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.     

Catalytic exhaust gas fuel reforming for diesel engines—effects of water addition on hydrogen production and fuel conversion efficiency

Previous work in our laboratory has shown that the exhaust gas assisted fuel reforming process has the potential to provide a solution to the diesel engine exhaust emission problems. When simulated reformer product gas rich in hydrogen is fed to the engine, a reduction of both NO_x and smoke emissions can be achieved. In this paper, the optimisation of the reforming process by water addition in the reactor is presented. Using a prototype catalyst at 290°C reactor inlet temperature, up to 15% more hydrogen in the reformer product was obtained compared to operation without water. The process has been found to be mainly a combination of the fuel oxidation, steam reforming and water gas shift reactions. The reforming process efficiency has been shown to improve considerably with water addition up to a certain level after which the adverse effects of the exothermic water gas shift reaction become significant.     

Effect of engine parameters and type of gaseous fuel on the performance of dual-fuel gas diesel engines—A critical review

Petroleum resources are finite and, therefore, search for their alternative non-petroleum fuels for internal combustion engines is continuing all over the world. Moreover gases emitted by petroleum fuel driven vehicles have an adverse effect on the environment and human health. There is universal acceptance of the need to reduce such emissions. Towards this, scientists have proposed various solutions for diesel engines, one of which is the use of gaseous fuels as a supplement for liquid diesel fuel. These engines, which use conventional diesel fuel and gaseous fuel, are referred to as ‘dual-fuel engines’. Natural gas and bio-derived gas appear more attractive alternative fuels for dual-fuel engines in view of their friendly environmental nature. In the gas-fumigated dual-fuel engine, the primary fuel is mixed outside the cylinder before it is inducted into the cylinder. A pilot quantity of liquid fuel is injected towards the end of the compression stroke to initiate combustion. When considering a gaseous fuel for use in existing diesel engines, a number of issues which include, the effects of engine operating and design parameters, and type of gaseous fuel, on the performance of the dual-fuel engines, are important. This paper reviews the research on above issues carried out by various scientists in different diesel engines. This paper touches upon performance, combustion and emission characteristics of dual-fuel engines which use natural gas, biogas, producer gas, methane, liquefied petroleum gas, propane, etc. as gaseous fuel. It reveals that ‘dual-fuel concept’ is a promising technique for controlling both NO_x and soot emissions even on existing diesel engine. But, HC, CO emissions and ‘bsfc’ are higher for part load gas diesel engine operations. Thermal efficiency of dual-fuel engines improve either with increased engine speed, or with advanced injection timings, or with increased amount of pilot fuel. The ignition characteristics of the gaseous fuels need more research for a long-term use in a dual-fuel engine. It is found that, the selection of engine operating and design parameters play a vital role in minimizing the performance divergences between an existing diesel engine and a ‘gas diesel engine’.     

A solution to renewable hydrogen economy for fuel cell buses – A case study for Zhangjiakou in North China

Fuel cell vehicles fueled with renewable hydrogen is recognized as a life-cycle carbon-free option for the transport sector, however, the profitability of the H₂ pathway becomes a key issue for the FCV commercialization. By analyzing the actual data from the Zhangjiakou fuel cell transit bus project, this research reveals it is economically feasible to commercialize FCV in areas with abundant renewable resources. Low electricity for water electrolysis, localization of H₂ supply, and curtailed end price of H₂ refueling effectively reduce the hydrogen production, delivery and refueling cost, and render a chance for the profitability of refueling stations. After the fulfillment of the intense deployment of both vehicles and hydrogen stations for the 2022 Winter Olympics, the H₂ pathway starts to make a profit thereafter. The practices in the Zhangjiakou FCB project offer a solution to the hydrogen economy, which helps to break the chicken-egg dilemma of vehicles and hydrogen infrastructure.     

