Due to the increasing energy crisis and environmental pollution, the development of drive motors for new energy vehicles (NEVs) has become the focus of popular attention. To improve the sine of the air-gap flux density and flux regulation capacity of drive motors, a new hybrid excitation synchronous motor (HESM) has been proposed. The HESM adopts a salient pole rotor with built-in dual-V permanent magnets (PMs), non-arc pole shoes and excitation windings. The fundamental topology, operating principle and analytical model for a magnetic field are presented. In the analytical model, the rotor magnetomotive force (MMF) is derived based on the minimum reluctance principle, and the permeance function considering a non-uniform air-gap is calculated using the magnetic equivalent circuit (MEC) method. Besides, the electromagnetic performance including the air-gap magnetic field and flux regulation capacity is analyzed by the finite element method (FEM). The simulation results of the air-gap ma... [more]

This contribution is focused on the fuel economy improvement of the Miller cycle under part-load characteristics on a supercharged DI (Direct Injection) gasoline engine. Firstly, based on the engine bench test, the effects with the Miller cycle application under 3000 rpm were studied. The results show that the Miller cycle has different extents of improvement on pumping loss, combustion and friction loss. For low, medium and high loads, the brake thermal efficiency of the baseline engine is increased by 2.8%, 2.5% and 2.6%, respectively. Besides, the baseline variable valve timing (VVT) is optimized by the test. Subsequently, the 1D CFD (Computational Fluid Dynamics) model of the Miller cycle engine after the test optimization at the working condition of 3000 rpm and BMEP (Brake Mean Effective Pressure) = 10 bar was established, and the influence of the combined change of intake and exhaust valve timing on Miller cycle was studied by simulation. The results show that as the effect of t... [more]

Power conversion systems based on the Organic Rankine Cycle (ORC) have been identified as a potential technology especially in converting low-grade renewable sources or waste heat. However, it is necessary to improve efficiency of ORC systems. This paper focuses on use of low geothermal resources (for temperature range of 80−128 °C and mass flow 100 kg/s) by using modified ORC. A modification of conventional binary power plant is conducted by combining gas turbines to increase quality of steam from a geothermal well. An analysis has been conducted for three different working fluids: R245fa, R1233zd(E) and R600. The paper discusses the impact of parameter changes not only on system efficiency but on other performance indicators. The results were compared with a conventional geothermal Organic Rankine Cycle (ORC). Increasing of geothermal steam quality by supplying exhaust gas from a gas turbine to the installation has a positive effect on the system efficiency and power. The highest eff... [more]

Horizontal wells with multi-stage fractures have been widely used to improve coalbed methane (CBM) production from coalbed methane reservoirs. The main focus of this work is to establish a new semi-analytical method in the Laplace domain and investigate the transient pressure behavior in coalbed methane reservoirs. With the new semi-analytical method, flow regimes of a multi-fractured horizontal well in coalbed methane reservoirs were identified. In addition, the sensitivities of fracture conductivity, diffusion model, storability ratio, inter-porosity flow coefficient, adsorption index, fracture spacing, fracture asymmetry, non-planar angle, and wellbore storage were studied. Results indicate that six characteristic flow regimes can be identified for multi-fractured horizontal wells in coalbed methane reservoirs, which are bilinear flow, first linear flow, desorption-diffusion flow, first pseudo-radial flow, second linear flow, and second pseudo-radial flow. Furthermore, the sensitivi... [more]

Sugarcane harvesting requires a significant amount of energy and time to manage dry leaves after the harvesting process. Therefore, the objective of this study was to minimize the energy requirement to process the cane and dry leaves’ harvesting (CDLH) for sugarcane while, at the same time, maximizing sugar production from cane and energy from dry leaves in Sri Lanka. The CDLH was conceptualized using a novel approach to optimize sugarcane harvesting to maximize biomass supply for energy production while reducing supply chain sugar-loss. The CDLH was investigated for manual harvesting capacity, energy consumption, sugar loss, and biomass energy potential. It was observed that CDLH consumed higher energy compared to the present practices of harvesting. However, the energy used for fieldwork was reduced because of the shifting of cane chopping and cleaning from the field to the factory. Low bulk density of the harvested cane of the CDLH system had a higher energy requirement in transport... [more]

This paper presents a novel maximum power point tracking method for photovoltaic inverters with a single phase connection to the onboard 400Hz vehicle or aircraft grid, supplying drives operating in a critical mode. By taking into account that the power fluctuations cause voltage ripples at the termini of photovoltaic panels connected to the DC-link capacitor, this paper proposes a conductance base maximum power point tracking method. The impact of varying voltage has been reduced to ensure the constant reference current for the grid current calculation problem, which has been reported in previous studies. Accordingly, a conductance base tracking method, grid current control, is proposed and implemented to ensure the expected output current with respect to varying power. As described in this paper, the exemplified solar converter prototype can implement constant reference photovoltaic current control with a maximum power point achievement under continuous voltage rippling. Experimental... [more]

