniques. All models were based on access to measured diurnal data from a limited time period, ranging from 10 to 35 days. The annual energy predictions were found to be improved, compared to models based on only a building-climate perspective, when the domestic load was included. For periods with a small heating demand, i.e., May-September, the average accuracy was 7% and 4% for the heating and total energy load, respectively, whereas for the rest of the year the accuracy was on average 3% for both heating and total energy load.
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| 19. |
- Olofsson, Thomas, 1968-, et al.
(author)
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Energy Performance for Buildings Evaluated with Multivariate Analysis
- 2005
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In: Proceedings of the of the Ninth IBPSA Conference and Exhibition, Building Simulation 2005. ; , s. 891-898
-
Conference paper (peer-reviewed)abstract
- Numerous problems can occur for an investigatorof larger datasets, e.g. how to handledimensionality, many variables and fewobservations, few variables and many observations,correlations, missing data, noise and to extractinformation from all data simultaneously.Multivariate analysis (MVA) is an establishedmethod for dealing with such problems.In this work, we introduce a methodology based onMVA, which was developed to model the buildingenergy performance from the perspective of theproperty holder. Data from a Swedish database of500 buildings, which recently has been compiledand is under expansion, was used for theinvestigation. The available data consists ofbuilding specific information and consumptiondata, monitored on a monthly basis, reported by theproperty holder. Electrical consumption for lightingand appliances is paid by the tenants in Sweden,and is thus lacking in the database. This means thatthe data base just include the part of the total energyuse that is paid by the property holder. With theoverall goal to assess the energy use paid by theproperty holders, a methodology is suggested forestimating the electrical energy paid by the tenants.At this early stage of our work, we found that theused methodology gives a fairly robust model andthat the interpretation of the model is believed to beaccurate in terms of comparing the energy usebetween different buildings.
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| 20. |
- Olofsson, Thomas, 1968-, et al.
(author)
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Long term energy demand predictions for buildings based on short-term measured data
- 2001
-
In: Energy and Buildings. - 0378-7788 .- 1872-6178. ; 33:2, s. 85-91
-
Journal article (peer-reviewed)abstract
- In order to obtain long-term predictions based on short-term data, a neural network model was developed. The model parameters are indoor and outdoor temperature difference and energy for heating and internal use. For purposes of training the neural network model a method for extending the measured data to represent an annual variation is proposed. The method has been applied on six single-family buildings. Based on access to data from 2 to 5 weeks, the deviation between predicted and measured diurnal energy demand on an annual basis was about 4% with a correlation of 90–95%, when access to the indoor and outdoor temperature difference was assumed. For models based on access to data from the warmest periods with a very small heating demand, the deviation was about 2–4 times larger.
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| 21. |
- Olofsson, Thomas, 1968-, et al.
(author)
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Multivariate Methods for Evaluating Building Energy Efficiency
- 2004
-
In: Proceedings of the 2004 ACEEE Summer Study of Energy Efficiency in Buildings. - 0918249538 ; , s. 265-274
-
Conference paper (peer-reviewed)abstract
- For an owner or operator of a building, benchmarking can be a useful guide for finding outhow energy efficient the building is and identifying what to improve. For successfulevaluation of the building energy efficiency, the categorization as well as the parameteridentification has decisive importance. That selection can be based on mathematical modelingsuch as linear regression accompanied with more or less user expert knowledge. Theselection, however, is not a simple task since analyses based on statistical data are sensitive tocorrelations between different measured parameters. For improving that analysis multivariatemethods such as Principal Component Analysis (PCA) can be a valuable support.We demonstrate here how PCA can be a useful tool for investigating aggregated statisticaldatasets. The investigation illustrates how a set of building performance parameters exhibitsdifferent relations depending on how the categorization is made, which is relevant to considerwhen benchmarking. The study is based on a national Swedish database of aggregated energyuse and building performance statistics.
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| 22. |
- Olofsson, Thomas, 1968-, et al.
(author)
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Overall heat loss coefficient and domestic energy gain factor for single family buildings
- 2002
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In: Energy and Buildings. - 0378-7788 .- 1872-6178. ; 37:11, s. 1019-1026
-
Journal article (peer-reviewed)abstract
- In this work we introduce a method for estimating the variation of the overall heat loss coe"cient and the domestic energy gain factor. Based on a neural network model, these parameters were extracted from analyzing the model by indirect methods. The used model parameters were: the supplied heating demand, the domestic electrical demand and the indoor–outdoor temperature di5erence. A feed-forward back propagation neural network was used as modeling tool. The proposed method has been found accurate, based on an analysis of arti6cially generated data. Additionally, measured data of inhabited single family buildings were examined and the model was found to generate reliable results, in parity with results obtained by comparable methods and estimations.
