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  • 1.
    Aichmayer, Lukas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Garrido, Jorge
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental evaluation of a novel solar receiver for a micro gas-turbine based solar dish system in the KTH high-flux solar simulator2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 159, p. 184-195Article in journal (Refereed)
    Abstract [en]

    This work presents the experimental evaluation of a novel pressurized high-temperature solar air receiver for the integration into a micro gas-turbine solar dish system reaching an air outlet temperature of 800°C. The experiments are conducted in the controlled environment of the KTH high-flux solar simulator with well-defined radiative boundary conditions. Special focus is placed on providing detailed information to enable the validation of numerical models. The solar receiver performance is evaluated for a range of operating points and monitored using multiple point measurements. The porous absorber front surface temperature is measured continuously as it is one of the most critical components for the receiver performance and model validation. Additionally, pyrometer line measurements of the absorber and glass window are taken for each operating point. The experiments highlight the feasibility of volumetric solar receivers for micro gas-turbine based solar dish systems and no major hurdles were found. A receiver efficiency of 84.8% was reached for an air outlet temperature of 749°C. When using a lower mass flow, an air outlet temperature of 800°C is achieved with a receiver efficiency of 69.3%. At the same time, all material temperatures remain below permissible limits and no deterioration of the porous absorber is found.

  • 2.
    Anglart, Henryk
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.
    Li, Haipeng
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.
    Niewinski, Grzegorz
    Warsaw Univ Technol, Inst Heat Engn, Nowowiejska 21-25, PL-00665 Warsaw, Poland..
    Mechanistic modelling of dryout and post-dryout heat transfer2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 161, p. 352-360Article in journal (Refereed)
    Abstract [en]

    In this paper a new mechanistic model for the diabatic annular two-phase flow is presented and applied to prediction of dryout and post-dryout heat transfer in various channels. The model employs a computational fluid dynamics code - OpenFOAM (R) - to solve the governing equations of two-phase mixture flowing in a heated channel. Additional closure laws have been implemented to calculate the location of the dryout and to predict wall temperature in the post-dryout region. Calculated results have been compared with experimental data obtained in pipes and good agreement between predictions and measurements has been achieved. The presented model is applicable to complex geometries and thus can be used for prediction of post-dryout heat transfer in a wide variety of energy conversion systems.

  • 3. Bauer, N.
    et al.
    Hilaire, J.
    Brecha, R. J.
    Edmonds, J.
    Jiang, K.
    Kriegler, E.
    Rogner, Hans-Holger
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis. Int Inst Appl Syst Anal IIASA, Austria.
    Sferra, F.
    Assessing global fossil fuel availability in a scenario framework2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 111, p. 580-592Article in journal (Refereed)
    Abstract [en]

    This study assesses global, long-term economic availability of coal, oil and gas within the Shared Socio-economic Pathway (SSP) scenario framework considering alternative assumptions as to highly uncertain future developments of technology, policy and the economy. Diverse sets of trajectories are formulated varying the challenges to mitigation and adaptation of climate change. The potential CO2 emissions from fossil fuels make it a crucial element subject to deep uncertainties. The analysis is based on a well-established dataset of cost-quantity combinations that assumes favorable techno-economic developments, but ignores additional constraints on the extraction sector. This study significantly extends the analysis by specifying alternative assumptions for the fossil fuel sector consistent with the SSP scenario families and applying these filters (mark-ups and scaling factors) to the original dataset, thus resulting in alternative cumulative fossil fuel availability curves. In a Middle-of-the-Road scenario, low cost fossil fuels embody carbon consistent with a RCP6.0 emission profile, if all the CO2 were emitted freely during the 21st century. In scenarios with high challenges to mitigation, the assumed embodied carbon in low-cost fossil fuels can trigger a RCP8.5 scenario; low mitigation challenges scenarios are still consistent with a RCP4.5 scenario.

  • 4.
    Bundschuh, Jochen
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. University of Southern Queensland, Australia.
    Yusaf, Talal
    Maity, Jyoti Prakash
    Nelson, Emily
    Mamat, Rizalman
    Mahlia, T. M. Indra
    Algae-biomass for fuel, electricity and agriculture2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 78, p. 1-3Article in journal (Refereed)
  • 5.
    Chiu, Justin N. W.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Castro Flores, José Fiacro
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lacarrière, B.
    Industrial surplus heat transportation for use in district heating2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 110, p. 139-147Article in journal (Refereed)
    Abstract [en]

    M-TES (Mobile Thermal Energy Storage) technology is explored in this paper for transportation of industrial surplus heat for use in LTDH (low temperature district heating network). LTDH has promising potential in utilizing low grade heat, on the other hand, 20%–50% of industry generated surplus heat is often released to the ambient environment. M-TES is used to match thermal energy supply and demand that occur at different locations and that are shifted in time. In this paper, design of M-TES is conducted, optimization in operating strategies is performed, sensitivity analysis on levelized cost is studied, and environmental impact of CO2 emissions due to transportation is evaluated. The results of the study show an array of transportation means and storage operating strategies under which M-TES is technically, economically and environmentally sound for transportation of industrial surplus heat for use in LTDH network. © 2016 Elsevier Ltd

  • 6. Dhakouani, A.
    et al.
    Gardumi, Francesco
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Znouda, E.
    Bouden, C.
    Howells, Mark I.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Long-term optimisation model of the Tunisian power system2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 550-562Article in journal (Refereed)
    Abstract [en]

    The electricity mix in Tunisia mainly relied on conventional energy sources for over 50 years. Recently, due to fossil fuel prices oscillations and national reserves shortage, the need arose for restructuring the energy supply system. Targeting the integration of renewable energies could be a plan for satisfying the increasing demand and the supply independence. However, several macroeconomic conditions and policies present barriers for the integration of Renewable Energy Sources (RES), despite their abundance, availability and environmental benefits. This paper presents a long-term model of Tunisia electricity system, based on OSeMOSYS (Open Source energy MOdelling SYStem), aimed at unveiling potential benefits of increasing RES in electricity production. The paper first investigates peculiarities of Tunisia electricity system, arguing the necessity to include them in the electricity system model. Then, it explains the choice of OSeMOSYS and brought modifications, including peculiar system characteristics. Finally, the model is applied to two scenarios, a Business As Usual case and a 30% RES target in electricity production case, for time horizon 2010–2030. Results demonstrate the importance of system features detailed modelling. Specifically, they show that targeting RES state-invested integration in the electricity mix may allow higher energy independence to be reached, without increasing significantly system costs.

  • 7.
    Eid, Cherrelle
    KTH, School of Electrical Engineering (EES).
    Market integration of local energy systems: Is local energy management compatible with European regulation for retail competition?2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 114, p. 913-922Article in journal (Refereed)
    Abstract [en]

    The growing penetration of distributed energy resources is opening up opportunities for local energy management (LEM) – the coordination of decentralized energy supply, storage, transport, conversion and consumption within a given geographical area. Because European electricity market liberalization concentrates competition at the wholesale level, local energy management at the distribution level is likely to impose new roles and responsibilities on existing and/or new actors. This paper provides insights into the appropriateness of organizational models for flexibility management to guarantee retail competition and feasibility for upscaling. By means of a new analytical framework three projects in the Netherlands and one in Germany have been analysed. Both the local aggregator and dynamic pricing projects present potentials for retail competition and feasibility of upscaling in Europe.

