Syngas, a sustainable fuel produced from biomass, often contains a significant proportion of hydrogen (H2) and carbon monoxide (CO). The viability of syngas, as a substitute for petroleum diesel fuel in a dual-fuel (DF) diesel engine is crucial to evaluate considering its combustive properties and environmental benefits. Artificial intelligence-based methods are widely used to optimize engine operations but are still rare in DF syngas/diesel engines. This study introduces a novel methodology combining the Adaptive Neuro-Fuzzy Inference System (ANFIS) with the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to optimize engine load, compression ratio (CR), and injection timing (IT). The ANFIS method is utilized to represent the intricate connections between engine parameters and output responses. Meanwhile, the TOPSIS technique is employed to determine the best combination of parameters that will maximize brake thermal efficiency (BTE) and pilot fuel replacement (PFR) and minimize emissions of unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOX). Strong predictive abilities were shown by the ANFIS model, whose coefficients of determination (R2) ranged from 0.86 to 0.96. The experimental findings demonstrate that the use of syngas in DF mode greatly improves BTE, reaching a maximum value of 25.59% under conditions of 100% load, CR of 18, and IT of 29 degrees before top dead centre (BTDC). The ANFIS-TOPSIS algorithm effectively identifies the best operating conditions, which include a 60% load, 17.5 CR, and 29 degrees BTDC. Significantly, the levels of HC and CO emissions decreased to 399.92 ppm and 367.77 ppm, respectively, while the NOX emissions remained at 146.61 ppm. This study innovatively integrates TOPSIS and ANFIS to optimize a syngas-diesel engine, contributing to the knowledge base on alternative fuels, and enabling the development of cleaner and more efficient engines.

This research work attempts to explore the combined effect of engine load and compression ratio (CR) on the performance, combustion, and emission characteristics of a 3.5 kW diesel engine utilizing simulated biogas (SBG), simulated producer gas (SPG), and SPG-SBG mixture under dual fuel (DF) mode. The compositions of the gaseous fuels are prepared based on the volumetric percentage of the individual gas components and are inducted into the engine cylinder using a novel venturi-type air-gas mixer. For the preparation of SBG, methane (CH4) and carbon dioxide (CO2) are mixed at a 70:30 ratio. Similarly, hydrogen (H2) and carbon monoxide (CO) are also mixed at a 70:30 ratio for the preparation of SPG. Again, H2 and CO at a 50:50 ratio are mixed with a 70:30 ratio of CH4 and CO2 to simulate the SPG-SBG mixture. Engine experiments are executed at five different loads, viz. 20

The substrate/water ratio and temperature effects on biogas production rate were investigated using cattle dung as substrate. Initially, laboratory-scale experiments were performed considering three substrate/water ratios of 1:1.5, 1:1 and 1.5:1 in both controlled (35°C) and uncontrolled environments for 55 days. The substrate/water ratio of 1:1 achieved the highest specific cumulative biogas yield of 247.75 and 311.14 ml/gVS for uncontrolled and controlled digesters, respectively, and consequently, considered for field-scale experiments that were performed in 1 m3 capacity anaerobic digestion plant at three different phases. An average volume of 6.26 m3/week of biogas was generated during the summer season (first phase) against the loading of 50.00 ± 1.50 kg cattle dung slurry/day. Subsequently, in the third phase of the experiment, the integration of the solar-assisted heating system improved the cumulative biogas yield by an average of 9.93% over the digester without solar-assisted heating (second phase) during the winter season. The correlation coefficient (R2) value was also found to be approximately 0.99, revealing that predicted results perfectly fit experimental values. The present study confirms that adopting a passive solar-assisted heating system for a field-scale anaerobic digestion plant is a novel approach towards enhancing the biogas yield.KEYWORDS: Anaerobic digestionsubstrate/water ratiotemperaturesolar-assisted heating systemkinetic analysis Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis study is part of a project (grant number: ECR/2016/001830) funded by the Science and Engineering Research Board (SERB) to the School of Energy Science and Engineering, Indian Institute of Technology Guwahati, India. The financial assistance provided by SERB is gratefully appreciated.

