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  • 1.
    Nwachukwu, Chinedu M
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Biomass-based gas use in Swedish iron and steel industry: Supply chain and process integration considerations2020In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, p. 2797-2811Article in journal (Refereed)
    Abstract [en]

    Substitution of fossil gaseous fuels with biomass-based gases is of interest to the iron and steel industry due to its role in the mitigation of anthropogenic CO2emissions. In switching from fossil fuels to biomass-based gases, a systems analysis of the full value chain from biomass supply to the production and supply of final gas products becomes crucial. This study uses process and heat integration methods in combination with a supply chain evaluation to analyse full value chains of biomass-based gases for fossil gas replacement within the iron and steel industry. The study is carried out as a specific case study in order to understand the implications of utilizing bio-syngas/bio-SNG as heating fuels in iron- and steel-making, and to provide insights into the most sensitive parameters involved in fuel switching. The results show a significant cost difference in the fuel production of the two gas products owing to higher capital and biomass use in the bio-SNG value chain option. When tested for sensitivity, biomass price, transportation distance, and capital costs show the most impact on fuel production costs across all options studied. Trade-offs associated with process integration, plant localisation, feedstock availability and supply were found to varying extents.

  • 2.
    Sandberg, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Krook-Riekkola, Anna
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A bottom-up study of biomass and electricity use in a fossil free Swedish industry2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 167, p. 1019-1030Article in journal (Refereed)
    Abstract [en]

    While previous research has focused on single industrial sectors or specific technologies, this study aims to explore the impacts of various industrial technology options on the use of biomass and electricity in a future fossil free Swedish industry. By building a small optimization model, that decomposes each industrial sector into site categories by type and technology to capture critical synergies among industrial processes. The results show important synergies between electrification, biomass and CCS/U (sequestration of CO2 is required to reach net-zero emissions). Reaching an absolute minimum of biomass use within the industry has a very high cost of electricity due to the extensive use of power-to-gas technologies, and minimising electricity has a high cost of biomass due to extensive use of CHP technologies. Meanwhile, integrated bio-refinery processes are the preferable option when minimising the net input of energy. There is, thus, no singular best technology, instead the system adapts to the given circumstances showing the importance of a detailed bottom-up modelling approach and that the decarbonisation of the industry should not be treated as a site-specific problem, but rather as a system-wide problem to allow for optimal utilisation of process synergies.

  • 3.
    Toffolo, Andrea
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, A.
    University of Padova, Padova, Italy.
    A practical tool to generate complex energy system configurations based on the synthsep methodology2019In: International Journal of Thermodynamics, ISSN 1301-9724, Vol. 22, no 1, p. 45-53Article in journal (Refereed)
    Abstract [en]

    Traditional fossil fueled power plants are commonly based on steam Rankine cycle or Brayton Joule cycle. Using water or air as working fluid is obviously the most obvious choice for the wide availability of these substances in nature. However, the scarcity of natural energy sources and the strong need of reducing environmental impact have necessarily drawn the research to new energy systems configurations operating with other working fluids, which are able to recover lower temperature sources, such as Sun or industrial wasted heat. The variety of new working fluids (refrigerants or organic fluids) widens the choice to a variety of configurations that can be tailored to the specific source characteristics and boundary constraints. It is not always easy or even possible to conceive the best configuration for given specifications with the mere experience of a common designer. To design a new system configuration, the designer normally uses some “non-codified rules” deriving from his knowledge of basic thermodynamics and energy engineering. This paper aims instead at showing a practical tool that is based on a new methodology, named SYNTHSEP, to generate new energy system configurations. This methodology starts from the simple thermodynamic cycles operated by a given fluid made up of the four fundamental processes (compression, heating, expansion and cooling) and uses a rigorous set of codified rules to build the final system configuration. The paper presents the basics of the new methodology and how it has been implemented in a practical tool that simply requires the information about the elementary cycles and their shared processes as input data.

  • 4.
    Mesfun, Sennai
    et al.
    International Institute for Applied Systems Analysis (IIASA), Laxenburg.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindbergh, Göran
    School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Lagergren, Carina
    School of Chemical Science and Engineering, KTH, Stockholm.
    Engvall, Klas
    School of Chemical Science and Engineering, KTH, Stockholm.
    Integration of an electrolysis unit for producer gas conditioning in a bio-synthetic natural gas plant2019In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 141, no 1, article id 012002Article in journal (Refereed)
    Abstract [en]

    Producer gas from biomass gasification contains impurities like tars, particles, alkali salts, and sulfur/nitrogen compounds. As a result, a number of process steps are required to condition the producer gas before utilization as a syngas and further upgrading to final chemicals and fuels. Here, we study the concept of using molten carbonate electrolysis cells (MCEC) both to clean and to condition the composition of a raw syngas stream, from biomass gasification, for further upgrading into synthetic natural gas (SNG). A mathematical MCEC model is used to analyze the impact of operational parameters, such as current density, pressure and temperature, on the quality and amount of syngas produced. Internal rate of return (IRR) is evaluated as an economic indicator of the processes considered. Results indicate that, depending on process configuration, the production of SNG can be boosted by approximately 50-60% without the need of an additional carbon source, i.e., for the same biomass input as in standalone operation of the GoBi-Gas plant. Copyright

  • 5.
    Fischer, Robert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Elfgren, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Energy Supply Potentials in the Northern Counties of Finland, Norway and Sweden towards Sustainable Nordic Electricity and Heating Sectors: A Review2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 4, article id 751Article in journal (Refereed)
    Abstract [en]

    The lands in the northernmost corner of Europe present contradictory aspects in their social and economic development. Urban settlements are relatively few and small-sized, but rich natural resources (minerals, forests, rivers) attract energy-intensive industries. Energy demand is increasing as a result of new investments in mining and industries, while reliable energy supply is threatened by the planned phase out of Swedish nuclear power, the growth of intermittent power supplies and the need to reduce fossil fuel consumption, especially in the Finnish and Norwegian energy sectors. Given these challenges, this paper investigates the potentials of so far unexploited energy resources in the northern counties of Finland, Norway and Sweden by comparing and critically analyzing data from statistic databases, governmental reports, official websites, research projects and academic publications. The criteria for the technical and economic definition of potentials are discussed separately for each resource. It is concluded that, despite the factors that reduce the theoretical potentials, significant sustainable techno-economic potentials exist for most of the resources, providing important insights about the possible strategies to contribute to a positive socio-economic development in the considered regions.

  • 6.
    Toffolo, Andrea
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rech, S.
    Department of Industrial Engineering, University of Padova, Italy.
    Lazzaretto, A.
    Department of Industrial Engineering, University of Padova, Italy.
    Generation of Complex Energy Systems by Combination of Elementary Processes2018In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 140, no 11, article id 112005Article in journal (Refereed)
    Abstract [en]

    The fundamental challenge in the synthesis/design optimization of energy systems is the definition of system configuration and design parameters. The traditional way to operate is to follow the previous experience, starting from the existing design solutions. A more advanced strategy consists in the preliminary identification of a superstructure that should include all the possible solutions to the synthesis/design optimization problem and in the selection of the system configuration starting from this superstructure through a design parameter optimization. This top–down approach cannot guarantee that all possible configurations could be predicted in advance and that all the configurations derived from the superstructure are feasible. To solve the general problem of the synthesis/design of complex energy systems, a new bottom–up methodology has been recently proposed by the authors, based on the original idea that the fundamental nucleus in the construction of any energy system configuration is the elementary thermodynamic cycle, composed only by the compression, heat transfer with hot and cold sources and expansion processes. So, any configuration can be built by generating, according to a rigorous set of rules, all the combinations of the elementary thermodynamic cycles operated by different working fluids that can be identified within the system, and selecting the best resulting configuration through an optimization procedure. In this paper, the main concepts and features of the methodology are deeply investigated to show, through different applications, how an artificial intelligence can generate system configurations of various complexity using preset logical rules without any “ad hoc” expertise.

