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  • 101.
    Jansson, Johan
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Model based control and optimization in pulpindustry2004In: SIMS, Copenhagen, September 2004, 2004Conference paper (Refereed)
  • 102.
    Jansson, Johan
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Groble, Fran
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Avelin, Anders
    Mälardalen University, School of Business, Society and Engineering.
    On-line simulation of continuous pulp digester2009In: TAPPSA JournalArticle in journal (Refereed)
    Abstract [en]

    Continuous cooking is the dominant process in the kraft pulping industry.  Our general knowledge and understanding of process conditions inside the digester is limited. Process control systems comprise of groups of measurements, which give information about conditions at the outer shell of the digester.  These measurements mostly tell about cooking liquor inflows and outflows, temperature and it is also possible to measure pressure or pressure difference at the screen section of the digester shell.  But ultimately process conditions inside the digester are based on measurements at the shell and intelligent approximations.

     

    The aim of this paper is to describe more accurately the cooking conditions and phenomena inside the digester.  A model of a continuous digester was developed as an extension of the well known Purdue model [Bhartiya, 2003].  The model was adapted to simulate an industrial Lo-Solids pulp digester as well as an ITC digester.  The models were then used to do online predictions and these predictions were compared with the actual plant performance.

  • 103.
    Jansson, Johan
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Grobler, Fank
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Model based control and optimization of  continuous digester2008In: TAPPSA JournalArticle in journal (Refereed)
    Abstract [en]

    Continuous pulp digesters are large reactors with significant residence time. They play a critical role in shaping the pulp qualities achieved at the product-end.  For this reason, there is a big drive towards developing fundamental dynamic models to be used for better process understanding and control (especially in the development of model based controllers).

    In this paper we discuss the use of physical models for diagnostics and process optimization of a continuous digester.  

     

    Accurate diagnostics are not possible without the use of a pressure-flow net. The pressure-flow net also makes it possible to validate pressure and flow sensors in the circulation around the digester.  For control purposes however, the pressure-flow net is not so important.

     

    Two dynamic physical models were built for a continuous digester, one with a pressure-flow net and one without.  The model without the pressure-flow net has been tuned and tested with good results at Ngodwana mill.  It was not possible to get the model which included  the pressure-flow net running with as many digester section blocks as we wanted due to the he system becoming stiff. However, for a lower number of sections results were obtained. With an adjustment of the boundary conditions, higher number of sections should be possible to test as well.

  • 104.
    Javed, F.
    et al.
    LUMS School of Science and Engineering, Lahore, Pakistan.
    Arshad, N.
    LUMS School of Science and Engineering, Lahore, Pakistan.
    Wallin, Fredrik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Vassileva, Iana
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    An adaptive optimization model for power conservation in the smart grid2010In: Conference Proceedings - IEEE International Conference on Systems, Man and Cybernetics, 2010, 2010, p. 1563-1570Conference paper (Refereed)
    Abstract [en]

    Dynamically adaptive systems (DAS) such as smart grids, cloud computing applications, sensor networks and P2P networks tend to change their structure at runtime. T herefore, design-time modeling for such systems are sometimes not enough to incorporate self-* properties. To this end, we have developed a dynamic mathematical modeling framework for runtime optimizations for DAS. In this paper, we describe how our system engineers a linear programming model by using a smart-grid application for power distribution as a case-study. At runtime whenever an optimization is desired this modeling framework captures the state of the system, converts it into an appropriate linear programming model, plan the changes using mathematical manipulations and apply the changes to the actual system. Our results show that this framework is able to capture accurate runtime models of large power systems and is able to adapt itself with the change in the size or structure of the system.

  • 105.
    Javed, F.
    et al.
    School of Science and Engineering, Lahore, Pakistan.
    Arshad, N.
    School of Science and Engineering, Lahore, Pakistan.
    Wallin, Fredrik
    Mälardalen University, Department of Public Technology.
    Vassileva, Iana
    Mälardalen University, Department of Public Technology.
    Dahlquist, Erik
    Mälardalen University, Department of Public Technology.
    Engineering optimization models at runtime for dynamically adaptive systems2010In: Proceedings of the IEEE International Conference on Engineering of Complex Computer Systems, ICECCS, 2010, p. 253-254Conference paper (Refereed)
    Abstract [en]

    Dynamically adaptive systems (DAS), such as smart grids, cloud computing applications, sensor networks and P2P networks tend to change their structure at runtime. Therefore, design-time modeling for such systems are sometimes not enough for self-management. To this end, we have developed a dynamic mathematical modeling framework for runtime modeling for DAS. In this paper, we describe how our system engineers a linear programming model for self-optimization by using a smart-grid application for power distribution as a case-study. At runtime whenever, an optimization is desired this modeling framework captures the state of the system, converts it into an appropriate linear programming model, plan the changes using mathematical manipulations and apply the changes to the actual system. Our initial simulation results show that this framework is able to capture accurate runtime models of large power systems and is able to adapt itself with the change in the size or structure of the system by constructing a succinct model which is faster and more efficient than a design time model.

  • 106.
    Javed, Fahad
    et al.
    LUMS Sch Sci & Engn, Dept Comp Sci, Lahore, Pakistan.
    Arshad, Naveed
    LUMS Sch Sci & Engn, Dept Comp Sci, Lahore, Pakistan .
    Wallin, Fredrik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Vassileva, Iana
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Forecasting for demand response in smart grids: An analysis on use of anthropologic and structural data and short term multiple loads forecasting2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 96, p. 150-160Article in journal (Refereed)
    Abstract [en]

    The electric grid is changing. With the smart grid the demand response (DR) programs will hopefully make the grid more resilient and cost efficient. However, a scheme where consumers can directly participate in demand management requires new efforts for forecasting the electric loads of individual consumers. In this paper we try to find answers to two main questions for forecasting loads for individual consumers: First, can current short term load forecasting (STLF) models work efficiently for forecasting individual households? Second, do the anthropologic and structural variables enhance the forecasting accuracy of individual consumer loads? Our analysis show that a single multi-dimensional model forecasting for all houses using anthropologic and structural data variables is more efficient than a forecast based on traditional global measures. We have provided an extensive empirical evidence to support our claims.

