Comparative study of regulated and unregulated gaseous emissions during NEDC in a light-duty diesel engine fuelled with Fischer Tropsch and biodiesel fuels

In this study, regulated and unregulated gaseous emissions and fuel consumption with five different fuels were tested in a 4-cylinder, light-duty diesel EURO IV typically used for the automotive vehicles in Europe. Three different biodiesel fuels obtained from soybean oil, rapeseed oil and palm oil, a Fischer Tropsch fuel and an ultra low sulphur diesel were studied. The test used was the New European Driving Cycle (NEDC), this allowed tests to be carried out on an engine warmed up beforehand to avoid the effect of cold starts and several tests a day. Regulated emissions of NO_X, CO, HC and CO₂ were measured for each fuel. Unburned Hydrocarbon Speciation and formaldehyde were also measured in order to determine the maximum incremental reactivity (MIR) of the gaseous emissions. Pollutants were measured without the diesel oxidation catalyst (DOC) to gather data about raw emissions. When biodiesel was used, increases in regulated and unregulated emissions were observed and also significant increases in engine fuel consumption. The use of Fischer Tropsch fuel, however, caused lower regulated and unregulated emissions and fuel consumption than diesel.     

Optimizing site selection for hydrogen production in Iceland

While the world energy demand is steadily growing, the concern for the environmental aspects of energy use and natural resource exploitation has increased. A new market has emerged for renewable energy, often referred to as “green energy”. This paper presents an optimization model developed as part of a feasibility study on the idea of exporting renewable energy in the form of hydrogen, from Iceland to the continent of Europe.     

Hydrogen infrastructure design and optimization: A case study of China

Infrastructure issues pose more challenges and uncertainties for hydrogen than other alternative “fuels” such as biofuels and electricity. A key challenge of developing a future commercial hydrogen economy is how the infrastructure will be best designed and operated as time progresses, given that numerous technological options exist and are still in development for hydrogen production, storage, distribution and dispensing. This paper presents a generic optimization-based model for the strategic dynamic investment planning and design of future hydrogen supply chains. The features and capabilities of the model are illustrated through a detailed case study of China. It is shown how the proposed methodology can provide policy-makers with new tools for hydrogen development strategies.     

Modeling and parameters fitting of chemical and phase equilibria in reactive systems for biodiesel production

Biodiesel, a non-toxic biodegradable fuel from renewable sources such as vegetable oils, has been developed in order to reduce dependence on crude oil and enable sustainable development. The knowledge of phase equilibrium in systems containing compounds for biodiesel production is valuable, especially in the purification stage of the biodiesel. Nonetheless, the refining process of biodiesel and by-products can be difficult and can elevate the production costs considerably unless it has an appropriate knowledge about the phase separation behavior. In addition, the transesterification reaction yield for producing biodiesel depends upon several operation parameters e.g. the feed molar ratio oil-to-alcohol and the temperature. These parameters were analyzed through a thermodynamic analysis by direct Gibbs energy minimization method in this paper, with the purpose of calculating the chemical and phase equilibrium of some mixtures containing compounds found in biodiesel production. For this, optimization techniques associated with the GAMS^® 2.5 software were utilized and the UNIQUAC and NRTL models were applied to represent the non-idealities of the liquid phases. Also, binary interaction parameters of studied compounds were correlated for NRTL and UNIQUAC models by using the least squares principle. The results showed that the use of optimization techniques associated with the GAMS software are useful and efficient tools to calculate the chemical and phase equilibrium by minimizing the Gibbs energy. Moreover, a good agreement was observed in cases in which calculated data were compared with experimental data.     

Design of a future hydrogen supply chain: A multi period model for Turkey

There is no doubt that energy will have one of highest priorities in agendas of strategic plans of countries. Since fossil fuels are running out and carbon emissions are more important than ever, researchers seek alternative clean and efficient energy sources. One of the best alternatives is hydrogen. The systems in which hydrogen flows from its production to end users are called hydrogen supply chains (HSC). Since hydrogen is not in active use, its HSC infrastructure is not complete and should be planned very carefully. We study the design of HSC of Turkey to meet the hydrogen demand of the period between 2021 and 2050. Our aim is to minimize total cost of the HSC while meeting the demand of the transportation sector. We address the problem by using a mixed integer programming (MIP) model and derive several insights for the future HSC. The results show that while decentralization (being able to fulfill the demand from local production facilities) is 12% in the first period, this rate raises up to 48% by the end of the planning horizon. Analysis also reveal that almost all grids do not produce and import hydrogen simultaneously, i.e., they either produce or import hydrogen. The results are robust in the sense that solutions of different optimality gaps have minor differences in terms of established facilities.     

