Bio-diesel as an alternative fuel for diesel engines—A review

The present review aims to study the prospects and opportunities of introducing vegetable oils and their derivatives as fuel in diesel engines. In our country the ratio of diesel to gasoline fuel is 7:1, depicting a highly skewed situation. Thus, it is necessary to replace fossil diesel fuel by alternative fuels. Vegetable oils present a very promising scenario of functioning as alternative fuels to fossil diesel fuel. The properties of these oils can be compared favorably with the characteristics required for internal combustion engine fuels. Fuel-related properties are reviewed and compared with those of conventional diesel fuel. Peak pressure development, heat release rate analysis, and vibration analysis of the engine are discussed in relation with the use of bio-diesel and conventional diesel fuel. Optimization of alkali-catalyzed transesterification of Pungamia pinnata oil for the production of bio-diesel is discussed. Use of bio-diesel in a conventional diesel engine results in substantial reduction in unburned hydrocarbon (UBHC), carbon monoxide (CO), particulate matters (PM) emission and oxide of nitrogen. The suitability of injection timing for diesel engine operation with vegetable oils and its blends, environmental considerations are discussed. Teardown analysis of bio-diesel B20-operated vehicle are also discussed.     

Straight vegetable oils usage in a compression ignition engine—A review

The ever increasing fossil fuel usage and cost, environmental concern has forced the world to look for alternatives. Straight vegetable oils in compression ignition engine are a ready solution available, however, with certain limitations and with some advantages as reported by many researchers. A comprehensive and critical review is presented specifically pertaining to straight vegetable oils usage in diesel engine. A detailed record of historical events described. Research carried out specifically under Indian conditions and international research work on the usage of straight vegetable oils in the diesel engine is separately reviewed. Many researchers have reported that straight vegetable oils in small percentage blends with diesel when used lower capacity diesel engines have shown great promise with regards to the thermal performance as well exhaust emissions. This has been explained in detail. Finally based on the review of international as well as Indian research a SWOT analysis is carried out. The review concludes that there is still scope for research in this area.     

Alternative fuel for gas turbine: Esterified jatropha oil–diesel blend

The oil crisis and the global effort to control the greenhouse effect have forced the researchers to think of various alternative energy sources. This decade has seen increasing importance of chemically treated vegetable oil biodiesel fuels for various applications in heat engines. Post-Kyoto negotiations refer to high level talks attempting to address global warming by limiting greenhouse gas emissions. During Climate Change Conference in Copenhagen the potential topics discussed were carbon capture and storage, biofuels, adaptation financing, technology transfer, sustainable agriculture, emissions targets, tropical forests and rural and transport electrification. Our area of interest is biofuels under which nonedible Jatropha oil due to its properties which are very close to diesel fuel is being explored as an alternative fuel. A lot of research is underway in the use of different biodiesel fuels in Internal Combustion engines, but very limited work has been reported in its use in gas turbines. This paper describes the results of an ongoing development program aimed at determining the technical feasibility of utilizing biodiesel in IS/60 Rovers gas turbine. The test rig is equipped with a dynamometer for turbine loading and AVL exhaust gas analyzer has been used to record emissions. The test results of 2 blends have been reported in this paper. Analyzing the results compared with the base line performance using diesel fuel under normal conditions show encouraging outcomes.     

Gas diffusion layers for PEM fuel cells: Materials,properties and manufacturing – A review

The complexity in proton exchange membrane fuel cell (PEMFC) stack stems from the fact that numerous physio-chemical processes as well as multi-functional components are involved in its operation. Among the various components a Gas Diffusion Layer (GDL) being an integral component that plays a significant role in determining the performance, durability, and the dynamic characteristics, when air is used as oxidant. In addition, it serves as an armour to safeguard the membrane (Nafion), which is a delicate as well as one of the most expensive components of the PEMFC stack. A comprehensive insight on the GDL can help us to assess the fuel cell stack performance and durability. Apparently, the gas (hydrogen and air/oxygen) being converted to the energy in a PEM fuel cell needs to be diffused uniformly for which surface attributes and porosity must also be well interpreted. This review is a comprehensive assessment made on the fundamental mechanism of the diffusion process along with the various materials involved and evaluating their pros and cons. Eventually, the various manufacturing techniques involved in the GDL fabrication process are also reviewed holistically. It is envisaged that the additive manufacturing process can be a potential option to fabricate a GDL in a cost-effective and simple manufacturing approach.     

