Solar energy is a potential source for a thermal power generation system. A direct vapor generation solar organic Rankine cycle system using phase change material storage was analyzed in the present study. The overall system consisted of an arrangement of evacuated flat plate collectors, a phase-change-material-based thermal storage tank, a turbine, a water-cooled condenser, and an organic fluid pump. The MATLAB programming environment was used to develop the thermodynamic model of the whole system. The thermal storage tank was modeled using the finite difference method and the results were validated against experimental work carried out in the past. The hourly weather data of Karachi, Pakistan, was used to carry out the dynamic simulation of the system on a weekly, monthly, and annual basis. The impact of phase change material storage on the enhancement of the overall system performance during the charging and discharging modes was also evaluated. The annual organic Rankine cycle effi... [more]

In this paper, the interaction between the energy storage (ES) power distribution and system efficiency enhancement is researched based on the energy stored quasi-Z-source inverter. The corresponding current counteraction, stress reduction, power loss profile, and efficiency enhancement around the embedded energy storage units are studied in details. Firstly, the current counteraction effect on the device current is presented with the embedded ES source. The corresponding reduction in the device current stress is revealed. Then, the detailed device power loss expressions with current redistribution in the impedance network are explored mathematically. A quasi-inverted-trapezoidal power loss profile is found with the embedded source power distribution. To further increase the overall system efficiency, an optimal energy efficiency tracking strategy is proposed for the ES-qZSI (energy-stored quasi-Z-source inverter) based on the power distribution control. Both the simulation and the exp... [more]

Simulation of the seismic wave propagation in natural gas hydrate (NGH) is of great importance. To finely portray the propagation of seismic wave in NGH, attenuation properties of the earth’s medium which causes reduced amplitude and dispersion need to be considered. The traditional viscoacoustic wave equations described by integer-order derivatives can only nearly describe the seismic attenuation. Differently, the fractional time derivative seismic wave-equation, which was rigorously derived from the Kjartansson’s constant-Q model, could be used to accurately describe the attenuation behavior in realistic media. We propose a new fractional finite-difference method, which is more accurate and faster with the short memory length. Numerical experiments are performed to show the feasibility of the proposed simulation scheme for NGH, which will be useful for next stage of seismic imaging of NGH.

Integrating photovoltaic applications within urban environments creates the need for more compact and efficient power electronics that can guarantee long lifetimes. The upcoming wide-bandgap semiconductor devices show great promise in providing the first two properties, but their packaging requires further testing in order to optimize their reliability. This paper demonstrates one iteration of the design for reliability methodology used in order to compare the generated thermo-mechanical stress in the die attach and the bond wires of a GaN and SiC MOSFET. An electro-thermal model of a photovoltaic string inverter is used in order to translate a cloudy and a clear one-hour mission profile from Arizona into a junction losses profile. Subsequently, the finite element method models of both devices are constructed through reverse engineering in order to analyze the plastic energy. The results show that the plastic energy in the die attach caused by a cloudy mission-profile is much higher th... [more]

Shale gas reservoirs are typically developed by multistage, propped hydraulic fractures. The induced fractures have a complex geometry and can be represented by a high permeability region near each fracture, also called stimulated region. In this paper, a new integrative analytical solution coupled with gas adsorption, non-Darcy flow effect is derived for shale gas reservoirs. The modified pseudo-pressure and pseudo-time are defined to linearize the nonlinear partial differential equations (PDEs) and thus the governing PDEs are transformed into ordinary differential equations (ODEs) by integration, instead of the Laplace transform. The rate vs. pseudo-time solution in real-time space can be obtained, instead of using the numerical inversion for Laplace transform. The analytical model is validated by comparison with the numerical model. According to the fitting results, the calculation accuracy of analytic solution is almost 99%. Besides the computational convenience, another advantage... [more]

The growing risk of climate change caused by the emission of greenhouse gases poses new challenges to contemporary countries. The development of economies is usually related to increasing levels of greenhouse gas emissions. Therefore, the question arises whether it is possible to achieve sustainable economic and financial development and simultaneously reduce greenhouse gas emissions. This paper assumes it is possible if energy efficiency is increased. The aim of the paper is to show the link between energy efficiency and sustainable economic and financial development in Organisation for Economic Co-operation and Development (OECD) countries for the period 2000−2018 by using data envelopment analysis (DEA) and regression analysis. The results show a slight upward trend of total factor energy efficiency (TFEE) in OECD countries for the analysed period; however, there is a difference in TFEE levels. Developed OECD countries have higher TFEE levels than developing OECD countries. The link... [more]

