| 1. |
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| 2. |
- Gustafsson, Marcus, 1987-, et al.
(author)
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Techno-economic analysis of energy renovation measures for a district heated multi-family house
- 2016
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 177, s. 108-116
-
Journal article (peer-reviewed)abstract
- Renovation of existing buildings is important in the work toward increased energy efficiency and reduced environmental impact. The present paper treats energy renovation measures for a Swedish district heated multi-family house, evaluated through dynamic simulation. Insulation of roof and façade, better insulating windows and flow-reducing water taps, in combination with different HVAC systems for recovery of heat from exhaust air, were assessed in terms of life cycle cost, discounted payback period, primary energy consumption, CO2 emissions and non-renewable energy consumption. The HVAC systems were based on the existing district heating substation and included mechanical ventilation with heat recovery and different configurations of exhaust air heat pump.Compared to a renovation without energy saving measures, the combination of new windows, insulation, flow-reducing taps and an exhaust air a heat pump gave up to 24% lower life cycle cost. Adding insulation on roof and façade, the primary energy consumption was reduced by up to 58%, CO2 emissions up to 65% and non-renewable energy consumption up to 56%. Ventilation with heat recovery also reduced the environmental impact but was not economically profitable in the studied cases. With a margin perspective on electricity consumption, the environmental impact of installing heat pumps or air heat recovery in district heated houses is increased. Low-temperature heating improved the seasonal performance factor of the heat pump by up to 11% and reduced the environmental impact.
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| 3. |
- Salehin, Sayedus, et al.
(author)
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Designing of an emergency energy module for relief and refugee camp situations : Case study for a refugee camp in Chad-Sudan border
- 2011
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In: 2011 World Congress on Sustainable Technologies. - 9780956426345 ; , s. 9-14
-
Conference paper (peer-reviewed)abstract
- Each year thousands of people get displaced and are forced to live in refugee camps or relief camps because of man-made or natural disasters. These people often lack basic needs such as clean water, lighting, cooling, etc. and many times these camps exist for more than 7-8 years. This paper aims at conceptualizing an Emergency Energy Module (EEM) which provides electrical energy to satisfy the basic needs and that can be deployed as an emergency response in a self-sufficient, self-contained, and highly mobile fashion, to support the energy demand of a refugee or a relief camp and the aid workers for long term. As a case study, a refugee camp near Chad-Sudan border has been investigated. As a preliminary study, electrical demand was determined for the camp. Further, locally available energy resources were studied and assessed based on key design criteria and the technologies were selected to meet the demand. Polycrystalline Solar PV panels, micro wind turbine and biogas polyethylene digester and diesel generator were chosen as the technology to harness selected energy resources. HOMER Software has been used for optimization and techno-economic analysis of the energy system. The selected solution has been, then, analyzed from an operational point of view.
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| 4. |
- Okda, Sherif, et al.
(author)
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Testing of the Aerodynamic Characteristics of an Inflatable Airfoil Section
- 2020
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In: Journal of Aerospace Engineering. - 1943-5525 .- 0893-1321. ; 33:5
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Journal article (peer-reviewed)abstract
- Inflatable structures are characterized by being light and easy to manufacture and deploy. Hence, they find many applications in aerospace and aeronautical engineering. In this paper, an inflatable segment with a The National Advisory Committee for Aeronautics (NACA) 0021 airfoil cross-section is designed, fabricated, and tested. The geometrical accuracy of the manufactured inflatable segment is measured using laser scanning. Measurements show that the average normalized error of the chord length and thickness are 2.97% and 0.554%, respectively. The aerodynamic behavior of the inflatable segment is then tested in a wind tunnel at different wind speeds and angles of attack. Lift forces are measured using a six-component balance, while the drag forces are calculated from the wake measurements. The lift and drag coefficients of the inflatable section are compared to those of a standard NACA 0021 airfoil. Finally, flow visualization is examined at different angles of attack using two methods: smoke and tufts. Both methods show that flow separation starts at 15° and full stall occurs at 25°. Results indicate that inflatables can find more applications in the design and construction of aerodynamic structures, such as wings.
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| 5. |
- Chen, B., et al.
