This article presents the potential of heat recovery from wastewater with an example of a wastewater treatment plant (WWTP) in Mokrawica, which is located in the West Pomeranian region of Poland. A thorough literature review discusses the relevance of the topic and shows examples of heat recovery conducted with heat pumps. Raw and treated wastewater are mostly used as heat sources, with the latter achieving higher thermal capacities. Heat recovery from a biological treatment process is rarely implemented and requires more detailed studies on this subject. The proposed methodology for estimating possible heat recovered from wastewater, requiring heating and cooling capacities, as well as the coefficient of performance (COP) of a heat pump, is based on only three parameters: wastewater volumetric flow, wastewater temperature, and the required temperature for heating or air-conditioning. The heat recovery potential was determined for different parts of WWTP processes, i.e., the sand box,... [more]

The worldwide population growth and the technological advancements reported in the past few years have led to an increase in the production and consumption of energy. This has increased greenhouse gas (GHG) emissions, the primary driver of climate change. As a result, great attention has been paid to sustainable and green energy sources that can replace or reduce reliance on non-sustainable energy sources. Among the different types of renewable energy sources currently available, bioenergy has been reported as an attractive resource mainly due to its low cost and great availability. Bioenergy can be produced from different biomass sources and converted into biofuels or value-added products through thermochemical, biochemical, and chemical processes. Gasification is a thermochemical process commonly used for bioenergy production, and it is particularly attractive mainly due to its high efficiency. However, its performance is influenced by parameters such as type of feedstock, size of bi... [more]

Combining biomass-fired power generation with CO2 capture and storage leads to so-called negative CO2 emissions. Negative CO2 emissions can already be obtained when coal is co-fired with biomass in a power plant with CCS technology. The need for bioenergy with CO2 capture and storage has been identified as one of the key technologies to keep global warming below 2 °C, as this is one of the large-scale technologies that can remove CO2 from the atmosphere. According to the definition of bioenergy with CO2 capture and storage, capturing and storing the CO2 originating from biomass, along with the biomass binding with carbon from the atmosphere as it grows, will result in net removal of CO2 from the atmosphere. Another technology option for CO2 removal from the atmosphere is direct air capture. The idea of a net carbon balance for different systems (including bioenergy with CO2 capture and storage, and direct air capture) has been presented in the literature. This paper gives a background... [more]

The Late Paleozoic is an important epoch of coal-bed accumulation in the North China, particularly in its western segment, where a world-class coal field has been found and exploited for three decades. Coal-bearing layers recorded rapid Late Carboniferous to Early Permian sea-level rise that led to the evolution of the shallow marine tidal flat basin, followed by regression that resulted in the formation of deltaic facies. However, little attention has been paid to the tectonic factors that assisted in the coal accumulation processes, which have been demonstrated worldwide to be pivotal. In this study, we evaluate the significant influence of southward subduction of the middle segment of the Paleo-Asian Ocean (PAO) during Carboniferous to Early Permian deposition of coal-bearing neritic to deltaic successions in the western North China Block (NCB). We pinpoint a direct link between basin-filling evolution of the northwestern Ordos Basin and the progressive uplift of the Inner Mongolia... [more]

The lubricating oil industry is widespread in the world, but getting rid of the used oils has become an environmental concern. Lubricating oils are used in industries and cars but potentially contaminate groundwater after use. This research uses montmorillonite clay to refine old oil treated with acetic acid. Compared to more conventional procedures, the suggested strategy for treating waste oil is more cost-effective due to the relatively inexpensive cost of the acid and the modest process conditions. Water content, sediment content, density, flash and fire points, viscosity, viscosity index, total acid and base number, pour points, and refractive index were among the physicochemical parameters of the treated oil that were examined as a result of this treatment. We analyzed the oils using Fourier transform infrared spectroscopy (FTIR) and atomic absorption spectrometry (AAS). New oil (10w 40), old oil, oil treated with acetic acid, and montmorillonite clay were all put through their p... [more]

