Thermal comfort (heating, ventilation and air conditioning, HVAC) and the energy consumption involved with it can put a strain on the driving range of fully electric vehicles (FEV), especially in certain times of the year as midsummer or winter. In order to reduce the energy consumption of HVAC, improved thermal management and adapted means of energy storage are needed. One part of the solution can be the use of phase change materials (PCM) for storing waste heat. For the specific application, however, a high loading/unloading power rate is required, which is challenging as the PCMs exhibit low heat conductivities. In the presented work, a storage demonstrator system was investigated which is part of an HVAC system of a specific fully electric vehicle. The profile of requirements of the system (power, stored capacity and allowed volume) make a new design of the storage necessary. Two demonstrator units, in which the PCM was combined with aluminum foam, were manufactured and their power... [more]

Since the electricity market liberalisation of the mid-1990s, forecasting energy demand and prices in competitive markets has become of primary importance for energy suppliers, market regulators and policy makers. In this paper, we propose a non-parametric model to obtain point and interval predictions of price and demand. It does not require any parametric assumption on the distribution of the error term or on the functional relationships linking the response variable to covariates. The assumed location−scale model provides a non-parametric estimation of the conditional mean and of the conditional variance by means of a Generalised Additive Model. Interval forecasts, at any given confidence level, are then obtained using a further non-parametric estimation of the innovation’s quantile. Since both the conditional mean and the conditional variance of the response variable are non-linear functions of covariates depending on calendar factors, renewable energy productions and other market... [more]

In this study, the thermal performance of latent heat thermal energy storage system (LHTESS) prototype to be used in a range of thermal systems (e.g., solar water heating systems, space heating/domestic hot water applications) is designed, fabricated, and experimentally investigated. The thermal store comprised a novel horizontally oriented multitube heat exchanger in a rectangular tank (forming the shell) filled with 37.8 kg of phase change material (PCM) RT62HC with water as the working fluid. The assessment of thermal performance during charging (melting) and discharging (solidification) was conducted under controlled several operational conditions comprising the heat transfer fluid (HTF) volume flow rates and inlet temperatures. The experimental investigations reported are focused on evaluating the transient PCM average temperature distribution at different heights within the storage unit, charging/discharging time, instantaneous transient charging/discharging power, and the total... [more]

The in situ hygro-thermal behavior of a wet masonry wall during its drying process is presented in this paper. The considered wall is a part of a basement of a historic building that was subjected to renovation works. The building is located in the City of Łowicz (Poland). The drying process was implemented by applying the thermo-injection method and a novel prototype of the drying device used for this method. The dedicated acquisition system was developed to in situ monitor parameters of the drying process. The air temperature and relative humidity in various locations in the basement, temperatures and moisture contents at several points of the wet wall as well as the electrical parameters of the drying device were registered. Based on variations of the monitored parameters, the hygro-thermal behavior of the wall during drying was studied. After 6 days of drying, the wall temperature in the drying zone was increased to approximately 40−55 °C, while the moisture content was reduced to... [more]

We developed and studied key performance indexes and representations of energy simulation heat fluxes to evaluate the performance of the evaporative cooling process as a passive cooling technique for a commercial building typology. These performance indexes, related to indoor thermal comfort, energy consumption and their interactions with their surrounding environments, contribute to understanding the interactions between the urban climate and building for passive cooling integration. We compare the performance indexes for current and future climates (2080), according to the highest emission scenario A2 of the Special Report on Emission Scenario (SRES). Specific building models were adapted with both green roof and wetted roof techniques. The results show that summer thermal discomfort will increase due to climate change and could become as problematic as winter thermal discomfort in a temperate climate. Thanks to evapotranspiration phenomena, the sensible heat contribution of the buil... [more]

Modern power systems must provide efficient, reliable, and environmentally responsible energy. Recently, the inclusion of Microgrids (MGs) has allowed us to overcome some difficulties and face important challenges in this direction, especially related to the use of alternative energy sources. Increased and probabilistic demand, as well as limited energy supply, pose the need to evaluate the reliability of any distribution system (DS) when MGs are introduced. Here we reviewed and classified the state-of-the-art of reliability assessment (RA) in MGs. Initially, we contextualize RA in distribution systems. Next, each of the MGs subsystems components are introduced and the questions (1) why is it important to evaluate the reliability in Microgrids? (2) how do Microgrids influence the reliability of distribution systems? and (3) how does each of its subsystems influence the reliability of the Microgrids? are addressed. A total of 1395 research studies were published between 2002 and 2020. U... [more]

