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  • 1.
    Adom, Philip Kofi
    et al.
    Department of Development Policy, School of Public Service and Governance, Ghana Institute of Management and Public Administration, Accra, Ghana.
    Amuakwa-Mensah, Franklin
    Environment for Development, University of Gothenburg, Sweden.
    Agradi, Mawunyo Prosper
    Department of Economics, University of Insubria, Varese, Italy.
    Nsabimana, Aimable
    Rwanda Polytechnic, Rwanda; Department of Economics, University of Rwanda, Rwanda.
    Energy poverty, development outcomes, and transition to green energy2021Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 178, s. 1337-1352Artikel i tidskrift (Refereegranskat)
  • 2.
    Antonopoulou, Io
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Spanopoulos, Athanasios
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, Athens, Greece.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Single cell oil and ethanol production by the oleaginous yeast Trichosporon fermentans utilizing dried sweet sorghum stalks2020Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, s. 1609-1617Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ability of the oleaginous yeast Trichosporon fermentans to efficiently produce lipids when cultivated in dried sweet sorghum was evaluated. First, lipid production was evaluated in synthetic media mimicking the composition of sweet sorghum stalks and optimized based on the nitrogen source and C: N ratio. Under optimum conditions, the lipid production reached 3.66 g/L with 21.91% w/w lipid content by using a mixture of sucrose, glucose and fructose and peptone at C: N ratio 160. Cultivation on pre-saccharified sweet sorghum stalks offered 1.97 g/L, while it was found that sweet sorghum stalks can support yeast growth and lipid production without the need for external nitrogen source addition. At an attempt to increase the carbon source concentration for optimizing lipid production, the Crabtree effect was observed in T. fermentans. To this end, the yeast was evaluated for its potential to produce ethanol under anaerobic conditions in synthetic media and sweet sorghum. The ethanol concentration at 100 g/L glucose was 40.31 g/L, while utilizing sweet sorghum by adding a distinct saccharification step and external nitrogen source offered ethanol concentration equal to 23.5 g/L. To the authors’ knowledge, this is the first time that the Crabtree effect is observed in T. fermentans.

  • 3.
    Baidar, Binaya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nicolle, Jonathan
    Institut de Recherche D’Hydro-Québec.
    Gandhi, Bhupendra K.
    Department of Mechanical and Industrial Engineering, Indian Institute of Technology.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Effects of runner change on the Winter-Kennedy flow measurement method: A numerical study2020Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 153, s. 975-984Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Winter-Kennedy (WK) method is a popular choice to estimate the relative flow rates, and thus the expected improvement in the efficiency of a low head turbine after its refurbishment. Runner refurbishment is a common way to improve the plant’s efficiency. However, a previous experiment on a model turbine reported deviations between the WK coefficients obtained from two different runners ‒ suggesting a deviation between the estimated and actual improvement in the efficiency. Without formal proof, the deviation was attributed to flow changes in the spiral casing. This paper presents a numerical investigation of the effects of a runner change on the WK method. For this purpose, unsteady Reynolds-averaged Navier-Stokes equations (URANS) simulations of a turbine model with two different runners were conducted. The runner’s impact on the average flow conditions upstream and its subsequent effect on the WK coefficients were studied. The study shows the dependence of the WK coefficients to the runner ‒ with a maximum deviation on the coefficient up to 0.7%. The larger deviations were observed in regions prone to strong secondary flow. Following a radial and circumferential sensitivity study, a suitable location to minimize the effects of runner change on the WK method is reported.

  • 4.
    Bakhtiari, Hamed
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Zhong, Jin
    University of Hong Kong, Hong Kong.
    Alvarez, Manuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Uncertainty modeling methods for risk-averse planning and operation of stand-alone renewable energy-based microgrids2022Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 199, s. 866-880Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The accuracy of models to capture the uncertainty of renewables significantly affects the planning and operation of renewable energy-based stand-alone (REB-SA) microgrids. This paper aims to first study different stochastic and deterministic models for renewables, then evaluate the performance of an REB-SA microgrid planning problem and provide qualitative and quantitative comparisons. A modified Metropolis-coupled Markov chain Monte Carlo simulation is considered for the first time in the planning of an REB-SA microgrid to predict the behavior of renewables with minimum iterations. The modified model is benchmarked against two prevalent models including the retrospective model with worst-case scenarios and the Monte Carlo simulation. The operations of three designed microgrids (by these three methods) are evaluated using the last three-year historical data of a city in northern Sweden including solar radiation, wind speed, the water flow of a river, and load consumption. The impacts of the considered methods on using PV panels and hydrogen systems are investigated. The results verify that the modified model decreases the risk of planning and operation of an REB-SA microgrid from the energy and power shortage viewpoints. Moreover, the designed microgrid with the modified model can cope with all possible scenarios from economic, technical, and environmental viewpoints.

