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Abstract Castor seed is an important oil seed crop of dryland agriculture. To estimate the energy needs of this crop, two experiments were conducted with three tillage treatments under two farming systems, namely bullock and tractor farming. Under all the selected tillage treatments both for tractor and bullock farming systems, it was found that threshing, harvesting, manual weeding and seed bed preparation were the energy intensive operations. No-tillage treatments was found not only the least energy consuming package of practices but also resulted i n a comparatively high output-input energy ratio despite higher weed intensity. Further, tractor cultivation consumed a higher amount of energy as compared to bullock cultivation but did not result in higher production. The farmer may, therefore, continue with bullock cultivation unless he were to cover larger areas which cannot be commanded by the bullock power resources available to him.

Abstract Biodiesel has gained the forefront of our focus on renewable transportation fuels. This article provides a comprehensive review on the sources used as feedstock and their classification based on generation or type (edible, non-edible, waste resources and animal fats) along with a variety of classical and modern oil extraction techniques. The technical aspects of the various biodiesel production methods currently implemented to the best of our knowledge are discussed here, which include in-situ biodiesel production, both catalysed (homogeneous and heterogeneous systems) and uncatalysed classical production approaches, with emphasis on how each of these approaches are affected by their reaction parameters. The review also highlights the observed drawbacks of each process with a view to assessing the implementation of supercritical and superheated technologies as an alternative, economically feasible advancement. Supercritical process (SCP) has shown great prospect in the obtainment of high quality biodiesel from a wide range of high to low grade feedstock with minimal impacts on the presence of water or FFAs (free fatty acids). From available literature it is shown that these do not affect the process significantly, and various other supercritical fluids such as methyl acetate, tert-butyl methyl ether (MTBE) and dimethyl carbonate can also be used to avoid glycerol formation. The process however, suffers from high initial implementation cost being the most prominent drawback, among others like thermal degradation of the fuel. Another promising technique, the superheated vapour technology (SHV) has emerged as an alternative, with limited literature proving the superiority of either of these processes to be inconclusive. In future works, researchers need to look into various aspects such as developing a spiral reactor for heat recovery, using software based optimization for eliminating redundant experiments analysing production cost for industrial scale-up and improving the fuel’s oxidative stability by adding antioxidants for convenient long-term storage and use.

Abstract Removing water from various feeds is usually carried out using evaporation process especially in food industry. Due to the high latent heat of water, this unit operation results in consumption of unacceptable amount of energy. Finding low energy consuming processes which could be replaced with this process is still a challenge. The processes with no phase inversion may be considered for concentration purposes with reasonable energy consumption in comparison with the other various separation procedures. Reverse osmosis and most of the other membrane technologies are separation techniques without any change in the phase and therefore consume low amount of energy. Concentrating the sugar thin juice in the classical sugar manufacturing procedure is carried out using conventional evaporation. Reverse osmosis membranes may be used as a pre-concentration step to partially separate water from the sugar thin juice in combination with this part of the plant. Final concentration and thick juice preparation for crystallization may be carried out in the evaporation unit. In this study, membranes were employed for sugar thin juice concentration using a two-stage reverse osmosis process in two different arrangements. The energy consumption was calculated and compared for conventional evaporation versus reverse osmosis combined with evaporation. The results indicate that the employment of revers osmosis membranes for concentrating the sugar thin juice leads to sensibly lower energy requirements. Furthermore, there is no thermal loss of sugar in the membrane process.

Abstract In this paper, a three-dimensional numerical simulation was carried out to characterize a high-ash coal gasification in a pressurized, oxygen-blown, two-stage E-Gas entrained flow gasifier. The Tabas coal was used as a high-ash feedstock, with 32 wt% ash and was compared with the Illinois #6 low-ash coal, with 10 wt% ash. The computational model was conducted in ANSYS FLUENT 14 based on the conservation equations described in the Eulerian–Lagrangian approach. Also, four heterogeneous combined with seven homogeneous reactions were solved via the finite rate and eddy-dissipation/finite rate model, respectively. Two different parametric analyses were conducted to characterize the gasification process in the E-Gas gasifier. These analyses cover the effects of the O2/Coal ratio and coal slurry water content on the gasifier performance characteristics such as the exit temperature, main species mole fractions, carbon conversion, high heating value, yield syngas fraction and cold gas efficiency. It was found that using the higher ash content coal decreases the cold gas efficiency about 5%, limits the gasifier economical operating range, and reduces the exit temperature, yield syngas and total higher heating value.

