This paper elaborates on the production of distilled biodiesel of standard EN14214 from waste cooking oil (WCO). Its economic viability is assessed and experimental investigations of a single-cylinder, four-stroke engine using a mixture of distilled biodiesel and diesel of Euro 5 standard are described. The physical and chemical characteristics of biodiesel produced from waste cooking oil were determined. Fuel samples prepared with different percentages of biodiesel and diesel were used to run the engine. We observed the effects of increasing the percentage of biodiesel in the mixture on brake power, brake specific fuel consumption, brake thermal efficiency, and the exhaust emission from the engine. The emission species included O2, CO, CO2, NOx, and SO2. Improved engine performance and reduced emissions from the engine were noticed with blended fuels with 10% and 20% distilled WCO biodiesel mixed with 90% and 80% mineral diesel by volume, respectively. The results of this study indica... [more]

Research and innovation in renewable energy, such as wind and solar, have been supporting the green transformation of energy systems, the backbone of a low-carbon climate-resilient society. The major challenge is to manage the complexity of the grid transformation to allow for higher shares of highly variable renewables while securing the safety of the stability of the grid and a stable energy supply. A great help comes from the ongoing digital transformation where digitisation of infrastructures and assets in research and industry generates multi-dimensional and multi-disciplinary digital data. However, a data user needs help to find the correct data to exploit. This has two significant facets: first, missing data management, i.e., datasets are neither findable because of missing community standard metadata and taxonomies, nor interoperable, i.e., missing standards for data formats; second, data owners having a negative perception of sharing data. To make data ready for data science e... [more]

In order to solve the problems of the high temperature of flue gas, low boiler efficiency, and the high concentration of nitrogen oxide (NOx) emissions for a 330 MW boiler fired with lean coal in a power plant, an adaptation modification by using different type of coals in the power generation unit (including pulverizing system, burners, heating surface, and so on) was carried out. The performances of boilers were tested under different combustion conditions before and after the modification. The results of the test show that the volatile content is higher and easy to burn out, and the combustible content of fly ash and slag are greatly reduced after the change in coal type (while lean coal is changed into bituminous coal). At the same time, the low-temperature economizer can greatly reduce the flue gas temperature, thus increasing the efficiency from 90.36% (lean coal, corrected) to 92.71% (bituminous coal). After the change in coal type (lean coal to bituminous coal) and the shift to... [more]

A smart and decentralized electrical system, powered by grid-connected renewable energy (RE) with a reliable storage system, has the potential to change the future socio-economic dynamics. Climate change may, however, affect the potential of RE and its related technologies. This study investigated the impact of climate change on photovoltaic cells’ temperature response and energy potential under two CO2 emission scenarios, RCP2.6 and 8.5, for the near future (2024−2040) and mid-century (2041−2065) in Togo. An integrated Regional Climate Model version 4 (RegCM4) from the CORDEX-CORE initiative datasets has been used as input. The latter platform recorded various weather variables, such as solar irradiance, air temperature, wind speed and direction, and relative humidity. Results showed that PV cells’ temperature would likely rise over all five regions in the country and may trigger a decline in the PV potential under RCP2.6 and 8.5. However, the magnitude of the induced change, caused b... [more]

This research investigates the most modern approaches to water treatment and recovery in power plants because of the scarcity of water sources and the significance of those sources in enhancing the performance of power-generating cycles. Gas turbines, which use mixes of air and water as the working fluid, provide superior efficiency, high specific power outputs, and reduced investment costs compared to combined cycles. Several different cycles for humidified gas turbines, including cycles of direct water injection, cycles of steam injection, and evaporative cycles that include humidity control towers, have been proposed. Despite this, only a few of these cycles have been put into practice, and even fewer are available for purchase on the market. This work aims to analyze the research and development literature on humidification-based gas turbines and highlight the cycles that have the most significant promise for the long run. In addition, work on development that still has to be carri... [more]

