The energy industry has been trying to reduce the use of fossil fuels that emit carbon and to proliferate renewable energy as a way to respond to climate change. The attempts to reduce carbon emissions resulting from the process of generating the electric and thermal energy needed by a building were bolstered with the introduction of the concept of nZEB (nearly zero-energy building). In line with such initiatives, the South Korean government made it mandatory for new buildings to have an nZEB certificate as a way to promote the supply of renewable energy. The criteria for Energy Independence Rate, which is one of the nZEB certification criteria in South Korea, is to maintain the share of renewable energy as at least 20% of the primary energy sources for the building. For a new building in South Korea to have an nZEB certificate, it is required to establish an energy plan that would allow the building to meet the Energy Independence requirement. This optimally reflects the cost of insta... [more]

The importance of biogas in the energy mix in Poland and Latvia is very low. In Poland, 306 million m3 of biogas is produced annually, and in Latvia, 56 million m3. The share of energy from agricultural biogas in Latvia is 1.6%, and in Poland, only 0.12%. This study analyzed the impact of the structure on CO2 emissions from agricultural biogas production in Latvia and Poland. The emission was determined in accordance with the EU directive. The structure of substrates was dominated by those from the second generation, i.e., manure and food waste. In Latvia, it was 70%, and in Poland, 78%. The manure share was 45% and 24%, respectively. The anaerobic digestion of manure guarantees high GHG savings thanks to the avoided emissions from the traditional storage and management of raw manure as organic fertilizer. The level of emissions from the production of agricultural biogas was calculated for the variant with the use of closed digestate tanks, and it was about 10−11 g CO2/MJ, which is com... [more]

South Africa is one of the most carbon-intensive economies in the world, but it is presently experiencing an energy crisis, as its utility company cannot meet the country’s energy demands. The use of renewable energy sources and retiring of coal-fired power stations are two important ways of alleviating this problem, as well as decarbonizing the grid. Repurposing retiring coal-fired power stations for renewable energy generation (RCP-RES) while maintaining energy sustainability and reliability has rarely been researched. This paper proposes macro- and microelements for repurposing retiring coal-fired power stations for renewable energy generation in Camden with the aim of improving power generation through a low-carbon system. In this model, concentrated solar power (CSP) and solar photovoltaics (SPV), in combination with storage technologies (STs), were employed for RCP-RES, owing to their excellent levels of availability in the retiring fleet regions. The simulation results show that... [more]

In this paper, a thorough 2D unsteady computational fluid dynamic analysis was performed on a pitching airfoil to properly comprehend the dynamic stall and aerodynamic forces. The computational software ANSYS Fluent was used to solve the unsteady Reynolds-averaged Navier−Stokes equations. Low Reynolds number flows were modeled using the k-ω shear stress transport turbulence model. Aerodynamic forces, fluid flow structures, and flow separation delay angles were explored as a function of the Reynolds number, reduced frequency, oscillation amplitude, and mean angle of attack. The maximum aerodynamic forces, including lift, drag, and the onset of the dynamic stall, were all influenced by these variables. The critical parameters that influenced the optimum aerodynamic forces and ended up causing dynamic stall delay were oscillation amplitude and mean angle of attack. The stall angle was raised by 9° and 6°, respectively, and a large increment in the lift coefficient was also noted in both c... [more]

One of the unconventional, innovative ways of using biomass is using it as a component of high-energy material. According to conceptual assumptions, biomass can act as an energy carrier in modified high-energy materials-explosives (EX). Modification of the composition of the explosive requires the development of a method of introducing an additional component and changes its explosive and operational parameters (including safety). Thermodynamic calculation programs allow you to model the predicted energetic parameters of an explosive in order to select prospective compositions without the need to carry out a large number of costly and time-consuming field tests. This enables more effective design of new explosives compositions by narrowing down the scope of field tests using the “in situ” method. The use of renewable biomass as a corrector of EX properties may be a pro-environmental approach and reduces the production costs of the product. The thermodynamic simulations performed showed... [more]

Artificial intelligence (AI) constitutes a kind of modelling method widely used in various fields of science including energy and environmental engineering [...]