  • 5.
    Chalima, Angelina
    et al.
    Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, Athens, Greece.
    Taxeidis, George
    Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, Athens, Greece.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, Athens, Greece.
    Optimization of the production of docosahexaenoic fatty acid by the heterotrophic microalga Crypthecodinium cohnii utilizing a dark fermentation effluent2020Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 152, s. 102-109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dark fermentation is an anaerobic digestion process of biowaste, used to produce hydrogen as a fuel, which however releases high amounts of polluting volatile fatty acids in the environment. In order for the process to become more competitive, the acids stream can be utilized through conversion to high added-value docosahexaenoic acid by the microalga Crypthecodinium cohnii. Docosahexaenoic acid is one of the two main omega-3 fatty acids, necessary for human nutrition. The purpose of this work was to optimize the production of omega-3 fatty acids by the cells, utilizing the organic content of a dark fermentation effluent. For that purpose, the effect of different fermentation conditions was examined, such as incubation temperature, nitrogen source and concentration, the addition of chemical modulators, as well as the feeding composition. The volatile fatty acid content of the effluent was totally depleted in a fed-batch culture of the microalga, while the cells accumulated DHA in a percentage of 35.6% of total lipids, when fed with yeast extract or 34.2% when fed with ammonium sulfate. Taking into consideration the economic feasibility of the culture conditions proposed it was concluded that the use of yeast extract could be substituted by the much economic ammonium sulfate.

  • 6.
    Gehlin, S.E.A.
    et al.
    The Swedish Association for HVAC Engineers, Stockholm, Sweden.
    Hellström, Göran
    Department of Mathematical Physics, Lund Technical University, Lund, Sweden.
    Nordell, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    The influence of the thermosiphon effect on the thermal response test2003Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 28, nr 14, s. 2239-2254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The issue of natural and forced groundwater movements, and its effect on the performance of ground heat exchangers is of great importance for the design and sizing of borehole thermal energy systems (BTESs). In Scandinavia groundwater filled boreholes in hard rock are commonly used. In such boreholes one or more intersecting fractures provide a path for groundwater flow between the borehole and the surrounding rock. An enhanced heat transport then occurs due to the induced convective water flow, driven by the volumetric expansion of heated water. Warm groundwater leaves through fractures in the upper part of the borehole while groundwater of ambient temperature enters the borehole through fractures at larger depths. This temperature driven flow is referred to as thermosiphon, and may cause considerable increase in the heat transport from groundwater filled boreholes. The thermosiphon effect is connected to thermal response tests, where the effective ground thermal conductivity is enhanced by this convective transport. Strong thermosiphon effects have frequently been observed in field measurements. The character of this effect is similar to that of artesian flow through boreholes.

  • 7. Gehlin, Signild
    et al.
    Hellström, Göran
    Influence on thermal response test by groundwater flow in vertical fractures in hard rock2003Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 28, nr 14, s. 2221-2238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper different approaches to groundwater flow and its effect in the vicinity of a borehole ground heat exchanger are discussed. The common assumption that groundwater flow in hard rock may be modelled as a homogeneous flow in a medium with an effective porosity is confronted and models for heat transfer due to groundwater flow in fractures and fracture zones are presented especially from a thermal response test point of view. The results indicate that groundwater flow in fractures even at relatively low specific flow rates may cause significantly enhanced heat transfer, although a continuum approach with the same basic assumptions would suggest otherwise.

  • 8.
    Gustafsson, Anna-Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Westerlund, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Heat extraction thermal response test in groundwater-filled borehole heat exchanger: Investigation of the borehole thermal resistance2011Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, nr 9, s. 2388-2394Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In groundwater-filled borehole heat exchangers (BHEs) convective flow influences the heat transfer in the borehole. During heat extraction thermal response tests (TRTs) the effect of the changing convective flow is more dominant than during heat injection tests. Water is heaviest around 4 °C and when exceeding this temperature during the test, the convective flow is stopped and restarted in the opposite direction resulting in a higher borehole thermal resistance during that time. Just before 0 °C the convective flow is the largest resulting in a much lower borehole thermal resistance. Finally, during the freezing period phase change energy is released and material parameters change as water is transformed into ice, resulting in a slightly higher borehole resistance than at a borehole water temperature of 0 °C. The changes in borehole thermal resistance are too large for ordinary analysis methods of thermal response tests to work. Instead another method is introduced where the borehole thermal resistance is allowed to change between different time intervals. A simple 1D model of the borehole is used, which is matched to give a similar mean fluid temperature curve as the measured one while keeping the bedrock thermal conductivity constant during the whole test. This method is more time-consuming than ordinary TRT analyses but gives a good result in showing how the borehole thermal resistance changes. Also, a CFD-model with a section of a simplified borehole was used to further study the effect of convection and phase change while the temperature was decreased below freezing point. The test and the model show similar results with large variations in the borehole thermal resistance. If the knowledge of changing borehole thermal resistance was used together with a design program including the heat pump and its efficiency, a better BHE system design would be possible.

  • 9.
    Gustafsson, Anna-Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Westerlund, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Multi-injection rate thermal response test in groundwater filled borehole heat exchanger2010Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 35, nr 5, s. 1061-1070Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During a thermal response test (TRT) or during operation of a borehole heat exchanger (BHE) system, a temperature gradient in and around the borehole is achieved. This causes convective flow in the groundwater due to density differences. In groundwater filled BHE the convective heat flow influences the heat transport in the borehole system. The size of the influence depends on the injection rate used, which changes during the year for normal BHE systems. Multi-injection rate TRT (MIR TRT) may be used as a method to detect the convective heat influence and to examine the effect on the BHE thermal transport parameters. It was shown that MIR TRT constitutes a valuable method to detect fractured bedrock and to examine the effect of different heat injection rates. For boreholes located in solid bedrock only the borehole thermal resistance was influenced by the convective flow. An increase in heat injection rate resulted in a decrease in resistance. It was shown that the length of the collector did not affect the result. For the fractured bedrock the effective bedrock conductivity was also affected, an increase in heat injection rate resulted in a higher effective bedrock thermal conductivity.

