Nitrogen-rich biomass can be suitable for utilization as a substrate in anaerobic co-digestion (AC-D) instead of animal manure. This biomass combined with other substrates could replace animal waste in certain cases in which animal waste cannot be used to obtain methane gas. Methane is the majority component of the biogas produced in AC-D used as an energy source. In this research, a comparative study has been developed between leguminous plant biomass and pig manure in AC-D in a semicontinuous regime at different Organic Load Rate (OLR) values (1.2−1.8 g VS LD−1 d−1). The most elevated methane yield (494 NL CH4 kg VS−1) belongs to assays developed with nitrogen-rich biomass at 1.4 g VS LD−1 d−1. Methane-yield results of nitrogen-rich biomass are higher than pig manure results for all OLR studied values. The digestate obtained in the AC-D is a fertilizer of interest due to its nitrogen content and ability to save energy by replacing mineral fertilizers.

In many competitive electricity markets around the world, the dynamic behavior of hourly electricity prices is subject to significant uncertainty and volatility due to electricity demand, availability of generation sources, fuel costs, and power plant availability. This work is devoted to describing and comparing the dynamics of electricity prices for some markets in Europe, selecting the five countries representing the largest economies in Western Europe (France, Germany, Italy, Spain, and the United Kingdom). Additionally, Denmark is included in the study to assess whether the size of the country is a determinant of price behavior. The six datasets of hourly price series, which exhibits a strong daily seasonality, are modelled using the most relevant well-known statistical models for time series analysis: ARIMA models and different versions of GARCH models. The comparison of the estimated models’ parameters, the analysis of outliers’ rate of appearance and the evaluation of out-of-sa... [more]

A methodology is outlined for equipment selection for the extraction of secondary deposits, supported by the Multiple Criteria Decision Making (MCDM) tool based on the Analytic Hierarchy Process (AHP) method and applied to evaluate its impact on the mining system’s performance and the viability of the rock mining project. The equipment selection analysis affords us the means to explore selected options, taking technological and economic parameters into account, and opening the way for making the decision to begin or discontinue mining operations. The simulation results show how maintaining the mining site in a good condition impacts on the actual duty cycle of mining equipment, the time required to complete the hauling task and the operating costs.

Combined heat and power (CHP) plants are known as efficient technologies to reduce environmental emissions, balance energy costs, and increase total energy efficiency. To obtain a more efficient system, various optimization methods have been employed, based on numerical, experimental, parametric, and algorithmic optimization routes. Due to the significance of algorithmic optimization, as a systematic method for optimizing energy systems, this novel review paper is focused on the meta-heuristic optimization algorithms, implemented in CHP energy systems. By considering the applied objective functions, the main sections are divided into single-objective and multi-objective algorithms. In each case, the units’ combination is briefly detailed, the objective functions are introduced, and analyses are conducted. The main aim of this paper is to gather a database for the optimization of CHPs, demonstrate the effect of the applied optimization methods on the objective functions, and finally, in... [more]

Cultivating microalgae requires a nitrogen and phosphorous feed source. Anaerobic digestion waste (digestate) provides a cheap sustainable feedstock for these materials. Previous studies have successfully demonstrated the feasibility of nutrient recovery and subsequent algae growth. There is now a need to fully characterise digestate filtration to improve our understanding of this process prior to its commercialisation. In this work, digestate filtration is characterised at bench scale using frontal (dead-end) filtration and a 100 kDa MWCO ultrafiltration membrane. Our experiments demonstrated rapid cake formation causing significant flux decline. The steady-state permeate flux for digestate was 2.4 to 4.8 L m−2 h−1, a reduction of ~90% compared to clean water flux. The specific cake resistance was ~1015 m kg−1 and the compressibility index 1.07. A series of four filtration and cleaning cycles showed 90% flux recovery following a clean water wash. Digestate filtration was then evaluate... [more]

The effects of hydrogen-enriched biogas on combustion and emissions of a dual-fuel spark-ignition engine with different hydrogen concentration ratios were studied numerically. A 1-cylinder spark ignition was used to perform a numerical simulation. To reveal the influence of the compression ratios on combustion and emissions of a gaseous engine, the crankshaft of the engine was modified to generate different compression ratios of 8.5, 9.0, 9.4, 10.0, and 10.4. The biogas contained 60 and 40% methane (CH4) and carbon dioxide (CO2), respectively, while the hydrogen fractions used to enrich biogas were 10, 20, and 30% of the mixture by volume. The ignition timing is fixed at 350 CA°. The results indicate that the in-cylinder pressure, combustion temperature, and combustion burning speed increase gradually with increasing hydrogen concentration due to the combustion characteristics of hydrogen in blends. As increasing the compression ratio, NOx emissions increase proportionally, while CO2 e... [more]

