| 1. |
- Petrovic, Bojana, et al.
(författare)
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Life cycle assessment of a wooden single-family house in Sweden
- 2019
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 251, s. 1456-1465
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Tidskriftsartikel (refereegranskat)abstract
- To understand the reasons behind the large environmental impact from buildings the whole life cycle needs to be considered. Therefore, this study evaluates the carbon dioxide emissions in all stages of a single-family house in Sweden from the production of building materials, followed by construction and user stages until the end-of-life of the building in a life cycle assessment (LCA). The methodology applied is attributional life cycle assessment (LCA) based on `One Click LCA' tool and a calculated life span of 100 years. Global warming potential (GWP) and primary energy (PE) are calculated by using specific data from the case study, furthermore the data regarding building materials are based on Environmental Product Declarations (EPDs). The results show that the selection of wood-based materials has a significantly lower impact on the carbon dioxide emissions in comparison with non-wood based materials. The total emissions for this single-family house in Sweden are 6 kg CO2e/m2/year. The production stage of building materials, including building systems and installations represent 30% of the total carbon dioxide equivalent emissions, while the maintenance and replacement part represents 37%. However, energy use during the in-use stage of the house recorded lower environmental impact (21%) due to the Swedish electricity mix that is mostly based on energy sources with low carbon dioxide emissions. The water consumption, construction and the end-of-life stages have shown minor contribution to the buildings total greenhouse gas (GHG) emissions (12%). The primary energy indicator shows the largest share in the operational phase of the house.
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| 2. |
- Petrovic, Bojana, et al.
(författare)
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Life cycle assessment of building materials for a single-family house in Sweden
- 2019
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Ingår i: Energy Procedia. - : Elsevier. - 1876-6102. ; 158, s. 3547-3552
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Tidskriftsartikel (refereegranskat)abstract
- The Nordic countries have shown great interest in using Life Cycle Assessment (LCA) in the building sector compared to the past years. Sweden has set up an objective to be carbon neutral (no greenhouse gas emissions to the atmosphere) by 2045. This paper presents a case study of a single-family house "Dalarnas Villa" in the region Dalarna, Sweden within a 100-year perspective. The assessment is implemented using a new software based on hard data agreed by Environmental Product Declarations (EPDs). It focuses on building materials, transport distances of the materials, and replacement of essential construction materials. The LCA in this study demonstrates the environmental impact related to building materials from production and construction phase including transport, replacement and deconstruction phase. The study does not cover energy use and water consumption. The results show that the building slab made by concrete is the part of the construction most contributing to CO2e, while the wood frame and cellulose insulation have low environmental impact. Replacement of materials takes nearly half of total environmental impact over 100 years. Having a large share of wood-based products, make greenhouse gas emissions remains low. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy.
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| 3. |
- Eriksson, Ola, 1979-, et al.
(författare)
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Impact of Wind Veer and the Coriolis Force for an Idealized Farm to Farm Interaction Case
- 2019
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the Coriolis force on the long distance wake behind wind farms is investigated using Large Eddy Simulations (LES) combined with a Forced Boundary Layer (FBL) technique. When using the FBL technique any mean wind shear and turbulent fluctuations can be added with body forces. The wind shear can also include the mean wind veer due to the Coriolis force. The variation of the Coriolis force due to local deviations from the mean profile, e.g., from wakes, is not taken into account in the FBL. This can be corrected for with an extra source term in the equations, hereon defined as the Coriolis correction. For a row of 4 turbines it is shown that the inclusion of the wind veer turns the wake to the right, while including the Coriolis correction turns it to the left. When including both wind veer and Coriolis correction the impact of wind veer dominates. For an idealized farm to farm interaction case, two farms of 4 * 4 turbines with 6 km in between, it can be seen that when including wind veer and the Coriolis correction a approximately 3% increase in the relative production for a full wake direction can be seen and only a slightly smaller increase can be seen when including only wind veer. The results indicate that FBL can be used for studies of long distance wakes without including a Coriolis correction but efforts need to be taken to use a wind shear with a correct mean wind veer.