The Galapagos Islands have been declared a World Heritage site due to their unique biodiversity, which makes them a living museum and a natural laboratory for humankind. However, to fulfill the energy needs of its habitants and foreign visitors, the islands have depended on fossil fuel energies that have produced levels of lead and chemical agents that are affecting the islands’ air quality, flora, and fauna. Therefore, zero-carbon initiatives have been created to protect the islands, wherein solar and wind power plants have been studied as reliable alternatives. In this way, Geographical Information Systems based on Multicriteria Decision Methods constitute a methodology that minimizes the destruction and disturbance of nature in order to assess the best location for the implementation of these alternative energy sources. Therefore, by exploring the geographical information along with the Analytical Hierarchical Processes and the Ordered Weighted Average methods, it was possible to id... [more]

In South Korea, Renewable Energy Sources (RES) have been increasing with the application of energy policies, such as Feed in Tariff (FIT) and the Renewable Portfolio Standard (RPS). However, a rapid increase in RES supply leads to an uncertain power supply due to the intermittent output of RES. A representative example is the curtailment of Wind Turbines (WT), which frequently occurs in Jeju Island, South Korea. The proportion of RES power on Jeju Island is 67%, and there are cases where WT is curtailed among the operable sections to maintain the balance of power supply and demand. This paper applies Power-to-Gas (P2G) technology to hydrogenate, store, and utilize unused power to solve this problem. In this paper, Aewol-eup in Jeju Island is selected as a target site for case study. An Integrated Energy System (IES) for various energy operations is designed to control RES output. This paper proposes the optimal facility configuration and finally drives the optimal design and operation... [more]

The testing of roller rotational resistance is essential in improving and searching for new design solutions to reduce the energy consumption of belt transport. The publication presents three methods of testing idler rotational resistance using various laboratory test stands designed and built by the authors. According to the first method, the test consists of applying torque to the roller axis and measuring the resistance force to rotate the roller axis. According to the second method, the test consisted of speeding up the idler, measuring the free stopping time and determining the moment of resistance to rotating the idler. The third stand enables the simulation of loads recommended by the PN-M-46606: 2010 and DIN 22112 standards, as well as operational loads, while measuring the dynamic rotational resistance. The comparative tests used two rollers different in terms of bearing type, hub type and quality of craft. The research object was ø133 × 465 rollers, most commonly used in the... [more]

One of the promising ways to increase fuel and modern gas turbine energy efficiency is using cyclic air intercooling between the stages of high- and low-pressure compressors. For intercooling, it is possible to use cooling in the surface heat exchanger and the contact method when water is injected into the compressor air path. In the presented research on the cooling contact method, it is proposed to use a thermopressor that implements the thermo-gas-dynamic compression process, i.e., increasing the airflow pressure by evaporation of the injected liquid in the flow, which moves at near-sonic speed. The thermopressor is a multifunctional contact heat exchanger when using this air-cooling method. This provides efficient high-dispersion liquid spraying after isotherming in the high-pressure compressor, increasing the pressure and decreasing the air temperature in front of the high-pressure compressor, reducing the work on compression. Drops of water injected into the air stream in the the... [more]

This paper presents an analysis of the possibility of determining the geometric deviations of large crankshafts of engines using both conventional and alternative fuels. Experimental tests were carried out on a test stand adapted to measure crankshafts seated with their main journals on a set of fixed supports with the possibility of height positioning and using a reference measuring system. A comparative assessment of the results was made for a selected crankshaft using the intercorrelation factor ρ, whose value ranged from 0.8982 to 0.9751. It was concluded that the proposed procedures can be useful in assessing of the geometric condition of the crankshafts with axial position deviations and with limited possibilities of their detection resulting from the adopted support conditions with a set of supports positioned at different heights. Experimental tests were supplemented with FE-analyses of the crankshaft supported at multiple locations and loaded with deviations in the position of... [more]

