As the onshore wind farm technology matures, offshore wind energy has attracted increasing attention. Zhejiang has coastal areas with massive potential for wind resources because of its geographical location. Therefore, understanding the wind resources in these areas can lay a foundation for future development and utilization. On this basis, this study used the measured wind field data of a wind farm along the coast of Zhejiang from March 2014 to February 2015 and from March 2016 to February 2018 to investigate and compare the characteristics of wind energy resources, including average wind speed, Weibull shape and scale factors, wind direction variation, and wind energy density. Then, the capacity coefficient of a wind turbine predicted using the wind farm data was compared with the actual capacity coefficients of two wind turbines in the wind farm in 2019. Results revealed the following observations: The overall variations in the evaluation indicators followed clear patterns over the... [more]

Increasingly, the exploitation of buildings involves the need for comprehensive management of all systems operating within it, their continuous monitoring, both for the safety of users and to mainly optimize the operating parameters of systems that are largely dependent on each other, interact with each other. This is mainly associated with the need for the most energy-efficient management of energy consumption, which has the largest share of operating costs. The main cost for the facilities is the cooling aspect, which is significant, and for this reason, it is necessary to analyze the possibility of its minimization. One of the possible systems to consider in order to reduce the consumption of cooling energy in the facility is the application of free-cooling technology, which is based on the use of the natural cooling capacity of the outside air for cooling rooms with high heat gains. The application of the free cooling system for facilities with a relatively stable cooling load, wit... [more]

The greenhouse gas emissions from the transportation sector are the primary cause of climate change. As a result, many studies have developed new powertrains with reduced CO2 emissions for the automotive industry. The gas turbine cycle coupled to an alternator is an autonomy booster for series hybrid electric vehicles. Many gas turbine configurations are proposed in the literature to obtain the highest cycle efficiency. This paper suggests a new architecture offering higher efficiency than all the previous cycles. The two-step methodology consists at first of a sensibility analysis using VBA and Refprop to determine the optimal operating conditions in terms of higher efficiency. The selected cycle consists of two compression stages with an intercooler, a combustion chamber, a cooled hot pressure turbine, an uncooled low-pressure turbine, and a recuperator. The efficiency of this design reaches 51.39%, which approximately matches the designs compared in the literature, but is more compa... [more]

It is highly critical that renewable energy-based power generation units provide continuous and high-quality electricity. This requirement is even more pronounced in standalone wind−diesel systems where the wind power is not always constant or available. Moreover, it is desired that the extracted power be maximized in such a way that less fuel is consumed from the diesel engine. This paper proposes a novel method to design decentralized model-predictive controllers to control the frequency and power of a single standalone generation system, which consists of a wind turbine subsystem mechanically coupled with a diesel engine generator subsystem. Two decentralized model-predictive controllers are designed to regulate the frequency and active power, while the mechanical coupling between the two subsystems is considered, and no communication links exist between the two controllers. Simulation results show that the proposed decentralized controllers outperform the benchmark decentralized li... [more]

In the present study analysis of co-firing microwave (MW) pre-treated biomass pellets of different origins (wood and wheat straw), with raw pellets (wood, straw, and peat), to control and improve thermochemical conversion of biomass blends and achieve a sustainable use of local energy resources in energy production has been carried out. Effects of MW pre-treatment regimes and composition of blends were studied experimentally using measurements of the weight loss of blends, the yield of volatiles, flame temperature, total heat output from the device, and composition of products. It was found that co-firing MW pre-treated and raw biomass pellets promotes synergistic interaction between components of blends by increasing mass loss rate, the intensity of which depends on the proximate composition of pellets, MW pre-treatment regime and mass fraction of pre-treated pellets in the blend. The most effective synergistic interaction was found when co-firing pre-treated straw or wood pellets wit... [more]

The publication presents the results of research on soil temperature distribution at a depth of 0.25−3 m in three measurement locations. Two boreholes were located in Białystok in the temperate climatic zone and one measuring well was installed in Belmez in the subtropical climatic zone. Measurements were made in homogeneous soil layers in sand (Białystok) and in clay (Białystok and Belmez). Based on the results of the measurements, a simplified model of temperature distributions as a function of depth and the number of days in a year was developed. The presented model can be used as a boundary condition to determine heat losses of district heating pipes located in the ground and to estimate the thermal efficiency of horizontal heat exchangers in very low-temperature geothermal energy applications.

