| 271. |
- Lodén, Jonas, 1973, et al.
(författare)
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Towards Energy Efficient Housing – the importance of local energy planning
- 2009
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Ingår i: Proceedings of International Forum on Energy Efficiency in Housing, 23-25 November 2009, Vienna, Austria.
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Konferensbidrag (refereegranskat)abstract
- A strategy for local energy planning must be in place in order to transform the local energy system and must comprise all relevant sectors and decision makers, i.e. include the residential sector with its relevant stakeholders. Thus, the housing sector cannot be treated inisolation but should rather be part of an analysis which takes a municipal energy systems perspective. This paper reports from an EU IEE (Intelligent Energy Europe) supported work named PATH-TO-RES which develops a methodology to be used as support tool for local energyplanning. The work uses a number of local case studies (Göteborg (SE), Valencia (ES), Dunkerque (FR), Gdansk (PL) and Arnhem and Lochem (NL)) to develop a step-by-stepassessment which can evaluate and define Pathways to renewable and efficient energy systems.A Pathway is a cost efficient way to bridge over from the present energy system to a sustainable system. In short, the proposed methodology starts with a detailed description of the present system (energy infrastructure as well as decision makers and stakeholders) and, based on this, anumber of steps are defined with the aim to serve as check points to ensure that one or more Pathways can be formulated which describe how the local energy system can be transformed to comply with goals and targets.In order to describe the energy systems of the six case studies in a common way, a schematic model called a RES-diagram (RES=Reference Energy System) has been applied, from which the structure (i.e. components, flows and connections) and energy balance of the systems can bedetermined. In the six municipalities studied considerable variation of population, land area and scale and characteristics of the existing energy systems exist. Differences and similarities between the six systems are highlighted and the paper discusses pre-requisites and conditions for municipal energy planning, based on energy systems of the case study regions.
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| 272. |
- Lundblad, Therese, 1993, et al.
(författare)
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An open data-based model for generating a synthetic low-voltage grid to estimate hosting capacity
- 2024
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Ingår i: Sustainable Energy, Grids and Networks. - 2352-4677. ; 39
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Tidskriftsartikel (refereegranskat)abstract
- This study develops and applies an open data-based reference electricity grid analysis (REGAL) model designed to create a synthetic representation of a low-voltage (LV) grid for a country-size geographic area. The model enables large-scale grid simulation in which new loads, such as electric vehicle charging, can be added to estimate their impacts on the current LV grid. The modeling is carried out in three steps: (1) generation of a synthetic LV grid; (2) addition of residential loads, including electric vehicle charging; and (3) evaluating if the grid capacity is exceeded. The grid is generated by selecting transformers and cables so that the system can fulfill the current demand while meeting national regulations and standards for distribution grids, all at the lowest total cost. This paper presents the results of calibration and validation against real-world data for the predicted electricity demands and synthetic grid generated by the model. Different calibration values were explored, and the accuracy of the estimations of grid capacities was calibrated using proprietary real-world data from grid operators. For a region with multiple grid cells, an average deviation from real-world data of ±10 % was achieved. For an average area of 1 km2, the error was 44.5 %, which means that the model is not suitable for analysis on this geographic level. However, the level of accuracy is deemed sufficient for initial estimations of hosting capacity for larger geographic areas, such as a region or a country, thereby enabling estimations of hosting capacity in new areas that lack publicly accessible grid capacities.
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| 273. |
- Lundblad, Therese, 1993, et al.
(författare)
-
Centralized and decentralized electrolysis-based hydrogen supply systems for road transportation – A modeling study of current and future costs
- 2023
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 48:12, s. 4830-4844
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Tidskriftsartikel (refereegranskat)abstract
- This work compares the costs of three electrolysis-based hydrogen supply systems for heavy road transportation: a decentralized, off-grid system for hydrogen production from wind and solar power (Dec-Sa); a decentralized system connected to the electricity grid (Dec-Gc); and a centralized grid-connected electrolyzer with hydrogen transported to refueling stations (Cen-Gc). A cost-minimizing optimization model was developed in which the hydrogen production is designed to meet the demand at refueling stations at the lowest total cost for two timeframes: one with current electricity prices and one with estimated future prices. The results show that: For most of the studied geographical regions, Dec-Gc gives the lowest costs of hydrogen delivery (2.2–3.3€/kgH2), while Dec-Sa entails higher hydrogen production costs (2.5–6.7€/kgH2). In addition, the centralized system (Cen-Gc) involves lower costs for production and storage than the grid-connected decentralized system (Dec-Gc), although the additional costs for hydrogen transport increase the total cost (3.5–4.8€/kgH2).
