This paper assesses the profitability of battery storage systems (BSS) by focusing on the internal rate of return (IRR) as a profitability measure which offers advantages over other frequently used measures, most notably the net present value (NPV). Furthermore, this study proposes a multi-objective optimisation (MOO) approach to IRR estimation instead of relying on the simple linear optimisation and compares the results to the popular linear optimisation with battery cycle-cost penalty. The analysis is conducted under perfect foresight conditions by considering multiple revenue streams: arbitrage trading in the day-ahead and intraday markets, peak shaving, participating in the primary reserves market, and from photovoltaic (PV) power-generation unit. Data are collected for the German power market for 2017 and 2021. The results show that MOO approach yields similar IRR estimates to the cycle-cost model in 2017. However, higher market volatility and increased electricity prices in 2021... [more]

Energy generation using dielectric elastomers (DE) has received a great deal of attention due to their light weight, low cost, and high efficiency. This method is an environmentally friendly system that generates electricity without emitting carbon dioxide and without using rare earths, and can contribute to the reduction of global warming. However, this DE system is expected to be used for wearables, such as shoe power generation, because it is not yet possible to make an energy generation element of a very large size. The problem is that this small DE generator can only generate a small amount of energy at one time. Therefore, in order to increase energy generation efficiency, it is necessary to use a material with higher conductivity for the DE electrode. Moreover, since DE energy generation is output at a high voltage, a circuit capable of stepping down with high efficiency is required in order to use this power for ordinary electric appliances. In addition to this, a circuit that... [more]

This study investigates whether natural gas exploitation is a blessing or a curse for provincial and prefecture economic growth. This study employs regression models and synthetic control methods (SCM) to investigate the research question based on hybrid panel and time-series data from 1993 to 2015 from 14 prefecture cities in Sichuan province in China. Based on the provincial data of Sichuan, the regression results show that natural gas exploitation is a curse for the provincial economic development of Sichuan because of the negative associations between gas resources and economic performance, for which the increasing rent-seeking in the province may partially account. However, the SCM results find that the local economy of Dazhou city may benefit from its sufficient natural gas resources in the short run, but it is not sustainable. Meanwhile, the gas resource has no significant contributions to the regional economic growth of Sichuan overall, which is partially attributed to the fact... [more]

MIL-53(Fe) was prepared and modified with benzoic acid to prepare MIL-53(Fe)-BA additive, which was used to improve the catalytic oxidation rate of sulfite, prevent the scaling of the desulfurization tower, and improve the desulfurization efficiency during the wet flue gas desulfurization (WFGD) process of power plants. MIL-53(Fe)-BA exhibits abundant Lewis acid sites because of the appearance of coordination unsaturated Fe atoms. Due to the excellent sorption capacity, Ca(OH)2 was used as the main SO2 desulfurizer. The composite desulfurizers were prepared by mixing MIL-53(Fe)-based additives and Ca(OH)2, and were characterized by SEM, XRD, and FT-IR. A desulfurization unit was set up at laboratory scale to study the effect of catalytic oxidation additives on sulfite oxidation and desulfurization efficiency. The results showed that the addition of MIL-53(Fe)-BA can increase the oxidation capacity of sulfite by 159%, and greatly improve the desulfurization efficiency. These composite d... [more]

Partial discharge (PD) ultrasonic detection is an early sign of the insolation defects of power transformers. The early diagnosis of PD requires the high sensitivity and reliability of ultrasonic sensing systems. For this purpose, a reformative PD ultrasonic sensing system based on phase-shifted FBG (PS-FBG) was demonstrated. By using PS-FBG as the ultrasonic sensing unit, the ultrasonic sensing system improved the response to the ultrasonic signal and overcame the electromagnetic noise. To compensate for the influence of temperature change on the ultrasonic sensing system, an automatic wavelength scanning demodulating method was carried out. The wavelength spanning strategy was optimized based on the principle of cross-correlation, in order to quicken the spanning. A PD detection test in the transformer oil was conducted, and the result shows that PS-FBG was 17.5 times more sensitive than PZT. Because of the better ultrasonic response, the proposed system was able to achieve the early... [more]

