Part I of the publication series addressed the fundamentals of lifetime assessment of prototype Francis turbines. This paper (Part II) focuses on the numerical part of the procedure. The essential steps and requirements shall be presented (background). The starting points for the numerical considerations are the pressure fields of the transient CFD simulations, which are exported per time step and applied to the existing structure via a fluid−structure interaction. That enables a transient mechanical stress calculation to be conducted, resulting in the fatigue analysis of the component to estimate the remaining lifetime. The individual model requirements should be represented accordingly and applied to the prototype facility (method). The results obtained from this application should be discussed and evaluated. It has to be mentioned that the validation of the numerical results will be performed at Part IV of this publication series (results). The present paper will end up discussing t... [more]

The prominence of two-dimensional hexagonal boron nitride (2D h-BN) nanomaterials in the energy industry has recently grown rapidly due to their broad applications in newly developed energy systems. This was necessitated as a response to the demand for mechanically and chemically stable platforms with superior thermal conductivity for incorporation in next-generation energy devices. Conventionally, the electrical insulation and surface inertness of 2D h-BN limited their large integration in the energy industry. However, progress on surface modification, doping, tailoring the edge chemistry, and hybridization with other nanomaterials paved the way to go beyond those conventional characteristics. The current application range, from various energy conversion methods (e.g., thermoelectrics) to energy storage (e.g., batteries), demonstrates the versatility of 2D h-BN nanomaterials for the future energy industry. In this review, the most recent research breakthroughs on 2D h-BN nanomaterials... [more]

The trigeneration plants for combined cooling, heating, and electricity supply, or integrated energy systems (IES), are mostly based on gas reciprocating engines. The fuel efficiency of gas reciprocating engines depends essentially on air intake temperatures. The transformation of the heat removed from the combustion engines into refrigeration is generally conducted by absorption lithium-bromide chillers (ACh). The peculiarity of refrigeration generation in food technologies is the use of chilled water of about 12 °C instead of 7 °C as the most typical for ACh. This leads to a considerable cooling potential not realized by ACh that could be used for cooling the engine intake air. A refrigerant ejector chiller (ECh) is the simplest in design, cheap, and can be applied as the low-temperature stage of a two-stage absorption-ejector chiller (AECh) to provide engine intake air cooling and increase engine fuel efficiency as result. The monitoring data on gas engine fuel consumption and power... [more]

Energy consumption in residential, commercial and industrial buildings is one of the major contributors to global warming. Due to the increase in the latter, and growing global energy crisis, more attention is being paid to renewable energy resources (RES). The use of innovative concepts in existing buildings is gaining popularity to provide reduction in energy requirements for electricity, heating and cooling. In this paper, an electricity, heating and cooling cooperation mechanism among neighboring buildings with RES is proposed. It relies on adjusting the RES tariff with a mutual agreement between the neighboring buildings, with an aim to minimize the operational costs. For this purpose, a mathematical model is developed for joint energy cooperation, where surplus energy in one of the buildings is shared with others, thereby reducing dependency on the grid. The optimization structure of the environment friendly energy cooperation is nonlinear, which is linearized using the McCormick... [more]

In the current study, a hemispherical shell vapor chamber (HSVC) was proposed and manufactured. A unique system of the HSVC consists of a very short evaporator space and a large condenser area with an inner and outer surface. The HSVC has a bottom surface that can be easily attached to the heat source and its radius varies from 0.045 m (near the bottom surface) to 0.078 m at the top with a curved side. An entirely new design of the integrated section of the large condenser with the evaporator section was verified using a new but simple concept. The current hemispherical shell vapor chamber (HSVC) was made from stainless steel. The current HSVC was specified with an outer/inner diameter of 78/70 mm at the top, a depth of 47 mm in the inner surface area, a total height of 60 mm, 30 mm at the bottom of the inner center, and a diameter of 45 mm on the surface of the outer bottom area. Three different models were manufactured and tested to verify which HSVC reached a high thermal performanc... [more]

This paper presents a partial power processing and an efficiency analysis of dc-dc differential converters based on the use of two basic converters of the same group: the positive or negative group. The paper contributes theoretical analysis and demonstrates that the differential converters based on the positive group process has more power than the load requires, and that the differential converters based on the negative group process has less power than the load needs. This is an important advantage of the negative group converters, since a parcel of the output power is directly transferred by the input source to the load, resulting in partial power processing. In order to verify the theoretical analysis herein developed, ten prototypes are evaluated considering an input voltage of 20 V and output power of 100 W.