(author)
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Pathways for sustainable energy transition
- 2019
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In: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 228, s. 1564-1571
-
Journal article (peer-reviewed)abstract
- Energy transitions are ongoing processes all over the world. While sustainable solutions are envisioned for the future, many societies are still under high-carbon and high-pollution energy regime borne by fossil fuels. How to design pathways towards sustainable energy transition has attracted worldwide concerns. Understanding the possible transition pathways of the energy system requires the integration of new energy technologies, environmental sciences, economics and management. This Special Issue of Journal of Cleaner Production targets to collect the latest research results on sustainable energy systems, discover innovative avenues and inspiring models and share knowledge on energy system modelling and management. In this paper, we identify 4 themes on sustainable energy transition pathways including: (1)Sustainable energy economics and management; (2)Renewable energy generation and consumption; (3)Environmental impacts of energy systems; and (4)Electric vehicle and energy storage. Theories, technologies, innovative models, and successful experiences are discussed accordingly. It is suggested that creative, robust and audacious strategies in governance, management and education are needed to boost sustainable energy transition across various scales and sectors.
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| 6. |
- von Platten, Jenny, et al.
(author)
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Renovating on unequal premises : A normative framework for a just renovation wave in swedish multifamily housing
- 2021
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In: Energies. - : MDPI. - 1996-1073. ; 14:19
-
Journal article (peer-reviewed)abstract
- While the energy transition of the EU housing stock is now being intensified with the launch of the Renovation Wave, economic inequalities are increasing in many OECD countries, which has effects on housing-related inequalities and the demand of affordable housing. The Renovation Wave is thus an opportunity to improve housing quality for low-income households, but also entails risks for increased rents. In Sweden, the standard of housing is relatively high and energy poverty in multifamily housing is rare, meaning that there are limited social benefits to be achieved from extensive energy retrofitting; moreover, Sweden lacks a social housing sector, which limits protection of the worst-off residents. This paper thus explores whether the limited social benefits of the Renovation Wave weigh up against the risks that it entails for the worst-off in the Swedish context. This is done within a normative framework for just energy transitioning that is developed within the context of the Renovation Wave and increasing economic inequalities, consisting of four ordered principles: (1) The equal treatment principle; (2) The priority principle; (3) The efficiency principle; and (4) The principle of procedural fairness. Analysis showed that to be considered just according to our framework, the Swedish energy transition of housing should, in contradistinction to what is suggested in the Renovation Wave, limit the imposition of extensive energy retrofitting in low-income areas. Finally, having identified a mismatch between the most effective approaches in terms of energy savings and the most acceptable approaches in terms of social justice, we offer policy recommendations on how to bridge this mismatch in a Swedish context. © 2021 by the authors.
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| 7. |
- Mathern, Alexandre, 1986, et al.
(author)
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Concrete Support Structures for Offshore Wind Turbines: Current Status, Challenges, and Future Trends
- 2021
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In: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 14:7
-
Research review (peer-reviewed)abstract
- Today’s offshore wind turbine support structures market is largely dominated by steel structures, since steel monopiles account for the vast majority of installations in the last decade and new types of multi-leg steel structures have been developed in recent years. However, as wind turbines become bigger, and potential sites for offshore wind farms are located in ever deeper waters and ever further from the shore, the conditions for the design, transport, and installation of support structures are changing. In light of these facts, this paper identifies and categorizes the challenges and future trends related to the use of concrete for support structures of future offshore wind projects. To do so, recent advances and technologies still under development for both bottom-fixed and floating concrete support structures have been reviewed. It was found that these new developments meet the challenges associated with the use of concrete support structures, as they will allow the production costs to be lowered and transport and installation to be facilitated. New technologies for concrete support structures used at medium and great water depths are also being developed and are expected to become more common in future offshore wind installations. Therefore, the new developments identified in this paper show the likelihood of an increase in the use of concrete support structures in future offshore wind farms. These developments also indicate that the complexity of future support structures will increase due to the development of hybrid structures combining steel and concrete. These evolutions call for new knowledge and technical know-how in order to allow reliable structures to be built and risk-free offshore installation to be executed.
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| 8. |
- Herre, Lars, 1990-, et al.
(author)
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Simplified model of integrated paper mill for optimal bidding in energy and reserve markets
- 2020
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In: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 279
-
Journal article (peer-reviewed)abstract
- Due to the increased use of variable renewable energy sources, more capacity for reserves is required. Non-generating resources such as large industrial consumers can arbitrage energy prices and provide reserve capacity by exploiting the inherent flexibility in selected industrial processes. A large enough industrial consumer can capitalize on this flexibility through optimized bidding in electricity markets. In this work, the day-ahead cost minimization of a risk-averse pulp and paper mill is formulated as a two-stage stochastic problem, considering thermodynamic and electrical constraints. The bids in the energy and reserve markets are jointly optimized subject to price uncertainty as well as uncertainty of frequency realization. The results of a case study in Sweden display a significant economic benefit in exploiting the flexibility of integrated pulp and paper mills with electric boilers. The expected cost of the pulp and paper mill resulting from different strategies are compared and the risk-aversion of the pulp and paper mill is investigated. Reserve offers are mainly facilitated by fast-acting electric boilers and supported by flexibility in the steam network. We show that reserve offers can significantly improve the profitability of the pulp and paper mill.