  • 107.
    Karim, Adel
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Bard, Gert
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Lindberg, E.
    Broman, L.
    Nordlander, S.
    Modeling of a Thermo-photovoltaic System (TPV)2007In: IGEC III Conf, 2007Conference paper (Refereed)
  • 108.
    Karlsson, C
    et al.
    Mälardalen University, Department of Public Technology.
    Dahlquist, Erik
    Mälardalen University, Department of Public Technology.
    Dotzauer, Erik
    Mälardalen University, Department of Public Technology.
    Data Reconciliation and Gross Error Detaction for Flue Gas Train in Heat and Power Plant, USAManuscript (Other academic)
  • 109.
    Karlsson, Christer
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Avelin, Anders
    Mälardalen University, School of Business, Society and Engineering.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Improving the usage of process data collected in process industry and power plants2007In: Procedings Eurosim conference, Ljubljana, 2007Conference paper (Refereed)
  • 110.
    Karlsson, Christer
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Avelin, Anders
    Mälardalen University, School of Business, Society and Engineering.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    New Methods for Adaptation to Degeneration in Process Models for Process Industries2009In: Chemical Product and Process Modeling, Vol. Vol. 4, no : Iss. 1, p. , Article 25.-Article in journal (Refereed)
    Abstract [en]

    The implementation of model-based control and diagnostics suffer strongly from the fact that models deteriorate as a function of process and sensor deterioration. Also, changes in the raw material (i.e. wood) may occur and often the process control is not addressing these variations in reality. It is thus vital for the model system to be robust in the sense that it is transparent and easy for the operator to maintain. Robustness is essential in many parts of the system, including measurement, process model validation, the ability of the model to adapt to changes in the process, optimization algorithms, and of course the model itself. In this paper, we first show three real-life applications of the utilization of models for diagnostics and control. Thereafter conditions for on-line adaptation of the models are discussed. The challenges when designing such a system are in achieving operator confidence, filtering of misleading measured data, adaptation of process parameters when the process parameters change, and combining validation of measurements and process models. These challenges are met by using a combination of physical and statistical models and methods based on them such as model predictive control (MPC) and parameter estimation. The model should be maintained by a qualified engineer who should be able to explain the system to the operator so that it is understood and confidence can be maintained.

  • 111.
    Karlsson, Christer
    et al.
    Mälardalen University, Department of Public Technology.
    Dahlquist, Erik
    Mälardalen University, Department of Public Technology.
    Process and sensor diagnostics: Data reconciliation for a flue gas channel2003Report (Other academic)
  • 112.
    Karlsson, Christer
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Kvarnström, Andreas
    Dotzauer, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Estimation of process model parameters and process measurements – a heat exchanger example2006In: Conference Proceedings New Trends in Automation, 2006Conference paper (Refereed)
  • 113.
    Kullman, M.
    et al.
    Eskilstuna Strängnäs Energy and Environment, Stockholm, Sweden.
    Campillo, Javier
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Fertner, C.
    University of Copenhagen, Department of Geosciences and Natural Resource Management, Copenhagen, Denmark.
    Giffinger, R.
    Vienna University of Technology, Department of Spatial Planning, Vienna, Austria.
    Grosse, J.
    University of Copenhagen, Department of Geosciences and Natural Resource Management, Copenhagen, Denmark.
    Groth, N. B.
    University of Copenhagen, Department of Geosciences and Natural Resource Management, Copenhagen, Denmark.
    Haindlmaier, G.
    Vienna University of Technology, Department of Spatial Planning, Vienna, Austria.
    Kunnasvirta, A.
    Turku University of Applied Sciences, Environment and Business, Turku, Finland.
    Strohmayer, F.
    Vienna University of Technology, Department of Spatial Planning, Vienna, Austria.
    Haselberger, J.
    Hamburg University of Applied Sciences, Hamburg, Germany.
    Note: The PLEEC project–planning for energy efficient cities2016In: Journal of Settlements and Spatial Planning, ISSN 2069-3419, Vol. 2016, p. 89-92Article in journal (Refereed)
    Abstract [en]

    Globally, more than 50% of all people are living in cities today. Enhancing sustainability and efficiency of urban energy systems is thus of high priority for global sustainable development. The European research project PLEEC (Planning for Energy Efficient Cities) focuses on technological, innovative, behavioural and structural capacities of European medium-sized cities in their transition towards Energy Smart Cities. The variation of strengths and weaknesses of cities’ capabilities as well as practices and tools for enhancing energy efficient performance of urban energy systems were at the centre of the project. This short note summarises its main findings.

  • 114.
    Kumm, M
    et al.
    Mälardalen University, Department of Public Technology.
    Nyman, H
    Dahlquist, E
    Lundin, K
    The impact from outside wind on air movments in a telecom tunnel2005Manuscript (preprint) (Other academic)
  • 115.
    Kyprianidis, Konstantinos
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    On the trade-off between aviation NOx and energy efficiency2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 185, p. 1506-1516Article in journal (Refereed)
    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.

  • 116.
    Kyprianidis, Konstantinos
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Cranfield University, UK.
    Nalianda, Devaiah
    Cranfield University, UK.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    A NOx Emissions Correlation for Modern RQL Combustors2015In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 75, p. 2323-2330Article in journal (Refereed)
    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.

  • 117.
    Larsson, Eva K.
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Separation of methane2013Report (Other academic)
    Abstract [en]

    Gasification with gas cleaning and direct separation of methane, where the residual gas can be used in a conventional boiler, is an attractive scenario in regard to flexible production of methane, power and heat. The technological challenge is to separate methane from a product gas with a low methane content and also complex composition.

