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  • 51.
    Hermansson, Caroline
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Bergkvist, Karolina
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Är off-grid framtiden för det svenska elsystemet?: En analys utifrån Flernivå-perspektivet2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Syftet med detta examensarbete är att studera om scenariot off-grid är en potentiell riktning i framtidens svenska energilandskap, samt undersöka vad som kan driva en sådan utveckling.

    För detta examensarbete har en kvalitativ forskningsstrategi tillämpats, genom ett abduktivt förhållningssätt till funnen empiri och teori. En empirisk datainsamling har genomförts i form av semistrukturerade intervjuer med ett tiotal aktörer på den svenska elnätsmarknaden. Därefter har en tematisk analys utförts, där det empiriska materialet ställts mot teori.

    Studien påvisar att det idag finns flertalet faktorer som kan vara drivande för en utveckling mot ett off-grid elsystem. I studiens empiriska material går det att finna tecken på att flertalet informanter tror att en förändring av dagens svenska elsystem behövs. Dock hur troligt det är, att en sådan förändringsprocess sker, finner studien inga belägg eller grunder för. De faktorer som skulle driva utvecklingen mot ett elsystem som karaktäriseras som off-grid kan identifieras som prisutveckling, utveckling i andra sektorer, ändrad tariffsättning, decentralisering, lagstiftning, ökad popularitet samt exempel där off-grid har realiserats.

  • 52.
    Herre, Lars
    et al.
    Kungliga Tekniska Högskolan (KTH), Sweden.
    Kovala, Tommy
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Industriell ekonomi och organisation.
    Söder, Lennart
    Kungliga Tekniska Högskolan (KTH), Sweden.
    Papahristodoulou, Christos
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Industriell ekonomi och organisation.
    ON THE FLEXIBILITY OF ELECTRICTY CONSUMERS: Modelling, Quantification and Analysis of Notice Time2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Power systems with a large share of inherently intermittent renewable energy sources require new approaches to system operation. Demand response is seen as a potential possibility for contributing to maintaining power balance in a future energy system with large amounts of volatile renewable energy generation (Bartusch et al., 2011; Torriti, Hassan & Leach, 2010). It would be a measure to reduce costs for maintaining the power balance, which is believed to become more expensive if traditional measures is to handle the increasing intermittency (Albadi & El-Saadany, 2008; Kirschen, 2003; Siano, 2014). The study of the flexibility of electricity demand is an essential key to exploring the current and future potential of demand side response for power system services.  

    For both solar and wind power, forecasts for several hours ahead may have a lower accuracy. Statistically, the forecasts become better the closer they approach real operation. In practice however, this does not happen in each case. This means that the flexibility need for a certain hour will be different, depending on when the need is identified, i.e. different notice times.

    For consumers to be flexible, there are several parameters that impact their ability and willingness to react to incentives with a change of load. Elasticity (self- and cross-elasticity) has been defined in literature to describe consumer flexibility with respect to a change of electricity price and is often referred to when modelling the flexibility of consumers (Albadi & El-Saadany, 2008; Lijesen, 2007). Flexibility with respect to electricity prices or other financial incentives has been widely studied in literature on smart grids and demand response.

    Another important parameter for electric demand to be flexible is the notice time, i.e. the time span between informing the consumer about a future need for reorganizing their consumption and providing a change of consumption as a system service. The impact of notice time on the flexibility of electricity consumers has not yet been systematically researched. It is logical that the willingness and ability of certain consumers to provide flexibility decreases as notice time becomes shorter. There are, however, some loads that even may become more flexible, the shorter the notice time, such as e.g. the charging of electric vehicles.  

    An essential basis for flexible consumers is the communication infrastructure that is used for sending price signals, bids and further market parameters depending on the demand response program. The type and information content of such communication is enabled through technological devices. These smart devices – which in most cases must exceed the function of only smart metering (Siano, 2014) – can have different properties and requirements that are determined by the demand response program and its respective requirements on data exchange. Therefore, the technological implementation and the impact of the limitations originating from the same are discussed in this study as well.  

    For a quantitative analysis of customer flexibility, both price and notice time are imperative parameters. Former has been studied in numerous references (Bartusch et al., 2011; Gyamfi, Krumdieck & Urmee, 2013; Kirschen et al., 2000; Lijesen, 2007) whereas the impact of the latter has not yet been examined in depth. In this paper, a study on consumer flexibility with respect to notice time is presented. It is analyzed how the ability to reschedule electricity demand during a time interval in the future is impacted by terms of notifying and updating flexible consumers. For this, a market and demand response program optimizing social welfare is developed that allows for an analysis of notice time dependent consumers.

  • 53.
    Honnanayakanahalli Ramakrishna, Prajwal
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    MODELING, SIMULATION AND OPTIMIZATION OF A SUBMERGED RENEWABLE STORAGE SYSTEM INTEGRATED TO A FLOATING WIND FARM: A feasibility case study on the Swedish side of the Baltic sea, based on the geographical and wind conditions2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Mathematical modeling and simulations of a submerged renewable storage system integrated to a wind farm, chosen based on the geographical and wind conditions at the Baltic Sea, gives insight on the feasibility of the submerged renewable storage and an approximation of the payback period and profits that could be generated. Genetic Algorithms were used to obtain the optimal number of spheres for a certain depth, based on 2 objective functions I.e. Minimum Life Cycle Cost (LCC) and maximum reduction in wind curtailment. The new arrangement concept shows that the Initial Capital Cost (ICC) could be decreased by 25% to 60% depending upon the number of sphere employed. Based on the inputs considered in the study, the results prove that the submerged renewable storage system would be feasible, and the profits ranging from 15 Million Euro to 29 Million Euro can be achieved at the chosen location, towards the Swedish side of the Baltic sea. Although, in a real life scenario it is assumed that only up to half of the profits obtained in the results would be achievable. The results also show that, the Pump/Turbine with a high turbine efficiency and lower pump efficiency, generated better profits, compared to a Pump/Turbine running with a higher pump efficiency and lower turbine efficiency. An attempt to increase the round-trip efficiency by adding a multi stage submersible pump, resulted in additional ICC and LCC, which saw a decrease in profits. 

  • 54.
    Ilic, Danica Djuric
    et al.
    Linköping University.
    Dotzauer, Erik
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Trygg, Louise
    Linköping University.
    District heating and ethanol production through polygeneration in Stockholm2012Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 91, nr 1, s. 214-221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ethanol can be produced with little impact on the environment through the use of polygeneration technology. This paper evaluates the potential of integrating a lignocellulosic ethanol plant into a district heating system by case study; the plant has an ethanol capacity of 95MW with biogas, electricity and heat as by-products. Stockholm's district heating system is used as the case study, but the results may be relevant also for other urban areas. The system has been studied using MODEST - an optimisation model framework. The results show that introducing the plant would lead to a significant reduction in the cost of heat production. The income from the biofuels and electricity produced would be about €76million and €130million annually, respectively, which is an increase of 70% compared to the income from the electricity produced in the system today. Assuming that the electricity produced will replace marginal electricity on the European electricity market and that the biofuel produced will replace gasoline in the transport sector, the introduction of the polygeneration plant in the district heating system would lead to a reduction of global CO2 emissions of about 0.7million tonnes annually

  • 55.
    Jahn, Tobias
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Solar-Driven Distributed Heating System: Upgrading a 200 kW Solar-driven Organic Rankine Cycle Unit for Distributed Heating2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The University of Tianjin, China is working on a 200 kW solar-driven Organic Rankine Cycle (ORC) plant. Due to difficulties with Chinese energy regulations and legislation, the plant will not be connected to the grid for electricity generation. The university intents therefore to use the solar system for distributed heating at times without ongoing experiments. Since no heat consumer was designated initially, the heating purpose resulting in the most cost-effective usage of the already purchased components was sought. In this context, the plant’s performance in four different heating scenarios was assessed to determine the necessary upgrades, which led to the optimized Levelized Costs of Energy (LCOE). The upgrades considered a thermal energy storage system (TESS), extension of heat exchanger (HE) capacity and redesign of the HE’s hot fluid outlet temperature (HFOT). Scenario 1 (S1) represents the current system on-site for space heating and cooling. The system has been upgraded with a TESS and the HFOT was lowered. Scenario 2 (S2) differs from S1 by also considering upgrading of the HE capacity. In S1, the LCOE for the optimized system based on the original HE capacity and heat demand are shown, whereas the LCOE for S2 indicate the minimum LCOE possible with an optimized system for an increased space heating and cooling demand. In scenario 3 (S3) and 4 (S4), the optimized LCOE of the system used for industrial heat loads was studied. The industrial heat load was assumed to be constant. Two durations were chosen: 24 hours and 7 days a week (24/7) and 16 hours and 7 days a week (16/7) according to a factory working in a three-shift and two-shift system, respectively. In order to obtain the optimized LCOE, the parabolic trough collector (PTC) field and TESS were modeled and simulated in TRNSYS and MATLAB, respectively. For S1 the minimum LCOE of 0.187 $/kWh is achieved providing that none of the analyzed upgrades are made to the current system. In S2 the minimum LCOE of 0.145 $/kWh is obtained at 750 kW HE capacity, 10 m³ TESS and 50°C HFOT. In this setup, the HE capacity is large enough to utilize nearly all solar energy immediately. For S3, the lowest LCOE of 0.106 $/kWh was obtained at 80 kW HE and 40 m³ TESS and for S4, it was 0.098 $/kWh at 130 kW HE and 30 m³ TESS. Based on those results, the following main conclusions are drawn: (1) the low degrees of utilization of the plant in S1 and S2 led to high LCOE which are not competitive with those for traditional heating with air conditioners (0.112 $/kWh), (2) the LCOE can be optimized when the system provides heat continually throughout the year as required, for instance, by industrial processes and (3) for a system with optimized LCOE, the CO2 reductions associated to the upgrades are below 6% for space heating and cooling and 55 – 65% for industrial process heat.

