Crack extraction of solar panels has become a research focus in recent years. The cracks are small and hidden. In addition, there are particles of irregular shape and size on the surface of the polycrystalline solar panel, whose reflection position and direction are random. Therefore, there is a complex and uneven texture background on the solar panel image, which makes the crack extraction more difficult. In this paper, a crack extraction method combining image texture and morphological features is proposed. Firstly, the background texture and multi-scale details are suppressed by the linear filter and the Laplace pyramid decomposition method. Secondly, the edge can be extracted based on the modulus maximum method of the wavelet transform. Finally, cracks were extracted by using the improved Fuzzy C-means (FCM) clustering combining the morphological and texture features of the cracks. To make the extraction results more accurate and reasonable, an improved region growth algorithm is p... [more]

Sludge dewatering is a key element in sludge’s processing and management. Solid-phase separation, sludge volume reduction and the separation of a high-quality supernatant are the main tasks of the dewatering devices. The effectiveness of this task, in turn, results from the selection of the dewatering method and conditioning of the sludge before dewatering. The aim of the research was to determine the influence of conditioning substances (polyelectrolyte, fly ash and zeolite) on the efficiency of dewatering at variable filtration pressure. The use of polyelectrolyte in sludge conditioning was a solution that increased the efficiency of the filtration process. On the contrary, the use of structure-forming substances (fly ash and zeolite) slows the process but reduces the hydration of the filter cake. The same trends were obtained in dual conditioning combining dosing of polyelectrolyte and ash or zeolite. It was also shown that the dewatering efficiency of conditioned sludge with these... [more]

In this study, optimal decision-making process in photovoltaic (PV) system location selection in Saudi Arabia is described. First, to identify the criteria that influence the decision of selecting a suitable location for the PV system, the geographical information system (GIS)-based multi-criteria decision making (MCDM) approach is used. Next, to assess the weights of the criteria that present different aspects of the investigated locations, four major criteria and 11 sub-criteria are proposed, and analytic hierarchy process (AHP) is applied to develop comparison decision matrix. Finally, the order preference by similarity to ideal solution (TOPSIS) technique evaluates and classifies 17 cities (such as Riyadh, Jeddah) in Saudi Arabia. The result shows that Tabuk city in the northern of Saudi Arabia is the best location. Among the 17 cities, the performance score of seven cities is above or equal 80%, and Tabuk city has the highest score with 87%. This analytical approach could contribu... [more]

The degradation mode is of great significance for reducing the complexity of research on the aging mechanisms of lithium-ion batteries. Previous studies have grouped the aging mechanisms into three degradation modes: conductivity loss (CL), loss of lithium inventory (LLI) and loss of active material (LAM). Combined with electrochemical impedance spectroscopy (EIS), degradation modes can be identified and quantified non-destructively. This paper aims to extend the application of this method to more operating conditions and explore the impact of external factors on the quantitative results. Here, we design a quantification method using two equivalent circuit models to cope with the different trends of impedance spectra during the aging process. Under four conditions, the changing trends of the quantitative values of the three degradation modes are explored and the effects of the state of charge (SoC) and excitation current during EIS measurement are statistically analyzed. It is verified... [more]

Many battery state of charge (SOC) estimation methods have been studied for decades; however, it is still difficult to precisely estimate SOC because it is nonlinear and affected by many factors, including the battery state and charge−discharge conditions. The extended Kalman filter (EKF) is generally used for SOC estimation, however its accuracy can decrease owing to the uncertain and inaccurate parameters of battery models and various factors with different time scales affecting the SOC. Herein, a SOC estimation method based on the EKF is proposed to obtain robust accuracy, in which the errors are compensated by a long short-term memory (LSTM) network. The proposed approach trains the errors of the EKF results, and the accurate SOC is estimated by applying calibration values corresponding to the condition of the battery and its load profiles with the help of LSTM. Furthermore, a multi-LSTM structure is implemented, and it adopts the ensemble average to guarantee estimation accuracy.... [more]

The horizontal rotor wave energy converter is a newly designed wave energy converter. While the mooring system plays a vital role in keeping the device floating stably, the selection of the mooring angle has immediate effects on the device’s floating stability and energy generation efficiency. Given the properties of wave energy along the coast in Shandong Province, this study combines wave statistics gathered from field measurements of a certain area in the Bohai Sea with hydrological data obtained in a field test in the same sea area and adopts Stokes’ fifth-order wave theory to theoretically design and simulate the mooring system for the new type of power generating device. With the help of AQWA software, data on the dynamics of the device at various angles are obtained to construct models and carry out regular wave experiments according to the most appropriate mooring angles to show the validity of the selected mooring angles. The consistency of the results between the experiment a... [more]