  • 10.
    Jafarzadeh Juposhti, Hessan
    et al.
    Faculty of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran.
    Maddahian, Reza
    Faculty of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Optimization of axial water injection to mitigate the Rotating Vortex Rope in a Francis turbine2021Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 75, s. 214-231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rotating Vortex Rope (RVR) resulting from flow instabilities inside draft tube affects the hydraulic turbine's efficiency and wear. Among the passive and active RVR mitigation methods, the water injection method has been widely investigated lately. The present research focuses on the dynamics of RVR mitigation using the water injection method and the optimization of exergy loss during the water injection. The numerical simulations are performed using a reduced turbine geometry consisting of one stay vane, two guide vanes, one runner passage by applying periodic boundary conditions at side boundaries, and a complete draft tube. The pressure fluctuations, velocity field, and the RVR structure are well captured using the Shear Stress Transport - Scale Adaptive Simulation (SST-SAS) turbulence model. The results of the local swirl number during the load variation show that the onset of flow instabilities and RVR formation are created due to a decrease of the axial momentum below the runner cone. The required axial momentum flux of water injection is calculated for a stable swirl number and the local minimum ratio of dimensionless loss to the pressure recovery factor. The numerical results show that the rotating and plunging components of the pressure fluctuations inside the draft tube reduce during the water injection. The pressure recovery of the draft tube improves. The dynamics of RVR mitigation are visualized using λ2 criterion and the spectrogram of pressure probes on the draft tube wall. An optimum water flow rate and jet velocity for a fixed axial momentum are proposed. The results show that a water jet with a large radius and low velocity is more effective to mitigate the RVR and minimizing the draft tube losses.

  • 11.
    Joy, Jesline
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Raisee, Mehrdad
    Hydraulic Machinery Research Institute, School of Mechanical Engineering, University of Tehran, Tehran, 1417935840, Iran.
    Cervantes, Michel J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Experimental investigation of an adjustable guide vane system in a Francis turbine draft tube at part load operation2023Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 210, s. 737-750Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydraulic turbines are increasingly used to regulate the electrical grid. They thus have to operate more often at off-design conditions where instabilities may develop leading to large pressure pulsations decreasing the life of the machines. In the present study, an adjustable guide vane system in the draft tube of a single regulated hydraulic turbine is developed. The aim is to mitigate the pressure pulsations when the turbine operates at part load operational regimes without significantly compromising the hydraulic efficiency of the turbine. The draft tube guide vane system, named DTGV, is composed of three guide vanes. Each guide vanes comprise two individual hydrofoils. The upper hydrofoil can rotate around an axis up to ±45°, and the lower is fixed. Therefore, the guide vanes are adjustable. The rotating vortex rope mitigation was investigated at two part-load operational regimes at a 12 m turbine head, a) Q/QBEP = 0.59, and b) Q/QBEP = 0.71. The results indicate that the DTGV system significantly mitigates the pressure pulsations, thereby improving the flexible operation of the turbine. The best mitigation outcome was for 0 GV configuration at both part-load operating conditions. The mitigation effects are better when the operating condition approaches BEP, and the rotating mode of the pressure pulsations tends to go towards the runner frequency (f/f0 = 1). The hydraulic efficiency is found to be marginally affected by the guide vane system at part load operations and is improved at the best efficiency point (Q/QBEP = 1) and high load Q/QBEP = 1.21.

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  • 12.
    Kharseh, Mohamad
    et al.
    Qatar University, Mechanical & Industrial Engineering Department, Doha.
    Altorkmany, Lobna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Al-Khawaja, Mohammed
    Qatar University, Mechanical & Industrial Engineering Department, Doha.
    Hassani, Ferri
    Department of Mining Metals and Materials Engineering, McGill University, H3A 2A7, Montreal.
    Analysis of the effect of global climate change on ground source heat pump systems in different climate categories2015Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 78, s. 219-225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ground source heat pump (GSHP) systems exhibit high thermal performance. Consequently, they are increasingly used to heat and cool buildings. The thermal performance of GSHP systems strongly depends on the operation ground temperature and thermal quality of the building envelope (TQBE). The operation ground temperature is a function of mean annual air temperature and annual thermal load of the building. The thermal load depends on the TQBE and outside temperature. Given that ongoing global climate change (GCC) affects air temperatures, it also affects the performance of GSHP systems. The magnitude of this impact on a given GSHP system strongly depends on local weather conditions and the TQBE.The overall aim of the current study is to investigate the impact of GCC on the performance of GSHP systems in different climate. To achieve this aim, three cities located in three climate categories were considered: Stockholm, Sweden (cold), Istanbul, Turkey (mild), and Doha, Qatar (hot). In each city, two buildings were modeled. One was built according to current local building regulations, while the other was built to have a TQBE lower than the standard TQBE. Simulations were run for present (2014) and future (projected for 2050) outdoor designing conditions.