  • 8.
    Endalew, Abebe K.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Zanzi, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Heterogeneous catalysis for biodiesel production from Jatropha curcas oil (JCO)2011In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 36, no 5, p. 2693-2700Article in journal (Refereed)
    Abstract [en]

    This work focuses on the development of heterogeneous catalysts for biodiesel production from high free fatty acid (FFA) containing Jatropha curcas oil (KO). Solid base and acid catalysts were prepared and tested for transesterification in a batch reactor under mild reaction conditions. Mixtures of solid base and acid catalysts were also tested for single-step simultaneous esterification and transesterification. More soap formation was found to be the main problem for calcium oxide (CaO) and lithium doped calcium oxide (Li-CaO) catalysts during the reaction of jatropha oil and methanol than for the rapeseed oil (RSO). CaO with Li doping showed increased conversion to biodiesel than bare CaO as a catalyst. La(2)O(3)/ZnO, La(2)O(3)/Al(2)O(3) and La(0.1)Ca(0.9)MnO(3) catalysts were also tested and among them La(2)O(3)-ZnO showed higher activity. Mixture of solid base catalysts (CaO and Li-CaO)and solid acid catalyst (Fe(2)(SO(4))(3)) were found to give complete conversion to biodiesel in a single-step simultaneous esterification and transesterification process. (C) 2011 Elsevier Ltd. All rights reserved.

  • 9.
    Fischer, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Wolf, T.
    Wapler, J.
    Hollinger, R.
    Madani Larijani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Model-based flexibility assessment of a residential heat pump pool2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 118, p. 853-864Article in journal (Refereed)
    Abstract [en]

    This paper presents and demonstrates a methodology to explore the flexibility of a heat pump pool. Three points are in the focus of this work: First the procedure to model a pool of residential heat pump systems. Second the study of the response of a large number of heat pumps when the Smart-Grid-Ready interface is used for direct load control. Third a general assessment of flexibility of a pool of heat pump systems. The presented pool model accounts for the diversity in space heating and domestic hot water demands, the types of heat source and heat distribution systems used and system sizing procedures. The model is validated using field test data. Flexibility is identified by sending trigger signals to a pool of 284 SG-Ready heat pumps and evaluating the response. Flexibility is characterized by maximum power, shiftable energy and regeneration time. Results show that flexibility is highly dependent on the ambient temperature and the use of an electric back-up heater. It is found that using SG-Ready-like signals offers significantly higher flexibility than just switching off heat pumps, as it is mostly done today.

  • 10.
    Fuso-Nerini, Francesco
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Dargaville, Roger
    Howells, Mark
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis. Columbia Univ, NY USA.
    Bazilian, Morgan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Estimating the cost of energy access: The case of the village of Suro Craic in Timor Leste2015In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 79, p. 385-397Article in journal (Refereed)
    Abstract [en]

    Energy access targets at national, sub-national, and local levels, are often not specified in great detail - and tend to focus on supply. Another approach to better inform policy and investment might benefit from an indicator that focuses on the services derived from electricity access. To provide support for decision-making, this research investigates the costs of reaching different levels of energy access in rural areas, with a case study of a village in the Ainaro district of Timor Leste. Utilizing the multi-tier definition of energy access proposed in the World Bank's "Global Tracking Framework" for Sustainable Energy for All, we present results both on the cost difference of achieving different tiers of energy access, and on the comparison among selected electrification and cooking options. Results show that in the period 2010-2030 achieving the highest tier of electricity access could be as much as seventy-five times more costly than achieving the lowest one. In addition moving across tiers, least cost solutions shift from stand-alone to mini-grid and finally grid connected options as electricity access increases. Regarding cooking, moving from open fires to some of the more modern solutions has the potential to reduce overall costs over the same period.

  • 11.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Characterization of the KTH high-flux solar simulator combining three measurement methods2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 2091-2099Article in journal (Refereed)
    Abstract [en]

    This paper presents the characterization of the first Fresnel lens-based High-Flux Solar Simulator (HFSS) showing the evaluation of the total thermal radiative power dependent on the aperture radius at the focal plane. This result can be directly applied to calculate the thermal power input into any solar receiver tested in the KTH HFSS. Three measurement setups were implemented and their results combined to assess and verify the characterization of the solar simulator: a thermopile sensor measuring radiative flux, a CMOS camera coupled with a Lambertian target to obtain flux maps, and a calorimeter to measure the total thermal power within an area of 300×300 mm. Finally, a Monte Carlo analysis was performed to calculate the total uncertainties associated to each setup and to combine them to obtain the simulator characterization. The final result shows a peak flux of 6.8 ± 0.35 MW/m2 with a thermal power of 14.7 ± 0.75 kW within an aperture of 180 mm in diameter at the focal plane, and a thermal-electrical conversion efficiency of 25.8 ± 0.3%. It was found very good repeatability and a stable energy output from the lamps during the experiments.

  • 12.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Paleta, Rita
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Pina, André
    Feasibility study of using a biogas engine as backup in a decentralized hybrid (PV/wind/battery) power generation system: Case study Kenya2015In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 90, no 2, p. 1830-1841Article in journal (Refereed)
    Abstract [en]

    In this study, a hybrid power system consisting of PV (Photovoltaics) panels, a wind turbine and a biogas engine is proposed to supply the electricity demand of a village in Kenya. The average and the peak load of the village are around 8kW and 16.5kW respectively.The feasibility of using locally produced biogas to drive a backup engine in comparison to using a diesel engine as backup has been explored through a techno-economic analysis using HOMER (Hybrid Optimization Model for Electric Renewables). This hybrid system has also been compared with a single diesel based power system.The results show that the hybrid system integrated with the biogas engine as backup can be a better solution than using a diesel engine as backup. The share of power generation by PV, wind and biogas are 49%, 19% and 32%, respectively. The LCOE (Levelized Cost of Electricity) of generated electricity by this hybrid system ($0.25/kWh) is about 20% cheaper than that with a diesel engine as backup ($0.31/kWh), while the capital cost and the total NPC (Net Present Cost) are about 30% and 18% lower, respectively.Regarding CO2 emissions, using a biogas engine as backup saves 17 tons of CO2 per year compared to using the diesel engine as backup.

  • 13. Ghezelbash, Reza
    et al.
    Farzaneh-Gord, Mahmood
    Behi, Hamidreza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Sadi, Meisam
    Khorramabady, Heshmatollah Shams
    Performance assessment of a natural gas expansion plant integrated with a vertical ground-coupled heat pump2015In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 93, p. 2503-2517Article in journal (Refereed)
    Abstract [en]

    In the present paper, a vertical ground-coupled heat pump system is proposed for energy saving in a natural gas expansion plant. Such plant is a modern type of conventional natural gas pressure drop station. Unlike the conventional type, which waste the natural gas pressure exergy in throttling process, the modern one uses the pressure exergy of the natural gas for producing electrical power. A remarkable feature of the proposed system is the type of energy resource used for preheating aim. In previous studies, natural gas was used for the preheating process, however: the proposed system employs geothermal energy as a renewable energy resource for providing part of heating demand. Initially, the vertical ground-coupled heat pump system preheats the natural gas stream up to medium temperatures, then, gas stream passes through station heater and reaches the desired temperature. For studying the economic and thermal performance of the proposed system, first of all, a system with a high net present value is selected, and then the performance of the selected system is studied in detail. The analysis revealed that the fuel saving potential of the system is 45.80% annually. Economically, the discounted payback period was also calculated about 6 years.