Natural gas is an indispensable resource not evenly distributed in the world. The gas supply chain is characterized by large imbalances between supply and demand, where the underground gas storage (UGS) application plays a key role for creating strategic reserves, taking advantage of geological structures. On the contrary, human activities will require clean energy with near-zero greenhouse gas emissions to be environmentally viable. A key element of this strategy is the carbon capture and storage (CCS) application useful for confining CO2 into the geosphere to reduce anthropogenic emissions. The development of appropriate injection methods and long-term monitoring systems for leak detection of the underground storage of natural gas and CO2 is important to prevent negative effects, such as ground deformations and micro seismic events. In this work, a variety of monitoring applications were gathered and critically analyzed for a total of 60 scientific contributions spanning the world. T... [more]

Leading to the enhancement of smart grid implementation, the peer-to-peer (P2P) energy transaction concept has grown dramatically in recent years allowing the end-users to successfully exchange their excess generation and demand in a more profitable way. This paper presents local energy market (LEM) architecture with various market strategies for P2P energy trading among a set of end-users (consumers and prosumers) in a smart residential locality. In a P2P fashion, prosumers/consumers can export/import the available generation/demand in the LEM at a profit relative to utility prices. A common portal known as the transactive energy market operator (TEMO) is introduced to manage the trading in the LEM. The goal of the TEMO is to develop a transaction agreement among P2P players by establishing a price for each transaction based on the price and trading demand provided by the participants. A few case studies on a location with ten residential P2P participants validate the performance of t... [more]

In this study, the crude oil spot price is forecast using Bayesian symbolic regression (BSR). In particular, the initial parameters specification of BSR is analysed. Contrary to the conventional approach to symbolic regression, which is based on genetic programming methods, BSR applies Bayesian algorithms to evolve the set of expressions (functions). This econometric method is able to deal with variable uncertainty (feature selection) issues in oil price forecasting. Secondly, this research seems to be the first application of BSR to oil price forecasting. Monthly data between January 1986 and April 2021 are analysed. As well as BSR, several other methods (also able to deal with variable uncertainty) are used as benchmark models, such as LASSO and ridge regressions, dynamic model averaging, and Bayesian model averaging. The more common ARIMA and naïve methods are also used, together with several time-varying parameter regressions. As a result, this research not only presents a novel an... [more]

Offshore wind energy is a sustainable renewable energy source that is acquired by harnessing the force of the wind offshore, where the absence of obstructions allows the wind to travel at higher and more steady speeds. Offshore wind has recently grown in popularity because wind energy is more powerful offshore than on land. Prior to the development of floating structures, wind turbines could not be deployed in particularly deep or complicated seabed locations since they were dependent on fixed structures. With the advent of floating structures, which are moored to the seabed using flexible anchors, chains, or steel cables, wind turbines can now be placed far offshore. The deployment of floating wind turbines in deep waters is encouraged by several benefits, including steadier winds, less visual impact, and flexible acoustic noise requirements. A thorough understanding of the physics underlying the dynamic response of the floating offshore wind turbines, as well as various design princi... [more]

In this paper, a techno-economic investigation of a small-scale solar water pumping system combined with power generation is conducted numerically. Irrigation and power production for a typical small-size citrus farm located in southern Iran is simulated. The system consists of monocrystalline photovoltaic panels (CS3K-305MS, 305 W), absorbent glass material batteries (8A31DT-DEKA, 104 Wh), inverters (SMA Sunny Boy 2.0, 2000 W), and a pumping storage system. The key concepts of water shortage probability (WSP) and loss of power supply probability (LPSP) are used in conjunction with users’ tolerances and sizing of the system. A genuine MATLAB code was developed and validated before the simulations. A specific electricity consumption pattern for a rural home and a variable irrigation water profile were considered. The main objective of the study is to size a system that provides both electricity for domestic use of a home as well as the energy required for running the irrigation pumps wi... [more]