Bioenergy accounts for 61.7% of all renewable energy sources, with solid fuels accounting for 43% of this amount. Poplar plantations can deliver woody biomass for energy purposes. A field experiment with poplar was located in the north-east of Poland on good quality soil formed from medium loam. The study aimed to determine the yield, the energy value of the yield and the thermophysical properties and elemental composition of the biomass of four poplar clones harvested in two consecutive 4-year harvest rotations. The highest biomass energy value was determined in the UWM 2 clone in the second harvest rotation (231 GJ ha−1·year−1). This value was 27−47% lower for the other clones. The biomass quality showed that poplar wood contained high levels of moisture and low levels of ash, sulphur, nitrogen and chlorine. This indicates that poplar can be grown in the north-east of Poland and that it gives a yield with a high energy value and beneficial biomass properties from the energy generatio... [more]

This study investigates the effects of Angola’s agricultural, manufacturing, and mineral exports on the country’s economic growth using data from 1980 to 2017. An Autoregressive Distributed Lag (ARDL) model is employed to estimate the effect of sectoral exports on economic growth. The estimation results show that while exports from all three sectors (manufacturing, mineral, and non-mineral) have driven Angola’s economic growth in the long-run; only non-manufacturing (agricultural and mineral) exports have led its growth in the short-run. Moreover, growth in non-export GDP was driven by mineral exports in the long-run and agricultural exports in the short-run. Considering the statistically significant and positive impact of mineral exports on the Angolan GDP as well as on its non-export GDP, this study points to a lack of evidence supporting the Dutch disease phenomenon in Angola.

In this review, we focus on the literature that described the various unit operations in a process design flowsheet of biorefineries. We begin by establishing the accepted definitions of a biorefinery, go on to describe how to categorize biorefineries, and finally review the literature on biorefinery process designs by listing the unit operation in each process design. Distinguishing biorefineries based on feedstock, the types of processing units, and the products emanating from the biorefinery are discussed.

The task of the whole microgrid state-space matrix creation is usually done in a preferred textual programming language, and it presents a complicated, time-consuming, and error-prone job for a researcher without good coding practices. To ease the modeling task, contribute to the adaptation of new microgrid structures, control algorithms, and devices, and to improve the flexibility of the model, a graphical element building block method is proposed in this paper. With the proposed approach model creation of the whole microgrid is reduced to the creation of the individual element state-space model that is linked with other elements in a logical way with a graphical connection. Elements are then grouped into meaningful wholes and encapsulated with the appropriate graphical user interface that enables easy parameter modification and model complexity change. More detailed DC/DC and DC/AC models of converters than those in the literature concerning microgrid stability are presented in this... [more]

Shale oil exploration has been a key area of onshore oil and gas exploration in China in recent years. In this study, organic geochemistry and element geochemistry are united to study the shale oil and source rock in the Lucaogou formation of Jimusar sag, in order to reveal the paleoclimate, paleoenvironment, source of organic matter, and factors affecting organic matter accumulation and shale oil generation. The shale oil in the study area is mainly accumulated in two strata with good reservoir properties and oiliness, known as the upper sweet spot and lower sweet spot. Indexes of biomarkers and sensitive elements revealed the warm and semi-arid paleoclimate during Lucaogou formation, and the water column was brackish to salty. Water stratification caused a suboxic to anoxic environment in the deep-water column and coincided with the anoxic photic zone phenomenon. Compared with the lower sweet spot, the more humid climate, deeper and fresher water, and stronger water stratification ch... [more]

In the present paper, the effect of temperature on the shape of magnetic hysteresis loops for a magnetocaloric composite core was studied. The composite core, based on La(Fe, Mn, Si)13-H, was set up using three component disks with different Curie temperatures. The magnetic properties of the components and the outcome composite core were determined using a self-developed measurement setup. For the description of hysteresis loops, the phenomenological T(x) model was used. The presented methodology might be useful for the designers of magnetic active regenerators.