  • 13.
    Kharseh, Mohamad
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Altorkmany, Lobna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Nordell, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Global warming’s impact on the performance of GSHP2011Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, nr 5, s. 1485-1491Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since heating and cooling systems of buildings consume 30e50% of the global energy consumption, increased efficiency of such systems means a considerable reduction in energy consumption. Ground source heat pumps (GSHP) are likely to play a central role in achieving this goal due to their high energy efficient performance. The efficiency of GSHP depends on the ground temperature, heating and cooling demands, and the distribution of heating and cooling over the year. However, all of these are affected by the ongoing climatic change. Consequently, global warming has direct effects on the GSHP performance.Within the framework of current study, heating and cooling demands of a reference building were calculated for different global warming scenarios in different climates i.e. cold, mild and hot climate. The prime energy required to drive the GSHP system is compared for each scenario and two configurations of ground heat exchangers. Current study shows that the ongoing climatic change has significant impact on GSHP systems.

  • 14.
    Liu, Hao
    et al.
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Li, Mi
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Zhao, Shuna
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Mensah, Rhoda Afriyie
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Das, Oisik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Jiang, Lin
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Xu, Qiang
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Insights into wood species and aging effects on pyrolysis characteristics and combustion model by multi kinetics methods and model constructions2023Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 206, s. 784-794Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Considering the extensive application of wood materials in the construction and manufacturing, waste wood has potential of converting into new natural energy sources. In this study, cypress, pine and fir woods commonly used in China, as well as old samples for above each species (more than 200 years old) have been used to study the aging and species effects on their thermal stability and combustion models. To obtain the kinetic triplets of the pyrolysis process, all samples have been heated in a nitrogen atmosphere with heating rates of 5, 10, 15, and 20 K min−1. The kinetics parameters of pyrolysis throughout the conversion process were then calculated using isoconversional method, Coats-Redfern (CR), and masterplots methods. The reconstructed theoretical models have been then adjusted using the accommodation functions. The results of this study contribute to an increased understanding of the fire mechanism of waste woods, and implications concerning to provide scientific theoretical guidance for its feasibility as a new energy fuel more efficiently.

  • 15.
    Mesfun, Sennai
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Sanchez, Daniel L.
    Carnegie Institution for Science, Department of Global Ecology.
    Leduc, Sylvain
    International Institute for Applied Systems Analysis (IIASA).
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Biberacher, Markus
    Research Studios Austria (RSA), Studio iSPACE.
    Kraxner, Florian
    International Institute for Applied Systems Analysis (IIASA).
    Power-to-gas and power-to-liquid for managing renewable electricity intermittency in the Alpine Region2017Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 107, s. 361-372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Large-scale deployment of renewable energy sources (RES) plays a central role in reducing CO2 emissions from energy supply systems, but intermittency from solar and wind technologies presents integration challenges. High temperature co-electrolysis of steam and CO2 in power-to-gas (PtG) and power-to-liquid (PtL) configurations could utilize excess intermittent electricity by converting it into chemical fuels. These can then be directly consumed in other sectors, such as transportation and heating, or used as power storage. Here, we investigate the impact of carbon policy and fossil fuel prices on the economic and engineering potential of PtG and PtL systems as storage for intermittent renewable electricity and as a source of low-carbon heating and transportation energy in the Alpine region. We employ a spatially and temporally explicit optimization approach of RES, PtG, PtL and fossil technologies in the electricity, heating, and transportation sectors, using the BeWhere model. Results indicate that large-scale deployment of PtG and PtL technologies for producing chemical fuels from excess intermittent electricity is feasible, particularly when incentivized by carbon prices. Depending on carbon and fossil fuel price, 0.15−15 million tonnes/year of captured CO2 can be used in the synthesis of the chemical fuels, displacing up to 11% of current fossil fuel use in transportation. By providing a physical link between the electricity, transportation, and heating sectors, PtG and PtL technologies can enable greater integration of RES into the energy supply chain globally.

  • 16.
    Mulenga, Enock
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kabanshi, Alan
    Department of Building Engineering, Energy Systems and Sustainability Science, University of Gävle, Kungsbäcksvagen 47, 801 76, Gävle, Sweden.
    Mupeta, Henry
    Department of Electrical Engineering, The Copperbelt University, Jambo Drive, Riverside, P.O. Box 21692, Kitwe, Zambia.
    Ndiaye, Musa
    Department of Electrical Engineering, The Copperbelt University, Jambo Drive, Riverside, P.O. Box 21692, Kitwe, Zambia.
    Nyirenda, Elvis
    ZESCO Limited, PO Box 33304, Lusaka, Zambia.
    Mulenga, Kabwe
    ZESCO Limited, PO Box 33304, Lusaka, Zambia.
    Techno-economic analysis of off-grid PV-Diesel power generation system for rural electrification: A case study of Chilubi district in Zambia2023Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 203, s. 601-611Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The study explores the techno-economic feasibility and viability of a Photovoltaic-Diesel Hybrid system for rural electrification in sub-Sahara Africa with a case study of Chilubi island, a remote district without access to electricity in the Northern Province of Zambia. Using HOMER (Hybrid Optimization of Multiple Electric Renewables) Pro software, the best and most feasible technical solutions through different hybrid system configurations, combinations and the district's rate of access to electricity were considered based on the least Levelized Cost of Energy (LCoE) and life cycle costs of the project. The results show that operating diesel generators as stand-alone is not economically sustainable and has a high LCoE. Influencing factors include variability in diesel pump prices, high fuel transportation costs, high cost of operation and maintenance, among other factors of concern. 100% photovoltaic (PV) with a battery system gave the lowest LCoE. However, the initial capital cost of solar energy projects in Zambia is relatively high compared to the equivalent diesel-based plants, as shown herein. It explains why diesel power plants are favoured for off-grid settlements. On the hand, the low operational cost and LCoE of PV power plants favour rural districts as they offset the high initial capital costs. Additionally, the continued downward trend in the cost of PV installations per kWp has opened discussions among policymakers and energy planners in Zambia to favour rural electrification with renewable energy-based power generation. This study contributes to this discussion.