Research on the state of charge (SOC) prediction of lead−acid batteries is of great importance to the use and management of batteries. Due to this reason, this paper proposes a method for predicting the SOC of lead−acid batteries based on the improved AdaBoost model. By using the online sequence extreme learning machine (OSELM) as its weak learning machine, this model can achieve incremental learning of the model, which has a high computational efficiency, and does not require repeated training of old samples. Through improvement of the AdaBoost algorithm, the local prediction accuracy of the algorithm for the sample is enhanced, the scores of the proposed model in the maximum absolute error (AEmax) and maximum absolute percent error (APEmax) indicators are 6.8% and 8.8% lower, and the accuracy of the model is further improved. According to the verification with experimental data, when there are a large number of prediction samples, the improved AdaBoost model can reduce the prediction... [more]

Cellulose particles are among the aging products of the insulating paper that are used in power transformers. Too many cellulose particles can cause transformer accidents. Traditional research and detection methods that are used for this problem generally focus on the number and length information of cellulose particles, and it is usually difficult to quantitatively describe the spatial shape of cellulose particles. However, the shape of cellulose particles is also one of the factors affecting the safety of transformer insulation. In this paper, we successfully extracted quantitative information of the spatial shape of cellulose particles in transformer oil using an image processing technique and the transport of intensity equation, providing a new novel approach for the study and detection of the shape of cellulose particles in transformer oil.

A new approach is proposed for estimating the power efficiency of an on-field solar photovoltaics (PV) system using data from thermal imaging and weather instruments obtained using an unmanned aerial vehicle (UAV). This method is specifically designed for the non-intrusive detection of the performance of the PV system in a large-scale solar power plant that could be efficient, manpower saving, operationally safe and comprehensive. In this study, a drone instrumented with a radiometer, a thermometer and an anemometer flew at a height of 1.5 m with a maximum lateral flight speed of 3.6 m/s above the PV modules (60 cells each) with hotspots or with aging but without hotspots. The average temperatures of the PV modules were then calculated through the measured radiation intensity, ambient temperature and wind speed based on the published correlation formula. The experimental correlations were obtained by measuring over 60 aging PV modules without hot-spot damage, and the uncertainties of t... [more]

The state of charge (SOC) of the battery is an important basis for the battery management system to perform state monitoring and control decisions. In this paper, by identifying the internal parameters of the battery model at different temperatures and SOCs of the lithium-ion battery, the specific factors that affect the change of the parameters are analyzed, the segmentation basis of the model and the fitting method of related parameters are discussed, the second-order equivalent circuit model of the lithium-ion battery whose parameters vary with SOC and temperature is established, the unscented Kalman filter (UKF) is used to estimate the SOC of the lithium-ion battery, and an improved SOC estimation method based on optimized equivalent circuit model is proposed. Simulation and experimental results show that the improved SOC estimation strategy can obtain high estimation accuracy in a wide temperature range.

During the 20th century, the global energy system was mainly based on the use of fossil fuels, such as oil, natural gas, and coal [...]

Biological methanation is the production of CH4 from CO2 and H2. While this approach to carbon capture utilization have been widely researched in the recent years, there is a gap in the technology. The gap is towards the flexibility in biomethanation, utilizing biological trickling filters (BTF). With the current intermittent energy system, electricity is not a given surplus energy which will interfere with a continuous operation of biomethanation and will result in periods of operational downtime. This study investigated the effect of temperature and H2 supply during downtimes, to optimize the time needed to regain initial performance. Short (6 h), medium (24 h) and long (72 h) downtimes were investigated with combinations of three different temperatures and three different flow rates. The results from these 27 experiments showed that with the optimized parameters, it would take 60 min to reach 98.4% CH4 in the product gas for a short downtime, whereas longer downtimes needed 180 min... [more]

Diode-based HVDC link technology is considered an alternative to reduce the cost and complexity of offshore HVDC platforms. When this technology is used, the AC grid of the wind farm must be created artificially. This paper proposes an advanced frequency control method that permits forming an AC grid voltage system to connect offshore wind turbines to a diode-based HVDC link rectifier. The proposed algorithm can be easily implemented in the wind farm’s overall Power Plant Controller (PPC) without any change in the commercial wind turbine firmware. All wind turbines receive reactive power targets from the PPC to maintain the frequency and amplitude of the offshore AC line, delivering the maximum active power generated by the wind. A novel black start method is proposed to establish the wind farm’s local AC grid voltage system. The control method has been implemented and proved in an experimental setting. The black start has been successfully verified, and the frequency control algorithm... [more]

Greenhouse gases (GHG) concentration (CO2, CH4, and NOx mainly) in the Earth’s atmosphere has dramatically increased since 1960; in particular, the atmospheric CO2 levels have increased from 320 ppm to 412 ppm from 1960 to 2019 [...]

