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  • 1.
    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.

  • 2.
    Benini, Ernesto
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    A parametric method for optimal design of two-dimensional cascades2001In: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy, ISSN 0957-6509, E-ISSN 2041-2967, Vol. 215, no 4, p. 465-473Article in journal (Refereed)
    Abstract [en]

    A parametric method for optimal design of two-dimensional cascades, based on the coupling between a genetic algorithm and a commercial computational fluid dynamics code, is introduced. The results of cascade geometry optimization for a large range of inlet and outlet flow angle pairs are presented. The method is a simple as well as effective tool for the optimal design of cascades for axial flow pumps.

  • 3.
    Benini, Ernesto
    et al.
    Dipartimento di Ingegneria Meccano, Università di Padova.
    Toffolo, Andrea
    Axial-flow compressor model based on a cascade stacking technique and neural networks2002In: Proceedings of the ASME Turbo Expo 2002 Turbomachinery: presented at the 2002 ASME Turbo Expo, June 3 - 6, 2002, Amsterdam, the Netherlands, New York: American Society of Mechanical Engineers , 2002, Vol. 5B, p. 793-801Conference paper (Refereed)
    Abstract [en]

    This paper introduces a cascade-stacking technique for the development of a gas turbine multi-stage axial-flow compressor model. A large database of stationary and rotating cascade performance is first obtained by quasi three-dimensional CFD simulations and used to train neural networks for the prediction of cascade performance under generalized conditions. Then the model directly calculates the operating point of a compressor having known geometry characteristics, including variable inlet guide/stator vane effects, as a function of mass flow rate and rotational speed. The model can also be used as a valuable preliminary design tool, obtaining geometry characteristics by imposing flow patterns.

  • 4.
    Benini, Ernesto
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Centrifugal compressor of a 100 kW microturbine: Part 3 - Optimization of diffuser apparatus2003In: Proceedings of the ASME Turbo Expo 2003: presented at the 2003 ASME Turbo Expo, June 16 - 19, 2003, Atlanta, Georgia, New York: American Society of Mechanical Engineers , 2003, Vol. 3 : Cycle innovations. Marine. Manufacturing materials and metallurgy. Microturbines and small turbomachinery, p. 707-714Conference paper (Refereed)
    Abstract [en]

    This is the last part of a three-part paper regarding performance analysis and optimization of a centrifugal compressor used in a 100 kW microturbine. This part deals with the numerical constrained optimization of the diffuser apparatus (i.e. the radial and deswirl cascades) for maximum aerodynamic efficiency and pressure recovery. The optimization is accomplished through the application of a multiobjective Pareto evolutionary algorithm which is interfaced to a parametric code, that generates the geometries to be analyzed, and a Computational Fluid Dynamics code that measures the fitness of the candidate solutions. The variables of the optimization include the main dimensions of diffuser (with a constraint on the overall radial and axial size) and the profiles' shape. The set of optimized configurations is illustrated and compared to the original one; the reason of improved performance are finally discussed.

  • 5.
    Benini, Ernesto
    et al.
    University of Padova.
    Toffolo, Andrea
    Development of high-performance airfoils for axial flow compressors using evolutionary computation2002In: Journal of Propulsion and Power, ISSN 0748-4658, E-ISSN 1533-3876, Vol. 18, no 3, p. 544-554Article in journal (Refereed)
    Abstract [en]

    An original multiobjective optimization method is used to support the generation of a new family of profiles for two-dimensional cascades suitable for subsonic compressors. The aim of the optimization is to maximize the pressure ratio and to minimize the profile losses of a cascade, while conforming to a functional constraint on the operating range. The method uses an evolutionary algorithm featuring a novel evaluation technique conceived for multiobjective problems and a blade-to-blade inviscid/viscous solver for calculating flow quantities. As an example, an excerpt of optimized profiles is presented, and their performances are compared with those of conventional NACA 65 profiles. The new profiles show superior design performances both in efficiency and pressure rise, as well as a tolerance to incidence angles comparable to conventional profiles. The reasons of this improvement are discussed in detail on the basis of rigorous loss analysis.

