| 1. |
- Aslanidou, Ioanna, et al.
(författare)
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Reforming heat and power technology course structure using student feedback to enhance learning experience
- 2021
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Ingår i: International Journal of Mechanical Engineering Education. - : SAGE Publications. - 0306-4190 .- 2050-4586. ; 49:4, s. 410-434
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Tidskriftsartikel (refereegranskat)abstract
- The main outcomes of an engineering course should be for the students to achieve the educational goals, enhance their problem solving capabilities and develop essential skills for their future career. In that context, it is important to understand what motivates the students and what helps them develop an engineering mindset. This paper discusses the improvement of a course with the use of student feedback to motivate students and help them develop essential skills. The purpose of the paper is to provide insight into how different aspects of the course are linked to the students’ growth. Different activities have been integrated in the course over the past years. The effect these have on the student motivation to follow the course and develop skills, knowledge and interest in the subject is discussed through the analysis of student performance, student feedback and the experience of the lecturers. The improvements in the course based on the student feedback were received positively by the students, whose learning experience improved, even though the workload of the course was high. Their motivation to successfully complete the course has also increased through the changes in the delivery of the course and the support by the teachers. The combination of student feedback and teacher experience is key for the improvement of a course, while ensuring that the students develop their engineering knowledge. Therefore, the teachers should strike a balance between helping the students find the solution and encouraging them to think on their own in order to develop essential skills.
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| 2. |
- Aslanidou, Ioanna, et al.
(författare)
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Teaching gas turbine technology to undergraduate students in Sweden
- 2018
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Ingår i: Proceedings of the ASME Turbo Expo. - : American Society of Mechanical Engineers (ASME). - 9780791851128
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the teaching of gas turbine technology in a third-year undergraduate course in Sweden and the challenges encountered. The improvements noted in the reaction of the students and the achievement of the learning outcomes is discussed. The course, aimed at students with a broad academic education on energy, is focused on gas turbines, covering topics from cycle studies and performance calculations to detailed design of turbomachinery components. It also includes economic aspects during the operation of heat and power generation systems and addresses combined cycles as well as hybrid energy systems with fuel cells. The course structure comprises lectures from academics and industrial experts, study visits, and a comprehensive assignment. With the inclusion of all of these aspects in the course, the students find it rewarding despite the significant challenges encountered. An important contribution to the education of the students is giving them the chance, stimulation, and support to complete an assignment on gas turbine design. Particular attention is given on striking a balance between helping them find the solution to the design problem and encouraging them to think on their own. Feedback received from the students highlighted some of the challenges and has given directions for improvements in the structure of the course, particularly with regards to the course assignment. This year, an application developed for a mobile phone in the Aristotle University of Thessaloniki for the calculation of engine performance will be introduced in the course. The app will have a supporting role during discussions and presentations in the classroom and help the students better understand gas turbine operation. This is also expected to reduce the workload of the students for the assignment and spike their interest.
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| 3. |
- Campillo, Javier, 1982-, et al.
(författare)
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Battery technologies for transportation applications
- 2016
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Ingår i: Technologies and Applications for Smart Charging of Electric and Plug-in Hybrid Vehicles. - Cham : Springer International Publishing. - 9783319436517 - 9783319436494 ; , s. 151-206
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- More than a fifth of the greenhouse emissions produced worldwide come from the transport sector. Several initiatives have been developed over the last few decades, aiming at improving vehicles’ energy conversion efficiency and improve mileage per liter of fuel. Most recently, electric vehicles have been brought back into the market as real competitors of conventional vehicles. Electric vehicle technology offers higher conversion efficiencies, reduced greenhouse emissions, low noise, etc. There are, however, several challenges to overcome, for instance: improving batteries’ energy density to increase the driving range, fast recharging, and initial cost. These issues are addressed on this chapter by looking in depth into both conventional and non-conventional storage technologies in different transportation applications.
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| 4. |
- Dall'Orto, Francesco, et al.
(författare)
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Economic Aspect of Hybrid Heating and Cooling Systems in a Residential Building
- 2019
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Konferensbidrag (refereegranskat)abstract
- District heating is a well-established technology; however, the use of individual heat pumps has been expanding and is now the main competitor to district heating. The prices for both electricity and district heating often vary over time because of the variation of raw material prices in the marketplace. Consequently, for the building owner it would be cost effective if they had the possibility to integrate both district heating and heat pumps. Aiding in the flexibility to switch between the two systems in order to choose the one with the lowest operating cost throughout the year. In the presented work, the modeling and control of a detached house integrated with both district heating and a heat pump are developed. The operating costs of both systems are computed considering the marketplace prices and the coefficient of performance of the heat pump, related to the external temperature. The results show that heat pumps can be well exploited during the spring and fall to cover base loads, and in the summer can be used for ambient cooling.
