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Bales, Chris
Publications (10 of 48) Show all publications
Sandström, M., Huang, P., Bales, C. & Dotzauer, E. (2023). Evaluation of hosting capacity of the power grid for electric vehicles – A case study in a Swedish residential area. Energy, 284, Article ID 129293.
Open this publication in new window or tab >>Evaluation of hosting capacity of the power grid for electric vehicles – A case study in a Swedish residential area
2023 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 284, article id 129293Article in journal (Refereed) Published
Abstract [en]

The deployment of electric vehicles (EVs) is growing significantly in recent years. The increasing EV charging loads pose great stress on power grids in Sweden, as many existing power grids are not designed to host such large shares of new electric loads. Hence, studies investigating the impact of EV charging are needed. This study conducts a case study based on an existing Swedish residential power grid using real-life EV charging data to estimate the local grid hosting capacity (HC) for EVs. A combined time-series and stochastic HC assessment method is used with voltage deviation, cable loading and transformer loading as the performance indices. Uncertainty in EV charging locations and individual charging behaviour have been considered via Monte Carlo simulations. The power grid HC is analysed and compared under three charging strategies and four EV penetration levels. Study results show that a charging strategy based on low electricity prices gave lower HC due to simultaneous EV loads compared to the other two strategies: charging directly after plugging in the EV and an even charging load through the plug-in session. This implies the need for coordinated charging controls of EV fleets or diversified power tariffs to balance power on a large scale. © 2023 The Authors

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Charging strategies, Electric vehicle (EV), Hosting capacity (HC), Power grid, Uncertainty analysis, Charging (batteries), Electric loads, Electric vehicles, Housing, Intelligent systems, Monte Carlo methods, Stochastic systems, Vehicle-to-grid, Case-studies, Charging loads, Electric vehicle, Electric vehicle charging, Hosting capacity, Power grids, Residential areas, Swedishs
National Category
Energy Systems
Identifiers
urn:nbn:se:du-47227 (URN)10.1016/j.energy.2023.129293 (DOI)001096442000001 ()2-s2.0-85174838805 (Scopus ID)
Available from: 2023-11-07 Created: 2023-11-07 Last updated: 2023-12-07Bibliographically approved
Rynoson, M., Bales, C. & Munkhammar, J. (2023). PV modeling in IDA ICE (5.0 beta): Perfomance analysis based on measured data in high latitudes. In: Proceedings of the 40th European Photovoltaic Solar Energy Conference and Exhibition in Lisbon, Portugal: . Paper presented at EU PVSEC 2023, Lisbon. München: WIP
Open this publication in new window or tab >>PV modeling in IDA ICE (5.0 beta): Perfomance analysis based on measured data in high latitudes
2023 (English)In: Proceedings of the 40th European Photovoltaic Solar Energy Conference and Exhibition in Lisbon, Portugal, München: WIP, 2023, , p. 6Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

In recent years, the widespread adoption of photovoltaic (PV) installations across various sectors has created a growing demand for accurate PV design tools. In this pursuit, the latest version of IDA Indoor Climate and Energy (IDA ICE 5 beta) emerges as a contender, offering advanced PV modeling capabilities, together with the advanced building simulation capabilities it already has. This study evaluates the accuracy of PV modeling within IDA ICE by comparing predicted power outputs to real-world data from three existing PV systems located at the Research Institute of Sweden (RISE) in Borås. To achieve this, weather files are created using historical weather and radiation data. As the measured radiation data is only available as total irradiation on a tilted plane, it was deconstructed into direct and diffuse components on the horizontal plane using a modified version of the model by Erbs et al.. Additional known parameters are the geometry of the PV array, and the characteristics of PV panel and inverter, based on their product data sheets. The accuracy of the PV design tool in IDA ICE is evaluated by comparing the power output of unshaded arrays against the measured data from RISE. The calculated power output is compared to the measured power output and analyzed through ASHRAE 14-2014 guidelines for performance evaluation. It was found that the software gives an accurate prediction of both panel temperature and PV power production. A study on shading effects is an open problem to improve the generality of the results in this study.