Active solar distillation—A detailed review

All over the world, access to potable water to the people are narrowing down day by day. Most of the human diseases are due to polluted or non-purified water resources. Even today, under developed countries and developing countries face a huge water scarcity because of unplanned mechanism and pollution created by manmade activities. Water purification without affecting the ecosystem is the need of the hour. In this context, many conventional and non-conventional techniques have been developed for purification of saline water. Among these, solar distillation proves to be both economical and eco-friendly technique particularly in rural areas. Many active distillation systems have been developed to overcome the problem of lower distillate output in passive solar stills. This article provides a detailed review of different studies on active solar distillation system over the years. Thermal modelling was done for various types of active single slope solar distillation system. This review would also throw light on the scope for further research and recommendations in active solar distillation system.     

Nonlinear D-optimal design of experiments for polymer–electrolyte–membrane fuel cells

Using empirical models, parameters have to be estimated from experimental data. Experimental characterization of fuel cell stacks is an expensive and time-consuming task. Therefore it is very important to choose an experimental design, which maximizes the statistical quality of the resulting information. Box and Lucas (Biometrika 46 (1959)) showed that it is possible to optimize nonlinear experimental designs by the minimization of the covariance matrix of the least squares estimate. The aim of this work is to adopt this general method in order to investigate its ability for application in polymer–electrolyte–membrane fuel cell (PEMFC) characterization. Based on an empirical PEMFC model a D-optimal design criterion has been developed and validated. Numerical methods, evolutionary and heuristic are investigated with respect to fast and robust evaluation of the design criterion. For a given set of experimental data best results are achieved using a heuristic approach, a so-called sequential search. Based on that result an algorithm to obtain an optimal design of experiments (DoE) in a nondeterministic operating area is introduced. The proposed algorithm is able to take into account experimental limitations due to test facilities or examinee. The algorithm further allows to include existing and for reference needed experiments.     

Portable fuel cell systems for America’s army: technology transition to the field

The US Army Communications, Electronics Research Development and Engineering Center (CERDEC) envisions three thrust areas for portable fuel cell systems for military applications. These areas include soldier power (<500 W), sensor power (0–100 W), and auxiliary power units or APUs (0.5–10 kW). Soldier and sensor fuel cell systems may be man-portable/backpackable while APUs could be employed as squad battery chargers or as ‘Silent Watch’ APUs where low signature (acoustic, thermal, etc.) operation is a requirement.The Army’s research and development efforts are focusing on methods of either storing or generating hydrogen on the battlefield. Hydrogen storage technology is considered critical to small military and/or commercial fuel cell systems, and is being pursued in a host of commercial and government programs. CERDEC, in a joint effort with the Army Research Office (ARO) and the Defense Advanced Research Projects Agency (DARPA), is developing several promising hydrogen generating technologies. The goal of this program is a safe, reliable hydrogen source that can provide rates up to 100 W with an energy density of greater than 1000 Wh/kg.For larger fuel cell units (>500 W), it is imperative that the fuel cell power units be able to operate on fuels within the military logistics chain [DOD 4140.25-M, DOD Directive 4140.25 (1993)]. CERDEC is currently conducting research on catalysts and microchannel fuel reformers that offer great promise for the reforming of diesel and JP-8 fuels into hydrogen. In addition to research work on PEM fuel cells and enabling technologies, the Army is also conducting research on direct methanol and solid oxide fuel cells, and combined heat and power applications utilizing new high temperature fuel cells.     

How to design a border adjustment for the European Union Emissions Trading System?

Border adjustments are currently discussed to limit the possible adverse impact of climate policies on competitiveness and carbon leakage. We discuss the main choices that will have to be made if the European Union implements such a system alongside the EU ETS. Although more analysis is required on some issues, on others some design options seem clearly preferable to others. First, the import adjustment should be a requirement to surrender allowances rather than a tax. Second, the general rule to determine the amount of allowances per ton imported should be the product-specific benchmarks that the European Commission is currently elaborating for a different purpose (i.e. to determine the amount of free allowances). Third, this obligation should apply when the imported product is registered at the EU border, and not after the end of the year as is the case for domestic emitters. Fourth, the export adjustment should take the form of a rebate on the amount of allowances a domestic emitter has to surrender. Five, this rebate should equal the above-mentioned product-specific benchmarks, not the emissions of the particular exporting plant or firm. Finally, the adjustment does not have to apply to consumer products but mostly to basic products.     