  • 14.
    Grönkvist, Stefan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Bryngelsson, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Westermark, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Oxygen efficiency with regard to carbon capture2006In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 31, no 15, p. 3220-3226Article in journal (Refereed)
    Abstract [en]

    Carbon capture is often discussed in the literature with the sole focus on power processes, despite the fact that carbon dioxide emissions from other sources are just as relevant for the impact on the atmosphere. Furthermore, some carbon capture methods are relatively inefficient when applied to power production processes. Carbon capture should preferably be performed where the cost is as low as possible, i.e. not necessarily from power production processes. As an example, carbon capture using combustion with pure oxygen is far more energy efficient if it is used together with lime kilns or cement kilns than together with power production processes. A new concept termed "oxygen efficiency" is introduced in this paper. It describes the amount of carbon dioxide that can potentially be captured per unit of oxygen. As such, the oxygen efficiency quantifies the value of a certain unit of oxygen for carbon capture reasons. The base concept is that the energy penalty for the production of one part of oxygen is the same no matter where it is produced; hence, if this unit of oxygen can be used to capture more carbon dioxide, it is more efficient. Typically, the oxygen efficiency would be five times greater for carbon capture when utilising pure oxygen together with cement kilns rather than together with methane-fired power plants. Furthermore, the concept of oxygen efficiency illustrates the importance of considering how carbon capture methods can be utilised in the most efficient way, in addition to evaluating which carbon capture method is the most suitable for a particular technology.

  • 15.
    Gunarathne, Duleeka Sandamali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Mueller, Andreas
    Fleck, Sabine
    Kolb, Thomas
    Chmielewski, Jan Karol
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Gasification characteristics of steam exploded biomass in an updraft pilot scale gasifier2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 71, p. 496-506Article in journal (Refereed)
    Abstract [en]

    Pretreatment of biomass becomes more and more important due to the large scale application of biomass having low energy density. In this paper, steam exploded biomass pellets (Black pellets) and unpretreated biomass pellets (Gray pellets) were gasified with air and steam at an updraft HTAG (High Temperature Agent Gasification) unit. Decomposition characteristics of pellets were first analyzed with TGA (thermo gravimetric analysis). Early decomposition of hemicellulose and cellulose were seen with Black pellets around 241 degrees C and 367 degrees C respectively. Introducing CO2 led comparatively high mass loss rate with Black pellets. Gasification of Black pellets resulted in syngas with high CO and hydrocarbon contents while Gasification of Gray pellets resulted in high H-2 content of syngas. LHV (lower heating value) of syngas was high around 7.3 MJ/Nm(3) and 10.6 MJ/Nm(3) with air gasification and steam gasification respectively. Even with significantly low syngas temperature with gasification of Black pellets, only slightly high total tar content was seen compared to that of Gray pellets gasification. Phenolic compounds dominated the tar composition. In general, steam gasification of Black pellets seems to be more feasible if syngas with high energy value is desired. If higher H-2 yield is preferred, gasification of unpretreated pellets likely to be more attractive.

  • 16.
    He, Bo
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Martin, Viktoria
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Setterwall, Fredrik
    Phase transition temperature ranges and storage density of paraffin wax phase change materials2004In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 29, no 11, p. 1785-1804Article in journal (Refereed)
    Abstract [en]

    Paraffin waxes have been used in many latent thermal energy storage applications because of their advantageous thermal performances. In this paper, the liquid-solid phase diagram of the binary system of tetradecane and hexadecane has been used to obtain information of the phase transition processes for cool storage applications. The analysis of the phase diagram indicates that, except for the minimum-melting point mixture, all mixtures melt and freeze in a temperature range and not at a constant temperature. The latent heat of fusion evolves throughout this temperature range. Differential scanning calorimetry (DSC) was used to determine the thermophysical properties of the binary system. Depending on the DSC settings throughout the measurements, varying results were obtained. For example, when the DSC runs at a high heating/cooling rate, it will lead to erroneous information. Also, the correct phase transition temperature range cannot be obtained simply from DSC measurement. By combining phase equilibrium considerations with DSC measurements, a reliable design method to incorporate both the heat of phase change and the temperature range is presented.

  • 17.
    Islam, M. S.
    et al.
    KTH, School of Electrical Engineering (EES).
    Akhter, R.
    Rahman, M. A.
    A thorough investigation on hybrid application of biomass gasifier and PV resources to meet energy needs for a northern rural off-grid region of Bangladesh: A potential solution to replicate in rural off-grid areas or not?2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 145, p. 338-355Article in journal (Refereed)
    Abstract [en]

    Rural electrification is a critical global challenge specifically in developing countries and Bangladesh is no exception. Most of the people live in the rural areas of the country and having no access to grid electricity hindering the development of these areas and the overall progress of the country's economy severely. In this regard, renewable energy based hybrid mini-grid can be a viable solution to ensure access to electricity for all. This paper presents a case study of supplying electricity through hybrid mini-grid to the rural unelectrified areas of the northern region of Bangladesh, and provides an analysis of its business creation, operation and related challenges. The study involves modelling of three alternative configurations for electricity generation with the different combination of solar energy, biomass generator, diesel generator and battery storage resources. Hybrid Optimization Model for Electric Renewable (HOMER) software is used to carry out the techno-economic analysis and identify the optimal off-grid system configuration. The analysis exposed that the per unit cost of electricity from the optimum off-grid supply configuration is much higher than the regulated tariff for grid connected residential consumers and cannot reach grid parity even with the full capital subsidy. However, the cost of off-grid supply is economical than the diesel-only supply option or the cost of owning a solar home system. The analysis further considered different electricity selling tariff to obtain a practical and reasonable payback period to make the proposed hybrid mini-grid system economically worthwhile. From the emission analysis, it is found that the proposed hybrid system would produce 75% lower CO2 than the existing methods of fulfilling energy needs in the study area. 

  • 18. Jonsson, M.
    et al.
    Yan, Jinyue
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Ammonia-water bottoming cycles: a comparison between gas engines and gas diesel engines as prime movers2001In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 26, no 1, p. 31-44Article in journal (Refereed)
    Abstract [en]

    Ammonia-water cycles can produce more power than steam Rankine cycles in several applications. One of these applications is as a bottoming cycle to internal combustion engines. In the present study, ammonia-water bottoming cycle configurations for spark-ignition gas engines and compression-ignition gas diesel engines have been compared, Single-pressure Rankine cycles have been used as a basis for the comparison. Low heat source temperatures should increase the difference in power output between the ammonia-water cycle and the Rankine cycle. However, in this study, the results of the simulations show different trends. In most cases, the ammonia-water bottoming cycles with gas engines as prime movers generate more power compared to a Rankine cycle than when gas diesel engines are the prime movers. The temperature of the most important waste heat source, the exhaust gas, is approximately 100 degreesC higher for the gas engines than for the gas diesel engines. Therefore, for the gas engines, most of the waste heat available to a bottoming cycle is in the form of relatively high-temperature exhaust gas, while for the gas diesel engines more of the waste heat is in the form of relatively low-temperature heat sources.

  • 19. Jonsson, M.
    et al.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    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, review/survey (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.