Backfilling technology is not always used by mining enterprises, which is conditioned by technological and economic factors, such as the need for high mining rates and costs for the technological processes of transporting backfill materials from the daylight surface to the mined-out space. This concerns the underground mining of hard coal, which is a strategic energy resource, in the mines of Ukraine. This paper aims to study the effect of leaving the waste bottom rocks in the mined-out space of the longwall face without their drawing to the earth’s surface on the geomechanical state of the rocks surrounding the longwall face. The geomechanical assessment of the stress state of the rock mass surrounding the longwall face, when leaving the waste rocks from the seam bottom rocks in the mined-out space, is performed by the finite element method using the Ansys software package. A geomechanical model has been developed and substantiated, which adequately reflects the mining-geological cond... [more]

Renewable energy communities are considered as key elements for transforming the present fossil fuel-based energy systems of islands into renewable-based energy systems. This study shows how renewable energy communities can be deployed in the Maltese context to achieve higher penetration of residential-scale photovoltaic systems. Case studies for five renewable energy communities in the Maltese LV distribution network have been analyzed in detail. A novel community battery energy storage sizing strategy was proposed to determine the optimal storage capacity at each energy community. The main objective of the community battery storage in each REC is to minimize the reverse power injection in the grid (minimize the total reverse energy and reverse peak power values), as well as to reduce the peak evening electricity demand. The optimal sizes for communal BESSs were determined to be of 57 kWh (EC 1), 55 kWh (EC 2), 31 kWh (EC 3), 37 kWh (EC 4) and 10 kWh (EC 5), respectively. The communit... [more]

In recent years, as an important part of unconventional resources, the effective development of shale oil has been a key area of research in petroleum engineering. Given the widespread availability and low cost of air, the evaluation of air injection in shale reservoirs is a topic worth exploring. This paper analyzes the production performance of different methods of air injection development in the shale reservoir, including air flooding and air huff and puff (HnP), based on full-diameter core air injection experiments. Meanwhile, the characteristics of the residual oil and produced oil are revealed by forming a systematic evaluation method that includes nuclear magnetic resonance (NMR), laser scanning confocal microscopy (LSCM), and gas chromatographic (GC) analysis. The results show that air flooding development is characterized by early gas breakthrough, long oil production period, and “L” shape oil production decline; while air HnP is characterized by first producing gas and then... [more]

The “carbon peak, carbon neutral” goal and the rapid development of new energy sources such as photovoltaic and hydrogen energy have accelerated the decline of the traditional coal industry. Therefore, the coal industry urgently needs to seize the opportunity for coal transformation and achieve high-quality development to improve its competitiveness. This study used a combination of literature analysis and case supplementation to identify 12 influencing factors of coal industry transformation. The DEMATEL method was used to classify the 12 influencing factors into four groups: strong cause, weak cause, strong outcome, and weak outcome. Then, the ISM method was used to construct a multi-level recursive structure of the factors influencing the transformation of the coal industry. The results show that the influencing factors of coal industry transformation can be divided into a three-layer hierarchical structure. Among them, policy traction is the most critical fundamental influence, tec... [more]

Savonius vertical axis wind turbines have simple structures, can self-start in environments with low wind speed and strong turbulence intensity, and can be installed at low costs. Therefore, installation is possible in urban centers with low wind speeds, which may contribute to the construction of a decentralized power system. Savonius wind turbines are operated by drag force, with the blades moving in the same direction as the flow current providing the thrust force and those moving in the opposite direction of the wind being rotated by the drag force. In this study, the Savonius wind turbine design was examined to develop a stable wind turbine for use in urban centers at low wind speeds. The Savonius rotor design variables (aspect and overlap ratios) and blade forms (semi-circular, Bach, and elliptical type) were examined using computational fluid dynamics analysis. Moreover, a rotor capable of providing the target output was designed and maximum rotor efficiency of 18% was realized.... [more]