  • 7.
    Lazzaretto, Andrea
    et al.
    Department of Industrial Engineering, University of Padova.
    Manente, Giovanni
    University of Padova, Department of Industrial Engineering.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    SYNTHSEP: A general methodology for the synthesis of energy system configurations beyond superstructures2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 147, p. 924-949Article in journal (Refereed)
    Abstract [en]

    The proper choice of the energy system configuration and design parameters, generally named “synthesis/design problem”, is only rarely straightforward because of the many variables involved. The goal of a standard for the generation of new system configurations has recently led to superstructures that potentially include all possible configurations, among which the optimum one, yet the ability of defining in advance such superstructures is a fundamental limit of this technique. To overcome this problem a bottom-up methodology is proposed, which relies on the basic idea that the system configuration is certainly based on one or more thermodynamic cycles that may share some processes or be combined in a cascade form. Accordingly, all the possible ways of combining elementary cycle processes into meaningful system configurations are first identified using a comprehensive and rigorous set of rules. An optimization is then performed in which the search space consists of all the obtainable configurations and associated design parameters. The paper shows all steps of this original synthesis/design optimization methodology and its effectiveness in the search for the best two-pressure level ORC system configuration. The optimum results obtained using different working fluids and temperatures of the heat source allow general design guidelines to be identified.

  • 8.
    Nwachukwu, Chinedu M
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grip, Carl-Erik
    Wang, Chuan
    Swerea MEFOS, Process Integration Department.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Systems analysis of sawmill by-products gasification towards a bio-based steel production2018In: ECOS 2018: Proceedings of the 31st International Conference on Efficiency, Cost, Optimisation, Simulation and Environmental Impact of Energy Systems / [ed] José Carlos Teixeira, Ana Cristina Ferreira, Ângela Silva, Senhorinha Teixeira, Universidade do Minho. Departamento de Engenharia Mecânica Campus Azurém, Guimarães Portugal , 2018Conference paper (Refereed)
  • 9.
    Gobbato, Paolo
    et al.
    Veil Energy Srl, Via Siemens 19, Bolzano.
    Masi, Massimo
    Department of Management and Engineering, University of Padova.
    Lazzaretto, Andrea
    Department of Industrial Engineering, University of Padova.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Analysis of the natural acoustic modes of a gas turbine combustor using isothermal CFD simulations2017In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 126, p. 489-499Article in journal (Refereed)
    Abstract [en]

    Thermoacoustic instabilities usually result from the coupling between the oscillatory heat release and one or more natural acoustic modes of the combustion system. When the shifting of system frequencies caused by the unsteady heat release is limited, the calculation of natural modes allows to identify which of them are excited by the flame once changes in flow temperature and composition due to combustion are considered. In this paper, isothermal computational fluid dynamics simulations are performed to predict the natural modes of a heavy-duty gas turbine combustor in reactive conditions. Combustion and heat transfer are neglected in the numerical analysis to simplify the model and limit the computational effort. The natural frequencies resulting from isothermal simulations are then corrected using a rather basic post-processing approach to account for temperature and gas composition changes due to combustion process. Frequency and amplitude of the calculated modes are finally compared to experimental measurements to evaluate the ability of the acoustic analysis to capture frequency and spatial shape of the combustor natural modes excited by the flame

  • 10.
    Toffolo, Andrea
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rech, Sergio
    Universita degli Studi di Padova, Interdepartmental Center “Giorgio Levi Cases” for Energy Economics and Technology, Padua, Italy.
    Lazzaretto, Andrea
    Universita degli Studi di Padova, Department of Industrial Engineering, Padua, Italy.
    Combination of elementary processes to form a general energy system configuration2017In: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE): Proceedings (IMECE), ASME Press, 2017, article id IMECE2017-71653Conference paper (Refereed)
    Abstract [en]

    The fundamental challenge in the synthesis/design optimization of energy conversion systems is the definition of the system configuration and design parameters. The traditional way to operate in system engineering practice is to follow the previous experience, starting from design solutions that already exist. A more advanced strategy consists in the preliminary identification of a superstructure that should include all the possible solutions to the synthesis/design optimization problem, and in the selection of the system configuration starting from this superstructure through a design parameter optimization. This top-down approach cannot guarantee that all possible configurations could be predicted in advance and that all the configurations derived from the superstructure are really feasible. To solve the general problem of the synthesis/design of complex energy systems a new bottom-up methodology is proposed, based on the original idea that the fundamental nucleus in the construction of any energy system configuration is the elementary thermodynamic cycle (compression, heat transfer with the hot source, expansion, heat transfer with the cold source). So, any configuration can be built by generating, according to a rigorous set of rules, all the combinations of the elementary thermodynamic cycles operated by different working fluids that can be identified within the system, and selecting the best resulting configuration through an optimization procedure. In this paper a deep analysis of the major features of the methodology is presented to show, through different examples of applications, how an artificial intelligence is able to generate system configurations of various complexity using preset logical rules without any "ad hoc" expertise. 

  • 11.
    Vesterlund, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Design optimization of a district heating network expansion: a case study for the town of Kiruna2017In: Applied Sciences, E-ISSN 2076-3417, Vol. 7, no 5, article id 488Article in journal (Refereed)
    Abstract [en]

    The urbanization of new areas beyond the existing perimeter of a town implies the expansion of several infrastructures, including the district heating network. The main variables involved in the design of the district heating network expansion are the layout of the new pipes, their diameters, and the capacity of the new heat production sites that are required to satisfy the increased demand of room heating and hot tap water. In this paper, a multi-objective evolutionary algorithm is applied to the minimization of the costs related to the expansion of the district heating network of the town of Kiruna, in northern Sweden. The results show that the spectrum of the optimal design compromises between investment costs for the new pipes and the new heat generation site on one side, and operating costs due to overall fuel consumption and pumping power in the network on the other. The presented methodology is a tool meant for the decision makers in the company who own the district heating network, to evaluate all the possible best design alternatives before making a decision.

  • 12.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), Laxenburg.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), Laxenburg.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindbergh, Göran
    School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Lagergren, Carina
    School of Chemical Science and Engineering, KTH, Stockholm.
    Engvall, Klas
    School of Chemical Science and Engineering, KTH, Stockholm.
    Integration of an electrolysis unit for producer gas conditioning in a bio-SNG plant2017In: 30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2017, International Measurement Confederation (IMEKO) , 2017Conference paper (Refereed)
    Abstract [en]

    Producer gas from biomass gasification contains impurities like tars, particles, alkali salts and sulfur/nitrogen compounds. As a result a number of process steps are required to condition the producer gas before utilization as a syngas and further upgrading to final chemicals and fuels. Here, we study the concept of using molten carbonate electrolysis cells (MCEC) both to clean and to condition the composition of a raw syngas stream, from biomass gasification, for further upgrading into SNG. A mathematical MCEC model is used to analyze the impact of operational parameters, such as current density, pressure and temperature, on the quality and amount of tailored syngas produced. Investment opportunity is evaluated as an economic indicator of the processes considered. Results indicate that the production of SNG can be boosted by approximately 50% without the need of an additional carbon source, i.e. for the same biomass input as in standalone operation of the GoBiGas plant.

  • 13.
    Vesterlund, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Optimization of multi-source complex district heating network, a case study2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 126, p. 53-63Article in journal (Refereed)
    Abstract [en]

    The level of complexity for a district heating network increases with the maturity of the network, and this affects the pattern of the distribution of the hot water from the heat production sites to the end users. The majority of district heating systems are also multi-source networks, typically supported with heat from one main production site and other smaller satellite sites that are activated when required. In general, local energy companies have a lack of knowledge regarding how a meshed network behaves when different production sites are operated. The schedule of heat generation at the different sites is often based on staff experience and some general rules of thumb.