Effective governance of air pollution requires precise identification of its influencing factors. Most existing studies attempt to identify the socioeconomic factors but lack consideration of multidimensional heterogeneous characteristics. This paper fills this long-ignored research gap by differentiating governance regions with regard to multidimensional heterogeneity characteristics. Decision tree recursive analysis combined with a spatial autoregressive model is used to identify governance factors in China. Empirical results show several interesting findings. First, geographic location, administrative level, economic zones and regional planning are the main heterogeneous features of accurate air pollution governance in Chinese cities. Second, significant influencing factors of air pollution in different delineated regions are identified, especially significant differences between coastal and non-coastal cities. Third, the trends of heterogeneity in urban air governance in China are... [more]

The manuscript analyses the management of low and ultra-low-temperature district heating systems (DHS) coupled with centralised and decentralised heat pumps. Operative conditions are defined in order to satisfy the heating needs without overloading the electric grid. The results are achieved by dynamic simulations, based on a real DHS located in southern Switzerland. At the building level, the heating needs are estimated considering real data and simultaneous energy simulations. Two DHS configurations, alternatives to the existing one, are simulated and suitable parameters for the management of the DHS are selected. The global performance of the two DHS is evaluated by KPIs also including the flexibility and the impact on the electric peak due to heat pumps. The achieved results are discussed providing suggestions for the stakeholders involved in DHS management for an optimal matching of the electric grid and thermal networks towards a reduction of the peak power. The rule-based contro... [more]

A fully wicked ground source heat pipe (GSHP) is numerically employed and simulated to transfer thermal energy from the subsurface to ground surface pavements to reduce the environmental temperature fluctuations in the pavement, thereby reducing thermal stresses and increasing pavement life. The GSHP can also reduce or eliminate snow and ice buildup on pavement surfaces. Each single GSHP was modeled in a two-dimensional axisymmetric cross-section using COMSOL software, which employs a finite element method. The modeled GSHP consisted of two parts: a disk shape buried below the pavement surface, connected to a cylindrical part embedded in a vertical underground borehole. The GSHP finite element model was validated against published experimental heat pipe data. The simulation results demonstrated that the thermal behavior of the heat pipe system during the cold season could reduce the temperature fluctuations on the pavement surface in six various climate zones. The addition of insulatio... [more]

Codes and methods are subjected to a continuous update process for answering the regulatory requirements concerning the long-term operation of existing reactors and new concept deployment. In this continuous improvement process, new generation codes are developed for supporting industrial applications and the long-term strategy. In this paper, attention is devoted to selecting codes under development in France for lattice and core steady-state and transient calculations. These codes, APOLLO3® and CATHARE3, have been selected for carrying out the activities of the H2020 CAMIVVER Project oriented to the 3D-multiphysics couplings improvements. Multiscale and multiphysics solutions are key topics to keep competitiveness and answer to newer industrial needs in plant operations, licensing, and safe operating envelope requirements. The paper presents an overview of the activities performed by Framatome to support the definition of benchmarks exercises proposed in the CAMIVVER Project. Small c... [more]

In the rapid promotion of China’s electricity spot market, a large number of electricity retailers and large consumers participate in power trading, of which medium- and long-term power trading accounts for a large proportion. In the electricity spot market, the previous medium- and long-term transactions need to be closely combined with the current spot market transaction settlement rules. This paper analyzes the trading strategy of large retailers in the power market. In order to effectively reduce the total electricity cost, it is necessary to optimize the medium- and long-term transactions based on three aspects: electricity quantity and benchmark price decisions of medium- and long-term contracts, the daily electricity decomposition method in the day-ahead (DA) market, and the daily load curve decomposition strategy. According to load history characteristics that are extracted by the X12 method, daily electricity is decomposed from the medium- and long-term electricity quantity in... [more]

New technologies are being developed to elaborate cutting-edge electrical jet engines to replace classical constructions. These new concepts consider the possibility of using electrical machines both as starters and generators, as well as suspension systems for the turbine shafts of aircraft engines. The paper will present mathematical analysis regarding active magnetic bearing (AMB) implementation for rotor−shaft support. This technology allows the elimination of friction forces between cooperating kinematic pairs (stator and rotor), reduces the adverse effects of classic bearings, and increases operating speed range and an operational susceptibility. The mathematical and numerical analysis of active magnetic suspension systems are presented. Next, a comparison of the theoretical studies using Comsol Multiphysics software and its experimental verification are described. A discussion regarding the mathematical analysis and experimental effects is also provided. The conclusion summarize... [more]

The modelling of Linear Fresnel Collectors (LFCs) is crucial in order to predict accurate performance for annual yields and to define proper commands to design the suitable controller. The ISO 9806 modelling, applied to thermal collectors, presents some gaps especially with concentration collectors including LFCs notably due to the factorisation of the incidence angle modifiers and the fact that they are considered symmetric around the south meridian. The present work details the use of two alternative modellings methodologies based on recorded experimental data on the solar system installed at the Cyprus Institute, in the outskirts of Nicosia, Cyprus. The first modelling is the RealTrackEff, which is an improved ISO9806 modelling, and the second is constructed using the CARNOT blockset in MATLAB/Simulink. Both models include all the elements of the heat transfer fluid loop, i.e., mineral oil, with a tank and a heat-exchanger. First, the open loop’s studies demonstrated that the root m... [more]