After over 20 years of development in Daqingzijiang Oilfield, isolated sand bodies under the delta front and pro-delta in the Qingshankou Formation(qn)have become important oil and gas reservoir bodies. However, the cause for large amounts of isolated bar sand bodies in the lake-basin delta sediment system has not been reported in China. This article, through core observation, reveals plenty of evidence that there storm waves once existed. Combined with paleogeography and hydrodynamic force analysis, it describes the transformation effect of waves on delta sand bodies and on the formation mechanism of bar sand bodies. Based on a study on paleogeomorphology and the statistics of sand body distribution, we consider ‘Storm waves conveying sand’ and ‘landform controlling sand’ as the cause and distribution model of the delta’s isolated bar sand body formation. We also think that the superposition of multiple bar sand bodies is the direct cause of the strong anisotropy in reservoirs and the... [more]

The introduction of transshipment ports in the liquefied natural gas (LNG) supply chain in recent years offers additional flexibility, but also challenges to the planning of the annual delivery program. We present a new variant of the LNG-annual delivery program (ADP) planning problem by considering transshipment as well as time-dependent sailing times. We present a continuous time formulation for the LNG-ADP problem and propose a rolling horizon heuristic to solve the problem. Both the model and heuristic were used to solve a case inspired by the Yamal LNG project. The computational results show that the heuristic provides good solutions within a relatively short amount of time, especially compared to the exact solution methods. However, there is a trade-off between computational time and solution quality when designing the rolling horizon heuristic. The results also show the impact storage capacity at the transshipment port has on the total cost.

Dilithium manganese oxide (LMO) thin film was newly fabricated as an active material on a fluorinated-tin-oxide pre-coated glass electrode by a wet process. A stable LMO precursor solution was developed through the reaction of lithium and manganese acetates with butylamine in ethanol. A spin-coated precursor film was heat-treated at 500 °C in air for 0.5 h. The X-ray diffraction pattern indicates that the resultant film consists of layer-structured LMO crystals. The X-ray photoelectron spectra of LMO thin film suggests that the ratio of Mn3+/Mn4+ is 1/4, and the chemical formula can be expressed as Li2MnO2.9. A device was assembled with O-deficient LMO and TiO2 thin films as each active material, along with an electrolytic solution involving LiPF6. The charging voltages (2.67 and 1.45 V) of this device were recorded by applying a constant current of 0.2 mA and using 1-sun irradiation with no external power supply, respectively. The voltages delivered by this cobalt-free device were 0.6... [more]

Rural areas of developing countries often have poor energy infrastructure and so rely on a very local supply. A local energy supply in rural Uganda frequently has problems such as limited accessibility, unreliability, a high expense, harmful to health and deforestation. By carbonizing waste biomass streams, available to those in rural areas of developing countries through a solar resource, it would be possible to create stable, reliable fuels with more consistent calorific values. An energy demand calculator is reported to assess the different energy demands of various thermochemical processes that can be used to create biofuel. The energy demand calculator then relates the energy required to the area of solar collector required for an integrated system. Pyrolysis was shown to require the least amount of energy to process 1 kg of biomass when compared to steam treatment and hydrothermal carbonization (HTC). This was due to the large amount of water required for steam treatment and HTC.... [more]

As a promising alternative renewable liquid fuel, biodiesel production has increased and eventually led to an increase in the production of its by-product, crude glycerol. The vast generation of glycerol has surpassed the market demand. Hence, the crude glycerol produced should be utilized effectively to increase the viability of biodiesel production. One of them is through crude glycerol upgrading, which is not economical. A good deal of attention has been dedicated to research for alternative material and chemicals derived from sustainable biomass resources. It will be more valuable if the crude glycerol is converted into glycerol derivatives, and so, increase the economic possibility of the biodiesel production. Studies showed that glycerol carbonate plays an important role, as a building block, in synthesizing the glycerol oligomers at milder conditions under microwave irradiation. This review presents a brief outline of the physio-chemical, thermodynamic, toxicological, production... [more]

Based on wind lidar, a novel yaw control scheme was designed that utilizes forecast wind information. The new scheme can reduce the power loss caused by the lag of accurate measurement data in the traditional yaw control strategy. A theoretical analysis of the power loss caused by the traditional wind measurement inherent error and the wind direction based traditional yaw control strategy was conducted. The yaw angle error and yaw stop/start frequency in an actual wind field were statistically analyzed, and a novel Long Short Term-Neural Network (LSTM-NN) yaw control strategy based on wind lidar information was proposed. An accurate forecast of the wind direction could reduce the power loss caused by the inherent yaw misalignment, while an accurate forecast of wind speed could increase the stop/start frequency in the medium speed section within the partial load range and reduce the frequency in the low speed section within the partial load range. Thus, the power captured could be incre... [more]

A magnetic nano-solid acid catalyst Fe3O4-PDA-SO3H was synthetized through an efficient method, as an eco-friendly and more efficient catalyst. The obtained catalyst has uniform core-shell structure, appropriate particle size, and high acid density. Fe3O4-PDA-SO3H was applied to catalyze the esterification of levulinic acid (LA) with alcohols of different chain length to produce the levulinate esters. The catalytic effect was optimized from the aspects of catalyst dosage, reaction temperature, and acid-alcohol molar ratio. Furthermore, the response surface optimization method was used to obtain the optimal conditions. Verified under these conditions, the experimental results showed that the conversion rate of LA can reach 95.87%, which was much higher than common cationic exchange resin Amberlyst 36 and Amberlyst 46. Furthermore, the recovery and reuse of the Fe3O4-PDA-SO3H was demonstrated six times without obvious loss in the activity.