Steam-to-carbon ratio control strategy for start-up and operation of a fuel processor

The purpose of this work is to suggest a steam-to-carbon ratio (SCR) control strategy for the start-up and operation of a fuel processor and to experimentally verify this strategy. To overcome ambient temperature variability and manufacturing deviations, a controlled SCR method (CSM) is suggested. The CSM controls the water flow rate independently through heat exchangers (HEXs) to maintain a constant inlet temperature of the reactors. To consistently satisfy the target SCR value, the remaining water after control is fed to the last HEX used as a buffer. To verify the CSM, seven gasoline fuel processors (GFPs) were constructed. The GFPs consisted of an autothermal reformer (ATR), hydrodesulphurization (HDS), a high-temperature shift reactor (HTS), a medium-temperature shift reactor (MTS), a preferential oxidation reactor (PROX), a HEX, and an exhaust gas burner. Water was individually supplied to HEX #1 ～ HEX #4 as a cool-side fluid. One of the GFPs was operated at a low (?32 °C) and a high (50 °C) temperature. The CSM maintained a constant inlet temperature of the reactors; only the inlet temperature of the PROX was affected by the ambient temperature thanks to the CSM. Temperature results for the other six GFPs showed that manufacturing deviations appeared only in the inlet temperature of the PROX by the CSM. To confirm the effect of the CSM on durability, 38 start–stop cycles were performed over 314 h of operation. The results showed that the repeated use of the CSM led to a slow degradation of efficiency, while the temperatures of the reformer and reactor remained steady during cycling testing.     

Water-gas shift reactor for fuel cell systems: Stable operation for 5000 hours

The water-gas shift reactor in the fuel processing unit of a fuel cell system has the vital function of reducing the concentration of CO in the reforming reactor's product gas to values of between 1.0 and 1.5 vol% in order to protect the anodic catalyst from becoming irreversibly poisoned. This paper presents Jülich's recent development in this field, specifically the WGS 6 in the 5 kW_e class. The WGS 6 is characterized by a fundamentally new concept for arranging high temperature and low temperature shift stages. Both stages are now coaxially integrated in one joint casing to provide higher values for the power density and specific power, whereas in earlier reactor generations, these stages are arranged in two separate, parallel housings. In addition, this contribution presents results from a long-term experiment for 5000 h on stream with WGS 6 and discusses the temporal trends of the product gas composition and reactor temperatures across this timespan. For this experiment, the inlet gas stream is produced by an autothermal reformer, which is installed upstream of the WGS 6.     

Systematic approach for recognizing limiting factors for growth of biomethane use in transportation sector – A case study in Finland

In this paper, limiting factors for increased use of biomethane as a transportation fuel are studied. The aim of this research is to recognize and estimate the limiting factors for biomethane utilization in the transportation sector. The limiting factors are studied by using calculation models from Life cycle perspective and literature reviews. According to the results, the main limiting factors can be classified into the following categories: production potential, technology, economy or policy. For biomethane utilization in Finland, the main limiting factors seem to be the lack of distribution infrastructure in northern parts of the country and the uncertain economical feasibility for agricultural biomass producers and for vehicle owners. From the political perspective, the external costs for petrol operated vehicles are higher than for biomethane operated vehicles. Reductions from the external costs could be used by political decisions as a base to support the growth of biomethane in the transportation sector which could lead to GHG emission reductions. A similar systematic approach can also be used to study limiting factors for other transportation energy systems.     

Identifying and addressing barriers for the sustainable development of natural gas as automotive fuel