Abstract The general objective of the investigation described in this article is the experimental testing of solar assisted dryers reported earlier. The tests show good technical results with a conventional energy consumption decrease of 27–80% and an average solar system efficiency of approx. 40%. From the experimental results, it can also be concluded that, with controlled removal of the moist air, improved product quality, significant reduction in drying time and mass losses, etc. result. The introduction of solar dryers seems to be a promising way for drying various agricultural products.

Abstract In this work, the combustion and emission fundamentals of high n-butanol/diesel ratio blend with 40% butanol (i.e., Bu40) in a heavy-duty diesel engine were investigated by experiment and simulation at constant engine speed of 1400 rpm and an IMEP of 1.0 MPa. Additionally, the impact of EGR was evaluated experimentally and compared with neat diesel fuel (i.e., Bu00). The results show that Bu40 has higher cylinder pressure, longer ignition delay, and faster burning rate than Bu00. Compared with Bu00, moreover, Bu40 has higher NOx due to wider combustion high-temperature region, lower soot due to local lower equivalence ratio distribution, and higher CO due to lower gas temperature in the late expansion process. For Bu40, EGR reduces NOx emissions dramatically with no obvious influence on soot. Meanwhile, there is no significant change in HC and CO emissions and indicated thermal efficiency (ITE) with EGR until EGR threshold is reached. When EGR rate exceeds the threshold level, HC and CO emissions increase dramatically, and ITE decreases markedly. Compared with Bu00, the threshold of Bu40 appears at lower EGR rate. Consequently, combining high butanol/diesel ratio blend with medium EGR has the potential to achieve ultra-low NOx and soot emissions simultaneously while maintaining high thermal efficiency level.

Heat transfer and flow characteristics of the sinusoidal-corrugated channel with Al2O3-water nanofluid are analyzed by a 2-D numerical simulation. A parametric study method is used to analyze the performance of sinusoidal-corrugated channel in practical applications like plate-fin compact heat exchangers. The effects of channel height, channel length, wave length, wave amplitude, and phase shift at different Reynolds numbers (6000–22,000) and nanoparticle volume fractions (0–4%) are evaluated. Nusselt number and Darcy friction factor are considered as performance parameters. It is found that the channel height and wave amplitude have the highest influences on Nusselt number and friction factor values, respectively. Also, the results show that the nanofluid flow inside the sinusoidal-corrugated channels offers higher values of Nusselt number compared to the base fluid, while the friction factor of both the nanofluid and the base fluid gets almost the same values. Finally, correlations are proposed to predict Nusselt number and friction factor of the water and Al2O3-water nanofluid flows in the sinusoidal-corrugated channels.

Abstract The technology landscape around distributed generation continues to evolve in response to increasing demand for high-efficiency, low-emission, low-cost power generation. While emerging distributed power technologies, such as solid oxide fuel cells (SOFCs), continue to advance, they still face challenges due to their high capital costs, and shorter lifetimes that typically arise from electrochemical stack performance degradation at high operating temperatures (>750 °C). Recent advancements in protonic ceramic fuel cells (PCFCs) offer the potential to mitigate drawbacks of their higher temperature SOFC counterparts by enabling lower operating temperatures (550 °C–600 °C) with acceptable power densities. The present work leverages the recent progress in protonic ceramic cell and stack technology development to generate viable system configurations and evaluate the energetic performance potential of PCFC-based systems for stationary power generation. Process system engineering of two water-neutral system concepts, which provide 25 kW of electric power and process hot water, are presented and evaluated through sensitivity studies. Stack design parameters are altered and used to gauge the effect on system performance characteristics, including fuel cell stack and balance-of-plant sizing requirements, and electric and cogeneration efficiencies. The study finds that the potentially high per-pass fuel utilization capability of PCFC stacks could enable unprecedented electric efficiencies approaching 70% without hybridization with other prime movers.

Abstract The energy efficiency of water supply systems can be increased through the recovery of hydraulic energy implicit to the volumes of water transported in various stages of the supply process, which can be converted into electricity through hydroelectric recovery systems. Such a process allows the use of a clean energy source that is usually neglected in water supplies, reducing its dependence on energy from the local network and the system’s operation costs. This article evaluates the possibilities and benefits of the use of water supply facilities, structures and equipment for hydraulic energy recovery, addressing several applicable hydroelectric models. A real case study was developed in Brazil to illustrate the technical, economic and environmental aspects of hydropower recovery in water supply systems.