  • 56.
    Johansson, Joakim
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Optimization of Section Points Locations in Electric Power Distribution Systems: Development of a Method for Improving the Reliability2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The power distribution system is the final link to transfer the electrical energy to the individual customers. It is distributed in a complex technical grid but is associated with the majority of all outages occurring. Improving its reliability is an efficient way to reduce the effects of outages.

    A common way of improving the reliability is by designing loop structures containing two connected feeders separated by a section point. The location of the section point will decide how the system structure is connected and its level of reliability. By finding the optimal location, an improved reliability may be accomplished.

    This Master’s thesis has developed a method of finding optimized section points locations in a primary distribution system in order to improve its reliability. A case study has been conducted in a part of Mälarenergi Elnät’s distribution system with the objective of developing an algorithm in MATLAB able to generate the optimal section points in the area. An analytical technique together with a method called Failure Modes and Effect Analysis (FMEA) as preparatory step, was used to simulate the impact of outages in various components based on historical data and literature reviews. Quantifying the impact was made by calculating the System Average Interruption Duration Index (SAIDI) and the Expected Cost (ECOST) which represented the reliability from a customer- and a socio-economic perspective.

    Using an optimization routine based on a Greedy algorithm an improvement of the reliability was made possible. The result of the case study showed a possible improvement of 28% on SAIDI and 41% on ECOST if optimizing the location of section points. It also indicated that loop structures containing mostly industry-, trade- and service-sectors may improve ECOST considerably by having a relocated section point.

    The analysis concluded that based on the considerable improvement the case study showed, a distribution system could be highly benefitted by optimizing the location of section points. The created algorithm may provide a helpful tool well representative for such a process in a cost-effective way. Applying it into a full size system was considered being possible but it would first require some additional improvements of reliability inputs and to resolve some fundamental issues like rated current in lines and geographical distances to substations. 

  • 57.
    Jurasz, Jakob
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. Faculty of Management, Department of Engineering Management, AGH University, Cracow, Poland.
    Canales, F. A.
    Department of Civil and Environmental, Universidad de la Costa, Barranquilla, Atlántico, Colombia.
    Kies, A.
    Frankfurt Institute for Advanced Studies, Goethe University Frankfurt, Frankfurt am Main, Germany.
    Guezgouz, M.
    Department of Electrical Engineering, Mostaganem University, Mostaganem, Algeria.
    Beluco, A.
    Instituto de Pesquisas Hidráulicas, Universidade Federal do Rio Grande do Sul, Brazil.
    A review on the complementarity of renewable energy sources: Concept, metrics, application and future research directions2020Inngår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 195, s. 703-724Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Global and regional trends indicate that energy demand will soon be covered by a widespread deployment of renewable energy sources. However, the weather and climate driven energy sources are characterized by a significant spatial and temporal variability. One of the commonly mentioned solutions to overcome the mismatch between demand and supply provided by renewable generation is a hybridization of two or more energy sources into a single power station (like wind-solar, solar-hydro or solar-wind-hydro). The operation of hybrid energy sources is based on the complementary nature of renewable sources. Considering the growing importance of such systems and increasing number of research activities in this area this paper presents a comprehensive review of studies which investigated, analyzed, quantified and utilized the effect of temporal, spatial and spatiotemporal complementarity between renewable energy sources. The review starts with a brief overview of available research papers, formulates detailed definition of major concepts, summarizes current research directions and ends with prospective future research activities. The review provides a chronological and spatial information with regard to the studies on the complementarity concept.

  • 58.
    Kamal, Majd
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Potential for low temperature district heating system: Integrating 4th generation district heating system with existing technology2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This project presents a feasibility study and an investigation of the potential for low temperature district heating system in Västerås. The investigation treats integrations possibilities for 4GDH (4th Generation District Heating) in Kungsängens area in Västerås, which is undergoing a large-scale building-up and construction.  The study is conducted for the company Mälarenergi AB. The advantages of 4GDH technology are identified and analyzed, where energy effectiveness and economic benefits aspects were concluded. Problems with existing technology and higher cooling demand expectations drive 4GDH to be an interesting and necessary technology in the future. Four Different integration solutions between old and new networks are presented, analyzed and discussed. Quantitative analysis conducted where initial cost for the four technical solutions were estimated and compared. The results show that low temperature district heating could lead to reduction in the initial cost for the network by using PEX instead of steel as pipe material. The results show also that one solution using heat exchanger as exchange stations has the lowest cost between the four solutions. The results show that the cost for the retention flow that is linked with 4GDH stands for 20%-30% of the total cost. The importance of the retention flow pipe is investigated using two physical models in OpenModelica and Excel, where simulations were conducted. It is concluded that it is possible to provide Kungsängen area with low temperature district heating without having the retention flow pipe. Three parameters were identified to be critical which are, geographical placement of the consumers, pattern variation for the heat demand and heat systems installed inside consumer’s buildings. The results show also that it might be critical to have a variate and optimized supply temperature for the area, depending on the demand. The simulations of a fictive area that could present a future heat demand for Kungsängen area shows that a temperature of 55°C is satisfying during winter season where the demand is high and a temperature between 60-65°C must be available during spring/autumn seasons and specially during summer. The variation depends directly on the temperature drop through the supply pipes to the consumers. The temperature drop is directly linked with water velocity inside the pipes. The losses increase during summer nights when the heat demand is low which lead to low water velocities. 

  • 59.
    Kos, Cristoffer
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Hermansson, Kristoffer
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    BUILDING AND SIMULATING DYNAMIC MODELS OF DISTRICT HEATING NETWORKS WITH MODELICA: Using Matlab to process data and automate modelling and simulation2017Independent thesis Advanced level (degree of Master (Two Years)), 300 hpOppgave
    Abstract [en]

    District heating systems are common in Nordic countries today and accounts for a great portion of the heat demand. In Sweden, total district heating end use in the last years has been around 50 TWh and district heating accounts for roughly 50 % of the total heat demand. Suppliers of district heating must balance demand and supply, often in large and complex networks. Heat propagation can be in the range of hours and it is not known in detail how the heat will propagate during transient conditions. A dynamic model has been developed in OpenModelica and a method for modeling, handling data, simulating and visualizing the results of a district heating network was developed using Matlab as core. Data from Mälarenergi AB, a district heating producer and grid operator, was used for validation of the model. Validation shows that the model works well in predicting heat propagation and temperature distribution in the network and that the model can be scaled up to a large number of heat exchangers and pipes. The model is robust and can handle bi-directional and reversing flows in complex ring structures. It was concluded that OpenModelica together with Matlab is a good combination for creating models of district heating networks, as a high degree of standardization and automation can be achieved. This, together with visualization of the heat propagation, makes it useful for the understanding of the district heating network during transient conditions.

  • 60.
    Kovala, Tommy
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Industriell ekonomi och organisation.
    Flexibla elkunders roll i ett framtida förnybart kraftsystem: Hur kommer framtidens elkunder besluta om sin elanvändning?2016Konferansepaper (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Erbjud elkunderna rätt service!

    Framtidens elkunder kommer möta ett bredare utbud av tjänster, avtal och produktpaket som bland annat ska kunna uppmuntra en högre grad av efterfrågeflexibilitet. En av flera viktiga aspekter för hur elkunderna kommer agera, är marknadens signal för efterfrågeflexibilitet. Bland annat är elkundernas möjlighet att planera och förbereda sin flexibilitet en mycket intressant variabel för den framtida efterfrågeflexibilitetens potential.

  • 61.
    Kovala, Tommy
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    This electricity price is too high for my household: Why are some households sensitive to the electricity price, when others barely are sensitive at all?2017Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The key-solution for a sustainable electricity system is demand flexibility. If we use technology to distribute the information, demand flexibility could be incentivized by dynamic pricing, so that real problems and costs in the electricity system become transparent for electricity consumers.

