1. A multi-objective solution of green vehicle routing problemÖzgür Kabadurmuş, Mehmet Serdar Erdoğan, Yiğitcan Özkan, Mertcan Köseoğlu, 2019, original scientific article Abstract: Distribution is one of the major sources of carbon emissions and this issue has been addressed by Green Vehicle Routing Problem (GVRP). This problem aims to fulfill the demand of a set of customers using a homogeneous fleet of Alternative Fuel Vehicles (AFV) originating from a single depot. The problem also includes a set of Alternative Fuel Stations (AFS) that can serve the AFVs. Since AFVs started to operate very recently, Alternative Fuel Stations servicing them are very few. Therefore, the driving span of the AFVs is very limited. This makes the routing decisions of AFVs more difficult. In this study, we formulated a multi-objective optimization model of Green Vehicle Routing Problem with two conflicting objective functions. While the first objective of our GVRP formulation aims to minimize total CO2 emission, which is proportional to the distance, the second aims to minimize the maximum traveling time of all routes. To solve this multi-objective problem, we used �-constraint method, a multi-objective optimization technique, and found the Pareto optimal solutions. The problem is formulated as a Mixed-Integer Linear Programming (MILP) model in IBM OPL CPLEX. To test our proposed method, we generated two hypothetical but realistic distribution cases in Izmir, Turkey. The first case study focuses on an inner-city distribution in Izmir, and the second case study involves a regional distribution in the Aegean Region of Turkey. We presented the Pareto optimal solutions and showed that there is a tradeoff between the maximum distribution time and carbon emissions. The results showed that routes become shorter, the number of generated routes (and therefore, vehicles) increases and vehicles visit a lower number of fuel stations as the maximum traveling time decreases. We also showed that as maximum traveling time decreases, the solution time significantly decreases.
Keywords: green vehicle routing problem, alternative fuel vehicles, epsilon-constraint, multi-objective optimization, Pareto optimality
Published in DKUM: 22.08.2024; Views: 44; Downloads: 8
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2. Methodology for estimating the effect of traffic flow management on fuel consumption and CO2 production : a case study of Celje, SloveniaBorut Jereb, Ondrej Stopka, Tomáš Skrúcaný, 2021, original scientific article Abstract: The manuscript discusses the investigation of vehicle flow in a predesignated junction byan appropriate traffic flow management with an effort to minimize fuel consumption, the productionof CO2, an essential greenhouse gas (hereinafter referred to as GHG), and related transport costs.The particular research study was undertaken in a frequented junction in the city of Celje, located in the eastern part of Slovenia. The results obtained summarize data on consumed fuel and produced CO2 amounts depending on the type of vehicle, traffic flow mixture, traffic light signal plan, andactual vehicle velocity. These values were calculated separately for three different conditions of traffic flow management. Amounts of fuel consumed were experimentally investigated in real traffic situations, whereas CO2 production was calculated by applying the actual European standardentitled EN 16258:2012 associated with a guideline for measuring emission values, as well as by examining specific traffic flow parameters. The key objective of the manuscript is to present multiple scenarios towards striving to minimize environmental impacts and improve transport operation's economic consequences when implementing proper traffic flow management. As for crucial findings, we quantified fuel consumption and CO2 emissions based on real data on the number and type of vehicles crossing the examined intersection and traffic light switching intervals. The results show that most of the CO2 was produced while waiting and in the accelerating phase in front of traffic lights, whereby in the running phase through the intersection, significantly less fuel was used. This study represents a mosaic fragment of research addressing endeavors to reduce CO2 production in urban transport. Following the experiments conducted, we can see a notable contribution towards reducing CO2 production with known and tested interventions in the existing transport infrastructure. A procedure embracing individual research steps may be deemed as an approach methodology dealing with traffic flow management with an aim to decrease the environmental and economic impacts oftraffic and transport operation; this is where the novelty of the research lies.