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| 4. |
- Eriksson, Ola, 1979-, et al.
(författare)
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Large-eddy simulations of the evolution of imposed turbulence in forced boundary layers in a very long domain
- 2020
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Ingår i: Wind Energy. - : Wiley. - 1095-4244 .- 1099-1824. ; 23:6, s. 1482-1493
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Tidskriftsartikel (refereegranskat)abstract
- The technique of using imposed turbulence in combination with a forced boundary layer in order to model the atmospheric boundary layer is analyzed for a very long domain using large-eddy simulations with different combinations of prescribed velocity profiles and pregenerated turbulence fields based on the Mann model. The ambient flow is first studied in the absence of wind turbines. The velocity profiles undergo a transition throughout the domain with a velocity increase of 10% to 15% close to the ground far downstream in the domain. The turbulence characteristics close to the turbulence plane are, as expected, similar to those of the added Mann turbulence. The turbulence will then undergo a transition throughout the domain to finally reach a balance with the shear profile at a certain downstream distance. This distance is found to depend on the turbulence level of the added Mann turbulence planes. A lower Mann turbulence level generally results in a shorter "balancing" distance. Secondly, a row of 10 turbines is imposed in the simulations at different distances from the plane of turbulence in order to determine how the distance affects wake conditions and power production levels. Our results show that a "balancing" distance is needed between the turbulence plane and the first turbine in the row in order to ensure nonchanging ambient conditions throughout the turbine row. This introduces an increase in the computational costs. The computational cost for the forced boundary technique is normally lower compared with using precursor simulations, for longer domains; however, this needs to be verified further.
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| 5. |
- Eriksson, Ola, 1979-
(författare)
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Numerical Computations of Wakes Behind Wind Farms : A tool to study Farm to Farm interaction
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- More and larger wind farms are planned offshore. As the most suitable sites to build are limited these new wind farms will be constructed near to each other in so called wind farm clusters. Behind the wind turbines in these farms there is a disrupted flow of air called a wake that is characterized by reduced wind speed and increased turbulence. These individual turbine wakes combine to form a farm wake that can travel long distances. In wind farm clusters farm to farm interaction will occur, i.e. the long distance wake from one wind farm will impact the wind conditions for other farms in the surrounding area.This thesis contains numerical studies of these long distance wakes. In these studies Large Eddy Simulations (LES) using an Actuator Disc method (ACD) are used. A prescribed boundary layer is used where the wind shear is introduced using body forces. The turbulence, based on the Mann model, is introduced as fluctuating body forces upstream of the farm. A neutral atmosphere is assumed. The applied method has earlier been used for studies of wake effects inside farms but not for the longer distances needed for the study of farm to farm interaction. Parameter studies are setup to analyze how to best use the model for the study of long distance wakes with regards to 1) numerical and physical parameters in the model, 2) the extension of the domain and turbulence as well as the characteristics of the flow far downstream and 3) the downstream development of turbulence with different combinations of wind shear and turbulence level.Using an initial simulation setup a wind farm was studied and preliminary results were obtained. These results were subsequently improved upon by applying the simulation setup adjustments indicated in the parameter studies. A comparison with a mesoscale model was also done. The mesoscale model was shown to be relevant for studies of long distance wakes in another study comparing LES and WRF. Finally an idealized farm to farm interaction case was studied with focus on the impact of including the Coriolis force in the simulations.Combining LES with a mesoscale model is of interest to study further.