This current experimental investigation attempts to explore the engine performance, combustion behaviour, and exhaust emission of a 3.5 kW capacity diesel engine utilizing synthetic-biogas (SBG), synthetic producer gas (SPG), and SBG-SPG mixture under dual fuel (DF) mode. SBG is prepared by mixing methane (CH4) and carbon dioxide (CO2) at 60:30 ratio. Similarly, hydrogen (H-2) and carbon monoxide (CO) are also mixed at a 50:50 ratio for the preparation of SPG. Again, H-2 and CO at a 50:50 ratio is mixed with a 60:30 ratio of CH4 and CO2 to simulate the SBG-SPG mixture. Engine experiments were executed at standard engine conditions of injection timing (IT) of 23 degrees BTDC and compression ratio (CR) of 17.5 with five different engine loading conditions viz. 20%, 40%, 60%, 80%, and 100%. Maximum brake thermal efficiency (BTE) and pilot fuel replacement (PFR) were obtained at full engine loading condition. At this operating condition, SBG, syngas, and SBG-SPG mixture showed a BTE of 18.2%, 15.92%, and 18.89% respectively. Similarly, PFR of 84%, 78.74%, and 82.92% was found in case of SBG, SPG, and SBG-SPG mixture respectively. The combustion data indicated a decrement in ignition delay (ID) and increment in cylinder pressure with higher engine load. At 100% engine load, minimum ID of 20, 21 and 22 degrees crank angle (CA) was obtained for SBG, SPG, and SBG-SPG mixture respectively. Again, highest peak cylinder pressure (PCP) was obtained for SBG-SPG mixture. It has also been observed that on an average, SPG resulted in higher emission including oxides of nitrogen (NOX), hydrocarbon (HC) and carbon monoxide (CO) compared to SBG. However, mixture of SBG-SPG resulted in 57.48, 0.09 and 5.6% reduction in NOX, HC and CO emissions respectively as compared to SPG.

The combined application of biogas (BG) and producer gas (PG) in diesel engines is a challenge and has scarcely been addressed so far. The present contribution focused on designing a venturi-type mixer to regulate the flow of these gases in a diesel engine under the dual-fuel (DF) mode. The mixer is simulated using CFD software (ANSYS 15.0) with five combinations of BG-PG flow, viz. 80-20%, 60-40%, 50-50%, 40-60% and 20-80% to analyse the flow behaviour, distribution and mixing quality of these gases with the air. The results indicated significant pressure drops at the throat section, which increases the velocity and turbulence inside the mixer to achieve a homogeneous mixture of gases in the divergent section. Moreover, the study resulted in lean air–fuel mixture for all flow combinations in 1.23–1.51. The proposed mixer seem to be suitable for DF engine operation with the combined application of BG and PG.

The study investigates the effect of feedstock/water (F/W) ratio and temperature on biogas generation both in laboratory and field scale anaerobic digesters using cattle dung (CD) as feedstock. Firstly, the lab-scale experiments were conducted under uncontrolled (ambient temperature) and controlled temperature (35±2°C) with three different F/W ratios, viz. 1:1.5, 1:1 and 1.5:1 for the hydraulic retention time (HRT) of 55 days. F/W ratio of 1:1 resulted with maximum biogas yield of 13.49 and 15.08 liters for uncotrolled and controlled digesters respectively. Based on this investigation, F/W ratio of 1:1 is considered for the experimental analysis of a field-scale anaerobic digestion (AD) plant of 1 m3 capacity. The pH value of the substrate was found in the range of 6.9–7.3 in the AD plant. The weekly average biogas production for 28 weeks was 6.26 m3, equivalent to 0.89 m3/day for a feeding rate of 25.00±1.50 kg/day with CD as feedstock

Effort for reduction of global emission level is currently one of the prime areas of concern for the research community across the globe. Particularly due to more stringent standards of emission control, the prevailing diesel engines are on the verge of losing their permission to operate. Engine fuel modification technologies are reported to improve engine combustion and reduce engine emission levels. The enhancement in liquid fuel using oxygenated additives can be a sustainable and cost effective solution to address the issues of the existing diesel engine emission. Among the existing vehicular fuel improvements technologies, the use of biodiesel, alcohols viz. methanol, ethanol, propanol, butanol, and ethers improves performance as well as emission characteristics of engine significantly. As found in open source, the application of biodiesel-alcohol blended fuels can reduce carbon emission by 50–60% and hence considered as a possible conventional fuel substitution for engine applications. These fuels can be applied either completely or as blends with diesel in diesel engines. Moreover, water emulsification with different blends of biofuels can further restrict the engine emission levels particularly the NOx and smoke emission levels up to 25%. Therefore, the current chapter delivers a critical analysis of the use of oxygenated additives for running diesel engines. The improvements in the physiochemical properties of biodiesel/diesel-alcohol blended fuels and their influence on the engine emission characteristics are discussed in the chapter.

Single particle combustion behaviours of coal-biomass fuel mixtures are studied. Different biomass i.e. sawdust, wood and rice husk is blended with locally available low grade coal to carry out the experimental investigation. The combustion of solid fuel consists of flaming combustion and char combustion. Rice husk showed higher flaming time and char glowing time because of higher ash and particle density. The burning time of coal-rice husk mixture fuel sample is higher compared to other samples due to the combine effect of particle density and ash content of the fuel samples. Ignition mass flux of saw dust is higher compared to rice husk and wood fuel particles because of the presence of higher volatiles in sawdust. The diameter index for flaming combustion, char combustion are 1.13 to 0.47 and 0.63 to 1.23 respectively for 0%–40% coal in coal/wood fuel mixtures. It is observed that with the increases in surface area/volume ratio, flaming and char combustion decreases due to reduction in effective surface area of the particle for combustion. This study concludes that particle size or surface area/volume together with particle density are the primary controlling parameter for better conversion of fuel mixtures in any co-combustion system.

