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  • 1.
    Carvalho, Lara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. IVL – Swedish Environmental Institute, Stockholm, Sweden.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    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. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Öhrman, Olov G. W.
    IVL – Swedish Environmental Institute, Stockholm, Sweden;RISE Energy Technology Center AB, Piteå, Sweden.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Alkali enhanced biomass gasification with in situ S capture and a novel syngas cleaning: Part 2: Techno-economic analysis2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 165, no Part B, p. 471-482Article in journal (Refereed)
    Abstract [en]

    Previous research has shown that alkali addition has operational advantages in entrained flow biomass gasification and allows for capture of up to 90% of the biomass sulfur in the slag phase. The resultant low-sulfur content syngas can create new possibilities for syngas cleaning processes. The aim was to assess the techno-economic performance of biofuel production via gasification of alkali impregnated biomass using a novel gas cleaning systemcomprised of (i) entrained flow catalytic gasification with in situ sulfur removal, (ii) further sulfur removal using a zinc bed, (iii) tar removal using a carbon filter, and (iv) CO2 reductionwith zeolite membranes, in comparison to the expensive acid gas removal system (Rectisol technology). The results show that alkali impregnation increases methanol productionallowing for selling prices similar to biofuel production from non-impregnated biomass. It was concluded that the methanol production using the novel cleaning system is comparable to the Rectisol technology in terms of energy efficiency, while showing an economic advantagederived from a methanol selling price reduction of 2–6 €/MWh. The results showed a high level of robustness to changes related to prices and operation. Methanol selling prices could be further reduced by choosing low sulfur content feedstocks.

  • 2.
    Delgado-Bonal, Alfonso
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martín, Sandra Vázquez
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mier, Maria-Paz Zorzano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Solar and wind exergy potentials for Mars2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 102, p. 550-558Article in journal (Refereed)
    Abstract [en]

    The energy requirements of the planetary exploration spacecrafts constrain the lifetime of the missions, their mobility and capabilities, and the number of instruments onboard. They are limiting factors in planetary exploration. Several missions to the surface of Mars have proven the feasibility and success of solar panels as energy source. The analysis of the exergy efficiency of the solar radiation has been carried out successfully on Earth, however, to date, there is not an extensive research regarding the thermodynamic exergy efficiency of in-situ renewable energy sources on Mars. In this paper, we analyse the obtainable energy (exergy) from solar radiation under Martian conditions. For this analysis we have used the surface environmental variables on Mars measured in-situ by the Rover Environmental Monitoring Station onboard the Curiosity rover and from satellite by the Thermal Emission Spectrometer instrument onboard the Mars Global Surveyor satellite mission. We evaluate the exergy efficiency from solar radiation on a global spatial scale using orbital data for a Martian year; and in a one single location in Mars (the Gale crater) but with an appreciable temporal resolution (1 h). Also, we analyse the wind energy as an alternative source of energy for Mars exploration and compare the results with those obtained on Earth. We study the viability of solar and wind energy station for the future exploration of Mars, showing that a small square solar cell of 0.30 m length could maintain a meteorological station on Mars. We conclude that the low density of the atmosphere of Mars is responsible of the low thermal exergy efficiency of solar panels. It also makes the use of wind energy uneffective. Finally, we provide insights for the development of new solar cells on Mars.

  • 3.
    Furusjö, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. IVL Swedish Environmental Research Institute, Climate & Sustainable Cities.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Carvalho, Lara
    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.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Alkali enhanced biomass gasification with in situ S capture and novel syngas cleaning: Part 1: Gasifier performance2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 157, p. 96-105Article in journal (Refereed)
    Abstract [en]

    Previous research shows that alkali addition in entrained flow biomass gasification can increase char conversion and decrease tar and soot formation through catalysis. This paper investigates two other potential benefits of alkali addition: increased slag flowability and in situ sulfur capture.

    Thermodynamic equilibrium calculations show that addition of 2–8% alkali catalyst to biomass completely changes the chemical domain of the gasifier slag phase to an alkali carbonate melt with low viscosity. This can increase feedstock flexibility and improve the operability of an entrained flow biomass gasification process. The alkali carbonate melt also leads to up to 90% sulfur capture through the formation of alkali sulfides. The resulting reduced syngas sulfur content can potentially simplify gas cleaning required for catalytic biofuel production.