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| 23. |
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| 24. |
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| 25. |
- Puttige, Anjan Rao, 1990-, et al.
(author)
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A Novel Analytical-ANN Hybrid Model for Borehole Heat Exchanger
- 2020
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In: Energies. - : MDPI. - 1996-1073. ; 13:23
-
Journal article (peer-reviewed)abstract
- Optimizing the operation of ground source heat pumps requires simulation of both short-term and long-term response of the borehole heat exchanger. However, the current physical and neural network based models are not suited to handle the large range of time scales, especially for large borehole fields. In this study, we present a hybrid model for long-term simulation of BHE with high resolution in time. The model uses an analytical model with low time resolution to guide an artificial neural network model with high time resolution. We trained, tuned, and tested the hybrid model using measured data from a ground source heat pump in real operation. The performance of the hybrid model is compared with an analytical model, a calibrated analytical model, and three different types of neural network models. The hybrid model has a relative RMSE of 6% for the testing period compared to 22%, 14%, and 12% respectively for the analytical model, the calibrated analytical model, and the best of the three investigated neural network models. The hybrid model also has a reasonable computational time and was also found to be robust with regard to the model parameters used by the analytical model.
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| 26. |
- Puttige, Anjan Rao, 1990-, et al.
(author)
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Application of Regression and ANN Models for Heat Pumps with Field Measurements
- 2021
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In: Energies. - : MDPI. - 1996-1073. ; 14:6
-
Journal article (peer-reviewed)abstract
- Developing accurate models is necessary to optimize the operation of heating systems. A large number of field measurements from monitored heat pumps have made it possible to evaluate different heat pump models and improve their accuracy. This study used measured data from a heating system consisting of three heat pumps to compare five regression and two artificial neural network (ANN) models. The models’ performance was compared to determine which model was suitable during the design and operation stage by calibrating them using data provided by the manufacturer and the measured data. A method to refine the ANN model was also presented. The results indicate that simple regression models are more suitable when only manufacturers’ data are available, while ANN models are more suited to utilize a large amount of measured data. The method to refine the ANN model is effective at increasing the accuracy of the model. The refined models have a relative root mean square error (RMSE) of less than 5%
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| 27. |
- Puttige, Anjan Rao, 1990-, et al.
(author)
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Improvement of borehole heat exchanger model performance by calibration using measured data
- 2020
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In: Journal of Building Performance Simulation, Taylor & Francis. - : Taylor & Francis. - 1940-1493 .- 1940-1507. ; 13:4, s. 430-442
-
Journal article (peer-reviewed)abstract
- Planning the operation of large ground source heat pump (GSHP) systems requires accurate models of borehole heat exchangers (BHEs) that are not computationally intensive. In this paper, we propose parameter estimation using measured data as a method to improve the analytical models of BHE. The method was applied to a GSHP system operating for over 3 years. The deviation between modelled and measured load of the BHE reduced from 22% to 14%. Influence of the calibration data set was tested by changing time resolution and season of the calibration data. We concluded that the time resolution must be high enough to differentiate among the effects of different parameters and that different model parameters must be used for injection and extraction (seasons). The method was also applied to a GSHP that has been monitored for 10 years, which showed that accuracy of the model can be improved by annual updates of parameters.
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| 28. |
- Puttige, Anjan Rao, 1990-, et al.
(author)
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Method to estimate the ground loads for missing periods in a monitored GSHP
- 2019
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In: EUROPEAN GEOTHERMAL CONGRESS 2019.
-
Conference paper (other academic/artistic)abstract
- Monitoring a ground source heat pump can provide important insights into its working, but to study the behaviour of the borehole heat exchanger (BHE) we require monitored data for the whole period of operation. In practice, the monitored data often has periods of missing data. We propose a method to estimate the load during the periods of missing data based on the fluid temperature after that period. The method determined the missing load with negligible error, for the case of a BHE that behaves exactly like the model describing it. A sensitivity analysis showed that the estimated load is highly sensitive to errors in measured load and fluid temperature. The method was applied to a real monitored BHE, the magnitude of estimated loads were unreasonably high, but the overall deviation between the measured and simulated values of fluid temperature decreased. Therefore, the high magnitude of missing load compensates for the lack of agreement between the model and the measured data.