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| 9. |
- Lv, Zhihan, Dr. 1984-, et al.
(author)
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Towards carbon Neutrality : Prediction of wave energy based on improved GRU in Maritime transportation
- 2023
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In: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 331
-
Journal article (peer-reviewed)abstract
- Efficient use of renewable energy is one of the critical measures to achieve carbon neutrality. Countries have introduced policies to put carbon neutrality on the agenda to achieve relatively zero emissions of greenhouse gases and to cope with the crisis brought about by global warming. This work analyzes the wave energy with high energy density and wide distribution based on understanding of various renewable energy sources. This study provides a wave energy prediction model for energy harvesting. At the same time, the Gated Recurrent Unit network (GRU), Bayesian optimization algorithm, and attention mechanism are introduced to improve the model's performance. Bayesian optimization methods are used to optimize hyperparameters throughout the model training, and attention mechanisms are used to assign different weights to features to increase the prediction accuracy. Finally, the 1-hour and 6-hour forecasts are made using the data from China's NJI and BSG observatories, and the system performance is analyzed. The results show that, compared with mainstream prediction algorithms, GRU based on Bayesian optimization and attention mechanism has the highest prediction accuracy, with the lowest MAE of 0.3686 and 0.8204, and the highest R2 of 0.9127 and 0.6436, respectively. Therefore, the prediction model proposed here can provide support and reference for the navigation of ships powered by wave energy.
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| 10. |
- Lindroth [formerly Tyrberg], Simon, 1979-
(author)
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Buoy and Generator Interaction with Ocean Waves : Studies of a Wave Energy Conversion System
- 2011
-
Doctoral thesis (other academic/artistic)abstract
- On March 13th, 2006, the Division of Electricity at Uppsala University deployed its first wave energy converter, L1, in the ocean southwest of Lysekil. L1 consisted of a buoy at the surface, connected through a line to a linear generator on the seabed. Since the deployment, continuous investigations of how L1 works in the waves have been conducted, and several additional wave energy converters have been deployed. This thesis is based on ten publications, which focus on different aspects of the interaction between wave, buoy, and generator. In order to evaluate different measurement systems, the motion of the buoy was measured optically and using accelerometers, and compared to measurements of the motion of the movable part of the generator - the translator. These measurements were found to correlate well. Simulations of buoy and translator motion were found to match the measured values. The variation of performance of L1 with changing water levels, wave heights, and spectral shapes was also investigated. Performance is here defined as the ratio of absorbed power to incoming power. It was found that the performance decreases for large wave heights. This is in accordance with the theoretical predictions, since the area for which the stator and the translator overlap decreases for large translator motions. Shifting water levels were predicted to have the same effect, but this could not be seen as clearly. The width of the wave energy spectrum has been proposed by some as a factor that also affects the performance of a wave energy converter, for a set wave height and period. Therefore the relation between performance and several different parameters for spectral width was investigated. It was found that some of the parameters were in fact correlated to performance, but that the correlation was not very strong. As a background on ocean measurements in wave energy, a thorough literature review was conducted. It turns out that the Lysekil project is one of quite few projects that have published descriptions of on-site wave energy measurements.
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| 11. |
- Behzadi, Amirmohammad, et al.
(author)
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A Green and Energy-Efficient Smart Building Driven by Photovoltaic Thermal Panels Connected to the Grid
- 2023
-
In: International Conference on Smart Cities and Green ICT Systems, SMARTGREENS - Proceedings. - : Science and Technology Publications, Lda. - 9789897586514 ; , s. 106-112
-
Conference paper (peer-reviewed)abstract
- The present paper introduces a new smart building system driven by photovoltaic thermal panels. The concept is to improve the contribution of renewable energy in the local matrix for peak load shaving by having a two-way connection with the local electricity network via a rule-based energy monitoring control design. Besides, the feasibility of removing the electrical storage unit with high investment cost is studied by establishing a dynamic interaction between the energy production and usage components to reduce the energy costs over the year. The system has intelligent thermal energy storage integrated with an electrically-driven coil, heat exchanger, pumps, and several smart valves and control units. The transient system simulation (TRNSYS) package is implemented to assess the practicality of the suggested intelligent model for a building complex in Malmo, Sweden. According to the parametric outcomes, by raising the panel area, while the generated electricity increases, the solar utilization factor falls, indicating conflictive changes among performance metrics. The results also show that the renewable resource covers the building's heating and electricity demands for the majority of the year and that a significant amount of energy is sold to the neighbourhood electricity grid, demonstrating the viability of the introduced intelligent model.