  • 20.
    Kabalina, Natalia
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Universidade de Lisboa, Portugal.
    Costa, Mario
    Weihong, Yang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Martin, Andrew R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Energy and economic assessment of a polygeneration district heating and cooling system based on gasification of refuse derived fuels2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 137, p. 696-705Article in journal (Refereed)
    Abstract [en]

    Conventional district heating and cooling (DHC) systems are compelled to reduce their fossil fuel dependency while ensuring profitability as cooling and heating demands decline. One solution is to retrofit the system with a gasifier and product gas upgrading equipment so that the system will be able to diversify its fuel input, including biomass and waste resources, while simultaneously producing synthetic natural gas (SNG), synthetic gas (syngas) and char complementarily to heat, cold and electricity. The main objective of this study is to assess energetically and economically a polygeneration DHC system based on gasification of refuse derived fuels considering the following sub-product scenarios: char; char and syngas; char and SNG; and char, syngas and SNG. The results show that when char is the only sub product of the modified DHC system, the investment payback is 3 years, the discounted net cash flow (DNCF) is 142 mln USD, and the system trigeneration efficiency is 83.6%. When other sub-products are supplied by the system, its performance reduces but the system DNCF increases, while the investment payback remains constant.

  • 21.
    Khan, MD. Ershad Ullah
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Optimization of hybrid renewable energy polygeneration system with membrane distillation for rural households in Bangladesh2015In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 93, p. 1116-1126Article in journal (Refereed)
    Abstract [en]

    Despite the country's rural electrification program, kerosene is the predominant source for lighting, and woody biomass is virtually the only option available for cooking. The rural population also struggles with unsafe drinking water in terms of widespread arsenic contamination of well water. Biogas plants and pV are individually impractical to serve both cooking, lighting and water purification systems, and their combined applications are extremely limited. This study considers a holistic approach towards tackling both of these issues via integrated renewable energy-based polygeneration employed at the village level. The polygeneration unit under consideration provides electricity via a pV array and animal and agriculture waste-fed digester, which in turn is coupled to a gas engine. Excess digester gas is employed for cooking and lighting, while waste heat from the process drives a membrane distillation unit for water purification. Technical assessments and optimization have been conducted with HOMER (Hybrid Optimization of Multiple Energy Resources). Results show that daily electricity demand can be met with such a system while simultaneously providing 0.4 m3 cooking fuel and 2e3 L pure drinking water. Cost estimates indicate that this approach is highly favorable to other renewable options. The pay back period of such system is between 3 and 4 years.

  • 22.
    Khatiwada, Dilip
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Seabra, Joaquim
    Faculdade de Engenharia Mecânica, UNICAMP, and Brazilian Bioethanol Science and Technology Laboratory (CTBE), Campinas, SP, Brazil.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Walter, Arnaldo
    Faculdade de Engenharia Mecânica, UNICAMP, and Brazilian Bioethanol Science and Technology Laboratory (CTBE), Campinas, SP, Brazil.
    Power generation from sugarcane biomass - A complementary option to hydroelectricity in Nepal and Brazil2012In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 48, no 1, p. 241-254Article in journal (Refereed)
    Abstract [en]

    This paper discusses the complementarity between hydroelectricity and surplus electricity from sugarcane biomass based cogeneration plants in sugarcane mills. The paper investigates opportunities and barriers in the context of governments' initiatives, institutions and prevailing regulatory frameworks in Brazil and Nepal. The paper finds that bioelectricity from cogeneration can be a good complementary option for hydroelectric power, helping foster diversification on the generation side and enhance security of electricity supply based on local resources. Bioelectricity potential from sugarcane biomass is estimated to be in the range of 209 - 313 GWh for Nepal and 62 -93 TWh for Brazil. In Nepal, the grid connected bioelectricity can provide power for operating industries, and support local development through rural electrification. In Brazil, the biomass potential can be further enhanced through a better utilization of the biomass in the sugar-ethanol industry to balance hydropower availability. This comparative study offers a reflection on the need for better planning and policies to address the barriers which are hindering the development of bioelectricity even in places where the potential is large.

  • 23.
    Khatiwada, Dilip
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Scenarios for bioethanol production in Indonesia: How can we meet mandatory blending targets?2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, ISSN ISSN: 0360-5442, Vol. 119, p. 351-361Article in journal (Refereed)
    Abstract [en]

    This study investigates the potential of bioethanol production and fossil fuel substitution using sugarcane feedstock in Indonesia. Current production practices, government biofuel policies (esp. mandatory blending targets), and sugar self-sufficiency are simulated to project the total potential of fuel ethanol and land requirements in the timeframe between 2015 and 2025. At present conditions, 450 million liters bioethanol can be annually produced in Indonesia using sugarcane molasses, a low-value co-product. This gives only a marginal contribution equivalent to 1% of the total gasoline consumption in 2015. The study examines the ethanol production potential after domestic sugar self-sufficiency is achieved by 2020. In 2015, 0.71 Mha land were required for sugarcane cultivation in order to meet a 2% blend mandate i.e. 0.68 billion liters (BL) ethanol using only cane-molasses. Juice ethanol is needed to meet the blending targets set for 2020 (i.e., 4.45 BL ethanol) and 2025 (i.e., 11.48 BL ethanol). This translates into sugarcane feedstock obtained from 1.60 Mha and 2.76 Mha land, respectively. The study also evaluates how improved resource efficiency can be achieved, exploring the bioelectricity production potential from sugarcane biomass, improvements in yields, and modernization of sugarcane mills. The results highlight how the use of established technologies and production methods can help develop agro-industries in the sugar ethanol segment of Indonesia.

  • 24.
    Levihn, Fabian
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    CHP and heat pumps to balance renewable power production: Lessons from the district heating network in Stockholm2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 137, p. 670-678Article in journal (Refereed)
    Abstract [en]

    There is a potential for utilizing a combination of combined heat and power (CHP) plants together with large scale heat pumps in district heating systems to balance intermittent renewable power production. The thought is to use a combination of both power production and consumption to balance both surplus and deficit in the electric power market. Much research has presented different modelling and simulations of such systems. This particular study present lessons and empirics from operating such a system. The DH system in Stockholm is large with over 12 TWh of heat demand annually. Since the 1970s the system has been operated with both CHPs and heat pumps. About 660 MW of heat pumps and 300 MW of electric boilers are currently operational in this system. Both the district heating and district cooling systems are equipped with storage. Besides constituting an empirical example, the paper contributes with input to future modelling of this kind of system.

  • 25.
    Levihn, Fabian
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    CO2 emissions accounting: Whether, how, and when different allocation methods should be used2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 68, p. 811-818Article in journal (Refereed)
    Abstract [en]

    CO2 abatement and the transition to sustainable energy systems are of great concern, calling for investments in both old and new technologies. There are many perspectives on how to account for these emissions, not least when it comes to how the roles of different alternative energy production options should be emphasized. Confusion and conflicting interests regarding the appropriate accounting methods for allocating CO2 emissions interfere with effective energy policy and the efficient use of corporate and national resources. Possible investments in the Stockholm district heating network and how they interact with the electric power grid illustrate the influence of different accounting methods on alternative energy production options. The results indicate that, for several abatement options, performance in terms of reduced CO2 emissions might be either improved or degraded depending on whether or how alternative electricity production is accounted for. The results provide guidelines for whether, how, and when different allocation methods are appropriate, guidelines relevant to academia, industrial leaders, and policymakers in multiple areas related to power production and consumption.