In this paper, the effects of the fluid-thermal parameters of a porous medium with different values of porosity and permeability on the fluid flow, heat, and concentration parameters were investigated for solar energy applications. The characteristics of the boundary layer, velocity profiles, pressure drop, and thermal and high heat concentration distribution have been analyzed. A developed Brinkman equation for fluid flow and a power law model for thermal conductivity (considering the porosity and permeability factors) were calculated with constant solar heat flux. The numerical model was developed based on the finite element method by the LU algorithm using the MUMPS solver. The Brinkman equations were solved under steady and unsteady states for velocity, pressure, thermal, and concentration distribution effects, respectively. In a porous medium, the normalized temperature of the presented model had an acceptable agreement with the experimental data, with a maximum error of 3%. At co... [more]

It is not uncommon for pump-turbine units in pumped storage power plants to experience load rejections due to the sudden disconnection of the generator from the power grid. Load rejection can suddenly increase the rotating speed of the pump-turbine and cause strong pressure fluctuations in the flow passage of the pump-turbine unit. During load rejection, the strong pressure fluctuations caused by the water hammer effect can cause strong structural vibrations, high stresses and even damage to the turbine runner, head cover, stay ring, bottom ring, head cover bolts and bottom ring bolts. In order to study, in detail, the flow-induced stress characteristics of the prototype pump-turbine unit, and the pressure variations during load rejection in a high-head pumped storage power plant were measured first. Then the measured data were used to set up computational fluid dynamics (CFD) simulations in the entire flow passage of the prototype pump-turbine and to calibrate the simulation results.... [more]

This paper proposes decarbonization pathways for Thailand based on a review of the status of renewable and fossil energies, technology evaluation and scenario studies. Results show that renewable electricity generation needs to grow at a 7.1% average annual growth rate (AAGR) between now and 2050 for the power sector to achieve net-zero by 2050. This would require it to reach 400 TWh, exceeding its technical potential. We propose a more achievable scenario of between 5% and 6% AAGR wherein renewable electricity will grow from 51 TWh to 217−291 TWh between 2020 and 2050. Gas-powered electricity will grow from 127 TWh to 185−111 TWh, requiring carbon capture and storage (CCS) to mitigate 75−45 Mtpa CO2 by 2050. For the transport sector, electric vehicles have the highest decarbonization potential, but they would add 45 TWh of electricity demand by 2050. For the industry sector, installing CCS in existing plants has the highest decarbonization potential. Overall, CCS is a key decarbonizat... [more]

Drying via solar energy is an environmentally friendly and inexpensive process. For controlled and bulk level drying, a greenhouse solar dryer is the most suitable controlled level solar dryer. The efficiency of a solar greenhouse dryer can be increased by using thermal storage. The agricultural products dried in greenhouses are reported to be of a higher quality than those dried in the sun because they are shielded from dust, rain, insects, birds, and animals. The heat storage-based greenhouse was found to be superior for drying of all types of crops in comparison to a normal greenhouse dryer, as it provides constant heat throughout the drying process. Hence, this can be used in rural areas by farmers and small-scale industrialists, and with minor modifications, it can be used anywhere in the world. This article provides a comprehensive analysis of the development of solar greenhouse dryers for drying various agricultural products, including their design, thermal modelling methods, co... [more]

The use of renewable energies, and of geothermal energy in particular, is increasingly being applied in Germany and Europe for the development of new residential districts. The use of geothermal borehole heat exchangers (BHE), in combination with ground-source heat pumps (GSHP), represents an important part of shallow geothermal systems, which are used, among other systems, in urban areas due to their small space requirements. Over the course of planning BHE systems, performance must be determined via the parameters of thermal conductivity, thermal capacity, undisturbed ground temperature, and borehole thermal resistance. These can be identified by the experimental approach known as thermal response testing (TRT). The thermal parameters change due to the influences of the seasonal temperature fluctuations that take place in the ground. In this paper, a pilot double-U BHE heat exchanger field with a depth of 120 m was investigated from this perspective. TRT was carried out using monthly... [more]