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| 12. |
- Binder, Christian, 1988-, et al.
(author)
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Phosphor Thermometry for In-Cylinder Surface Temperature Measurements in Diesel Engines
- 2019
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In: Measurement science and technology. - 0957-0233 .- 1361-6501.
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Journal article (other academic/artistic)abstract
- Surface temperature measurements in technically relevant applications can be very hallenging and yet of great importance. Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor’s luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based phosphor thermometry. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors’ luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including four which – to the authors’ knowledge –have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of serval tens of Kelvin.
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| 13. |
- Skagestad, Ragnhild, 1978, et al.
(author)
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GCCSI Webinar: Cutting Cost of CO2 Capture in Process Industry (CO2stCap) Project overview & first results for partial CO2 capture at integrated steelworks
- 2017
-
Other publication (other academic/artistic)abstract
- GCCSI Webinar: Cutting Cost of CO2 Capture in Process Industry (CO2stCap) Project overview & first results for partial CO2 capture at integrated steelworks This publication has the format of a webinar: The CO2StCap project is a four year initiative carried out by industry and academic partners with the aim of reducing capture costs from CO2 intensive industries (more information here). The project, led by Tel-Tek, is based on the idea that cost reduction is possible by capturing only a share of the CO2 emissions from a given facility, instead of striving for maximized capture rates. This can be done in multiple ways, for instance by capturing only from the largest CO2 sources at individual multi-stack sites utilising cheap waste heat or adapting the capture volumes to seasonal changes in operations. The main focus of this research is to perform techno-economic analyses for multiple partial CO2 capture concepts in order to identify economic optimums between cost and volumes captured. In total for four different case studies are developed for cement, iron & steel, pulp & paper and ferroalloys industries. The first part of the webinar gave an overview of the project with insights into the cost estimation method used. The second part presented the iron & steel industry case study based on the Lulea site in Sweden, for which waste-heat mapping methodology has been used to assess the potential for partial capture via MEA-absorption. Capture costs for different CO2 sources were discussed, demonstrating the viability of partial capture in an integrated steelworks.
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| 14. |
- Johansson, Björn, 1975, et al.
(author)
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Power Level Sampling of Metal Cutting Machines for Data Representation in Discrete Event Simulation
- 2015
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In: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 53:23, s. 7060-7070
-
Journal article (peer-reviewed)abstract
- An extension to the application area for discrete event simulation (DES) has been ongoing since the last decade and focused only on economic aspects to include ecologic sustainability. With this new focus, additional input parameters, such as electrical power consumption of machines, are needed. This paper aim at investigating how NC machine power consumption should be represented in simulation models of factories. The study includes data-sets from three different factories. One factory producing truck engine blocks, one producing brake disc parts for cars and one producing forklift components. The total number of data points analysed are more than 2,45,000, where of over 1,11,000 on busy state for 11 NC machines. The low variability between busy cycles indicates that statistical representations are not adding significant variability. Furthermore, results show that non-value-added activities cause a substantial amount of the total energy consumption, which can be reduced by optimising the production flow using dynamic simulations such as DES.