  • 26.
    Levihn, Fabian
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    On the problem of optimizing through least cost per unit, when costs are negative: Implications for cost curves and the definition of economic efficiency2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 114, p. 1155-1163Article in journal (Refereed)
    Abstract [en]

    For society and industry alike, efficient allocation of resources is crucial. Numerous tools are available that in different ways rank available options and actions under the aim to minimize costs or maximize profit. One common definition of economic efficiency is least cost per unit supplied. A definition that becomes problematic if cost take negative values. One model, where negative costs are not uncommon, is expert based/bottom up [marginal abatement] cost curves. This model is used in many contexts for understanding the impact of economic policy as well as optimizing amongst potential actions. Within this context attention has been turned towards the ranking problem when costs are negative.

    This article contributes by widening the discussion on the ranking problem from the MACC context to the general definition of least cost per unit supplied. Further it discuss why a proposed solution to the ranking problem, Pareto optimization, is not a good solution when available options are interdependent. This has particular consequences for the context of energy systems, where strong interdependencies between available options and actions are common. The third contribution is a proposed solution to solve the ranking problem and thus how to define economic efficient when costs are negative.

  • 27.
    Levihn, Fabian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Nuur, Cali
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Laestadius, Staffan
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Marginal abatement cost curves and abatement strategies: Taking option interdependency and investments unrelated to climate change into account2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 76, p. 336-344Article in journal (Refereed)
    Abstract [en]

    Firms usually have optimization tools for evaluating various investment options; policymakers likewise need tools for designing economically efficient policies. One such tool is the MACC (marginal abatement cost curve), used to capture the least-cost sequence of abatement options. Such curves are also used for understanding the implications of government policies for markets and firms. This article explores dynamic path-dependent aspects of the Stockholm district heating system case, in which the performance of some discrete options is conditioned by others. In addition, it proposes adding a feedback loop to handle option redundancy when implementing a sequence of options. Furthermore, in an energy system, actions unrelated to climate change abatement might likewise affect the performance of abatement options. This is discussed together with implications for climate change policy and corporate investment optimization. Our results indicate that a systems approach coupled with a feedback loop could help overcome some of the present methodological limitations.

  • 28.
    Lille, Simon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Jewartowski, Marcin
    Experimental study of the fuel jet combustion in high temperature and low oxygen content exhaust gases2005In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 30, no 2-4, p. 373-384Article in journal (Refereed)
    Abstract [en]

    The performance of high temperature air combustion (HiTAC) depends oil the heat regenerator efficiency and on the way fuel is mixed with furnace gases. In this work. combustion of a fuel jet of gasol (>95% of propane) was investigated experimentally. Experiments were carried out in steady-state conditions using a single jet flame furnace. The jet of fuel was co-axially injected into high temperature exhaust gases generated by means of a gas burner also fired with gasol. Thus. instead of highly preheated and oxygen depleted air, which was normally used by other researches for such studies. this work has used high temperature and low oxygen content exhaust gases as the oxidiser. A water-cooled fuel nozzle was used to control fuel inlet temperature. Influence of the oxygen content in the oxidiser. at temperatures of 860-890 degreesC, on the flame visibility and the reactants composition was investigated. The combustion of gasol in hot flue cyases appeared to be very stable and complete even at very low oxygen concentration. The oxygen concentration in the oxidiser was found to have a substantial effect on flame size, luminosity, colour, visibility and lift-off distance. Reduced oxygen concentration increases the flame size and lift-off distance, and decreases luminosity and visibility. The HiTAC flame first became bluish and then non-visible at sufficiently low concentration of oxygen in the oxidiser. In this work. results are presented for the constant ratio between fuel Jet velocity and velocity of co-flowing flue gases. ThB ratio was equal to 26.

  • 29.
    Lindfeldt, Erik G.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Westermark, Mats O.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    System study of carbon dioxide (CO2) capture in bio-based motor fuel production2008In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 33, no 2, p. 352-361Article in journal (Refereed)
    Abstract [en]

    A number of different technologies for producing renewable motor fuels have been studied; some effects of applying carbon dioxide (CO2) capture to the production of renewable motor fuels are described in this paper. Some of the technologies studied are well suited for CO2 capture. However, it is shown that the advantages with CO2 capture for these technologies are not enough to offset their shortcomings described in previous studies, which show that the largest CO2 reduction from biomass in Sweden may be achieved by producing fuel pellets for coal substitution or using the biomass in combined heat and power plants. A conclusion of the present paper is that even with v capture added to the respective technology, it is inefficient to use renewable resources for motor fuel production if the aim is to achieve as high CO2 emission reduction as possible per input of biomass. Therefore, the large Swedish subsidies of the production of motor fuels appear sub-optimal, also when the possibility of CO2 capture is considered. Nevertheless, incorporating CO2 capture in the production of renewable motor fuels from biomass might be a cost-effective way of reducing CO2 emissions.

  • 30.
    Lindmark, Susanne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Westermark, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Martin, Viktoria
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Dirodi, Natalia
    System Aspects of Trigeneration based on Humidified Gas Engine with Flue Gas CondensationIn: Energy, ISSN 0360-5442, E-ISSN 1873-6785Article in journal (Other academic)
  • 31.
    Liu, H.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology. Huazhong University of Science and Technology, China .
    Saffari Pour, Mohsen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Mellin, Pelle
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Grip, C. -E
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace 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.

  • 32.
    Lorenzi, Guido
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Universidade de Lisboa, Portugal.
    Lanzini, Andrea
    Santarelli, Massimo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Politecnico di Torino, Italy.
    Martin, Andrew R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Exergo-economic analysis of a direct biogas upgrading process to synthetic natural gas via integrated high-temperature electrolysis and methanation2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 1524-1537Article in journal (Refereed)
    Abstract [en]

    Biogas upgrading to synthetic natural gas (SNG) is a viable and appealing route for power-to-gas because it combines waste management with the use of the surplus electricity that might arise in energy systems having a considerable share of renewable energy sources in their production mix. In this work, the exergo-economic performance of a biogas upgrading process through integrated electrolysis and methanation is assessed in connection with the current market status to test which conditions could make the proposed option economically viable. Two different configurations, which differ mainly for the operating pressure of the electrolyser, are compared. The exergy efficiencies are high (>80%) and exergo-economic costs of the produced bio-SNG in the two analyzed configurations are 5.62 and 4.87 c(sic)/kWh(exergy), for low- and high-pressure respectively. Lower values would be required for the bio-SNG to compete with fossil natural gas. We show how both the input electricity price and the capacity factor have a substantial impact on the economic sustainability of the process. Eventually, the monetary exploitation of the oxygen produced by electrolysis and the participation to the emission trading scheme could contribute further to improve the economic attractiveness of the process.