The growing concern about global climate change extends to different professional sectors. In the building industry, the energy consumption of buildings becomes a factor susceptible to change due to the direct relationship between the outside temperature and the energy needed to cool and heat the internal space. This document aims to estimate the energy consumption of a Minimum Energy Building (MEB) in different scenarios—past, present, and future—in the subtropical climate typical of seaside cities in Southern Spain. The building energy consumption has been predicted using dynamic building energy simulation software tools. Projected climate data were obtained in four time periods (Historical, the 2020s, 2050s, and 2080s), based on four emission scenarios defined by the Intergovernmental Panel on Climate Change (IPCC): B1, B2, A2, A1F1. This methodology has been mathematically complemented to obtain data in closer time frames (2025 and 2030). In addition, different mitigation strategie... [more]

Briquetting is one of the recommended biomass agglomeration processes. The material subjected to briquetting gains valuable functional features related to higher energy density, appropriate moisture content, and increased bulk density. However, the briquettes need high mechanical durability to maintain high quality during transportation, loading, and other logistic steps before they will be delivered to the final consumer and utilized for energy purposes. The mechanical durability depends on many factors, including the particles comminution of the compacted biomass. Therefore, the aim of this study was to analyze the impact of particle comminution on the mechanical durability of wheat straw briquettes. The research was carried out in accordance with the international standard for solid biofuels PN-EN ISO 17831-1:2016-02. The briquettes were produced from three different fractions: 0−2 mm, 2−15 mm, and 15−45 mm. To obtain more data related to the mechanical durability of briquettes, the... [more]

Hydraulic fracturing has transitioned into widespread use over the last few decades. There are a variety of numerical methods available to simulate hydraulic fracturing. However, most current methods require a large number of input parameters, of which the values of some parameters are poorly constrained. This paper proposes a new method of modelling the hydraulically fractured region using void-ratio dependent relation to define the permeability of the fractured region. This approach is computationally efficient and reduces the number of input parameters. By implementing this method with an equivalent continuum representation, uncertainties are reduced arising from heterogeneity and anisotropy of earth materials. The computational efficiency improves modelling performance in stress sensitive zones such as in the vicinity of the injection well or near faults.

In today’s world, distributed generation (DG) is an outstanding solution to tackle the challenges in power grids such as the power loss of the system that is intensified by the exponential increase in demand for electricity. Numerous optimization algorithms have been used by several researchers to establish the optimal placement and sizing of DGs to alleviate this power loss of the system. However, in terms of the reduction of active power loss, the performance of these algorithms is weaker. Furthermore, the premature convergence, the precision of the output, and the complexity are a few major drawbacks of these optimization techniques. Thus, this paper proposes the multileader particle swarm optimization (MLPSO) for the determination of the optimal locations and sizes of DGs with the objective of active power loss minimization while surmounting the drawbacks in previous algorithms. A comprehensive performance analysis is carried out utilizing the suggested approach on the standard IEE... [more]

Small sized electric motors providing high specific torque and power are required for many mobile applications. Air gap windings technology allows to create innovative lightweight and high-power electric motors that show low phase inductances. Low inductance leads to a small motor time constant, which enables fast current and torque control, but requires a high switching frequency and short sampling time to keep current ripples and losses in an acceptable range. This paper proposes an optimal torque feedforward control method, minimizing either torque ripples or motor losses, combined with a very robust and computation-efficient modal current feedback control. Compared to well-known control methods based on the Clarke-Park Transformations, the proposed strategy reduces torque ripples and motor losses significantly and offers a very fast implementation on standard microcontrollers with high robustness, e.g., against measurement errors of rotor angle. To verify the accuracy of the propos... [more]

This study concerns the development and testing of three types of Anti-lock Brake Systems (ABS): a standard on-off wheel’s acceleration control; a wheel’s longitudinal slip controller based on a discrete Proportional-Integral-Derivative (PID) control; and a novel type of ABS that involves controlling the wheel’s speed through a discrete PID. This work was developed inside a wider project that will lead to the implementation of stability control systems in a prototype car. For this reason, the typologies of ABS must not require extra sensors compared to those in standard vehicles: Inertial Measurement Unit (IMU) and 4-wheel speed sensors. Furthermore, they must be easily integrated with other controls and electronic components in terms of sampling time and values. The standard ABS seems more appropriate than the others two because it uses only parameters defined by sensors and it has a simple architecture that does not have the problem of computational time. However, in recent years, ca... [more]

During annual operation, a heat pump produces both heating and cooling effects, so it would be of great advantage to store one of the two to be then used when it is necessary. To do this, a seasonal energy storage is necessary. This paper presents results relative to the use of a ground ice thermal energy storage (I-TES) integrated with a reversible heat pump for annual air conditioning. The energy analysis is based on heating and cooling loads for a residential building located in Milan. In particular, the focus is on the most important parameters affecting the performance of both the whole system and the Ice Tank, which is the position and the thickness of the insulation layers and the shape of the ice tank. A biannual simulation of the system allows for a full description of the ice tank behavior during the charging and discharging processes. The main objective of the study is to suggest a first tentative procedure to design the I-TES integrated system with the best energy performan... [more]