EAF steelmaking based on renewable electricity allows for low-CO2 steel production. However, the increased integration of volatile renewable energies into the energy system requires the provision of flexibility options. In view of the substantial oxygen consumption in the steel mill, flexible on-site generation and storage holds a significant potential for demand-side management. The utilization of by-product oxygen from an electrolysis plant not only contributes to load flexibility but also generates a climate-neutral fuel. In the present study, different process layouts are developed based on state-of-the-art technologies. The proposed supply systems for oxygen, hydrogen, and synthetic natural gas are subjected to design and operational optimization and assessed with respect to the overall demand-side flexibility, carbon dioxide emission reduction, and economic viability.

Marine energy resources could be crucial in meeting the increased demand for clean electricity. To enable the use of marine energy resources, developing efficient and durable offshore electrical systems is vital. Currently, there are no large-scale commercial projects with marine energy resources, and the question of how to design such electrical systems is still not settled. A natural starting point in investigating this is to draw on experiences and research from offshore wind power. This article reviews different collection grid topologies and key components for AC and DC grid structures. The review covers aspects such as the type of components, operation and estimated costs of commercially available components. A DC collection grid can be especially suitable for offshore marine energy resources, since the transmission losses are expected to be lower, and the electrical components could possibly be made smaller. Therefore, five DC collection grid topologies are proposed and qualitat... [more]

Renewable energy is predicted to play a crucial role in the energy sector as transitioning from fossil fuels to biofuels is key to achieving carbon neutrality. The comprehensive utilization of livestock manure and crop residues as a viable source of biofuels can play a significant role in Ghana’s future energy system. This current study aims to examine and predict the biofuel potential in Ghana from animal manure and crop residues. The biogas-biomethane potential of animal manure is determined using anaerobic digestion technology, whereas crop residues’ bioethanol potential is assessed using computational and analytical approaches. The findings demonstrate that animal manure biogas potential is 237.72 normal million cubic meters (NMm3). The highest manure-biogas potential per animal is from cattle (27.15 Nm3) and pigs (18.15 Nm3), while the least contribution is from chickens (1.80 Nm3). In addition, the annual bioethanol production is 3.74 gigaliters (GL), and residues from maize (0.8... [more]

The integration of distributed generation systems, including intermittent solar photovoltaic (PV) and wind, has a significant impact on the power system [...]

Nowadays, power converters with reduced cost, compact size and high efficiency are evolving to overcome the emergent challenges of renewable energy integrations. In this context, there is an increased demand for well-designed power converters in renewable energy applications to reduce energy utilization and handle a variety of loads. This paper proposes a center-tapped bridge cascaded series-resonant LC dual active bridge (DAB) converter for DC-DC conversion. The low part count of the proposed converter enables a high-power density design with reduced cost. The proposed converter offers reduced conduction losses as the reverse current is eliminated by adopting current blocking characteristics. Reverse current blocking also enables zero voltage switching (ZVS) and zero current switching (ZCS) over a wide operating range. Therefore, using a simple fixed frequency modulation (FFM) scheme offers a wide operating range compared to a conventional DAB converter. A thorough comparison of the p... [more]

Cathode precursors of lithium-NMC 811 were synthesized by the coprecipitation method using two different nickel sources, namely mixed nickel−cobalt hydroxide precipitate (MHP) and nickel sulfate. The characteristics of the synthesized precursors were compared with the characteristics of the commercial NMC 811 cathode precursor obtained from the international market. The XRD analyses identified that the diffraction peaks of the three precursor materials were in close agreement to that of Li0.05Ni0.75Co0.1Mn0.1O2, with the figure(s) of merit (FoM) of 0.81, 0.88, and 0.9, respectively, for the synthesized precursor that used MHP as the source of nickel (SM-LNMCO-811), nickel sulfate as the source of nickel (SX-LNMCO-811), and the commercial precursor (K-NMC-811). The elemental analysis of the synthesized precursors revealed the Ni:Mn:Co mol ratios of 0.8:0.08:0.12 and 0.76:0.11:0.13 for SM-LNMCO-811 and SX-LNMCO-811, respectively. The SEM analysis revealed that SX-LNMCO-811 and K-NMC-811... [more]