Heat stress in deep hot mines is a factor that often determines the possibility of technical mining of natural resources. One of the solutions enabling miners to work in such mines is air cooling. Cooling systems vary, and their selection depends on the type of mine and the mining methods used. Limited air cooling capabilities exist in electric-powered coal mines. The main solution for air cooling is based on movable spot air coolers. Such systems commonly use surface or underground refrigeration plants. An underground refrigeration plant (URP) equipped with compressor chillers does not achieve more than 2.5−3.0 MW of cooling capacity due to the limited heat rejection capacity of return air streams in a typical coal mine. The method discussed in this paper, using mine water to discharge waste heat from the underground refrigeration plant, provides a measurable benefit for optimizing the mine air cooling system. The main purpose of this research is to study the feasibility and effect of... [more]

In recent years, CO2 huff and puff has become one of the most important methods developed for unconventional shale oil reservoirs and has been widely used in all major shale oil fields. However, the microscopic mechanism of CO2 contacting with crude oil is complex, and the change law of the residual oil occurrence after CO2 injection is unclear. In this paper, a micro visualization fluid flow simulation experiment (microfluidic experiment) under high temperatures and high pressure of a shale reservoir was conducted to reveal the micro mechanism of CO2 and crude oil after contact at the microscale. This allows conclusion of more precise results than any experiment conducted in a room environment. Combined with gas−oil two-phase micro flow characteristics, the production mechanisms of crude oil by CO2 huff and puff at the pore scale are clarified, and the change characteristics of the remaining oil occurrence state after CO2 injection are quantified. The results show that CO2 mainly prod... [more]

In this study, we aim to investigate if there is a scaling of the streamwise distance from a wind turbine that leads to a collapse of the mean wake velocity deficit under different ambient turbulence levels. For this purpose, we perform large-eddy simulations of the wake of a wind turbine under neutral atmospheric conditions with various turbulence levels. Based on the observation that a higher atmospheric turbulence level leads to faster wake recovery and shorter near-wake length, we propose the use of the near-wake length as an appropriate normalization length scale. By normalizing the streamwise distance by the near-wake length, we obtain a collapse of the normalized wake velocity deficit profiles for different turbulence levels. We then explore the possibility of using the relationship obtained for the normalized maximum wake velocity deficit as a function of the normalized streamwise distance in the context of analytical wake modeling. Specifically, we investigate two approaches:... [more]

is a species distributed worldwide. Its seeds are used to produce castor oil, which can be used for the production of biofuels; yield improvement can be achieved with elicitors that are substances of biological origin that can induce increased productivity of primary and secondary metabolism, when applied to plants. Salicylic acid (SA) is a natural constituent of plants, and applied exogenously acts as an elicitor. The aim of this work is to evaluate the oil content of castor bean plants elicitated with 900, 600, 300, and 100 µM of salicylic acid and its emissions derived from biodiesel made with the oil in blends (0, 10 and 20%) with commercial fuel in a 296 cc diesel cycle engine; elicitation was foliar sprayed. The oil content increased 39% when 900 µM SA was applied compared to control, and the evaluation of emissions showed the maximum reduction with 20% of Ricinus communis biodiesel (RCB) in all different RPM rates. Otherwise, the use of SA could be a method to increase oil conte... [more]

An important requirement of the power grid with high penetration of renewable energy sources is the mitigation of potential harmonic interactions between different distributed large grid-tie inverters and the mains. This work presents the harmonic interaction between multiple multilevel photovoltaic (PV) inverters based on the well-known T-type neutral-point-clamped inverter (3L-TNPC). The multiple 3L-TNPC is connected in parallel to a common ac bus by using distribution voltage feeders. The analysis is performed by using the Norton equivalence model of each power circuit, its admittance matrix modeling, and the potential overall impedance resonances with the ac grid. The main contribution of this work is the development of a current harmonic injection model of the system operating under a polluted voltage grid for harmonic analysis, while overall filtering design restrictions due to impedance limits based on current and voltage standards are considered. The proposed impedance Norton m... [more]