As a result of the increased integration of power converter-connected variable speed wind generators (VSWG), which do not provide rotational inertia, concerns about the frequency stability of interconnected power systems permanently arise. If the inertia of a power system is insufficient, wind power plants’ participation in the inertial response should be required. A trendy solution for the frequency stability improvement in low inertia systems is based on utilizing so-called “synthetic” or “virtual” inertia from modern VSWG. This paper presents a control scheme for the virtual inertia response of wind power plants based on the center of inertia (COI) frequency of a control area. The PSS/E user written wind inertial controller based on COI frequency is developed using FORTRAN. The efficiency of the controller is tested and applied to the real interconnected power system of Southeast Europe. The performed simulations show certain conceptual advantages of the proposed controller in compa... [more]

With the emergence of the concept of green manufacturing, more manufacturers have attached importance to energy consumption indicators. The process planning and shop scheduling procedures involved in manufacturing processes can both independently achieve energy savings, however independent optimization approaches limit the optimization space. In order to achieve a better optimization effect, the optimization of energy savings for integrated process planning and scheduling (IPPS) was studied in this paper. A mathematical model for multi-objective optimization of IPPS was established to minimize the total energy consumption, makespan, and peak power of the job shop. A hierarchical multi-strategy genetic algorithm based on non-dominated sorting (NSHMSGA) was proposed to solve the problem. This algorithm was based on the non-dominated sorting genetic algorithm Ⅱ (NSGA-Ⅱ) framework, in which an improved hierarchical coding method is used, containing a variety of genetic operators with diffe... [more]

This study proposes to use gas-fired boilers as peak shaving heat sources in heating substations due to their capability to increase the reliability, flexibility and heat capacity without the need to change the district heating network (DHN). However, the design and operational requirements with different connection modes for this kind of DH system are still not clear. This paper presents a systematic study on this kind of DH system, analyzes the connection modes of series and parallel connections between the gas-fired boilers and the heat exchangers. For each connection mode, we figured out the thermal balances and obtained the design and operational parameters including the supply temperatures of the heat exchangers, gas-fired boilers and their variations under different network temperature levels and the base load ratios (β). Under the series connection mode, the design supply temperature of the heat exchangers has no relation with the design peak shaving flow ratio (ω′); it decreas... [more]

The energy market is gradually changing from centralized trading to peer-to-peer trading due to the tremendous increase in a microgrid with green energy resources. When more generating units are included in the microgrid, the possibilities of more reactive power flows exist in the system that leads to high transmission loss which has to be optimized. The reactive power is one of the essential ancillary services in the microgrid towards preserving the voltage in the transmission and distribution line. The major contribution of the paper is towards managing the ancillary service in the distributed energy network economically and technically. This study aims to estimate and optimize the power loss, reactive power, and price management as well. Towards optimization, the self-balanced differential evolution algorithm (SBDE) is used in this study. A distribution system operator is involved in coordinating the sellers and buyers. The proposed layered microgrid architecture uses the blockchain... [more]

Accompanying the continuous increase in wind power penetration, the power system inertia is reduced, and the system frequency regulation performance deteriorates. Wind turbine generators are required to participate in primary frequency regulation (PFR) to support system frequency. Here, the PFR capability of the widely-used doubly-fed induction generator (DFIG) is evaluated to estimate the participation of the DFIG in system frequency control. The frequency regulation model of the DFIG is established and briefly discussed. The equivalent PFR droop coefficient is then deduced from the model using a small signal increment method to evaluate the DFIG’s PFR capability. Key factors affecting the equivalent droop coefficient are studied, and the droop control is optimized to keep the equivalent droop coefficient in the desired range. The proposed method is verified utilizing a provincial power grid model of China.