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  • 17.
    Möllersten, Kenneth
    et al.
    Luleå tekniska universitet.
    Gao, Lin
    Luleå tekniska universitet.
    Yan, Jinyue
    Efficient energy systems with CO2 capture and storage from renewable biomass in pulp and paper mills2004Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 29, nr 9, s. 1583-1598Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the impact of combining CO2 capture and storage with alternative systems for biomass-based combined heat and power production (CHP) in Kraft pulp and paper mills. We compare heat, power, and CO2 balances of systems with alternative configurations of the CHP and CO2-capture systems. Because the captured CO2 comes from renewable biomass, the studied systems yield negative CO2 emissions. It is shown that pulp mills and integrated pulp and paper mills have the potential to become net exporters of biomass-based electricity while at the same time removing CO2 from the atmosphere on a net basis. The study shows that that the overall best CO2 abatement is achieved when CO2 capture is carried out within a biomass integrated gasifier with combined cycle where the syngas undergoes a CO-shift reaction. This configuration combines efficient energy conversion with a high CO2 capture efficiency. Furthermore, cost curves are constructed, which show how the cost of CO2 capture and storage in pulp and paper mills depends on system configuration and the CO2 transportation distance.

  • 18.
    Nwachukwu, Chinedu M
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Toffolo, Andrea
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Biomass-based gas use in Swedish iron and steel industry: Supply chain and process integration considerations2020Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, s. 2797-2811Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 19.
    Patel, Alok
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India.
    Pruthi, Vikas
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India;iofuel Laboratory, Centre for Transportation Systems, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India.
    Pruthi, Parul A.
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India.
    Innovative screening approach for the identification of triacylglycerol accumulating oleaginous strains2019Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 135, s. 936-944Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Currently, triacylglycerides (TAG) accumulation in the form of lipid droplets (LDs) in oleaginous microorganisms is of immense importance due to their ability to get transesterified into value-added products in the form of biodiesel. Hence, in order to search for oleaginous microorganisms having high lipid content among a wide range of samples from different niches, there is a compulsive need to develop simple, reliable and rapid methods for screening of TAG accumulating strains. Conventional methods require multistep processes for the isolation, cultivation, extraction and estimation of lipids to identify oleagenic strains. To overcome these challenges, we are proposing an easy, live cellimaging technique for the estimation of lipids via visualization of TAG accumulation in probable strains at the single cell level that gives real-time monitoring of intracellular lipid accumulation in yeasts. In this screening technique, only 100 μl of specific neutral lipid accumulating medium was used to grow the isolated culture in the microtiter plate. The harvested cells were stained with LipidTOX™ Green and visualized by a LED based digital inverted fluorescence microscope. Among 446 yeast colonies screened, maximum lipid producing yeast strains Rhodosporidium kratochvilovae HIMPA1 and Rhodotorula minuta,having supersized lipid body of 5.05 ± 0.87 μm and 4.46 ± 0.61 μm, respectively, were identified as potential candidates for biodiesel production. To the best of our knowledge, this is the first report of using LipidTOX™ Green for the staining of lipid droplets present in yeast cells as per the literature.