The performance, energy storage capacity, safety, and lifetime of lithium-ion battery cells of different chemistries are very sensitive to operating and environmental temperatures. The cells generate heat by current passing through their internal resistances, and chemical reactions can generate additional, sometimes uncontrollable, heat if the temperature within the cells reaches the trigger temperature. Therefore, a high-performance battery cooling system that maintains cells as close to the ideal temperature as possible is needed to enable the highest possible discharge current rates while still providing a sufficient safety margin. This paper presents a novel design, preliminary development, and results for an inexpensive reusable, liquid-cooled, modular, hexagonal battery module that may be suitable for some mobile and stationary applications that have high charge and or discharge rate requirements. The battery temperature rise was measured experimentally for a six parallel 18650 c... [more]

The authors studied the impact of indoor air humidity in the range of 60% to 90% on building user perception in the temperature range of 26 to 28 °C. The research thesis was put forward that the impact of humidity on indoor air quality dissatisfaction of building users in a warm and humid indoor environment is greater than that indicated in thermal comfort models. The presented experiment examined the indoor air quality perception of n = 28 subjects in the test chamber of a nearly zero energy building under ten environmental conditions, together with a thermal comfort assessment. The authors developed an experimental relation for predicting building users’ satisfaction based on the Weber−Fechner law, where the predicted percentage of dissatisfied users (PD) is determined by means of air enthalpy (h), PD = f(h). The obtained results confirmed the sated thesis. Additionally, the intersection points of the experimental function and isotherms resulting from the Fanger model are presented,... [more]

The steady-state injection characteristic of gas fuel injector is one of the key factors that affects the performance of gas fuel engine. The influences of different injection strategies, such as different injection angles and different injection positions, on the mixing performance in gas-fueled engine have been emphasized in previous literatures. However, the research on the injection characteristics of the gas fuel injector itself are insufficient. The three-dimensional steady-state computational fluid dynamics (CFD) models of two kinds of injectors, in different opening manners, and the other two kinds of injectors, in different sealing methods, were established in this paper. The core region speed, stagnation pressure loss and mass flow rate were compared. Additionally, the effective injection pressure (EIP) concept was also used to evaluate the injection efficiency of gas fuel injector. The simulation results show that the jet speed of the pull-open injector is higher than the pu... [more]

Rising demand and limited production of electricity are instrumental in spreading the awareness of cautious energy use, leading to the global demand for energy-efficient buildings. This compels the construction industry to smartly design and effectively construct these buildings to ensure energy performance as per design expectations. However, the research tells a different tale: energy-efficient buildings have performance issues. Among several reasons behind the energy performance gap, occupant behavior is critical. The occupant behavior is dynamic and changes over time under formal and informal influences, but the traditional energy simulation programs assume it as static throughout the occupancy. Effective behavioral interventions can lead to optimized energy use. To find out the energy-saving potential based on simulated modified behavior, this study gathers primary building and occupant data from three energy-efficient office buildings in major cities of Pakistan and categorizes t... [more]

Street lighting plays a crucial role in a city’s night landscape and in urban traffic management, influencing users’ comfort and safety. To contain costs of public street lighting systems and to avoid energy waste, illuminance levels on road surfaces must be adequate to fit actual traffic volumes, as prescribed by regulations. This is true not only for motorized roads but also for sidewalks, paths, and pedestrian areas. Regulations in force establish a relationship between road traffic volumes and minimum illuminance levels through the lighting classes selection procedure. Lighting classes selection is based on various para meters among which traffic volume is the most difficult to evaluate because traffic volumes are generally estimated or measured by a traffic observation campaign. In this paper, an alternative method for classes association which is based on a space syntax approach, is described. The method was applied to the case study town of Pontedera (Italy) for the analysis of... [more]

This paper presents a comprehensive analysis of the effect of the converter synchronizing methods on the contribution that Battery Energy Storage Systems (BESSs) can provide for the support of the inertial response of a power system. Solutions based on phase-locked loop (PLL) synchronization and virtual synchronous machine (VSM) synchronization without PLL are described and then compared by using time-domain simulations for an isolated microgrid (MG) case study. The simulation results showed that inertial response can be provided both with and without the use of a PLL. However, the behavior in the first moments of the inertia response differed. For the PLL-based solutions, the transient response was dominated by the low-level current controllers, which imposed fast under-damped oscillations, while the VSM systems presented a slower response resulting in a higher amount of energy exchanged and therefore a greater contribution to the support of the system inertial response. Moreover, it... [more]