  • 6.
    Benini, Ernesto
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Innovative procedure to minimize multi-row compressor blade dynamic loading using rotor-stator interaction optimization2007In: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy, ISSN 0957-6509, E-ISSN 2041-2967, Vol. 221, no 1, p. 59-66Article in journal (Refereed)
    Abstract [en]

    This paper presents a two-dimensional two-objective procedure for minimizing dynamic loading and maximizing efficiency in multi-stage compressors. The procedure arises from the combination of an evolutionary algorithm and a CFD code, in which a sliding mesh technique and a time-dependent approach are implemented, enabling the study of unsteady rotor-stator interaction. The method is then applied to a two-stage compressor cascade (rotor-stator-rotor-stator). The results concerning the optimal set of geometrical parameters considered for optimization (axial distances between successive cascades, circumferential clocking between stators and between rotors) are finally presented and discussed

  • 7.
    Benini, Ernesto
    et al.
    Dipartimento di Ingegneria Meccano, Università di Padova.
    Toffolo, Andrea
    Optimal design of horizontal-axis wind turbines using blade-element theory and evolutionary computation2002In: Journal of solar energy engineering, ISSN 0199-6231, E-ISSN 1528-8986, Vol. 124, no 4, p. 357-363Article in journal (Refereed)
    Abstract [en]

    This paper describes a multi-objective optimization method for the design of stall-regulated horizontal-axis wind turbines. Two modules are used for this purpose: an aerodynamic model implementing the blade-element theory and a multi-objective evolutionary algorithm. The former provides a sufficiently accurate solution of the flow field around the rotor disc; the latter handles the decision variables of the optimization problem, i.e., the main geometrical parameters of the rotor configuration, and promotes function optimization. The scope of the method is to achieve the best trade-off performance betoveen two objectives: annual energy production per square meter of wind park (to be maximized) and cost of energy (to be minimized). Examples of the best solutions found by the method are described and their performance compared with those of commercial wind turbines

  • 8.
    Benini, Ernesto
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Centrifugal compressor of a 100 kW microturbine: Part 1 - Experimental and numerical investigations on overall performance2003In: Proceedings of the ASME Turbo Expo 2003: presented at the 2003 ASME Turbo Expo, June 16 - 19, 2003, Atlanta, Georgia, New York: American Society of Mechanical Engineers , 2003, Vol. 3 : Cycle innovations. Marine. Manufacturing materials and metallurgy. Microturbines and small turbomachinery, p. 691-698Conference paper (Refereed)
    Abstract [en]

    This paper describes on/off design performance of a centrifugal compressor of a 100 kW turbogenerator gas turbine engine used for small scale power generation. The compressor stage is made up of a radial impeller and a two-stage diffuser (radial and deswirl). Pan 1 deals with the experimental and numerical tests on overall compressor and diffuser performance: An extensive test series with steady probe measurements at impeller exit and diffuser exit is performed at different operating points and rotational speeds. This makes it possible to characterize both overall compressor and diffuser. The numerical model is based on a mixing plane at impeller-diffuser interface and therefore neglects the effect of unsteadiness due to rotor-stator interaction. Then, in part 2 the true time-dependent interaction is investigated by means of a numerical model where a sliding mesh technique is adopted. The unsteady results are then processed and compared with the steady ones regarding the flow in the diffuser. Finally, in part 3 the geometry of the compressor diffuser is optimized using an evolutionary algorithm coupled with a CFD code in order to improve compressor performance.