Active building envelopes that act as energy converters—gathering on-site available renewable energy and converting it to thermal energy or electricity—is a promising technological design niche to reduce energy consumption in the building sector, cut greenhouse gas emissions, and thus tackle climate change challenges. This research adds scientific knowledge in the field of composite building envelope structures containing phase-change materials for thermal energy storage. In this study, the focus lies on the cooling phase of the diurnal gain and release of solar energy. The experimental setup imitates day and night environment. Six alterations of small-scale solar facade modules are tested in two different configurations—with and without the adjustable insulation layer on their outer surface during the discharging phase. Modules explore combinations of aerogel, air gap, and Fresnel lenses for solar energy concentration. The results allow us to compare the impact of the application of a... [more]

A reliable estimate of the wind potential in the marine atmospheric boundary layer (MABL) is of great importance to justify the energetic viability of new offshore wind farms. The purpose of the study is to provide an additional tool for the prediction of the energy that a wind turbine would produces in the open sea from the usual way of measurements at sea, that is, when they are carried out with measuring masts, where the meteorological data are obtained at levels much lower than those of a wind turbine hub. For this, the variation in the wind speed with the height in the MABL is determined, based on the Monin−Obukhov similarity theory, according to the boundary conditions of the air−sea interface, where the input data for the Validation of the results are extracted from the German FINO 3 research platform during the years 2016, 2017, and 2018. It is applied to the production of electrical energy from a 6.0 MW commercial wind turbine, with the hub at 100 m above the sea surface. As a... [more]

A climate-friendly and CO2-neutral energy supply for agricultural farms is the subject of investigation of this study. The supply concerns the internal economy (buildings and animal husbandry) as well as the production of synthetic fuels for outdoor work (cultivation of the fields). This energy is in demand with many customers, e.g., the dairy cooperative Arla Foods, whose goal is the production of cow’s milk with net-zero CO2 emissions by the year 2050. The operational energy system considered here included renewable electricity generation, covering electricity consumption in the cowshed, battery storage for times without electricity generation, the production of synthetic fuels and feeding into the public power grid. Fluctuations depending on the day and the season were taken into account for electricity at 15-min intervals and for fuel per calendar week for one year. The aim was to determine the necessary capacities of renewable energy (RE) generation systems and production systems... [more]

The motivation for research to help address climate change is a continuous process of searching for eco-friendly materials in the building industry, which will allow minimizing the negative impact of this sector on the environment. The main objective of the paper is to assess the properties of a natural resource such as straw as an eco-friendly material in various variants for use in low-energy demand construction. The research results will fill the knowledge gap in the field of numerical analyses of the energy demand of straw material buildings based on the results of the conducted laboratory tests. A test of a heat transfer coefficient was conducted with different orientation of straw stalks. Then, samples were subject to a fire resistance test to determine material behavior at 1000 °C. During the fire resistance test, the clay-based plaster was ‘burnt out’, which hardened its structure, effectively preventing flames from reaching the insulation layers in the form of straw stalks. As... [more]

This paper presents the results of testing the electrical strength of an insulating system in a vacuum obtained from three noble gases: argon, neon, helium, and air. The breakdown voltages were measured for contact gaps of 1 mm and 2 mm. A difference was observed in the pressure range where the electrical strength was kept constant. The chamber filled with helium residual gases lost its insulating properties at the highest pressure among the tested gases (2.00 × 100 Pa at contact gap d = 2 mm), while the chamber filled with argon gas lost its insulating properties at the lowest pressure among the tested gases (2.00 × 10−1 Pa at contact gap d = 2 mm). After a decrease in electrical strength, an intense glow discharge was observed. A theoretical description related to the initiation of an electrical breakdown in vacuum insulating systems is also presented. The situation in which the discharge chamber with a contact system was filled with the mentioned gases was analyzed. The mean free pa... [more]

In response to extreme climate change, China has set a goal of reaching emission peak by 2030 and achieving carbon neutrality by 2050. Energy conservation and emission reduction of building heating in northern China are key to achieving this goal. Based on building area prediction and energy consumption intensity, this paper establishes a model for calculating heating energy consumption and carbon emissions in northern residential buildings at the macro level, which provides a basis for formulating policies related to heating and emission reduction in northern buildings. Based on the research method of scenario projection, combining the carbon emission subsets and future heating energy mix projections in northern China, the heating energy consumption in northern China decreases to 175, 149 and 135 Mtce in 2050 under the baseline, medium control and strict control scenarios, respectively. The heating energy consumption in the northern region should be controlled at least under the mediu... [more]

Investigating the constructions of borehole heat exchangers with high efficiency (unit heat transfer between the heat carrier and ground) is important. One of the means to improve efficiency is the use of the most efficient construction of the borehole heat exchanger. The paper describes research on borehole heat exchangers’ thermal efficiency, which is mainly characterized by parameters obtained from a thermal response test: effective thermal conductivity and borehole thermal resistivity. The borehole heat exchangers of the Laboratory of Geoenergetics in Poland were studied. Based on thermal response test interpretation and empirical equations, one of which is proprietary, the heat transfer is calculated independent of the duration of the thermal response test. Other conditions for using borehole heat exchangers in downtowns are discussed. The research aims to determine the best borehole heat exchanger design from five basic possibilities studied. A lack of unequivocal statements rega... [more]

