Optimization of substation grounding grid design for horizontal and vertical multilayer and uniform soil condition using Simulated Annealing method.

Grounding systems are critical in safeguarding people and equipment from power system failures. A grounding system's principal goal is to offer the lowest impedance path for undesired fault current. Optimization of the grounding grid designs is important in satisfying the minimum cost of the grounding system and safeguarding those people who work in the surrounding area of the grounded installations. Currently, there is no systematic guidance or standard for grounding grid designs that include two-layer soil and its effects on grounding grid systems, particularly vertically layered soil. Furthermore, while numerous studies have been conducted on optimization, relatively limited study has been done on the problem of optimizing the grounding grid in two-layer soil, particularly in vertical soil structures. This paper presents the results of optimization for substation grounding systems using the Simulated Annealing (SA) algorithm in different soil conditions which conforms to the safety requirements of the grounding system. Practical features of grounding grids in various soil conditions discussed in this paper (uniform soil, two-layer horizontal soil, and two-layer vertical soil) are considered during problem formulation and solution algorithm. The proposed algorithm's results show that the number of grid conductors in the X and Y directions (Nx and Ny), as well as vertical rods (Nr), can be optimized from initial numbers of 35% for uniform soil, 57% for horizontal two-layer soil for ρ1> ρ2, and 33% for horizontal two-layer soil for ρ1< ρ2, and 29% for vertical two-layer soil structure. In other words, the proposed technique would be able to utilize square and rectangle-shaped grounding grids with a number of grid conductors and vertical rods to be implemented in uniform, two-layer horizontal and vertical soil structure, depending on the resistivity of the soil layer.

Effects of power station and abattoir on PAH input into sediments of Oji River: ecological and human health exposure risks.

This study investigated the concentration and sources of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Oji River due to point sources of pollution from abattoir and power plant and determined the ecological and human health risks associated with the PAHs in the sediments. Oji River in Nigeria receives contaminants from anthropogenic activities relating to waste tires used in singeing cow meats in abattoir and preparing hides and skin for local consumption. It also receives contaminants from power distribution station where the defunct coal power plant used to be situated. These activities have the potential to release polycyclic aromatic hydrocarbons that could accumulate in the river sediments. The PAHs were measured using gas chromatography-mass spectrometry (GC-MS). This study found that the abattoir is responsible for the occurrence of benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene in the sediments around the abattoir. The occurrence and distribution of PAHs around the area affected by the power station was profound as among all the 16 priority PAHs; only naphthalene benzo[g,h,i]perylene, dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene were not detected. The five-member ring PAHs were predominant in this section of the river affected by power station. Ecological risks of the PAHs due to the effects of the power station are significant. The total toxicity equivalence (TEQ) of the PAHs upstream the abattoir is insignificant but significant around the abattoir and within the area impacted by the power station. The values of the hazard index (HI) and risk index (RI) indicate insignificant carcinogenic and non-carcinogenic human health risks in all the locations except the area within the influence of the power station where there are insignificant non-carcinogenic risks but significant carcinogenic risks.

Occupational Health and Safety and Turnover Intention in the Ghanaian Power Industry: The Mediating Effect of Organizational Commitment.

This study aimed at investigating the effect of occupational health and safety (OHS) on employee's turnover intention (TI) with the mediating effect of organizational commitment (OC) in the Ghanaian power industry. Methods. With stratified sampling technique, 350 participants were selected to participate in the study with standardized quantitative questionnaires to measure the variables involved in the study and SmartPLS 3-structural equation modeling technique to analyze the data. Results. The results showed that (1) occupational health and safety and turnover intention are negatively related (ß = 0.245, p < 0.05); (2) there exists a positive relationship between occupational health and safety and organizational commitment (ß = 0.820, p < 0.05); (3) organizational commitment and turnover intention are negatively related (ß = 0.640, p < 0.05); and (4) organizational commitment significantly mediates the relationship between occupational health and safety and turnover intention (indirect effect = -0.53 and direct effect = -0.25, p < 0.05). Conclusion. Employees satisfied with the health and safety system of their organization tend to be committed to their organization and have low turnover intention, and vice versa.

Multi-criteria of wind-solar site selection problem using a GIS-AHP-based approach with an application in Igdir Province/Turkey.