China is confronted with the dual constraints of economic transformation and carbon emission reduction. As the digital economy is a key force in promoting economic transformation and optimizing industrial structure, it is crucial to analyze the digital economy’s impact on carbon emission reduction from the perspective of energy consumption and industrial value chain implications. We selected data from 251 prefecture-level cities and above in China from 2011 to 2019 as research samples, measured the development level of the digital economy using the entropy value method, and constructed relevant regression models based on two-way fixed effects, intermediary analysis, and moderation analysis. The research reveals that: (1) The digital economy has a significant contribution to carbon emission efficiency, and there are significant regional heterogeneity and city size differences; (2) The digital economy can improve carbon emission efficiency by reducing energy consumption. (3) From a value... [more]

Several research works have investigated the direct supply of renewable electricity to electrolysis, particularly from photovoltaic (PV) and wind generator (WG) systems. Hydrogen (H2) production based on solar energy is considered to be the newest solution for sustainable energy. Different technologies based on solar energy which allow hydrogen production are presented to study their benefits and inconveniences. The technology of water decomposition based on renewable energy sources, to produce hydrogen, can be achieved by different processes (photochemical systems; photocatalysis systems, photo-electrolysis systems, bio-photolysis systems, thermolysis systems, thermochemical cycles, steam electrolysis, hybrid processes, and concentrated solar energy systems). A comparison of the different methods for hydrogen production based on PV and WG systems was given in this study. A comparative study of different types of electrolyzers was also presented and discussed. Finally, an economic asse... [more]

A number of measures to diversify its energy supply sources and reduce its dependence on imported energy sources has been taken by the EU. These include pursuing new energy sources, such as renewable energy and liquefied natural gas; increasing the storage capacities; and investing in interconnectors and other infrastructure. However, these actions require long-term adjustment, while there is a need to find an option to meet the energy needs at a moment. One possible option is to utilize seed production wastes for energy production. This research paper aims to investigate the potential of utilizing seed production wastes (SPWs) for energy production in continental Croatia, and assess its feasibility. Eight different SPWs were used in this research, where their energy characteristics were determined and the theoretical thermal potential was calculated if they are used as raw material in the production of thermal energy through biomass and cogeneration power plants, or in biogas power pl... [more]

The harmless disposal of spent cathode carbon blocks (SCCBs) has become an urgent issue in the primary aluminum industry, and the disposal of SCCBs by co-combustion in pulverized coal boilers is expected to be the most effective treatment method. A muffle furnace at 815 °C was used in this study to perform a co-combustion experiment of meager coal and SCCBs. The ash fusion characteristics (AFTs), microscopic morphology, and minerals composition of co-combustion ash were characterized. The interaction mechanism of different mineral components and the change in AFTs and viscosity-temperature characteristics were investigated using FactSage software. Results show that the change in the ash deformation temperature (DT) is correlated linearly with the SCCB addition ratio, whereas other characteristic temperatures exhibit a nonlinear relationship. The contents of SiO2, Al2O3, and Na2O collectively determine the DT in the ash, and the influence degree from high to low is in the order of SiO2,... [more]

In Poland’s largest mining district, the Upper Silesian Coal Basin, there is a growing interest in resource development by small operators. Some concession areas are not yet directly affected by the mining industry. The objects of this research are two such areas and the goal is to determine a load of heavy metals (HM) in soils prior to mining projects and to assess the extent of their contamination at this stage. The metals studied were Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, while HM contamination was assessed using the Contamination Factor (CF), Contamination Degree (CD), Pollution Load Index (PLI), and Geoaccumulation Index (Igeo). The Ecological Risk Potential Index (ER) and Comprehensive Potential Ecological Risk Index (PERI) were also employed. The pre-mining areas are close to an area where mining was terminated before 2000. For this area, we performed the same set of analyses as for the pre-mining areas studied. HM concentration levels and pollution indices in post-mining areas ar... [more]