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| 274. |
- Lyngfelt, Anders, 1955, et al.
(författare)
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Dependence of Sulphur Capture Performance on Air Staging in a 12 MW Circulating Fluidised Bed Boiler
- 1993
-
Ingår i: Gas Cleaning at High Temperatures, Eds. R. Clift and J.P.K. Seville, Blackie Academic & Professional, Glasgow, ISBN 0 7514 0178 1.. - 0751401781 ; , s. 470-491
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Three cases of air staging were examined in a 12 MW circulating fluidised bed boiler: i) no staging, ii} normal staging and iii) intensified staging. The conditions inside the combustion chamber were investigated by zirconia cell measurements of the oxygen partial pressure, 0.35, 0.65 and 8 m above the bottom air distributor plate. A significant effect of the degree of staging was seen in the two lower locations: At 0.65 m height the fraction of time under substoichiometric conditions was low in the no-staging case (2-35%), at normal staging it was 70-90%, whereas at intensified staging it was 100Y.. At 0.35 m height, i.e. in the dense bed, a similar effect was seen, although the fraction of time under reducing conditions was lower. The fraction of time under reducing conditions was low in the top of the combustion chamber in all three cases . The increase in the fraction of time under reducing conditions with a higher degree of staging is associated with a decrease in sulphur capture. It is assumed that a release of SO2 from CaSO4 takes place during the transitions between oxidising and reducing conditions. Thus, the rapid alternations between oxidising and reducing conditions, as seen with the zirconia cell, offer an explanation of the reductive decomposition and, accordingly, of the dependence of sulphur capture on temperature and on the extent of staging.
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| 275. |
- Magnusson, Anna, 1974, et al.
(författare)
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Dual fibre optical probe measurements of solids volume fraction in a circulating fluidized bed
- 2005
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 151:1-3, s. 19-26
-
Tidskriftsartikel (refereegranskat)abstract
- The calibration of a dual fibre optical probe was experimentally investigated in a circulating fluidized bed. The particle volume fraction registered by the optical probe was compared to pressure drop measurements for a range of operating conditions. A theoretical calibration theory was applied to the probe signal to obtain the local and instantaneous particle volume fraction. It was found that glare points on the particles and the beam length from the probe to the particle determines the curvature of the calibration function to a large extent.
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| 276. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
-
A novel experimental method for determining lateral mixing of solids in fluidized beds – Quantification of the splash-zone contribution
- 2020
-
Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 370, s. 96-103
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental method to investigate the lateral mixing of bulk solids in bubbling fluidized beds is presented.The method utilizes finite volume analysis of the measured temperature field over the bed surface, from which the solids dispersion coefficient is determined. The temperature field is measured with a thermographic camera,which in this work is applied to a fluid-dynamically down-scaled fluidized bed that resembles the conditions relevant for hot large-scale operation.The method is applied to investigate the effect of key parameters for the solids mixing process; fluidization velocity, particle size and pressure drop over the air distributor plate. The results showed up-scaled dispersion coefficients in the order of 10−3m2/s for the conditions investigated. The lateral mixing of solids decreased with increasing particle size and increased with increases in the fluidization velocity and pressure drop over the air distributor. The method was also used to quantify the contribution of the splash zone to the total lateral solids mixing. When lateral solids mixing in the splash zone was blocked with a vertical baffle the lateral solids dispersion was reduced by some 90%.