    In this paper a method for modeling and simulating complex district networks is further developed in order to optimize the total operating costs of a multi-source network, with constraints on the pressure and temperature levels in the user areas and on the heat generation characteristics at each production site.

    The optimization results show that the usage of the cheapest resources is preferred to a distributed generation of heat, even if some of the pipes may exceed the recommended thermal load capacity. The main site water supply temperature is found to be the lowest allowed by the constraint on the temperature of the water supplied to the end users, since the decrease of the costs associated with the lower thermal losses in the network is not counterbalanced by the increase of those associated with the pumping power of a larger water mass flow rate.

  • 14.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Anderson, Jan-Olof
    Process Energy Engineering, Solvina, SE-42130 Västra Frölunda.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Integrated SNG Production in a Typical Nordic Sawmill2016In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 9, no 5, article id 333.Article in journal (Refereed)
    Abstract [en]

    Advanced biomass-based motor fuels and chemicals are becoming increasingly important to replace fossil energy sources within the coming decades. It is likely that the new biorefineries will evolve mainly from existing forest industry sites, as they already have the required biomass handling infrastructure in place. The main objective of this work is to assess the potential for increasing the profit margin from sawmill byproducts by integrating innovative downstream processes. The focus is on the techno-economic evaluation of an integrated site for biomass-based synthetic natural gas (bio-SNG) production. The option of using the syngas in a biomass-integrated gasification combined cycle (b-IGCC) for the production of electricity (instead of SNG) is also considered for comparison. The process flowsheets that are used to analyze the energy and material balances are modelled in MATLAB and Simulink. A mathematical process integration model of a typical Nordic sawmill is used to analyze the effects on the energy flows in the overall site, as well as to evaluate the site economics. Different plant sizes have been considered in order to assess the economy-of-scale effect. The technical data required as input are collected from the literature and, in some cases, from experiments. The investment cost is evaluated on the basis of conducted studies, third party supplier budget quotations and in-house database information. This paper presents complete material and energy balances of the considered processes and the resulting process economics. Results show that in order for the integrated SNG production to be favored, depending on the sawmill size, a biofuel subsidy in the order of 28–52 €/MWh SNG is required.

  • 15.
    Vesterlund, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Optimization of multi-source complex district heating network: a case study2016In: Proceeding of 29th International Conference on efficiency, Cost, Optimization, Simulation and Enviromental Impact of Energy Systems, 2016Conference paper (Refereed)
    Abstract [en]

    The level of complexity for a district heating network increases with the maturity of the network, and this affects the pattern of the distribution of the hot water from the heat production sites to the end users. The majority of district heating systems are also multi-source networks, typically supported with heat from one main production site and other smaller satellite sites that are activated when required. In general, local energy companies have a lack of knowledge regarding how a meshed network behaves when different production sites are operated. The schedule of heat generation at the different sites is often based on staff experience and some general rules of thumb.

    In this paper a method for modeling and simulating complex district networks is further developed in order to optimize the total operating costs of a multi-source network, with constraints on the pressure and temperature levels in the user areas and on the heat generation characteristics at each production site.

    The optimization results show that the usage of the cheapest resources is preferred to a distributed generation of heat, even if some of the pipes may exceed the recommended thermal load capacity. The main site water supply temperature is found to be the lowest allowed by the constraint on the temperature of the water supplied to the end users, since the decrease of the costs associated with the lower thermal losses in the network is not counterbalanced by the increase of those associated with the pumping power of a larger water mass flow rate.

  • 16.
    Vesterlund, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Simulation and analysis of a meshed district heating network2016In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 122, p. 63-73Article in journal (Refereed)
    Abstract [en]

    The flow distribution in a district heating network tends to become no longer obvious when system design is developed and its complexity increased. As a consequence, the network owner, often the local energy company, is in need of a simulation program to have the possibility of analysing network behaviour and expand the understanding about the operation of district heating system. In this paper, a simulation tool developed in MATLAB/Simulink is applied in order to analyse the flow distribution in the district heating network of the town of Kiruna (Sweden). The network in Kiruna has been developing since the 60s and is today a complex network with a meshed structure, i.e. it is formed by a set of loops from which secondary branches depart. The simulation tool is part of a methodology that has specifically been developed to analyse the flow pattern in such kind of networks without altering their physical structure, and it is expected to be a valuable tool for the redesign of the network in the forthcoming relocation of some of the urban districts. The results about the current network configuration show that only a few pipes in the network are exceeding the levels of heat flow recommended by pipe manufacturers. The largest drops in pressure and temperature from the heat production site to the nodes serving the main consumer areas are within 1.2 bar and 9 °C in the days of highest demand.

  • 17.
    Grip, Carl-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Östman, Marianne
    Swerea MEFOS AB.
    Sandberg, Erik
    Center for Process Integration in Steelmaking, Swerea MEFOS, Luleå, Luleå tekniska universitet.
    Orre, Joel
    Swerea MEFOS AB.
    Forestry meets Steel: A system study of the possibility to produce DRI (directly Reduced Iron) using gasified biomass2015In: ECOS 2015: 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems , 2015Conference paper (Refereed)
    Abstract [en]

    The main production of primary Iron from ore is now made by reduction using fossil reductants, either by producing hot metal in the blast furnace process or as directly reduced iron with natural gas as most common reductant. The climate gas impact would be improved if at least part of the reductants could be produced from Biomass. One possibility could be to use gasified Biomass to produce DRI (Directly Reduced Iron). This is studied in a cooperative project where LTU, MEFOS, ETC and five industries in the areas forestry & pulp, mining, iron and gas are involved. The investigation is made in four parts where the first one is on the supply of biomass. A large amount of Biomass has to be delivered into a single site to exchange a large amount of fossil reductant. Also, forestry by-products should be used as most of the round wood is reserved for other uses. Harvesting, logistics and economics are considered. The second part is on the gasification of the biomass, where the aim is to use to produce hot gas that can be used directly. Pilot experiments are carried out using oxygen in an entrained flow gasifier. The third part is on the metallurgical processes, where reduction tests are carried out with gas that can be produced in the gasifier. The limitations of the gas content are studied as well as the effect on DRI. Also the suitability of the DRI product is evaluated. The fourth part of the project uses process integration to model the whole process chain. The results from the other project parts are used to build the system model. It is then used for technical economic optimization the whole system harvesting-transport-gasifier-direct reduction-use of DRI. The first use of the system model has been to find the best supply road (harvesting, pretreatment and transport) for a chosen production case The simulations indicated that the supply of residuals is possible but will need material from a large part of the north Sweden wood area, and that a relatively large amount of gas recirculation is needed. The continuing work is focused on further development of the optimization tool and the use of it for more extensive studies of the trade-off between parameters of metallurgy, gasification and supply. The result can be important for evaluation of future industrial applications. It could also help in understanding the effect of governmental control instruments. The paper will mainly focus on the process integration study.