  • 20.
    Saadat, Nazmus
    et al.
    Centre for Biocomposites and Biomaterials Processing, Division of Forestry, Daniels Faculty of Architecture, Landscape and Design, University of Toronto, Toronto, Ontario, Canada.
    Dias, Otavio Titton
    Centre for Biocomposites and Biomaterials Processing, Division of Forestry, Daniels Faculty of Architecture, Landscape and Design, University of Toronto, Toronto, Ontario, Canada.
    Jaffer, Shaffiq
    Total NA, Hopkinton MA, USA.
    Tjong, Jimi
    Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada.
    Sain, Mohini
    Centre for Biocomposites and Biomaterials Processing, Division of Forestry, Daniels Faculty of Architecture, Landscape and Design, University of Toronto, Toronto, Ontario, Canada; Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada.
    Anisotropically layered 2D-3D biocarbon-carbon functionality in sustainable high-performance composite for bipolar plates in fuel cell2024Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 224, artikel-id 120155Artikel i tidskrift (Refereegranskat)
  • 21.
    Sartaj, Km
    et al.
    Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India.
    Patel, Alok
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Gunjyal, Neelam
    Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India.
    Prasad, Ramasare
    Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India.
    Photo-induced biomitigation of sewage wastewater by new isolate of Rhodotorula glutinis ISO A1–lipid augmentation and profiling2022Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 195, s. 742-754Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Development of efficient wastewater treatment technologies along with circular economic approaches are the most imperative biotechnological attention presently. Thus, to add more value in this process, current study accessed a novel oleaginous yeast strain, R. glutinis ISO A1 for its biodegrading potential in sewage wastewater encompassing toxic formulations. To achieve improved performance light irradiance of various intensities (50 lux–150 lux) was applied during the cultivation period as an abiotic stress factor. All irradiances significantly stimulated nutrient removal efficiency of R. glutinis and improved growth rate but intracellular accumulation of carotenoids was found slightly inhibited. Boosted lipogenesis (lipid content ⁓40.66%) along with phenomenal reduction in COD (88.33 ± 1.88%), nitrate (73.2 ± 3.95%) and phosphate (85.1 ± 2.97%) was monitored with an optimum exposure condition at 100 lux. Cultures illuminated with light (50 lux–150 lux) also showed excellent tolerance for multiple heavy metals (Zn, Cd, Cr) and exhibited their complete removal. Further, analysis of fatty acid methyl esters (FAME) presented an increase in saturated fatty acids that reveal modulations in R. glutinis's membrane fluidity against stress generated due to the light exposure. Besides, estimated biodiesel properties of obtained FAME complying European and American fuel standards. These findings shed new light on the factors affecting wastewater bioremediation and successfully established a photo-induced biological treatment system in an oleaginous yeast for the very first time with an addition to successive lipid enhancement.

  • 22.
    Shiraghaee, Shahab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sundström, Joel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Raisee, Mehrdad
    Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Cervantes, Michel J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation2024Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 225, artikel-id 120232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The implementation of hydropower to stabilize electrical grids dictates more frequent off-design operations of these renewable energy resources. Flow instabilities under such conditions reduce the efficiency of hydro turbines. Part-load operation is particularly detrimental since the development of a rotating vortical structure termed rotating vortex rope (RVR) in the draft tube leads to periodic pressure pulsations that jeopardize turbine performance. This paper experimentally explores a novel solution involving the protrusion of flat plates into the turbine draft tube. Three flat plates equally separated by 120° were vertically installed on the draft tube wall. The plates were protruded up to 83% of the draft tube local radius under four different part-load conditions. Their impact was observed through time-resolved pressure measurements in the draft tube and vaneless space, as well as efficiency measurements. The results demonstrated successful RVR mitigation, achieving a maximum 85% reduction in pressure oscillation amplitudes. Protruding flat plates disrupted RVR periodicity and coherence, confining its orbit to the draft tube center. This approach proved particularly effective at lower part-load conditions, enhancing turbine hydraulic efficiency by increasing torque extraction. Reducing the adverse effects under part load, the proposed method appears promising in extending the operational range of hydraulic turbines.

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  • 23.
    Sotoudeh, Nahale
    et al.
    Faculty of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran.
    Maddahian, Reza
    Faculty of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Investigation of Rotating Vortex Rope formation during load variation in a Francis turbine draft tube2020Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 151, s. 238-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rotating Vortex Rope (RVR) has been a matter of focus for years due to the major effects on hydraulic turbine’s efficiency. The exact procedure of RVR formation is still vague. The present research focuses on the dynamics of the RVR formation during the load variation employing transient numerical simulations. Two different geometries including the full geometry and the reduced one, which consists of one stay vane, two guide vanes, one runner blade, one splitter blade and full draft tube, are considered. In order to capture the transient swirling flow features inside the draft tube, the Shear Stress Transport-Scale Adaptive Simulation (SST-SAS) model is utilized to approximate the turbulent stresses. The pressure results inside the draft tube agree well with the experimental measurements. Moreover, the velocity results show the central low-axial-velocity and high-tangential-velocity region in the draft tube properly. The flow structure is visualized using λ2 criterion. The dynamic of RVR and the physics behind the RVR formation are investigated during the load variation. The results indicate four flow regimes with different characteristics during RVR formation. The first flow regime is a stable swirling structure occurring at Best Efficiency Point (BEP). The second flow regime occurs at the beginning of the load variation where signs of flow instabilities appear. These instabilities are temporary and washed down by the upstream flow. Expanding the instabilities and creating the vortical structures in the draft tube are the important flow features in the third flow regime. The fourth flow regime is the presence of a developed rotating rope occurring at the Part Load (PL) condition. The flow regimes differ according to the size and shape of the stalled region during load rejection inside the draft tube cone. They also reveal that despite some shortcomings, the reduced model is reliable to simulate the RVR transient formation. The full geometry simulations could be also applicable for practical problems provided that the modified time step is slightly greater than the main blade rotational angle is used.