    Alkali catalyst recovery and recycling is a precondition for the economic feasibility of the proposed process and is effected through a wet quench. It is shown that the addition of Zn for sulfur precipitation in the alkali recovery loop enables the separation of S, Ca and Mg from the recycle. For high Si and Cl biomass feedstocks, an alternative separation technology for these elements may be required to avoid build-up.

  • 4.
    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.

  • 5.
    Höltinger, Stefan
    et al.
    Institute for Sustainable Economic Development, University of Natural Resources and Life Science Vienna, Austria.
    Mikovits, Christian
    Institute for Sustainable Economic Development, University of Natural Resources and Life Science Vienna, Austria.
    Schmidt, Johannes
    Institute for Sustainable Economic Development, University of Natural Resources and Life Science Vienna, Austria.
    Baumgartner, Johann
    Institute for Sustainable Economic Development, University of Natural Resources and Life Science Vienna, Austria.
    Arheimer, Berit
    Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden.
    Lindström, Göran
    Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    The impact of climatic extreme events on the feasibility of fully renewable power systems: a case study for Sweden2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 178, p. 695-713Article in journal (Refereed)
    Abstract [en]

    Long term time series of variable renewable energy (VRE) generation and electricity demand (load) provide important insights into the feasibility of fully renewable power systems. The coverage of energy statistics is usually too short or the temporal resolution too low to study effects related to interannual variability or the impact of climatic extreme events. We use time series simulated from climate data to assess the frequency, duration, and magnitude of extreme residual load events of two fully renewable power scenarios with a share of VRE generation (wind and solar PV) of about 50% for the case of Sweden. We define residual load as load – wind – PV – nuclear generation. Extreme residual load events are events that exceed the balancing or ramping capacities of the current power system. For our analysis, we use 29 years of simulated river runoff and wind and PV generation. Hourly load is derived from MERRA reanalysis temperature data by applying statistical models. Those time series are used along with historic capacity and ramping restrictions of hydro and thermal power plants in an optimization model to minimize extreme residual load events. Our analysis shows that even highly flexible power systems, as the Swedish one, are affected by climatic extreme events if they increase their VRE shares. Replacing current nuclear power capacities by wind power results on average in three extreme residual load events per year that exceed the current power system’s flexibility. Additional PV generation capacities instead of wind increase the number of extreme residual load events by about 4 %, as most events occur during the winter month when solar generation is close to zero and thus not able to counterbalance low wind events. Contrarily, overproduction and the need to curtail VRE generation become more pressing with higher shares of PV. In the discussion we highlight measures that could provide additional balancing capabilities to cope with the more frequent and severe residual load events in a fully renewable power system with high shares of VRE generation.

  • 6.
    Jafri, Yawer
    et al.
    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.
    Anheden, Marie
    RISE Research Institutes of Sweden, Stockholm.
    Kulander, Ida
    RISE Research Institutes of Sweden, Stockholm.
    Håkansson, Åsa
    Preem, Stockholm.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. IVL Swedish Environmental Research Institute Ltd., Stockholm.
    Multi-aspect evaluation of integrated forest-based biofuel production pathways: Part 1. Product yields & energetic performance2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 166, p. 401-413Article in journal (Refereed)
    Abstract [en]

    Forest-based biofuels are strategically important in forest-rich countries like Sweden but the technical performance of several promising production pathways is poorly documented. This study examines product yields and energy efficiencies in six commercially relevant forest-based “drop-in” and “high blend” biofuel production pathways by developing detailed spreadsheet energy balance models. The models are in turn based on pilot-scale performance data from the literature, supplemented with input from technology developers and experts. In most pathways, biofuel production is integrated with a market pulp mill and/or a crude oil refinery. Initial conversion is by pyrolysis, gasification or lignin depolymerization and intermediate products are upgraded by hydrotreatment or catalytic synthesis.

    While lignin oil (LO) hydrodeoxygenation had the highest expanded system efficiency, considerable uncertainty surrounds product yields owing to absence of suitable experimental data on LO upgrading. Co-feeding vacuum gas oil and fast pyrolysis oil in a fluidized catalytic cracker has a complex and uncertain effect on fossil yields, which requires further investigation. Co-locating bio-oil hydrotreatment at the refinery improves heat utilization, leading to higher system efficiencies. Explicit consideration of mill type and energy requirements is required to avoid performance misestimation as an assumption of energy surplus can confer a definite advantage.