Anthracite pretreatment for high-performance direct carbon solid oxide fuel cell — A green pathway for power generation

Coal-fueled direct carbon solid oxide fuel cell (DC-SOFC) is a very attractive electrochemical conversion device. However, coal contains a certain amount of ash, such as Al, Si, S, etc., which are toxicants for SOFC components. To solve the above problem, anthracite is pyrolyzed at 600 °C to obtain semi-coking coal results in better cell performance. The results show that the higher carbon gasification oxidation activity of semi-coking coal is due to the higher amount of fixed carbon and catalyst. Therefore, more fuel gas (CO) is available in the anode chamber for the Boudouard reaction. Also, the electrochemical performance of both coals as DC-SOFC fuel was compared using La_0·4Sr_0·6Co_0·2Fe_0·7Nb_0·1O_3-δ (LSCFN) as anode. The maximum power density (MPD) of the DC-SOFC with semi-coking coal is 596 mW cm⁻² at 850 °C, much higher than that of the SOFC using anthracite (396 mW cm⁻²) as the fuel. Furthermore, at the same fuel content, the cell fueled with semi-coking coal has a longer discharge time (30 h), which shows a better stability.     

A method for the techno-economic evaluation of chemical processes—improvements to the “OPTIMO” code

This paper describes the improvement of a chemical engineering code [1] developed specifically for the evaluation and analysis of multi-step processes. The capabilities of the original code have been retained in that the mass and energy balances are the basis of a heat exchange network synthesis. However, rather than complete the evaluation with the process thermal efficiency as before, the program has been extended in order to accommodate a more detailed nuclear reactor-chemical plant coupling and new routines were written so that the hydrogen production cost can be estimated.The code was applied to two sulphur-based cycles and the results are presented later.     

A novel approach to analyse incomplete design of experiments – Application to the study of the influence of operational parameters on the performance of a solid oxide fuel cell based micro-combined heat and power system

A SOFC based commercial μ-CHP system is characterized by Electrochemical Impedance Spectroscopy, using a 2⁴ full factorial test plan. The studied factors are: natural gas input power, ratio between oxygen and natural gas flow rates at the reformer inlet, stack average temperature and average operating cell voltage. Six replicates are performed in the domain centre. We performed equivalent circuit analysis and extracted three responses from each spectrum: ohmic resistance together with the two parameters of the CPE used in the model.However, one of our experiment is an outlier. To circumvent this problem, two methods described in the literature were applied: recalculation of missing response and introduction of a dynamic variable. Due their unsatisfactory results, we developed an innovative approach combining an iterative fitting of the multilinear model underlying any factorial design and an N-way ANOVA. Our method is successfully validated on the different 2⁴⁻¹ fractional designs deriving from the full factorial one.The only impacted response is the ohmic resistance. It increases as temperature decreases or as applied voltage increases. It is impacted by a strong synergistic effect of pressure and temperature and a compensating effect of pressure and applied voltage. No significant quadratic effect is observed.     

Methane–hydrogen fuel blends for SI engines in Brazilian public transport: Potential supply and environmental issues