A thermodynamical analysis of steam reforming of Associated Petroleum Gas (APG) was conducted in the presented research. The reforming process of heavy hydrocarbons for small scale power generation is a complex issue. One of the main issues is that a set of undesired chemical reactions deposit solid carbon and, consequently, block the reactor’s catalytic property. The experimental investigation is crucial to design an APG reforming reactor. However, a numerical simulation is a key tool to design a safe operating condition. Designing the next generation of reactors requires a complex coupling of mathematical models, kinetics, and thermodynamic analysis. In practice, the thermodynamic analysis should be applied in each control volume to assure realistic results. This is not easy to apply in practice since both thermodynamic analysis and CFD modeling can be time-consuming. In this paper, the authors suggest using a mathematical formalism called Parametric Equation Formalism to calculate t... [more]

Arsenic emission from coal combustion power plants has attracted increasing attention due to its high toxicity. In this study, it was found that there was a close relationship between the ash fusion temperature (AFT) and arsenic distribution based on the thermodynamic equilibrium calculation. In addition to the AFT, coal characteristics and combustion temperature also considerably affected the distribution and morphology of arsenic during coal combustion. Thus, an arsenic volatilization model based on the AFT, coal type, and combustion temperature during coal combustion was developed. To test the accuracy of the model, blending coal combustion experiments were carried out. The experimental results and published data proved that the developed arsenic volatilization model can accurately predict arsenic emission during co-combustion, and the errors of the predicted value for bituminous and lignite were 2.3−9.8%, with the exception of JingLong (JL) coal when combusted at 1500 °C.

In this contemporary era, environmental problems spread at different levels in all countries of the world. Economic growth does not just depend on prioritizing the environment or improving the environmental situation. If the foreign direct investment is directed to the polluting industries, they will increase pollution and damage the environment. The purpose of the study is to consider the relationship between foreign direct investment in Kazakhstan and Uzbekistan and economic growth and renewable energy consumption. The study is based on data obtained from 1992 to 2018. The results show that there is a two-way link between foreign direct investment and renewable energy consumption in the considered two countries. The Granger causality test approach is applied to explore the causal relationship between the variables. The Johansen co-integration test approach is also employed to test for a relationship. The empirical results verify the existence of co-integration between the series. The... [more]

In recent years, investigations on advanced technological solutions aiming to achieve high-energy performance in buildings have been carried out by research centers and universities, in accordance with the reduction in buildings’ energy consumption required by European Union. However, even if the research and design of new technological solutions makes it possible to achieve the regulatory objectives, a building’s performance during operation deviates from simulations. To deepen this topic, interesting studies have focused on testing these solutions on full-scale facilities used for real-life activities. In this context, a test facility will be built in the university campus of Politecnico di Torino (Italy). The facility has been designed to be an all-electric nearly Zero Energy Building (nZEB), where heating and cooling demand will be fulfilled by an air-source heat pump and photovoltaic generators will meet the energy demand. In this paper, the facility energy performance is evaluate... [more]

The advancement of electric mobility as a measure to comply with international climate targets and sustain renewable resources in the future has led to an electrification of the mobility sector in recent years. This trend has not been spared in the logistics and commercial vehicle sector. Emerging electric powertrain concepts for long-haul vehicles have since been developed and adapted to different use cases and axle concepts. In this paper, the authors show the influence of the powertrain topology and the associated design of the electric machine on the efficiency and energy consumption of commercial vehicles. For this, existing series or prototype long-haul axle topologies are analyzed regarding their efficiency and operating points within four driving cycles. Additionally, a sensitivity analysis on the influence of the total gearbox ratio tests the assumed designs. We find that single-machine topologies offer efficiency advantages over multiple-machine topologies. However, this stud... [more]

With renewable power sources and new topology structures being widely introduced into the power system, the current local information-based power generation-side protection cannot fully guarantee the protection performance and the safety coordination with the power grid. This paper proposes an improved hierarchical protection system on the power generation-side. The proposed system takes advantage of the fusion of multi-information provided by the system, station and local layers. The system layer provides the information such as system voltage control and power regulation demand, so that the generation-side protection and control system can adapt to the system operation mode and power regulation demand. The station layer realizes the coordination of the protection principle and action strategy among the related units through information interaction with the power grid, the automatic control system and the local layer protection. The local layer introduces the condition monitoring info... [more]