  • 7.
    Jafri, Yawer
    et al.
    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.
    Anheden, Marie
    RISE Research Institutes of Sweden, Stockholm.
    Kulander, Ida
    RISE Research Institutes of Sweden, Stockholm.
    Håkansson, Åsa
    Preem, Stockholm.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. IVL Swedish Environmental Research Institute Ltd., Stockholm.
    Multi-aspect evaluation of integrated forest-based biofuel production pathways: Part 2, economics, GHG emissions, technology maturity and production potentials2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 172, p. 1312-1328Article in journal (Refereed)
    Abstract [en]

    Promoting the deployment of forest-based drop-in and high blend biofuels is considered strategically important in Sweden but many aspects of the overall performance of the foremost production technologies are as yet unexamined. This paper evaluates the technology maturity, profitability, investment requirements, GHG performance and Swedish biofuel production potential of six commercially interesting forest-based biofuel production pathways.

    Significant heterogeneity in technology maturity was observed. Lack of technical demonstration in industrially representative scales renders the liquefaction-hydrotreatment route for drop-in biofuels less mature than its gasification-catalytic upgrading counterpart. It is a paradox that short-term priority being accorded to pathways with the lowest technology maturity. Nth-of-a-kind investments in (a) gasification-based methanol, (b) hydropyrolysis-based petrol/diesel, and (c) lignin depolymerization-based petrol/diesel were profitable for a range of plant sizes. The profitability of pulp mill-integrated small gasification units (<100 MW) goes against the common perception of gasification being economically feasible only in large scales. New low-cost options for debottlenecking production at recovery boiler-limited kraft mills appear worth investigating. GHG emission reductions ranged from 66 to 95%; a penalty was incurred for high consumption of natural gas-based hydrogen. Swedish biofuel production potentials ranged from 4 to 27 TWh/y but a more feasible upper limit is 12–15 TWh/y.

  • 8. Johansson, Lars
    et al.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    An open absorption system installed at a sawmill: Description of pilot plant used for timber and bio-fuel drying2000In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 25, no 11, p. 1067-1079Article in journal (Refereed)
    Abstract [en]

    This work describes a pilot plant and its different parts in a system used for bio-fuel drying and timber drying with an open absorption process. This technique has not been used previously in Sweden in this application. The open absorption system has been installed on four timber dryers and one bio-fuel dryer at a sawmill located in the northern part of Sweden. The annual energy demand for the dryers has decreased considerably. The specific heat demand for a conventional drying system is about 5970 kJ/kg of evaporated water. For the open absorption system, the corresponding value is a heat demand of approximately 1400 kJ/kg of evaporated water. At the same time, an additional 360 kJ/kg of electricity has to be supplied. Here, 45,000 m3 per year of dried bio-fuel has been sold on the market as a result of the decreased heat demand in the wood dryers at the sawmill. The plant has been working well and has had a high availability. The pay-off time for the investment will be approximately 3 years for nondiscounted cash-flows

  • 9.
    Jonsson, Maria
    et al.
    Department of Chemical Engineering and Technology, Division of Energy Processes, Royal Institute of Technology, Stockholm, Sweden.
    Yan, Jinyue
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Department of Chemical Engineering and Technology, Division of Energy Processes, Royal Institute of Technology, Stockholm, Sweden.
    Humidified gas turbines: a review of proposed and implemented cycles2005In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 30, no 7, p. 1013-1078Article in journal (Refereed)
    Abstract [en]

    Gas turbines with air-water mixtures as the working fluid promise high electrical efficiencies and high specific power outputs to specific investment costs below that of combined cycles. Different humidified gas turbine cycles have been proposed, for example direct water-injected cycles, steam-injected cycles and evaporative cycles with humidification towers. However, only a few of these cycles have been implemented and even fewer are available commercially. This paper comprehensively reviews the literature on research and development on humidified gas turbines and identifies the cycles with the largest potential for the future. In addition, the remaining development work required for implementing the various humidified gas turbine cycles is discussed. This paper can also be used as a reference source that summarizes the research and development activities on humidified gas turbines in the last three decades.