Sustainable sources like wind, solar, and geothermal power are defined as a clean source of renewable energy which has a less harmful impact on the environment than other energy sources such as coal, natural gas and oil. Turkey is one of the energy-importing countries where air pollution has been become an inevitable environmental concern. Thus, investments on sustainable sources have been developed rapidly in recent years in Turkey. This paves the way for studying a site selection problem considering both solar and wind energy in Igdir Province located in the east part of Turkey. In the literature, there are many studies on solar-wind energy to select a desirable site for both energy sources, and many solution techniques have been proposed dealing with this problem. In this study, one of multi-criteria decision-making methods named analytical hierarchy process (AHP) and geographical information systems (GIS) are used to determine suitable site selection for solar-wind energy investigating four counties of Igdir: Tuzluca, Igdir Central, Karakoyunlu and Aralik. The aim of this work is first to investigate possible locations for solar-wind power plant installation using a mapping method, GIS, and then, AHP is applied to the problem to obtain optimum areas for both solar-wind energy. Also, more accurate results are provided comparing results of two methods, GIS and AHP. The results reveal that 524.5 km2 for solar power plant and 147.2 km2 for wind turbine are suitable while only 49.1 km2 is suitable for solar-wind power plan installation.

Effect of installed capacity size on environmental efficiency across 528 thermal power stations in North China.

Thermal power plants are the main source of carbon dioxide emissions in China. Beijing-Tianjin-Hebei and their neighborhood provinces are the most polluted regions in China. Environmental efficiencies of 528 thermal power plants were evaluated through metafrontier epsilon-based measure, which aimed to overcome the invalid inferences of radial or non-radial model. We also analyzed the heterogeneity of environmental efficiency across different regions by considering environmental technology differences. Bootstrap regression was used in order to testify three different hypotheses to address the disadvantages of conventional regression. We found that environmental efficiency in Beijing and Tianjin is higher than the other regions and is becoming divergent. In addition, coal consumption intensity negatively affects environmental efficiency. Large-scale power stations are more environmental efficient than smaller ones. Longer equipment utilization hour can enhance energy performance of power stations, which can decrease carbon emissions and increase environmental efficiency. It is better to promote technology transfer from regions with higher environmental efficiency to regions with lower environmental efficiency. Low-carbon technologies should be promoted to decrease carbon emissions.

Benefits of current and future policies on emissions of China's coal-fired power sector indicated by continuous emission monitoring.

Emission inventories are critical to understanding the sources of air pollutants, but have high uncertainties in China due in part to insufficient on-site measurements. In this study, we developed a method of examining, screening and applying online data from the country's improving continuous emission monitoring systems (CEMS) to reevaluate a "bottom-up" emission inventory of China's coal-fired power sector. The benefits of China's current national emission standards and ultra-low emission policy for the sector were quantified assuming their full implementation. The derived national average emission factors of SO2, NOx and particulate matter (PM) were 1.00, 1.00 and 0.25 kg/t-coal respectively for 2015 based on CEMS data, smaller than those of previous studies that may not fully recognize improved emission controls in recent years. The annual emissions of SO2, NOx and PM from the sector were recalculated at 1321, 1430 and 334 Gg respectively, 75%, 63% and 76% smaller than our estimates based on a previous approach without the benefit of CEMS data. The results imply that online measurement with proper data screening can better track the recent progress of emission controls. The emission intensity (the ratio of emissions to economic output) of Northwest China was larger than that of other regions, attributed mainly to its less intensive economy and industry. Transmission of electricity to more-developed eastern provinces raised the energy consumption and emissions of less-developed regions. Judged by 95 percentiles of flue-gas concentrations measured by CEMS, most power plants met the current national emission standards in 2015 except for those in Northwest and Northeast China, while plants that met the ultra-low emission policy were much scarcer. National SO2, NOx and PM emissions would further decline by 68%, 55% and 81% respectively if the ultra-low emission policy can be strictly implemented, implying the great potential of the policy for emission abatement.

Characteristics of particle emissions and their atmospheric dilution during co-combustion of coal and wood pellets in a large combined heat and power plant.