The effect of intrinsic metal mineral elements in the combustion process of pulverized coal on the formation and transformation mechanism of PM was investigated in a drop-tube furnace in air atmospheres at 1200 °C, which laid a solid foundation for the control of particulate pollutants. The results show that reducing the evaporation of mineral elements or the generated PM1 aggregating to form PM1−10 or particles bigger than 10µm can reduce the emission of PM1 in the coal combustion process. The amount of PM0.2, PM0.2−1, PM1−2.5 and PM2.5 produced by the raw coal-carrying Mg are reduced by 36.7%, 17.4%, 24.6% and 21.6%, respectively. The amount of PM10 is almost unchanged. The addition of Mg increases the viscosity of submicron particles effectively, making it easier to aggregate and bond together to form ultra-micron particles. The amount of PM0.2, PM0.2−1, PM1−2.5, PM2.5 and PM10 produced by the raw coal-carrying Ca are reduced by 36.3%, 33.0%, 42.8%, 38% and 17.7%, respectively. The... [more]

The article reviews the existing methods of increasing the energy efficiency of electric transport by analyzing and studying the methods of increasing the energy storage resource. It is grouped according to methods, approaches, and solutions. The most effective methods and ways of their implementation are identified. General methods of increasing energy efficiency, methods of increasing recuperation during braking, methods of energy-efficient energy consumption, the use of energy-saving technologies, and improving the energy efficiency of the traction drive are considered. The purpose of this work is to identify the main operating factors on the basis of a critical review of existing methods for assessing the technical condition of batteries and experimental results on the degradation of lithium-ion batteries. Using the great experience of the research group in the field of modeling, diagnostics, and forecasting of life of electric cars, as well as their intellectual management, the ne... [more]

The application of rapeseed oil (RO) blends with diesel fuel and/or alcohols and/or ethers is known to significantly affect the combustion process. Aiming to further investigate the effects of rapeseed oil in a blend with diethyl ether (DEE) on this process, the coefficient of variation of the mean indicated pressure (COVMIP) of a 2.5l direct injection diesel engine was calculated. The analysis of the experimental results revealed the repeatability of the combustion process variability of diesel fuel (DF), rapeseed oil (RO), and DEE/RO blends containing up to 20% DEE. In these cases, the COVMIP does not exceed 4%. Additionally, it became obvious that for a higher content of DEE in blend with RO, the cyclic repeatability of the mean indicated pressure (MIP) was reduced. Thus, the values of COVMIP for fuels containing 30 and 40% of DEE by vol. in blend with RO were even three times higher than the values obtained for the reference fuel i.e., DF. The results indicate that the increased co... [more]

Power generation using small wind turbines connected to AC grids has been gaining attention and contributions in recent years. As small wind turbines are connected to remote areas as support energy systems, there are not extensive contributions connecting those small turbines to AC grids. This paper presents the integration of a small wind generation system which is AC-grid-connected. The system is composed of a 160 W commercial small wind turbine with a permanent magnet synchronous generator and a 140 W Texas Instruments (Dallas, TX, USA) development kit devoted to connecting photovoltaic panels to AC grids. Several experimental tests were developed to characterize the devices, e.g., to obtain the power−current curves of the synchronous generator. Moreover, a mathematical model of the flyback converter is developed in detail in order to design a new converter controller. All the control capacity of the development kit is used to extract the maximum power of the synchronous generator,... [more]

An experimental study was conducted to investigate the effect of high-ratio biodiesel and pure biodiesel on the emissions and performance of Euro4-compliant vehicles. The tested fuels were diesel fuel, biodiesel with a ratio of 30% by volume (B30), biodiesel with a ratio of 50% (B50) and pure biodiesel FAME (B100), while the tested vehicle is of the Euro4-compliant standard currently available in the Indonesian market. In this study, tests on emissions, performance and fuel economy were conducted based on the international standard of the UN ECE R83-05, adopted as UN ECE R-85 and UN ECE R-101 respectively. This study also investigated the effect of the carbon-to-hydrogen ratio on the carbon balance formula. Here, the paper proposed a modified R101 carbon balance formula to calculate the fuel economy for high-ratio and pure biodiesel fuels. The results showed that biodiesel had lower CO, HC and particulate emissions, while NOx emissions were higher compared to diesel fuel. However, pure... [more]