The tight sandstone reservoir in the Qianfoya formation of well PL-3 of the Puguang gas field in Sichuan, China, obtained a high-yield gas flow after a volume fracturing treatment. However, the stimulated reservoir volume (SRV), fracture morphology, scale and formation law still remain unclear. Based on particle flow discrete-element theory in this paper, we carried out a few trials of the Brazilian splitting test, uniaxial compression and triaxial compression of rock mechanics. Meanwhile, the research also testified to the conversion relationship between macroparameters and microparameters, established the numerical simulation on hydraulic fracturing through PFC2D discrete element software, and finally analyzed the influence of difference coefficients on the fracturing effect, in terms of different in-situ stresses. The conclusions are as follows: firstly, the influence of in-situ stress is essential for the direction, shape and quantity of fracture propagation, and the fractures gene... [more]

In this paper, the combustion behavior of low rank coal and its product after hydrothermal carbonization with paper sludge hydrochar were studied. The Raman technique was used to compare the structural differences between raw coal and the product. Thermogravimetric analysis was employed to conduct experiments of single sample and their mixtures with different proportions at a heating rate of 20 °C/min, the activation energy of chemical reactions was calculated. The results showed that upgraded product had higher carbon ordering degree than raw coal and the ignition temperature and burnout temperature of the product were advanced. Compared with raw coal, the combustion characteristic parameters C and S of the product were higher, indicating that its combustibility was better. As for the mixture, when the paper sludge hydrochar ratio was not more than 10%, the mixed fuel combustion curve was still similar to coal curve. After the paper sludge hydrochar ratio exceeded 10%, the activation... [more]

Quantitative estimates of reservoir parameters and elastic anisotropy using seismic methods is essential for characterizing shale oil reservoirs. Rock physics models were established to quantify elastic anisotropy associated with clay properties, laminated microstructures, and bedding fractures at different scales in shale. The inversion schemes based on the built rock physics models were proposed to estimate reservoir parameters and elastic anisotropy using well log data. Based on the back propagation neural network framework, the obtained rock physical inversion results were used to establish the nonlinear models between elastic properties and reservoir parameters and elastic anisotropy of shale. The established correlations were applied for quantitative seismic interpretation, converting seismic inversion results to the reservoir parameters and elastic anisotropy to characterize the shale oil reservoir comprehensively. The predicted elastic anisotropy of the shale matrix reflects th... [more]

High-energy consumption globally has raised questions about the low environmentally friendly and high-cost processes used until now for energy production. Microbial fuel cells (MFCs) may support alternative more economically and environmentally favorable ways of bioenergy production based on their advantage of using waste. MFCs work as bio-electrochemical devices that consume organic substrates in order for the electrogenic bacteria and/or enzyme cultures to produce electricity and simultaneously lower the environmental hazardous value of waste such as COD. The utilization of organic waste as fuels in MFCs has opened a new research path for testing a variety of by-products from several industry sectors. This review presents several organic waste substrates that can be employed as fuels in MFCs for bioenergy generation and the effect of their usage on power density, COD (chemical oxygen demand) removal, and Coulombic efficiency enhancement. Moreover, a demonstration and comparison of th... [more]

Unrenovated multifamily houses in Germany are mostly heated by fossil heat generators; therefore, measures are required for CO2 emission reduction. The use of air−water heat pumps is restricted by high required flow temperatures and heat output but can be mitigated by hybrid heat pumps. To limit additional operation costs by the heat pump, a new operation strategy is introduced in this study, which allows to maintain a target CO2 emission. The operation strategy is applied in a field trial in a small unrenovated multifamily house built in 1964. A thermohydraulic simulation model is verified and is used in full-year simulations to apply improvement measures and compare the new control strategy with existing optimizing strategies. The results show that the control onto target emissions is possible and limits additional costs but can also result in higher CO2 mitigation costs, making it less favorable. The hybrid heat pump reduces the direct fossil CO2 emissions by 61% (in total by 22%);... [more]

Mass and cost tradeoffs by deploying three optimized spars, made of all-glass, hybrid and all-carbon composites, applied to a publicly available large-scale composite blade of 100 m in length for a 13.2 MW wind turbine, are explored. The blade mass and cost minimizations are calculated for two design load cases, generating the worst aerodynamic loads for parked and rotating rotor blades, while meeting the stiffness, strength, stability and resonance design requirements, as recommended by the wind turbine standards. The optimization cases are formulated as a single-objective, multi-constraint optimization problem, while taking into account the manufacturability of hybrid spars in particular, and it is solved using a genetic algorithm method. The blade mass lowers in the range of 8.1−13.3%, 18.5−20.7% and 25.7−26.4% for the optimized all-glass, hybrid and all-carbon spars, respectively, while the cost decreases for the optimized all-glass spars only. The cost increases in a range of 1.2−... [more]

The growing worldwide costs of energy produced as a result of conventional fuel combustion, the limited capacity of the distribution grid, and the growing number of unstable installations based on renewable energy sources increase the need to implement systems of stabilization and regulate loads for end users. The battery energy storage system (BESS) that operates in the internal microgrid of an enterprise enables the management of the accumulated energy in any time zone of the day. Using a price arbitrage strategy with an electricity storage facility, we can reduce the cost of high electricity prices during peak demand periods. This study aims to determine the most effective method of setting up the capacity and electrical power of an energy storage system operating in a microgrid, in an enterprise to implement a price arbitration strategy. Such a method should include consideration of the characteristics of the demand profile of consumer systems, the charges related to electricity, a... [more]