Place, publisher, year, edition, pages
München: WIP, 2023. p. 6
Keywords
PV Array, PV Modeling, Renewable Energy Planning, IDA ICE, Building Energy Simulation
National Category
Energy Systems
Identifiers
urn:nbn:se:du-47506 (URN)10.4229/EUPVSEC2023/4DV.4.48 (DOI)3-936338-88-4 (ISBN)
Conference
EU PVSEC 2023, Lisbon
Funder
SOLVE, 52693-1
Available from: 2023-12-18 Created: 2023-12-18 Last updated: 2023-12-18Bibliographically approved
Zhang, F., Fleyeh, H. & Bales, C. (2022). A hybrid model based on bidirectional long short-term memory neural network and Catboost for short-term electricity spot price forecasting. Journal of the Operational Research Society, 73(2), 301-325
Open this publication in new window or tab >>A hybrid model based on bidirectional long short-term memory neural network and Catboost for short-term electricity spot price forecasting
2022 (English)In: Journal of the Operational Research Society, ISSN 0160-5682, E-ISSN 1476-9360, Vol. 73, no 2, p. 301-325Article in journal (Refereed) Published
National Category
Energy Engineering
Identifiers
urn:nbn:se:du-35574 (URN)10.1080/01605682.2020.1843976 (DOI)000596991400001 ()2-s2.0-85096954531 (Scopus ID)
Available from: 2020-12-07 Created: 2020-12-07 Last updated: 2023-03-16
Andersen, M., Bales, C. & Dalenbäck, J.-O. -. (2022). Economic Analysis of Heat Distribution Concepts for a Small Solar District Heating System. Energies, 15(13), Article ID 4737.
Open this publication in new window or tab >>Economic Analysis of Heat Distribution Concepts for a Small Solar District Heating System
2022 (English)In: Energies, E-ISSN 1996-1073, Vol. 15, no 13, article id 4737Article in journal (Refereed) Published
Abstract [en]

One challenge in today’s district heating systems is the relatively high distribution heat loss. Lowering distribution temperatures is one way to reduce operational costs resulting from high heat losses, while changing the distribution system from steel pipes to plastic pipes and changing the heat distribution concept can reduce investment costs. The result is that the overall life cycle cost of the district heating system is reduced, leading to the improved cost competitiveness of district heating versus individual heating options. The main aim of this study was to determine the most cost-efficient distribution system for a theoretical solar district heating system, by comparing the marginal life cycle cost of two different distribution systems. A secondary aim was to determine the influence of the employed pipe type and insulation level on the marginal life cycle cost by comparing detailed economic calculations, including differences in pipe installation costs and construction costs, among others. A small solar-assisted district heating system has been modeled in TRNSYS based on a real system, and this “hybrid” model is used as a basis for a second model where a novel distribution system is employed and the heating network operating temperature is changed. Results indicate that a novel distribution concept with lower network temperatures and central domestic hot water preparation is most efficient both from an energy and cost perspective. The total life cycle costs vary less than 2% for a given distribution concept when using different pipe types and insulation classes, indicating that the investment costs are more significant than operational costs in reducing life cycle costs. The largest difference in life cycle cost is observed by changing the distribution concept, the novel concept having approximately 24% lower marginal life cycle cost than the “hybrid” system. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Place, publisher, year, edition, pages
MDPI, 2022
Keywords
Cost reduction, District heating, Economic analysis, Heat losses, Heating equipment, Hot water distribution systems, Investments, Water, 4GDH, Distribution systems, District heat, District heating system, GRUDIS, Hot water, Hot water circulation, Solar thermal, TRNSYS, Water circulation, Life cycle
National Category
Energy Engineering
Identifiers
urn:nbn:se:du-42151 (URN)10.3390/en15134737 (DOI)000824395100001 ()2-s2.0-85133513099 (Scopus ID)
Available from: 2022-08-16 Created: 2022-08-16 Last updated: 2023-08-28
Shantia, A., Streicher, W. & Bales, C. (2022). Effect of tapered headers on pressure drop and flow distribution in a U-type polymeric solar absorber. Renewable energy, 192, 550-560
Open this publication in new window or tab >>Effect of tapered headers on pressure drop and flow distribution in a U-type polymeric solar absorber
2022 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 192, p. 550-560Article in journal (Refereed) Published
Abstract [en]