  • 10.
    Kirtania, Kawnish
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Axelsson, Joel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kinetic study of catalytic gasification of wood char impregnated withdifferent alkali salts2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 118, p. 1055-1065Article in journal (Refereed)
    Abstract [en]

    Different concentrations (0.1 and 1 M K+/Na+) of salt solutions (K2CO3, Na2CO3, NaOH and NaCl) were used to impregnate alkali in sawdust. After devolatilization, char samples were gasified at different temperatures (750–900 °C) under CO2 in a macro-thermogravimetric analyzer for gasification kinetics. Morphologically, three classes of chars could be identified. Chars experiencing the highest catalytic influence were in Class-2 (0.5 M K2CO3 and 1 M NaOH) with a swollen and molten surface. In contrast, Class-1 (wood char like) and Class-3 (with salt deposits) chars showed moderate and low catalytic effect on gasification reactivity respectively. It is believed to be related to char surface swelling and alkali salt used. At 850 °C or below, the reactivity increased linearly (Class-1 and Class-3 Char) with initial alkali content up to 2200 mmol alkali/kg of char (except for NaCl). The same reaction rate was maintained until 3600 mmol/kg of char of alkali loading (Class-2) and then decreased. However, no trend was observed at 900 °C due to drastic change in reactivity of the samples, probably due to alkali transformation. Among the salts, K2CO3 (0.5 M) was found to be the most suitable for catalytic gasification due to its high catalytic activity in combination with relatively low carbon leaching.

  • 11.
    Kjellsson, Elisabeth
    et al.
    Lund University.
    Hellström, Göran
    Perers, B.
    Technical University of Denmark.
    Optimization of systems with the combination of ground-source heat pump and solar collectors in dwellings2009In: Energy, ISSN 0360-5442, E-ISSN 1873-6785Article in journal (Refereed)
    Abstract [en]

    The use of ground-source heat pumps for heating and domestic hot water in dwellings is common in Sweden. The combination with solar collectors has been introduced to reduce the electricity demand in the system. In order to analyze different systems with combinations of solar collectors and ground-source heat pumps, computer simulations have been carried out with the simulation program TRNSYS. Large differences were found between the system alternatives. The optimal design is when solar heat produces domestic hot water during summertime and recharges the borehole during wintertime. The advantage is related to the rate of heat extraction from the borehole as well as the overall design of the system. The demand of electricity may increase with solar recharging, because of the increased operating time of the circulation pumps. Another advantage with solar heat in combination with heat pumps is when the boreholes or neighbouring installations are drilled so close that they thermally influence each other. This may lead to decreasing temperatures in the ground, which gives decreased performance of the heat pump and increased use of electricity. The net annual heat extraction from the ground is reduced by recharge from solar heat. © 2009 Elsevier Ltd. All rights reserved.

  • 12.
    Krook-Riekkola, Anna
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Berg, Charlotte
    National Institute of Economic Research (NIER), Stockholm, Sweden.
    Ahlgren, Erik
    Chalmers University of Technology, Department of Energy and Environment.
    Söderholm, Patrik
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Challenges in top-down and bottom-up soft linking: Lessons from linking a Swedish energy system model with a CGE model2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 803-817Article in journal (Refereed)
    Abstract [en]

    This paper proposes and discusses a soft-linking procedure between a Computable General Equilibrium (CGE) model and an energy system model with the aim to improve national energy policy decision-making. Significant positive and negative experiences are communicated. Specifically, the process of soft-linking the EMEC and TIMES-Sweden models is presented, and unlike previous work we rely on the use of multiple direction-specific connection points. Moreover, the proposed soft-linking methodology is applied in the context of a climate policy scenario for Sweden. The results display a partly new description of the Swedish economy, which when soft-linking, generates lower CO2-emissions in the reference scenario due to a decline in industrial energy demand. These findings point at the importance of linking bottom-up and top-down models when assessing national energy and climate policies.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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

  • 16.
    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

  • 17.
    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

  • 18.
    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

  • 19. Leduc, Sylvain
    et al.
    Starfelt, F.
    Mälardalen University.
    Dotzauer, E.
    Mälardalen University.
    Kindermann, G.
    International Institute for Applied System Analysis (IIASA), Laxenburg.
    McCallum, I.
    International Institute for Applied System Analysis (IIASA), Laxenburg.
    Obersteiner, M.
    Obersteiner.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Optimal location of lignocellulosic ethanol refineries with polygeneration in Sweden2010In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 35, no 6, p. 2709-2716Article in journal (Refereed)
    Abstract [en]