  • 33.
    Mainali, Brijesh
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Financing off-grid rural electrification: Country case Nepal2011In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 36, no 4, p. 2194-2201Article in journal (Refereed)
    Abstract [en]

    More than 61% of the total population of Nepal has no access to electricity. The majority is poor and live in rural areas. In recent years, rural electrification has had high priority in government policies, and micro hydro and solar PV have been the most commonly adopted off-grid technologies. The financial mix in the off-grid rural electrification is generally characterized by subsidy, equity and credit. In this paper, we analyze how rural electrification has been funded and the impact of subsidy policies on the renewable energy market, focusing on the projects implemented under the ‘subsidy policy 2000’. Our study is based on official data obtained from authorities in Nepal and a survey carried out among private supply and installation companies, NGOs and financial institutions. The study shows that awareness levels in adopting RE-technologies and willingness of people to access and pay for electricity have increased significantly. However, there is a huge financial gap between the cost of electrification and the affordability. Bridging this gap is a crucial issue that needs to be addressed for the smooth expansion of rural electrification in the country.

  • 34. Maity, Jyoti Prakash
    et al.
    Bundschuh, Jochen
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. University of Southern Queensland, Australia.
    Chen, Chien-Yen
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Microalgae for third generation biofuel production, mitigation of greenhouse gas emissions and wastewater treatment: Present and future perspectives - A mini review2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 78, p. 104-113Article in journal (Refereed)
    Abstract [en]

    The extensive use of fossil fuels is increasingly recognized as unsustainable as a consequence of depletion of supplies and the contribution of these fuels to climate change by GHG (greenhouse gas) emissions into the atmosphere. Microalgae indicate alternative renewable sustainable energy sources as they have a high potential for producing large amounts of biomass which in turn can be used for production of different third-generation biofuels at large scale. Microalgae transform the solar energy into the carbon storage products, leads to lipid accumulation, including TAG (triacylglycerols), which then can be transformed into biodiesel, bioethanol and biomethanol. This paper reviews the selection, production and accumulation of target bioenergy carrier's strains and their advantages as well as the technological development for oil, biodiesel, ethanol, methanol, biogas production and GHG mitigation. The feedstock of promising algal strain exhibits the suitable biofuel production. The current progress of hybrid-technologies (biomass production, wastewater treatment, GHG mitigation) for production of prime-products as biofuels offer atmospheric pollution control such as the reduction of GHG (CO2 fixation) coupling wastewater treatment with microalgae growth. The selection of efficient strain, microbial metabolism, cultivation systems, biomass production are key parameters of viable technology for microalgae-based biodiesel-production.

  • 35.
    Malmqvist, Tove
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Glaumann, Mauritz
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Scarpellini, Sabina
    CIRCE - Centre of Research for Energy Resources and Consumption - Polytechnic Centre, University of Zaragoza.
    Zabalza, Ignacio
    CIRCE - Centre of Research for Energy Resources and Consumption - Polytechnic Centre, University of Zaragoza.
    Aranda, Alfonso
    CIRCE - Centre of Research for Energy Resources and Consumption - Polytechnic Centre, University of Zaragoza.
    Llera, Eva
    CIRCE - Centre of Research for Energy Resources and Consumption - Polytechnic Centre, University of Zaragoza.
    Diaz, Sergio
    CIRCE - Centre of Research for Energy Resources and Consumption - Polytechnic Centre, University of Zaragoza.
    Life Cycle Assessment in Buildings: the ENSLIC simplified method and guidelines2011In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 36, no 4, p. 1900-1907Article in journal (Refereed)
    Abstract [en]

    The application of Life Cycle Assessment (LCA) in the building sector is scarce today. It has several causes. First of all, making a LCA evaluation of a whole building demands a specific tool to handle the large information needed. Further, this tool has to be adapted to the different decisions taken throughout the building life cycle. In a few countries such tools have been developed but they are exceptions. However, useful experience has been gained in these countries, which is a valuable source for developing guidelines for application in other countries. Since results of building’s LCA may contain abundant and complex information, a great challenge is to elaborate efficient ways for communication with users and clients.

    The simplified methodology and guidelines presented in this paper is a systematic approach guiding the user through the Life Cycle process - clarifying key issues which usually cause difficulty, such as the choice of the assessment tool, the definition of the system limits, the options for simplifying the process, etc. The guidelines have been developed in the framework of the “ENSLIC building project”, co-financed by the European Commission-Intelligent Energy for Europe Programme- and by 9 European Organisations including more than 15 LCA experts and architects.

  • 36.
    Malmqvist, Tove
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Glaumann, Mauritz
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Svenfelt, Åsa
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Carlson, Per-Olof
    Erlandsson, Martin
    Andersson, Johnny
    Wintzell, Helene
    Finnveden, Göran
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Lindholm, Torbjörn
    Malmstrom, Tor-Göran
    A Swedish environmental rating tool for buildings2011In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 36, no 4, p. 1893-1899Article in journal (Refereed)
    Abstract [en]

    In 2003, a joint effort between the Swedish government, a number of companies in the building and construction sectors, some municipalities, insurance companies and banks set a target that by 2009, all new buildings and 30% of existing Swedish buildings should be rated using a voluntary environmental rating tool. In a major research programme finished in 2008, a tool was developed to be used in this context. The tool covers three assessment areas: Energy, Indoor environment and Material & Chemicals. These areas are split into 11 aspects with one or a few indicators. Rating criteria are specified for each indicator, stipulating requirements for a rating Gold, Silver, Bronze and Rated. Indicator results can then be aggregated to aspect, area and a single raring for building level for enhanced result communication. The tool builds on previous experiences regarding environmental building rating tools and therefore includes some special characteristics which aim to tackle some of the criticism directed towards the first generation of such tools. At the time of writing, the first buildings have received official ratings and an independent stakeholder group is promoting broader implementation of the tool. (C) 2010 Elsevier Ltd. All rights reserved.

  • 37. Markovska, Natasa
    et al.
    Klemes, Jiri Jaromir
    Duic, Neven
    Guzovic, Zvonimir
    Mathiesen, Brian Vad
    Lund, Henrik
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes. Malardalen University (MDU), Sweden .
    Sustainable development of energy, water and environment systems2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 76, p. 1-3Article in journal (Refereed)
  • 38. Mendiburu, Andres Z.
    et al.
    Carvalho, Joao A., Jr.
    Zanzi, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Coronado, Christian R.
    Silveira, Jose L.
    Thermochemical equilibrium modeling of a biomass downdraft gasifier: Constrained and unconstrained non-stoichiometric models2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 71, p. 624-637Article in journal (Refereed)
    Abstract [en]

    The objective of this work is to develop a non-stoichiometric equilibrium model to study parameter effects in the gasification process of a feedstock in downdraft gasifiers. The non-stoichiometric equilibrium model is also known as the Gibbs free energy minimization method. Four models were developed and tested. First a pure non-stoichiometric equilibrium model called M1 was developed; then the methane content was constrained by correlating experimental data and generating the model M2. A kinetic constraint that determines the apparent gasification rate was considered for model M3 and finally the two aforementioned constraints were implemented together in model M4. Models M2 and M4 showed to be the more accurate among the four developed models with mean RMS (root mean square error) values of 1.25 each. Also the gasification of Brazilian Pinus elliottii in a downdraft gasifier with air as gasification agent was studied. The input parameters considered were: (a) equivalence ratio (0.28-035); (b) moisture content (5-20%); (c) gasification time (30-120 min) and carbon conversion efficiency (80-100%).