Based on the synergistic effect of ripening and hydrogen ion etching in a hydrothermal solution, a simple, facile, and low-cost new strategy was demonstrated to prepare multi-channel surface-modified amorphous Fe2O3 nanospheres as anodes for Li-ion batteries in this study. Compared with polycrystalline Fe2O3, the conversion reaction between amorphous Fe2O3 and lithium ions has a lower Gibbs free energy change and a stronger reversibility, which can contribute to an elevation in the cycle capability of the electrode. Meanwhile, there are abundant active sites and more effective dangling bonds/defects in amorphous materials, which is beneficial to promote charge transfer and lithium-ion migration kinetics. The Galvanostatic intermittent titration analysis results confirmed that the amorphous Fe2O3 electrode had a higher Li+ diffusion coefficient. In addition, the surfaces of the amorphous nanospheres are corroded to produce multiple criss-cross channels. The multi-channel surface structu... [more]

Photovoltaic (PV) systems are dependent on solar irradiation and environmental temperature to achieve their best performance. One of the challenges in the photovoltaic industry is performing maintenance as soon as a system is not working at its full generation capacity. The lack of a proper maintenance schedule affects power generation performance and can also decrease the lifetime of photovoltaic modules. Regarding the impact of environmental variables on the performance of PV systems, research has shown that soiling is the third most common reason for power loss in photovoltaic power plants, after solar irradiance and environmental temperature. This paper proposes a new statistical predictor for forecasting PV power generation by measuring environmental variables and the estimated mass particles (soiling) on the PV system. Our proposal was based on the fit of a nonlinear mixed-effects model, according to a log-logistic function. Two advantages of this approach are that it assumes a n... [more]

The large-scale storage of hydrogen in salt caverns, modelled on today’s natural gas storage, is a promising approach to storing renewable energy over a large power range and for the required time period. An essential subsystem of the overall gas storage is the surface facility and, in particular, the compressor system. The future design of compressor systems for hydrogen storage strongly depends on the respective boundary conditions. Therefore, this work analyses the requirements of compressor systems for cavern storage facilities for the storage of green hydrogen, i.e., hydrogen produced from renewable energy sources, using the example of Lower Saxony in Germany. In this course, a hydrogen storage demand profile of one year is developed in hourly resolution from feed-in time series of renewable energy sources. The injection profile relevant for compressor operation is compared with current natural gas injection operation modes.

The Cretaceous condensate gas reservoir in Yakela is in a fan delta system in which the river channel swings frequently and the contact relationships between sandbodies are complicated both vertically and horizontally. Therefore, making the sandbody architecture clear is becoming the most urgent demand in locating the remaining oil. However, conventional well correlations and fine interpretation do not apply in this area due to the large-spacing of wells and the lack of reliable seismic data. In this paper, we analyzed the vertical characteristics of sandbody architecture including the type and thickness of architectural elements and their contact relationships based on well data, then simulated the lateral and planar distribution probabilities via a database containing a large number of dimension parameters from relevant architectural elements using Monte Carlo simulation. This simulation provides reasonable and efficient estimation of inter-well sandbody distribution. The workflow an... [more]

In the era of aiming toward reaching a sustainable ecosystem, the primary focus is to curb the emissions generated by non-conventional resources. One way to achieve this goal is to find an alternative to traditional power plants (TPP) by integrating various distributed energy resources (DERs) via a Virtual Power Plant (VPP) in modern power systems. Apart from reducing emissions, a VPP enhances the monetary benefits to all its participants, including the DER owners, participants, and utility personnel. In this paper, the multi-objective optimal scheduling of the VPP problem considering multiple renewable energy resources has been solved using the multi-objective black widow optimization (MOBWO) algorithm. Renewable resources consist of solar PV modules, wind turbines, fuel cells, electric loads, heat-only units, and CHP units. The weighting factor method was adopted to handle the multi-objective optimal scheduling (MOOS) problem by simultaneously maximizing profit and minimizing emissio... [more]