This study presents an application for a series VSC (voltage source converter) in distribution grids for power flow management. Series devices have been widely studied for FACTS (flexible AC transmission systems), however, more recently these devices have gained increased interest in applications for loading balance in medium voltage distribution grids. As the number of distributed generation (DG) units increases, increasing the capacity and reliability of distribution grids while maximizing the benefits of installed DGs and loading behavior is an ever more important task. In this paper, we describe a test system and control proposals for a practical application of series converters interconnecting two distribution feeders at 13.8 kV under load variation disturbances. This approach provides solutions when installed at the end of distribution lines by interconnecting two feeders, resulting in capacity increases in the feeders without needing grid reconfigurations using a small-rated ser... [more]

Solid oxide fuel cells (SOFCs) have complex characteristics, including a long time delay, strong thermoelectrical coupling, and multiple constraints. This leads to multiple control objectives, such as efficiently controlling the power output of the stack and considering the temperature constraints of multiple high-temperature components. Dealing with multiple objectives at the same time brings challenges to the design of SOFC system control. Based on the verified high-precision system model and aiming to achieve fast response, high efficiency, and thermal management, this paper first designs a generalized predictive controller (GPC) to realize the global optimization of the system. Then, through the actual test of the individual reformer, the reformer characteristics are analyzed, the standby controller to control the reformer temperature is designed, and the thermoelectric cooperative controller is constricted with the GPC. The results show that while fast power tracking, high efficie... [more]

The anticipated electrification of the transport sector may lead to significant increase in the future peak electricity demand, resulting in potential violations of network constraints. As a result, a considerable amount of network reinforcement may be required in order to ensure that the expected additional demand from electric vehicles that are to be connected will be safely accommodated. In this paper we present the Backwards Induction Framework (BIF), which we use for identifying the optimal investment decisions, for calculating the option value of smart charging of EV and the cost of stranded assets; these concepts are crystallized through illustrative case studies. Sensitivity analyses depict how the option value of smart charging and the optimal solution are affected by key factors such as the social cost associated with not accommodating the full EV capacity, the flexibility of smart charging, and the scenario probabilities. Moreover, the BIF is compared with the Stochastic Opt... [more]

The global climate, ecological, and energy crisis has increased the interest in the green economy (GE) concept that aims to resolve environmental problems while promoting economic growth, social stabilization, and creating favorable conditions for sustainable economic growth. The implementation of GE solutions requires an assessment system for evaluating the extent to which business operations are consistent with GE principles. In this study, the environmental, economic, and social dimensions of the quality of life were identified, and agricultural factors were considered to determine the progress in the implementation of GE principles. The correlation between the success of GE implementation and the utilization of environmental funding provided by the Common Agricultural Policy (CAP) was analyzed. A composite GE index composed of 19 variables was developed for this purpose with the use of Hellwig’s taxonomic measure of development. The strength of the correlation between GE implementa... [more]

Industrial energy accounts for a large percentage of global consumption and, thus, it is a target for decarbonization by renewable and in particular solar energy adoption. Low uncertainty simulation tools can reduce the financial risk of solar projects, fostering the transition to a sustainable energy system. Several simulation tools are readily available to developers; differences exist in the format of input data and complexity of physical and numerical models. These tools can provide a variety of results from technical to financial and sensitivity analysis, often producing significant differences in yield assessment and uncertainty levels. IEA SHC Task 64/SolarPACES Task IV—Subtask C aims to address the lack of standard simulation tools for Solar Heating of Industrial Processes (SHIP) plants. This article describes the collaborative work developed by the researchers participating in the task. The identification and classification of several currently available simulation tools are p... [more]

This paper presents a switched inductor (SI) DC−DC boost regulator designed for thermoelectric generator (TEG) applications. To boost and regulate the output voltage, two feedback loops are implemented which control the duty cycle of the SI clock. The first loop consists of a pulse skip modulation (PSM) controller that compares the load voltage and reference voltage. Based on the comparison output, the PSM will either pass or bypass the modulated pulse width signal generated from the second loop. The second loop replaces the conventional circuit design of the pulse width modulation (PWM) with a voltage-to-time converter (VTC). The VTC converts the difference between load and supply voltage to time delay resulting in a modulated pulse width. This work is the first to report on utilizing VTC circuit in the SI boost regulator. The proposed SI boost regulator is designed using 65 nm CMOS technology which converts the TEG voltage of 50 mV to support dynamic voltage scaling in the range of 0... [more]