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| 6. |
- Eriksson, Ola, 1979-
(författare)
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Numerical Computations of Wakes Behind Wind Farms
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- More and larger wind farms are planned offshore. As the most suitable build sites are limited wind farms will be constructed near to each other in so called wind farm clusters. Behind the wind turbines in these farms there is a disrupted flow of air called a wake that is characterized by reduced wind speed and increased turbulence. These individual turbine wakes combine to form a farm wake that can travel a long distance. In wind farm clusters farm to farm interaction will occur, i.e. the long distance wake from one wind farm will impact the wind conditions for other farms in the surrounding area.The thesis contains numerical studies of these long distance wakes. In this study Large Eddy Simulations (LES) using an Actuator Disc method (ACD) are used. A prescribed boundary layer is used where the wind shear is introduced using body forces. The turbulence, based on the Mann model, is introduced as fluctuating body forces upstream of the farm. A neutral atmosphere is assumed. The applied method has earlier been used for studies of wake effects inside farms but not for the longer distances needed for farm to farm interaction.Numerical studies are performed to get better knowledge about the use of this model for long distance wakes. The first study compares the simulation results with measurements behind an existing farm. Three parameter studies are thereafter setup to analyze how to best use the model. The first parameter study examines numerical and physical parameters in the model. The second one looks at the extension of the domain and turbulence as well as the characteristics of the flow far downstream. The third one gathers information on the downstream development of turbulence with different combinations of wind shear and turbulence level. The impact of placing the turbines at different distances from the turbulence plane is also studied. Finally a second study of an existing wind farm is performed and compared with a mesoscale model. The model is shown to be relevant also for studies of long distance wakes. Combining LES with a mesoscale model can be of interest.
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| 7. |
- Eriksson, Ola, 1979-, et al.
(författare)
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The Long distance wake behind Horns Rev I studied using large eddy simulations and a wind turbine parameterization in WRF
- 2017
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 854
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present paper is to obtain a better understanding of long distance wakes generated by wind farms as a first step towards a better understanding of farm to farm interaction. The Horns Rev I (HR) wind farm is considered for this purpose, where comparisons are performed between microscale Large Eddy Simulations (LES) using an Actuator Disc model (ACD), mesoscale simulations in the Weather Research and Forecasting Model (WRF) using a wind turbine parameterization, production data as well as wind measurements in the wind farm wake. The LES is manually set up according to the wind conditions obtained from the mesoscale simulation as a first step towards a meso/microscale coupling.The LES using an ACD are performed in the EllipSys3D code. A forced boundary layer (FBL) approach is used to introduce the desired wind shear and the atmospheric turbulence field from the Mann model. The WRF uses a wind turbine parameterization based on momentum sink. To make comparisons with the LESs and the site data possible an idealized setup of WRF is used in this study.The case studied here considers a westerly wind direction sector (at hub height) of 270 ± 2.5 degrees and a wind speed of 8 ± 0.5 m/s. For both the simulations and the site data a neutral atmosphere is considered. The simulation results for the relative production as well as the wind speed 2 km and 6 km downstream from the wind farm are compared to site data. Further comparisons between LES and WRF are also performed regarding the wake recovery and expansion.The results are also compared to an earlier study of HR using LES as well as an earlier comparison of LES and WRF. Overall the results in this study show a better agreement between LES and WRF as well as better agreement between simulations and site data.The procedure of using the profile from WRF as inlet to LES can be seen as a simplified coupling of the models that could be developed further to combine the methods for cases of farm to farm interaction.
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| 8. |
- Katsogiannos, Petros, 1979-
(författare)
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Bariatric surgery as treatment of type 2 diabetes – clinical and mechanistic aspects
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bariatric surgery can rapidly improve glycemic control and cardiovascular risk factors in patients with T2D and obesity. These improvements appear to be partly independent of weight loss, however, the underlying mechanisms remain incompletely understood. A randomized controlled trial was designed where 19 patients with obesity and T2D were either operated with a Roux-en-Y gastric bypass (RYGB) operation or continued with standard-of-care treatment and followed up for 2 years, providing the data for Paper I-III.In paper I, we focused on changes in whole-body glucose metabolism in relation to changes in adipose tissue metabolism and morphology. We observed an early adipose tissue remodeling and a reduction in adipocyte size that however, did not correlate to the early improvements in metabolic control.In paper II, we analyzed the neuroendocrine changes after RYGB. We observed changes within 4 weeks with signs of enhanced parasympathetic outlow, reduced morning cortisol, and enhanced incretin and glucagon responses to glucose, suggesting that neurohormonal mechanisms can contribute to the rapid improvement of insulin resistance and glycemia following RYGB in T2D.In paper III the patients from the RYGB group were interviewed 2 years after surgery to examine the effects of surgery on health-related quality of life (HRQoL). We found that the improved HRQoL after RYGB was not explained specifically by the magnitude of weight loss, but rather by the participants achieving a state of union between body and consciousness.In paper IV, we compared changes in circulating cytokine and adipokine levels in obese patients with- and without T2D. We observed that the cytokine profile of these patients is altered when compared to lean healthy control subjects and persist to a large extent after RYGB despite the weight loss and improved metabolic status.In conclusion, we observed that in the early post-operative period, neurohormonal changes appear to be more important than adipose tissue changes in improving insulin sensitivity and leading to diabetes remission.In the qualitative part of our study, we observed that the improved HRQoL was not solely explained by weight loss
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| 9. |
- Katsogiannos, Petros, 1979-, et al.