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| 29. |
- Puttige, Anjan Rao, 1990-, et al.
(author)
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Modeling and optimization of hybrid ground source heat pump with district heating and cooling
- 2022
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In: Energy and Buildings. - : Elsevier. - 0378-7788 .- 1872-6178. ; 264
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Journal article (peer-reviewed)abstract
- Hybrid heating systems with ground source heat pumps (GSHP) and district heating and cooling offer flexibility in operation to both building owners and energy providers. The flexibility can be used to make the heating system more economical and environmentally friendly. However, due to the lack of suitable models that can accurately predict the long-term performance of the GSHP, there is uncertainty in their performance and concerns about the long-term stability of the ground temperature, which has limited the utilization of such hybrid heating systems. This work presents a hybrid model of a GSHP system that uses analytical and artificial neural network models to accurately represent a GSHP system's long-term behavior. A method to improve the operation of a hybrid GSHP is also presented. The method was applied to hospital buildings in northern Sweden. It was shown that in the improved case, the cost of providing heating to the building can be reduced by 64 t€, and the CO2 emissions can be reduced by 92 tons while maintaining a stable ground temperature.
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| 30. |
- Puttige, Anjan Rao, 1990-
(author)
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Utilization of a GSHP System in a DHC Network : modeling and optimization
- 2021
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Doctoral thesis (other academic/artistic)abstract
- The ground source heat pumps (GSHPs) of customers connected to the district heating and cooling (DHC) network can benefit both the customer and the energy company. However, operating the GSHP to minimize the cost of providing heating and cooling to the customer while ensuring the long-term stability of the ground temperature is a challenge. This thesis addresses the challenge by developing accurate models of GSHP and optimizing the operation of the GSHP system using these models.The models presented in this thesis use field measurements to develop accurate models with low computational time. The main components of a GSHP system are the heat pump and the borehole heat exchanger (BHE). This thesis presents two approaches to use measured data to improve the accuracy of analytical models for BHE. The first approach is the calibration of the model parameters using this measured data. The second approach combines the analytical model with an artificial neural network model resulting in a hybrid model. The calibration approach reduced the relative RMSE of the analytical model from 21.9% to 13.9% in the testing period. The relative RMSE of the hybrid model for the testing period was 6.3%.We compared different data-driven models for heat pumps and determined that artificial neural network models have an advantage over traditional regression models when field measurements are available. The artificial neural network model was refined to better utilize the measured data. The refined models of heat pumps had a relative RMSE of less than 5%.The hybrid BHE model and an artificial neural network model for the heat pumps were used to model the GSHP system. The model was validated using four years of field measurements. The relative MAE for the compressor power and BHE power were 7.3% and 19.1% respectively.The validated model was used to optimize the operation of the GSHP system. In optimal operation, the cost of providing heating and cooling to the area was minimized from the perspective of the energy company while maintaining a stable temperature in the ground. In optimal operation, the annual cost of operation was shown to reduce by 64 t€ and the annual CO2 emission was shown to reduce by 92 tons.
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| 31. |
- Vesterberg, Jimmy, 1976-, et al.
(author)
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A single-variate building energy signature approach for periods with substantial solar gain
- 2016
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In: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 122, s. 185-191
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Journal article (peer-reviewed)abstract
- The use of regression analysis for the identification of building performance parameters based on measurements is often difficult due to collinearity between the outdoor temperature and the global solar radiation (S). This study proposes a method to overcome this issue. The proposed method is based on using the seasonal symmetry of S to pair data from time-periods equidistant from the winter solstice. In addition, a method to utilize synthetic data to fine-tune the paired-data approach is presented. To evaluate the paired-data approach, two years data from a multifamily building in Umeå was used to estimate the heat loss factor (air-to-air transmission including air leakage). The results were compared with results obtained when S was very low (S ≈ 0). It was found that, the fine-tuned paired-data approach resulted in a modest deviation in the heat loss factor with an average absolute deviation of 4.0%. The small deviation indicates that the paired-data approach can extend the use of single-variate regression models for accurate identification of heat loss factors to situations where the solar gain is substantial. The paired-data approach was also used to calibrate a commercial energy building simulation tool.
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| 32. |
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