In recognition of the risks associated with climate change, governments around the world have tried to develop and define policies to address greenhouse gas emissions with transport recognized as one of major sources of greenhouse gases and air pollution. Apart from climate change, there is another side to this coin, and that is the risks surrounding energy security and future oil supplies. Vehicle manufacturers are increasingly recognizing their role in contributing to the goal of decarbonizing the economy and reduce dependence on oil. Out of available alternate fuels compressed natural gas (CNG) is the one which is meeting the maximum needs of countries worldwide, who want to switch over to alternate fuels. However, despite the fact that CNG are often seen as a panacea by policy-makers, there are a number of barriers to their widespread market penetration and diffusion. This study aims to identify an approach to strategic framework for addressing the barriers to widespread adoption of compressed natural gas as transportation fuel. Besides assessing the barriers to natural gas vehicles, the study attempts to identify how they can affect various stakeholders. The paper systematically examines natural gas vehicles (NGVs) adoption patterns and the evolution of pertinent market structures throughout the world but majorly concentrated on eleven countries:, China, Iran, Pakistan, Argentina, India, Brazil, Italy, United States, Germany, Sweden and South Korea. The underlying paper set out an objective of presentation of the framework for supporting policy makers in aspects including; identifying and assessing qualitative aspects of the barriers and consequently defining measures for their resolutions.     

Hydrogen related degradation in pipeline steel: A review

To support our increasing energy demand, steel pipelines are deployed in transporting oil and natural gas resources for long distances. However, numerous steel structures experience catastrophic failures due to the evolution of hydrogen from their service environments initiated by corrosion reactions and/or cathodic protection. This process results in deleterious effect on the mechanical strength of these ferrous steel structures and their principal components. The major sources of hydrogen in offshore/subsea pipeline installations are moisture as well as molecular water reduction resulting from cathodic protection. Hydrogen induced cracking comes into effect as a synergy of hydrogen concentration and stress level on susceptible steel materials, leading to severe hydrogen embrittlement (HE) scenarios. This usually manifests in the form of induced-crack episodes, e.g., hydrogen induced cracking (HIC), stress-oriented hydrogen induced cracking (SOHIC) and sulfide stress corrosion cracking (SSCC). In this work, we have outlined sources of hydrogen attack as well as their induced failure mechanisms. Several past and recent studies supporting them have also been highlighted in line with understanding of the effect of hydrogen on pipeline steel failure. Different experimental techniques such as Devanathan–Stachurski method, thermal desorption spectrometry, hydrogen microprint technique, electrochemical impedance spectroscopy and electrochemical noise have proven to be useful in investigating hydrogen damage in pipeline steels. This has also necessitated our coverage of relatively comprehensive assessments of the effect of hydrogen on contemporary high-strength pipeline steel processed by thermomechanical controlled rolling. The effect of HE on cleavage planes and/or grain boundaries has prompted in depth crystallographic texture analysis within this work as a very important parameter influencing the corrosion behavior of pipeline steels. More information regarding microstructure and grain boundary interaction effects have been presented as well as the mechanisms of crack interaction with microstructure. Since hydrogen degradation is accompanied by other corrosion-related causes, this review also addresses key corrosion causes affecting offshore pipeline structures fabricated from steel. We have enlisted and extensively discussed several recent corrosion mitigation trials and performance tests in various media at different thermal and pressure conditions.     

Ni–Pt/C as anode electrocatalyst for a direct borohydride fuel cell

In this study, a series of Ni–Pt/C and Ni/C catalysts, which were employed as anode catalysts for a direct borohydride fuel cell (DBFC), were prepared and investigated by XRD, TEM, cyclic voltammetry, chronopotentiometry and fuel cell test. The particle size of Ni₃₇–Pt₃/C (mass ratio, Ni:Pt = 37:3) catalyst was sharply reduced by the addition of ultra low amount of Pt. And the electrochemical measurements showed that the electro-catalytic activity and stability of the Ni₃₇–Pt₃/C catalysts were improved compared with Ni/C catalyst. The DBFC employing Ni₃₇–Pt₃/C catalyst on the anode (metal loading, 1 mg cm⁻²) showed a maximum power density of 221.0 mW cm⁻² at 60 °C, while under identical condition the maximum power density was 150.6 mW cm⁻² for Ni/C. Furthermore, the polarization curves and hydrogen evolution behaviors on all the catalysts were investigated on the working conditions of the DBFC.     