RDEA: A recursive DEA based algorithm for the optimal design of biomass supply chain networks

The optimal design of supply chain networks is often examined based on one or more economic or other criteria (e.g., cost, profit environmental impact, danger, time). However, the efficiency of the derived solutions is often ignored. In this work, a recursive DEA (RDEA) algorithm is presented, which introduces a different way of designing a supply chain network. The selection of possible installed facilities is based on minimum cost and maximum efficiency, through a MILP model. Optimal supply chain structure is obtained when the termination criterion is met, yielding only the efficient solutions, while simultaneously reducing the overall cost. An application of this RDEA algorithm to a biomass supply chain is examined. A comparative study is also presented, demonstrating the results obtained when solving the MILP without the proposed algorithm and with the use of an RDEA.     

Design of a future hydrogen supply chain: A multi-objective model for Turkey

One of the important alternatives to conventional fossil fuel vehicles in the transportation sector is hydrogen fuel cell vehicle (HFCV) technology. One of the most significant obstacles to the widespread use of these vehicles is the hydrogen supply chain network (HSC) infrastructure. In the design of this network, the harm caused by the network to the environment and the security risks that may arise are as important as the associated cost of building it. In this study, an HSC design that will minimize cost, carbon emission and security risk for Turkey is proposed. The problem is modeled using a mixed integer linear programming (MILP). Five different optimization cases are studied when the penetration rate of HFCV is 25%. In the first three cases, the objectives are independently optimized. The multi-objective optimization is addressed in Case 4 and Case 5. Case 4 is solved with epsilon constraint method by employing the results of the first three cases. The most balanced solution found is 88%, 10% and 2% away from the best cost, carbon emission and risk values, respectively. It is observed that the proposed solution has a decentralized network structure where steam methane reforming (SMR) and electrolysis (ELE) production plants are established. In Case 5, the weighted sum method (another multi-objective optimization method) is used and those which gave the closest results to that of the epsilon constraint method are chosen as the associated weights of three objectives. Using these weights, 10 different demand scenarios are studied. It is observed that the HSC has a decentralized structure under almost all demand scenarios.     

Geographic evaluation of trigeneration systems in the tertiary sector. Effect of climatic and electricity supply conditions

The development of trigeneration systems is especially important in the buildings sector, where the thermal loads are imposed by the needs of heating, domestic hot water, and cooling. A strong seasonal character is indicated, since the demands depend totally on local climatic conditions and vary considerably throughout the year. Geographic locations were chosen so as to represent the climatic variety in Spain: Canary Islands, Mediterranean Coast, Atlantic Coast, and different locations in the interior of the Iberian Peninsula. The solution of a mixed integer linear programming model (MILP) that incorporated local economic/environmental conditions determined the optimal configuration of the different energy supply plants as well as the optimal operation modes throughout an entire representative year. From an economic point of view, the optimal configuration for all localities included cogeneration modules. From an environmental point of view, the optimal solution was strongly dependent on the origin of the electricity supplied by the grid.     

Design of biomass processing network for biofuel production using an MILP model

This paper presents a general optimization model that enables the selection of fuel conversion technologies, capacities, biomass locations, and the logistics of transportation from the locations of forestry resources to the conversion sites and then to the final markets. A mixed integer linear programming (MILP) model has been formulated and implemented in a commercial software package (GAMS) using databases built in Excel. The MILP represents decisions regarding (1) the optimal number, locations, and sizes of various types of processing plants, (2) the amounts of biomass, intermediate products, and final products to be transported between the selected locations over a selected period, and maximizes the objective function of overall profit. The model has been tested based on an industry-representative data set that contains information on the existing wood resources, final product market locations and demands, and candidate locations and sizes for different types of processing plants, as well as the costs associated with the various processing units and transportation of materials, covering the Southeastern region of the United States. The model is applied to design both a distributed, and a more centralized, conversion system. The overall profits, values, cost, and supply network designs of both systems are analyzed using the optimization model. In particular, we investigate: 1) which parameters have major effect on the overall economics, and 2) the benefits of going to more distributed types of processing networks, in terms of the overall economics and the robustness to demand variations.     