    Utilities and electricity retailers have tried to offer such contracts before, but deemed the necessary educative interventions for consumers too expensive and retreated to nominal price competition (Flaim et al., 2013). Using a questionnaire, collecting intentions for demand flexibility, we reveal that lacking knowledge is just one of many areas that could be targeted with interventions.

  • 62.
    Kyprianidis, Konstantinos
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    On the trade-off between aviation NOx and energy efficiency2017Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 185, s. 1506-1516Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study aims to assess the trade-off between the ever-increasing energy efficiency of modern aero-engines and their   performance. The work builds on performance models previously developed to optimise the specific fuel consumption of future aero-engine designs. As part of the present work a simple and adaptable   emissions correlation for Rich-burn Quick-quench Lean-burn combustor designs is derived. The proposed model is computationally inexpensive and sufficiently accurate for use in aero-engine multi-disciplinary conceptual design tools. Furthermore, it is possible to adapt the correlation to model the   emissions of combustors designed for very aggressive future cycles. An approach to lean-burn combustor   emissions modelling is also presented. The simulation results show that improving engine propulsive efficiency is likely to have a benign effect on  emissions at high altitude; at sea-level conditions   emissions are particularly likely to reduce. Improving engine thermal efficiency however has a detrimental effect on   emissions from RQL combustors, both at high altitude and particularly at sea-level conditions. LDI combustor technology does not demonstrate such behaviour. Current legislation permits trading   emissions engine efficiency and hence reduce   emissions. If we are to reduce the contribution of aviation to global warming, however, future certification legislation may need to become more stringent and comprehensive.

  • 63.
    Kyprianidis, Konstantinos G.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. Cranfield University.
    Future Aero Engine Designs: An Evolving Vision2011Inngår i: Advances in Gas Turbine Technology / [ed] Ernesto Benini, Rijeka, Croatia: InTech, 2011, 1st, s. 3-24Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 64.
    Kyprianidis, Konstantinos G.
    Cranfield University, UK.
    Multi-Disciplinary Conceptual Design of Future Jet Engine Systems2010Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis describes various aspects of the development of a multi-disciplinary aero engine conceptual design tool, TERA2020 (Techno-economic, Environmental and Risk Assessment for 2020), based on an explicit algorithm that considers: engine performance, engine aerodynamic and mechanical design, aircraft design and performance, emissions prediction and environmental impact, engine and airframe noise, and production, maintenance and direct operating costs.

    As part of this research effort, a newly-derived semi-empirical NOx correlation for modern rich-burn single-annular combustors is proposed. The development of a numerical methods library is also presented, including an improved gradient-based algorithm for solving non-linear equation systems. Common assumptions made in thermo-fluid modelling for gas turbines and their effect on caloric properties are investigated, while the impact of uncertainties on performance calculations and emissions predictions at aircraft system level is assessed. Furthermore, accuracy limitations in assessing novel engine core concepts as imposed by current practice in thermo-fluid modelling are identified.

    The TERA2020 tool is used for quantifying the potential benefits from novel technologies for three low pressure spool turbofan architectures.  The impact of failing to deliver specific component technologies is quantified, in terms of power plant noise and CO2 emissions. To address the need for higher engine thermal efficiency, TERA2020 is again utilised; benefits from the potential introduction of heat-exchanged cores in future aero engine designs are explored and a discussion on the main drivers that could support such initiatives is presented. Finally, an intercooled core and conventional core turbofan engine optimisation procedure using TERA2020 is presented. A back-to-back comparison between the two engine configurations is performed and fuel optimal designs for 2020 are proposed.

    Whilst the detailed publications and the work carried out by the author, in a collaborative effort with other project partners, is presented in the main body of this thesis, it is important to note that this work is supported by 20 conference and journal papers.

  • 65.
    Kyprianidis, Konstantinos G.
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. Cranfield University.
    Sethi, Vishal
    Cranfield University.
    Ogaji, Stephen O. T.
    Cranfield University.
    Pilidis, Pericles
    Cranfield University.
    Singh, Riti
    Cranfield University.
    Kalfas, Anestis I.
    Aristotle University of Thessaloniki.
    Thermo-Fluid Modelling for Gas Turbines-Part I: Theoretical Foundation and Uncertainty Analysis2009Inngår i: ASME TURBO EXPO 2009 Proceedings, GT2009-60092, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this two-part publication, various aspects of thermo-fluidmodelling for gas turbines are described and their impact onperformance calculations and emissions predictions at aircraftsystem level is assessed. Accurate and reliable fluid modellingis essential for any gas turbine performance simulation softwareas it provides a robust foundation for building advanced multidisciplinarymodelling capabilities. Caloric properties forgeneric and semi-generic gas turbine performance simulationcodes can be calculated at various levels of fidelity; selection ofthe fidelity level is dependent upon the objectives of thesimulation and execution time constraints. However, rigorousfluid modelling may not necessarily improve performancesimulation accuracy unless all modelling assumptions andsources of uncertainty are aligned to the same level. Certainmodelling aspects such as the introduction of chemical kinetics,and dissociation effects, may reduce computational speed andthis is of significant importance for radical space explorationand novel propulsion cycle assessment.

    This paper describes and compares fluid models, based ondifferent levels of fidelity, which have been developed for anindustry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles.The latter comprises the following modules: engineperformance, aircraft performance, emissions prediction, andenvironmental impact. The work presented aims to fill thecurrent literature gap by: (i) investigating the commonassumptions made in thermo-fluid modelling for gas turbinesand their effect on caloric properties and (ii) assessing theimpact of uncertainties on performance calculations andemissions predictions at aircraft system level.

    In Part I of this two-part publication, a comprehensiveanalysis of thermo-fluid modelling for gas turbines is presentedand the fluid models developed are discussed in detail.Common technical models, used for calculating caloricproperties, are compared while typical assumptions made influid modelling, and the uncertainties induced, are examined.Several analyses, which demonstrate the effects of composition,temperature and pressure on caloric properties of workingmediums for gas turbines, are presented. The working mediumsexamined include dry air and combustion products for variousfuels and H/C ratios. The errors induced by ignoringdissociation effects are also discussed.

  • 66.
    Kyprianidis, Konstantinos G.
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. Cranfield University.
    Sethi, Vishal
    Cranfield University.
    Ogaji, Stephen O. T.
    Cranfield University.
    Pilidis, Pericles
    Cranfield University.
    Singh, Riti
    Cranfield University.
    Kalfas, Anestis I.
    Aristotle University of Thessaloniki.
    Thermo-Fluid Modelling for Gas Turbines-Part II: Impact on Performance Calculations and Emissions Predictions at Aircraft System Level2009Inngår i: ASME TURBO EXPO 2009 Proceedings, GT-2009-60101, 2009, s. 483-494Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this two-part publication, various aspects of thermo-fluidmodelling for gas turbines are described and their impact onperformance calculations and emissions predictions at aircraftsystem level is assessed. Accurate and reliable fluid modellingis essential for any gas turbine performance simulation softwareas it provides a robust foundation for building advanced multidisciplinarymodelling capabilities. Caloric properties forgeneric and semi-generic gas turbine performance simulationcodes can be calculated at various levels of fidelity; selection ofthe fidelity level is dependent upon the objectives of thesimulation and execution time constraints. However, rigorousfluid modelling may not necessarily improve performancesimulation accuracy unless all modelling assumptions andsources of uncertainty are aligned to the same level. Certainmodelling aspects such as the introduction of chemical kinetics,and dissociation effects, may reduce computational speed andthis is of significant importance for radical space explorationand novel propulsion cycle assessment.

    This paper describes and compares fluid models, based ondifferent levels of fidelity, which have been developed for anindustry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles.The latter comprises the following modules: engineperformance, aircraft performance, emissions prediction, andenvironmental impact. The work presented aims to fill thecurrent literature gap by: (i) investigating the commonassumptions made in thermo-fluid modelling for gas turbinesand their effect on caloric properties and (ii) assessing theimpact of uncertainties on performance calculations andemissions predictions at aircraft system level.

    In Part II of this two-part publication, the uncertaintyinduced in performance calculations by common technicalmodels, used for calculating caloric properties, is discussed atengine level. The errors induced by ignoring dissociation areexamined at 3 different levels: i) component level, ii) enginelevel, and iii) aircraft system level. Essentially, an attempt ismade to shed light on the trade-off between improving theaccuracy of a fluid model and the accuracy of a multidisciplinarysimulation at aircraft system level, againstcomputational time penalties. The results obtained demonstratethat accurate modelling of the working fluid is not alwaysessential; the accuracy/uncertainty for an overall engine modelwill always be better than the mean accuracy/uncertainty of the individual component estimates as long as systematic errors arecarefully examined and reduced to acceptable levels to ensureerror propagation does not cause significant discrepancies.Computational time penalties induced by improving theaccuracy of the fluid model as well as the validity of the idealgas assumption for future turbofan engines and novelpropulsion cycles are discussed.