  • 24.
    Svanberg, Martin
    et al.
    SSPA SWEDEN AB.
    Finnsgård, Christian
    SSPA SWEDEN AB.
    Flodén, Jonas
    Department of Business Administration, School of Business, Economics and Law, University of Gothenburg.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Analyzing animal waste-to-energy supply chains: The case of horse manure2018Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 129B, s. 830-837Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To reduce human impact upon the environment, a transition from fossil to renewable energy sources such as biomass is imperative. Biomass from animal waste such as horse manure has unutilized potential as it has yet to be implemented at a large scale as an energy source. Research has demonstrated the technical feasibility of using animal waste for energy conversion, though their supply chain cost poses a barrier, as does a gap in research regarding the specific design of efficient horse manure-to-energy supply chains. In response, we investigated the design of horse manure-to-energy supply chains through interviews and site visits at stables, as well as through interviews with transport companies. Our findings show that horse manure-to-energy supply chains have distinct attributes at all stages of the supply chain such as the geographical spread of stables that determines supply chain design and hampers efficiency. They share several such attributes with forest biomass-to-energy supply chains, from which important needs can be identified, including the industrial development of trucks dedicated to the purpose, mathematical modeling to handle the trade-off of cost of substance loss in storage and cost of transport, and business models that reconcile the conflicting goals of different actors along the supply chains.

  • 25.
    Söderholm, Patrik
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Samhällsvetenskap.
    Sundqvist, Thomas
    Swedish Competition Authority.
    Empirical challenges in the use of learning curves for assessing the economic prospects of renewable energy technologies2007Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 32, nr 15, s. 2559-2578Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In bottom-up energy models endogenous technical change is introduced by implementing technology learning rates, which specify the quantitative relationship between the cumulative experiences of the technology on the one hand and cost reductions on the other. The main purpose of this paper is to critically analyze the choice of modeling and estimation strategies in learning curve analyses of power generation costs. We identify and discuss a number of theoretical and econometric issues involved in the estimation of learning curves. These include the presence of omitted variable bias and simultaneity, but also methodological problems related to the operationalization of theoretical concepts (i.e., learning-by-doing) and the associated use of data. We illustrate the importance of these issues by employing panel data for wind power installations in four western European countries, which are used to compare the results from different learning curve model specifications. The results illustrate that the estimates of learning rates may differ significantly across different model specifications and econometric approaches. The paper ends by outlining a number of recommendations for energy model analysts, who need to select appropriate energy technology learning rates from the empirical literature, or who choose to perform the empirical work themselves.

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  • 26.
    Trivedi, Chirag
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gandhi, B.K.
    Indian Institute of Technology, Roorkee.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dahlhaug, O.G.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Experimental investigations of a model Francis turbine during shutdown at synchronous speed2015Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 83, s. 828-836Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydraulic turbines are widely used to meet the real-time electricity demand at moderate to low cost. Intermittency in the power grid due to high penetration of wind and solar power has raised significant concerns for grid stability and reliability. The intermittency results in an increase of the start–stop cycles of hydraulic turbines. Each cycle induces fatigue to the turbine runner because it experiences unsteady pressure loading of high amplitude. The turbine runner accelerates freely due to an instantaneous transition into no load during shutdown. The amplitude of the unsteady pressure pulsation increases as the runner accelerates. To investigate the unsteady pressure pulsation, a shutdown slightly different from the normal shutdown was performed. Guide vanes were closed completely before the generator was disconnected from the load. The runner was spinning at constant angular speed through the generator. Amplitudes of the pressure pulsations were 20% and 35% lower in the vaneless space and the runner, respectively, compared to the normal shutdown of the turbine.

  • 27.
    Trivedi, Chirag
    et al.
    Waterpower laboratory, NTNU – Norwegian university of science and technology, 7491 Trondheim, Norway.
    Iliev, Igor
    Waterpower laboratory, NTNU – Norwegian university of science and technology, 7491 Trondheim, Norway.
    Dahlhaug, Ole Gunnar
    Waterpower laboratory, NTNU – Norwegian university of science and technology, 7491 Trondheim, Norway.
    Markov, Zoran
    Faculty of Mechanical Engineering, Ss. Cyril and Methodius University, 1000 Skopje, Republic of North Macedonia.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. Vattenfall AB, Aurorum 12, 971 77 Luleå, Sweden.
    Lysaker, Henning
    Rainpower Norge AS, S. P. Andersens veg 7, 7031 Trondheim, Norway.
    Investigation of a Francis turbine during speed variation: Inception of cavitation2021Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 166, s. 147-162Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Variable-speed operation of a hydro turbine is considered as an alternative option to meet fluctuating energy demand as it allows high-ramping rate. Cavitation can be a limiting factor to utilize the variable-speed technology at fully capacity in a hydro power plant. This work investigates the cavitation characteristics and unsteady pressure fluctuations as turbine ramps up to meet the energy demand. The investigated Francis turbine consists of 15 blades and 15 splitters, and the reference diameter is 0.349 m. Numerical model of complete turbine is prepared and hexahedral mesh is created. Rayleigh Plesset Model is activated for cavitation modelling. Available experimental data of model acceptance test are used to prescribe boundary conditions, and to validate the numerical results at distinct points. Transient behaviour of the cavitation is studied, and the results are quite interesting. At certain time instants, the cavitation effect is extremely predominant, and as a result of cavitation bubble bursts, the amplitudes of pressure fluctuations are significantly high.