    The integration of ethanol production with combined heat and power plants is considered in this paper. An energy balance process model has been used to generate data for the production of ethanol, electricity, heat and biogas. The geographical position of such plants becomes of importance when using local biomass and delivering transportation fuel and heat. An optimization model has thus been used to determine the optimal locations for such plants in Sweden. The entire energy supply and demand chain from biomass outtake to gas stations filling is included in the optimization. Input parameters have been studied for their influence on both the final ethanol cost and the optimal locations of the plants. The results show that the biomass cost, biomass availability and district heating price are crucial for the positioning of the plant and the ethanol to be competitive against imported ethanol. The optimal location to set up polygeneration plants is demonstrated to be in areas where the biomass cost is competitive and in the vicinity of small to medium size cities. Carbon tax does not influence the ethanol cost, but solicits the production of ethanol in Sweden, and changes thus the geography of the plant locations.

  • 20.
    Liu, H.
    et al.
    State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan.
    Saffaripour, M.
    Division of Energy and Furnace Technology, KTH Royal Institute of Technology.
    Mellin, P.
    Division of Energy and Furnace Technology, KTH Royal Institute of Technology.
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yang, W.
    Division of Energy and Furnace Technology, KTH Royal Institute of Technology.
    Blasiak, W.
    Division of Energy and Furnace Technology, KTH Royal Institute of Technology.
    A thermodynamic study of hot syngas impurities in steel reheating furnaces: Corrosion and interaction with oxide scales2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 77, p. 352-361Article in journal (Refereed)
    Abstract [en]

    Environmental concerns lead industries to implement gasified biomass (syngas) as a promising fuel in steel reheating furnaces. The impurities of syngas as well as a combination with iron oxide scale form complex mixtures with low melting points, and might cause corrosion on steel slabs. In this paper, the effects of syngas impurities are thermodynamically investigated, when scale formation on the steel slabs surface simultaneously takes place. A steel reheating furnace can be divided into preheating, heating, and soaking zones where the temperature of a steel slab changes respectively. Therefore, the thermodynamic calculation is performed at different temperatures to predict the fate of impurities. Then, the stable species are connected with respective zones in a reheating furnace. It is concluded that reactions due to alkali compounds, chloride, and particulate matter could take place on steel slabs. In the low temperature range, interaction of sodium chloride occured with pure iron prior to scale formation. Then, at high temperature the reactions of impurities are notable with iron oxides due to scale growing. Furthermore, the multicomponent reactions with syngas impurities showed that most of alkali contents evaporate at first stages, and only small amounts of them remain in slag at high temperature.

  • 21.
    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.

  • 22.
    Mesfun, Sennai
    et al.
    Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Leduc, Sylvain
    Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Patrizio, Piera
    Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Mendoza-Ponce, Alma
    Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Lammens, Tijs
    B.T.G. Biomass Technology Group B.V, Enschede, The Netherlands.
    Staritsky, Igor
    Wageningen Environmental Research (WENR), Team Earth Informatics, Wageningen, The Netherlands.
    Elbersen, Berien
    Wageningen Environmental Research (WENR), Team Earth Informatics, Wageningen, The Netherlands.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Kraxner, Florian
    Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Spatio-temporal assessment of integrating intermittent electricity in the EU and Western Balkans power sector under ambitious CO2 emission policies2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 164, p. 676-693Article in journal (Refereed)
    Abstract [en]

    This work investigates a power dispatch system that aims to supply the power demand of the EU and Western Balkans (EUWB) based on low-carbon generation units, enabled by the expansion of biomass, solar, and wind based electricity. A spatially explicit techno-economic optimization tool simulates the EUWB power sector to explore the dispatch of new renewable electricity capacity on a EUWB scale, under ambitious CO2 emission policies. The results show that utility-scale deployment of renewable electricity is feasible and can contribute about 9–39% of the total generation mix, for a carbon price range of 0–200 €/tCO2and with the existing capacities of the cross-border transmission network. Even without any explicit carbon incentive (carbon price of 0 €/tCO2), more than 35% of the variable power in the most ambitious CO2 mitigation scenario (carbon price of 200 €/tCO2) would be economically feasible to deploy. Spatial assessment of bio-electricity potential (based on forest and agriculture feedstock) showed limited presence in the optimal generation mix (0–6%), marginalizing its effect as baseload. Expansion of the existing cross-border transmission capacities helps even out the variability of solar and wind technologies, but may also result in lower installed RE capacity in favor of state-of-the-art natural gas with relatively low sensitivity to increasing carbon taxes. A sensitivity analysis of the investment cost, even under a low-investment scenario and at the high end of the CO2 price range, showed natural gas remains at around 11% of the total generation, emphasizing how costly it would be to achieve the final percentages toward a 100% renewable system.