Keywords: traffic flow management, urban transport, CO2 production, greenhouse gas, fuel consumption, methodology, logistics, crossroads
Published in DKUM: 19.08.2024; Views: 82; Downloads: 9
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3. Comparative analysis of direct operating costs: Conventional vs. hydrogen fuel cell 19-seat aircraftMaršenka Marksel, Anita Prapotnik Brdnik, 2023, original scientific article Abstract: In this paper, a comparative analysis of direct operating costs between a 19-seat conventional and hydrogen-powered fuel cell aircraft is performed by developing a model to estimate direct operating costs and considering the evolution of costs over time from 2030 to 2050. However, due to the technology being in its early stages of development and implementation, there are still considerable uncertainties surrounding the direct operating costs of hydrogen aircraft. To address this, the study considers high and low kerosene growth rates and optimistic and pessimistic development scenarios for hydrogen fuel cell aircraft, while also considering the evolution of costs over time. The comparative analysis uses real flight and aircraft data for the airliner Trade Air. The results show that the use of 19-seat hydrogen fuel cell aircraft for air transportation is a viable option when compared to conventional aircraft. Additionally, the study suggests potential policies and other measures that could accelerate the adoption of hydrogen fuel cell technology by considering their direct operating costs.
Keywords: fuel cell aircrafts, direct operating cost of aircraft, 19-seat aircraft
Published in DKUM: 15.04.2024; Views: 172; Downloads: 16
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4. Efficiency of neat and quaternized-cellulose nanofibril fillers in chitosan membranes for direct ethanol fuel cellsMaša Hren, Damjan Makuc, Janez Plavec, Michaela Roschger, Viktor Hacker, Boštjan Genorio, Mojca Božič, Selestina Gorgieva, 2023, original scientific article Keywords: chitosan, cellulose nanofibrils, anion exchange membrane, direct alkaline alcohol fuel cells
Published in DKUM: 10.04.2024; Views: 222; Downloads: 15
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5. The Evaluation of Torrefaction Efficiency for Lignocellulosic Materials Combined with Mixed Solid WastesMaja Ivanovski, Darko Goričanec, Danijela Urbancl, 2023, original scientific article Abstract: The paper presents the results of research aimed at evaluating the possibility of using selected biomass wastes to produce solid biofuels. In this work, the thermochemical properties of two lignocellulosic biomasses, namely, miscantshus (Miscanthus × Giganteus) and hops (Humulus lupulus), and non-lignocellulosic biomass, namely, municipal solid waste, and their mixtures (micanthus + municipal solid waste and hops + municipal solid waste) were studied using the torrefaction process as the main method for investigation. The effects of various torrefaction temperatures (250, 300, and 350 °C) and times (30 and 60 min) were evaluated. Proximate and ultimate analyses were performed on the torrefied samples. The following can be stated: as the torrefaction temperature and time increased, mass and energy yields decreased while the higher heating values (HHVs) and fuel ratios (FRs) increased, together with carbon contents (C). In addition, energy on return investment (EROI) was studied; the maximum EROI of 28 was achieved for MSW biochar at 250 °C for 30 min. The results of studying greenhouse gas emissions (GHGs) showed a reduction of around 88% when using torrefied biochar as a substitute for coal. In sum, this study shows that torrefaction pre-treatment can improve the physicochemical properties of raw biomasses to a level comparable with coal, and could be helpful in better understanding the conversion of those biomasses into a valuable, solid biofuel.
Keywords: torrefaction, waste biomass, renewable energy, fuel ratio, greenhouse gas emission, GHG
Published in DKUM: 29.03.2024; Views: 222; Downloads: 20
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6. Exploring the possibilities of adjusting gensets to NATO requirementsDejan Barešić, Željko Hederić, Miralem Hadžiselimović, 2019, original scientific article Abstract: Stationary and mobile gensets are used in the Armed Forces of the Republic of Croatia. In this research, priority was given to mobile gensets which have a variety of uses. In addition to being used in the Republic of Croatia, the mobile gensets are also used in international military operations in various modes of operation. Therefore, it is necessary to be very familiar with their characteristics and the possibility of adjusting them to NATO requirements. For the purpose of the adjustment, a test was performed on a P-B40.R1 genset. A model that simulates the genset behaviour with different tested fuels was developed. The investigated genset, together with some others, was introduced into the Armed Forces pursuant to the Product Quality Protocol that was in force during the 1990s. The Protocol did not cover all requirements and recommendations for the genset operation in an international military environment. Therefore, research was conducted, which has resulted in the adjustment of the equipment and in the harmonisation of the Product Quality Protocol with the ISO standard and NATO requirements. When adjusting the materiel, special emphasis is given to defining certain genset types that are able to use the modified F-34 kerosene-type fuel instead of diesel fuel. The F-34 fuel is obtained from kerosene used in aviation; this fuel can be easily obtained in international military operations where the tendency is to use the same type of fuel for airplanes, vehicles, and diesel engine equipment. When F-34 is used as the genset fuel, the quality of the generated electrical energy might be reduced. For the purpose of bringing the output characteristics of the generator within prescribed limits, simulations were performed both with and without the tuning of the regulation parameters.