  • 18.
    Grip, Carl-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Salman, Hassan
    HKS Energy, Sveaskog.
    Andersson, Lars I.
    Billerudkorsnäs AB.
    Ritzen, Ola
    AGA AB/Linde Gas.
    Tottie, Magnus
    LKAB.
    Robinnsson, Ryan
    Höganäs AB.
    Winnikka, Henrik
    Energy Technology Centre, Piteå.
    Östman, Marianne
    Swerea MEFOS AB.
    Sandberg, Erik
    Swerea MEFOS AB.
    Forestry meets steel: a technoeconomic study of the possible DRI production using biomass2015Conference paper (Refereed)
    Abstract [en]

    The possibility to produce DRI using gasified Biomass is studied in a cooperative project. LTU, MEFOS, ETC and five industries in the areas forestry & pulp, mining, iron and gas are involved. The production chain Biomass production and distribution -Gasification-DRI production-DRI use is investigated in four work packages:WP1: Biomass supply: A large amount of Biomass has to be delivered into a single site to exchange a large amount of fossil reductant. It is important to use forestry by- products as a major part of round wood is reserved for other uses. Harvesting, logistics and economics have to be considered. Available data were collected and used to make a system model on harvesting treatment and transport. The simulations indicated that the supply of residuals is possible but will need material from a large part of the north Sweden wood area. WP2: Gasification. The aim is to use to produce hot gas that can be used directly. Pilot experiments are carried out using oxygen in an entrained flow gasifier. WP3: Metallurgical processes. Reduction tests are carried out with gas that can be produced in the gasifier. The limitations of the gas content are studied as well as the effect on DRI. Also the suitability of the DRI product is evaluated WP4: Process integration. A system model is built using the results from work packages 1-3 and used for technical economic optimization the whole system harvesting-transport-gasifier-direct reduction- use of DRI. The process chain is technically possible; however there are problems to be solved, e.g., gas quality vs. demands from DRI process, Biomass supply and logistics. The result is important to evaluate for industrial application, but also to get information of the effect of different governmental control instruments.

  • 19.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Andersson, Jan Olof
    Process Energy Engineering, Solvina, SE-42130 Västra Frölunda.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Integrated SNG production in a typical Nordic sawmill2015In: ECOS 2015: 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems , 2015Conference paper (Refereed)
    Abstract [en]

    Advanced biomass based motor fuels and chemicals are becoming increasingly important to replace fossil energy sources within the coming decades. It is likely that the new biorefineries will evolve mainly from existing forest industry sites as they already have the required biomass handling infrastructure in place. The main objective of this work is to assess the potential for increasing the profit margin from sawmill byproducts by integrating innovative downstream processes. The focus is on the techno-economic evaluation of an integrated site for bio-SNG production. The option of using the syngas in a b-IGCC for the production of electricity (instead of SNG) is also considered for comparison. The process flowsheets that are used to analyse the energy and material balances are modelled in MATLAB and Simulink. A mathematical process integration model of a typical Nordic sawmill is used to analyse the effects on the energy flows in the overall site as well as to evaluate the site economics. Different plant sizes have been considered in order to assess the economy-of-scale effect. The technical data required as input are collected from the literature and, in some cases, from experiments. The investment cost is evaluated on the basis of conducted studies, third party supplier budget quotations and in-house database information. This paper presents complete material and energy balances of the considered processes and the resulting process economics.

  • 20.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Integrating the processes of a Kraft pulp and paper mill and its supply chain2015In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 103, p. 300-310Article in journal (Refereed)
    Abstract [en]

    This paper investigates the possibility of combining different forest industries (a pulp and paper mill, its supply chain, and a wood-pellet plant) into an integrated industrial site in which they share a common heat and power utility. Advanced process integration and optimization techniques are used to study the site from both material and energy viewpoints. An existing pulp and paper mill is used as the site core plant and its pulp and paper production rates are kept fixed as they are in reality, while the other material flow links among the plants are based on the current industrial situation in Sweden. Different scenarios are evaluated in order to reflect the two main objectives that can be pursued (increased electricity production or biomass resource saving) and the two technologies that can be considered for the shared CHP system (boilers and product gas fired gas turbines). The corresponding non-integrated (standalone) configurations are compared to these scenarios to quantify the potential benefits of the integration. Investment opportunity is also calculated for the considered scenarios as an indicator of the economic convenience

  • 21.
    Vesterlund, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Simulation and analysis of a meshed district heating network2015In: ECOS 2015: 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems , 2015Conference paper (Refereed)
  • 22.
    Tanaka, Yasuto
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    Mesfun, Sennai
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Tamura, Yutaka
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1 Ookayama.
    Yoshikawa, Kunio
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Tokyo Institute of Technology, Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology.
    Thermodynamic performance of a hybrid power generation system using biomass gasification and concentrated solar thermal processes2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 160, p. 664-672Article in journal (Refereed)
    Abstract [en]

    This paper describes the investigation of a hybrid power production system from biomass and solar energy. This paper suggests integration through heat exchanger network as a useful approach to obtain the synergy between biomass and solar. Biomass is first gasified in a bubbling fluidized bed (BFB) gasifier, and then syngas is used in a gas turbine. Excess heat exists in this sub-system and concentrated solar thermal process (CSTP) while there is a demand of steam for generating gasifying agent. Steam Rankine cycle exploits the heat created by these thermal streams to generate power while satisfying the steam demands. Thermodynamic performance was analyzed by process modelling with a semi-kinetic model of BFB gasifier and pinch analyses. The composition and temperature of gasifying agent showed some effect on the overall efficiency of the system. Higher overall efficiency of the system was achieved at higher temperature and higher O2 fraction in the O2-steam mixture as gasifying agent. The increase in thermal input from CSTP had positive effect on overall efficiency of the hybrid system until thermal input from CSTP becomes dominant against thermal stream related to the gasifier and the gas turbine.

  • 23.
    Toffolo, Andrea
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, Andrea
    University of Padova, Department of Industrial Engineering.
    Manente, Giovanni
    University of Padova, Department of Industrial Engineering.
    Paci, Marco
    ENEL Engineering and Innovation, via Andrea Pisano 120, 56126 Pisa.
    A multi-criteria approach for the optimal selection of working fluid and design parameters in Organic Rankine Cycle systems2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 121, p. 219-232Article in journal (Refereed)
    Abstract [en]

    The selection of the cycle configuration, working fluid and operating parameters is crucial for the economic profitability of Organic Rankine Cycle systems using low to medium temperature heat sources. The aim of this paper is to show a method that improves this selection taking into account several criteria at a time: an original thermodynamic optimization procedure of the system configuration and design parameters which explores all possible configurations, the design options around the optimum values of the objective function, an economic modeling technique validated on real cost data, and the consideration of the off-design behavior. The method is applied to comparatively assess the performance of two working fluids, isobutane and R134a, in the temperature interval between 130 and 180 °C. The results show that the optimal cycle configuration is in most cases subcritical for isobutane and supercritical recuperated for R134a. The maximum power output of R134a is higher than isobutane for all the temperatures considered. The analysis of the objective function around the optimum shows the extent of the best range of turbine inlet pressures and enthalpies. These results highlight alternative design conditions to those maximizing the power output which might be preferred for technical and economic reasons.

  • 24.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A synthesis/design optimization algorithm for Rankine cycle based energy systems2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 66, p. 115-127Article in journal (Refereed)
    Abstract [en]

    The algorithm presented in this work has been developed to search for the optimal topology and design parameters of a set of Rankine cycles forming an energy system that absorbs/releases heat at different temperature levels and converts part of the absorbed heat into electricity. This algorithm can deal with several applications in the field of energy engineering: e.g., steam cycles or bottoming cycles in combined/cogenerative plants, steam networks, low temperature organic Rankine cycles. The main purpose of this algorithm is to overcome the limitations of the search space introduced by the traditional mixed-integer programming techniques, which assume that possible solutions are derived from a single superstructure embedding them all. The algorithm presented in this work is a hybrid evolutionary/traditional optimization algorithm organized in two levels. A complex original codification of the topology and the intensive design parameters of the system is managed by the upper level evolutionary algorithm according to the criteria set by the HEATSEP method, which are used for the first time to automatically synthesize a “basic” system configuration from a set of elementary thermodynamic cycles. The lower SQP (sequential quadratic programming) algorithm optimizes the objective function(s) with respect to cycle mass flow rates only, taking into account the heat transfer feasibility constraint within the undefined heat transfer section. A challenging example of application is also presented to show the capabilities of the algorithm