This study presents a simplified analysis technique capable of predicting the dynamic behavior of a tripod suction pile subjected to a horizontal load. The first natural frequency of the system, horizontal displacement, and allowable rotation angle at the pile head were set as target physical quantities in accordance with substructure design requirements. In consideration of the physical characteristics of the tripod suction pile, the analysis was extended to the single pile-multi-pile-tripod-tower part to derive the influence factors. A possible displacement response function that could be applied to the intermediate pile range was also proposed. Thereafter, a detailed design was determined using an integrated load analysis, which included a turbine based on the basic design of simplified analysis method. Furthermore, the dynamic behavior of the offshore wind turbine at each installation stage was predicted using a numerical analysis and measured via field tests. The displacement at t... [more]

In this paper, we study the dynamics of a two-degree freedom system consisting of the main body and tuned mass damper with inerter (TMDI). We add the dash-pot with variable damping coefficient to TMDI to study the overall efficiency of the device. We investigate different types of the non-linear characteristic of the dash-pot. We investigate devices in which damping coefficient change according to the relative displacement or the relative velocity between the damped mass and tuned mass damper. We also include in the investigation of different types of control functions. We show the two-parameter diagrams presenting the main body’s maximum amplitude versus the frequency of excitation of the damped body and different control parameter. We show how the application of a non-linear damper lets us control the main system’s oscillation amplitude.

Linear generator utilization in a wave energy converter (WEC) is an attractive alternative to a rotary generator. This paper presents the design of a permanent magnet linear machine (PMLM) for WEC applications in low wave power areas. In this paper, the wave height and vertical speed of Malaysian water is used for the simulation and design. Two design variants are introduced which are tubular PMLM with no spacer (TPMLM-NS) and tubular PMLM with spacer (TPMLM-S). Finite element analysis (FEA) has been conducted to investigate the performance and to refine the main dimensions of the design in terms of split ratio, pitch ratio and tooth width. The FEA results are then validated using an analytical method which is established according to the design’s magnetic field distribution. Based on main dimension refinement, it can be deduced that both the split ratio and the pitch ratio have a significant influence on the airgap flux density and back EMF of the design. The obtained FEA results also... [more]

The fire load of buildings is significantly increased by means of electric cables, usually creating a long combustible base for fire to spread and in this way decreasing the fire safety of buildings. The aim of the study was to evaluate a relationship between the construction of the cables and their fire properties, especially the mass loss influence on other fire properties of cables. Six cables of different core numbers were tested by means of the standard test method EN 50399. Additionally, thermogravimetric analysis and Attenuated Total Reflection—Fourier Transform Infrared analysis were performed on the separate outer sheath, bedding, and core insulations in order to determine the similarity of the materials’ chemical structures. It was found that: (1) the construction of the cable strongly influences the fire behavior due to the creation of a barrier for flame penetration and emission of combustion effluents though inside the closed agglomeration of non-combustible metallic cores... [more]

The measures to reduce the impact of evaporation loss in a natural draft counter-flow wet cooling tower (NDWCT) have important implications for water conservation and emissions reduction. A mathematical model of evaporation loss in the NDWCT was established by using a modified Merkel method. The NDWCTs in the 300 MW and 600 MW power plant were taken as the research objects. Comparing experimental values with calculated values, the relative error was less than 3%. Then, the effect of air parameters on evaporation loss of NDWCT was analyzed. The results showed that, with the increase of dry bulb temperature, the evaporation heat dissipation and the evaporation loss decreased, while the rate of evaporation loss caused by unit temperature difference increased. The ambient temperature increased by 1 °C and the evaporation loss was reduced by nearly 26.65 t/h. When the relative air humidity increased, the evaporation heat dissipation and evaporation loss decreased, and the rate of evaporatio... [more]

Ammonia has strong potentialities as sustainable fuel for energy applications. NH3 is carbon free and can be synthetized from renewable energy sources (RES). In Solid Oxide Fuel Cells, NH3 reacts electrochemically thereby avoiding the production of typical combustion pollutants such as NOx. In this study, an ammonia-fueled solid oxide fuel cells (SOFC) system design is proposed and a thermodynamic model is developed to evaluate its performance. A SOFC short stack was operated with NH3 in a wide range of conditions. Experimental results are implemented in the thermodynamic model. Electrical efficiency of 52.1% based on ammonia Lower Heating Value is calculated at a net power density of 0.36 W cmFC−2. The operating conditions of the after burner and of the ammonia decomposition reactor are studied by varying the values of specific parameters. The levelized cost of energy of 0.221 $ kWh−1 was evaluated, as introduced by the International Energy Agency, for a system that operates at nomina... [more]

12.9% of the energy use in the EU originates from the commercial and public sector. It has therefore become a priority to optimize energy efficiency in these buildings. The purpose of this study has been to explore how energy demand in a new office building is affected by different internal heat gains, location, orientation, and façade design, and also to see how different indicators can change perspective on energy efficiency. The study was performed with simulations in IDA-ICE with different façade design and changes in internal heat gains (IHG), orientation, and location. Energy demand was then compared to two different indicators. Using a façade designed to lower solar heat gains had little effect on energy demand in the north of Sweden, but slightly more effect further south. The amount of internal heat gains had significant effect on energy demand. Making deeper studies on design and internal heat gains should therefore be prioritized in the beginning of new building projects so... [more]