  • 67.
    Kyprianidis, Konstantinos
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. Cranfield University, UK.
    Nalianda, Devaiah
    Cranfield University, UK.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    A NOx Emissions Correlation for Modern RQL Combustors2015Inngår i: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 75, s. 2323-2330Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study begins with a review of existing emissions prediction methodologies for Rich-burn Quick-quench Lean-burn combustors. The need for a simple and adaptable NOx emissions correlation for such combustor designs as used in state-of-the-art civil turbofan engines is discussed. The derivation of a new correlation is consequently presented. The proposed model is computationally inexpensive and sufficiently accurate for use in aero-engine multi-disciplinary conceptual design tools. Furthermore, it is possible to adapt the correlation to model the NOx emissions of combustors designed for very aggressive future cycles. A case study is presented focusing on the NOx performance of advanced future cycles relative to current and future certification limits.

  • 68.
    Kyprianidis, Konstantinos
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. Cranfield University.
    Rolt, Andrew M.
    Rolls-Royce plc.
    Sethi, Vishal
    Cranfield University.
    On Intercooled Turbofan Engines2013Inngår i: Progress in Gas Turbine Performance / [ed] Ernesto Benini, Rijeka, Croatia: InTech, 2013, 1st, , s. 268s. 3-24Kapittel i bok, del av antologi (Fagfellevurdert)
  • 69.
    Kyprianidis, Konstantinos
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Skvaril, JanMälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Developments in Combustion Technology2016Collection/Antologi (Fagfellevurdert)
    Abstract [en]

    Over the past few decades, exciting developments have taken place in the field of combustion technology. The present edited volume intends to cover recent developments and provide a broad perspective of the key challenges that characterize the field. The target audience for this book includes engineers involved in combustion system design, operational planning and maintenance. Manufacturers and combustion technology researchers will also benefit from the timely and accurate information provided in this work. The volume is organized into five main sections comprising 15 chapters overall: - Coal and Biofuel Combustion - Waste Combustion - Combustion and Biofuels in Reciprocating Engines - Chemical Looping and Catalysis - Fundamental and Emerging Topics in Combustion Technology

  • 70.
    Kyprianidis, Konstantinos
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Skvaril, JanMälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Developments in Near-Infrared Spectroscopy2017Collection/Antologi (Fagfellevurdert)
    Abstract [en]

    Over the past few decades, exciting developments have taken place in the field of near-infrared spectroscopy (NIRS). This has been enabled by the advent of robust Fourier transform interferometers and diode array solutions, coupled with complex chemometric methods that can easily be executed using modern microprocessors. The present edited volume intends to cover recent developments in NIRS and provide a broad perspective of some of the challenges that characterize the field. The volume comprises six chapters overall and covers several sectors. The target audience for this book includes engineers, practitioners, and researchers involved in NIRS system design and utilization in different applications. We believe that they will greatly benefit from the timely and accurate information provided in this work.

  • 71.
    Larsson, Ida
    et al.
    SP Fire Research.
    Lönnermark, Anders
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. SP Fire Research.
    Persson, Henry
    SP Fire Research.
    Blomqvist, Per
    SP Fire Research.
    Temperature Measurements and Examination of Self-heating in Large Scale storage of Wood Pellets2014Inngår i: World Bioenergy 2014, Jönköping, Sweden, 2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper summarizes the experimental data from a large-scale storage test performed within the European project called SafePellets. Temperature measurements were made inside a silo with a capacity of storing 3000 ton of wood pellets, from August to October in 2013. The purpose of the test was to examine the self-heating of the wood pellets, where and when it occurs, how it spreads and if it could be connected to certain events. For temperature measurements, both the temperature cables belonging to the silo temperature surveillance system and thermocouples mounted by SP at the cables and on the in/out-side walls of the silo were used.

     

    The results clearly reveal that self-heating occurs almost instantly after start of filling the silo and temperatures above 40 °C inside the pellets bulk is regular. The temperature surveillance system, which was set to give an alarm signal for high temperatures, was activated several times during the test period and temperatures exceeding 60 °C were registered at several occasions. Measurements above the pellet surface also show that this headspace temperature varies much with the outside ambient temperature and the sunlight radiation. A sunny summer’s day, the headspace temperature could easily reach above 40 °C, which will influence the pellet bulk. The project also emphasized an important problem when it comes to silo storage. The problem of temperature sensor cables inside the silo not always hanging where they are supposed to be was observed in the test and dealt with.

  • 72.
    Lee, M.
    et al.
    National Taiwan University, Taipei, Taiwan.
    Keller, A. A.
    University of California, Santa Barbara, CA, United States.
    Chiang, P. -C
    National Taiwan University, Taipei, Taiwan.
    Den, W.
    Tunghai University, Taichung, Taiwan.
    Wang, H.
    Tongji University, Shanghai, China.
    Hou, C. -H
    National Taiwan University, Taipei, Taiwan.
    Wu, J.
    Tongji University, Shanghai, China.
    Wang, X.
    Tongji University, Shanghai, China.
    Yan, Jinyue
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. Tongji University, Shanghai, China; Royal Institute of Technology (KTH), Sweden.
    Water-energy nexus for urban water systems: A comparative review on energy intensity and environmental impacts in relation to global water risks2017Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 205, s. 589-601Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The importance of the interdependence between water and energy, also known as the water-energy nexus, is well recognized. The water-energy nexus is typically characterized in resource use efficiency terms such as energy intensity. This study aims to explore the quantitative results of the nexus in terms of energy intensity and environmental impacts (mainly greenhouse gas emissions) on existing water systems within urban water cycles. We also characterized the influence of water risks on the water-energy nexus, including baseline water stress (a water quantity indicator) and return flow ratio (a water quality indicator). For the 20 regions and 4 countries surveyed (including regions with low to extremely high water risks that are geographically located in Africa, Australia, Asia, Europe, and North America), their energy intensities were positively related to the water risks. Regions with higher water risks were observed to have relatively higher energy and GHG intensities associated with their water supply systems. This mainly reflected the major influence of source water accessibility on the nexus, particularly for regions requiring energy-intensive imported or groundwater supplies, or desalination. Regions that use tertiary treatment (for water reclamation or environmental protection) for their wastewater treatment systems also had relatively higher energy and GHG emission intensities, but the intensities seemed to be independent from the water risks. On-site energy recovery (e.g., biogas or waste heat) in the wastewater treatment systems offered a great opportunity for reducing overall energy demand and its associated environmental impacts. Future policy making for the water and energy sectors should carefully consider the water-energy nexus at the regional or local level to achieve maximum environmental and economic benefits. The results from this study can provide a better understanding of the water-energy nexus and informative recommendations for future policy directions for the effective management of water and energy.

  • 73.
    Leo, Johannes
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Hansen, Peter
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Aspiring for Added Value with Energy Efficient Building Renovation: REN2017 – a method for component-based selection and evaluation of building refurbishment options2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this study is to develop and propose a heuristic prescriptive method, REN2017, for identifying and evaluating component-based refurbishment options from an energy-economic and added value standpoint; and to evaluate the method in terms of its usefulness in a real life scenario. 

    This study uses an abductive single-case study approach with threads of action research encompassing primary data, from the study object and two reference objects, of on-site inspections, unstructured interviews with professionals and staff surveys. The proposed method, REN2017, is based on scientific articles and official government and organization documents within the subjects of building retrofit; energy saving; energy-efficiency-measure packages; refurbishment; added values; as well as case-specific data from qualitative document analysis. REN2017 is evaluated based on its applicability, adaptability and potency in assessing a building and identify and evaluate refurbishment options. 

    The study showed that the method was applicable to a 1969 modular preschool. Although the method was deemed potent and adaptable regarding the assessment of the study and reference objects as well as in the determination of its present state, it was regarded as lacking in its potency in the identification of refurbishment measures. The method enabled the evaluation of measures once identified. However, it requires further refinement of the evaluation phase regarding the connection between the energy-economic and the value-adding assessments as well as regarding the New Building analysis.