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| 15. |
- Shahroozi, Zahra, 1992-
(author)
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Survivability control using data-driven approaches and reliability analysis for wave energy converters
- 2024
-
Doctoral thesis (other academic/artistic)abstract
- Wave energy, with five times the energy density of wind and ten times the power density of solar, offers a compelling carbon-free electricity solution. Despite its advantages, ongoing debates surround the reliability and economic feasibility of wave energy converters (WECs). To address these challenges, this doctoral thesis is divided into four integral parts, focusing on optimizing the prediction horizon for power maximization, analyzing extreme waves' impact on system dynamics, ensuring reliability, and enhancing survivability in WECs.Part I emphasizes the critical importance of the prediction horizon for maximal power absorption in wave energy conversion. Using generic body shapes and modes, it explores the effect of dissipative losses, noise, filtering, amplitude constraints, and real-world wave parameters on the prediction horizon. Findings suggest achieving optimal power output may be possible with a relatively short prediction horizon, challenging traditional assumptions.Part II shifts focus to WEC system dynamics, analyzing extreme load scenarios. Based on a 1:30 scaled wave tank experiment, it establishes a robust experimental foundation, extending into numerical assessment of the WEC. Results underscore the importance of damping to alleviate peak forces. Investigating various wave representations highlights conservative characteristics of irregular waves, crucial for WEC design in extreme sea conditions.Part III explores the computational intricacies of environmental design load cases and fatigue analyses for critical mechanical components of the WEC. The analysis is conducted for hourly sea state damage and equivalent two-million-cycle loads. Finally, a comparison of safety factors between the ultimate limit state and fatigue limit state unfolds, illustrating the predominant influence of the ultimate limit state on point-absorber WEC design.Part IV, centers on elevating survivability strategies for WECs in extreme wave conditions. Three distinct controller system approaches leverage neural networks to predict and minimize the line force. Distinct variations emerge in each approach, spanning from rapid detection of optimal damping to integrating advanced neural network architectures into the control system with feedback. The incorporation of a controller system, refined through experimental data, showcases decreases in the line force, providing a practical mechanism for real-time force alleviation.This thesis aims to contribute uniquely to the goal of advancing wave energy conversion technology through extensive exploration.
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| 16. |
- Kyprianidis, Konstantinos, 1984, et al.
(author)
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Multidisciplinary Analysis of a Geared Fan Intercooled Core Aero-Engine
- 2014
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In: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 136:1
-
Journal article (peer-reviewed)abstract
- The reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, along with the reduction of engine nacelle drag and weight. One alternative design approach to improving specific fuel consumption is to consider a geared fan combined with an increased overall pressure ratio intercooled core performance cycle. The thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is very little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to analyze the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption. With minimum mission fuel in mind, the results indicate as optimal values a pressure ratio split exponent of 0.38 and an intercooler mass flow ratio of 1.18 at hot-day top of climb conditions. At ISA midcruise conditions a specific thrust of 86 m/s, a jet velocity ratio of 0.83, an intercooler effectiveness of 56%, and an overall pressure ratio value of 76 are likely to be a good choice. A 70,000 lbf intercooled turbofan engine is large enough to make efficient use of an all-axial compression system, particularly within a geared fan configuration, but intercooling is perhaps more likely to be applied to even larger engines. The proposed optimal jet velocity ratio is actually higher than the value one would expect by using standard analytical expressions, primarily because this design variable affects core efficiency at midcruise due to a combination of several different subtle changes to the core cycle and core component efficiencies at this condition. The analytical expressions do not consider changes in core efficiency and the beneficial effect of intercooling on transfer efficiency, nor do they account for losses in the bypass duct and jet pipe, while a relatively detailed engine performance model, such as the one utilized in this study, does. Mission fuel results from a surrogate model are in good agreement with the results obtained from a rubberized-wing aircraft model for some of the design parameters. This indicates that it is possible to replace an aircraft model with specific fuel consumption and weight penalty exchange rates. Nevertheless, drag count exchange rates have to be utilized to properly assess changes in mission fuel for those design parameters that affect nacelle diameter.