  • 23.
    Moradi, Isaac
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Quality control of global solar radiation using sunshine duration hours2009In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 34, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to develop a new and automatic method for controlling the quality of daily global solar radiation, Gd, using sunshine duration hours. The new method has three levels of tests: first, Gd is compared against daily extraterrestrial radiation that is received on a horizontal surface (0.03×God≤Gdod); second, Gd should only exceed by a small amount of the daily clear sky irradiation that is observed under highly transparent clear skies (Gd<1.1Gcd); and third, the method uses a series of persistence checks that utilize the relation between daily global solar radiation and relative sunshine duration hours. The method is capable of identifying systematic and non-systematic errors and its ability has been shown in three different climates including semi-arid, coastal humid and very arid climates.

  • 24.
    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.

  • 25.
    Pardo, Nicholas
    et al.
    European Commission, DG Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten.
    Vatopoulos, Konstantinos
    European Commission, DG Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten.
    Krook-Riekkola, Anna
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Perez, Alicia
    European Commission, DG Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten.
    Methodology to estimate the energy flows of the European Union heating and cooling market2013In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 52, p. 339-352Article in journal (Refereed)
    Abstract [en]

    Over 40% of the total energy consumed in Europe is used for the generation of heat for either domestic or industrial purposes. Meanwhile, the demand for cooling is steadily increasing in all European Member State. In this context, it is essential to identify the heating and cooling demand in the economic sectors. The objective of this study is to propose a methodology to estimate the European heating and cooling demand by country, fuel, economical subsector and activity based on official statistics and reports from resource origin to the customer. The results show that most useful heat energy comes from the direct burn of a fuel principally natural gas. The contribution of the electricity is relatively moderate for the residential and service sectors but low for industrial sector. Most part of the cooling demand is generated by electrical cooling machines (air conditioning and chillers) which extract free environmental energy allowing compensate part of the losses from the electricity production. District heating has a moderate contribution and district cooling can be considered negligible.

  • 26.
    Patel, Alok
    et al.
    Molecular Microbiology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee (IIT-R), India.
    Pruthi, Vikas
    Molecular Microbiology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee (IIT-R), India.
    Pruthi, Parul A.
    Molecular Microbiology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee (IIT-R), India.
    Synchronized nutrient stress conditions trigger the diversion of CDP-DG pathway of phospholipids synthesis towards de novo TAG synthesis in oleaginous yeast escalating biodiesel production2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 139, p. 962-974Article in journal (Refereed)
  • 27.
    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.

  • 28.
    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.

  • 29.
    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

  • 30. Toffolo, Andrea
    et al.
    Lazzaretto, Andrea
    Department of Mechanical Engineering, University of Padova.
    Evolutionary algorithms for multi-objective energetic and economic optimization in thermal system design2002In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 27, no 6, p. 549-567Article in journal (Refereed)
    Abstract [en]

    Thermoeconomic analyses in thermal system design are always focused on the economic objective. However, knowledge of only the economic minimum may not be sufficient in the decision making process, since solutions with a higher thermodynamic efficiency, in spite of small increases in total costs, may result in much more interesting designs due to changes in energy market prices or in energy policies. This paper suggests how to perform a multi-objective optimization in order to find solutions that simultaneously satisfy exergetic and economic objectives. This corresponds to a search for the set of Pareto optimal solutions with respect to the two competing objectives. The optimization process is carried out by an evolutionary algorithm, that features a new diversity preserving mechanism using as a test case the well-known CGAM problem.

  • 31. 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

  • 32.
    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.