Clay as a dispersant in the catalyst layer for zinc–air fuel cells

This study proposes a four-layer membrane electrode assembly (MEA) consisting of air-electrode, proton exchange membrane, Zn-electrode with KOH or NaCl aqueous electrolyte and a steel supporter, for use in Zn–air fuel cells. Montmorillonite clay was used to disperse carbon black (CB) and MnO₂ catalyst to improve the performance of the air-electrode. The microstructures of the air-electrode and cell characteristics were investigated by field emission scanning electron microscopy (FE-SEM), optical microscopy (OM) and an electrochemical analyzer. The experimental results indicate that the four-layer MEA for Zn–air fuel cells reached a power density of 6 mW cm⁻² (at 10 mA cm⁻²) without electrolyte leakage from the cells. The open circuit voltage (OCV) and current density were improved by adding clay to the air-electrode as clay can minimize CB aggregation. In the polarization test, the OCV value (1.40 V) reached approximately 90% of the standard potential (1.65 V) and remained steadily over 48 h. These experimental results demonstrate the four-layer MEA can replace conventional Zn–air fuel cells that utilize aqueous electrolyte.     

Carbon monoxide poisoning and mitigation strategies for polymer electrolyte membrane fuel cells – A review

Polymer electrolyte membrane fuel cells (PEMFC) have received much attention due to their high power density, good start-stop capabilities and high gravimetric and volumetric power density compared with other fuel cells. However, certain technological challenges persist, which include the fact that conventional anode electrocatalysts are poisoned by low levels (few ppm) of carbon monoxide (CO). This review considers the mechanism of CO poisoning and the effects that it has on the PEMFC performance. The key parameters affecting CO poisoning are identified and methods used to mitigate the effects are discussed. These mitigation strategies are divided into three groups according to the means by which the technologies are applied: pre-treatment of reformate, on board removal of CO and in operando mitigation strategies.     

Nickel–carbon nanocomposites prepared using castor oil as precursor: A novel catalyst for ethanol steam reforming

A novel and simple method to prepare nickel-based catalysts for ethanol steam reforming is proposed. The present method was developed using castor oil as a precursor. The results clarify that the nickel–carbon (Ni/C) catalyst has a high activity for ethanol steam reforming. It was observed that the catalytic behavior could be modified according to the experimental conditions employed. Moreover, it is interesting to note that the increase in the catalytic activity of the Ni/C nanocomposite over time, at 500 and 600 °C of reaction temperature, may be associated with the formation of filamentous carbon. The preliminary results indicate that the novel methodology used, led to the obtainment of materials with important properties that can be extended to applications in different catalytic process.     

Utilities’ business models for renewable energy: A review

The transformation of today's electric power sector to a more sustainable energy production based on renewable energies will change the structure of the industry. Consequently, utilities as the major stakeholders in this transformation will face new challenges in their way of doing business. They will have to adapt their business models to remain competitive in the new energy landscape. The present review of business model literature shows that two basic choices exist: utility-side business models and customer-side business models. The two approaches follow a very different logic of value creation. While the former is based on a small number of large projects, the latter is based on a large number of small projects. The article reveals that blueprints for utility-side business models are available, whereas customer-side business models are in an early stage of development. Applying the business model framework as an analytical tool, it is found that existing utility-side business models comprise a series of advantages for utilities in terms of revenue potential and risk avoidance. This study provides new insights about why utilities will favor utility-side business models over customer-side business models and why they also should engage in customer-side business models in their quest for more sustainable future business models.     

Recent developments in bifunctional air electrodes for unitized regenerative proton exchange membrane fuel cells – A review

Unitized regenerative proton exchange membrane fuel cell (UR-PEMFC) technology has progressed in the recent past and has started appearing towards few applications. However, the UR-PEMFC viability is limited by its lower round-trip efficiency mainly due to several reasons such as sluggish air electrode reactions, lower performance/stability, higher materials cost etc. In this context, many approaches are being implemented for efficiency enhancement including design and development of effective bifunctional air electrodes (oxygen reduction and evolution reactions) materials both for fuel cell and electrolyzer modes as well as for optimization of operating condition for performance stability in real life applications. This review focusses on the recent developments of air electrode active materials design/development for performance improvement in UR-PEMFC. Among all developed electrode materials, the catalysts with Pt- and Ir-based metals still provided the maximum round-trip efficiency of about 50% at 500 mA cm^?2 in the unit cell.     