This paper presents an electromagnetic transient analysis of lightning-initiated overvoltage stresses of the step-up transformers installed inside a nacelle of onshore, multi-megawatt, new-generation wind turbines. The increase in the wind turbine (WT) nominal power output, necessitated introducing the step-up transformer into the nacelle. A transformer installed inside a nacelle is subjected to completely different overvoltage stresses from those present if it were installed at the base of the WT tower. This has serious repercussions on its overvoltage protection (i.e., selection and installation of surge arresters) and insulation coordination. Furthermore, the overvoltage protection of medium-voltage cables (inside the tower) is also problematic when considering their length, proximity to the tower wall, and their screen grounding practices, and needs to be tackled in conjunction with that of the step-up transformer. This paper presents detailed models for the various components of t... [more]

The strategies, plans and legislation on energy market development and decarbonization in the European Union (EU) developed in recent years, such as the directives implementing the package “Clean energy for all Europeans”, aim at promoting not only renewable energy sources, but also new institutions that involve the development of local energy markets and a greater role for citizens in managing their own energy generation. At the same time, Poland remains the economy most dependent on coal and one of the largest air polluters in the EU. In order to minimize this problem and to meet the direction of energy development in the EU, Poland decided to establish, among other things, an energy cooperative. It is intended to fill the gap in the development of the civil dimension of energy on a local scale and at the same time improve efficiency in the use of the potential of renewable energy sources in rural areas. The authors of the paper seek to verify the extent to which this new institution... [more]

This study aims to examine the asymmetric nexus between CO2 emissions and renewable energy and economic and population growth in seven East African countries (EACs) at the regional level and country levels. Common correlated effect means group (CCEMG), nonlinear autoregressive distributed lagged (NARDL), and causality tests were employed for the panel data from 1980 to 2016. The main findings are as follows: (1) Renewable energy consumption negatively affects CO2 emissions, while economic and population growth positively affect CO2 emissions at the regional level. (2) The findings of asymmetric and symmetric linkages between CO2 emissions and its determinants (economic and population growth and renewable energy) are very volatile across the country levels. (3) The causality hypotheses are different across the country and regional levels. (4) This study shows the renewable energy growth nexus, wherein renewable energy positively affects economic growth at the regional level. Lastly, the... [more]

The chemical looping gasification of residual biomasses—operated in fluidized beds composed of oxygen-carriers—may allow the production of biofuels from syngas. This biomass-to-fuel chain can contribute to mitigate climate change, avoiding the accumulation of greenhouse gases in our atmosphere. The ongoing European research project Horizon2020 CLARA (G.A. 817841) investigates wheat-straw-pellets (WSP) and raw-pine-forest-residue (RPR) pellets as feedstocks for chemical looping gasification. This work presents experimental results from devolatilizations of WSP and RPR, in bubbling beds made of three different oxygen-carriers or sand (inert reference), at 700, 800, 900 °C. Devolatilization is a key step of gasification, influencing syngas quality and quantity. Tests were performed at laboratory-scale, by a quartz reactor (fluidizing agent: N2). For each pellet, collected data allowed the quantification of released gases (H2, CO, CO2, CH4, hydrocarbons) and mass balances, to obtain gas yi... [more]

This study aimed to determine the flow structures and heat transfer for flow past a tandem cylinder array and the effect of a slit on the enhancement of heat transfer. Different distances between cylinders and inclination angles of the slit were simulated to determine the effects on the flow pattern and heat transfer. Overall, the Nusselt number of the array is increased by 6−15% with applying a slit on a cylinder. However, in some special conditions, the slit induces two kinds of flow pattern transforms which are Suppression and Revival. The suppression mode inhibits the vortex shedding and reduces the heat transfer. In contrast, the revival mode triggers the vortex shedding and increases heat transfer.

In this work, the main research question is how a high penetration of energy communities (ECs) affects the national electricity demand in the residential sector. Thus, the existing building stock of three European regions/countries, namely, the Iberian Peninsula, Norway, and Austria, is analyzed and represented by four different model energy communities based on characteristic settlement patterns. A tailor-made, open-source model optimizes the utilization of the local energy technology portfolio, especially small-scale batteries and photovoltaic systems within the ECs. Finally, the results on the national level are achieved by upscaling from the neighborhood level. The findings of different 2030 scenarios (building upon narrative storylines), which consider various socio-economic and techno-economic determinants of possible future energy system development, identify a variety of modification potentials of the electricity demand as a result of EC penetration. The insights achieved in th... [more]

With the increasing penetration of renewable resources into the low-voltage distribution grid, the demand for alternatives to grid reinforcement measures has risen. One possible solution is the use of battery systems to balance the power flow at crucial locations in the grid. Hereby, the optimal location and size of the system have to be determined in regard to investment and its effect on grid stability. In this paper, the optimal placement and sizing of battery storage systems for grid stabilization in a small low-voltage distribution grid in southern Germany with high PV penetration are investigated and compared to a grid heuristic reinforcement strategy.