  • 33.
    Toloue Farrokh, Najibeh
    et al.
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
    Suopajärvi, Hannu
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
    Mattila, Olli
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Phounglamcheik, Aekjuthon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Romar, Henrik
    Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FI-90014, Oulu,.
    Sulasalmi, Petri
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu.
    Fabritius, Timo
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu.
    Slow pyrolysis of by-product lignin from wood-based ethanol production: A detailed analysis of the produced chars2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 164, p. 112-123Article in journal (Refereed)
    Abstract [en]

    Slow pyrolysis as a method of producing a high-quality energy carrier from lignin recovered from wood-based ethanol production has not been studied for co-firing or blast furnace (BF) applications up to now. This paper investigates fuel characteristics, grindability, moisture uptake and the flow properties of lignin chars derived from the slow pyrolysis of lignin at temperatures of 300, 500 and 650 °C (L300, L500 and L650 samples respectively) at a heating rate of 5 °C min-1. The lignin chars revealed a high mass and energy yield in the range of 39-73% and 53-89% respectively. Pyrolysis at 500 °C or higher, yielded lignin chars with low H/C and O/C ratios suitable for BF injection. Furthermore, the hydrophobicity of lignin was improved tremendously after pyrolysis. Pyrolysis at high temperatures increased the sphericity of the lignin char particles and caused some agglomeration in L650. Large and less spherical particles were found to be a reason for high permeability, compressibility and cohesion of L300 in contrast to L500 and L650. L300 and L500 chars demonstrated high combustibility with low ignition and burnout temperatures. Also, rheometric analysis showed that L500 has the best flow properties including low aeration energy and high flow function.

  • 34.
    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.

  • 35. Westerlund, Lars
    et al.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Johansson, Lars
    Theoretical investigation of the heat demand for public baths1996In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 21, no 7-8, p. 731-737Article in journal (Refereed)
    Abstract [en]

    Public baths normally use outdoor air to remove moisture from the building. This procedure results in large heating demands. A theoretical hour-based method for estimation of the heating demand has been developed. The method allows for dynamic behaviour with correct time periods for each mass-transfer level. Results of predictions with this method have been compared with yearly estimates of the heating demand based on actual measurements in a public bath. The difference is 3%. A parametric study shows that the air temperature and relative humidity in the building strongly influence the heating demand. Comparisons with other prediction methods based on use of the duration curve or mean annual outdoor temperature show differences less than 5% from results obtained with the hour-based method. The simpler approaches (use of a duration curve or mean value) fail when minimum outdoor airflow must be considered, as will be the case, for instance, when comparing different energy-saving systems or design of components for the climate system.

  • 36. Wetterlund, Elisabeth
    et al.
    Leduc, Sylvain
    International Institute for Applied System Analysis (IIASA), Laxenburg.
    Dotzauer, Erik
    Mälardalen University.
    Kindermann, Georg
    International Institute for Applied System Analysis (IIASA), Laxenburg.
    Optimal localisation of biofuel production on a European scale2012In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 41, no 1, p. 462-472Article in journal (Refereed)
    Abstract [en]

    This paper presents the development and use of an optimisation model suitable for analysis of biofuel production scenarios in the EU, with the aim of examining second generation biofuel production. Two policy instruments are considered – targeted biofuel support and a CO2 cost. The results show that over 3% of the total transport fuel demand can be met by second generation biofuels at a cost of approximately 65-73 EUR/MWh. With current energy prices, this demands biofuel support comparable to existing tax exemptions (around 30 EUR/MWh), or a CO2 cost of around 60 EUR/tCO2. Parameters having large effect on biofuel production include feedstock availability, fossil fuel price and capital costs. It is concluded that in order to avoid suboptimal energy systems, heat and electricity applications should also be included when evaluating optimal bioenergy use. It is also concluded that while forceful policies promoting biofuels may lead to a high biofuel share at reasonable costs, this is not a certain path towards maximised CO2 emission mitigation. Policies aiming to promote the use of bioenergy thus need to be carefully designed in order to avoid conflicts between different parts of the EU targets for renewable energy and CO2 emission mitigation.