  • 9.
    Benini, Ernesto
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Experimental and numerical analyses to enhance the performance of a microturbine diffuser2006In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 30, no 5, p. 427-440Article in journal (Refereed)
    Abstract [en]

    This paper describes design and off-design behavior of a centrifugal compressor of a 100 kW gas turbine used for small scale power generation and establishes the guidelines to improve diffuser performance. The first part of the paper deals with the experimental and numerical tests on the overall machine: An extensive series of tests at different operating points and rotational speeds is performed using steady probe measurements at impeller exit and diffuser exit; the numerical model features a mixing plane at impeller-diffuser interface and therefore neglects the effect of unsteadiness due to rotor-stator interaction. In the second part of the paper, the true time-dependent rotor-stator interaction is investigated by means of a numerical model where a sliding mesh technique is adopted instead. The unsteady results are then processed and compared with the computed steady flow in the diffuser. Finally, the geometry of the compressor diffuser is optimized using an evolutionary algorithm coupled with a CFD code.

  • 10.
    Bernini, Ernesto
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Centrifugal compressor of a 100 kW microturbine: Part 2 - Numerical study of impeller-diffuser interaction2003In: Proceedings of the ASME Turbo Expo 2003: presented at the 2003 ASME Turbo Expo, June 16 - 19, 2003, Atlanta, Georgia, New York: American Society of Mechanical Engineers , 2003, Vol. 3 : Cycle innovations. Marine. Manufacturing materials and metallurgy. Microturbines and small turbomachinery, p. 699-705Conference paper (Refereed)
    Abstract [en]

    The interaction between impeller and diffuser blades in high-speed centrifugal compressors is thought to have a significant influence on the flow within the diffuser. In this part, Computational Fluid Dynamics is exploited to simulate, visualize and analyze the complex flow generated by the interaction, with particular emphasis on the unsteady behavior of the vaned diffuser of the microturbine compressor studied in part 1. For this purpose, the 3D geometry of the compressor stage is studied by performing a fully unsteady simulation of rotor-stator interaction. The results of the unsteady calculation regarding the diffuser performance are then averaged in time and compared with those obtained with a fully steady and decoupled computation in order to highlight the main difference between the two approaches.

  • 11.
    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.

  • 12.
    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.

  • 13.
    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.

  • 14.
    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

  • 15.
    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

  • 16.
    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.

  • 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.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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.

  • 22.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    A critical review of the thermoeconomic diagnosis methodologies for the location of causes of malfunctions in energy Systems2006In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 128, no 4, p. 335-341Article in journal (Refereed)
    Abstract [en]

    Thermoeconomic diagnosis procedures in the literature rely on the assumption that specific consumptions of resources in the components are the key to interpret the effects of malfunctions and then to trace a path towards the sources of anomalies. The main obstacle to a successful application of these approaches is represented by the actual interactions existing among components which cause a propagation of the alteration of component specific consumptions and therefore mask those effects that would allow a direct identification of the origin of malfunction. This paper presents an extensive discussion of potentialities and limits of diagnosis procedures proposed in the literature in distinguishing the effects induced by component interactions from those that are intrinsically generated by the anomaly, which is considered here as the main task to locate effectively causes of malfunctions in energy systems

  • 23.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    A critical review of the thermoeconomic diagnosis methodologies for the location of causes of malfunctions in energy systems2003In: Proceedings of the ASME Advanced Energy Systems Division - 2003: presented at the 2003 ASME International Mechanical Engineering Congress, November 15 - 21, 2003, Washington, D.C / [ed] Robert Boehm, New York: American Society of Mechanical Engineers , 2003, p. 345-354Conference paper (Refereed)
    Abstract [en]

    Thermoeconomic diagnosis procedures in the literature rely on the assumption that specific consumption of resources in the components are the key to interpret the effects of malfunctions and then to trace a path towards the sources of anomalies. The main obstacle to a successful application of these approaches is represented by the actual interactions existing among components which cause a propagation of the alteration of component specific consumptions and therefore mask those effects that would allow a direct identification of the origin of malfunction. This paper presents an extensive discussion of potentialities and limits of diagnosis procedures proposed in the literature in distinguishing the effects induced by component interactions from those that are intrinsically generated by the anomaly, which is considered here as the main task to locate effectively causes of malfunctions in energy systems.