  • 25.
    Gobbato, Paolo
    et al.
    Department of Industrial Engineering, University of Padova.
    Masi, Massimo
    Department of Management and Engineering, University of Padova.
    Lazzaretto, Andrea
    Department of Industrial Engineering, University of Padova.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Division of Energy Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology.
    Acoustic analysis of a diffusion flame gas turbine combustor by means of non-reactive calculations2014In: Proceedings of the 27th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2014: ECOS 2014, Turku, Finland, 15 - 19 June 2014 / [ed] R. Zevenhoven, Åbo: Åbo Akademi University Press, 2014Conference paper (Refereed)
    Abstract [en]

    Combustion instabilities are unsteady phenomena that can affect premixed and diffusion flame combustors. They are spontaneously excited by a feedback loop between an oscillatory heat release and one or more natural acoustic modes of the combustor. When large instabilities occur, the associated oscillations of pressure and heat release may lead to premature failures due to vibrations and thermal loads at combustor walls. The prediction of natural acoustic modes is often used to identify the modes coupled to the unsteady heat release and to design damping systems. Thanks to the increase in computing capabilities, several modelling tools have been developed to obtain detailed information regarding the spatial shape of the acoustic modes. This paper presents the acoustic analysis of a non-premixed gas turbine combustor. The analysis is based on non-reactive computational fluid dynamics simulations performed on a coarse grid model to calculate the frequency and shape of natural modes. The simulations require very limited computational effort because simple numerical models are adopted and no combustion and heat transfer models need to be activated. The influence of temperature and gas composition on acoustic mode frequencies is considered through a simple post-processing correction. Thus, frequencies measured under limit cycle conditions can be directly compared to calculated values to identify which natural mode is excited by the unsteady heat release. The numerical results are validated against full-scale experimental measurements.

  • 26.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kudahettige-Nilsson, Rasika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Black liquor fractionation for biofuels production: A techno-economic assessment2014In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 166, p. 508-517Article in journal (Refereed)
    Abstract [en]

    The hemicelluloses fraction of black liquor is an underutilized resource in many chemical pulp mills. It is possible to extract and separate the lignin and hemicelluloses from the black liquor and use the hemicelluloses for biochemical conversion into biofuels and chemicals. Precipitation of the lignin from the black liquor would consequently decrease the thermal load on the recovery boiler, which is often referred to as a bottleneck for increased pulp production. The objective of this work is to techno-economically evaluate the production of sodium-free lignin as a solid fuel and butanol to be used as fossil gasoline replacement by fractionating black liquor. The hydrolysis and fermentation processes are modeled in Aspen Plus to analyze energy and material balances as well as to evaluate the plant economics. A mathematical model of an existing pulp and paper mill is used to analyze the effects on the energy performance of the mill subprocesses.

  • 27.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Integrating the processes of a Kraft pulp and paper mill and its supply chain2014In: 27th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems: ECOS 2014, Turku, Finland 15 -19 June 2014 / [ed] R. Zevenhoven, Åbo: Åbo Akademi University Press, 2014Conference paper (Refereed)
    Abstract [en]

    This paper investigates the possibility of combining different forest industries (a pulp and paper mill, its supply chain, and a wood-pellet plant) into an integrated industrial site in which they share a common heat and power utility. Advanced process integration and optimization techniques are used to study the site from both material and energy viewpoints. An existing pulp and paper mill is used as the site core plant and its pulp and paper production rates are kept fixed as they are in reality, while the other material flow links among the plants are based on the current industrial situation in Sweden. Different scenarios are evaluated in order to reflect the two main objectives that can be pursued (increased electricity production or biomass resource saving) and the two technologies that can be considered for the shared CHP system (boilers and product gas fired gas turbines). The corresponding non-integrated (standalone) configurations are compared to these scenarios to quantify the potential benefits of the integration. Investment opportunity is also calculated for the considered scenarios as an indicator of the economic convenience

  • 28.
    Hebenstreit, Babette
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Schnetzinger, R.
    Bioenergy 2020+ GmbH.
    Ohnmacht, R.
    Bioenergy 2020+ GmbH.
    Höftberger, E.
    Bioenergy 2020+ GmbH.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Haslinger, W.
    Bioenergy 2020+ GmbH.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Techno-economic study of a heat pump enhanced flue gas heat recovery for biomass boilers2014In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 71, p. 12-22Article in journal (Refereed)
    Abstract [en]

    An active condensation system for the heat recovery of biomass boilers is evaluated. The active condensation system utilizes the flue gas enthalpy exiting the boiler by combining a quench and a compression heat pump. The system is modelled by mass and energy balances. This study evaluates the operating costs, primary energy efficiency and greenhouse gas emissions on an Austrian data basis for four test cases. Two pellet boilers (10 kW and 100 kW) and two wood chip boilers (100 kW and 10 MW) are considered. The economic analysis shows a decrease in operating costs between 2% and 13%. Meanwhile the primary energy efficiency is increased by 3–21%. The greenhouse gas emissions in CO2 equivalents are calculated to 15.3–27.9 kg MWh−1 based on an Austrian electricity mix. The payback time is evaluated on a net present value (NPV) method, showing a payback time of 2–12 years for the 10 MW wood chip test case.

  • 29.
    Manente, Giovanni
    et al.
    University of Padova, Department of Industrial Engineering.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, Andrea
    University of Padova, Department of Industrial Engineering.
    Pasi, Marco
    ENEL Engineering and Innovation, via Andrea Pisano 120, 56126 Pisa.
    An organic Rankine cycle off-design model for the search of the optimal control strategy2013In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 58, p. 97-106Article in journal (Refereed)
    Abstract [en]

    Power generation from low enthalpy geothermal resources using Organic Rankine Cycle systems is markedly influenced by the temperature level of the heat source and heat sink. During plant operation the actual temperature of the geofluid may be different from the value assumed in the design phase. In addition, the seasonal and daily variations of the ambient temperature greatly affect the power output especially when a dry condensation system is used. This paper presents a detailed off-design model of an Organic Rankine Cycle that includes the performance curves of the main plant components. Two capacitive components in the model have the key function of damping the temporary disequilibrium of mass and energy inside the system. Isobutane and R134a are considered as working fluids, mainly operating in subcritical and supercritical cycles, respectively. The off-design model is used to find the optimal operating parameters that maximize the electricity production in response to changes of the ambient temperatures between 0 and 30 °C and geofluid temperatures between 130 and 180 °C. This optimal operation strategy can be conveniently applied both to already existing plants and to the choice of new design plant configurations.

  • 30.
    Hebenstreit, Babette
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Höftberger, Ernst
    Bioenergy 2020+ GmbH.
    Ohnmacht, Ralf
    VOIGT+WIPP Engineers GmbH.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Enhanced flue gas condensation technology: Analysis of a 10 MW demonstration plant2013Conference paper (Other academic)
    Abstract [en]

    A study on the application of an active condensation system to a typical Austrian heating plant fed with wood chips is presented. The heating plant consists of two biomass boilers (5MW+3MW). The flue gas of both boilers is mixed and directed to a condensing heat exchanger for heat recovery. The heat gained in the heat recovery system is used for preheating the reflux. A heat pump was integrated to enhance the heat recovery. In this paper the integration of the heat pump is discussed. All parts are modeled to calculate the potential energy gain which is obtained and to assess the usefulness of the application of a heat pump from a thermodynamic point of view. In addition, an economic analysis was carried out to evaluate the payback time for the heat pump using the typical Austrian heat and electricity prices. Finally first measurement results are discussed.