  • 39.
    Mentis, Dimitrios
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Karalis, George
    Zervos, Arthouros
    Howells, Mark
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Taliotis, Constantinos
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Bazilian, Morgan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Rogner, Holger
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. International Institute for Applied Systems Analysis, Austria .
    Desalination using renewable energy sources on the arid islands of South Aegean Sea2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 94, p. 262-272Article in journal (Refereed)
    Abstract [en]

    Water and energy supply are strongly interrelated and their efficient management is crucial for a sustainable future. Water and energy systems on several Greek islands face a number of pressing issues. Water supply is problematic as regards both to the water quality and quantity. There is significant lack of water on several islands and this is mainly dealt with tanker vessels which transport vast amounts of water from the mainland. At the same time island energy systems are congested and rely predominantly on fossil fuels, despite the abundant renewable energy potential. These issues may be addressed by combining desalination and renewable energy technologies. It is essential to analyse the feasibility of this possibility. This study focuses on developing a tool capable of designing and optimally sizing desalination and renewable energy units. Several parameters regarding an island's water demand and the desalination's energy requirements are taken into account as well as input data which concern technological performance, resource availability and economic data. The tool is applied on three islands in the South Aegean Sea, Patmos (large), Lipsoi (medium) and Thirasia (small). Results of the modelling exercise show that the water selling price ranges from 1.45 (sic)/m(3) for the large island, while the corresponding value is about 2.6 (sic)/m(3) for the small island, figures significantly lower than the current water cost (7-9 (sic)/m(3)).

  • 40. Mollersten, K.
    et al.
    Yan, Jinyue
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Westermark, Mats
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Potential and cost-effectiveness of CO2 reductions through energy measures in Swedish pulp and paper mills2003In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 28, no 7, p. 691-710Article in journal (Refereed)
    Abstract [en]

    Using the two criteria of potential CO2 reduction and Cost Of CO2 reduction, technical energy measures in Swedish pulp. and paper mills are investigated. Principal CO2-reducing measures analysed are: decreased specific energy utilisation, fuel switch, and CO2 capture and sequestration. Among the investigated measures, conventional technologies for electricity conservation and improved electrical conversion efficiency in existing systems for cogeneration of heat and power are identified as the most cost-effective alternatives that also have large CO2 reduction potentials. For commercially available technologies, the results indicate an accumulated reduction potential of up to 8 MtCO(2)/y (14% of the Swedish net emissions). If emerging technologies for black liquor gasification (BLG) with pre-combustion CO2 capture and sequestration are considered, the CO2 reduction potential increases by up to 6 MtCO(2)/y (10% of the Swedish net emissions). Commercialised BLG, CO2 capture and reliable CO2 sequestration technologies are identified as important potential contributors to Swedish compliance with Kyoto Protocol targets, especially in a scenario of nuclear power closure.

  • 41.
    Morfeldt, Johannes
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Methodological differences behind energy statistics for steel production – implications when monitoring energy efficiency2014In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 77, no SI, p. 391-396Article in journal (Refereed)
    Abstract [en]

    Energy efficiency indicators used for evaluating industrial activities at the national level are often based on statistics reported in international databases. In the case of the Swedish iron and steel sector, energy consumption statistics published by Odyssee, Eurostat, the IEA (International Energy Agency), and the United Nations differ, resulting in diverging energy efficiency indicators. For certain years, the specific energy consumption for steel is twice as high if based on Odyssee statistics instead of statistics from the IEA. The analysis revealed that the assumptions behind the allocation of coal and coke used in blast furnaces as energy consumption or energy transformation are the major cause for these differences. Furthermore, the differences are also related to errors in the statistical data resulting from two different surveys that support the data. The allocation of coal and coke has implications when promoting resource as well as energy efficiency at the systems level. Eurostat's definition of energy consumption is more robust compared to the definitions proposed by other organisations. Nevertheless, additional data and improved energy efficiency indicators are needed to fully monitor the iron and steel sector's energy system and promote improvements towards a greener economy at large.

  • 42.
    Nerini, Francesco Fuso
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Broad, Oliver
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Mentis, Dimitris
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Welsch, Manuel
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Bazilian, Morgan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Howells, Mark
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    A cost comparison of technology approaches for improving access to electricity services2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 95, p. 255-265Article in journal (Refereed)
    Abstract [en]

    The UN's Sustainable Energy For All initiative has made universal access to energy by 2030 a key target. Countries wherein budgets are constrained and institutions stressed are faced with the challenge of further extending energy services and doing so significantly. To meet this goal for the power sector in a cost-effective way, governments have to consider the deployment of a mix of stand-alone, mini-grid and grid-based solutions. To help inform analysis, planning and the decision process, this paper presents a simple, transparent, least-cost model for the electrification of rural areas. The approach builds on four key parameters, namely: (i) target level and quality of energy access, (ii) population density, (iii) local grid connection characteristics and (iv) local energy resources availability and technology cost. From an application perspective, this work can be used both for (1) fast assessments of specific energy access projects, and (2) to inform more complex regional studies using a geo-referencing software to analyze the results. Such applications are presented in the results using country case studies developed for Nigeria and Ethiopia. These show how the strategy for expanding energy access may vary significantly both between and within given regions of energy-poor countries.

  • 43.
    Persson, Henry
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Han, Tong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Xia, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Evangelopoulos, Panagiotis
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Weihong, Yang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fractionation of liquid products from pyrolysis of lignocellulosic biomass by stepwise thermal treatment2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 154, p. 346-351Article in journal (Refereed)
    Abstract [en]

    The thermal properties of cellulose, hemicellulose and lignin can be utilized to improve the characteristics of pyrolysis liquids. In this study, a concept of stepwise pyrolysis to fractionate the liquid based on the thermal properties of the biomass constituents was investigated. Lignocellulosic biomass was thermally treated in two steps: 200–300 °C followed by 550 °C. Derived liquids were studied for GC/MS analysis, water content, acid concentration and a solvent extraction method. Pyrolytic liquid derived from 550 °C after treatment at lower temperatures have a higher relative composition of phenolic compounds compared to one-step pyrolysis (increased from 58 to 90% of GC/MS peak area). Also, compounds known to promote aging, such as acids and carbonyl compounds, are derived at lower temperatures which may suppress aging in the liquid derived downstream at 550 °C. For liquids derived at 550 °C, the total acid number was reduced from 125 in one-step treatment to 14 in two-step treatment. Overall, no significant difference in the total liquid yield (sum of the liquids derived in separated treatments) nor any variations in their collective composition compared to one-step treatment at 550 °C was observed, i.e. stepwise pyrolysis can be utilized for direct fractionation of pyrolytic vapors.

  • 44.
    Ren, Guorui
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. Harbin Institute of Technology, Harbin, Heilongjiang, China.
    Wan, J.
    Liu, J.
    Yu, D.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Analysis of wind power intermittency based on historical wind power data2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 150, p. 482-492Article in journal (Refereed)
    Abstract [en]

    As wind power provides an increasingly larger share of electricity supply, the challenges caused by wind power intermittency have become more and more prominent. A better understanding of wind power intermittency would contribute to mitigate it effectively. In the present study, the definition of wind power intermittency is given firstly. Based on the definition, wind power intermittency is quantified by duty ratio of wind power ramp (DRWPR). This index provides system operators quantitative insights into wind power intermittency. Furthermore, some characteristics of wind power intermittency can be extracted by the index, such as the differences between wind speed intermittency and wind power intermittency, the differences of wind power intermittency between different scales and so on. The wind power intermittency of a Chinese wind farm is studied in detail based on the proposed index and historical data.