  • 28.
    Trubetskaya, Anna
    et al.
    School of Engineering and Ryan Institute, National University of Ireland Galway, Galway, Ireland.
    Souihi, Nabil
    Green Technologies and Environmental Economics Platform, Department of Chemistry, Umeå University, Umeå, Sweden.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Categorization of tars from fast pyrolysis of pure lignocellulosic compounds at high temperature2019Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 141, s. 751-759Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study presents how the yields of different tar compounds from pure lignocellulosic compounds respond to the change in temperature and residence time. Experiments were carried out with a drop tube furnace in the temperature range from 800 to 1250 °C. The tar composition was characterized by gas chromatography with a flame ionization detector and mass spectrometry using a dual detector system. Longer residence time and higher heat treatment temperatures increased the soot formation and decreased the tar yields. Soot yields from lignin samples were greater than soot yields from holocellulose pyrolysis. The dominating products in tars from pyrolysis of all lignocellulosic compounds were benzene and toluene. Cellulose and hemicellulose pyrolysis produced greater amount of oxygenates in tars, whereas lignin tar was rich in phenols, polycyclic hydrocarbons and naphthalenes. Simultaneous reduction of tar and soot was achieved by impregnation of lignin from wheat straw with alkali metals. The OPLS-DA model can accurately explain the differences in tar composition based on the experimental mass spectrometry data.

  • 29.
    Wei, Juntao
    et al.
    Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai.
    Gong, Yan
    Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai.
    Guo, Qinghua
    Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai.
    Chen, Xueli
    Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai.
    Ding, Lu
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Yu, Guangsuo
    Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai.
    A mechanism investigation of synergy behaviour variations during blended char co-gasification of biomass and different rank coals2018Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 131, s. 597-605Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Co-gasification reactivity of rice straw and bituminous coal/anthracite blended chars under CO2 atmosphere was evaluated using thermogravimetric analysis, and the influences of coal type and gasification temperature on synergy behaviour variations on co-gasification reactivity as carbon conversions increased were quantitatively studied. Furthermore, the chemical forms and concentrations of AAEM species at different co-gasification conversions were quantitatively analyzed for revealing co-gasification synergy mechanism. The results demonstrate that as conversions increased, synergy behaviour on co-gasification reactivity of rice straw-bituminous coal blends was shown as the weakened inhibition effect firstly and then the enhanced synergistic effect. Moreover, the inhibition effect on co-gasification reactivity of rice straw-bituminous coal blends was sustained up to higher conversion with the increment of gasification temperature. Differing from rice straw-bituminous coal blends, synergistic effect on co-gasification reactivity of rice straw-anthracite blends was obviously enhanced at early stage of co-gasification and started to slowly weaken after reaching the most significant synergistic effect at middle stage of co-gasification. Additionally, it was revealed that synergy behaviour variations on co-gasification reactivity of rice straw-bituminous coal blends were mainly attributed to the combination effects of active K and Ca transformation during co-gasification, while those of rice straw-anthracite blends indicated a good correlation with active K transformation during co-gasification.

  • 30.
    Wei, Maogui
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden. Guangxi University, College of Agronomy, 530005, Nanning, China.
    Xiong, Shaojun
    Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden.
    Chen, Feng
    Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden.
    Geladi, Paul
    Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden.
    Eilertsen, Lill
    Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden. Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, SE-901 83, Umeå, Sweden.
    Myronycheva, Olena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden.
    Lestander, Torbjörn A.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden.
    Thyrel, Mikael
    Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE901 83, Umeå, Sweden.
    Energy smart hot-air pasteurisation as effective as energy intense autoclaving for fungal preprocessing of lignocellulose feedstock for bioethanol fuel production2020Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 155, s. 237-247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study compared the effects of hot-air pasteurisation (HAP) at 75–100 °C versus autoclaving at 121 °C and 2 bar overpressure on the lignocellulosic degradation process of birch-based substrates that were used for shiitake mushroom cultivation and potential bioethanol production. Fifty substrate samples were obtained as a time series from different stages of the cultivation, and their chemical contents were measured by chemical analysis and near infra-red spectroscopy (NIR). Despite of different energy intensities, HAP and autoclaving did not result in significant differences in the degradation of lignin and carbohydrates. Major compositional changes were associated with the cultivation process. Principal component analysis on the wet chemical data and orthogonal projections to latent structures based on NIR spectra reached the same conclusion, namely that HAP had similar effect as autoclaving on compositional changes in the substrate during cultivation. The results of this study suggest that a substitution of autoclaving by HAP may potentially save up to 9.9 TWh energy for the global production of 7.5 million ton shiitake. At the same time, lignocellulose feedstock can be pretreated for the production of up to 3.24 million m3 of 95%-ethanol fuels, which can potentially substitute proximate 1.88 million m3 of regular gasoline.

  • 31.
    Zhong, Jin
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Department of Electrical & Electronic Engineering, The University of Hong Kong, Hong Kong.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Towards a 100% Renewable Energy Electricity Generation System in Sweden2021Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 171, s. 812-824Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Swedish government’s target is to have 100 per cent renewable electricity production by 2040. Currently, hydropower contributes the majority of renewable electricity generation of the country. The wind power capacity has increased significantly in the past decade. In this paper, practical data is used to study the possibility of reaching the 100% renewable electricity generation goal by replacing existing thermal generations with wind power generations. It is found that the Swedish electricity generation system can reach 100% renewable by tripling the existing wind power capacity combined with the existing hydropower in the country. Based on current growth rate of wind power installation, the goal could be reached within 20 years. Hourly simulation shows that 100 % renewable energy generation system composed by wind power and hydropower satisfy hourly operation requirements.

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