The paper focuses on water losses in the turbine condenser cooling system of the 905 MW power unit in Opole Power Plant (Opole Poland). The evaporative and drift losses are determined for various operating and atmospheric conditions. The drift loss is found to be 0.125−0.375% of the cooling water flux and some increase in this loss is noticed with increase in unit power and ambient temperature. The studies have shown that the presence of wind increases the total water loss related to the power generated by the power unit. This effect is analysed for selected constant air temperature values Tamb. The increase of the cooling water loss stream, related to the power of the unit, is at the level of 14.8% for Tamb equal to 7 °C, 23% for 15 °C, and approximately 10% at 22 °C. These increases are related to the level of losses in almost no wind conditions. It is investigated how the change in the cooling water flux affects the power unit operation and the amount of water loss. For the power un... [more]

Curtailment losses for large-scale hybrid wind−solar photovoltaic (PV) plants with a single grid connection point are often calculated in 1 h time resolution, underestimating the actual curtailment losses due to the flattening of power peaks occurring in shorter time frames. This paper analyses the curtailment losses in hybrid wind−PV plants by utilising different time resolutions of wind and PV production while varying the grid cut-off power, wind/solar PV farm sizes, and shares of wind/PV capacity. Highly resolved 1 s measurements from the operational wind farm and pyranometer are used as an input to specialized wind and PV farm power production models that consider the smoothing effect. The results show that 15 min resolution is preferred over 1 h resolution for large-scale hybrid wind−PV plants if more accurate assessment of curtailment losses is required. Although 1 min resolution additionally increases the estimation accuracy over 15 min resolution, the improvement is not signifi... [more]

This paper introduces the concept, theory of operation and applications of soft open points for direct current networks (DCSOPs). The DCSOP is based on a bidirectional DC−DC converter actively controlled to behave like a normal conductor. Unlike the normal conductor, the DCSOP can transfer the electric power between nodes at different voltage levels. With this advantage, the DCSOP can effectively control the power flow direction. Thus, DCSOPs can play a vital role in the reconfiguration of DC distribution networks. The operation and control of the DCSOP device was investigated, both in transient and steady-state conditions. Then, a DCSOP was integrated into a DC microgrid model to validate its ability to change the power flow through the modelled feeders. In addition, a set of reliability indicators was calculated for the DC microgrid under different reconfiguration scenarios. It was shown that reliability is improved when the DCSOP device implements network reconfiguration. Finally, a... [more]

The emergence of large photovoltaic farms poses a new challenge for quick and economic diagnostics of such installations. This article presents this issue starting from a quantitative analysis of the impact of panel defects, faulty installation, and lack of farm maintenance on electricity production. We propose a low-cost and efficient method for photovoltaic (PV) plant quality surveillance that combines technologies such as an unmanned aerial vehicle (UAV), thermal imaging, and machine learning so that systematic inspection of a PV farm can be performed frequently. Most emphasis is placed on using deep neural networks to analyze thermographic images. We show how the use of the YOLO network makes it possible to develop a tool that performs the analysis of the image material already during the flyby.

The interaction between global horizontal irradiance (GHI) and temperature helps determine the maximum amount of solar power generated. As temperature increases, GHI increases up to the point that it increases at a decreasing rate and then decreases. Therefore, system operators need to know the maximum possible solar power which can be generated. Using the multivariate adaptive regression splines, extreme value theory and copula models, the present paper seeks to determine the maximum temperature that will result in the generation of the maximum GHI ceteris paribus. The paper also discusses extremal dependence modelling of GHI with temperature and relative humidity (RH) at one radiometric station using South African data from 16 November 2015 to 16 November 2021. Empirical results show that the marginal increases of GHI converge to 0.12 W/m2 when temperature converges to 44.26 °C and the marginal increases of GHI converge to −0.1 W/m2 when RH converges to 103.26%. Conditioning on GHI,... [more]

The current geometric increase in the global deployment of solar photovoltaic (PV) modules, both at utility-scale and residential roof-top systems, is majorly attributed to its affordability, scalability, long-term warranty and, most importantly, the continuous reduction in the levelized cost of electricity (LCOE) of solar PV in numerous countries. In addition, PV deployment is expected to continue this growth trend as energy portfolio globally shifts towards cleaner energy technologies. However, irrespective of the PV module type/material and component technology, the modules are exposed to a wide range of environmental conditions during outdoor deployment. Oftentimes, these environmental conditions are extreme for the modules and subject them to harsh chemical, photo-chemical and thermo-mechanical stress. Asides from manufacturing defects, these conditions contribute immensely to PV module’s aging rate, defects and degradation. Therefore, in recent times, there has been various inves... [more]