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| 17. |
- Wadekar, Sandip, 1989
(author)
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Large-Eddy Simulation of Gasoline Fuel Spray Injection at Ultra-High Injection Pressures
- 2021
-
Doctoral thesis (other academic/artistic)abstract
- Gasoline direct injection is a state-of-the-art technique that reduces hydrocarbon and particulate emissions. However, further improvement is needed to meet current as well as future emission regulations. A prominent solution is to increase the fuel injection pressure which allows faster fuel droplet atomization, quick evaporation and improves fuel-air mixture formation under realistic engine conditions. In this work, the gasoline fuel injection process at ultra-high injection pressures ranging from 200 to 1500 bar was analyzed using numerical models. In particular, the Large-Eddy Simulation (LES) method, with the standard Smagorinsky turbulence model, was utilized using the Eulerian formulation for the continuous phase. The discrete droplet phase was treated using a Lagrangian formulation together with spray sub-models. In the first part of study, spray was injected into an initially quiescent constant volume chamber using two different nozzle hole shape geometries: divergent and convergent. The numerical results were calibrated by reproducing experimentally observed liquid penetration length and efforts were made to understand the influence of ultra-high injection pressures on spray development. The calibrated models were then used to investigate the impact of ultra-high injection pressures on mean droplet sizes, droplet size distribution, spray-induced large-scale eddies and entrainment rate. The results showed that, at ultra-high injection pressures, the mean droplet sizes were significantly reduced and the droplets achieving very high velocities. Integral length scales of spray-induced turbulence and air entrainment rate were better for the divergent-shaped injector, and considerably larger at higher injection pressures compared to lower ones. In the second part of the study, four consecutive full-cycle cold flow LES simulations were carried out to generate realistic turbulence inside the engine cylinder. The first three cycles were ignored, with the fourth cycle being used to model the injection of the fuel using the divergent-shaped injector only (which was found to be better in the previous part of this study) at different injection pressures. In addition to the continuous gas phase (Eulerian) and the dispersed liquid (Lagrangian), the liquid film feature (Finite-Area) was used to model the impingement of fuel spray on the engine walls and subsequent liquid film formation. The simulation results were used to evaluate spray-induced turbulence, fuel-air mixing efficiency and the amount of liquid mass deposited on the walls. The limitation of the high-pressure injection technique with respect to liquid film formation was optimized using a start of injection (SOI) sweep. Overall results showed that the mixing efficiency increased at high injection pressure and that SOI should occur between early injection and late injection to optimize the amount of mass being deposited on the engine walls.
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| 18. |
- Honeth, Nicholas, et al.
(author)
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Application of the IEC 61850-7-420 data model on a hybrid renewable energy system
- 2011
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In: 2011 IEEE PES Trondheim PowerTech. - Trondheim : IEEE Communications Society. - 9781424484195 - 9781424484171
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Conference paper (peer-reviewed)abstract
- IEC 61850 is the most promising standard for design of substation communication and automation systems. Recent revisions of the standard include support for modeling, and control of Distributed Energy Resources (DER). This paper presents an application of the IEC 61850-7-420 data model for DER in the implementation of a control and energy management system for a Hybrid Renewable Energy System (HRES). These systems are beginning to prove their usefulness in providing deployable electrical supply in locations where no such supply exists as well as for backup power or power quality related support functions. The motivation for applying the standard to the design process is twofold; to modularize the design according to an accepted international standard and to design for interoperability with other IEC 61850 enabled devices and SCADA systems.
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| 19. |
- Yang, Shun-Han, 1987, et al.
(author)
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Parametric study of the dynamic motions and mechanical characteristics of power cables for wave energy converters
- 2018
-
In: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 23:1, s. 10-29
-
Journal article (peer-reviewed)abstract
- A case study of a point-absorber wave energy converter (WEC) system is presented. The WEC system forms an array, with several WECs located around a central hub to which they are each connected by a short, free-hanging power cable. The objective of the study is to analyse the dynamic characteristics and estimate the fatigue life of the power cable which is not yet in use or available on the commercial market. Hence, a novel approach is adopted in the study considering that the power cable’s length is restricted by several factors (e.g., the clearances between the service vessel and seabed and the cable), and the cable is subject to motion and loading from the WEC and to environmental loads from waves and currents (i.e., dynamic cable). The power cable’s characteristics are assessed using a numerical model subjected to a parametric analysis, in which the environmental parameters and the cable’s design parameters are varied. The results of the numerical simulations are compared and discussed regarding the responses of the power cables, including dynamic motion, curvature, cross-sectional forces, and accumulated fatigue damage. The effects of environmental conditions on the long-term mechanical life spans of the power cables are also investigated. Important cable design parameters that result in a long power cable (fatigue) service life are identified, and the cable service life is predicted. This study contributes a methodology for the first-principle design of WEC cables that enables the prediction of cable fatigue life by considering environmental conditions and variations in cable design parameters.