  • 24.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    A method to separate the problem of heat transfer interactions in the synthesis of thermal systems2008In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 33, no 2, p. 163-170Article in journal (Refereed)
    Abstract [en]

    Most of the efforts to improve energy system configurations are directed towards the recovery of internal heat, which reduces the contribution of the external hot source and enhance system efficiency accordingly. This problem is strictly related to the synthesis of different components into system topology, i.e. with the definition of the optimal system configuration according to specified objectives. A new method for the optimization of the heat transfer interactions within energy systems is presented here, based on the idea of cutting thermal links between the "basic" components of the system. The boundary temperatures of hot and cold flows that are generated as a consequence of these cuts are evaluated in an optimization procedure that involves the design parameters of the system as well. The high potential of the proposed method consists in separating the problem of defining the system configuration into two separate sub-problems, the first regarding the definition of the "basic" topology of the system (related to all components different from the heat exchangers), the second the optimal heat transfer interactions within the system. This feature makes complex systems today only marginally "optimizable", amenable to complete optimization. The method is applied to a humid air turbine (HAT) cycle plant, which represents a good test to prove its reliability and generality, due to the internal recirculation of mass and energy flows

  • 25.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Analytical and neural network models for gas turbine design and off-design simulation2001In: International Journal of Thermodynamics, ISSN 1301-9724, Vol. 4, no 4, p. 173-182Article in journal (Refereed)
    Abstract [en]

    This paper presents a gas turbine design and off-design model in which the difficulties due to lack of knowledge about stage-by-stage performance are overcome by constructing artificial machine maps through appropriate scaling techniques applied to generalized maps taken from the literature and validating them with test measurement data from real plants. In particular, off-design performance is obtained through compressor map modifications according to variable inlet guide vane closure. The set of equations of the developed analytical model is solved by a commercial package, which provides great flexibility in the choice of independent variables of the overall system. The results obtained from this simulator are used for neural network training: problems associated with the construction and use of neural networks are discussed and their capability as a tool for predicting machine performance is analyzed.

  • 26.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Energy, economy and environment as objectives in multi-criterion optimization of thermal systems design2004In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 29, no 8, p. 1139-1157Article in journal (Refereed)
    Abstract [en]

    The paper shows how a thermal system design can be optimized using energy, economy and environment as separate objectives. Comparisons with a single-objective thermo-economic optimization and a two-objective energetic and economic optimization are also discussed. The test case plant of the CGAM problem is taken as an example of application for the three-objective approach. An environmental impact objective function is defined and expressed in cost terms by weighting carbon dioxide and nitrogen oxide emissions according to their unit damage costs. An evolutionary algorithm is used to find the surface of optimal solutions in the space defined by the three objective functions

  • 27.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Prediction of performance and emissions of a two-shaft gas turbine from experimental data2008In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 28, no 17-18, p. 2405-2415Article in journal (Refereed)
    Abstract [en]

    Precise performance evaluation at design and off-design operations is needed for a correct management of power plants. This need is particularly strong in gas turbine power plants, which can quickly react to load variations and are very sensitive to ambient conditions. The paper aims at presenting a simple tool to determine the values of the thermodynamic quantities in each point of the plant and the overall plant performances of a real gas turbine plant. Starting from experimental data, a zero-dimensional model is developed, which properly considers the effect of ambient conditions and water injection for pollutant abatement at different load settings under the action of the control system. In particular, semi-empirical correlations for pollutant emissions taken from the literature are adapted by tuning their coefficients on the experimental data, in order to predict carbon monoxide and nitrogen oxide pollution. Such a tool can be useful to manage the energetic, economic and environmental aspects of plant operation.

  • 28.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Martegani, A.D.
    Department of Mechanical Engineering, University of Padova.
    A systematic experimental approach to cross-flow fan design2003In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 125, no 4, p. 684-693Article in journal (Refereed)
    Abstract [en]

    A systematic investigation of cross-flow fan performances is presented according to an original criterion for the parameterization of fan geometry. Test facility and procedures are set up following ISO standards. The aim is to find which are the parameters most affecting fan performances and the effects of their design choice. Indications are found to design fans according to the desired objectives, such as maximum total pressure, total efficiency, and flow rate.