This article introduces a new non-pillar coal mining technology (i.e., Gob-side Entry Retaining by Roof Cutting (GERRC)) under the condition of thick and hard roofs. First, we theoretically analyzed the solution to the large suspension span of the thick and hard roof in coal mining. Three-Zone pre-split blasting design in non-pillar coal mining for thick and hard roofs was proposed, based on the principles of rock mechanics. After field experiments, the technology was successfully applied to the non-pillar coal mining of a huge thick conglomerate roof. This research supplements the non-pillar mining technology system. The proposed technologies and methods have strong applicability and have certain guiding significance for the safe and efficient mining of related coal mines.

The new standards on energy saving for new and existing buildings have animated both researchers and technicians in recent years, aiming at reducing the dependence on fossil fuels, improving indoor comfort, and systems efficiency. In this scenario, special attention must be paid to historical buildings that need to preserve their key testimonial heritage within the society. This paper describes the design and realization stages of a pilot system based on a ground-coupled heat pump, operating both in heating and cooling modes, installed in the monumental site of Saints Marcellino and Festo (SM&F), in Naples, Southern Italy. This study aims to demonstrate that low-enthalpy geothermal systems can be employed as energy retrofit applications in buildings of historical, artistic, and cultural interest and, at the same time, to prove that the use of this technology allows achieving the objectives, set at global level by the current regulations, and requiring a reduction of carbon dioxide emis... [more]

Interior and exterior wind turbine blade inspections are necessary to extend the lifetime of wind turbine generators. The use of unmanned vehicles is an alternative to exterior wind turbine blade inspections performed by technicians that require the use of cranes and ropes. Interior wind turbine blade inspections are even more challenging due to the confined spaces, lack of illumination, and the presence of potentially harmful internal structural components. Additionally, the cost of manned interior wind turbine blade inspections is a major limiting factor. This paper analyses all aspects of the viability of using manually controlled or autonomous aerial vehicles for interior wind turbine blade inspections. We discuss why the size, weight, and flight time of a vehicle, in addition to the structure of the wind turbine blade, are the main limiting factors in performing internal blade inspections. We also describe the design issues that must be considered to provide autonomy to unmanned v... [more]

The article deals with the study on the efficiency of units for porous ammonium nitrate production. The ways which increase the effective implementation of energy resources are determined by including the ejector recycling module, heat and mass exchangers that utilize principles of regenerative indirect evaporative cooling, and the sub-atmospheric inverse Brayton cycle. Mixed exergy analysis evaluates all flows of the system contour as those of the same value. The target parameter for determining the efficiency of both systems is the ratio of the unit’s productivity to the exergy expenditures to produce the unit mass of the product. As a result, it is found that the mentioned devices and units enable to increase the efficiency of the basic scheme by 87%.

Container shipping is the largest producer of emissions within the maritime shipping industry. Hence, measures have been designed and implemented to reduce ship emission levels. IMO’s MARPOL Annex VI, with its future plan of applying Tier III requirements, the Energy Efficiency Design Index for new ships, and the Ship Energy Efficiency Management Plan for all ships. To assist policy formulation and follow-up, this study applies an energy consumption approach to estimate container ship emissions. The volumes of sulphur oxide (SOx), nitrous oxide (NOx), particulate matter (PM), and carbon dioxide (CO2) emitted from container ships are estimated using 2018 datasets on container shipping and average vessel speed records generated via AIS. Furthermore, the estimated reductions in SOx, NOx, PM, and CO2 are mapped for 2020. The empirical analysis demonstrates that the energy consumption approach is a valuable method to estimate ongoing emission reductions on a continuous basis and to fill dat... [more]

Liquid air can be employed as a carrier of cold energy obtained from liquefied natural gas (LNG) and surplus electricity. This study evaluates the potential of liquid air as a distributed source with a supply chain for a cold storage system using liquid air. Energy storing and distributing processes are conceptually designed and evaluated considering both the thermodynamic and economic aspects. Further, the proposed supply chain is compared with a conventional NH3/CO2 cascade refrigeration system. The thermodynamic analysis demonstrates that the exergy efficiency and the coefficient of performance of the proposed supply chain are 22% and 0.56, respectively. Economic analysis is based on a life cycle cost (LCC) evaluation. From the economic analysis, the liquid air production cost and the LCC of a liquid air cold storage system (LACS) are estimated to be 40.4 USD/ton and 34.2 MMUSD, respectively. The LCC is reduced by 19% in the LACS compared with the conventional refrigeration system.... [more]