    Membranes have several attractive properties for this application. They consume no energy input for their operation, as long as the feed is pressurized and no recirculation etc. is needed. They have attracted a great deal of interest in the last decades for separation of methane and carbon dioxide from anaerobic digestion biogas production and for treatment of natural gas. They have the potential to offer cost effect­tive solutions also for smaller plants, since they are delivered in modules that can be duplicated to fit the size of the plant. For these reasons, it was chosen to concentrate the study on membranes. Alternative separation methods that were considered are cryogenic separation and pressure swing adsorption (PSA).

    Membranes separate gases based on differences in gas components’ diffusivity and solubility in the (polymer) membrane material. It was found that both these factors differ too little between CH4 and N2 to assume a possibility to separated them, if N2 is a large part of the gas composition, as is the case in air-blown gasification. Therefore, it was concluded that membrane separation is not an option for air-blown gasification. Instead, a gas from oxygen-blown CFB gasification or from dual bed indirect gasification was set as the input gas, thereby eliminating the problem with N2 in the search for suitable membranes. The main components in the gas are then H2, CO, H2O, CO2, CH4 and some higher hydrocarbon. An ideal separation would yield only CH4 and higher hydrocarbons in one stream and the other components in another.

    There are two kinds of membranes, glassy, that separate mainly based on size, and rubbary, that separate mainly based on solubility which is closely connected to the boiling point of the gas components. Calculations were made on a typical glassy membrane. It was found that the problem is that the separation between CH4 and CO is insufficient. Therefore, a two-step membrane separation with a shift step between was tried. The shift reaction, CO + H2O -> H2 + CO2, introduces a gas composition to the second membrane that is more easily separated. Even with the possibly overoptimistic conditions set in this preliminary calculation, the result is unsatisfactory. The achieved CH4 percentage is only 80% and 30% of the methane is lost in the gas streams that will be combusted for heat and power production. Also, this separation option would require a rather complicated process. The conclusion is that it is unlikely that this concept would be attractive, even after modifications to achieve better percentage values. 

    Rubbary membranes have also been considered. Based on the separation factors, it can be conclu­ded that they would require upstream separation of H2O and CO2 by a glassy membrane or other gas processing methods, before a rubbary membrane could perform the separation between CH4 and H2+CO. It is, however, unlikely that this separation would be sufficiently good, at least in a one-step system.

    A possible way to increase performance of membranes is to use liquid membranes that has a liquid to absorb gas components that have permeated through the membrane. No publications have been found on specific liquid membranes that could be suitable for the separation in question. Liquid membranes intrinsically add the need for regeneration of the liquid phase. Further search for liquid membranes is assessed as one of the interesting routes for continued investigations on separation. 

    Cryogenic separation can be expected to fulfil the requirements on gas quality and minimizing CH4 loss. The drawback is that a cryogenic plant would mean substantial investment cost and energy consumption. A conclusion from a rough cost analysis is that the cryogenic alternative seems to have the potential to be cost effective and should be included in further studies.

    Liquid membranes, cryogenic and also PSA etc. are all worth considering for the separation process.

  • 118.
    Li, Hailong
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Han, Song
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Potentials of energy saving and efficiency improvement from lighting and space heating: a case study of SAAB2012Conference paper (Refereed)
  • 119.
    Li, Hailong
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Larsson, Eva K.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yu, Xinhai
    E China Univ Sci & Technol, Shanghai, Peoples R China.
    Feasibility study on combining anaerobic digestion and biomass gasification to increase the production of biomethane2015In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 100, p. 212-219Article in journal (Refereed)
    Abstract [en]

    There is a rapid growing interest in using biomethane as fuel for transport applications. A new concept is proposed to combine anaerobic digestion and biomass gasification to produce biomethane. H-2 is separated from the syngas generated by biomass gasification in a membrane system, and then is used to upgrade raw biogas from anaerobic digestion. Simulations have been conducted based on the real operation data of one full scale biogas plant and one full scale biomass gasification plant in order to investigate the feasibility of the new concept. Results show that although less power and heat are generated compared to the gasification plant, which results in a lower overall efficiency, much more biomethane can be produced than the biogas plant; and the new concept can achieve a higher exergy efficiency. Due to the increasing price of biomethane, the novel concept demonstrates a big potential of income increase. For example, at a biomethane price of 12.74SEK/kg, the annual income can be increased by 53% compared to the total income of the biogas and gasification plant. (C) 2015 Elsevier Ltd. All rights reserved.

  • 120.
    Li, Hailong
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindmark, Johan
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nordlander, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zhao, Li
    Tianjin University, China.
    Using the solid digestate from a wet anaerobic digestion process as an energy resource2013In: Energy technology, ISSN 2194-4296, Vol. 1, no 1, p. 94-101Article in journal (Refereed)
    Abstract [en]

    The wet anaerobic digestion process is a widely used method to produce biogas from biomass. To avoid the risks involved with using the digestion waste as a fertilizer, this work investigates the possibilities to use the solid digestate as an energy resource to produce heat and electricity, which could save some energy currently consumed by the plant and, therefore, may increase the overall efficiency of a biogas plant. Simulations were conducted based on real data from the Växtkraft biogas plant in Västerås, Sweden as a case study. Results show that it is necessary to dry the solid digestate before combustion and include flue-gas condensation to recover enough heat for the drying process. When a steam turbine cycle is integrated, the generated electricity could cover 13–18 % of the total electricity consumption of the plant, depending on the degree of dryness. In addition, reducing the digestion period can increase the carbon content (ultimate analysis), the heating value, and the mass flow of the solid digestate. As a result, the production of electricity and heat is augmented in the steam turbine cycle. However, the production of biogas is reduced. Therefore, a comprehensive economic evaluation is suggested to optimize a biogas plant that uses the solid digestate from a wet anaerobic digestion process as an energy resource.