Coal combustion is one of the most significant anthropogenic CO2 and air pollution sources globally. This paper studies the atmospheric emissions of a power plant fuelled with a mixture of industrial pellets (10.5%) and coal (89.5%). Based on the stack measurements, the solid particle number emission, which was dominated by sub-200 nm particles, was 3.4×1011 MJ-1 for the fuel mixture when electrostatic precipitator (ESP) was cleaning the flue gas. The emission factor was 50 mg MJ-1 for particulate mass and 11 740 ng MJ-1 for the black carbon with the ESP. In the normal operation situation of the power plant, i.e., including the flue-gas desulphurisation and fabric filters (FGD and FF), the particle number emission factor was 1.7×108 MJ-1, particulate mass emission factor 2 mg MJ-1 and black carbon emission factor 14 ng MJ-1. Transmission electron microscopy (TEM) analysis supported the particle number size distribution measurement in terms of particle size and the black carbon concentration. The TEM images of the particles showed variability of the particle sizes, morphologies and chemical compositions. The atmospheric measurements, conducted in the flue-gas plume, showed that the flue-gas dilutes closed to background concentrations in 200 sec. However, an increase in particle number concentration was observed when the flue gas aged. This increase in particle number concentration was interpret as formation of new particles in the atmosphere. In general, the study highlights the importance of detailed particle measurements when utilizing new fuels in existing power plants. Implications: CO2 emissions of energy production decrease when substituting coal with biofuels. The effects of fuels changes on particle emission characteristics have not been studied comprehensively. In this study conducted for a real-scale power plant, co-combustion of wood pellets and coal caused elevated black carbon emissions. However, it was beneficial from the total particle number and particulate mass emission point of view. Flue-gas cleaning can significantly decrease the pollutant concentrations but also changes the characteristics of emitted particles. Atmospheric measurements implicated that the new particle formation in the atmospheric flue-gas plume should be taken into account when evaluating all effects of fuel changes." Are implication statements part of the manuscript?

Distribution of mercury in the combustion products from coal-fired power plants in Guizhou, southwest China.

Method 30B and the Ontario Hydro Method (OHM) were used to sample the mercury in the flue gas discharged from the seven power plants in Guizhou Province, southwest China. In order to investigate the mercury migration and transformation during coal combustion and pollution control process, the contents of mercury in coal samples, bottom ash, fly ash, and gypsum were measured. The mercury in the flue gas released into the atmosphere mainly existed in the form of Hg°. The precipitator shows a superior ability to remove Hgp (particulate mercury) from flue gas. The removal efficiency of Hg2+ by wet flue gas desulfurization (WFGD) was significantly higher than that for the other two forms of mercury. The synergistic removal efficiency of mercury by the air pollution control devices (APCDs) installed in the studied power plants is 66.69-97.56%. The Hg mass balance for the tested seven coal-fired power plants varied from 72.87% to 109.67% during the sampling time. After flue gas flowing through APCDs, most of the mercury in coal was enriched in fly ash and gypsum, with only a small portion released into the atmosphere with the flue gas. The maximum discharge source of Hg for power plants was fly ash and gypsum instead of Hg emitted with flue gas through the chimney into the atmosphere. With the continuous upgrading of APCDs, more and more mercury will be enriched in fly ash and gypsum. Extra attention should be paid to the re-release of mercury from the reutilization of by-products from APCDs. Implications: Method 30B and the Ontario Hydro Method (OHM) were used to test the mercury concentration in the flue gas discharged from seven power plants in Guizhou Province, China. The concentrations of mercury in coal samples, bottom ash, fly ash, and gypsum were also measured. By comparison of the mercury content of different products, we found that the maximum discharge source of Hg for power plants was fly ash and gypsum, instead of Hg emitted with flue gas through the chimney into the atmosphere. With the continuous upgrading of APCDs, more and more mercury will be enriched in fly ash and gypsum. Extra attention should be paid to the re-release of mercury from the reutilization of by-products from APCDs.

The impact of hydroelectric dams on mercury dynamics in South America: A review.

The increase in global demand for electric energy is reflected in plans to construct numerous hydroelectric dams in South America that can cause chronic ecological impacts if not built and managed correctly. One of the main impacts generated by hydropower dams is the accumulation of Hg chemical species in their reservoir compartments and the downstream transport of these contaminants. Hg circulation in these environments has been studied for 27 years and this review brings a synthesis of the dynamics that are now well established, so that future studies can focus on gaps and inconsistent results in the literature. The topics cover the methylation process of Hg, its transfer along the trophic chain and the impacts downstream from dams. In addition, meta-analyses are used to propose regression models that explain Hg dispersion in environmental compartments of reservoirs, using as predictors morphological, spatial and temporal aspects of these environments.

Peak exposures to main components of ash and gaseous diesel exhausts in closed and open ash loading stations at biomass-fuelled power plants.