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| 20. |
- Kersten, Anton, 1991
(author)
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Modular Battery Systems for Electric Vehicles based on Multilevel Inverter Topologies - Opportunities and Challenges
- 2021
-
Doctoral thesis (other academic/artistic)abstract
- Modular battery systems based on multilevel inverter (MLI) topologies can possibly overcome some shortcomings of two-level inverters when used for vehicle propulsion. The results presented in this thesis aim to point out the advantages and disadvantages, as well as the technical challenges, of modular vehicle battery systems based on MLIs in comparison to a conventional, two-level IGBT inverter drivetrain. The considered key aspects for this comparative investigation are the drive cycle efficiency, the inverter cost, the fault tolerance capability of the drivetrain and the conducted electromagnetic emissions. Extensive experiments have been performed to support the results and conclusions. In this work, it is shown that the simulated drive cycle efficiency of different low-voltage-MOSFET-based, cascaded seven-level inverter types is improved in comparison to a similarly rated, two-level IGBT inverter drivetrain. For example, the simulated WLTP drive cycle efficiency of a cascaded double-H-bridge (CDHB) inverter drivetrain in comparison to a two-level IGBT inverter, when used in a small passenger car, is increased from 94.24% to 95.04%, considering the inverter and the ohmic battery losses. In contrast, the obtained efficiency of a similar rated seven-level cascaded H-bridge (CHB) drivetrain is almost equal to that of the two-level inverter drivetrain, but with the help of a hybrid modulation technique, utilizing fundamental selective harmonic elimination at lower speeds, it could be improved to 94.85%. In addition, the CDHB and CHB inverters’ cost, in comparison to the two-level inverter, is reduced from 342€ to 202€ and 121€, respectively. Furthermore, based on a simple three-level inverter with a dual battery pack, it is shown that MLIs inherently allow for a fault tolerant operation. It is explained how the drivetrain of a neutral point clamped (NPC) inverter can be operated under a fault condition, so that the vehicle can drive with a limited maximum power to the next service station, referred to as limp home mode. Especially, the detection and localization of open circuit faults has been investigated and verified through simulations and experiments. Moreover, it is explained how to measure the conducted emissions of an NPC inverter with a dual battery pack according to the governing standard, CISPR 25, because the additional neutral point connection forms a peculiar three-wire DC source. To separate the measured noise spectra into CM, line-DM and phase-DMquantities, two hardware separators based on HF transformers are developed and utilized. It is shown that the CM noise is dominant. Furthermore, the CM noise is reduced by 3dB to 6dB when operating the inverter with three-level instead of two-level modulation.
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| 21. |
- Wang, S., et al.
(author)
-
Operational reliability of multi-energy customers considering service-based self-scheduling
- 2019
-
In: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 254
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Journal article (peer-reviewed)abstract
- The developments of energy storage and substitution techniques have made it possible for customers to self-schedule their energy consumption behaviors, to better satisfy their demands in response to uncertain supply conditions. The interdependency of multiple energies, the chronological characteristics, and uncertainties in the self-scheduling context bring about additional complexities to secure the reliable energy requirements of multi-energy customers. As a necessary and challenging task, the operational reliability of multi-energy customers is tackled in this paper. Considering that the consumed energies eventually come down to the energy-related services, the self-scheduling of multi-energy customers is implemented from the perspective of specific energy-related services rather than energy carriers. Firstly, an optimal self-scheduling model for multi-energy customers is developed with the consideration of chronological service curtailment, service shifting and possible failures during service shifting. In the optimal self-scheduling model, the costs of service curtailment and shifting are formulated based on the proposed evaluation method. The time-sequential Monte Carlo simulation approach is applied to model the chronological volatilities of multi-energy demands over the entire study period, embedded with a scenario reduction technique to reduce the computational efforts. Taking full account of the possible scenarios, the quantitative reliability indices of the multi-energy customers can be obtained. The results in test cases demonstrate that the expected energy not supplied of the multi-energy customer drops significantly by 56.32% with the self-scheduling strategy. It can be also concluded that, the self-scheduling and its inherent uncertainties do have significant impacts on the operational reliability of the multi-energy customer.
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| 22. |
- Li, Xiaojian, 1991, et al.
(author)
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Installation effects on engine design
- 2020
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Conference paper (other academic/artistic)abstract
- Increasing the engine bypass ratio is one way to improve propulsive efficiency. However, an increase in the bypass ratio (BPR) has usually been associated with an increase in the fan diameter. Consequently, there can be a notable increase in the impact of the engine installation on the overall aircraft performance. In order to achieve a better balance between those factors, it requires novel nacelle and engine design concepts. This report mainly reviews installation effects on engine design. Firstly, the installation effects assessment methods are introduced. Then, the installation effects on engine cycle design, intake design and exhaust design are sequentially reviewed.
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| 23. |
- Chiu, Justin N. W., et al.