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| 5. |
- Hermansson, K., et al.
(författare)
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An Automated Approach to Building and Simulating Dynamic District Heating Networks
- 2018
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Ingår i: IFAC-PapersOnLine. - : Elsevier B.V.. - 2405-8963. ; 51:2, s. 855-860
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Tidskriftsartikel (refereegranskat)abstract
- In Nordic countries, district heating accounts for a large share of the consumers’ heat demand. In Sweden, roughly 50% of the total heat demand is attributed to district heating. Which, over the past few years, is equivalent to around 50 TWh, and imposes a difficult balance between supply and demand for the suppliers of district heating. For large networks the propagation of heat from supplier to end-user can vary several hours. Further complexities of large networks, which can consist of multiple overlapping rings, is that during transient conditions the flow can actually change direction. A dynamic modeling library has been developed in Modelica using OpenModelica for district heating networks. Methods for modeling, handling data, simulating and the visualization of results has been developed using Matlab. The model has been validated using data from Mälarenergi AB, a local provider of district heating in Västerås, Sweden. The model provides to an acceptable degree in predicting the heat propagation and temperature distribution in a localized case study. Adding a higher level of robustness, the model has the capacity to handle bi-directional and reversing flows in complex ring structures. Through this work, the combination of OpenModelica and Matlab, a framework for automating the building and simulation of district heating networks is obtainable. The implications of automating network modeling from computer-aided design drawings allows for a quick robust overview of how the network is working and how prospective additions to the network could impact the end-users. Furthermore, incorporating visual aspects for heat propagation in a network contributes to a higher understanding of complex network structures.
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| 6. |
- Saletti, Costanza, et al.
(författare)
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A control-oriented scalable model for demand side management in district heating aggregated communities
- 2022
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Ingår i: Applied Thermal Engineering. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-4311 .- 1873-5606. ; 201
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Tidskriftsartikel (refereegranskat)abstract
- District heating networks have become widespread due to their ability to distribute thermal energy efficiently, which leads to reduced carbon emissions and improved air quality. Additional benefits can derive from novel demand side management strategies, which can efficiently balance demand and supply. However, their implementation requires detailed knowledge of heating network characteristics, which vary remarkably depending on urban layout and system amplitude. Moreover, extensive data about the energy distribution and thermal capacity of different areas are seldom available. For this purpose, the present work proposes a novel procedure to develop a fast scale-free model of large-scale district heating networks for system optimization and control. Each network community is represented and modeled as an aggregated region. Its physics-based model is identified starting from a limited amount of data available at the main substations and includes heat capacity and heat loss coefficients. The procedure is demonstrated and validated on the network of Va center dot steras, Sweden, showing results that are in agreement with data from the literature. Thus, the model is well suited for real-time optimization and predictive control. In particular, the possibility to easily estimate the heat storage potential of network communities allows demand side management solutions to be applied in several conditions.
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| 7. |
- Saletti, Costanza, et al.
(författare)
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Enabling smart control by optimally managing the State of Charge of district heating networks
- 2021
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Ingår i: Applied Energy. - : ELSEVIER SCI LTD. - 0306-2619 .- 1872-9118. ; 283
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Tidskriftsartikel (refereegranskat)abstract
- Digitalization and smart control of district heating networks are emerging as key features to make these systems flexible and optimal. However, since effective and scalable methods for large-scale systems are currently unavailable, the implementation of smart controllers can be challenging and time-consuming. This is addressed herein by proposing a novel approach to include the thermal capacity of the connected buildings in the optimal control of large-scale heating networks. A reduced-order model of the aggregated communities supplied by a large-scale network is used to define their State of Charge, which is exploited to store or retrieve energy when convenient, while maintaining indoor comfort. This concept is included in a Model Predictive Controller that optimizes power plant management and heat distribution. The results show that the controller successfully shaves heat supply peaks to different regions up to 16% and reduces the difference between distribution and soil temperature up to 20%. At the same time, the return temperature is kept close to the set-point of 35 degrees C, which is lower than the historical operation and further reduces distribution heat losses. The procedure can be easily replicated to optimize systems of different sizes and to support their transition to efficient, smart district heating networks.
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| 8. |
- Zimmerman, Nathan, 1983-, et al.