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| 277. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
-
Calcium looping for combined CO 2 capture and thermochemical energy storage
- 2023
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Ingår i: Circular Economy Processes for CO2 Capture and Utilization: Strategies and Case Studies. - 9780323956680 ; , s. 119-162
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The carbonation of calcium oxide (CaO) has been extensively investigated concerning the separation of CO2 from gaseous streams. The carbonation reaction is of special interest in postcombustion processes for the capture of CO2 since the produced calcium carbonate (CaCO3) can be calcined in a separate reactor to generate a stream of pure CO2 for sequestration and storage. The cycle, which consists of carbonation and calcination reactions, involves considerable heat of reaction, rendering the process relevant not only for CO2 capture but also for energy storage purposes in the form of thermochemical energy storage (TCES). Energy storage is envisioned as an important flexibility measure to increase the penetration of variable renewable electricity (VRE), thereby increasing the value of VRE due to the reduced share of generation that needs to be curtailed. In this chapter, the general characteristics of the calcium looping process for both CO2 capture and energy storage are presented. Thereafter, the process that combines these two features is described, focusing on its layout specifications, associated opportunities and challenges, and the most recent advances toward its development.
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| 278. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
-
Comparison of the Dynamic Behaviour between Bubbling and Circulating Fluidized Bed Combustors
- 2020
-
Ingår i: INFUB - 12th European Conference on Industrial Furnaces and Boilers.
-
Konferensbidrag (refereegranskat)abstract
- This work compares the dynamic behaviour of the flue gas side of large-scale bubbling and circulating fluidized bed (BFB and CFB respectively) boilers. For this, a dynamic model is developed and presented. The model is used to simulate two industrial units and is validated against steady-state operational data. The model is applied to investigate and compare the transient behaviour of BFB and CFB boilers of the same size given step changes in load and moisture content. Results show that for a certain load change the heat transfer to the waterwalls stabilizes faster in BFB units, yielding larger relative changes in temperature once a new steady state is established. Differences in stabilization time between the dense bed and the top of the furnace are observed in both units, caused by the distribution of solids along the combustor: the dense bed contains more solids than regions located higher up in the furnace and therefore it is found to be less sensitive to changes and slower to respond, with stabilization times of around 15 minutes in contrast to the 1-8 minutes observed for the upper furnace. This behaviour is accentuated in the BFB case where all the solids remain in the dense bottom region.
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| 279. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
-
Comparison of the Transient Behaviors of Bubbling and Circulating Fluidized Bed Combustors
- 2023
-
Ingår i: Heat Transfer Engineering. - : Informa UK Limited. - 0145-7632 .- 1521-0537. ; 44:4, s. 303-316
-
Tidskriftsartikel (refereegranskat)abstract
- This work compares the transient behaviors of the flue gas sides of large-scale bubbling and circulating fluidized bed (BFB and CFB, respectively) boilers. For this purpose, a dynamic model of the in-furnace side of fluidized bed combustors presented and validated by the authors in a former work is used to simulate two industrial units. The results show that for load changes the heat transfer to the waterwalls stabilizes more rapidly in BFB units. Differences in stabilization time between the dense bed and the top of the furnace are observed in both units, caused by the distribution of solids along the combustor: the dense bed contains more solids than regions located higher up in the furnace and, therefore slower to respond, with stabilization times of around 15 minutes, as compared to stabilization times in the range of 1-8 minutes for the upper furnace. This behavior is accentuated in the BFB, where all the solids remain in the dense bottom region. The effect of the characteristic times of the main in-furnace mechanisms (fluid-dynamics, fuel conversion, and heat transfer) on the dynamic performance of BFB and CFB units has been explored and expressed through proposed mathematical relationships.
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| 280. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
-
Dynamic modeling of the flue gas side of large-scale circulating fluidized bed boilers
- 2021
-
Ingår i: CFB 2021 - Proceedings of the 13th International Conference on Fluidized Bed Technology. ; , s. 59-64
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a 1.5D dynamic model of the gas side of large-scale circulating fluidized bed boilers. The model accounts for the solid’s hydrodynamics, the fuel conversion and the heat transfer to the waterwalls. The model is validated with industrial data from a 100 MWth unit, showing a good agreement between simulation results and measured data. The validated model is used to study the dynamics of the furnace after a load change is introduced. Simulation results show that regions with large concentration of solids are slower to reach steady-state but are less sensitive to load changes.
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