In the last decades, the whole world has been feeling the effects of environmental pollution, especially air pollution in large cities, with the transport sector as a major contributor to this scenario. In this sense, Brazil presents 27 states with great potential for biogas generation from landfills through anaerobic digestion. Only in the year 2016, the calculations presented in this paper point to a methane production in landfills of 5.57E+09 m³. On the other hand, the high number of rivers and hydroelectric dams in the country makes possible the generation of electricity that reached 90.27 TWh in 2016. However, the water that is drained by the floodgates to control the level of the reservoirs becomes an interesting wasted energy source for other uses, such as the production of other clean fuel, hydrogen, through classical processes such as electrolysis. It is pointed out the possibility of producing 2.76E+06 tons of hydrogen only with the energy drained in these hydroelectric plants. These two fuels together can be used to fuel vehicles powered by the hydrogen–methane blends, like HBio95 and HBio60. The promise of harmful and CO₂ emissions by focusing on mixture of gases has recently attracted the interest of vehicle manufacturers and transport operators. In this scenario, this work presents an analysis on the use of mixture of gases in the urban bus fleet of the 27 Brazilian states, using as energy source derived from secondary energy from Brazilian hydroelectric plants and biogas from sanitary landfills, comparing this scenario with the use of only methane from landfills or only H₂ from hydroelectric plants, assessing issues such as pollutant emissions, engine performance and deployment facilities.     

Application of Plackett–Burman design to screen the effective process parameters for biodiesel production

Significance of biodiesel is increasing forever because of increase in environmental pollution caused by fossil fuel and increasing of fossil fuel prices. Hence, the main goal of this study is to screen the effective process parameters for biodiesel production from chicken fat. Plackett–Burman (PB) design was used to screen the effective process variables among molar ratio, catalyst concentration (%), ultrasound power (W), mixing intensity (rpm), reaction time (min), temperature (°C), and moisture level (%). The obtained biodiesel quality is compared with American Society for Testing and Materials (ASTM) standard methods. This result confirms the effectiveness of PB design to screen the effective process parameters for biodiesel production.     

Study of cold start air–fuel mixture parameters for spark ignition engines fueled with gasoline–isobutanol blends

Biofuels are set to play an important role in the future strategy of automotive fuel suppliers, and therefore the study of using alcohols in spark ignition engines has become a necessity. A simple thermodynamic model was developed for calculating air–fuel mixture parameters for port injection engines fueled with gasoline–isobutanol blends, and theoretical results were compared to experimental values. For simulating the evaporation process, gasoline was considered a mixture of four components, with isobutanol added in different proportions. As all engine components are at ambient temperature during cold starts, mixture formation was considered an adiabatic process, with the fuel breaking up into droplets and evaporating, thus resulting in a temperature drop. A port injection engine fitted to a passenger car was used to validate the model for calculating air–fuel mixture parameters.     

Heat transfer analysis for the design and application of the passive cooling rate controlled device—Box-in-box

BackgroundIn cryopreservation, cooling rate is a dominant factor that influences the survival of cells. Box-in-box (BIB) was recently developed as a reliable, cooling rate controlled and cost-effective cooling device. However, the intrinsic heat transfer characteristic still needs to be further specified for the best of design and application of the device.MethodThe freezing process of samples inside BIB is simulated by developing a one dimensional heat transfer model in which fixed-grid technique is used to solve the solidification problem of the ternary cryopreservation media (water, NaCl and cryoprotectant). Based on the model, several critical factors, including supercooling temperature, structural parameters and application conditions, are evaluated respectively. Several cell free experiments were also conducted to validate the model.ResultsIt was demonstrated that BIB method can achieve uniform and consistent cooling of samples, and the theoretical and experimental results fit quite well. Further analysis reveals that several structural parameters (such as the dimension of insulation layer) and application conditions (such as the cryoprotectant concentration and the sample volume) have significant effect on the freezing process of sample. Thus the design and application of BIB should be carefully conducted to achieve the desired cooling rate.ConclusionThe theoretical model is reasonable for the BIB system. It provides an effective tool to determine the detailed structural parameters when designing BIBs, and it can also be used as a good support for the application of BIB systems.     