(author)
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Industrial surplus heat storage in smart cities
- 2015
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In: ASME 2015 9th International Conference on Energy Sustainability, ES 2015, collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum. - : American Society of Mechanical Engineers. - 9780791856857
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Conference paper (peer-reviewed)abstract
- Surplus heat generated from industrial sectors amounts to between 20% and 50% of the total industrial energy input. Smart reuse of surplus heat resulted from industrial sectors and power generation companies is an opportunity to improve the overall energy efficiency through more efficient use the primary energy sources. A potential solution to tackle this issue is through use of thermal energy storage (TES) to match user demand to that of the generated surplus heat. A mobile TES (MTES) concept of transportation of industrial surplus heat from production sites to end customers has shown promising results. One commissioned demonstration project using industrial heat for swimming pool water temperature regulation in Dortmund, Germany proved the interest and attention given to this concept. In this paper, a techno-economic case study in Sweden of transportation of surplus thermal energy to district heating in smart cities is presented. The application consists of heat storage at 110°C- 130°C through the use of phase change materials (PCM) based TES, notably with use of Erythritol (90 kWh/ton) for the considered temperature range, to remote district heating network located at 48 km from the thermal energy generation site. The advantages of using latent heat based PCM are the high enthalpy density per unit volume and per unit mass, as well as the quasi-constant temperature during charging and releasing of heat. The M-TES in this study has a total storage capacity of 2.1 MWh, the optimization of charge/discharge time to the amount of stored/released energy and to that of energy transportation rate is presented in this paper. Contrary to logical thinking, it is shown through this work that under certain conditions, it is more cost-effective to operate at partial load of storage units albeit the increased number of transport trips and charge/discharge cycles.
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| 24. |
- Lv, Zhihan, Dr. 1984-, et al.
(author)
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Digital twins for secure thermal energy storage in building
- 2023
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In: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 338
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Journal article (peer-reviewed)abstract
- The purpose of this work is to explore the role of the safe and optimal scheduling of thermal energy storage systems in intelligent buildings in promoting sustainable economic development under Digital Twins (DTs) technology. Phase Change Material (PCM) has high energy density, constant temperature storage, small footprint, and long service life. Here, PCM is first placed in the indoor building structure, and the DTs technology is introduced. In the development of intelligent buildings, the data generated by the energy storage system of intelligent buildings in the real space can be mapped to the virtual space in real time for simultaneous analysis. In addition, the PCM wall structure and thermal network DTs model are designed for the intelligent building. In addition, the PCW structure is used to build a thermal energy storage and dispatch model of the smart thermoelectric building based on DTs. Finally, the model is evaluated and analyzed experimentally. The analysis of system optimization power under different schemes indicates that the scheduling operation strategy of thermal energy storage of building walls can avoid overcharging or over-discharging batteries in the microgrid and reduce battery power consumption. Besides, the building wall energy storage capacity is always in the range of 0.2 ∼ 0.8 on the all-weather scale. Moreover, the model constructed here achieves significantly lower economic costs, environmental costs, and energy costs and a better energy-saving effect than the existing model. The model built here can serve as experimental reference for further digital energy storage in intelligent buildings and comprehensive energy utilization because of its superior safety performance and lower consumption.
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| 25. |
- Mohammed, Abdullah, et al.
(author)
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Minimizing energy consumption for robot arm movement
- 2014
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In: Procedia CIRP. - : Elsevier BV. - 2212-8271 .- 2212-8271. ; 25, s. 400-405
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Conference paper (peer-reviewed)abstract
- Robots are widely used in industry due to their efficiency and high performance. Many of them are operating in the manufacturing stage of the production line where the highest percentage of energy is consumed. Therefore, their energy consumption became a major focus for many robots manufacturers and academic research groups. Nevertheless, the optimization of that consumption is still a challenging task which requires a deep understanding of the robot's kinematic and dynamic behaviors. This paper proposes an approach to develop an optimization module using Matlab® to minimize the energy consumptions of the robot's movement. With the help of Denavit-Hartenberg notation, the approach starts first by solving the inverse kinematics of the robot to find a set of feasible joint configurations required to perform the task, solving the inverse kinematics is usually a challenging step which requires in-depth analyses of the robot. The module then solves the inverse dynamics of the robot to analyze the forces and torques applied on each joint and link in the robot. Furthermore, a calculation for the energy consumption is performed for each configuration. The final step of the process represents the optimization of the calculated configurations by choosing the one with the lowest power consumption and sends the results to the robot controller. Three case studies are used to evaluate the performance of the module. The experimental results demonstrate the developed module as a successful tool for energy efficient robot path planning. Further analyses for the results have been done by comparing them with the ones from commercial simulation software. The case studies show that the optimization of the location for the target path could reduce the energy consumption effectively.
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