Presently, the world is undergoing exciting haste to install photovoltaic (PV) systems in industry, residential/commercial buildings, transportation, deserts, street lights, and many other applications. Solar photovoltaic energy systems are clean and reliable energy sources that are unlimited, unlike their fossil fuel counterparts. The energy market is rapidly growing globally with newly and cumulative installed capacities of about 37.6 GW and 139.6 GW, accounting for 53% and 55%, respectively, in 2017, making it one of the fastest-growing industries. The cumulative photovoltaic installations are projected to have reached 600 GW worldwide and are projected to reach 4500 GW by 2050 because of the strategies and policies of many countries. In 2021, more than three-quarters of the developed countries are now home to one solar installation. This article evaluates a critical and extensive review of the contributions of solar photovoltaic systems to national development. The approach follows... [more]

Despite the significant slowdown of economic activity in South Africa by virtue of the COVID-19 outbreak, load shedding or scheduled power outages remained at a high level. The trend of rising load-shedding hours has persisted throughout most of the year 2022. Operational issues within the South African power utility inflamed the unpredictable nature of generation capacity, resulting in unscheduled outages at several generating units, mostly due to multiple breakdowns. To forestall substantial spikes in energy costs, an increasing number of enterprises and homeowners have started to gradually adopt renewable energy technologies to sustain their operational demand. Therefore, there is an increase in the exploration and investment of battery energy storage systems (BESS) to exploit South Africa’s high solar photovoltaic (PV) energy and help alleviate production losses related to load-shedding-induced downtime. As a result, the current work presents a comprehensive and consequential revie... [more]

The electrical system is undergoing a structural change, dissolving into a new concept of a distributed environment, based on renewable energies, demand management and resource sharing [...]

In this study, in terms of the mechanisms of nitric oxide (NO) emissions, research was carried out to consider the impact of physical and chemical properties of wood and herbaceous biomass processed into pellets and briquettes in the course of the combustion process (in individual phases) in a low-power heating device. Combustion tests in the grate heating device showed statistically significant differences in the combustion process and thus carbon monoxide (CO), nitric oxide (NO), and sulfur dioxide (SO2) emissions in the fuel form and the combustion phase. In terms of assessing the ecological and energy parameters of the combustion process, the nitrogen content in biomass was not the most important factor indicating the formation of NO emissions. Usually, the strongest correlations were observed with the formation of NO emissions in the first phase of combustion, which was related to the emissions of CO and SO2. In the second and third flame phases, a significant reduction in NO emis... [more]

The transient electromagnetic disturbance generated by arcing discharge between the pantograph and catenary can pose a significant risk to the safe operation of electrified railways. In order to better comprehend its properties, a pantograph−catenary discharge generating device is designed to simulate the discharge phenomenon with moving electrodes in this experimental investigation. The effects of the applied voltage, the gap distance, and the relative motion between the pantograph and catenary on the time- and frequency-domain features of the discharge current and electromagnetic field are investigated. The variation trends of pulse peak current, rise time, pulse repetition frequency, maximum amplitude, and characteristic frequency in the radiation spectrum are retrieved under varying experimental settings, and the effect mechanisms are derived from the physics of gas discharge. A dynamic discharge test is conducted in this study in order to further understand the effect of electrode... [more]

Michael Potter pioneered microbial fuel cell (MFC) technology in 1911 [...]

In order to ensure the safe and reliable operation of a high-speed railway, the precise positioning of the mid-point anchor in the catenary is very important. In view of the two problems in the calculation of the mid-point anchor position of the catenary in a long ramp section, the calculation accuracy is low, and the calculation of the central anchor clamp position is lacking. In this study, the predetermined location of the mid-point anchor is chosen based on the mid-point anchor location principle and the line condition, and the range of the allowable error of the mid-point anchor setting is determined according to the predetermined position of the mid-point anchor. Secondly, by considering the impact of the line ramp and using the measured span length, the tension difference of the clue in the direction of the line is calculated. Then, the theoretical location of the mid-point anchor clamp is determined using the downhill component and the tension difference. Finally, the theoretic... [more]

The architectural and construction professions are in a state of major transition [...]