Hydrogen quality for fuel cell vehicles – A modeling study of the sensitivity of impurity content in hydrogen to the process variables in the SMR–PSA pathway

As fuel cell vehicles approach wide-scale deployment, the issue of the quality of hydrogen dispensed to the vehicles has become increasingly important. The various factors that must be considered include the effects of different contaminants on fuel cell performance and durability, the production and purification of hydrogen to meet fuel quality guidelines, and the associated costs of providing hydrogen of that quality to the fuel cell vehicles. In this paper, we describe the development of a model to track the formation and removal of several contaminants over the various steps of hydrogen production by steam-methane reforming (SMR) of natural gas, followed by purification by pressure-swing adsorption (PSA). We have used the model to evaluate the effects of setting varying levels of these contaminants in the product hydrogen on the production/purification efficiency, hydrogen recovery, and the cost of the hydrogen. The model can be used to track contaminants such as CO₂, CO, N₂, CH₄, and H₂S in the process. The results indicate that a suggested specification of 0.2 ppm CO would limit the maximum hydrogen recovery from the PSA under typical design and operating conditions. The steam-to-carbon ratio and the process pressure are found to have a significant impact on the process efficiency. Varying the CO specification from 0.1 to 1 ppm is not expected to affect the cost of hydrogen significantly, although the cost of gas analysis to comply with such stringent requirements may add 2–10 cents/kg to the cost of hydrogen.     

The German energy audit program for firms—a cost-effective way to improve energy efficiency?

In 2008, a program was established in Germany to provide grants for energy audits in small- and medium-sized enterprises. It aims to overcome barriers to energy efficiency, like the lack of information or a lack of capacity, and is intended to increase the adoption of energy efficiency measures. We evaluate the program's impact in terms of energy savings, CO₂ mitigation, and cost-effectiveness. We find that firms adopt 1.7?C2.9 energy efficiency measures, which they would not have adopted without the program. Taking a firm's perspective, the program shows a net present value ranging from ?0.4 to 6??/MWh saved, which very likely implies a net benefit. For the government, each ton of CO₂ mitigated costs between 1.8 and 4.1??. Each euro of public expenditure on audit grants led to 17?C33?? of private investment. The cost-effectiveness of the program for firms and the low share of public expenditure underline its value for the German energy efficiency policy mix and suggest that it should be expanded in Germany. Further, the good experiences with the program in Germany should encourage countries which have not yet established an audit program to do so.     

Are car manufacturers on the way to reduce CO2 emissions?: A DEA approach

One of the pillars of the fight against climate change is reducing the amount of greenhouse gases that are emitted into the atmosphere. In that regard, curtailing CO₂ emissions from transport activities is a major objective. In its attempts of “decarbonising” transport, the European Commission set in 2009 different emission limits on the vehicles sold in Europe. With this background, this paper aims to test the ability of the major car manufacturers to meet these present and future targets with the existing technological trends. To that end, we provide an in-depth analysis on the temporal evolution of emission efficiencies in the Spanish car market. The well-known DEA-Malmquist method is applied over a large sample of car models sold in Spain between 2004 and 2010. A second-stage regression allows us to identify the main drivers of efficiency, catch-up and technical change over the period. Finally, the estimated trends are extrapolated to predict future emission levels for the car manufacturers. Using post-regulation rates of technical change, results show that the vast majority of companies would meet the 2015 target, 27% of the current market would meet the 2020 target, and around 3% would be able to comply with the 2025 target. Thus, since all targets are technologically feasible, stricter regulation is the recommended approach to encourage manufacturers to meet the goals set by the European Commission.     

A solution to the unit commitment problem—a review

Unit commitment (UC) is an optimization problem used to determine the operation schedule of the generating units at every hour interval with varying loads under different constraints and environments. Many algorithms have been invented in the past five decades for optimization of the UC problem, but still researchers are working in this field to find new hybrid algorithms to make the problem more realistic. The importance of UC is increasing with the constantly varying demands. Therefore, there is an urgent need in the power sector to keep track of the latest methodologies to further optimize the working criterions of the generating units. This paper focuses on providing a clear review of the latest techniques employed in optimizing UC problems for both stochastic and deterministic loads, which has been acquired from many peer reviewed published papers. It has been divided into many sections which include various constraints based on profit, security, emission and time. It emphasizes not only on deregulated and regulated environments but also on renewable energy and distributed generating systems. In terms of contributions, the detailed analysis of all the UC algorithms has been discussed for the benefit of new researchers interested in working in this field.