This study inspects the effect of tapered headers on pressure drop and flow distribution in a U-type polymeric absorber with novel tapered headers and lens-shaped absorber strings using a validated thermo-hydraulic model. The model results are compared with those obtained from the literature to attain credibility in the flow distribution trend for the U-configuration. A good agreement between the developed discrete model and comparison cases is found. Moreover, in order to examine the efficacy of tapered headers in more detail, different scenarios are treated in terms of header configuration by applying cylindrical geometry in one or both inlet/outlet headers. The outcomes exemplify that even a slight cone angle of 1.73 degrees in headers can significantly reduce non-uniformity (phi(max) < 8%) with negligible influence on the total pressured drop. Yet, further reduction in maldistribution (phi(max) < 5%) can be achieved in U-type absorbers if the tapered outlet header is combined with a cylindrical inlet header in the range of AR <= 3.34 and DR <= 0.24. In this case, a compromise between additional pressure drop and flow distribution degree should be found. The present study offers a systematic approach for conducting thermo-hydraulic analysis in flat-plate solar collectors with complex absorber compositions and geometries. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Keywords
Flat-plate solar collector, U-type solar absorber, Pressure drop, Flow distribution, Discrete model, Thermo-hydraulic model
National Category
Energy Systems
Identifiers
urn:nbn:se:du-42082 (URN)10.1016/j.renene.2022.04.042 (DOI)000804982200007 ()2-s2.0-85129551228 (Scopus ID)
Available from: 2022-08-09 Created: 2022-08-09 Last updated: 2023-03-17Bibliographically approved
Shantia, A., Streicher, W. & Bales, C. (2022). Effect of tapered headers on pressure drop and flow distribution in a Z-type polymeric solar absorber. Solar Energy, 232, 283-297
Open this publication in new window or tab >>Effect of tapered headers on pressure drop and flow distribution in a Z-type polymeric solar absorber
2022 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 232, p. 283-297Article in journal (Refereed) Published
Abstract [en]

This work presents a discrete model for the thermo-hydraulic analysis of a novel polymeric solar thermal absorber with tapered headers and lens-shaped absorber strings. The numerical model developed is based on empirical correlations for laminar and turbulent flow regimes. The principal aim of this study is to ascertain if tapered headers help improve flow distribution in parallel-flow absorbers under laminar and turbulent flow conditions. In order to verify the model, the simulation results are compared to the measurement for total pressure drop and two studies from the previous literature for flow distribution. Altogether, a good agreement is found in all comparison cases, and the proposed numerical algorithm is proven to be robust and stable for complex thermo-hydraulic analysis. The results are then elaborated by comparing the tapered case to several conventional cases with cylindrical headers but with identical riser configurations to the original model. The results indicate that using tapered headers in compact absorbers with relatively large area ratios can noticeably reduce non-uniformity, especially up to middle range flows, by maintaining higher Reynolds numbers in the headers. The developed model can be used to optimize the hydraulic design of solar collectors with complex geometries and large area ratios. © 2022 The Authors

Keywords
Discrete model, Flat-plate solar collector, Flow distribution, Pressure drop, Thermo-hydraulic model, Z-type solar absorber, Drops, Hydraulic models, Parallel flow, Reynolds number, Solar absorbers, Solar collectors, Turbulent flow, Discrete models, Drop distribution, Flat-plate solar collectors, Laminar and turbulent flow, Large area ratio, Solar thermal absorbers, Thermo-hydraulics analysis
National Category
Energy Engineering
Identifiers
urn:nbn:se:du-39330 (URN)10.1016/j.solener.2021.11.048 (DOI)000768764000008 ()2-s2.0-85122507335 (Scopus ID)
Available from: 2022-01-17 Created: 2022-01-17 Last updated: 2023-04-14Bibliographically approved
Andersen, M., Bales, C. & Dalenbäck, J.-O. (2022). Heat distribution concepts for small solar district heating systems – Techno-economic study for low line heat densities. Energy Conversion and Management: X, 15, Article ID 100243.
Open this publication in new window or tab >>Heat distribution concepts for small solar district heating systems – Techno-economic study for low line heat densities
2022 (English)In: Energy Conversion and Management: X, ISSN 2590-1745, Vol. 15, article id 100243Article in journal (Refereed) Published
Abstract [en]

The high operating temperatures in today’s district heating networks combined with the low energy demand of new buildings lead to high relative network heat losses. New networks featuring lower operating temperatures have reduced relative heat losses while enabling an increase in the use of solar heat. The primary aim of this study was to determine if a particular district heating system can be made more effective with respect to heat losses and useful solar energy, by considering different distribution concepts and load densities. A small solar assisted district heating system with a novel hybrid distribution system has been modelled based on a real case study. This model serves as a basis for two other models where the distribution system and heating network operating temperature is changed. A secondary aim of the study was to determine the economic implications of making these changes, by using costs estimates to calculate the contribution of essential system components to total system cost. Results indicate that a novel distribution concept with lower network temperatures and central domestic hot water preparation is most energy efficient in a sparse network with a heat density of 0.2 MWh/m∙a and a performance ratio of 66%, while a conventional district heating system performs worst and has a performance ratio of less than 58% at the same heat density. In an extremely sparse network with heat density of 0.05 MWh/m∙a, the performance ratio is 41% and 30% for these systems, respectively. A simple economic analysis indicates that the novel distribution concept is also best from an economic point of view, reducing the initial investment cost by 1/3 compared to the conventional concept, which is the most costly. However, more detailed calculations are needed to conclude on this.