Zr doped BaFeO3-δ as a robust electrode for symmetrical solid oxide fuel cells

A BaFe_0.9Zr_0.1O_3-δ (BFZ) is successfully synthesized and its characteristics are investigated. The oxide exhibits high stability and a cubic perovskite structure in a reducing atmosphere. A La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ (LSGM) supported symmetrical solid oxide fuel cell (SOFC) with BFZ electrode demonstrates a maximum power density of 1097 mW cm⁻² using humidified H₂ as the fuel and ambient air as the oxidant at 800 °C. And as low as 0.190 Ω cm² of polarization resistance of single cell is observed at 650 °C. Moreover, the electrode demonstrates high stability in 100 h test, as well as redox stability in both oxidizing and reducing atmospheres. The high electrochemical property and good stability suggest that the BFZ is promising candidate for symmetrical SOFC electrode.     

Pd decorated Co–Ni nanowires as a highly efficient catalyst for direct ethanol fuel cells

The storage and conversion of energy necessitates the use of appropriate electrochemical systems and chemical reaction catalysts. This work presents newly developed catalysts for electrooxidation of ethanol in an alkaline medium. Nanocatalysts composed of Co–Ni nanowires (Co–Ni NWs) decorated with Pd nanoparticles (Pd NPs) were made at varying metal ratios and their chemical composition and structure was investigated in detail. The synthesis involved a wet chemical reduction assisted by a magnetic field, which led to the generation of NWs, followed by the deposition of spherical Pd NPs on their surface. The best catalytic activity was obtained for the catalyst made of Co₃–Ni₇ decorated with Pd NPs, which exhibited EOR of 8003 mA/mg_Pd for only 0.86 wt% of Pd loading. The results can be explained by the synergistic effect between the morphology of the bimetallic support and the favorable interaction of oxophilic Co, Ni with catalytic Pd.     

Is it environmentally advantageous to use vegetable oil directly as biofuel instead of converting it to biodiesel?

The oil price instability and the measures taken to reduce the increase in greenhouse gas emissions are the main factors promoting the development and use of environmentally friendly energies. From an energy efficiency point of view, biofuels constitute a renewable energy source and its use helps to reduce energy dependency on fossil fuels. The most used biofuels for transport worldwide are biodiesel (BD) and bioethanol. However, there are other options such as straight vegetable oil (SVO).SVO can be small-scale produced in local cooperatives through pressing, filtering and conditioning processes which are much simpler than the ones required for BD production. In this study a comparative life cycle assessment (LCA) of two biofuels obtained from Spanish rapeseed, namely small-scale SVO and large-scale BD, is performed. The LCA methodology allows the two biofuels’ production and their rate of consumption in a vehicle (a truck) to be compared. In this manner, it is possible to assess which is environmentally advantageous: to use SVO directly as biofuel or to convert it to BD. Moreover, LCA is used in the study to calculate the energy return on investment index (EROI) and an energy conversion ratio to evaluate which biofuel is more energy efficient.The obtained results show the environmental benefits of using SVO instead of BD by analyzing representative impact categories defined by the CML and EDIP methods. A sensitivity analysis has also been conducted. EROI indexes for SVO and BD production show a clear preference for SVO as compared to BD.     

Active fuel design—A way to manage the right fuel for HCCI engines

Homogenous charge compression ignition (HCCI) engines feature high thermal efficiency and ultralow emissions compared to gasoline engines. However, unlike SI engines, HCCI combustion does not have a direct way to trigger the in-cylinder combustion. Therefore, gasoline HCCI combustion is facing challenges in the control of ignition and, combustion, and operational range extension. In this paper, an active fuel design concept was proposed to explore a potential pathway to optimize the HCCI engine combustion and broaden its operational range. The active fuel design concept was realized by real time control of dual-fuel (gasoline and n-heptane) port injection, with exhaust gas recirculation (EGR) rate and intake temperature adjusted. It was found that the cylinderto- cylinder variation in HCCI combustion could be effectively reduced by the optimization in fuel injection proportion, and that the rapid transition process from SI to HCCI could be realized. The active fuel design technology could significantly increase the adaptability of HCCI combustion to increased EGR rate and reduced intake temperature. Active fuel design was shown to broaden the operational HCCI load to 9.3 bar indicated mean effective pressure (IMEP). HCCI operation was used by up to 70% of the SI mode load while reducing fuel consumption and nitrogen oxides emissions. Therefore, the active fuel design technology could manage the right fuel for clean engine combustion, and provide a potential pathway for engine fuel diversification and future engine concept.