Load power forecast is one of most important tasks in power systems operation and maintenance. Enhancing its accuracy can be helpful to power systems scheduling. This paper presents how to use partial real-time temperature information in forecasting load power, which is usually done using past load power and temperature data. The partial real-time temperature information means temperature information for only part of the entire prediction time interval. To this end, a long short-term memory (LSTM) network is trained using past temperature and load power data in order to forecast load power, where forecasted load power depends on the temperature prediction implicitly. Then, in order to deal with the case where nontrivial temperature prediction errors happen, a multi-layer perceptron (MLP) network is trained using the past data describing the relation between temperature variation and load power variation. Then, the temperature is measured at the beginning of the prediction time-interval... [more]

Microgrid is becoming an essential part of the power grid regarding reliability, economy, and environment. Renewable energies are main sources of energy in microgrids. Long-term solar generation forecasting is an important issue in microgrid planning and design from an engineering point of view. Solar generation forecasting mainly depends on solar radiation forecasting. Long-term solar radiation forecasting can also be used for estimating the degradation-rate-influenced energy potentials of photovoltaic (PV) panel. In this paper, a comparative study of different deep learning approaches is carried out for forecasting one year ahead hourly and daily solar radiation. In the proposed method, state of the art deep learning and machine learning architectures like gated recurrent units (GRUs), long short term memory (LSTM), recurrent neural network (RNN), feed forward neural network (FFNN), and support vector regression (SVR) models are compared. The proposed method uses historical solar rad... [more]

Commercial and residential building is one of the four major final energy consumption and end-use sectors. In this sector, cooling loads represent an important part of the energy consumption, and therefore, they must be minimized, improving the energy efficiency of buildings. Ventilated façades are one of the most widely used passive elements that are integrated into buildings, precisely with the aim of reducing these loads. This reduction is due to the airflow induced in the air cavity by the buoyancy forces, when the solar radiation heats the outer layer of the façade. In the open joint ventilated facades (OJVF), ventilation is attained through the open joints between the panels composing the outer layer. Despite the steadily growing research in the characterization of this type of system, few studies combine the numerical modelling of OJVF with experimental results for the assessment of the airflow in the ventilated cavities. This paper experimentally validates a numerical simulatio... [more]

The modeling of stator and rotor faults is the basis of the development of online monitoring techniques. To obtain reliable stator and rotor fault models, this paper focuses on dynamic modeling of the stator and rotor faults in real-time, which adopts a multiple-coupled-circuit method by using a winding function approach for inductance calculation. Firstly, the model of the induction machine with a healthy cage is introduced, where a rotor mesh that consists of a few rotor loops and an end ring loop is considered. Then, the stator inter-turn fault model is presented by adding an extra branch with short circuit resistance on the fault part of a stator phase winding. The broken rotor bar fault is then detailed by merging and removing the broken-bar-related loops. Finally, the discrete models under healthy and faulty conditions are developed by using the Tustin transformation for digital implementation. Moreover, the stator and rotor mutual inductances are derived as a function of the rot... [more]

Multi-scale bedding fractures, i.e., km-scale regional bedding fractures and cm-scale lamina-induced fractures, have been the focus of unconventional oil and gas exploration and play an important role in resource exploration and drilling practice for tight oil and gas. It is challenging to conduct numerical simulations of bedding fractures due to the strong heterogeneity without a proper mechanical criterion to predict failure behaviors. This research modified the Tien−Kuo (T−K) criterion by using four critical parameters (i.e., the maximum principal stress (σ1), minimum principal stress (σ3), lamina angle (θ), and lamina friction coefficient (μlamina)). The modified criterion was compared to other bedding failure criteria to make a rational finite element simulation constrained by the four variables. This work conducted triaxial compression tests of 18 column samples with different lamina angles to verify the modified rock failure criterion, which contributes to the simulation work on... [more]

Dilation behavior is of great importance for reasonable modeling of the stability of the host rock of the repository for high-level radioactive waste disposal. It is a suitable method for carrying out direct shear experiments to analyze the dilation behavior of rock with well understood physical meanings. Based on a series of direct shear experiments on granite samples from the Alxa candidate area under different normal stresses, the shear stress‒shear strain and shear stress‒normal strain relations have been studied in detail. Five typical stages have been divided associated with the fracturing process and deformation behaviors of the granite samples during the experimental process, and the method to determine the typical stress thresholds has been proposed. It has also been found that the increasing normal stress may reduce the maximum dilation angle, and when the normal stress is relatively lower, the negative dilation angle may occur during the post-peak stage. According to the dat... [more]