  • 31.
    Andersson, Jan-Olof
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Improving energy efficiency of sawmill industrial sites by integration with pellet and CHP plants2013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 111, p. 791-800Article in journal (Refereed)
    Abstract [en]

    An essential strategy to lower energy and resources consumption is the development of highly integrated industrial sites including different kind of plants complementing one another. Sawmills are huge biomass suppliers to other industries, such as pulp and paper mills, pellet plants and CHP plants, and part of the biomass is also used for the internal heat requirement. In this paper the integration of a sawmill with a pellet plant and a CHP plant is investigated using advanced process integration techniques, so that the thermal energy and the electricity produced in the CHP plant by burning part of the sawmill biomass output are used for the heat and power requirements of the other two industries. The results show that up to 18% of the biomass by-products from the sawmill can be saved, but from the economic point of view the ratio between prices of the thermal energy sold for district heating and the low quality biomass has to be lower than the present one to make the integrated design solution more attractive than separate plant operation.

  • 32.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Optimization of process integration in a Kraft pulp and paper mill: Evaporation train and CHP system2013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 107, p. 98-110Article in journal (Refereed)
    Abstract [en]

    A great interest has been arising about the production of fuels and advanced chemicals from renewable resources such as wooden biomass in the so-called biorefineries. Pulp and paper mills are often seen as the most obvious fundamental module of such industrial sites, because of the common feedstock and the chemical transformations that already occur in the process. In this paper the model of real Kraft pulp and paper mill is developed and optimized from energetic point of view using process integration techniques, in order to assess the potential for energy saving and to establish a starting point for future research on biorefinery sites. Improvements to the configurations of the multi-effect evaporator and of the steam cycle in the CHP system have been introduced, and three different levels of heat integration boundaries have been considered (multi-effect evaporator, mill sub-processes, and total site). Results indicate a significant potential for the decrease in thermal energy requirement and/or the increase in power production for the same pulp and paper production.

  • 33.
    Morandin, Matteo
    et al.
    Chalmers University of Technology, Department of Energy and Environment, Division of Heat and Power Technology.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, Andrea
    Department of Industrial Engineering, University of Padova.
    Superimposition of elementary thermodynamic cycles and separation of the heat transfer section in energy systems analysis2013In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 135, no 2, article id 21602Article in journal (Refereed)
    Abstract [en]

    In a wide variety of thermal energy systems, the high integration among components derives from the need to correctly exploit all the internal heat sources by a proper matching with the internal heat sinks. According to what has been suggested in previous works to address this problem in a general way, a "basic configuration" can be extracted from the system flowsheet including all components but the heat exchangers, in order to exploit the internal heat integration between hot and cold thermal streams through process integration techniques. It was also shown how the comprehension of the advanced thermodynamic cycles can be strongly facilitated by decomposing the system into elementary thermodynamic cycles which can be analyzed separately. The advantages of the combination of these approaches are summarized in this paper using the steam injected gas turbine (STIG) cycle and its evolution towards more complex system configurations as an example of application. The new concept of "baseline thermal efficiency" is introduced to combine the efficiencies of the

  • 34.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Techno-economic evaluation of butanol production via black liquor fractionation2013Conference paper (Refereed)
  • 35.
    Toffolo, Andrea
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, Andrea
    University of Padova.
    Manente, Giovanni
    University of Padova.
    Paci, Marco
    ENEL Engineering and Innovation, via Andrea Pisano 120, 56126 Pisa.
    An organic rankine cycle off-design model for the search of the optimal control strategy2012In: ECOS 2012: The 25th International Conference on Efficiency, Cost, Optimization and Simulation of Energy Conversion Systems and Processes (Perugia, June 26th-June 29th, 2012) / [ed] Umberto Desideri; Giampaolo Manfrida; Enrico Sciubba, Firenze: Firenze University Press, 2012, p. 28-41Conference paper (Refereed)
    Abstract [en]

    Power generation from low enthalpy geothermal resources using Organic Rankine Cycle systems is markedly influenced by the temperature level of the heat source and heat sink. During plant operation the actual temperature of the geofluid may be different from the value assumed in the design phase. In addition, the seasonal and daily variations of the ambient temperature greatly affect the power output especially when a dry condensation system is used. This paper presents a detailed off-design model of an Organic Rankine Cycle that includes the performance curves of the main plant components. Two capacitive components in the model have the key function of damping the temporary disequilibrium of mass and energy inside the system. Isobutane and R134a are considered as working fluids, mainly operating in subcritical and supercritical cycles, respectively. The off-design model is used to find the optimal operating parameters that maximize the electricity production in response to changes of the ambient temperatures between 0 and 30°C and geofluid temperatures between 130 and 180°C. This optimal operation strategy can be conveniently applied both to already existing plants and in the choice of new design plant configurations. --------------------------------------------------------------------------------

  • 36.
    Gobbato, Paolo
    et al.
    Department of Mechanical Engineering, University of Padova.
    Masi, Massimo
    Department of Management and Engineering, University of Padova.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Tanzinid, Giordano
    ENEL Engineering and Innovation.
    Calculation of the flow field and NOx emissions of a gas turbine combustor by a coarse computational fluid dynamics model2012In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 45, no 1, p. 445-455Article in journal (Refereed)
    Abstract [en]

    Gas turbine performance is strongly dependent on the flow field inside the combustor. In the primary zone, the recirculation of hot products stabilises the flame and completes the fuel oxidation. In the dilution zone, the mixing process allows to obtain the suitable temperature profile at turbine inlet. This paper presents an experimental and computational analysis of both the isothermal and the reactive flow field inside a gas turbine combustor designed to be fed with natural gas and hydrogen. The study aims at evaluating the capability of a coarse grid CFD model, already validated in previous reactive calculations, in predicting the flow field and NOx emissions. An experimental campaign was performed on an isothermal flow test rig to investigate the combustion air splitting and the penetration of both primary and dilution air jets. These experimental data are used to validate the isothermal computations. The impact of combustion on the calculated flow field and on air splitting is investigated as well. Finally, NOx emission trend estimated by a post-processing technique is presented. The numerical NOx concentrations at the combustor discharge are compared with experimental measurements acquired during operation with different fuel burnt (natural gas or hydrogen) and different amount of steam injected.

  • 37.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Morandin, Matteo
    Chalmers University of Technology, Department of Energy and Environment, Division of Heat and Power Technology.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Methodological aspects in synthesis of combined sugar and ethanol production plant2012In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 41, no 1, p. 165-174Article in journal (Refereed)
    Abstract [en]

    The synthesis problem, i.e. the definition of type, number and design parameters of system components and their interconnections, is one of the main research field of chemical and energy engineering. The present paper aims at clarifying some methodological aspects for the systematic synthesis of processes by suggesting an organized procedure which is applied here to a case study of a sugarcane mill. The procedure starts from the definition of a Basic Plant Configuration (BPC) that is built according to the original “concept” of the conversion process (e.g., “transform sugarcane into sugar” or “transform sugarcane into sugar and ethanol”). The BPC comprises the “basic components”, i.e. those required to perform the main material and energy conversions, and considers the hot and cold thermal flows only instead of the heat exchangers. A design optimization of this configuration is then to be performed, in which the extreme temperature of the thermal streams are considered among the set of the decision variables. The original BPC is then progressively changed into new BPCs by means of structural modifications including component staging and addition of new material connections or subprocesses. Modifications to the original BPC are mainly derived from the interpretation of the process Grand Composite Curve (GCC), a graphical tool provided by Pinch Analysis, which helps identify the potential for process internal heat recovery. Although the development of an automated algorithm is the final goal of the research activities, this article aims at showing that the proposed approach can be used to systematically explore the most significant process synthesis options. In the light of the suggested procedure we investigate here three different process concepts for the conversion of sugarcane. Starting from the original concept of sugar production, process structural developments towards the combined sugar and ethanol production are proposed and discussed.