  • 29.
    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

  • 30.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, Università di Padova.
    Toffolo, Andrea
    Passuello, Riccardo
    Department of Mechanical Engineering, Università di Padova.
    Jüdes, Marc
    Institute for Energy Engineering, Technische Universität Berlin.
    Cziesla, Frank
    Institute for Energy Engineering, Technische Universität Berlin.
    Tsatsaronis, George
    Institute for Energy Engineering, Technische Universität Berlin.
    The characteristic curve method in energy systems diagnosis: Analysis of uncertainties in a real plant2005In: Proceedings of the ASME Advanced Energy Systems Division - 2005: presented at 2005 ASME International Mechanical Engineering Congress and Exposition, November 5 - 11, 2005, Orlando, Florida, USA, New York: American Society of Mechanical Engineers , 2005, Vol. 46, p. 379-390Conference paper (Refereed)
    Abstract [en]

    Thermoeconomic diagnostic approaches have proved to be effective in quantifying additional exergy consumption and costs, whereas they demonstrated to be less appropriate in the search of malfunction causes. With the intent of overcoming this limitation the Characteristic Curve Method was suggested by Toffolo and Lazzaretto, which is based on the idea that every malfunction leaves an undeletable trace in the system: the modification of the component characteristic curve. An exergetic index was found to be very suitable to highlight this trace, and demonstrated consequently to be very effective in identifying the causes of malfunctions. In this paper the method is applied to an existing cogeneration plant, that is simulated using a commercially available code. Simulation errors due to the iterative criterion used by the simulator to find convergence are considered in the analysis, and the reliability of the method under these conditions checked. The example of application is used to show all the calculation steps to be performed, and the way of reading the results in order to properly detect causes of malfunctions. This helps avoid misleading conclusions and demonstrates the practical and easy application of the method when commercial simulator codes are used.

  • 31.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Reini, M.
    Department of Energetics, University of Trieste.
    Taccani, R.
    Department of Energetics, University of Trieste.
    Zaleta-Aguilar, A.
    Department of Mechanical Engineering, University of Guanajuato.
    Rangel-Hernández, V.
    CIRCE-Department of Mechanical Engineering, University of Zaragoza.
    Verda, V.
    Department of Energy Engineering, Politecnico di Torino.
    Four approaches compared on the TADEUS (thermoeconomic approach to the diagnosis of energy utility systems) test case2006In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 31, no 10-11, p. 1586-1613Article in journal (Refereed)
    Abstract [en]

    Four approaches to the diagnosis of malfunctions in energy systems are presented and applied to the same test case plant. The paper is part of a project, started in 2001 and named thermoeconomic approach to the diagnosis of energy utility systems (TADEUS), aimed at integrating various experiences accumulated by a group of researchers operating in the thermoeconomic diagnostics, a field of research started by Antonio Valero and co-workers in 1990 and then followed by various people all over the world. It is shown how, starting from the same basic set of ideas, researchers developed different approaches, each one having peculiar characteristics that are, however, complementary to each other

  • 32.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Trolese, Sebastiano
    Department of Mechanical Engineering, University of Padova.
    Using experimental data for predicting performance and emissions of a real gas turbine plant2002In: Proceedings of the ASME Advanced Energy Systems Division - 2002: presented at the 2002 ASME International Mechanical Engineering Congress and Exposition, November 17 - 22, 2002, New Orleans, Louisiana / [ed] Srinivas Garimella, New York: American Society of Mechanical Engineers , 2002, p. 309-317Conference paper (Refereed)
    Abstract [en]

    Precise performance evaluation at design and off-design operations is needed for a correct management of power plants. This need is particularly strong in gas turbine power plants which can quickly react to load variations and are very sensitive to ambient conditions. The paper aims at presenting a simple tool to determine the values of the thermodynamic quantities in each point of the plant and the overall plant performances of a real gas turbine plant. Starting from experimental data, a zero-dimensional model is developed which properly considers the effect of ambient conditions and water injection for pollutant abatement at different load settings under the action of the control system. An emission model taken from the literature is also included, after tuning on experimental data, to predict carbon monoxide and nitrogen oxide pollution