Keywords
4GDH, Solar thermal, District heat, Hot water circulation, GRUDIS, TRNSYS
National Category
Building Technologies
Research subject
Energy and Built Environments, SHINE
Identifiers
urn:nbn:se:du-41759 (URN)10.1016/j.ecmx.2022.100243 (DOI)2-s2.0-85132220381 (Scopus ID)
Available from: 2022-06-27 Created: 2022-06-27 Last updated: 2023-03-17Bibliographically approved
Sandström, M., Bales, C. & Dotzauer, E. (2022). Hosting Capacity of the Power Grid for Electric Vehicles - A Case Study on a Swedish Low Voltage Grid. In: IOP Conference Series: Earth and Environmental Science. Paper presented at 7th International Conference on Sustainable and Renewable Energy Engineering, ICSREE 2022Virtual, Online, 5 May 2022 through 7 May 2022. Institute of Physics (1)
Open this publication in new window or tab >>Hosting Capacity of the Power Grid for Electric Vehicles - A Case Study on a Swedish Low Voltage Grid
2022 (English)In: IOP Conference Series: Earth and Environmental Science, Institute of Physics , 2022, no 1Conference paper, Published paper (Refereed)
Abstract [en]

Hosting capacity (HC) is described as the maximum amount of new production or consumption that can be added to the grid without causing a violation. In this case study, a deterministic approach is used to investigate the HC of electric vehicle (EV) charging in a low-voltage grid, containing 13 detached single-family houses. It investigates how different parameters affect the HC, and what is causing the violation in the grid. Two different performance indices (PI) are used in the study: power cable overloading and voltage drop. The local grid is simulated for one year for four cases and the HC is derived for these. The cases are distinguished by two different violation thresholds for the voltage drop and two different implementation orders of the location of the charging. The results show that the HC of the grid is 6-11 EVs charging simultaneously. The difference in HC is primarily due to variation in the baseload through the year and location of charging. The cable between the substation and the first cable cabinet was the major contributor to the fault, and the PI causing the violation differed depending on what case was used. © Published under licence by IOP Publishing Ltd.

Place, publisher, year, edition, pages
Institute of Physics, 2022
National Category
Energy Systems
Identifiers
urn:nbn:se:du-42169 (URN)10.1088/1755-1315/1050/1/012008 (DOI)2-s2.0-85134688555 (Scopus ID)
Conference
7th International Conference on Sustainable and Renewable Energy Engineering, ICSREE 2022Virtual, Online, 5 May 2022 through 7 May 2022
Available from: 2022-08-17 Created: 2022-08-17 Last updated: 2023-03-17Bibliographically approved
Zhang, F., Bales, C. & Fleyeh, H. (2021). Feature Augmentation of Classifiers Using Learning Time Series Shapelets Transformation for Night Setback Classification of District Heating Substations. Advances in Civil Engineering / Hindawi, 2021, Article ID 8887328.
Open this publication in new window or tab >>Feature Augmentation of Classifiers Using Learning Time Series Shapelets Transformation for Night Setback Classification of District Heating Substations
2021 (English)In: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, Vol. 2021, article id 8887328Article in journal (Refereed) Published
National Category
Computer Sciences Energy Engineering
Identifiers
urn:nbn:se:du-36774 (URN)10.1155/2021/8887328 (DOI)000629368200002 ()2-s2.0-85102779915 (Scopus ID)
Available from: 2021-05-05 Created: 2021-05-05 Last updated: 2023-04-14Bibliographically approved
Zhang, F., Bales, C. & Fleyeh, H. (2021). From time series to image analysis: A transfer learning approach for night setback identification of district heating substations. Journal of Building Engineering, 43, Article ID 102537.
Open this publication in new window or tab >>From time series to image analysis: A transfer learning approach for night setback identification of district heating substations
2021 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 43, article id 102537Article in journal (Refereed) Published
National Category
Energy Systems
Identifiers
urn:nbn:se:du-37271 (URN)10.1016/j.jobe.2021.102537 (DOI)000697043900001 ()2-s2.0-85105692294 (Scopus ID)
Available from: 2021-06-03 Created: 2021-06-03 Last updated: 2023-04-14Bibliographically approved
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