  • 121.
    Li, Hailong
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Economic assessment of the mobilized thermal energy storage (M-TES) system for distributed heat supply2013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 104, p. 178-186Article in journal (Refereed)
    Abstract [en]

    A conceptual system, mobilized thermal energy storage system (M-TES), was proposed for distributed heat supply. The economic evaluation that is essential to identify the key issues and provide guidelines regarding system improvement was conducted in this paper. Results show that the cost using M-TES to supply heat (COH) is primarily determined by the transport distance and the heat demand. The variation of COH is proportional to the transport distance, but inversely proportional to the heat demand. According to the sensitivity study, COH is more sensitive to the price of phase change material (PCM) than other parameters, such as the transport cost. Moreover, it is possible for an M-TES system to compete with other heat supply methods, such as pellet/bio-oil/biogas/oil boiler systems and electrical air-source heat pump. When using M-TES to replace the existing system, the payback time is mainly determined by the transport distance and the heat demand. Water is another potential working fluid for M-TES system. Comparatively, using PCM is more suitable for cases with larger heat demand or longer transport distance.

  • 122.
    Li, Yuying
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Nanyang Normal University, China.
    Ren, Xuemin
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Nanyang Normal University, China.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Fan, Panpan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Nanyang Normal University, China.
    Chao, T.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Nanyang Normal University, China.
    Biogas Potential from Vetiveria zizaniodes (L.) Planted for Ecological Restoration in China2014In: Applied energy conference proceedings, ISSN 0306-2619, Vol. 61, p. 2733-2736Article in journal (Refereed)
    Abstract [en]

    Biogas is a promising renewable fuel all over the world. The experiment of biogas productivity from vetiver (Vetiveria zizanioides L.) was carried out to study the effect of different harvest times on the biogas yield and the dynamics of some fermentation parameters during 2011-2012. Micro-aerobic fermentation technology is used at the pretreatment of the vetiver plants. The batch anaerobic digestion technology and drainage collection process were used. The results showed that the harvest time of vetiver plants had greater effect on the biogas yield. There were more deferences among the biogas yield, daily biogas yield and biomass utilization of the plants growing at different stages. Plant nutrient had less changes during anaerobic fermentation. The results suggested that Vetiveria zizanioides could be used as a raw material of biogas production and both ecological protect and energy production could exist in a mutually beneficial system.

  • 123.
    Lie, Bernt
    et al.
    Telemark University College.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Optimal use of bioenergy by advanced modeling and control2013In: Technologies for Converting Biomass to Useful Energy / [ed] Erik Dahlquist, Taylor & Francis Group, 2013, 1, p. 373-400Chapter in book (Refereed)
    Abstract [en]

    Officially the use of biomass for energy use globally is only 10-13 % of the total energy demand of 140 000 TWh/y. Still, the production of biomass annually is in the range of 270 000 TWh/y. Most of it obviously is not used very efficiently, although some is also used as food. There is thus a need for new methods for converting biomass into refined products like chemicals, fuels, wood and paper products, heat, cooling and electric power. The different type of conversion methods covered is biogas production, bio-ethanol production, torrefaction, pyrolysis, high temperature gasification and combustion. These methods are covered as well as principals for controlling the processes. The suitability for the different methods for different type of biomass as well as different versions of the methods is presented – both existing methods and those being developed for the future. System optimization using modeling methods and simulation is covered as well as analysis of advantages of different solutions. Many key-experts from all over the world are presenting the keys of their specialties to give us an up-to-date view of the situation all over the world. This book has the aim to give facts and inspiration to professionals like engineers and researchers, students as well as those working for different type of authorities or societal organizations.

  • 124.
    Lindhult, Erik
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Campillo, Javier
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Read, S.
    TU Delft, Delft, Netherlands.
    Innovation capabilities and challenges for energy smart development in medium sized European cities2016In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, no 88, p. 205-211Article in journal (Refereed)
    Abstract [en]

    Transition towards becoming Energy smart city integrating different areas of energy production, distribution and use in a community requires a spectrum of capabilities. The paper reports on findings from the EU planning project PLEEC, involving six medium sized European cities. The purpose of the paper is to describe innovation capabilities and challenges in the complex, systemic innovation journey of cities in the transition to sustainability. A case of implementing an innovative project for electrical vehicles in Eskilstuna is presented illustrating both technological potentials and innovation challenges.

  • 125.
    Lindmark, Johan
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Lagerkvist, Anders
    Luleå University of Technology, Division of Waste Science and Technology.
    Nilsson, Erik
    Andreas, Lale
    Luleå University of Technology, Division of Waste Science and Technology.
    Carlsson, My
    Luleå University of Technology, Division of Waste Science and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Pre-treatment of Substrate for Increased Biogas ProductionManuscript (preprint) (Other academic)
    Abstract [en]

    The full biogas potential of most organic material cannot be exploited with today’s technology. The complex structures of the organic materials are broken down too slowly and the nutrients cannot become biologically available during the relatively short retention time of most digesters. This means that a lot of the bound energy in the organic material leaves the biogas plant with the liquid digestate. There is a possibility to increase the efficiency of the process by pre-treating the material before digestion. This paper explores a pre-treatment of ley crop silage using electrical fields, known as electroporation (EP). Different settings of the EP equipment were tested and the results were analysed using a batch digestion setup. The results from the experiments show that there is a possibility to double the biogas production at typical retention times of a CSTR. The energy balance of the EP equipment suggests that the pre-treatment yield is around 2-6 times larger than the energy input to the process, i.e. energy in the form of methane.  

  • 126.
    Lindmark, Johan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lagerkvist, Anders
    Division of Waste Science and Technology, Luleå University of Technology, Luleå, Sweden.
    Nilsson, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, My
    AnoxKaldnes AB, Lund, Sweden.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Evaluating the effects of electroporation pre-treatment on the biogas yield from ley crop silage.2014In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, Vol. 174, no 7, p. 2616-2625Article in journal (Refereed)
    Abstract [en]

    Exploiting the full biogas potential of some types of biomass is challenging. The complex structures of lignocellulosic biomass are difficult to break down and thus require longer retention times for the nutrients to become biologically available. It is possible to increase the digestibility of the substrate by pre-treating the material before digestion. This paper explores a pre-treatment of ley crop silage that uses electrical fields, known as electroporation (EP). Different settings of the EP equipment were tested, and the results were analyzed using a batch digestion setup. The results show that it is possible to increase the biogas yield with 16 % by subjecting the substrates to 65 pulses at a field strength of 96 kV/cm corresponding to a total energy input of 259 Wh/kg volatile solid (VS). However, at 100 pulses, a lower field strength of 48 kV/cm and the same total energy input, no effects of the treatment were observed. The energy balance of the EP treatment suggests that the yield, in the form of methane, can be up to double the electrical energy input of the process.