This research represents a conceptual shift in the process of introducing flexibility into power system frequency stability-related protection. The existing underfrequency load shedding (UFLS) solution, although robust and fast, has often proved to be incapable of adjusting to different operating conditions. It triggers upon detection of frequency threshold violations, and functions by interrupting the electricity supply to a certain number of consumers, both of which values are decided upon beforehand. Consequently, it often does not comply with its main purpose, i.e., bringing frequency decay to a halt. Instead, the power imbalance is often reversed, resulting in equally undesirable frequency overshoots. Researchers have sought a solution to this shortcoming either by increasing the amount of available information (by means of wide-area communication) or through complex changes to all involved protection relays. In this research, we retain the existing concept of UFLS that performs s... [more]

Loop distribution systems are increasingly used for reasons such as increased distributed generation (DG) and increased demand for a reliable and high-quality power supply. Because the loop distribution system involves bidirectional power flow, the method for protection of the radial distribution system cannot be applied. Therefore, a protection method is proposed herein for loop distribution systems. In this study, the existence of DG is also considered. According to the proposed method, the fault point is estimated on the basis of the equivalent circuit of the distribution system. Then, the fault section is determined and separated from the distribution system. The separation of DG is determined depending on whether the frequency and voltage are maintained within the steady state ranges. The proposed method is modelled and verified using the Electromagnetic Transients Program. Simulations according to the fault location are performed and analyzed. The results show that the method acc... [more]

The transition towards renewable energy sources and “green” technologies for energy generation and storage is expected to mitigate the climate emergency in the coming years [...]

Sustainability is among the most important directions in global development. The challenge today is to reconcile the fastest possible economic growth and the pursuit of prosperity with concern for the environment. One of the important problems of modern economies and societies is to reduce overall consumption and implement new patterns of sustainable consumption and production. The main aim of this article was to analyze consumer preferences in terms of purchasing personalized production offered by implementing the concept of Industry 4.0 and ensuring sustainable consumption and production (SCP). Based on the analysis of the literature and the results of our own research, an attempt was made to estimate the impact of personalized production offered by the Industry 4.0 concept on SCP and thus the sustainable development of the economy. This article presents the results of a survey conducted on a selected group of consumers, focusing on learning about expectations, consumer preferences f... [more]

In some power networks, components of frequency less than the frequency of the fundamental voltage harmonic called subharmonics or subsynchronous interharmonics occur. In this paper, the effect of voltage subharmonics on currents, power losses, speed fluctuations and electromagnetic torque is examined. The results of numerical computations using the finite element method for an induction cage motor of rated power of 5.6 MW and four motors of rated power of 200 kW with different numbers of poles are presented. An extraordinary harmful effect on high-power induction motors is demonstrated. Among other effects, voltage subharmonics cause significant torque pulsations whose frequencies may correspond to the elastic-mode natural frequency. Possible resonance can result in excessive torsional vibration and the destruction of a power train.

Energy usage in buildings is coming increasingly under the spotlight as carbon policy focus shifts towards the utilization of thermal energy. In the UK, heating and hot water accounts for around 40% of energy consumption and 20% of greenhouse gas emissions. Heating is typically produced onsite, making widescale carbon or energetic improvements challenging. District heating networks (DHNs) can offer significant carbon reduction for many users but can only be implemented if the end user buildings have good thermal energy efficiency. This greatly limits the ability to implement advancing 4th and 5th generation DHNs, which are the most advanced systems available. We elucidate the current state of thermal efficiency in buildings in the UK and provide recommendations for necessary building requirements and modifications in order to accommodate 4th and 5th generation district heating. We conclude that key sectors must be addressed including creating a skilled workforce, producing relevant met... [more]

Predictive maintenance strategies in power transformers aim to assess the risk through the calculation and monitoring of the health index of the power transformers. The parameter most used in predictive maintenance and to calculate the health index of power transformers is the dissolved gas analysis (DGA). The current tendency is the use of online DGA monitoring equipment while continuing to perform analyses in the laboratory. Although the DGA is well known, there is a lack of published experimental data beyond that in the guides. This study used the nearest-rank method for obtaining the typical gas concentration values and the typical rates of gas increase from a transformer population to establish the optimal sampling interval and alarm thresholds of the continuous monitoring devices for each power transformer. The percentiles calculated by the nearest-rank method were within the ranges of the percentiles obtained using the R software, so this simple method was validated for this stu... [more]