Fly and bottom ashes are collected at power plants to reduce the environmental effects of energy production. However, handling the ashes causes health problems for operators, maintenance workers and truck drivers at the power plants. Hence, we evaluated ash loaders' peak inhalation exposures to the chemical components of ash and diesel exhausts in open and closed ash loading stations at biomass-fuelled combined heat and power plants. We also carried out chemical and morphological analyses of the ashes to evaluate their health hazard potential in order to find practical technical measures to reduce workers' exposure. On the basis of X-ray diffraction analyses, the main respirable crystalline ash compounds were SiO2, CaSO4, CaO, Ca2Al2SiO7, NaCl and Ca3Al2O6 in the fly ashes and SiO2, KAlSi3O8, NaAlSi3O8 and Ca2Al2SiO7 in the bottom ashes. The short-term exposure levels of respirable crystalline silica, inhalable inorganic dust, Cr, Mn, Ni and nitric oxide exceeded their Finnish eight hours occupational exposure limit values in the closed ash loading station. According to our observations, more attention should be paid to the ash-moistening process, the use of tank trucks instead of open cassette flatbed trucks, and the sealing of the loading line from the silo to the truck which would prevent spreading the ash into the air. The idling time of diesel trucks should also be limited, and ash loading stations should be equipped with exhaust gas ventilators. If working conditions make it impossible to keep to the OEL values, workers must use respirators and protect their eyes and skin.

Collective neurodynamic optimization for economic emission dispatch problem considering valve point effect in microgrid.

The economic emission dispatch (EED) problem aims to control generation cost and reduce the impact of waste gas on the environment. It has multiple constraints and nonconvex objectives. To solve it, the collective neurodynamic optimization (CNO) method, which combines heuristic approach and projection neural network (PNN), is attempted to optimize scheduling of an electrical microgrid with ten thermal generators and minimize the plus of generation and emission cost. As the objective function has non-derivative points considering valve point effect (VPE), differential inclusion approach is employed in the PNN model introduced to deal with them. Under certain conditions, the local optimality and convergence of the dynamic model for the optimization problem is analyzed. The capability of the algorithm is verified in a complicated situation, where transmission loss and prohibited operating zones are considered. In addition, the dynamic variation of load power at demand side is considered and the optimal scheduling of generators within 24 h is described.

Finding Relevant Parameters for the Thin-film Photovoltaic Cells Production Process with the Application of Data Mining Methods.

A data mining approach is proposed as a useful tool for the control parameters analysis of the 3-stage CIGSe photovoltaic cell production process, in order to find variables that are the most relevant for cell electric parameters and efficiency. The analysed data set consists of stage duration times, heater power values as well as temperatures for the element sources and the substrate - there are 14 variables per sample in total. The most relevant variables of the process have been found based on the so-called random forest analysis with the application of the Boruta algorithm. 118 CIGSe samples, prepared at Institut des Matériaux Jean Rouxel, were analysed. The results are close to experimental knowledge on the CIGSe cells production process. They bring new evidence to production parameters of new cells and further research.

Evaluation of arterial hypertension risk under exposure to noise and chemical occupational hazards.

The article covers studies on determining priority risk factors for health of female workers of heat-and-power engineering enterprise, risk groups revealed, suggestions for medical examinations with investigations in early diagnosis of cardiovascular system dysadaptation.

[Offshore substation workers' exposure to harmful factors - Actions minimizing risk of hazards]. / Narazenie pracowników morskich stacji elektroenergetycznych najwyzszych napiec na szkodliwe czynniki - dzialania minimalizujace ryzyko zagrozen.

The current development of electric power industry in Poland, especially in the field of renewable energy sources, including wind power, brings about the need to introduce legislation on new work environment. The development of occupational safety and health (OSH) regulations that must be met by new workplaces, such as offshore substations becomes necessary in view of the construction of modern offshore wind power plants - offshore wind farms. Staying on offshore substation is associated with an increased exposure to harmful health factors: physical, chemical, biological and psychophysical. The main sources of health risks on offshore substations are: temperature, electromagnetic field, noise from operating wind turbines, direct and alternating current, chemicals, Legionella bacteria and social isolation of people. The aim of this article is to draw attention to the problem of offshore substation workers' exposure to harmful factors and to present methods of preventing and reducing the risk-related adverse health effects. In this paper, there are identified and described risks occurring on offshore substations (fire, explosion, lightning, accidents at work). Some examples of the means and the methods for reducing the negative impact of exposure on the human health are presented and discussed. The article also highlights the need to develop appropriate laws and health and safety regulations concerning the new working environment at the offshore substations. The review of researches and international standards shows that some of them can be introduced into the Polish labor market.

Managing Scarce Water Resources in China's Coal Power Industry.