Increasing the share of renewables in energy markets influences the daily operation of thermal power units. High capacity power units are more frequently operated to balance power grids and, thus, steam boilers are exposed to unfavorable transient states. The aim of this work was to perform thermal and structural analyses of a boiler’s outlet steam header, with a capacity of 650∙103 kg/h (180 kg/s) of live steam. Based on the measured steam pressure and temperatures on the outer surface of the component, transient temperature fields were determined by means of an algorithm that allows determination of transient stress distributions on the internal and external surfaces, as well as at stress concentration regions. In parallel, a finite element method simulation was performed. A comparison of the obtained results to a finite element analysis showed satisfactory agreement. The analyses showed that the start-up time could be reduced because the total stress did not exceed the allowed value... [more]

Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventions and are solely driven by thermal gradients and gravitational force. This brings up new needs for performance and reliably assessment. This paper provides a review on fundamental approaches to model and analyze the performance of passive heat removal systems exemplified for the passive heat removal chain of the KERENA boiling water reactor concept developed by Framatome. We discuss modeling concepts for one-dimensional system codes such as ATHLET, RELAP and TRACE and furthermore for computational fluid dynamics codes. Part I dealt with numerical and experimental methods for modeling of condensation inside the emergency condenser and on the containment cooling condenser. This second part deals with boiling and two-phase flow instabilities.

Electronic devices can be damaged in an undesirable manner if the junction temperature achieves high values in order to cause thermal runaway and melting. This paper describes the mathematical model to calculate the power losses in power semiconductor devices used in bidirectional rectifier which supplies a resistive-inductive load. The obtained thermal model can be used to analyse the thermal behaviour of power semiconductors in steady-state conditions, at different values of the firing angle, direct current, air speed in the case of forced cooling, and different types of load. Also, the junction and case temperature of a power thyristor have been computed. In order to validate the proposed mathematical model, some experimental tests have been performed. The theoretical values are in good concordance with the experimental data and simulated results.

The performance of ground-coupled heat pump systems (GCHPs) operating under significant groundwater flow can be difficult to predict due to advective heat transfer in the subsurface. This is the case of the Carignan-Salières elementary school located on the south shore of the St. Lawrence River near Montréal, Canada. The building is heated and cooled with a GCHP system including 31 boreholes subject to varying groundwater flow conditions due to the proximity of an active quarry being irregularly dewatered. A study with the objective of predicting the borehole temperatures in order to anticipate potential operational problems was conducted, which provided an opportunity to evaluate the impact of groundwater flow. For this purpose, a numerical model was calibrated using a full-scale heat injection test and then run under different scenarios for a period of twenty years. The heat exchange capacity of the GCHP system is clearly enhanced by advection when the Darcy flux changes from 6 × 10−... [more]

The electrical efficiency and durability of a photovoltaic (PV) cell degrades as its temperature increases. Accordingly, there have been continued efforts to control the cell temperature by cooling the PV module. Generally, passive PV cooling using heat sinks attached on the back of the PV module can improve the electrical efficiency. However, few experimental studies have evaluated the effect of the heat sink shape on PV cooling. Therefore, this study proposed a passive cooling technology using meshes made of iron and aluminum, and performed indoor tests using a solar simulator to analyze the cooling performance. The experimental results demonstrated that iron and aluminum meshes reduced the PV module temperature by approximately 4.35 °C and 6.56 °C, respectively. Additionally, numerical studies were performed using a computational fluid dynamics (CFD) simulation to compare the cooling fins and meshes. The numerical results showed that the cooling fins exhibited a better cooling perfo... [more]

Reliable energy models are needed to determine building energy performance. Relatively detailed energy models can be auto-generated based on 3D shape representations of existing buildings. However, parameters describing thermal performance of the building fabric, the technical systems, and occupant behavior are usually not readily available. Calibration with on-site measurements is needed to obtain reliable energy models that can offer insight into buildings’ actual energy performances. Here, we present an energy model that is suitable for district-heated multifamily buildings, based on a 14-node thermal network implementation of the ISO 52016-1:2017 standard. To better account for modeling approximations and noisy inputs, the model is converted to a stochastic state-space model and augmented with four additional disturbance state variables. Uncertainty models are developed for the inputs solar heat gains, internal heat gains, and domestic hot water use. An iterated extended Kalman fil... [more]

Laminar flow of ethylene glycol-based silicon nitride (EG-Si3N4) nanofluid in a smooth horizontal pipe subjected to forced heat convection with constant wall heat flux is computationally modeled and analyzed. Heat transfer is evaluated in terms of Nusselt number (Nu) and heat transfer coefficient for various volume fractions of Si3N4 nanoparticles in the base fluid and different laminar flow rates. The thermophysical properties of the EG-Si3N4 nanofluid are taken from a recently published experimental study. Computational modelling and simulation are performed using open-source software utilizing finite volume numerical methodology. The nanofluid exhibits non-Newtonian rheology and it is modelled as a homogeneous single-phase mixture, the properties of which are determined by the nanoparticle volume fraction. The existing features of the software to simulate single-phase flow are extended by implementing the energy transport coupled to the fluid flow and the interaction of the fluid fl... [more]