  • 38.
    Toffolo, Andrea
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, Andrea
    University of Padova.
    Spakovsky, Michael R. von
    Virginia Polytechnic Institute and State University.
    On the nature of the heat transfer feasibility constraint in the optimal synthesis/design of complex energy systems2012In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 41, no 1, p. 236-243Article in journal (Refereed)
    Abstract [en]

    In this paper, the formulation of the constraint on heat transfer feasibility in the synthesis/design optimization of complex energy systems is discussed, with particular emphasis on the case in which the matching among the hot and cold thermal streams within the system is not defined a priori. The mathematical nature of the set of inequality constraints expressing the internal availability of thermal power at different temperature levels is examined and some examples are shown illustrating the way these constraints bound the feasible region of the search space and affect the hypersurface of the so-called optimum response surface, which results from considering a reduced number of degrees of freedom of the optimization problem. A brief discussion is also proposed about the choice of the algorithm and the variables for the optimization process.

  • 39.
    Rech, Sergio
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    TSO-STO: A two-step approach to the optimal operation of heat storage systems with variable temperature tanks2012In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 45, no 1, p. 366-374Article in journal (Refereed)
    Abstract [en]

    Mixed-Integer Linear Programming (MILP) has been generally used in the recent past to evaluate the optimal operation of heat storage systems for district heating. In fact, model equations and constraints can be linearized to strongly reduce the computational time without a significant loss in accuracy, and other simplifying hypotheses can be introduced, such as the constant value of the heat storage temperature.This paper presents instead a non-linear model of a Combined Heat and Power (CHP) system with a variable temperature heat storage serving a district heating network. Optimal operation for a fixed time-dependent demand is searched by varying CHP system loads. The objective is the maximization of management profit in a deregulated electricity market, taking into account investment (CHP and heat storage systems) and operating costs. The nature of the problem is investigated and a new approach for the decomposition of the objective function is proposed to simplify the solution procedure. The impact of different fuel costs and average electricity prices on the results is also analyzed.

  • 40.
    Masi, Massimo
    et al.
    Department of Mechanical Engineering, University of Padova.
    Gobbato, Paolo
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Cocchi, Stefano
    GE Oil & Gas—Nuovo Pignone SpA.
    Numerical and experimental analysis of the temperature distribution in a hydrogen fuelled combustor for a 10 MW gas turbine2011In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 133, no 2Article in journal (Refereed)
    Abstract [en]

    Proper cooling of the hot components and an optimal temperature distribution at the turbine inlet are fundamental targets for gas turbine combustors. In particular, the temperature distribution at the combustor discharge is a critical issue for the durability of the turbine blades and the high performance of the engine. At present, CFD is a widely used tool to simulate the reacting flow inside gas turbine combustors. This paper presents a numerical analysis of a single can type combustor designed to be fed both with hydrogen and natural gas. The combustor also features a steam injection system to restrain the NOx pollutants. The simulations were carried out to quantify the effect of fuel type and steam injection on the temperature field. The CFD model employs a computationally low cost approach, thus the physical domain is meshed with a coarse grid. A full-scale test campaign was performed on the combustor: temperatures at the liner wall and the combustor outlet were acquired at different operating conditions. These experimental data, which are discussed, were used to evaluate the capability of the present CFD model to predict temperature values for combustor operation with different fuels and steam to fuel ratios

  • 41.
    Gobbato, Paolo
    et al.
    Department of Mechanical Engineering, University of Padova.
    Masi, Massimo
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Numerical simulation of a hydrogen fuelled gas turbine combustor2011In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, no 13, p. 7993-8002Article in journal (Refereed)
    Abstract [en]

    The interest for hydrogen-fuelled combustors is recently growing thanks to the development of gas turbines fed by high content hydrogen syngas. The diffusion flame combustion is a well-known and consolidated technology in the field of industrial gas turbine applications. However, few CFD analyses on commercial medium size heavy duty gas turbine fuelled with pure hydrogen are available in the literature. This paper presents a CFD simulation of the air-hydrogen reacting flow inside a diffusion flame combustor of a single shaft gas turbine. The 3D geometrical model extends from the compressor discharge to the gas turbine inlet (both liner and air plenum are included). A coarse grid and a very simplified reaction scheme are adopted to evaluate the capability of a rather basic model to predict the temperature field inside the combustor. The interest is focused on the liner wall temperatures and the turbine inlet temperature profile since they could affect the reliability of components designed for natural gas operation. Data of a full-scale experimental test are employed to validate the numerical results. The calculated thermal field is useful to explain the non-uniform distribution of the temperature measured at the turbine inlet

  • 42.
    Morandin, Matteo
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Meréchal, Francois
    LENI Industrial Energy Systems Laboratory.
    Ensinas, Adriano V.
    CECS, Federal University of ABC (UFABC).
    Nebra, Silvia A
    NIPE Interdisciplinary Centre for Energy Planning, University of Campinas.
    Synthesis and parameter optimization of a combined sugar and ethanol production process integrated with a CHP system2011In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 36, no 6, p. 3675-3690Article in journal (Refereed)
    Abstract [en]

    The combined sugar and ethanol production process from sugar cane is a paradigmatic application for energy integration strategies because of the high number of hot and cold streams involved, the external hot utility requirement at two temperature levels for juice evaporation and crystallization, and the electricity demand for juice extraction by milling. These conditions make it convenient to combine the sugar-cane process with a CHP system fuelled by bagasse, the main by-product from juice extraction. The strategies, tools and expertise on energy integration developed separately by the research teams authoring this paper are applied here jointly to optimize the synthesis and the design parameters of the process and of the total site starting from the basic idea of dissociating the heat exchanger network design problem from the total site synthesis problem. At first the minimization of the external heat requirement for the process alone is pursued and results show that a one third reduction can be achieved by optimal heat integration. Then the use of the by-product bagasse for on-site power generation is considered and two bagasse-fuelled CHP systems are optimized along with some parts of the sugar and ethanol production process in order to obtain maximum total site net power. Results show a variety of interesting scenarios of combined sugar, ethanol and electricity production plants with considerably high electricity output.

  • 43.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Morandin, Matteo
    Department of Mechanical Engineering, University of Padova.
    Spakovsky, Michael R. von
    Center for Energy Systems Research, Department of Mechanical Engineering, Virginia Polytechnic Institute, Blacksburg.
    Criteria for the decomposition of energy systems in local/global optimizations2010In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 35, no 2, p. 1157-1163Article in journal (Refereed)
    Abstract [en]

    The decomposition of an energy system into subsystems of reduced complexity, to be optimized separately, but in a way compatible with the optimum of the global system, has been recognized as a viable solution to the problem of the design optimization of highly integrated, complex energy systems. Iterative Local/Global Optimization (ILGO) and its dynamic extension (DILGO) permit the decomposition of the global problem into smaller subproblems to be optimized separately, guaranteeing in the process that the subproblem optima eventually converge after a small number of iterations to or near to the optimum of the original global problem. The aim of this paper is to analyze the criteria for energy system decomposition, in particular with regard to the formulation of the separate subproblems and to the imposition of the constraints that affect the coupling of two or more subsystems. Three general decomposition criteria are identified and discussed with simple examples to let the mathematical formulation be analyzed critically

  • 44.
    Masi, Massimo
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Antonello, Marco
    Department of Mechanical Engineering, University of Padova.
    Experimental analysis of a motorbike high speed racing engine2010In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 87, no 5, p. 1641-1650Article in journal (Refereed)
    Abstract [en]