In this paper, a new integrated system of solid oxide fuel cell (SOFC)−gas turbine (GT)−steam Rankine cycle (SRC)−exhaust gas boiler (EGB) is presented, in which ammonia is introduced as a promising fuel source to meet shipping decarbonization targets. For this purpose, an SOFC is presented as the main power-generation source for a specific marine propulsion plant; the GT and SRC provide auxiliary power for machinery and accommodation lighting, and steam from the waste heat boiler is used for heating seafarer accommodation. The combined system minimizes waste heat and converts it into useful work and power. Energy and exergy analyses are performed based on the first and second laws of thermodynamics. A parametric study of the effects of the variation in the SOFC current density, fuel utilization factor, superheat temperature, and SRC evaporation pressure is conducted to define the optimal operating parameters for the proposed system. In the present study, the energy and exergy efficien... [more]

This paper presents the design optimization of a heat exchanger for a free-piston Stirling engine (FPSE) through an improved quasi-steady flow (iQSF) model and a central composite design. To optimize the tubular hot heat exchanger (HHX) design, a design set of central composite designs for the design factors of the HHX was constructed and the brake power and efficiency were predicted through the iQSF model. The iQSF model is improved because it adds various heat and power losses based on the QSF model and applies a heat transfer model that simulates the oscillating flow condition of an actual Stirling engine. Based on experimental results from the RE-1000, an FPSE developed by Sunpower, the iQSF model significantly improves the prediction error of the indicated power from 66.9 to 24.9% compared to the existing QSF model. For design optimization of the HHX, the inner diameter and the number of tubes with the highest brake power and efficiency were determined using a regression model, an... [more]

The utilization of renewable energy sources aids in the economic development of a country. Among the various renewable energy sources, wind energy is more effective for electricity production. The doubly fed induction generator is an extensively known wind turbine generator for its partially rated power converters and dynamic performance. The doubly fed induction generator assists the wind turbine to function with a wide speed range. Hence, the steady-state performance analysis of a doubly fed induction generator helps enable it to operate efficiently at a specific wind turbine speed. In this paper, a 2 MW variable speed pitch regulated doubly fed induction generator with a speed range of 900—2000 rpm was opted for steady-state analysis. This was followed by the design and modelling of a doubly fed induction generator in Matlab/Simulink environment, and the analyses were performed using mathematical equations computed via Matlab coding. The steady-state magnitudes were calculated with... [more]

The paper presents a novel method for non-intrusive appliances identification. It can be used for energy load disaggregation in a smart grid. The approach identifies changes in the state of the particular appliance by measuring and processing the common supply current signal. Analysis of the instantaneous changes in the aggregated current on the output of the analyzed circuit in the power network is exploited here. The signal is processed using the time alignment of the current and voltage signals samples represented in the array form. The scheme includes filtering, event detection and identification, which is performed by comparing parameters of the detected event against previously determined signatures of monitored appliances. The analysis is performed in the time domain; therefore (unlike other existing methods), the information contained in the original signal is not lost. The approach was tested in the laboratory designed specifically for this purpose. All tests have been conduct... [more]

The need to significantly reduce emissions from the steelmaking sector requires effective and ready-to-use technical solutions. With this aim, different decarbonization strategies have been investigated by both researchers and practitioners. To this concern, the most promising pathway is represented by the replacement of natural gas with pure hydrogen in the direct reduced iron (DRI) production process to feed an electric arc furnace (EAF). This solution allows to significantly reduce direct emissions of carbon dioxide from the DRI process but requires a significant amount of electricity to power electrolyzers adopted to produce hydrogen. The adoption of renewable electricity sources (green hydrogen) would reduce emissions by 95−100% compared to the blast furnace−basic oxygen furnace (BF−BOF) route. In this work, an analytical model for the identification of the minimum emission configuration of a green energy−steel system consisting of a secondary route supported by a DRI production p... [more]

Battery technology is crucial in the transition towards electric mobility. Lithium-ion batteries are conquering the market but are facing fire safety risks that might threaten further applications. In this study, we address the problem and potential solutions for traction batteries in the European Union area. We do so by taking a unique socio-technical system perspective. Therefore, a novel, mixed-method approach is applied, combining literature review; stakeholder interviews; Failure Mode, Mechanisms, and Event Analysis (FMMEA); and rapid prototyping. Our findings confirm that fire safety is an upcoming concern. Still, most stakeholders lack a full understanding of the problem. Improving safety is a shared responsibility among supply chain and societal stakeholders. For automotive applications, voluntary standard-setting on safety risks is an appropriate tool to improve fire safety, whereas for niche applications, a top-down approach setting regulations seems more suited. For both gro... [more]