This paper presents the results of research on the energetic use of self-combusted hemp pellets and co-firing with pine pellets. The tests were carried out with the use of a boiler equipped with a Lester Projekt Company gasifying burner and an automatic fuel feeding system. The boiler is equipped with an additional heat exchanger that enables the simulation of any heat load. The experimental stand so built guaranteed to obtain results adequate to the real operating conditions. The research material consisted of pellets made of waste biomass of the Futura 75 sowing hemp and pine sawdust pellets. The experiment was carried out in five proportions by mass of mixtures of both fuels (C-hemp, P-pine): 0:100 (P100), 25:75 (C25/P75), 50:50 (C50/P50), 75:25 (C75/P25), 100:0 (C100). For each variant, the following were determined: effective boiler power, boiler energy balance, boiler energy efficiency, the volumetric composition of flue gas (carbon monoxide, carbon dioxide, hydrogen, sulfur diox... [more]

The electric vehicle (EV) industry has made significant progress but, in many markets, there are still barriers holding back its advancement. A key issue is the anxiety caused to the drivers by the limited range of current EV models and the inadequate access to charging stations in long-distance trips, as is the case on highways. We propose an intuitive multi-criteria approach that optimally places EV charging stations on highways that (partially) lack such points. The approach, which is applied in an iterative fashion to dynamically evaluate the alternatives, considers a set of practical criteria related to the traffic intensity and the relative location of the charging stations with interchanges, major cities, and existing stations, thus supporting decisions in a pragmatic way. The optimal locations are determined by taking into consideration constraints about the EV driving range and installation preferences to improve the operation of the highway while ensuring reasonable cost of i... [more]

Excessive regional differences in energy consumption have led to inequality and energy poverty. It is essential to clarify the factors of energy consumption convergence to solve this problem. We use the spatial convergence model to analyze the convergence characteristics and conditions of China’s natural gas consumption from 2005 to 2017. The results of spatial absolute convergence show that there is absolute convergence of natural gas consumption in China, and the economic competition among provinces slightly hinders the convergence. Furthermore, based on the spatial Durbin model and the spatial conditional convergence model, we found that insufficient pipe network construction and the price difference caused by provincial borders are the main factors hindering the flow of natural gas, which also restricts the spatial convergence of natural gas consumption. The development of the tertiary industry and the improvement of purchasing power will help accelerate the convergence of natural... [more]

The use of waste incineration with energy recovery is a matured waste-to-energy (WtE) technology. Waste incineration can reduce the volume and mass of municipal solid waste significantly. However, the generation of high volumes of polluting flue gases is one of the major drawbacks of this technology. Acidic gases are constituents in the flue gas stream which are deemed detrimental to the environment. The wet flue gas desulphurization (FGD) method is widely employed to clean acidic gases from flue gas streams, due to its high efficiency. A major setback of the wet FGD technology is the production of wastewater, which must be treated before reuse or release into the environment. Treating the wastewater from the wet FGD presents challenges owing to the high level of contamination of heavy metals and other constituents. Membrane distillation (MD) offers several advantages in this regard, owing to the capture of low-grade heat to drive the process. In this study the wet FGD method is adopte... [more]

Coke-making technology utilises two systems for charging the coke oven chambers with coal—a stamp-charged system (stamp-charging) and a gravity charged system (top charging). The presented study examines the impact of selected coal properties on the effectivity of the stamping operation by measuring the bulk density of the obtained stamped coal cake. An empirical mathematical model was developed that allows the forecasting of the coal cake density based on the most frequently assessed coal parameters, such as volatile matter, ash, moisture and particle size parameters, as well as the stamping operation parameter—cumulative stamping energy. The obtained results showed that the density of the stamped coal cake increases with the increase in the stamping energy (53.3 kg/m3 increase, for increase in natural logarithm value of 1), RRSB specific coal particle diameter d′ (6.4 kg/m3 increase, for each 0.1 mm increase in d′), ash content (8.9 kg/m3 increase, for 1% point increase) and moisture... [more]