  • 37. Wetterlund, Elisabeth
    et al.
    Pettersson, Karin
    Chalmers University of Technology, Department of Energy and Environment, Division of Heat and Power Technology.
    Harvey, Simon
    Chalmers University of Technology, Department of Energy and Environment, Division of Heat and Power Technology.
    Systems analysis of integrating biomass gasification with pulp and paper production - Effects on economic performance, CO2 emissions and energy use2011In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 36, no 2, p. 932-941Article in journal (Refereed)
    Abstract [en]

    This paper evaluates system aspects of biorefineries based on biomass gasification integrated with pulp and paper production. As a case the Billerud Karlsborg mill is used. Two biomass gasification concepts are considered: BIGDME (biomass integrated gasification dimethyl ether production) and BIGCC (biomass integrated gasification combined cycle). The systems analysis is made with respect to economic performance, global CO2 emissions and primary energy use. As reference cases, BIGDME and BIGCC integrated with district heating are considered. Biomass gasification is shown to be potentially profitable for the mill. The results are highly dependent on assumed energy market parameters, particularly policy support. With strong policies promoting biofuels or renewable electricity, the calculated opportunity to invest in a gasification-based biorefinery exceeds investment cost estimates from the literature. When integrated with district heating the BIGDME case performs better than the BIGCC case, which shows high sensitivity to heat price and annual operating time. The BIGCC cases show potential to contribute to decreased global CO2 emissions and energy use, which the BIGDME cases do not, mainly due to high biomass demand. As biomass is a limited resource, increased biomass use due to investments in gasification plants will lead to increased use of fossil fuels elsewhere in the system.

  • 38.
    Zetterholm, Jonas
    et al.
    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. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Pettersson, Karin
    RISE Research Institutes of Sweden, Eklandagatan 86, Göteborg, Sweden.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Evaluation of value chain configurations for fast pyrolysis of lignocellulosic biomass: Integration, feedstock, and product choice2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 144, p. 564-575Article in journal (Refereed)
    Abstract [en]

    Fast pyrolysis of lignocellulosic biomass constitutes a promising technology to reduce dependence on fossil fuels. The product, pyrolysis liquids, can either substitute heavy fuel oil directly, or be upgraded via e.g. hydroprocessing to diesel and petrol. This study presents a systematic evaluation of production costs and CO2 mitigation potentials of different fast pyrolysis value chain configurations. The evaluation considers types of localisations, emissions from electricity and hydrogen production, biomass feedstocks, and final products. The resulting production costs were found to be in the range of 36–60 EUR/MWh for crude pyrolysis liquids, and 61–90 EUR/MWh upgraded to diesel and petrol. Industrial integration was found to be favoured. The CO2 mitigation potential for the pyrolysis liquids was in the range of 187–282 t-CO2/GWh biomass. High variations were found when upgraded to diesel and petrol –best-case scenario resulted in a mitigation of 347 t-CO2/GWh biomass, while worst-case scenarios resulted in net CO2 emissions. Favourable policy support, continued technology development, and/or increased fossil fuel prices are required for the technology to be adapted on an industrial scale. It was concluded that integration with existing industrial infrastructure can contribute to cost reductions and thus help enable the transformation of traditional forest industry into biorefineries.

  • 39.
    Zhao, Xu
    et al.
    School of Business Administration, China University of Petroleum-Beijing, Changping, Beijing, China.
    Luo, Dongkun
    School of Business Administration, China University of Petroleum-Beijing, Changping, Beijing, China.
    Lu, Kun
    China-Russia Cooperation Department, CNPC, Dongcheng, Beijing, China.
    Wang, Xiaoyu
    Postal Savings Bank of China, Chaoyang, Beijing, China.
    Dahl, Carol
    Mineral and Energy Economics Program, Colorado School of Mines, Golden, CO, USA.
    How the removal of producer subsidies influences oil and gas extraction: A case study in the Gulf of Mexico2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 166, p. 1000-1012Article in journal (Refereed)
    Abstract [en]

    Since producer subsides can entail significant economic, fiscal, social and environmental costs, governments have been increasingly interested in removing them. Although many studies have been done on reducing consumer subsidies, subsidies to fossil fuel production are rarely discussed by scholars. This paper seeks to fill this void by developing an economic optimization model for oil and gas extraction to analyze the effects of producer subsidy removal. We forecast field-specific costs for exploration, development and production through constructing functions for the number of wells drilled and producing wells, production and economic limits. Various scenarios of phasing out producer subsidies in U.S. federal and state regulation on optimal production using field data from the Gulf of Mexicoare simulated, including removing royalty relief, amortization of geological and geophysical costs, and percentage depletion. The results show that removal of producer subsidies reduces the optimal production rate and investors' net present value and increases government revenue, but the total effect is a cost of net social benefits. Changes in both the discount rate and oil price have positive effects on optimal production, but they exert opposite effects on producer benefits. Our research is helpful for policy-makers to regulate an efficient subsidy removal path.

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