  • 127.
    Lindmark, Johan
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Nilsson, Erik
    Lagerkvist, Anders
    Luleå University of Technology, Division of Waste Science and Technology.
    Andreas, Lale
    Luleå University of Technology, Division of Waste Science and Technology.
    Carlsson, My
    Luleå University of Technology, Division of Waste Science and Technology.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering.
    Pretreatment of Substrate for Increased Biogas Production2010Conference paper (Refereed)
  • 128.
    Lindmark, Johan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Bel Fdhila, Rebei
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB, Corporate Research, Västerås.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Effects of mixing on the result of anaerobic digestion: Review2014In: Renewable & Sustainable Energy Reviews, ISSN 1364-0321, Vol. 40, p. 1030-1047Article in journal (Refereed)
    Abstract [en]

    Mixing in an anaerobic digester keeps the solids in suspension and homogenizes the incoming feed with the active microbial community of the digester content. Experimental investigations have shown that the mixing mode and mixing intensity have direct effects on the biogas yield even though there are conflicting views on mixing design. This review analyzes and presents different methods to evaluate the mixing in a digester (chemical and radioactive tracers and laboratory analysis), tools for digester design (computational fluid dynamics and kinetic modeling) and current research on the effects of mixing on the anaerobic digestion process. Empirical data on experiments comparing different mixing regimes have been reviewed from both a technical and microbial standpoint with a focus both on full scale digesters and in lab-scale evaluations. Lower mixing intensity or uneven mixing in the anaerobic digestion process can be beneficial during the startup phase to allow for methanogenic biomass growth and alleviate process instability problems. Intermittent mixing has been shown to be able to yield a similar gas production as continuous mixing but with the possibility to reduce the maintenance and energy demands of the process. Problems often experienced with experimental design include the effect of mixing on the solids retention time, and measurement of steady state gas production because of startup instabilities. Further research should be aimed at studying the effects of mixing on a chemical and microbial level and on the different stages of anaerobic digestion (hydrolysis, acidogenesis, acetogenesis and methanogenesis). The focus should be on the effects of mixing on a multiple stage digestion process and also finding new methods to evaluate the effects of mixing in the one stage digestion process rather than evaluating a wider range of mixing modes, intensities and substrates.

  • 129.
    Lindmark, Johan
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Bel Fdhila, Rebei
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    PROBLEMS AND POSSIBILITIES WITH THE IMPLEMENTATION OF SIMULATION AND MODELING AT A BIOGAS PLANT2012Conference paper (Refereed)
    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.

  • 130.
    Lu, Yuexia
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    X., Yu
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Experimental investigation on CO2 absorption using absorbent in hollow fiber membrane contactor2008In: International Scientific Conference on "Green Energy management and IT", Stockholm, March 12-13, 2008, 2008Conference paper (Refereed)
  • 131.
    Lu, Yuexia
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Xinhai, Yu
    E China Univ Sci & Technol, Shanghai.
    Shan-Tung, Tu
    E China Univ Sci & Technol, Shanghai.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Experimental Studies on Simultaneous Removal of CO2 and SO2 in a Polypropylene Hollow Fiber Membrane Contactor2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, p. 283-288Article in journal (Refereed)
    Abstract [en]

    Membrane gas absorption technology is a promising alternative to conventional technologies for the mitigation of acid gases. In this study, simultaneous removal of SO2 and CO2 from coal-fired flue gas was studied in a polypropylene hollow fiber membrane contactor using aqueous monoethanolamine as the absorbent. The influences of liquid and gas flow rates on the simultaneous absorption performance of CO2 and SO2 were investigated. The experimental results indicated that the membrane contactor could eliminate these two sour gases simultaneously and effectively. Absorption of SO2 and CO2 was enhanced by the increase in liquid flow rate and decrease in gas flow rate. It was observed that a small amount of SO2 in the flue gas had a slight influence on the absorption of CO2. In addition, the membrane contactor was continuously operated for two weeks to evaluate its duration performance. The results showed that the CO2 mass transfer rate was decreased significantly with the operating time due to partial wetting of membrane pores. After 14 days of continuous operation, the CO2 mass transfer rate of the wetted membrane contactor was decreased by 41% but could be retrieved to 86% of the fresh one by increasing the gas phase pressure.

  • 132.
    Lu, Yuexia
    et al.
    East China University of Science and Technolog.
    Xinhai, Yu
    East China University of Science and Technology.
    Shan-Tung, Tu
    East China University of Science and Technology.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Wetting of polypropylene hollow fiber membrane contactors2010In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 362, no 1-2, p. 444-452Article in journal (Refereed)
    Abstract [en]

    The membrane wetting by the absorbent leads to the increase of mass transfer resistance and deterioration of CO2 absorption performance during membrane gas absorption process. In this paper, polypropylene (PP) fibers were immersed in monoethanolamine (MEA), methyldiethanolamine (MDEA) and deionized (DI) water, respectively, assuming that the immersed PP fibers would undergo similar exposure conditions as those used in hollow fiber membrane contactor. The wetting evolution of PP fibers was investigated as a function of immersion time. The characterization results confirmed that the absorbent molecules diffused into the PP polymer during the exposure process, resulting in the swelling of the membrane. The absorption-swelling wetting mechanism was proposed to explain what happened during the wetting process. A 30.8° reduction in the contact angle was observed, indicating that the membrane surface hydrophobicity decreased significantly following the immersion time. Experimental results showed that the membrane surface morphology and surface roughness suffered significant and complicated changes after being immersed in the absorbents for a certain period. It was found that the absorbent with higher surface tension is in favor of fewer changes of the membrane surface morphologies. Based on the experimental results, improving the membrane surface hydrophobicity was suggested as an effective way to overcome the wetting problem.