Coal power generation capacity is expanding rapidly in the arid northwest regions in China. Its impact on water resources is attracting growing concerns from policy-makers, researchers, as well as mass media. This paper briefly describes the situation of electricity-water conflict in China and provides a comprehensive review on a variety of water resources management policies in China's coal power industry. These policies range from mandatory regulations to incentive-based instruments, covering water withdrawal standards, technological requirements on water saving, unconventional water resources utilization (such as reclaimed municipal wastewater, seawater, and mine water), water resources fee, and water permit transfer. Implementing these policies jointly is of crucial importance for alleviating the water stress from the expanding coal power industry in China.

Limitations to the Use of Species-Distribution Models for Environmental-Impact Assessments in the Amazon.

Species-distribution models (SDM) are tools with potential to inform environmental-impact studies (EIA). However, they are not always appropriate and may result in improper and expensive mitigation and compensation if their limitations are not understood by decision makers. Here, we examine the use of SDM for frogs that were used in impact assessment using data obtained from the EIA of a hydroelectric project located in the Amazon Basin in Brazil. The results show that lack of knowledge of species distributions limits the appropriate use of SDM in the Amazon region for most target species. Because most of these targets are newly described and their distributions poorly known, data about their distributions are insufficient to be effectively used in SDM. Surveys that are mandatory for the EIA are often conducted only near the area under assessment, and so models must extrapolate well beyond the sampled area to inform decisions made at much larger spatial scales, such as defining areas to be used to offset the negative effects of the projects. Using distributions of better-known species in simulations, we show that geographical-extrapolations based on limited information of species ranges often lead to spurious results. We conclude that the use of SDM as evidence to support project-licensing decisions in the Amazon requires much greater area sampling for impact studies, or, alternatively, integrated and comparative survey strategies, to improve biodiversity sampling. When more detailed distribution information is unavailable, SDM will produce results that generate uncertain and untestable decisions regarding impact assessment. In many cases, SDM is unlikely to be better than the use of expert opinion.

Thermodynamic analysis of in situ gasification-chemical looping combustion (iG-CLC) of Indian coal.

Chemical looping combustion (CLC) is an inherent CO2 capture technology. It is gaining much interest in recent years mainly because of its potential in addressing climate change problems associated with CO2 emissions from power plants. A typical chemical looping combustion unit consists of two reactors-fuel reactor, where oxidation of fuel occurs with the help of oxygen available in the form of metal oxides and, air reactor, where the reduced metal oxides are regenerated by the inflow of air. These oxides are then sent back to the fuel reactor and the cycle continues. The product gas from the fuel reactor contains a concentrated stream of CO2 which can be readily stored in various forms or used for any other applications. This unique feature of inherent CO2 capture makes the technology more promising to combat the global climate changes. Various types of CLC units have been discussed in literature depending on the type of fuel burnt. For solid fuel combustion three main varieties of CLC units exist namely: syngas CLC, in situ gasification-CLC (iG-CLC) and chemical looping with oxygen uncoupling (CLOU). In this paper, theoretical studies on the iG-CLC unit burning Indian coal are presented. Gibbs free energy minimization technique is employed to determine the composition of flue gas and oxygen carrier of an iG-CLC unit using Fe2O3, CuO, and mixed carrier-Fe2O3 and CuO as oxygen carriers. The effect of temperature, suitability of oxygen carriers, and oxygen carrier circulation rate on the performance of a CLC unit for Indian coal are studied and presented. These results are analyzed in order to foresee the operating conditions at which economic and smooth operation of the unit is expected.

Linear free energy correlations for fission product release from the Fukushima-Daiichi nuclear accident.

This paper extends the preliminary linear free energy correlations for radionuclide release performed by Schwantes et al., following the Fukushima-Daiichi Nuclear Power Plant accident. Through evaluations of the molar fractionations of radionuclides deposited in the soil relative to modeled radionuclide inventories, we confirm the initial source of the radionuclides to the environment to be from active reactors rather than the spent fuel pool. Linear correlations of the form In χ = −α ((ΔGrxn°(TC))/(RTC)) + ß were obtained between the deposited concentrations, and the reduction potentials of the fission product oxide species using multiple reduction schemes to calculate ΔG°rxn (TC). These models allowed an estimate of the upper bound for the reactor temperatures of TC between 2015 and 2060 K, providing insight into the limiting factors to vaporization and release of fission products during the reactor accident. Estimates of the release of medium-lived fission products 90Sr, 121mSn, 147Pm, 144Ce, 152Eu, 154Eu, 155Eu, and 151Sm through atmospheric venting during the first month following the accident were obtained, indicating that large quantities of 90Sr and radioactive lanthanides were likely to remain in the damaged reactor cores.