The emergence of DC fast chargers for electric vehicle batteries (EVBs) has prompted the design of ad-hoc microgrids (MGs), in which the use of a solid-state transformer (SST) instead of a low-frequency service transformer can increase the efficiency and reduce the volume and weight of the MG electrical architecture. Mimicking a conventional gasoline station in terms of service duration and service simultaneity to several customers has led to the notion of ultra-fast chargers, in which the charging time is less than 10 min and the MG power is higher than 350 kW. This survey reviews the state-of-the-art of DC ultra-fast charging stations, SST transformers, and DC ultra-fast charging stations based on SST. Ultra-fast charging definition and its requirements are analyzed, and SST characteristics and applications together with the configuration of power electronic converters in SST-based ultra-fast charging stations are described. A new classification of topologies for DC SST-based ultra-f... [more]

In recent years, DC power supply and distribution technology plays an increasingly significant role in power supply and distribution systems with a low loss and large power supply radius. However, the corresponding DC distribution network protection electric devices cannot satisfy the needs of the existing DC power supply and distribution network. Based on this, in this article, an intelligent/energy-efficient DC leakage protection circuit breaker based on two-phase magnetic nanomaterials and detection and control technology is proposed. Firstly, the core of an intelligent/energy-efficient DCCB is composed of two-phase magnetic nanomaterials, and the mathematical modeling process, preparation and processing method of two-phase magnetic nanomaterials are given. Secondly, the DC leakage detection technology is studied by fluxgate technology, and the design process of magnetic rings, winding and detection circuit is given. Thirdly, the simulation and experiment results of the detection sy... [more]

This study evaluates the technical, economic and environmental benefits of renewable energy resources (RER) for electricity supply to large size buildings in an educational institution. The cost of energy generation coupled with the epileptic power supply has led to the demand for an alternative source of energy supply to an education institution in Nigeria. The essence of renewable energy generation is becoming more glaring and a hybrid energy system (HES) is believed to deliver efficient and sustainable energy for the institutions; this paper aims to analyse the techno-economic assessment of a HES design setup at the College of Engineering, Afe Babalola University Ado-Ekiti for powering the university buildings; this grid connected system was assessed with various system configurations was simulated using hybrid optimization model for electric renewables (HOMER) software and the levelized cost of energy (LCOE) with the consideration of the HES benefits was developed. The results obta... [more]

This paper proposes an active-clamp forward-flyback (ACFF) converter with an integrated planar transformer for wide-input voltage and high-output current applications, such as low-voltage direct-current (LDC) converters in electric vehicles. An integrated planar transformer that consists of a forward-flyback transformer, single primary winding, and efficient structure of secondary windings is adopted for the proposed converter, and since this transformer is implemented with a common four-layer printed circuit board (PCB) winding, a high power density and low cost of the proposed converter can be achieved. In addition, due to the low leakage inductance induced by the planar transformer, a reduced commutation period can be achieved, and it is possible to increase the switching frequency resulting in low volume of transformer. Although the integrated planar transformer has relatively high conduction loss, the active-clamp topology can significantly reduce the conduction loss on switches c... [more]

Inductive power transfer (IPT) technology offers a promising solution for electric vehicle (EV) charging. It permits an EV to charge its energy storage system without any physical connections using magnetic coupling between inductive coils. EV inductive charging is an exemplary option due to the related merits such as: automatic operation, safety in harsh climatic conditions, interoperability, and flexibility. There are three visions to realize wireless EV charging: (i) static, in which charging occurs while EV is in long-term parking; (ii) dynamic (in-motion), which happens when EV is moving at high speed; and (iii) quasi-dynamic, which can occur when EV is at transient stops or driving at low speed. This paper introduces an extensive review for IPT systems in dynamic EV charging. It offers the state-of-the-art of transmitter design, including magnetic structure and supply arrangement. It explores and summarizes various types of compensation networks, power converters, and control tec... [more]

The effective use of robotic manipulators is particularly important when carrying out hazardous tasks. Often, for this type of mission, manipulators equipped with a hydraulic drive system are used, and their work results primarily from the implementation of precise movements through their effectors. In heavy manipulators, limiting the uncontrolled movement resulting from high inertia and relatively low stiffness has an impact on the improvement of the control precision. Therefore, the paper presents experimental studies that allow the assessment of the impact of the use of counterbalance valves on the precision and dynamics of a manipulator with a hydrostatic drive system. The tests were carried out for a wide range of effector velocities along a horizontal trajectory, on the basis of which, it was found that it was possible to improve the precision and dynamics of the work of such manipulators due to the precision of the trajectory and pressures in the drive system.