Keywords: genset, F-34 fuel, regulator adjustment, simulations
Published in DKUM: 22.02.2024; Views: 227; Downloads: 18
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7. Analysis of combustible fractions in mixed municipal waste and packaging and calculation of energy valueIvana Tršelič, Simon Jerina, Sebastijan Seme, Janja Stergar, 2020, original scientific article Abstract: The present article analyses combustible fractions in mixed municipal waste and packaging and the calculation of energy value. Methods of thermal treatment of waste and methods of preparation of alternative fuels and classifications are presented and described. The article describes the method of analysis of caloric values with which we determined the energy values of individual fractions. For the research, we also used two thermal analyses, with which we considered individual fractions, thermogravimetric analysis, and differential dynamic calorimetry. The article presents the results of both thermal analyses, with which we observe the responses of individual types of plastics at different temperatures and the change in physical and chemical properties. The problem we have analysed in this article is mainly recyclable plastic that can no longer be reused due to various factors. The results of the structural analysis of household waste collection are also presented and described; on the basis of the analysis, the energy value of the container of mixed municipal waste and the reasonableness of waste reuse are recalculated.
Keywords: mixed municipal waste, mixed municipal packaging, combustible fractions, energy value, solid recovered fuel, TGA analysis
Published in DKUM: 04.12.2023; Views: 276; Downloads: 7
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8. Impacts of zero-emission powertrains based on hydrogen technologies in public transportNiko Natek, Boštjan Krajnc, 2020, original scientific article Abstract: This article reviews the development potentials and environmental impact of introducing category M3 vehicles (for passenger transport/buses) with fuel cell electric powertrains to an urban and inter-urban public transport service (PTS) to be operated in the Savinjsko-Šaleška region. The main focus is the demonstration of the PTS modelling and preliminary environmental impact assessment of the operation compared to conventional (modern) diesel-powered internal combustion engines.
Keywords: Hydrogen, Fuel Cell, Transport, Energy efficiency, Green-house gas emissions, Energy transition, Environment, Public transport service, Internal combustion Engine, CO2
Published in DKUM: 15.11.2023; Views: 415; Downloads: 6
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9. Black-out diesel engine operation modelling for the CHPP start-upDušan Strušnik, Marko Agrež, Jurij Avsec, 2022, published scientific conference contribution Abstract: Modelling power plants using real process data is crucial in determining the cost-effectiveness and flexibility of systems. The quality of the elaborated model is determined with the validation of the model, which can also give results for the operating regimes of the plant, which are not often used in practice. In this way, also the operation and responsiveness of power plants outside the range of planned operation are determined. The model simulates the operation of a diesel engine (DE) required to start a combined heat & power plant (CHPP) from a black-out or loss of the electrical power network supply. The model is made on the basis of data provided by the manufacturer and the measured DE data. The results of the model enable detailed insight into the characteristics of the DE behaviour at different operating regimes. The economic and ecological rationale ranges of operation of the DE can be determined from the characteristics of operation. The results of the model show that the DE operates with a 41.72% average efficiency, consumes from 0.114 kg/s of diesel fuel for its operation and up to 3.68 kg/s of air, the air ratio ranges from 2.2 to 2.5. DE develops shaft power up to 2170 kW.
Keywords: air-fuel equivalence ratio, black-out, diesel engine, thermal efficiency, shaft power
Published in DKUM: 27.10.2023; Views: 530; Downloads: 8
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