  • 133.
    Lu, Yuexia
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology. East China University of Science and Technology, Shanghai, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering.
    Yu, X.H
    East China University of Science and Technology, Shanghai, China.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering.
    CO2 capture by the absorption process in the membrane contactors2009In: 6th Vienna International Conference on Mathematical Modeling, MATHMOD 2009, 2009Conference paper (Refereed)
    Abstract [en]

    Post combustion CO2 capture is corresponding to the most widely applicable option in terms of industrial sectors and is compatible to a retrofit strategy. In addition to the conventional chemical absorption process, membrane gas absorption is considered as one of the promising alternatives to conventional techniques for the CO2 separation from the flue gas of fossil fuels combustion. As a hybrid approach of chemical absorption and membrane separation, it may offer a number of important features, e.g., economical viability due to its larger interfacial area, no flooding at high flow rates, no foaming and channeling, linear scale-up with predictable performance. This paper is to describe and present the state-of-the-art of the R&D efforts on membrane contactors focused on the microporous hallow fiber structure. The operating principles, liquid absorbents selection, influence of membrane wetting phenomenon, membrane materials and module types have been intensively reviewed. Model parameters including economic performance has been evaluated with comparison of other technologies. Technical obstacles of applying membrane contactors in CO2 capture process have also been discussed. The knowledge and application gaps have been examined and identified, thus providing a recommendation for the future studies.

  • 134.
    Lu, Yuexia
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Yu, Xinhai
    East China University of Science and Technology, Shanghai.
    Jia, Jingjing
    East China University of Science and Technology, Shanghai.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Fabrication and characterization of superhydrophobic polypropylene hollow fiber membranes for carbon dioxide absorption2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 90, no 1, p. 167-174Article in journal (Refereed)
    Abstract [en]

    The membrane wetting by amine absorbents results in performance deterioration of membrane gas absorption system for CO2 post-combustion capture. To solve this problem, in this study, the polypropylene membrane fiber was modified by depositing a rough layer on the surface to improve its hydrophobicity. Weighing the coating homogeneity, hydrophobicity and modification process efficiency, the mixture of cyclohexanone and MEK system was considered as the best non-solvent. The contact angle increased dramatically from 122_ to 158_ by the modification, thereby obtaining superhydrophobic membrane surface. The membrane–absorbent interaction results demonstrated that the modification treatment effectively enhanced the stability and maintained the superhydrophobicity of fibers contacting with the absorbent. In addition, continuous CO2 absorption experiments for up to 20 days were carried out in untreated and modified polypropylene hollow fiber membrane contactors, using 1 mol L_1 MEA solution as the absorbent. The long-term system operation results indicated that, even though additional mass transfer resistance was introduced by the surface coating, the modified polypropylene hollow fiber

    membrane contactor was still technically feasible for CO2 capture from the power stations.

  • 135.
    Lu, Yuexia
    et al.
    School of Mechanical and Power Engineering, East China University of Science and.
    Yu, Xinhai
    School of Mechanical and Power Engineering, East China University of Science and.
    Tu, Shan-Tung
    School of Mechanical and Power Engineering, East China University of Science and.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    CO2 capture by the absorption process in membrane contactors2009In: The First International Conference on Applied Energy (ICAE09), 2009Conference paper (Refereed)
    Abstract [en]

    Membrane has a potential to improve the CO2 capture process. In this paper, experimentswere carried out to investigate the impact of amine absorbents on membrane surfaceproperties with polypropylene (PP) fibers immersed in monoethanolamine (MEA) andmethyldiethanolamine (MDEA) aqueous solutions with and without CO2 loading. The surfacemorphological changes of the membrane were examined by using scanning electronmicroscopy (SEM). The experimental results showed that the fibers immersed in the aqueoussolutions without CO2 loading underwent significant deformation than those with CO2 loading,which is mostly linked to the decrease of absorbent concentration with the reaction betweenCO2 and aqueous solutions. It was also found that the morphological changes of membraneimmersed in MDEA were severer than that in MEA due to the lower surface tension of theformer.

  • 136.
    Lu, Yuexia
    et al.
    School of Mechanical and Power Engineering, East China University of Science and.
    Yu, Xinhai
    School of Mechanical and Power Engineering, East China University of Science and.
    Tu, Shan-Tung
    School of Mechanical and Power Engineering, East China University of Science and.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    INFLUENCE OF MEA AND MDEA SOLUTIONS ON SURFACE MORPHOLOGY OF MICROPOROUS POLYPROPYLENE MEMBRANES2009In: The First International Conference on Applied Energy (ICAE09), 2009Conference paper (Refereed)
    Abstract [en]

    Membrane has a potential to improve the CO2 capture process. In this paper, experimentswere carried out to investigate the impact of amine absorbents on membrane surfaceproperties with polypropylene (PP) fibers immersed in monoethanolamine (MEA) andmethyldiethanolamine (MDEA) aqueous solutions with and without CO2 loading. The surfacemorphological changes of the membrane were examined by using scanning electronmicroscopy (SEM). The experimental results showed that the fibers immersed in the aqueoussolutions without CO2 loading underwent significant deformation than those with CO2 loading,which is mostly linked to the decrease of absorbent concentration with the reaction betweenCO2 and aqueous solutions. It was also found that the morphological changes of membraneimmersed in MDEA were severer than that in MEA due to the lower surface tension of theformer.