The construction of new wastewater treatment plants and the modernization of existing ones lead to the expansion of sewage networks, resulting in a sharp increase in the volume of municipal sewage sludge, which translates into a global problem of sludge management. The solution to this problem could be the recovery of energy from sewage sludge in the cement industry to exploit its energy potential. The aim of the present study was to examine the results of laboratory research on the production of alternative fuels based on municipal sewage sludge, plastic waste from end-of-life vehicles, and wood waste (sawdust) from carpentry enterprises. The tests were carried out for waste mixtures designated as PAZO I, PAZO II, PAZO III, and PAZO IV fuels, differing in the percentage of waste used and the type of plastic waste. The following parameters were evaluated in fuels: water content, ash content, sulfur content, and calorific value. Water content of the obtained fuels ranged from 17.1% to 1... [more]

Despite the many different methods for creating modified heat transfer surfaces to increase critical heat fluxes and heat transfer coefficients at pool boiling of various liquids at given reduced pressures, active research is currently underway to find optimal surface morphology and geometric parameters of structures for practical application. In this work, we used the method of microarc oxidation (MAO) to obtain coatings with different microstructures on the surface of duralumin heaters. In the present work, we studied the effect of MAO coatings on heat transfer, critical heat flux, and evaporation dynamics during liquid nitrogen boiling under conditions of steady-state heat release at pressures of 0.1, 0.05, and 0.017 MPa. It was shown that the modification of heaters led to a 50−60% increase in heat transfer coefficients as compared to the smooth one under the atmospheric pressure. Based on the data of high-speed video filming of boiling, it was shown that the main mechanism of inte... [more]

Oil shale constitutes an important proportion of unconventional resources, and its efficient exploitation helps alleviate the Chinese oil shortage situation. Nowadays, microwave heating is a promising method for in situ development of oil shale. However, the corresponding numerical simulation lacks in guiding the retorting optimization under microwave heating. A novel pseudo three-dimensional model, considering electromagnetics, temperature field, and chemical reactions coupling was developed and implemented to investigate oil shale reservoirs’ retorting performance under microwave heating based on the finite element method (FEM). The effects of microwave power, antenna number, and antenna position were analyzed creatively to optimize the microwave heating parameters. Numerical results showed high microwave power increased the maximum reservoir temperature quickly near the heating well, but the thermal conductivity of oil shale dominated the temperature of distal formation. For a typic... [more]

Wind turbines (WTs) are exposed to a dynamic/cyclic load environment, and are subjected to 1P/3P loads under operational conditions. Recent studies introduced the Sommerfeld Effect to explain the dynamic response amplification induced by 1P/3P loads. This study establishes a theoretical model to analyze the resonance of WTs under 1P/3P loads. Sensitiveness analysis was conducted for parameters b, c, S, F, and T to explore their influence on the dynamic response. The resonance phenomenon induced by 1P/3P frequency passing the natural frequency is discussed. The results show that there is no Sommerfeld Effect in soft−stiff WTs. Only if the imbalance reaches a much higher value (19200 kg·m in this study) should the Sommerfeld Effect be considered for soft WTs; otherwise, it can be ignored. The 3P resonance appeared when the 3P frequency approached the natural frequency, but it was not the Sommerfeld Effect.

As an emerging foundation structure for offshore wind turbines, bucket foundations with superior bearing capacities and efficient construction procedures have attracted significant attention in China. Thick-walled bucket foundations with concrete skirts can effectively reduce the cost and prevent the buckling problem of steel skirts during construction, transportation, and installation. However, great challenges are encountered during the sinking process, and the accurate calculation of sinking resistance is a critical process. Static-pressure tests of thin-walled and thick-walled models in sand were performed to measure the penetration resistance and soil pressure at the sidewalls and ends. The horizontal-soil-pressure coefficients of different models were calculated, and the end and skin-friction coefficients in the cone-penetration test method are recommended. The drag-reduction effects of the anti-drag ring and pressure-pull-out loading method were examined, and the drag-reduction... [more]

Converting municipal solid waste (MSW) into valuable feedstocks, such as refuse-derived fuel (RDF), is a sustainable method according to the concept of waste management hierarchy. A heterogeneous composition with a good calorific value and lower emissions allows RDF to be used for energy recovery purposes. We have earlier analyzed the generation and thermochemical characteristics of the MSW produced in Kazakhstan. This work aims to study the combustion characteristics in terms of emissions and ash composition to evaluate the possibility of RDF co-firing with Ekibastuz coal. In particular, RDF is blended with high ash bituminous coal (Ekibastuz coal) and co-fired in the laboratory scale bubbling fluidized bed reactor (BFB) at a bed temperature of 850 °C. The co-firing tests of RDF to coal samples were conducted under various proportions to analyze flue gas compositions. Experiments were carried in the presence of bed material (sand), and the fuel particles were fed in batch mode into th... [more]