  • 74.
    Leva, Alberto
    et al.
    Politecn Milan, DEIB, I-20133 Milan, Italy..
    Papadopoulos, Alessandro
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Seva, Silvano
    Politecn Milan, DEIB, I-20133 Milan, Italy..
    Cimino, Chiara
    Politecn Milan, DEIB, I-20133 Milan, Italy..
    Explicit Model-Based Real PID Tuning for Efficient Load Disturbance Rejection2019Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 58, nr 51, s. 23211-23224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the process control, many PID loops are primarily devoted to rejecting load disturbances, and some of them are crucial for the quality of the overall plant operation. In such a scenario, automatic tuning is highly desired. However, load disturbance rejection calls for strong feedback up to quite high frequencies with respect to the dominant plant dynamics, on which most tuning rules are centered. As such it is difficult for a rule to yield good and, above all, uniform results in the face of all the various process structures it can be confronted with. In this paper, we propose an explicit model-based PID tuning rule specifically targeted at the problem just evidenced. The rule minimizes the magnitude of the nominal disturbance-to-output frequency response, at the same time preventing that magnitude to exhibit a peak or a plateau around its maximum. This characteristic, together with tuning the PID derivative filter, leads to sharp disturbance rejection without incurring in an excessive control sensitivity to high-frequency measurement noise and mitigates the problems caused by heterogeneous process dynamics. The proposed approach is assessed by comparing the rule with selected counterparts, on a literature benchmark with different process structures. A laboratory experiment is finally presented to show that our rule can withstand real-world operating conditions.

  • 75.
    Levay, Anders
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Roos, Olof
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Energieffektivisering av flerbostadshus: Energibesparande åtgärder för Brf Lillåudden 32018Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    The European Union’s goal for year 2020 aims to reduce the greenhouse gases by 20 % compared to the levels of 1990. This goal can be reached by increasing energy efficiency and renewable energy sources by 20 %. In Sweden housing stands for 40 % of the total energy usage and in apartment buildings district heating is the most used way for heating and hot water. In this degree project two apartment buildings, connected by a garage, have been studied to see which solutions would yield a saving in both money and the environment. The building is heated using district heating and is ventilated through mechanical exhaust ventilation. Analyzing the current energy consumption and ventilation rates, two heat pump manufacturers was contacted to see what their systems could save in terms of energy. By recovering heat from the exhaust air with a heat pump the buildings can save both money and have a reduced impact on the environment. Having a demand-controlled ventilation in the garage would not give a large enough saving in energy to be worth the investment. The already scheduled fans have decreased their energy usage by half. However by having a demand-controlled ventilation in the garage it could reduce the harmful heavy metals that get released when cars drive in and out. By simply lowering the temperature in the garage from 15 °C to 10 °C could save about 12 500 sek/year in heating costs. The conclusion to this study is that using a heat pump to recover energy from exhaust air is an investment that will generate financial savings for the cooperative apartment and have a reduced negative impact on the environment.

  • 76.
    Li, Hailong
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Song, Jingjing
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Sun, Q.
    Institute of Thermal Science and Technology, Shandong University, Jinan, China.
    Wallin, Fredrik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Zhang, Q.
    China Petroleum University, Beijing, China.
    A dynamic price model based on levelized cost for district heating2019Inngår i: Energy, Ecology and Environment, ISSN 2363-7692, Vol. 4, nr 1, s. 15-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    District Heating (DH) is facing a tough competition in the market. In order to improve its competence, an effective way is to reform price models for DH. This work proposed a new dynamic price model based on the levelized cost of heat (LCOH) and the predicted hourly heat demand. A DH system in Sweden was used as a case study. Three methods were adopted to allocate the fuel cost to the variable costs of heat production, including (1) in proportion to the amount of heat and electricity generation; (2) in proportion to the exergy of generated heat and electricity; and (3) deducting the market price of electricity from the total cost. Results indicated that the LCOH-based pricie model can clearly reflect the production cost of heat. Through the comparison with other market-implemented price models, it was found that even though the market-implemented price models can, to certain extent, reflect the variations in heat demand, they cannot reflect the changes in production cost when different methods of heat production are involved. In addition, price model reforming can lead to a significant change in the expense of consumers and consequently, affect the selection of heating solution.

  • 77.
    Li, Hailong
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Sun, Qie
    Shandong University, China.
    Zhang, Qi
    China University of Petroleum, China.
    Wallin, Fredrik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    A review of the pricing mechanisms for district heating systems2015Inngår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 42, s. 56-65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Heating represents the largest proportion of energy use as supplied to consumers across all end energy uses. Therefore, there is huge potential for energy savings in the heating sector in order to reduce the emission of CO2. District heating (DH) has been considered an efficient, environmentally friendly and cost-effective method for heating in buildings, and is playing an important role in the mitigation of climate change. In the interest of fairness and in the highly competitive market the DH companies operate, there is a strong need to develop a novel heat pricing mechanism in order to promote sustainable development of DH systems. In this paper, existing methods and models regarding heat pricing have been reviewed. The features of different pricing mechanisms have been analysed, including advantages and disadvantages. Insights into developing an advanced pricing mechanism for DH systems have been offered.

  • 78.
    Li, Yangyang
    et al.
    Tsinghua Univ, Sch Environm, Beijing 100084, Peoples R China.
    Jin, Yiying
    Tsinghua Univ, Sch Environm, Beijing 100084, Peoples R China.
    Li, Jinhui
    Tsinghua Univ, Sch Environm, Beijing 100084, Peoples R China.
    Li, Hailong
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling. Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Yu, Zhixin
    Universitetet i Stavanger.
    Effects of pungency degree on mesophilic anaerobic digestion of kitchen waste2016Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 181, s. 171-178Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated the influence of pungency degrees (PDs) on mesophilic anaerobic digestion of kitchen waste (KW). Batch tests were performed to evaluate the methane potential and production rate and the effect of PDs on organics degradation efficiency (in terms of volatile solids, protein and ether extract) at mesophilic temperature. Koch and Drewes model and modified Gompertz model were applied to assess the effects of PDs on the hydrolysis rate constant, biomethane yield rate and lag time. The results revealed that with the increasing contributions of PDs, the methane yield, organics degradation efficiency and hydrolysis rate of KW decreased while the pH values and concentrations of total ammonia nitrogen and free ammonia nitrogen were increased. Additionally, PDs lower than PD3 presented better digestion performance, and according to results of organics degradation and kinetics study, it could be suggested that appropriate range of PD in KW beneficial for AD is PD5-PD4.

  • 79.
    Lindberg, Carl-Fredrik
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. ABB Corporate Research, Sweden.
    Bhutani, Naveen
    ABB Corporate Research, Bangalore, India.
    Starr, Kevin
    ABB Inc., Westerville, OH, USA.
    Horton, Robert
    ABB Inc., Westerville, OH, USA.
    Energy Conservation in Industry: Steam Energy Fingerprint of Paper Machine2015Inngår i: Handbook of Clean Energy Systems / [ed] Jinyue Yan, Chichester, West Sussex, UK: John Wiley & Sons, 2015, s. 2175-2181Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    There is a large value in making the industry more energy efficient. The benefit is not only energy savings and reduction of CO2 emissions, the industry also becomes more competitive due to lower costs for energy, and often also improved production rate and product quality due to positive side effects when processes are made more efficient. Several factors influence efficiency, the most important ones are presented, as well as advices for an assessment and actions for improvements.

    As an example a steam energy fingerprint of a paper machine is given. In the assessment energy flows are quantified, energy users in the paper machine are benchmarked and actions for improving efficiency are suggested.

  • 80.
    Lindgren, Nicolas
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Brogren, Karl
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Production optimization for district heating: Short-term planning of district heating grid in Gävle, Sweden2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Energy systems with a high portion of renewable energy from wind and solar power can suffer from fluctuations in production due to weak winds or cloudy weather, which may affect the electricity price. When producing heat and power in a combined heat and power plant, an additional heat storage tank can be used to store the heat surplus which is obtained when the power production is high, and the heat demand is low. To optimize heat and power production economically, short-term planning can be applied. Short-term planning covers the production in the near future of 1-3 days. The optimization in this degree project is based on the district heating production, which means that the heating demand always needs to be fulfilled. The district heating production is based on the weather. Therefore a suitable period for simulation is three days due to the accuracy of the weather forecasts are reasonable. The optimization is performed on the district heat system in Gävle, Sweden. The system comprises several different production units, such as combined heat and power plants, backup plants, and industrial waste heat recovery. Two different models are made, one using linear programming and one using mixed integer non-linear programming. The model stated as a linear programming problem is not as accurate as of the one stated as a mixed integer non-linear programming problem which uses binary variables. Historical input data from Bomhus Energi AB, a company owned together by the local heat and power supplier Gävle Energi AB and the pulp and paper manufacturer BillerudKorsnäs AB, was given to simulate different scenarios. The different scenarios have various average temperatures and in some scenarios are there some issues with the pulp and paper industry affecting the waste heat recovery. In all scenarios is the heat storage tank charged when the demand is low and then discharged when the demand increases to avoid starting some of the more expensive backup plants if possible. The simulation time varies a lot between the two approaches, from a couple of seconds to several hours. Particularly when observing scenarios with a rather high demand since the backup generators use binary variables which take a lot of time to solve.       