The present study focuses on optimizing the engine operating parameters of a dual-fuel (DF) engine. Producer gas (PG) and Honge oil methyl ester (HOME) are used as primary fuel and pilot fuel respectively for the operation. An experimental design matrix of 20 different combinations was considered using Design of Experiments (DoE), based on the central composite design (CCD) of response surface methodology (RSM). The effects of these combinations were experimentally investigated to calculate the performance and emission characteristics of the engine. The objective of the work is to maximize the Brake thermal efficiency (BTE) and minimize the exhaust gas temperature (EGT), nitrogen oxide (NOx), hydrocarbon (HC), and carbon monoxide (CO) emissions. The RSM model is developed using the experimental data and further, the operating parameters were optimized using the desirability approach. The optimized combination of operating parameters was obtained at 61.10% engine load, compression ratio (CR) of 18, and injection timing (IT) of 23.30° before top dead center (BTDC). The optimum responses corresponding to these operating conditions were found as 14.23%, 354.29 °C, 52.18 ppm, 39.53 ppm, and 0.51% for BTE, EGT, NOx, HC, and CO respectively with an overall desirability of 0.962. The optimized responses were validated experimentally at optimum input conditions and found to be within acceptable error levels. Further, an economic analysis of the optimized DF system is also carried out.

The present study proposes a techno-economic assessment of a biogas run diesel engine under dual-fuel (DF) mode using response surface methodology (RSM). Initially, engine experiments are conducted based on an experimental matrix designed with design of experiments (DoE) to investigate the effects of load, compression ratio (CR), and injection timing (IT). The quadratic models developed based on the experimental results are used to predict the output variable responses such as brake thermal efficiency (BTE), biogas flow rate (BFR), oxides of nitrogen (NOx), hydrocarbon (HC), carbon monoxide (CO) and carbon dioxide (CO2). Optimization of independent variables with desirability approach gave the optimum running condition for the engine i.e. 71% engine load, CR of 17.5, and IT of 28.5 degrees BTDC with an overall desirability index of 0.96. Experimental verification of the optimized results gave a very close agreement with least error levels. Further, a financial evaluation of the optimized DF system as a remote power-generating unit is carried out. The results indicated a levelized unit cost of electricity (LUCE) of 0.36 USD/kWh with a payback period of 7.5 years. However, with the increase in capacity of the system, the LUCE is bought down significantly to 0.183 USD/kWh and tariff charges to 0.125 USD/ kWh after a payback period of 6.8 years.

The present study highlighted the effect of feedstock/water (F/W) ratio and temperature on biogas generation from cattle dung (CD) and vegetable waste (VW). The daily biogas generation was investigated for retention time of 55 days by considering F/W ratio of 80:20, 60:40, 40:60 and 20:80 for both the feedstocks. The highest cumulative biogas production for CD and VW were found to be 11.25 and 4.09 l with average pH values of 6.5 and 3.5 respectively at F/W ratio of 60:40. Temperature-controlled experiments were performed under mesophilic (35 ± 2 °C) and thermophilic (55 ± 2 °C) conditions at F/W ratio of 60:40, for detailed analysis. The biogas yields under mesophilic and thermophilic conditions were found to be 21.72% and 22.75% respectively higher compared to uncontrolled CD digesters. Whereas in the case of VW digesters, biogas yields under mesophilic and thermophilic conditions were observed to be 15.20% and 23.25% respectively higher than that of uncontrolled digesters.

Renewable energy (RE) has been identified as an appropriate response to climate change and fossil fuel depletion by many governmental bodies. It has shifted the energy industry towards renewable and sustainable energy systems over the last few decades. This expansion has also increased the demand of specialists for design, installation and maintenance of different RE systems. Most people working in this sector are not well trained or educated enough whereas some of them are not even aware of sustainability. This has shifted towards formulation, model, develop and incorporation of new courses and programmes that would provide sufficient knowledge and skill in the sustainable RE sector. Moreover, the implementation of these new RE courses shouldn’t be limited to engineering level but also focuses on providing basic knowledge to everyone working in this field. Hence, in the present study, two-course structures have been suggested, i.e. general course which would offer basic knowledge and awareness of different RE systems in school level (including primary, elementary, intermediate and secondary) and in the professional programmes (Industrial Training Institute (ITI), diploma, undergraduate, postgraduate and research). Moreover, adequate knowledge would be provided not only in the theoretical field but also in the practical field depending upon the level of programme. Furthermore, undergraduate, postgraduate and research levels students would be provided with a broad knowledge of science, engineering design, planning and implementation of RE systems, while ITI and diploma level would acquire skill development and training in the RE systems.