(författare)
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Achieving lower district heating network temperatures using feed-forward MPC
- 2019
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Ingår i: Materials. - : MDPI AG. - 1996-1944 .- 1996-1944. ; 12:15
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Tidskriftsartikel (refereegranskat)abstract
- The focus of this work is to present the feasibility of lowering the supply and return temperatures of district heating networks in order to achieve energy savings through the implementation of feed-forward model predictive control. The current level of district heating technology dictates a need for higher supply temperatures, which is not the case when considering the future outlook. In part, this can be attributed to the fact that current networks are being controlled by operator experience and outdoor temperatures. The prospects of reducing network temperatures can be evaluated by developing a dynamic model of the process which can then be used for control purposes. Two scenarios are presented in this work, to not only evaluate a controller's performance in supplying lower network temperatures, but to also assess the boundaries of the return temperature. In Scenario 1, the historical load is used as a feed-forward signal to the controller, and in Scenario 2, a load prediction model is used as the feed-forward signal. The findings for both scenarios suggest that the new control approach can lead to a load reduction of 12.5% and 13.7% respectively for the heat being supplied to the network. With the inclusion of predictions with increased accuracy on end-user demand and feed-back, the return temperature values can be better sustained, and can lead to a decrease in supply temperatures and an increase in energy savings on the production side.
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| 9. |
- Zimmerman, Nathan, 1983-, et al.
(författare)
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Agglomeration Detection in Circulating Fluidized Bed Boilers Using Refuse Derived Fuels
- 2016
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Ingår i: 2016 9th EUROSIM Congress on Modelling and Simulation. - : IEEE Computer Society. - 9781509041190 ; , s. 123-128
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Konferensbidrag (refereegranskat)abstract
- The formation of agglomerates in a refuse derived fuel (RDF) fired circulating fluidized bed (CFB) boiler has been investigated by implementing a dynamic model of the combustion process. The nature of refuse derived fuel, which is complex in composition, leads to an increased tendency for agglomerate formation. Notwithstanding the fact that a robust control scheme is essential in preventing the decrease in boiler efficiency from accelerated agglomerate formation. Therefore, a mechanism for detecting agglomeration through a physical model by looking at the minimum fluidization is presented. As agglomerates form between the fuel ash and bed sand the average diameter of the sand will increase and therefore the minimum fluidization velocity. Samples of bed material have been sieved and measured from a 150MW circulating fluidized bed boiler fired with refuse derived fuel to determine bed material size distribution. The findings have been correlated and match an increase in the minimum fluidization velocity during a seven day sampling period where the bed material size distribution increases above the average sand diameter.
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| 10. |
- Zimmerman, Nathan, 1983-
(författare)
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Modelling Towards Control of Dynamic Systems : Applications on RDF Fired CFB Performance and DHN Distribution
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The combination of global warming along with increasing energy demand necessitates the importance of improving processes pertaining to the production and consumption of energy in combined heat and power plants. This thesis brings to light transient factors currently burdening process performance for circulating fluidized bed boilers (CFBs) combusting refuse derived fuels (RDFs) and district heating networks (DHN). These two domains are not completely disconnected from one another, which is the case for Northern European countries. Heat can be generated from a central location to be distributed through a network of customers to meet a heating demand. Results show that first-principle modelling techniques have the capacity to capture transients factors associated within the aforementioned entwined energy systems.On the production side, obtaining real-time information pertaining to the lower heating value of refuse derived fuel affords the ability to implement feed-forward model predictive control. Therefore, feed-forward model predictive control has the potential to minimize combustion temperature swings by making the necessary controls moves before changes in the fuel’s composition are actualized by the process. On the consumption side, attaining a deeper understanding of district heating network dynamics, e.g. heat propagation, network losses, distribution delays, and end-user requirements, introduces the possibility to analyse network performance and reduce peak load production. The perspective of quick network performance can be achieved by an automated approach to building and simulating district heating networks. Nonconventional end-user heating configurations, e.g. homes utilizing district heating and a heat pump, has the potential of illustrating how heating consumption patterns may change over time. Peak load reduction is achievable in district heating networks when it is possible to reduce network supply temperature. This can be achieved by predicting end-user heating requirements and using this information for feed-forward model predictive control.The overall observations made in this thesis demonstrates that process improvements are obtainable for transient energy systems. Despite the presented work focusing on only one type of energy production and one type of consumption, the approach described unlocks a flexibility that eliminates the need for unambiguous modelling and simulations by allowing for the reusability of model components. The exportability of these models further distinguishes them, as they can be used to test new control approaches within an energy system as real-time predictions within each energy sub-system become more accessible.
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