  • 45.
    Robèrt, Markus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Hultén, Per
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Frostell, Björn
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Biofuels in the energy transition beyond peak oil: A macroscopic study of energy demand in the Stockholm transport system 20302007In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 32, no 11, p. 2089-2098Article in journal (Refereed)
    Abstract [en]

    The objective of this study is to examine the potential for a full transition to domestically produced biofuels in the Stockholm County transport system in 2030, without exceeding the proportional share of national bioenergy assets. This target is chosen in order to test the potential of biofuel assets in Sweden, facilitating the transition to renewable fuel systems, and to display the potential of transport energy demand at macrolevel under tighter conditions on the energy market after fossil oil production has peaked. The distribution of bioenergy to the transport sector, including conversion losses and relationships to other energy sectors, is analysed explicitly. State-of-the-art traffic forecasting models, complemented with a specially designed energy quantification model, are applied to assess energy quantities needed at different vehicle efficiency levels and mobility patterns. The purpose is not to determine the most energy-efficient transport system possible, or to forecast the optimal distribution of bioenergy set aside for the transport sector in the future. Rather, we try to visualise, at a more conceptual level, energy demand as dependent on principle transport strategies, future technological developments and a type of planning that takes technological interlinkages between evolving components into strategic account. This work highlights the importance of implementing both demand and supply-side policies in order to reduce energy use and greenhouse gas emissions in all energy sectors before making assessments of reasonable distributions of bioenergy between energy sectors and other biomass usage.

  • 46.
    Rydstrand, Magnus
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Westermark, Mats O.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Bartlett, Michael
    KTH, Superseded Departments, Chemical Engineering and Technology.
    An analysis of the efficiency and economy of humidified gas turbines in district heating applications2004In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 29, no 15-dec, p. 1945-1961Article in journal (Refereed)
    Abstract [en]

    In this article, the performance of gas turbine cycles operating with air/water working fluids, so-called humidified cycles, are examined in district heating applications. The investigated cycles are based on a GTX100 core from ALSTOM Power Sweden AB (ALSTOM)(1) and utilise a two-stage flue gas condenser and an inlet air humidifier (pre-humidifier) to provide elevated quantities of district heating. Simulations have shown that electrical efficiencies up to 50% and total efficiencies above 100% can be reached calculated on the lower heating value (LHV) of the fuel. Based on cost data from ALSTOM, humidified cycles have a potential to give much lower (40% per kW(el) and 60% per kW(DH)) specific investment costs compared to combined cycles, mainly due to the absence of steam turbine. The humidified cycles are predicted to be cost-effective investments at market electricity prices Euro5-8/MWh(el) lower than the conventional alternatives in district heating applications.

  • 47.
    Saxe, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Advantages of integration with industry for electrolytic hydrogen production2007In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 32, no 1, p. 42-50Article in journal (Refereed)
    Abstract [en]

    This paper evaluates possible synergies with industry, such as heat and oxygen recovery from the hydrogen production. The hydrogen production technology used in this paper is electrolysis and the calculations include the cost and energy savings for integrated hydrogen production. Electrolysis with heat recovery leads to both cost reduction and higher total energy efficiencies of the hydrogen production. Today about 15–30% of the energy supplied for the production is lost and most of it can be recovered as heat. Utilization of the oxygen produced in electrolysis gives further advantages. The integration potential has been evaluated for a pulp and paper industry and the Swedish energy system, focusing on hydrogen for the transportation sector. The calculated example shows that the use of the by-product oxygen and heat greatly affects the possibility to sell hydrogen produced from electrolysis in Sweden. Most of the energy losses are recovered in the example; even gains in energy for not having to produce oxygen with cryogenic air separation are shown. When considering cost, the oxygen income is the most beneficial but when considering energy efficiency, the heat recovery stands for the greater part.

  • 48.
    Saxe, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Folkesson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Energy system analysis of the fuel cell buses operated in the project: Clean Urban Transport for Europe2008In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 33, no 5, p. 689-711Article in journal (Refereed)
    Abstract [en]

    During the project Clean Urban Transport for Europe (CUTE), which ended in May 2006, 27 fuel cell buses were operated in nine European cities. In this paper key performance parameters from the operation of the fuel cell buses in the project are reported, the energy system of the bus is analysed and drive cycle tests in five cities are presented and analysed. The focus of the paper is on fuel consumption and optimisation potential but experiences of, and recommendations for, evaluation in large demonstration projects are also presented. The results show that although the total fuel cell system efficiency was found to be high (36–41%), the fuel consumption was higher for the fuel cell buses than for diesel buses. Since the CUTE buses were a pre-commercial generation of fuel cell buses, with standard auxiliaries and extensive reliability measures, large fuel consumption reduction is possible. Suggestions on how to increase the efficiency is presented in this paper. Minimising the reliability measures would decrease fuel consumption by about 20% and lowering the weight by 2 tonnes would decrease fuel consumption by another 10%. Hybridisation in combination with using electrical auxiliaries could save an additional 5–10% or more.

  • 49.
    Scharff, Richard
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Approaching wind power forecast deviations with internal ex-ante self-balancing2013In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 57, p. 106-115Article in journal (Refereed)
    Abstract [en]

    Short-term variations in wind power generation make real-time balancing of load and generation a more challenging task for the Transmission System Operator (TSO). One issue of interest that could facilitate the efficient integration of wind power is to shift larger parts of the balancing responsibility from the TSO to the power generating companies. The idea is to reduce the real-time balancing need for the TSO by demanding power generating companies to minimise their expected imbalances. To comply with this, power generating companies can re-schedule their production based on updated production forecasts. As a key of the contribution, this paper analyses internal ex-ante self-balancing, where this re-scheduling is done shortly before the period of delivery and internally within each power generating company. To quantify the value of such a more distributed balancing responsibility, a model has been developed which consists of a sequence of optimisation models. Then, possible trading decisions of power generating companies are evaluated in different situations. This is based on a hydro-thermal generation portfolio within the framework of the Nordic electricity market.

  • 50.
    Semlitsch, Bernhard
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Flow phenomena leading to surge in a centrifugal compressor2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 103, p. 572-587Article in journal (Refereed)
    Abstract [en]

    Surge is a global flow instability occurring in centrifugal compressors at low mass-flow rate operation. Due to its violent nature, it is the limiting factor for operability. To enhance the operating range, understanding of the flow instability inception when approaching surge is essential. Therefore, the flow evolution along a speed line is analysed by performing unsteady, three-dimensional flow simulations using a centrifugal compressor geometry with ported shroud. A stable operating condition, at high mass-flow rates, is compared to lower mass-flow rate operating conditions close to and at surge. The particularities of the flow-fields are analysed and described. A smooth flow-field is observed for the stable operating condition, whereas flow reversal manifesting as tip leakage at the outer periphery of the impeller occurs for all off-design operating conditions. The reversed flow exhibits swirling motion in the impeller rotation direction. This induces a globally swirling flow upstream of the impeller, which influences the flow incidence angles at the blades and hence, their efficiency. Proper orthogonal decomposition and dynamic mode decomposition have been performed to analyse the flow structures appearing with surge more thoroughly. For the lowest mass-flow rate operating condition, low frequency modes describing the filling and emptying processes during surge have been found.

12 1 - 50 of 67
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