The two main research goals of this study are to develop a relationship diagram between the parameters of reliability and maintainability and to investigate the impact of reliability and maintenance on engineering design costs. In this study, we use the theory of reliability and maintainability parameters to derive the relationship between the parameters using block diagrams. Compared with onshore wind farms, offshore wind farms have higher reliability requirements, but the maintenance degree of offshore wind farms is lower due to environmental factors. This study proposes an important concept of reliability and maintenance for value engineering, which can help system design engineers and project engineers integrate reliability concerns in the design phase and operation and maintenance phase.

Smart cities can be made into super-smart cities through IoT devices’ implication of energy-efficient 6G. IoT devices are expected to reach fifty billion, but limited information is available regarding the energy-efficient 6G wireless communication standard. This article highlights the key technologies, applications, and trends in the Internet of Things (IoT) for energy-efficient 6G wireless communication in smart cities. The systematic review helped to achieve the aim of the study by considering the 20 articles extracted from databases and Google that fell between 2015 and 2021 and are written in English. The findings identified that quantum communication, blockchain, visible light communication (VLC), 6G brain−computer interface (BCI), symbiotic radio, and others are the key technologies. The applications of IoT technologies and energy-efficient 6G are found in 15 Minute City, Industrial Town, Intelligent Transport systems and others. Furthermore, the trend of using 6G through IoT de... [more]

Although they are of significant importance for environmental applications, the industrialization of photocatalytic techniques still faces many difficulties, and the most urgent concern is cost control. Natural minerals possess abundant chemical inertia and cost-efficiency, which is suitable for hybridizing with various effective photocatalysts. The use of natural minerals in photocatalytic systems can not only significantly decrease the pure photocatalyst dosage but can also produce a favorable synergistic effect between photocatalyst and mineral substrate. This review article discusses the current progress regarding the use of various mineral classes in photocatalytic applications. Owing to their unique structures, large surface area, and negatively charged surface, silicate minerals could enhance the adsorption capacity, reduce particle aggregation, and promote photogenerated electron-hole pair separation for hybrid photocatalysts. Moreover, controlling the morphology and structure... [more]

Solar thermal energy coupled to a seasonal sorption storage system stands as an alternative to fossil fuels to supply residential thermal energy demand in climates where solar energy availability is high in summer and low in winter, matching with a high space heating demand. Sorption storage systems usually have a high dependency on weather conditions (ambient temperature and solar irradiation). Therefore, in this study, the technical performance of a solar-driven seasonal sorption storage system, using an innovative composite sorbent and water as working fluid, was studied under three European climates, represented by: Paris, Munich, and Stockholm. All scenarios analyses were simulation-based under optimal system control, which allowed to maximize the system competitiveness by minimizing the system operational costs. The optimal scenarios profit from just 91, 82 and 76% of the total sorption system capacity, for Paris, Munich, and Stockholm, respectively. That means that an optimal co... [more]

This study investigates a combined power generation and cooling system comprising an organic Rankine cycle (ORC) and a vapor compression cycle (VCC). Thermodynamic analyses of the system were conducted for two operation modes, i.e., the basic ORC mode and the ORC−VCC mode, using six different working fluids: R245fa, R114, R600, R142b, R152a, and R1234yf. The results showed that the thermal efficiency of the combined ORC−VCC system was almost twice that of the basic ORC system. The effects of thermodynamic parameters, such as the turbine inlet temperature and pressure and the condensing temperature, on the system performance were discussed. The second-law efficiency, cooling capacity, and coefficient of performance were addressed by varying the condensing temperature.

Although pre-stack inversion has been carried out on reservoir prediction, few studies have focused on the application of pre-stack for seismic inversion in fractured-cavity carbonate reservoirs. In carbonate rock, complicated combinations and fluid predictions in karst caves are remain unclear. Post-stack methods are commonly used to predict the position, size, and fillings of caves, but pre-stack inversion is seldom applied in carbonate karst reservoirs. This paper proposes a pre-stack inversion method for forward modeling data and oil survey seismic data, using both points to indicate the application of pre-stack inversion in karst caves. Considering influence of cave size, depth, and filler on prediction, three sets of models (different caves volume; different fillings velocity of caves; complicated combination of caves) are employed and inverted by pre-stack inversion. We analyze the pre-stack results to depict Ordovician oil bearing and characterize caves. Geological model parame... [more]