Optimization and analysis of a hydrogen supply chain in terms of cost,CO2 emissions,and risk: the case of Turkey

The transportation sector, which is largely dependent on oil, is faced with many problems such as the danger of depletion of fossil fuels that are harmful to the environment. Moreover, the situations such as epidemics and war cause excessive fluctuations in oil prices. Therefore, there is a need for new solutions based on alternative energy sources for a sustainable transportation sector. Hydrogen fuel cell electric vehicles (HFCEV) are one of the significant alternatives for an efficient, zero emissions and sustainable transportation system. Considering the potential investment in HFCEV technology, the need for a cost effective, green, and low risk Hydrogen Supply Chain (HSC) network infrastructure is inevitable. In this study, the HSC design of the Turkish transportation sector over a 25-year period (2026–2050) is investigated. The problem is modeled using a multi-period mixed integer linear programming (MIP) model. Three objectives are addresses: cost, carbon dioxide (CO₂) emissions and safety risk. In order to consider the uncertainty in the hydrogen demand, five different scenarios are analyzed using fuzzy concept. There are four main results. First, unit hydrogen cost is found to be very high due to low demand and high capital cost in the initial period (2026–2031). Second, HSC network is established in a decentralized setting in all scenario solutions. The level of decentralization gets stronger over time and with increasing demand. Third, short-distance road transport is generally preferred for hydrogen transport. Fourth, since the aim is to minimize cost, CO₂ emissions, and risk level, a mixed production strategy based on cost-oriented SMR and zero-emissions-oriented Electrolysis (ELE) is observed in all scenarios.     

Combustion characteristics of biodiesel saturated with pyrolysis oil for power generation in gas turbines

There is a perceived need for multi-fuel burner geometries capable of operating with variable composition fuels from diverse sources to achieve fuel flexibility in gas turbines. The objective of the research covered herein is a comparison study between two liquid fuels, a biodiesel (in a pure form) and the biodiesel as a saturated mixture with a pyrolysis by-product; these two fuels were compared against a standard kerosene as a baseline. The research methodology involved two stages: firstly atomization patterns and injection regimes were obtained using a high speed imaging method, secondly a combustion test campaign was undertaken using a swirl burner to quantify the operational behaviour, species production and exhaust gas compositions of the fuels. Emissions, flame stability trends and power outputs were measured at gas turbine relevant equivalence ratios. Excess oxygen and atomization trends in the biodiesel seem to be playing a major role in the production of emissions and flame stability when compared to kerosene. Also, heavy organics seem to be acting as catalytic substances for OH production close to the burner mouth. In terms of stability and combustion, it is proposed that the saturated blend would be a viable candidate for power generation.     

Optimal transition towards a large-scale hydrogen infrastructure for the transport sector: The case for the Netherlands

A multi-period optimization framework based on a comprehensive techno-economic analysis is used to design spatially-explicit and time-evolutionary hydrogen (H₂) supply networks. It is of particular interest to investigate the spatio-temporal economic, environmental and energetic performance if H₂ were to be introduced as a fuel in the Dutch transport sector. A key observation is that the transition towards a large-scale H₂ supply infrastructure is economically viable, if designed optimally with a holistic long-term systems perspective. However, the well-to-tank (WtT) CO₂ emission reduction potential is limited (ca. 30%), which can be improved (ca. 85%) with carbon capture and storage (CCS). The spatially-explicit nature of the framework facilitates the design of efficient networks with a high network-wide WtT energy efficiency (ca. 50% or more). Furthermore, H₂ is observed to have the potential to alleviate Dutch energy security concerns. (Disclaimer: Results/comments are the authors’ and do not necessarily represent the views of the associated organizations/institutions).     