  • 81.
    Lindmark, Johan
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Bel Fdhila, Rebei
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Thorin, Eva
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    ON MODELLING THE MIXING IN A DIGESTER FOR BIOGAS PRODUCTION2009Inngår i: / [ed] I. Troch, F. Breitenecker, 2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    At the Vaxtkraft biogas plant the mixing is produced by pumping in biogas and releasing it at the bottom. The mixing inside the digester of a biogas plant is important for good biogas production and since it is complicated to study the mixing inside the digester while it is in operation, this study is based on numerical simulations using a computational fluid dynamic finite volume code. To study the mixing dynamics, five different flow rates of gas (air) injections ranging from 0.1 to 0.6kg/s were simulated. These gas flow rates produced an average liquid speed in the digester between 0.10 and 0.22 m/s. The liquid recirculation impact on the mixing was investigated through the simulation of a case where it is combined with the lowest gas injection flow rate. The results from the simulation suggest that the liquid outlet is situated too close to the gas injection, resulting in energy losses in form of diminished mixing of the digester. A complete redesign of the digester is needed to seriously overcome the mixing limitation.

  • 82.
    Lindmark, Johan
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Thorin, Eva
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Bel Fdhila, Rebei
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    PROBLEMS AND POSSIBILITIES WITH THE IMPLEMENTATION OF SIMULATION AND MODELING AT A BIOGAS PLANT2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Advanced models are being developed for the anaerobicdigestion (AD) process. These models can be used to control and optimize industrial size biogas plant to reach their full potential. There are many models available for different types of implementations. However, many of the published models demands extensive chemical analysis that might not be practically and economically viable in industry. Sampling routines at six Swedish biogas plants was compiled for comparison with the demand of input in published modeling approaches. The gap between the models and practices in industry has to come together through model simplification and extended sampling routines. Chemical oxygen demand (COD) for example is not a commonly used analysis in Swedish biogas plants but which is regularly used to model the AD. Knowledge of the biochemical processes in AD built in to a model can help operators increase the biogas yield of the plant without jeopardizing the production. There is a lack of robust online measurement equipment today to be able to have reliable online models for operational support but near infrared spectroscopy (NIR) is a promising technology for online measuring of a series of different characteristics that could make modeling more interesting for the AD industry. The mixing has as of yet not been devoted much attention to when modeling the process.

  • 83.
    Louise, Wästhage
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Optimization of floating PV systems: Case study for a shrimp farm in Thailand2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The use of solar photovoltaic (PV) systems have expanded rapidly the last decade and today’s market includes several different solar utilizations, where floating PV is one of them. Previous studies have shown how floating PV systems increase the PV efficiency and at the same time reduce the water evaporation. The purpose of this study is to evaluate and optimize energy solutions using floating PV systems for a shrimp farm cultivation in Thailand, where the technical, environmental and economic aspects will be included. The optimizations have been done in the open source model OptiCE, where genetic algorithm (AG) have been used to maximize the renewable reliability and minimize the Levelized Costs of Electricity (LCOE). In order to find the optimal renewable solution for the investigated shrimp farm, four scenarios have been compared considering different PV system combinations. The simulated results showed how the scenarios considering floating PV system generated a higher reliability than the scenarios considering ground-mounted PV system. The scenario considered tracking PV system increased the system´s renewable reliability compared to fixed PV system. However the shrimp farm is connected to the national electric grid or not will have a huge impact on the LCOE due to the low electric price and the implemented feed-in-tariff (FIT) program. The size of the installed PV capacity significantly affects the reliability results were the capacity of 200 kWp reaches a reliability of almost 100%. The optimal solution for the investigated shrimp farm to become independent is therefore to install a combined floating PV and battery storage system.

  • 84.
    Lundberg, Lucas
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Improving a planning and communication tool for solar power plant installations in Sweden: Improvement of tools and structures and investigating the cooperation between installers and multiplicators in the Swedish PV-market2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This work is part of the master in Energy system at Mälardalens University and was written during spring of 2018. The purpose of this degree project is to evaluate the needs when it comes to planning tools for Swedish installers of PV-system. The outcome from this survey will then be used to adapt an already existing planning tool to better fit the Swedish PV-market. The method used was first a survey trip to meet with 35 different installers to get their experience and thoughts about the Swedish PV-market, their planning process, and the planning tool QuickPlan.

    The comments from the interviews were then used to adapt QuickPlan to the Swedish market. The features that were required to be fixed or updated in QuickPlan were updating the tax system, including another roof, calculating the payback period, calculating the saved CO2 emission for installing a PV-system, implementing heat pumps in the load profiles, implementing fuses and evaluating the radiation calculation within the tool. Those implementations were evaluated together with results describing what was affecting the suggested implementations.

    It was also evaluated how this business model that includes the tool QuickPlan should be implemented to the Swedish PV-market or if it not ready for it yet. The results from the survey showed the importance of certain features in a planning tool for the Swedish installers. For the implementations, a solution was presented by comparing to others results. The conclusions show that the increased adaptation of the tool to the Swedish PV-market will make it more available for the installers and the business model was overall positive according to the interviewed persons.

  • 85.
    Lundin, Rasmus
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Beitler-Dorch, Benjamin
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Modelling and Analysis of Mobile Energy Transmission for Offshore Wind Power: An analysis of flow batteries as an energy transmission system for offshore wind power2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    A comparison between a traditional fixed high voltage direct current energy transmission system and a mobile transmission system utilizing vanadium redox flow batteries has been conducted in this degree work.  The purpose of this comparison was to evaluate if a mobile energy transmission system could be competitive in terms of energy efficiency and cost-effectiveness for use in offshore wind power applications. A literary study was made to fully grasp the various technologies and to create empirical ground of which cost estimation methods and energy calculations could be derived. A specific scenario was designed to compare the two transmission systems with the same conditions. To perform the comparison, a model was designed and simulated in MATLAB. The results from the model showed that the flow battery system fell behind in energy efficiency with a total energy loss of 33.3 % compared to the 11.7 % of the traditional system, future efficiency estimations landed it at a more competitive 17.5 %. The techno-economic results proved that a mobile flow battery system would be up to nine times more expensive in comparison to a traditional transmission system, with the best-case scenario resulting in it being roughly two times more expensive. The main cause of this was found out to be the expensive energy subsystem, specifically the electrolyte, used in the flow battery system. Several environmental risks arise when using a flow battery system with this electrolyte as well which could harm marine life severely. In conclusion; with further development and cost reductions, a case could be made for the advantages of a truly mobile energy transmission system. Specifically, in terms of the pure flexibility and mobility of the system, allowing it to circumvent certain complications. The mobility of the system gives the possibility of selling energy where the spot prices are at their highest, providing a higher revenue potential compared to a traditional fixed system. As for now though, it is simply too expensive to be a viable solution.

  • 86.
    Lundkvist, Wictor
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Simulering och analys av solcellsanläggningen på brf. Sjökortet: Analys av optimala systemlösningar samt lönsamhetsberäkning av solcellsanläggningen på ett nyproducerat flerbostadshus i Västerås uppfört av Riksbyggen2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    With the growing popularity of solar cells in Sweden, real estate companies have become interested in the possibility of installing solar panels when constructing new apartment buildings. Riksbyggen is one of these companies that sees solar energy as an interesting alternative when constructing energy-efficient buildings with low energy consumption.

    The purpose of this study is to investigate optimal system solutions and the profitability of a PV-system in a newly produced apartment building containing 28 apartments in Västerås. This investigation is made possible by creating and simulating the PV-system in the simulation program PVSyst.

    The PV-system that will be installed on Brf. Sjökortet has an installed capacity of 54 kW. 40 kW will be placed on the roof with a tilt of 4° while 14 kW will be placed on the facade with a tilt of 90°.

    According the simulation results, the PV-system will produce 43,6 MWh per year, which means the specific electricity production becomes 807 kWh/kWp. Own use of solar electricity is estimated to be 61 %, which means that 26,7 MWh will be utilized directly by the housing association, while 16,9 MWh must be submitted for sale. Out of the solar electricity that can be used directly 9,9 MWh will cover the property electricity meanwhile the remaining 16,8 MWh covers the residents household electricity. The residents of the housing cooperative will thus gain access to a large portion of the produced solar electricity without having to pay for it.

    The PV-system will without investment aid become unprofitable with an annuity of – 16 304 SEK per year. When the investment aid covering 35 % of the investment cost is included, the PV-system becomes profitable with an annuity of 2 687 SEK per year.

    The own use of solar electricity is difficult to improve by only changing the tilt of the solar panels. However, the results shows that a greater amount of solar electricity can be utilized by the housing cooperative in the winter months by increasing the amount of solar panels on the facade while decreasing the amount of solar panels on the roof with the same amount. A higher amount of solar panels on the facade will though decrease the yearly solar electricity production, making it more difficult for the PV-system to show profitability.

    The determined distribution of solar modules on the roof and facade is optimally distributed if the goal for the housing association is to utilize as much solar electricity as possible directly.