Vibrations occurring during road transport can vary in a wide spectrum and they can lead to losses in quality of transported materials. However, the vibrations are definitely different than the loads experienced by pellet samples in the tester used for durability tests according to the standard ISO 17831-1. pThe aim of the study was to evaluate the durability of wood biomass pellets available for sale in large-area stores, in terms of loads occurring in transport. The durability of the ellets was tested by subjecting them to vertical and horizontal vibrations similar to those occurring during local transport of this type of fuel for the needs of households. Durability tests were also carried out in accordance with ISO 17831-1. The results were analyzed statistically. Among other, it was found that the vibration time impact on the tested pellet durability was significantly lower in case of horizontal vibrations than in vertical. Moreover, pellets with a diameter of 8 mm showed lower dur... [more]

The size of the fuel cell and battery of a Fuel Cell Hybrid Electric Vehicle (FCHEV) will heavily affect the overall performance of the vehicle, its fuel economy, driveability, and the rates of fuel cell degradation observed. An undersized fuel cell may experience accelerated ageing of the fuel cell membrane and catalyst due to excessive heat and transient loading. This work describes a multi-objective design exploration exercise of fuel cell size and battery capacity comparing hydrogen fuel consumption, fuel cell lifetime, vehicle mass and running cost. For each system design considered, an individually optimised Energy Management Strategy (EMS) has been generated using Stochastic Dynamic Programming (SDP) in order to prevent bias to the results due to the control strategy. It has been found that the objectives of fuel efficiency, lifetime and running cost are largely complimentary, but degradation and running costs are much more sensitive to design changes than fuel efficiency and th... [more]

L. (JCL) commercial plantations in Mexico, one of the most important JCL origin centers, have failed due to a variety of biological, political and technical factors affecting their productivity. This study explores feasible sites of JCL cultivation as a potential source for biodiesel production in Mexico, given agroclimatic and agroecological considerations. We propose a GIS-based approach for estimating suitable and available lands to grow JCL by integrating an Analytical Hierarchy Process (AHP) in the ArcGIS software. Spatial analysis combined multiple data, different evaluation criteria, three land availability classes (high, medium and low potential) and took into account ecological, ethical, and political restrictions, and considering two scenarios with different restriction levels. Suitability and availability maps were generated using agroclimatic information (climatic, land use/soil, and climate change and extreme weather events risk) together with other socioeconomic factors.... [more]

Article [...]

Industrial energy flexibility enables companies to optimize their energy-associated production costs and support the energy transition towards renewable energy sources. The first step towards achieving energy flexible operation in a production facility is to identify and characterize the energy flexibility measures available in the industrial systems that comprise it. These industrial systems are both the manufacturing systems that directly execute the production tasks and the systems performing supporting tasks or tasks necessary for the operation of these manufacturing systems. Energy flexibility measures are conscious and quantifiable actions to carry out a defined change of operative state in an industrial system. This work proposes a methodology to identify and characterize the available energy flexibility measures in industrial systems regardless of the task they perform in the facility. This methodology is the basis of energy flexibility-oriented industrial energy audits, in jux... [more]

Metal cloth seals have been used increasingly in gas turbines due to their flexibility and superior leakage performance. Leakage performance of a metal cloth seal depends on operating conditions, slot and geometric dimensions. These parameters need to be investigated for the best leakage performance. In this study, pressure drop and critical geometric parameters of typical cloth seal form are investigated with an experimental setup. Slot depth, cloth width, sealing gap, shim thickness, surface roughness, pressure drop, offset and mismatch are selected parameters for the screening experiments. Sixteen experiments were conducted following a two-level Resolution IV fractional factorial experiment design for eight parameters. The results indicated that strong parameters for the leakage performance are pressure drop, cloth width, slot depth and offset. Leakage rate is increased with an increase in slot depth, gap, shim thickness, pressure drop and mismatch. During screening experiments, the... [more]

Facing the reinforced emission regulations and moving toward a clean powertrain, hydrogen has become one of the alternative fuels for the internal combustion engine. In this study, the prediction methodology of hydrogen yield by on-board fuel reforming under a diesel engine is introduced. An engine dynamometer test was performed, resulting in reduced particulate matter (PM) and NOx emission with an on-board reformer. Based on test results, the reformed gas production rate from the on-board reformer was trained and predicted using an artificial neural network with a backpropagation process at various operating conditions. Additional test points were used to verify predicted results, and sensitivity analysis was performed to obtain dominant parameters. As a result, the temperature at the reformer outlet and oxygen concentration is the most dominant parameters to predict reformed gas owing to auto-thermal reforming driven by partial oxidation reforming process, dominantly.