(författare)
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Changes in Circulating Cytokines and Adipokines After RYGB in Patients with and without Type 2 Diabetes
- 2021
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Ingår i: Obesity. - : Wiley. - 1930-7381 .- 1930-739X. ; 29:3, s. 535-542
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveThis study aimed to compare cytokine and adipokine levels in patients with obesity with and without type 2 diabetes (T2D) at baseline and 6 months after Roux‐en‐Y gastric bypass (RYGB) with healthy controls.MethodsA total of 34 patients (21 with T2D) with BMI of 30 to 45 kg/m2 were compared with 25 healthy controls without obesity. Cytokines, adipokines, and peptides of relevance for inflammation and metabolism were analyzed in plasma.ResultsSignificant decreases in weight and glycated hemoglobin A1c were observed. At baseline, interleukin‐6 (IL‐6), IFN‐β, IL‐18, leptin, and hepatocyte growth factor were higher in all patients with obesity compared with healthy controls. In patients without T2D, TNF‐α, IL‐1α, IL‐2, IL‐15, and visfatin were also increased, whereas bone morphogenic protein‐4 was decreased. Following RYGB, IL‐6 and hepatocyte growth factor were still increased in both groups compared with controls. In T2D patients, IFN‐β, IL‐27, IL‐1α, IL‐2, regenerating islet‐derived protein 3A, visfatin, and osteopontin were found to be increased. In patients without T2D, TNF‐α, IL‐1α, IL‐2, IL‐15, leptin, and visfatin remained increased.ConclusionsThe altered cytokine profile of patients with obesity persisted after RYGB despite large weight loss and improved metabolic status, thus reflecting an inherent inflammatory state.
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| 10. |
- Petrović, Bojana, et al.
(författare)
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Carbon Assessment of a Wooden Single-Family Building : Focusing on Re-Used Building Products
- 2024
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Ingår i: Buildings. - 2075-5309. ; 14:3
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Tidskriftsartikel (refereegranskat)abstract
- Previous research has shown a lack of studies with comparisons between primary (virgin) and secondary (re-used) building materials, and their embodied emissions. The creation of different scenarios comparing the environmental impact of virgin vs. re-used materials is also motivated by the scarcity of raw materials in the world and the emergency of mitigating greenhouse gas (GHG) emissions from buildings. The aim of this study was to investigate scenarios, including new vs. re-used building products, applying the LCA method for a wooden single-family building. The findings showed a 23% reduction potential for total released (positive) CO2e when comparing the Reference scenario with Scenario I, using re-used wooden-based materials. Further, Scenario II, using all re-used building materials except for installations, showed a 59% CO2e reduction potential compared to the Reference scenario. Finally, Scenario III, which assumes all re-used building products, showed a 92% decreased global warming potential (GWP) impact compared to the Reference scenario. However, when including biogenic carbon and benefits (A5 and D module), the Reference scenario, based on newly produced wooden building materials, has the largest negative GHG emissions. It can be concluded that the re-use of building products leads to significant carbon savings compared to using new building products.
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