Compression Ignition (CI) engine is used to generate power for various stationary applications in remote places due to the non-availability of centralised grid connectivity. The burning diesel in CI engine leads to fossil fuel depletion and environmental degradation. Hence, there is a huge demand of generating remote electricity by utilizing available renewable resources with the help of existing CI engines. In this paper biogas (BG) and producer gas (PG) based CI engine technology for remote electricity generation in India has been reviewed. The study is organised in two sections. The first section focused on conceptualizing the influence of these gaseous fuels in CI engine as secondary fuel under dual fuel (DF) mode with diesel/biodiesel as pilot fuel. The effect of various operating parameters on the performance, combustion and emission characteristics have been reviewed. It is evident from the study that induction of gaseous fuel declines the engine performance to some extent, however emission characteristics reported to be enhanced. However, changes in the operating conditions bring with immense scope in the improvement of the engine performance. The study develops a clear understanding on the possibilities of these gases to be used as a primary source for generating rural electricity. In the second section, a discussion on the implementation of such technologies in various rural localities of India considering the biomass potential of the country has been addressed. An exhaustive review is also carried out on various electricity generating units in India powered by BG and PG individually. The literature on use of combined BG and PG units for energy generation are limited and no suitable economic model has been developed considering these gases for rural power generation. This study provides a complete insight to every pros and cons associated with such power generating units and its socio-economic impacts on rural livelihood.

Solar energy is one of the most suitable renewable energy options in India. In the last decade, solar energy installations have received an ample impetus in India due to active initiatives taken by the Indian government. However, the solar energy potential of country’s North-Eastern (NE) part is not utilized effectively so far. In the present study, a comprehensive analysis of the feasibility of installation of a megawatt-level grid-connected solar photovoltaic (SPV) power plant in all the state capitals of NE India is carried out. The climatic data collected from various online sources and NASA climatic database were utilized in designing a 2 MW SPV plant. The theoretical procedure involved in designing the SPV plant is also presented in this study. PVsyst simulation software is used to predict the performance of 2 MW power plants for these eight states of India. From the analysis, it is observed that NE India has an immense potential for installation of solar energy conversion devices and thus it can be harvested economically. It has been observed that locations of Guwahati and Gangtok provide a high performance ratio of 0.855. Aizawl provides the minimum unit cost of electricity generated at a value of 3.88 INR/unit. The analysis also reveals that the Aizawl and Guwahati are the most suitable locations for installation of SPV power plant amongst the NE capitals.

Doping of nonmagnetic impurities in technologically important ZnO has opened a new window for achieving room temperature ferromagnetism, p-type carrier conduction, and enhancement of ferroelectric properties. Here, we report on the confined optical phonon and bandgap engineering in highly oriented Li implanted ZnO thin films. Using resonance Raman scattering condition, the confined longitudinal optical phonon lineshapes in uniaxial hexagonal wurtzite crystal are analyzed in detail using the phonon confinement model. We have demonstrated that phonon confinement model can yield a meaningful result for the interpretation of resonance Raman lineshapes if one considers the contribution of both the E1 (LO) and A1 (LO) modes, particularly while dealing with oriented ZnO thin films. Furthermore, with the increase in Li dose, the bandgap of ZnO is found to show a blue shift, and such blue shift in bandgap is explained using first principles calculation.

The effect of partial replacement of NaCl by KCl on puffing quality parameters on microwave puffed rice was investigated. Reduced sodium and an increased intake of potassium based salt substitutes was formulated and mixed with water and the solution was infused in parboiled rice. The salt infused rice was dried in a fluidised bed dryer till it attains the optimum moisture content for puffing which should be around 10.5%. The salt concentrations were varied such that the total salt concentration was maintained as 3-5% of the total mass of rice. The preconditioned rice obtained by the process was puffed in microwave oven and expansion ratio, percentage of puffing and sensory values were measured. Maximum expansion ratios, percentage of puffing and sensory values were achieved at a mixture of 2.5% NaCl and 1.5% KCl. Sensory evaluation study indicated that salt substitute could be prepared with NaCl and KCl at a proportion of 62.5% of NaCl and 37.5% KCl. It was also obtained that both sodium chloride and potassium chloride has positive effect on expansion ratio and percentage puffing of puffed rice and the effect of sodium chloride is more than that of potassium chloride. However, in case of sensory perception the effect of potassium chloride is more than that of sodium chloride. Hence potassium based salt substitute can be applied to parboiled rice which can significantly reduce the percentage of NaCl maintaining similar taste without affecting the puffing quality.