As the number of active components increase, distribution networks become harder to control. Microgrids are proposed to divide large networks into smaller, more manageable portions. The benefits of using microgrids are multiple; the cost of installation is significantly smaller and renewable energy-based generators can be utilized at a small scale. Due to the intermittent and time dependent nature of renewables, to ensure reliable and continuous supply of energy, it is imperative to create a system that has several generators and storage systems. The way to achieve this is through an energy management system (EMS) that can coordinate all these generators with a storage system. Prior to on-site installation, validation studies should be performed on such controllers. This work presents a standardized communication modeling based on IEC 61850 that is developed for a commercial microgrid controller. Using commercial software, different terminals are set up as intelligent electronic device... [more]

In the delicate context of climate change, biomass gasification has been demonstrated to be a very useful technology to produce power and hydrogen. Nevertheless, in literature, there is a lack of a flexible and fast but accurate model of biomass gasification that can be used with all the combinations of oxidizing agents, taking into account both organic and inorganic contaminants, and able to give results that are more realistic. In order to do that, a model of biomass gasification has been developed using the chemical engineering software Aspen Plus. The developed model is based on the Gibbs free energy minimization applying the restricted quasi-equilibrium approach via Data-Fit regression from experimental data. The simulation results obtained, considering different mixes of gasifying agents, were compared and validated against experimental data reported in literature for the most advanced fluidized bed technology. The maximum discrepancy value obtained for hydrogen, with respect to... [more]

To achieve climate goals, it is necessary to decarbonise the transport sector, which requires an immediate changeover to alternative power sources (e.g., battery powered vehicles). This change will lead to an increase in the demand for electrical energy, which will cause additional stress on power grids. It is therefore necessary to evaluate energy and power requirements of a future society using e-mobility. Therefore, we present a new approach to investigate the influence of increasing e-mobility on a distribution grid level. This includes the development of a power grid model based on a cellular approach, reducing computation efforts, and allowing time and spatially resolved grid stress analysis based on different load and renewable energy source scenarios. The results show that by using the simplified grid model at least seven times, more scenarios can be calculated in the same time. In addition, we demonstrate the capability of this novel approach by analysing the influence of diff... [more]

Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventions and are solely driven by thermal gradients and gravitational force. This brings up new needs for performance and reliably assessment. This paper provides a review on fundamental approaches to model and analyze the performance of passive heat removal systems exemplified for the passive heat removal chain of the KERENA boiling water reactor concept developed by Framatome. We discuss modelling concepts for one-dimensional system codes such as ATHLET, RELAP and TRACE and furthermore for computational fluid dynamics codes. Part I deals with numerical and experimental methods for modelling of condensation inside the emergency condensers and on the containment cooling condenser while part II deals with boiling and two-phase flow instabilities.

The Savonius-type hydraulic turbine, mainly known for its good self-starting properties and simple structure, not only has energy capturing characteristics but also has a certain effect on flow velocity reduction. Aside from ensuring energy capture efficiency, studying the effects of parameters on the flow velocity reduction capacity is of great significance for the protection of mariculture, as it can reduce the damage to cages and fishes. In this study, a computational fluid dynamics method was carried out to investigate the hydrodynamic characteristics and variations in the wake of a turbine. The accuracy of the simulation results was verified by experimental comparison. Firstly, the velocity contours and vectors were studied in detail to reveal the mechanism of the flow velocity reduction effect. Secondly, the velocity attenuation coefficient and relative attenuation length were formulated by the variation rule of the velocity field to evaluate the turbine reduction strength and ra... [more]

With an increasing interest in ultra-high frequency (UHF) partial discharge (PD) measurements for the continuous monitoring of power transformers, it is necessary to know where to place the UHF sensors on the tank wall. Placing a sensor in an area with many obstructions may lead to a decrease in sensitivity to the UHF signals. In this contribution, a previously validated simulation model of a three-phase 300 MVA, 420 kV power transformer is used to perform a sensitivity analysis to determine the most sensitive sensor positions on the tank wall when PD activity occurs inside the windings. A matrix of UHF sensors located on the transformer tank is used to perform the sensitivity analysis. Some of the windings are designed as layer windings, thus preventing the UHF signals from traveling through them and creating a realistic situation with very indirect propagation from source to sensor. Based on these findings, sensor configurations optimized for UHF signal sensitivity, which is also req... [more]