Most of the small modular reactors (SMRs) under development worldwide present the same components: an integral reactor vessel with a low-positioned core as the heat source and a high-positioned steam generator as the heat sink. Moreover, some SMRs are being designed to be driven by natural circulation during normal power generation. This work focused on such designs and on their performance, considering the changes generated by the geometric and hydraulic parameters of the system. Numerical simulations using mass, momentum, and energy equations that considered buoyancy forces were performed to determine the effects of various geometric and hydraulic parameters, such as diameters and flow resistances, on the reactor’s performance. It was found that nonuniform diameters promote velocity changes that affect the natural circulation flow rate. Moreover, the reactor’s temperature distribution depends on the steam generator tube pitch. Therefore, the hydraulic diameters of the reactor’s coola... [more]

The research work hereby presented, emerges from the urge to answer the well-known question of how the uncertainty of intermittent renewable sources affects the performance of a microgrid and how could we deal with it. More specifically, we want to evaluate what could be the impact in performance of a microgrid that is intended to serve a smart-building (powered by photovoltaic panels and with battery energy storage), when the uncertainty of the photovoltaic-production forecasts is considered in the energy management process through the use of quantile forecasts. For this, several objectives (or services) are targeted based in a two-step (double-objective) energy management framework, which combines optimization-based and rule-based algorithms. The performance is evaluated based on some particular services, namely: energy cost, carbon footprint, grid peak power, and grid commitment; with the latter being a novel service proposed in the domain of microgrids. Simulations are performed wh... [more]

When the load of Circulating Fluidized Bed (CFB) boiler changes dynamically, the accumulation and consumption of residual char causes a large inertia and hysteresis in the boiler combustion system. Therefore, accurate estimation of the residual char in the boiler is of great significance to the control system and improve the combustion efficiency. Based on the Computational Particles Fluid Dynamics (CPFD) method, a numerical simulation of the variable load process of CFB boiler was carried out, and the dynamic changes of the residual char inventory were analyzed by combining the coal feed, ash discharge, and furnace calorific value. The results showed that after CFB boiler reached stable operation, the residual char fluctuated from 11,000 kg to 16,000 kg, accounting for about 3.7% of the total bed material, and the residual char was in a dynamic balance. During the load-up phase, the average residual char was 17,500 kg, and during the load-down phase, the average residual char was 15,0... [more]

A passive regulation system for the water content has been developed and evaluated for a proton exchange membrane fuel cell. It is of particular relevance for micro-fuel cells, whose volume, weight and extra-consumption of fuel and power for subsidiary components must be kept to a minimum. This solution consists of a self-regulating humidity system implemented at the anode chamber that allows free water exchange with the environment through the surface of a gas-tight membrane. The micro-fuel cell, which is designed according to the patent WO2015025070A1, has been assembled and operated under completely passive conditions. The behavior of the anode humidity regulation system has been analyzed externally and in situ. The external part of the anode, where the humidity exchange with the environment takes place, has been isolated in a closed chamber and a hygrometer has been used to register the relative humidity in the zone near to the water exchange film. The results obtained from the ope... [more]

The monitoring of rock volume where offshore exploitation activities take place is crucial to assess the corresponding seismic hazard. Fluid injection/extraction operations generate a pore fluid pressure perturbation into the volume hosting the reservoir which, in turn, may trigger new failures and induce changes in the elastic properties of rocks. Our purpose is to evaluate the feasibility of reconstructing pore pressure perturbation diffusion in the host medium by imaging the 4D velocity changes using active seismic. We simulated repeated active offshore surveys and imaged the target volume. We constructed the velocity model perturbed by the fluid injection using physical modeling and evaluated under which conditions the repeated surveys could image the velocity changes. We found that the induced pressure perturbation causes seismic velocity variations ranging between 2−5% and 15−20%, depending on the different injection conditions and medium properties. So, in most cases, time-lapse... [more]