Location of a biomass based methanol production plant: A dynamic problem in northern Sweden

Concerning production and use of biofuels, mismatch between the locations of feedstock and the biofuel consumer may lead to high transportation costs and negative environmental impact. In order to minimize these consequences, it is important to locate the production plant at an appropriate location. In this paper, a case study of the county of Norrbotten in northern Sweden is presented with the purpose to illustrate how an optimization model could be used to assess a proper location for a biomass based methanol production plant. The production of lignocellulosic based methanol via gasification has been chosen, as methanol seems to be one promising alternative to replace fossil gasoline as an automotive fuel and Norrbotten has abundant resources of woody biomass. If methanol would be produced in a stand-alone production plant in the county, the cost for transportation of the feedstock as well as the produced methanol would have great impact on the final cost depending on where the methanol plant is located. Three different production plant sizes have been considered in the study, 100, 200 and 400 MW (biomass fuel input), respectively. When assessing a proper location for this kind of plant, it is important to also consider the future motor fuel demand as well as to identify a heat sink for the residual heat. In this study, four different automotive fuel- and district heating demand scenarios have been created until the year 2025. The results show that methanol can be produced at a maximum cost of 0.48 €/l without heat sales. By selling the residual heat as district heating, the methanol production cost per liter fuel may decrease by up to 10% when the plant is located close to an area with high annual heat demand.     

Optimal synthesis of trigeneration systems subject to environmental constraints

Environmental information obtained through Life Cycle Analysis techniques has been incorporated into a Mixed Integer Linear Programming (MILP). The solution of the model provides the optimal configuration and operation of an energy supply system to be installed, minimizing the environmental burden associated with production of equipment and consumption of resources. Starting from a superstructure of cogeneration system with additional components highly interconnected, the energy supply system was optimized considering specific demands of a hospital located in Zaragoza, Spain. The objective functions took into account the kilograms of CO₂ released and Eco-indicator 99 Single Score. Also considered were price of energy resources, price and amortization possibilities of the equipment and options for selling surplus electricity to the electric grid. The effect of electricity generation conditions on the optimal configuration was examined by varying the source of electricity production in Spain and considering natural gas/electricity mixes from alternate countries. The ratio between local electricity emissions and natural gas emissions (α factor) was found to have the highest impact on the configuration of the system. Therefore the α factor could be considered the strongest influencing factor when deciding the optimal configuration of a system that minimizes environmental loads.     

Oil assessment of Halamphora coffeaeformis diatom growing in a hybrid two-stage system for biodiesel production

The lipid content, composition and productivity of the marine benthic diatom Halamphora coffeaeformis were studied in order to evaluate its potential as feedstock for biodiesel production. Cultures were carried out in two stages: I) in photobioreactors (PBRs) to increase the biomass as inoculum for larger volumes, and II) in raceway ponds to increase naturally the triacylglycerol (TAG) content during the stationary growth phase. Biomass concentrations of 0.64 g L⁻¹ and 0.23 g L⁻¹ were reached in the PBR and the raceway pond, respectively. Total lipid content was 54.4 (±11.6) % ash free dry weight (AFDW) in the raceway pond on day 19 (harvest day), with a neutral lipid content of 34% AFDW. The TAG productivity in the raceway pond was 1.2 mg L⁻¹ d⁻¹. The indicators of biodiesel, calculated from fatty acid profile composition, showed that H. coffeaeformis oil was of good quality, according to international standards. Some hypothetical aspects are proposed in order to improve lipid productivity and net energy ratio in processes at larger scales.     

Performance evaluation of artificial neural network coupled with generic algorithm and response surface methodology in modeling and optimization of biodiesel production process parameters from shea tree (Vitellaria paradoxa) nut butter