  • 87.
    Lundström, Lukas
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Heat demand profiles of buildings' energy conservation measures and their impact on renewable and resource efficient district heating systems2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Increased energy performance of the building stock of European Union is seen as an important measure towards mitigating climate change, increasing resource utilisation efficiency and energy supply security. Whether to improve the supply-side, the demand-side or both is an open issue. This conflict is even more apparent in countries such as Sweden with a high penetration of district heating (DH). Many Swedish DH systems have high share of secondary energy resources such as forest industry residuals, waste material incineration and waste heat; and resource efficient cogeneration of electricity in combined heat and power (CHP) plants. When implementing an energy conservation measure (ECM) in a DH connected building stock, it will affect the operation of the whole DH system. If there are CHP plants and the cogeneration of electricity decreases due to an ECM, and this electricity is valued higher than the fuel savings, the consequences of the ECM would be negative. 

    These complex relationships are investigated by conducting a case study on the Eskilstuna DH system, a renewable energy supply system with relatively high share of cogenerated electricity. Heat demand profiles of ECMs are determined by building energy simulation, using recently deep energy retrofitted multifamily buildings of the “Million Programme”-era in Eskilstuna as model basis. How implementing ECMs impact on the DH system’s heat and electricity production under different electricity revenue scenarios has been computed and evaluated in terms of resource efficiency and CO2 emissions. 

    The results show that different ECMs in the buildings impact differently on the DH system. Measures such as improved insulation level of the building’s envelope, that decrease the heat demand’s dependence to outdoor temperature, increase the amount of cogenerated electricity. While measures such as thermal solar panels, which save heat during summer, affects the absolute amount of cogenerated electricity negatively. Revenues from cogenerated electricity influence the amount of cost-effectively produced electricity much more than the impact from ECMs. Environmental benefits of the ECMs, measured in CO2 emissions and primary energy consumption, are quite small in DH systems that have high share of forest residual fuels and electricity cogeneration. The consequences can even be negative if ECMs lead to increased need of imported electricity that is produced resource inefficiently or/and by fossil fuels. However, all studied ECMs increase the relative amount of cogenerated electricity, the ratio between amount of cogenerated electricity and the heat load. This implied that all ECMs increase the overall efficiency of the Eskilstuna DH system.

  • 88.
    Lundström, Lukas
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Song, Jingjing
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    SEASONAL DEPENDENT ASSESSMENT OF ENERGY CONSERVATION WITHIN DISTRICT HEATING AREAS2014Inngår i: Proceedings from the 14th International Symposium on District Heating and Cooling, September 7th to September 9th, 2014, Stockholm, Sweden / [ed] Anna Land, Stockholm: Swedish District Heating Association , 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    When housing companies plan for energy conserving renovations, costs and amount of saved energy are usually estimated with yearly mean values. Yet the fuel mix varies widely depending on heat demand of district heating system, often with higher cost and CO2 emission rates during winter than summer.

    Instead of comparing different energy conserving measures’ potentials with yearly mean values, it would be beneficial to examine them in a higher resolution, e.g. on daily or monthly basis, to identify real effectiveness of different measures in reducing CO2-emissions and primary energy consumption.

    In this study, three energy conserving measures are put into a building simulation model to obtain results of hourly energy consumption reduction, which is then fitted into a district heating optimization model to analyze the impact on district heating system.

    This study also discuss the correlation between energy cost for the customer and different measures’ environmental impact under new circumstances: seasonal energy price models of district heating, a price model which introduce price fluctuation throughout a year. This new factor provides a more comprehensive incitement to the property owners to encourage them to make environmental friendly decisions when planning for energy conserving renovations.

  • 89.
    Maher, Azaza
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    An analyze of long-term hourly district heat demand forecasting of a commercial building using neural networks2016Inngår i: The 8th International Conference on Applied Energy – ICAE2016, 2016Konferansepaper (Fagfellevurdert)
  • 90.
    Maher, Azaza
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Finite State Machine household’s appliances models for non-intrusive energy estimation2016Inngår i: The 8th International Conference on Applied Energy – ICAE2016 / [ed] Energy Procedia, 2016Konferansepaper (Fagfellevurdert)
  • 91.
    Maher, Azaza
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Wallin, Fredrik
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Supervised Household’s Loads Pattern Recognition2016Inngår i: 2016 IEEE Electrical Power and Energy Conference, EPEC 2016 / [ed] IEEE, 2016, artikkel-id 7771718Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The deployment of smart meters is a promising innovation that comes to enhance the energy efficiency measures in the smart grid. The smart meter enables distributors to better understand the electrical network and reduce complexity of the management operations. It offers to households monitoring and control possibilities to their everyday energy consumption through the distribution of detailed information on household consumption and its evolution. This involves disaggregation of individual household loads in term of their individual energy consumption known as Non intrusive loads monitoring. In this paper, we present a supervised NILM approach based on dynamic fuzzy c-means events clustering and KNN label matching. First, a filtering method is involved to enhance the edge/events detection step. Then we perform a dynamic Fuzzy c-means clustering procedures to build appliances signature data based on active and reactive power measurements taking into account the time of day usage. The data base is further refined to map potential clusters centers that best identify the different appliances. A performance evaluation of the proposed approach is conducted showing a recognition rate over 90% for high consumption loads and promising results for low consumption loads.

  • 92.
    Marcin, Richard
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Mucha, Matej
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    THEORETICAL STUDY TO IMPROVE THE ENERGY BALANCE IN WASTEWATER TREATMENT PLANT: Investigation of microalgae photobioreactor in biological treatment step and open algal pond in reject water treatment in Uppsala and Västerås2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The self-treatment system of nature cannot handle man-caused high rate water pollution on its own, therefore cleaning in wastewater treatment plant (WWTP) is necessary to avoid eutrophication – excessive enrichment of nature by nutrients. Current technologies applied in WWTPs are old, outdating and highly energy demanding, especially biological treatment step generally requires large amount of energy for aeration of water. The alternative to current system could be microalgae treatment step, which would use green algae to consume pollutants present in the waste water, namely nitrogen, phosphorus and heavy metals. Via photosynthesis it could produce oxygen required for biological oxidation of organic matter. Furthermore carbon source is necessary for microalgal growth, this can be added to the water as CO2 produced in other industries and so decrease global greenhouse gas footprint. Co-digestion of microalgae with undigested wastewater sludge under mesophilic conditions can give a synergic effect for biogas production, therefore harvested and co-digested microalgae could contribute to positive energy balance of WWTP. Full-scale microalgae cultivation in WWTP can be achieved only when good grow is guaranteed. This is a result of many factors, particularly access to nutrients, light condition, water temperature, and pH. The goal of master’s thesis was to understand and evaluate main factors influencing algal growth using literature review, propose design of microalgae treatment step with artificial lights and evaluate energy balance, of wastewater treatment plants in Uppsala and Västerås with new design. The work proposed two different designs of microalgae treatment steps, modelled in Excel and applied to current state of municipal WWTP in Västerås and Uppsala with belonging satellite plants. The first design of microalgae activated photobioreactor (MAASPBR) aimed to replace current biological treatment step. This is possible in Västerås and Uppsala WWTPs if microalgae can consume 75% of total nitrogen (Ntot) and produce at least 13.5 and 2.4 tonne O2/day in Västerås and Uppsala respectively. The sensitivity analysis showed that minimal volumetric algal yield of 0.15 kg/m3 ,day and 0.25 kg/m3 ,day is required for Västerås and Uppsala respectively, when oxygen production rate of 1.92 kg O2/kg microalgae is assumed. Furthermore harvested and co-digested algae with sewage sludge contributes to significant increase of biogas production and negligible transportation energy increase. The second design of open algal pond for reject water (OAPRW) aims to cultivate microalgae on reject water with high concentration of nutrients, generated in sludge centrifuge. The model assumed high algal growth due to excessive amount of nutrients and increased water temperature to 24°C. Results show a possible 23% and 20% electricity saving on blowers in the biological treatment in Västerås and Uppsala respectively. Both models have positive impact on energy balance in all WWTPs, however MAASPBR has greater uncertainties, because this type of photobioreactor has not been tested unlike OAPRW which has been tested in pilot plant scale.

  • 93.
    Mirmoshtaghi, Guilnaz
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Biomass gasification in fluidized bed gasifiers: Modeling and simulation2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Using woody biomass as a resource for production of biofuel, heat and power through gasification has been studied for years. In order to reduce the cost of operating and to design the full-scale gasification plant developing a general model to be applicable for different ranges of input data with acceptable level of accuracy, is needed. In order to develop such model for the gasifier, as the main component in the process, three major models have been studied in this thesis; theoretical model (Equilibrium model), semi-empirical model (modified equilibrium model, kinetic combined with hydrodynamic model) and empirical model (statistical model).