Hywind-Scotland is a wind farm in Scotland that for many reasons is at the leading edge of technology and is located at a paradigmatic study area for offshore wind energy assessment. The objective of this paper is to compute the Capacity Factor ( C F ) changes and instantaneous power generation changes due to seasonal and hourly fluctuations in air density. For that reason, the novel ERA5 reanalysis is used as a source of temperature, pressure, and wind speed data. Seasonal results for winter show that C F values increase by 3% due to low temperatures and denser air, with economical profit consequences of tens of thousands (US$). Hourly results show variations of 7% in air density and of 26% in power generation via FAST simulations, emphasizing the need to include air density in short-term wind energy studying.

Single room ventilation units with heat recovery is one of the ventilation solutions that have been used in renovated residential buildings in Estonia. In multi-story buildings, especially in a cold climate, the performance of units is affected by the stack effect and wind-induced pressure differences between the indoor and the outdoor air. Renovation of the building envelope improves air tightness and the impact of the pressure conditions is amplified. The aim of this study was to predict the air pressure conditions in typical renovated multi-story apartment buildings and to analyze the performance of room-based ventilation units. The field measurements of air pressure differences in a renovated 5-story apartment building during the winter season were conducted and the results were used to simulate whole-year pressure conditions with IDA-ICE software. Performance of two types of single room ventilation units were measured in the laboratory and their suitability as ventilation renovati... [more]

In the past decade, the condensation of internal air humidity in automotive headlamps has become more prevalent than ever due to the increased usage of a new light source—LEDs. LEDs emit far less heat than previously-used halogen lamps, which makes them far more susceptible to fogging. This fogging occurs when the internal parts of the headlamp fall to a temperature below the dew point. The front glass is most vulnerable to condensation due to its direct exposure to ambient conditions. Headlamp fogging leads to a decrease in performance and the possibility of malfunctions, which has an impact not only on the functional aspect of the product’s use but also on traffic safety. There are currently several technical solutions available which can determine the effectivity of ventilation systems applied for headlamp defogging. Another approach to this problem may be to use a numerical simulation. This paper proposes a CFD (computational fluid dynamics) simulation with a slightly simplified 3D... [more]

Domestic heating accounts for 64% of domestic energy usage in the UK, yet there are currently very few viable options for low carbon residential heating. The government’s carbon plan commits to improving the uptake of district heating connections in new build dwellings, but the greatest carbon saving can be made through targeting traditional housing stock. This paper aims to quantify the potential carbon and energy savings that can be made by connecting a traditional tenement building to a district heating scheme. The study uses a transient system simulation tool (TRNSYS) model to simulate the radiator system in a tenement block and shows that a significant benefit can be achieved by reducing the supply temperature; however, the minimum supply temperature is drastically limited by the building condition. Therefore, the study also critically compares the benefits of a lower supply temperature against minor refurbishments. It was found that improving building conditions alone could offer... [more]

The selective catalytic reduction (SCR) methodology is notably recognized as the widely applied strategy for NOX control in exhaust after-treatment technologies. In real SCR systems, complex unsteady turbulent multi-phase flow phenomena including poly-dispersed AdBlue® spray evolve with a wide ranging relative velocity between the droplet phase and carrier gas phase. This results from an AdBlue® spray that is injected into a mixing pipe which is cross-flowing by a hot exhaust gas. To reduce the complexity while gaining early information on the injected droplet size and velocity needed for a minimum deposition and optimal conversion, a single droplet with a specified diameter is addressed to mimic a spray featuring the same Sauter Mean Diameter. For that purpose, effects of turbulent hot cross-flow on thermal decomposition processes of a single AdBlue® droplet are numerically investigated. Thereby, a single AdBlue® droplet is injected into a hot cross-flowing stream within a mixing pipe... [more]

Common kinetic parameters were obtained for leached and non-leached samples of vine wood biomass. Both samples were considered to have different proportions of cellulose, hemicellulose, and lignin compositions as a result of the leaching process. The two samples were analyzed in terms of pyrolysis kinetic parameters using non-isothermal thermogravimetric analysis. Furthermore, the classic Friedman isoconversional method, a deconvolution procedure using the Fraser−Suzuki function, and a modified Friedman method from a previous study on the delay in conversion degree were satisfactorily applied. The observed difference when the deconvolution technique was applied suggests that the classic Friedman method is not adequate for studying the pyrolysis of individual vine wood biomass components. However, this issue was solved by studying the delay in conversion degree of both biomasses and calculating the kinetic parameters using the resulting information. This procedure was found to be useful... [more]