This work investigated the potential of shea butter oil (SBO) as feedstock for synthesis of biodiesel. Due to high free fatty acid (FFA) of SBO used, response surface methodology (RSM) was employed to model and optimize the pretreatment step while its conversion to biodiesel was modeled and optimized using RSM and artificial neural network (ANN). The acid value of the SBO was reduced to 1.19 mg KOH/g with oil/methanol molar ratio of 3.3, H₂SO₄ of 0.15 v/v, time of 60 min and temperature of 45 °C. Optimum values predicted for the transesterification reaction by RSM were temperature of 90 °C, KOH of 0.6 w/v, oil/methanol molar ratio of 3.5, and time of 30 min with actual shea butter oil biodiesel (SBOB) yield of 99.65% (w/w). ANN combined with generic algorithm gave the optimal condition as temperature of 82 °C, KOH of 0.40 w/v, oil/methanol molar ratio of 2.62 and time of 30 min with actual SBOB yield of 99.94% (w/w). Coefficient of determination (R²) and absolute average deviation (AAD) of the models were 0.9923, 0.83% (RSM) and 0.9991, 0.15% (ANN), which demonstrated that ANN model was more efficient than RSM model. Properties of SBOB produced were within biodiesel standard specifications.     

Hydrogen rich gas production by the autothermal reforming of biodiesel (FAME) for utilization in the solid-oxide fuel cells: A thermodynamic analysis

The thermodynamics of the autothermal reforming (ATR) of biodiesel (FAME) for production of hydrogen is simulated and evaluated using Gibbs free minimization method. Simulations are performed with water-biodiesel molar feed ratios (WBFR) between 3 and 12, and oxygen-biodiesel molar feed ratio (O_XBFR) from 0 to 4.8 at reaction temperature between 300 and 800 °C at 1 atm. Yields of H₂ and CO are calculated as functions of WBFR, O_XBFR and temperature at 1 atm. Hydrogen rich gas can be produced by the ATR of biodiesel for utilization in solid-oxide fuel cells (SOFCs). The best operating conditions for the ATR reformer are WBFR≥9 and O_XBFR = 4.8 at 800 °C by optimization of the operating parameters. Yields of hydrogen and carbon monoxide are 68.80% and 91.66% with 54.14% and 39.2% selectivities respectively at the above conditions. The hydrogen yield from biodiesel is higher than from unmodified oils i.e., transesterification increases hydrogen yield. Increase in saturation of the esters, results in increase in methane selectivity, while an increase in unsaturation results in a decrease in methane selectivity. Increase in degree of both saturation and unsaturation of esters, increases coke selectivity. Similarly an increase in the linoleic content of esters, increases coke selectivity.     

Optimal renewable power generation systems for Busan metropolitan city in South Korea

The metropolitan cities of developed countries comprise more than 50% of the global population and consume over 60% of the world's energy. Many governments plan to enhance their energy infrastructure and the electricity supply–demand reliability of their energy sources. Among them, South Korea's government has developed electricity generation facilities, most of which use renewable resources such as photovoltaic and wind energy. This study determines the optimal renewable electricity generation configuration for one of the largest metropolitan cities in South Korea, Busan metropolitan city. A simulation using 2013 Busan electricity demand data produces this optimal configuration, which includes photovoltaic panels, wind facilities, converters, and batteries with $0.399 of COE (Cost of Electricity) and 100% of renewable fractions. Both the study's practical limitations and implications are discussed.     

Brassica carinata as an alternative oil crop for the production of biodiesel in Italy: agronomic evaluation, fuel production by transesterification and characterization

In this study, the non-food use of Brassica carinata oil for biodiesel production was investigated. B. carinata, a native plant of the Ethiopian highlands widely used as food by the Ethiopians, has recently become object of increasing interest. This is due to its better agronomic performances in areas such as Spain, California and Italy that are characterized by unfavorable environmental conditions for the cultivation of Brassica napus (by far the most common rapeseed cultivated in continental Europe). The agronomic performance and the energetic balance described here confirmed that B. carinata adapted better and was more productive both in adverse conditions (clay- and sandy-type soils and in semi-arid temperate climate) and under low cropping system when compared with B. napus. The biodiesel, produced by transesterification of the oil extracted from the B. carinata seeds, displayed physical–chemical properties suitable for the use as diesel car fuel. A comparison of the performance of B. carinata oil-derived biodiesel with a commercial biodiesel and petroleum diesel fuel was conducted as regards engine performance, regulated and unregulated exhaust emissions. These results make B. carinata a promising oil feedstock for cultivation in coastal areas of central-southern Italy, where it is more difficult to achieve the productivity potentials of B. napus, and could offer the possibility of exploiting the Mediterranean marginal areas for energetic purposes.