    Equilibrium model (EM), shows low accuracy in predicting the content ofmajor components in product gas especially CH4 and CO. Therefore to improve the accuracy of prediction modification of EM is needed. Analyzing the semi-empirical approaches show that although the accuracy of EM can be improved, the generality of the modified models are still low. Therefore two new modified models have been developed. The first model is based on including data from wider range of operating condition to develop the empirical equation. The second model is based on combining QET and reaction kinetics for char gasification approaches. The first model decreases the overall error from 44% to 31% while the overall error of second model is decreased from 36% to 8%. Other semi-empirical model for fluidized bed gasifiers which is not equilibrium-based is developed by combining reaction kinetics with hydrodynamic equations. Investigating different hydrodynamic models show that combining two-phase-structure model with reaction kinetics for bubbling fluidized bed gasifiers improves the accuracy of the kinetic-only model.

    The third type of approaches, investigated in this thesis, towards developing a general model is the empirical model. This model has been developed based on Partial least square (PLS) approach. The PLS-R model show high level of accuracy within the specific range of empirical data used for developing the model. Further analysis on the experimental dataset by PLS-R model show that equivalence ratio (ER) is the operating parameter with the most significant impact on the performance of fluidized bed gasifiers. Optimizing the operation of fluidized bed gasifiers based on this model shows that high gas quality (high volume fraction of H2, CO and CH4 and low volume fraction of CO2), high carbon conversion and low tar yield is achieved when ER≈0.3, Steam to Biomass ratio≈0.7, moisture content≈9% and particle size≈3mm and olivine is the bed material. 

  • 94.
    Moustakas, K.
    et al.
    National Technical University of Athens, Greece.
    Rehan, M.
    King Abdulaziz University, Jeddah, Saudi Arabia.
    Loizidou, M.
    National Technical University of Athens, Greece.
    Nizami, A. S.
    Government College University, Lahore, Pakistan.
    Naqvi, Muhammad
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Energy and resource recovery through integrated sustainable waste management2020Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 261, artikkel-id 114372Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This editorial is prepared for the Applied Energy Journal as a Virtual Special Issue (VSI) and it overviews the research work presented at the NAXOS 2018 6th International Conference on Sustainable Solid Waste Management, held from 13th to 16th June 2018 in Naxos Island, Greece. The research articles presented in VSI highlight the recent developments in waste valorisation for the recovery of energy, fuels and value-added products. They also cover the primary hurdles and potential solutions moving towards more sustainable society. This editorial not only presents the overall summary of the extended research papers from NAXOS 2018, but also provides an overview of the current trends and developments in the fields of waste management, waste valorization, and energy production systems. The articles published in this VSI cover a wide range of topics, including energy recovery from waste, waste to energy technologies, sustainable energy systems, anaerobic digestion, thermal arc plasma gasification, microalgal-based biorefinery, waste management, modelling of advanced gasification systems, waste valorization, and microbial fuel cell technology. 10 manuscripts, out of total 21 extended mansucripts invited, were accepted for publication in the Applied Energy Journal through peer review process conducted by the expert reviewers in the relevant fields with the aid of the guest editors.

  • 95.
    Mählkvist, Simon
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Pontus, Netzell
    Pulp mill heat and mass balance model: Exploring the benefits and possibilities of process modelling as an applied method in a case study2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis focused on the modelling of a pulping process. The purpose was to see if an accurate model can be crated based on relatively simple premises and if the errors can be identified or analysed. To realise this, the authors conducted a literature study to identify the current state of the art regarding the chemical pulping process. In addition, flow charts and sample data from a case study were examined. Based on the literature review and case study, model assumptions were derived. The model is divided into sixteen components. Where mixing occurs, lumped conditions are assumed. The model has five validation points, four of which are temperatures and a mass flowrate. These are shown as deviations from the measured values. In conclusions, it was the model could produce stable results over a narrow time frame. More so if the transition period at the start of the simulation is overlooked. Several new model assumptions are presented with the purpose to increase accuracy e.g. account for the components ability to store mass.

  • 96.
    Nabati, Hamid
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Numerical and Theoretical Investigation on CoolingPerformance of Radiators in the Power TransformersInngår i: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, heat transfer and fluid flow in a cooling system of power transformers have been studied. In order to simplify the study, a single radiator element is chosen which is composed of two welded identical steel plates. Also based on symmetrical property of radiator, just one quarter of it, was modelled and simulated. It is well known that phenomenon like Foucault currents generate unwanted loss in form of heat in the transformers. From engineering and design points of view, it is desired to establish efficient cooling in transformers efficiently in order to increase their operation life. The main objective in the current paper is to study the current situation of cooling system and its characteristics to identify the weakness points of installed cooling system. Also a new configuration for oil channels based on pin fin technology was studied to evaluate its capability for cooling efficiency improvement in this special case. Result can be used for optimization of power transformer cooling system in future studies. To accomplish these goals, a basic model based on theoretical correlation and a numerical study was performed for radiator model in the ONAN state. The physical properties of the cooling oil were calculated from technical drawing obtained from Iran Transfo Company. The finite volume method was used to solve the fluid and heat transfer governing equations in the steady state. Results show that there is a good agreement between available data, theoretical model and CFD model for oil channel in the current configuration. Heat transfer in ONAN state is within acceptable range, but the oil entrance and outlet passages should be redesigned to get better flow behaviour.  The radiator height has a direct effect on outlet temperature; however the maximum reduction in the outlet temperature would 7%, when the height is doubling. The radiator equipped with internal pin fins shows better heat transfer behaviour, while the pressure drop through the channels remains in acceptable range.

  • 97.
    Nabati, Hamid
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Evaluation of CFD Method for Efficiency Improvement in CO2Capturing with Application of Pin Fin TechnologyInngår i: Chemical Product and Process Modeling, ISSN 1934-2659Artikkel i tidsskrift (Fagfellevurdert)
  • 98.
    Nabati, Hamid
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Time, R.W.
    PREDICTION OF CONDENSING FLOW WITH RELEVANCE TO FLUE GAS CONDENSER AND CO2 CAPTURING2009Inngår i: Proceedings of SIMS 50, 2009Konferansepaper (Annet vitenskapelig)
  • 99.
    Naqvi, Muhammad Raza
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Yan, Jinyue
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Complementing existing CHP plants using biomass for production of hydrogen and burning the residual gas in a CHP boiler2017Inngår i: Biofuels, ISSN 1759-7269, E-ISSN 1759-7277, nr 6, s. 675-683Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biorefinery systems at combined heat and power (CHP) plants represent numerous technical, economic and environmental benefits by utilizing the existing biomass handling infrastructure and producing biofuels together with heat and power. This study evaluates the economic feasibility of integrating biomass gasification to an existing CHP plant. Integration includes biomass gasification with downstream processing of the synthesis gas to remove particles and tars, condense out water, remove CO2 and use membrane filtration (polyamide membrane) to extract hydrogen. The separated residual gas components are utilized as extra fuel to the boiler in the CHP plant. Approximately 58.5 MWth of synthesis gas can be produced from a 90 MWth plant that represents 16.4 MWthof hydrogen. The rest of the heating value of produced synthesis gas (in the form of methane and carbon monoxide) is utilized for heat and power production. From an economic perspective, the production cost of hydrogen is estimated to be 0.125–0.75 €/kg. This can be compared to the US governments goal that H2 produced by wind power plus electrolyzers should have a maximum cost of 2.8–3.4 €/kg. The lower cost is for a unit operating at 3 bar and assuming that the costs are split between H2 and the syngas residue that is combusted, while the higher prices assume an atmospheric gasifier and all costs are put on the H2 produced.

  • 100.
    Naqvi, Muhammad Raza
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Yan, Jinyue
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Biorefinery: Production of Biofuel, Heat, and Power Utilizing Biomass2015Inngår i: Handbook of Clean Energy Systems / [ed] Prof. Jinyue Yan, United States: WILEY , 2015Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The world’s energy consumption is projected to increase rapidly that will cause depletion of known fossil fuel resources, global warming and threat to future energy security. Biomass is likely to play a significant role in the future energy systems replacing conventional fuels due to strict regulations for reducing greenhouse gas (GHG) emissions as well as contributing as additional resource in the global energy mix. Biomass is processed in a bio-refinery facility for polygeneration of bio-energy products such as biofuels, heat, and power. Polygeneration system can be categorized based on various process routes producing electricity or biofuels or even providing only heat e.g. biomass gasification system, integrated biogas production with combined heat and power by treating organic waste, tri-generation systems etc. The successful commercialization of bio-refinery systems for polygeneration require pilot plants to demonstrate improvements in energy efficiency,  substantial biofuel, heat and power production potential from biomass together with reduced cost. From the sustainability perspective, bio-refinery systems show numerous economic, social and environmental benefits including diversification in biomass resources and bio-energy products.

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