  • 137.
    Lundh, M.
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Vassileva, Iana
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Wäckelgård, E.
    Comparison between hot water measurements and modelled profiles for Swedish households2008Conference paper (Refereed)
  • 138.
    Lundström, Lukas
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Eskilstuna Energy and Envirorment, Eskilstuna; Eskilstuna kommunfastigheter, Eskilstuna .
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Wallin, Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Helgesson, Jan
    Eskilstuna kommunfastigheter, Eskilstuna .
    Björklund, Ulf
    Eskilstuna Energy and Environment, Eskilstuna .
    Impact on carbon dioxide emissions from energy conservation within Swedish district heating networks2014In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 61, p. 2132-2136Article in journal (Refereed)
    Abstract [en]

    The 100 largest Swedish district heating (DH)-networks were studied on how DH conservation measures impacts CO2-emission rates taking both direct and indirect (i.e. displaced electricity) emissions into account, applying six different methods for the indirect emissions assessment. When the marginal electricity approach is applied on low CO2-emitting DH-networks with a high share of cogenerated electricity, it resulted in assessments that imply that DH conservation leads to higher CO2 emissions. This was not the case with the efficiency method.

  • 139.
    Lönnqvist, Tomas
    et al.
    KTH, Energi och klimatstudier, ECS.
    Olsson, Jesper
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. MDH.
    Espinosa, Cecilia
    Center for Promotion of Sustainable Technology (CPTS).
    Birbuet, Juan Cristóbal
    Center for Promotion of Sustainable Technology (CPTS).
    Silveira, Semida
    KTH.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Persson, Per-Erik
    VAFAB Miljö AB.
    Lindblom, Sandra
    VAFAB Miljö AB.
    Khatiwada, Dilip
    KTH.
    The potential for waste to biogas in La Paz and El Alto in Bolivia2013In: 1st International Water Association Conference on HolisticSludge Management, 2013, Västerås Sweden, 2013Conference paper (Refereed)
    Abstract [en]

    In the cities of La Paz and El Alto, 573 tons of organic material are disposed in landfills every day. These residues can be used to produce biogas and recycle nutrients, thus alleviating environmental impacts related to waste management. Technical solutions are evaluated through a multicriteria analysis with the purpose of defining a strategy for implementing waste-to-biogas in the two cities. As a result, the development for waste-to-biogas-system is defined in three steps. Step 1 consists of an active extraction system of landfill gas in the already existing landfills. Step 2 implies the establishment of a dry-digestion biogas facility based on present waste collection practices, that is, not segregated waste. Step 3 consists of a biogas plant using dry digestion for processing source segregated bio-waste. The economic feasibility of these three steps is evaluated. Despite prevailing fossil fuels subsidies in the country, implementing waste-to-biogas turn out feasible in the country provided the digestate is commercialized as bio-fertilizer or erosion control material and additional services such as waste collection and deposition are computed in the total economy of the biogas production plant.

  • 140. M, Naqvi
    et al.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Black liquor gasification integrated in pulp and paper mills: A critical review2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 21, p. 8001-8015Article in journal (Other academic)
  • 141.
    Md Lokman, Hosain
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Bel Fdhila, Rebei
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Sand, U.
    Engdahl, J.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    CFD Modeling of Real Scale Slab Reheating FurnaceConference paper (Refereed)
  • 142.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    BIO-METHANE PRODUCTION THROUGH DIFFERENT BIOMASS GASIFIERS2013Conference paper (Refereed)
    Abstract [en]

    Considering sustainability of energy resources and environmental concerns have led to activities all over the world seeking alternatives for current methods of fuel production. Gasification of biomass to supply bio-methane is one of those options. Bio-methane is carbon neutral and meets the needs of combustion engines in vehicles.Focusing on vehicle fuel production reveals the need for wide research to understand different types of gasifiers in order to find the possibilities for more methane production.In this paper data collected from different experimental setups are summarized and analyzed.Fluidized bed gasifiers show higher methane concentrations in the produced gas while entrained flow and downdraft gasifiers may be the least suitable types for high methane yields.Heating value of the product gas and cold gas efficiency are also studied as the important parameters for evaluating the characteristics of the product gas. This analysis shows that by increasing the equivalence ratio, the heating value of the product gas decreases while the efficiency may not follow the same trend.

  • 143.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Mälardalen Högskola.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    EVALUATION OF DIFFERENT BIOMASS GASIFICATION MODELING APPROACHES FOR FLUIDIZED BED GASIFIERS2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 91, p. 69-82Article in journal (Refereed)
    Abstract [en]

    To develop a model for biomass gasification in fluidized bed gasifiers with high accuracy and generality that could be used under various operating conditions, the equilibrium model (EM) is chosen as a general and case-independent modeling method. However, EM lacks sufficient accuracy in predicting the content (volume fraction) of four major components (H2, CO, CO2 and CH4) in product gas. In this paper, three approaches—MODEL I, which restricts equilibrium to a specific temperature (QET method); MODEL II, which uses empirical correlations for carbon, CH4, C2H2, C2H4, C2H6 and NH3 conversion; and MODEL III, which includes kinetic and hydrodynamic equations—have been studied and compared to map the barriers and complexities involved in developing an accurate and generic model for the gasification of biomass.

    This study indicates that existing empirical correlations can be further improved by considering more experimental data. The updated model features better accuracy in the prediction of product gas composition in a larger range of operating conditions. Additionally, combining the QET method with a kinetic and hydrodynamic approach results in a model that features less overall error than the original model based on a kinetic and hydrodynamic approach.

  • 144.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Mälardalen Högskola.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    THE EFFECT OF INCLUDING HYDRODYNAMICS FOR MODELING ATMOSPHERIC BUBBLING FLUIDIZED BED GASIFIERS2014Conference paper (Refereed)
  • 145.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Skvaril, Jan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    The influence of different parameters on biomass gasification in circulating fluidized bed gasifiers2016In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 126, p. 110-123Article in journal (Refereed)
    Abstract [en]

    The mechanism of biomass gasification has been studied for decades. However, for circulating fluidized bed (CFB) gasifiers, the impacts of different parameters on the gas quality and gasifiers performance have still not been fully investigated. In this paper, different CFB gasifiers have been analyzed by multivariate analysis statistical tools to identify the hidden interrelation between operating parameters and product gas quality, the most influencing input parameters and the optimum points for operation. The results show that equivalence ratio (ER), bed material, temperature, particle size and carbon content of the biomass are the input parameters influencing the output of the gasifier the most. Investigating among the input parameters with opposite impact on product gas quality, cases with optimal gas quality can result in high tar yield and low carbon conversion while low tar yield and high carbon conversion can result in product gas with low quality. However using Olivine as the bed material and setting ER value around 0.3, steam to biomass ratio to 0.7 and using biomass with 3 mm particle size and 9 wt% moisture content can result in optimal product gas with low tar yield.