  • 33.
    Lazzaretto, Andrea
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Zanon, Frederico
    Department of Mechanical Engineering, University of Padova.
    Parameter sttetting for a tubular SOFC simulation model2004In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 126, no 1, p. 40-46Article in journal (Refereed)
    Abstract [en]

    Several empirical assumptions deriving from observations and measurements of the physical processes are involved in the modeling of Solid Oxide Fuel Cells (SOFCs). An insight of the main models proposed in the literature is given to present the characteristics and limits of these assumptions for the various existing configurations. The basic structure and equations of the models are discussed in details, focusing particularly on the parameters that are to be set to achieve reliability and accuracy. According to this discussion, a zero-dimensional model for a tubular Solid Oxide Fuel Cell (SOFC) is then presented. The model demonstrates good capability in predicting SOFC characteristic curves as they appear in the literature.

  • 34.
    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.

  • 35.
    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

  • 36.
    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

  • 37.
    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

  • 38.
    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.

  • 39.
    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.

  • 40.
    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.

  • 41.
    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)
  • 42.
    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.

  • 43.
    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

  • 44.
    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

  • 45.
    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

  • 46.
    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.

  • 47.
    Mondarin, Marco
    et al.
    Department of Mechanical Engineering, University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    On the benefits of separating the heat transfer section and analyzing elementary thermodynamic cycles in energy systems analysis2009In: 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. 8 : Energy systems: analysis, thermodynamics and sustainability, sustainable products and processes, p. 283-294Conference paper (Refereed)
    Abstract [en]

    The search for increasing performance and efficiency in energy system analysis leads to complex and highly integrated systems configurations. In a wide variety of energy systems the high integration among components derives from the need of correctly exploiting all the internal heat sources by a proper matching with the internal heat sinks. To address this problem in a general way, in previous works it was suggested to extract from the system flowsheet a "basic configuration" including the components different from the heat exchangers (named "basic" components) and a set of hot and cold thermal flows (without considering the heat exchangers that realize the heat transfer among them). It was also shown how the comprehension of the processes occurring within the system can be strongly facilitated by analyzing separately the elementary thermodynamic cycles involved in the system processes. In this paper, a further step is done by considering the overall efficiency as a baseline efficiency, obtained from the contributions of the separate elementary cycles, with the additional contribution given by the thermal coupling (i.e. the internal heat transfer) among the cycles themselves. The advantages of this analysis are shown using the evolution of the STIG cycle towards more complex system configurations as an example of application

  • 48.
    Morandin, Matteo
    et al.
    University of Padova.
    Toffolo, Andrea
    Lazzaretto, Andrea
    University of Padova.
    On the Benefits of Separating the Heat Transfer Section and Analyzing Elementary Thermodynamic Cycles in Energy Systems Analysis2009In: 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. 8 : Energy systems: analysis, thermodynamics and sustainability, sustainable products and processes, p. 283-294Conference paper (Refereed)
    Abstract [en]

    The search for increasing performance and efficiency in energy system analysis leads to complex and highly integrated systems configurations. In a wide variety of energy systems the high integration among components derives from the need of correctly exploiting all the internal heat sources by a proper matching with the internal heat sinks. To address this problem in a general way, in previous works it was suggested to extract from the system flowsheet a “basic configuration” including the components different from the heat exchangers (named “basic” components) and a set of hot and cold thermal flows (without considering the heat exchangers that realize the heat transfer among them). It was also shown how the comprehension of the processes occurring within the system can be strongly facilitated by analyzing separately the elementary thermodynamic cycles involved in the system processes. In this paper, a further step is done by considering the overall efficiency as a baseline efficiency, obtained from the contributions of the separate elementary cycles, with the additional contribution given by the thermal coupling (i.e. the internal heat transfer) among the cycles themselves. The advantages of this analysis are shown using the evolution of the STIG cycle towards more complex system configurations as an example of application.

  • 49.
    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

  • 50.
    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.

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