    Power gain is the main objective in any motorbike competition. Despite of the wide literature on theoretical and experimental methods for increasing engine power, there is a general lack of data about tests on racing engine performance due to the obvious manufacturers' reluctance to spread information, especially for recent high technological level applications. This paper, instead, presents all the main results of the experimental tests conducted on a motorbike engine both in the original stock arrangement and in a modified configuration proposed in compliance with the Technical Regulations of the 2007 FIM Road Racing Supersport Italian Championship (CIV). Traditional testing techniques (steady-flow discharge coefficients measurements and chassis dynamometer tests performed in the slow speed ramp mode) are chosen to reduce time and costs and to limit engine wearing while obtaining an acceptable degree of accuracy. It is also proved that the tests to assess the improvements obtained with design changes could not have been completed in the steady-state mode using a single engine because of the short life cycle of racing engines due to wearing, which would have altered the comparisons. Test results show a 16% and 33% rise in torque and power for the racing configuration, reaching the state of the art of the best performing engines in the Italian Supersport racing class

  • 45. Toffolo, Andrea
    et al.
    Masi, Massinmo
    Department of Mechanical Engineering, University of Padova.
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Low computational cost CFD analysis of thermoacoustic oscillations2010In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, no 6-7, p. 544-552Article in journal (Refereed)
    Abstract [en]

    The numerical analysis of thermoacoustic oscillation phenomena by means of time-dependent CFD simulations usually requires a great computational effort, which may not be reasonable in industrial design. On the other hand, CFD tools provide the only approach that includes all the physical and chemical aspects involved in the thermoacoustic coupling between flame heat release and the acoustic modes of the burner/combustion chamber system. This paper presents some guidelines to reduce the computational effort required to perform a CFD analysis of the thermoacoustic oscillations with commercial codes. These guidelines are organized in a procedure that can be followed to analyze thermoacoustic coupling conditions that actually lead to unstable oscillations or are identified as potentially critical in the design phase. This procedure is also illustrated by an example of application, the partially-premixed flame type burner of a real 10 MW industrial boiler which shows noisy pressure fluctuations at a low frequency

  • 46.
    Masi, Massimo
    et al.
    Department of Mechanical Engineering, University of Padova.
    Gobbato, Paolo
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Cocchi, Stefano
    GE Oil & Gas—Nuovo Pignone SpA.
    Numerical and Experimental Analysis of the Temperature Distribution in a Hydrogen Fuelled Combustor for a 10 MW Gas Turbine2010In: Proceedings of the ASME Turbo Expo 2010: presented at the 2010 ASME Turbo Expo, June 14 - 18, 2010, Glasgow, UK, New York: American Society of Mechanical Engineers , 2010, Vol. 2 : Combustion, fuels and emissions, p. 1005-1014Conference paper (Refereed)
    Abstract [en]

    Proper cooling of the hot components and an optimal temperature distribution at the turbine inlet are fundamental targets for gas turbine combustors. In particular, the temperature distribution at the combustor discharge is a critical issue for the durability of the turbine blades and the high performance of the engine. At present, CFD is a widely used tool to simulate the reacting flow inside gas turbine combustors. This paper presents a numerical analysis of a single can type combustor designed to be fed both with hydrogen and natural gas. The combustor also features a steam injection system to restrain the NOx pollutants. The simulations were carried out to quantify the effect of fuel type and steam injection on the temperature field. The CFD model employs a computationally low cost approach, thus the physical domain is meshed with a coarse grid. A full-scale test campaign was performed on the combustor: temperatures at the liner wall and the combustor outlet were acquired at different operating conditions. These experimental data, which are discussed, were used to evaluate the capability of the present CFD model to predict temperature values for combustor operation with different fuels and steam-fuel ratios

  • 47. Toffolo, Andrea
    et al.
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Morandin, Matteo
    Department of Mechanical Engineering, University of Padova.
    The HEATSEP method for the synthesis of thermal systems: An application to the S-Graz cycle2010In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 35, no 2, p. 976-981Article in journal (Refereed)
    Abstract [en]

    In the last decades component synthesis has become a critical issue in the research field about new highly integrated energy conversion systems. Several heuristic methodologies following experience-based guidelines have been proposed to simplify the problem of synthesis optimization. This paper describes an application of the HEATSEP method, which consists in the isolation of all the heat transfer processes of an energy system in an undefined "black-box". Then, synthesis optimization can be split in two subproblems, the first about the synthesis/design optimization of the basic plant configuration (which is made up of all the components but heat transfer devices) and the other about the synthesis of the heat exchanger network inside the black-box. The chosen test case is the design optimization of the basic plant configuration of an S-Graz cycle based power plant, as it is suitable to show the potentialities of the method

  • 48. Toffolo, Andrea
    et al.
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    A global and a local approach with evolutionary algorithms to locate malfunction causes in energy systems2009In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 131, no 4, p. 0420011-0420017Article in journal (Refereed)
    Abstract [en]

    Energy system performance may differ from the expected one during actual operation because of the effects of faults, anomalies, and wear and tear due to normal use. One of the main issues of diagnosis, i.e., the procedure to discover the causes of malfunctions, is to find the way back from measured altered performance to the original cause. Several procedures were proposed in the literature to solve the diagnostic problem, usually based on the comparison between a reference nonmalfunctioning condition and an actual, possibly malfunctioning, condition. A different strategy is suggested in the paper. A direct search of the possible causes of malfunctions is performed by means of an evolutionary algorithm: a component fault is arbitrarily introduced in a model of the healthy system by substituting the reference characteristic curve with an altered one, and the algorithm is used to search for a combination of different kinds of performance modifiers that generates the same measured effects of the actual anomaly. A global and a local approach are proposed and applied to a real test case plant, also in presence of measurement noise. The local approach demonstrates to be more effective in terms of accuracy and computational effort.

  • 49. Toffolo, Andrea
    Fuzzy expert systems for the diagnosis of component and sensor faults in complex energy systems2009In: Proceedings of the ASME International Mechanical Engineering Congress and Exposition - 2008: presented at 2008 ASME International Mechanical Engineering Congress and Exposition, October 31 - November 6, 2008, Boston, Massachusetts, USA, New York: American Society of Mechanical Engineers , 2009, Vol. 6: Electronics and photonics, p. 237-247Conference paper (Refereed)
    Abstract [en]

    Locating the causes of malfunctions in complex energy systems is an extremely difficult task, since more than one fault mode may produce similar and possibly undistinguishable patterns of effects. This paper shows how fuzzy expert systems can exploit the available measurements from the data acquisition system to identify different component and sensor fault modes. Real sensor data (mass flow rates, pressures, temperatures, and key operating parameters) are compared to the expected values of the same quantities that are calculated using numerical models of local subsystems. This comparison simply determines if the differences between measured and expected values are "negative", "zero" or "positive" in fuzzy logic terms. The final objective is to verify the existence of some patterns of these attributes that univocally identify the considered fault modes. These patterns are then implemented as the set of rules forming the knowledge base of a fuzzy expert system. The proposed diagnostic methodology is tested on the gas section of a real combined-cycle cogeneration plant and the effect of measurement noise is also discussed.

  • 50. Toffolo, Andrea
    Fuzzy expert systems for the diagnosis of component and sensor faults in complex energy systems2009In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 131, no 4, p. 0420021-04200210Article in journal (Refereed)
    Abstract [en]

    Locating the causes of malfunctions in complex energy systems is an extremely difficult task, since more than one fault mode may produce similar and possibly undistinguishable patterns of effects. This paper shows how fuzzy expert systems can exploit the available measurements from the data acquisition system to identify different component and sensor fault modes. Real sensor data (mass flow rates, pressures, temperatures, and key operating parameters) are compared with the expected values of the same quantities that are calculated using numerical models of local subsystems. This comparison simply determines if the differences between measured and expected values are "negative," "zero," or "positive" in fuzzy logic terms. The final objective is to verify the existence of some patterns of these attributes that univocally identify the considered fault modes. These patterns are then implemented as the set of rules forming the knowledge base of a fuzzy expert system. The proposed diagnostic methodology is tested on the gas section of a real combined-cycle cogeneration plant, and the effect of measurement noise is also discussed

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