  • 146.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Mälardalen Högskola.
    Skvaril, Jan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    INVESTIGATION OF EFFECTIVE PARAMETERS ON BIOMASS GASIFICATION IN CIRCULATING FLUIDIZED BED GASIFIERS2015Conference paper (Refereed)
  • 147.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Skvaril, Jan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Investigation of Most Effective Parameters on Biomass Gasufication in Circulating Fluidized bed Gasifiers2015In: Forest and Plant Bioproducts Division 2015 - Core Programming Area at the 2015 AIChE Annual Meeting, 2015, p. 189-200Conference paper (Refereed)
  • 148.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Modeling and Simulation of Short Circuit Current and TRV to Develop a Synthetic Test System for Circuit Breakers2014In: Proceedings of the 55th Conference on Simulation and Modelling (SIMS 55), 2014, Vol. 108, p. 285-292Conference paper (Refereed)
    Abstract [en]

    A parallel injection of short circuit current and transient voltage to medium and high voltage circuit breaker (CB) by a synthetic model is studied. Transient recovery voltage is created by a capacitor bank and is applied to CB. Also short circuit current is supplied by a 20/0.765 Kv short circuit transformer. Texas DSP is used as controller and programmed in code composer.To test of circuit breakers by synthetic test equipments, an accurate control system can satisfy the test criterion. An optical triggered spark gap has been used to interrupt short circuit current and to initialize of transient recovery voltage (TRV) that is applied across the contacts of circuit breaker. Modeled results are verified by a laboratory based synthetic test system. Test object CB is a 24 Kv, 25 KA with vacuum type chamber. To find a desired sequence to open/close of backup- test object and auxiliary circuit breakers within appropriate time to inject of recovery voltage is main goal of the presented paper. Modeling and simulation has been done in MATLAB software. Test procedure has been done under IEC 62271-100 , 62271-101.

  • 149.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Power transformer parameter estimation with on-line data aquisition using the Kalman filter method2008Conference paper (Refereed)
  • 150.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, Department of Public Technology.
    Mahmoudi, Jafar
    Mälardalen University, Department of Public Technology.
    Dahlquist, Erik
    Mälardalen University, Department of Public Technology.
    Process control in steel core production to reduce of power losses in electrical machines and transformers: Process Control2009In: Proceedings MATHMOD 09 Vienna, Vienna- Austria: Mathematical Modelling (MATHMOD) 2009 , 2009Conference paper (Refereed)
    Abstract [en]

    The main aim of cold rolling is reduction of strips to the desired final thickness. As the cold rolled strip is being manufactured from hot rolled strip, the uniformity of width, thickness, hardness, etc. are all now intended for improvement.  To reach to this target, need to abound control system to reach the higher quality of slabs.  It should satisfy the several factors, as regards geometrical, mechanical, chemical and surface properties.

    Process control has taken advantage of new measurement equipments, new control actuators and algorithms. Automation and automatic process control can advance the quality further than what is achievable by manual control. This is an important desideration in rolling industry that rolling of slabs needs advanced and optimized process control to increase the productivity and reduction of the variations in the final properties.

    A typical cold rolling stand performs one step in a chain of processes in the cold rolling mill, which can include pickling, rolling, annealing, temper rolling and downstream processes. All these processes contribute to the final properties of the strips. When the main process or the main objective is well controlled, it is important to continue with the other processes. In continuous annealing furnaces, the temperature controls the mechanical properties, but temperature differences and bending around rollers change the flatness. Temper rolling needs the same flatness control as other cold rolling processes. Cooling and lubrication can affect several properties of the strips.

    Precise general control of the strip in a cold steel rolling mill will be discussed in this article.

    Typically, the rolling process is modelled with numerical techniques. But these are not appropriate for a controller design, because they are too difficult. Thus, a linear mathematical model for the rolling process is presented here, which describes the interaction of the required influencing parameters. The attempt leads to numerically professional algorithms, which are essential to run in a real-time situation. With the help of these linear descriptions, the vital elements for the control are investigated. Modern rolling mills are equipped with a servo-hydraulic gap adjustment system, eccentricity control of the rolls, thickness, speed, force and tension controls.

    A model to optimize of the control design process and increasing of accuracy is presented. In this way using the process transfer function in system at different control mode like to thickness, flatness, shape and etc designed a PID and PI optimized controller with using of the best optimization method, final properties increased. The measurements are used to verify the model approach and to detect the most significant sources of disturbances.

    A new linearised numerical model for the rolling process which is suitable for closed loop control has been developed. The model is based on the calculation of the operating point using an available numerical method, followed by determining the partial derivatives at the operating point with respect to all input parameters. Finally, the partial derivatives are combined using superposition to describe the behaviour of the complete system. In this manner, the changes in the output parameters can be determined for small changes in the input parameters. This calculation is numerically efficient and suitable for use in closed loop control.

    Moreover, the roll eccentricity problem and the possibilities to perform compensation will be explained here. Due to the great variety of solutions, a classification of the methods will be sketched. The basic properties of these classes are discussed. Then, a special solution is presented, which has proved its worth already in a practical application. The investigation of its properties is proposed to be typical for the every class, to which the method belongs.

    Finally measurement data which can be used to verify the new model will be performed. The model has been incorporated as a simulation system developed by the authors who enable the simulation of a multi-pass single stand rolling process. To get practical information about the rolling process, a data logging system was developed and installed in Sura AB for data collection.

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