Nuclear power plants in the United States are increasingly challenged to compete in wholesale electricity markets due to the low electricity costs and increasingly dynamic grid conditions from competing generation sources. An alternative market for nuclear power is industrial facilities that can use the thermal and/or electrical power generated by a nuclear power plant to offset the economic losses incurred by electricity market challenges. A generic pressurized water reactor (PWR) simulator was used to show the results of a basic design for a generic thermal power extraction system and tests were run using a set of procedures to show what happens when a nuclear power plant transitions from full electrical power dispatch to 15% and 50% thermal power dispatch. This type of operation leads to losses in turbine performance efficiency due to the deviation from the design operating point, but because the thermal power is also used by the industry load without conversion losses, the combined... [more]

Polarization is a universal phenomenon that occurs inside lithium-ion batteries especially during operation, and whether it can be accurately characterized affects the accuracy of the battery management system. Model-based approaches are commonly adopted in studies of the characterization of polarization. Towards the application of the battery management system, a lumped diffusion model with three parameters was adopted. In addition, a joint algorithm composed of the Particle Swarm Optimization algorithm and the Levenberg-Marquardt method is proposed to identify model parameters. Verification experiments showed that this proposed algorithm can significantly improve the accuracy of model output voltages compared to the Particle Swarm Optimization algorithm alone and the Levenberg-Marquardt method alone. Furthermore, to verify the real-time performance of the proposed method, a hardware implementation platform was built, and this system’s performance was tested under actual operating con... [more]

A model has been developed and implemented in the software package BoilFAST that allows for reliable calculations of the self-pressurization and boil-off losses for liquid hydrogen in different tank geometries and thermal insulation systems. The model accounts for the heat transfer from the vapor to the liquid phase, incorporates realistic heat transfer mechanisms, and uses reference equations of state to calculate thermodynamic properties. The model is validated by testing against a variety of scenarios using multiple sets of industrially relevant data for liquid hydrogen (LH2), including self-pressurization and densification data obtained from an LH2 storage tank at NASA’s Kennedy Space Centre. The model exhibits excellent agreement with experimental and industrial data across a range of simulated conditions, including zero boil-off in microgravity environments, self-pressurization of a stored mass of LH2, and boil-off from a previously pressurized tank as it is being relieved of vap... [more]

Electricity generation is becoming increasingly flexible in Europe these days. Due to the integration of new renewable energy sources like wind and photovoltaic, other conventional resources, such as hydropower, operate within a brought range around their best efficiency point, thus leading to higher dynamical loads at the water-bearing parts, especially at the runner and the guide vanes (background). By scrutinizing the literature of the past years, one could summarize the outcome in that way, that research projects focused either on model measurements with higher visual accessibility or, less often, on prototype measurements in existing power plants. Today prototype measurements are performed, if possible, to eliminate scaling effects. Moreover, increasing computing power allows prototype simulations to be carried out within a reasonable time. At the acknowledged research projects, prototype and model measurements and numerical simulations have been performed to identify the main gap... [more]

The present work reports an integrated (experimental and numerical) methodology that combines the development of a finite element multiphysics model with an experimental strategy to optimally design an eddy current damper for automotive suspensions. The multiphysics model couples the whole set of time-dependent electromagnetic, thermal, mechanical, and fluid−wall interaction (CFD) partial differential equations. The developed FE model was validated against both literature model predictions and in-house experimental data. The electromagnetic model takes into account the magnetic material characteristics of the ferromagnetic material and iron poles. Loss separation and the Jiles−Atherton hysteresis models were invoked to determine the heat generated in the soft iron parts. The computation of the fluid−wall interaction phenomena in the air gap allowed for the prediction of the temperature field across the solid materials, including the magnets. The design of the EC damper addresses the ef... [more]

In order to eradicate water−energy−food poverty, Sustainable Development Goals (SDG) proposed milestones to overcome the feeding problem. The development of water−energy−food (WEF) nexus management tools, and approaches has increased during last years. The aim of this research is to review WEF nexus management methods, tools, and examples to identify gaps, goals, or future development that arise when modelling goods management issues for designing a sustainable development framework. It is also presented the food−biofuel competition for resources problem focusing in threatened systems. In addition to the resource trade-off quantification issue, it proposed an analysis for WEF systems management from economic, environmental, and practical points of view with the aim of identifying results, challenges, gaps, or assumptions for nexus. The renewable energy highlights as an enabler for sustainable development.

With the number of communicating sensors linked to the Internet of Things (IoT) ecosystem increasing dramatically, well-designed indoor light energy harvesting solutions are needed. A first step in this direction would be to be able to accurately estimate the harvestable energy in a specific light environment. However, inside, this energy varies in spectral composition and intensity, depending on the emission source as well as the time of day. These challenging conditions mean that it has become necessary to obtain accurate information about these variations and determine their impact on energy recovery performance. In this context, this manuscript presented a method to apply an innovative energy harvesting estimation method to obtain practical and accurate insight for the design of energy harvesting systems in indoor environments. It used a very low-cost device to obtain spectral information and fed it to supervised machine learning classification methods to recognize light sources. F... [more]

This paper presents a model-based analysis of variability of thermodynamic and chemical parameters in a rotary kiln (RK) during thermal treatment of animal waste. The core process of chemical treatment of waste takes place in RKs; the process involves heating, gasification and partial combustion of the waste. Control over these parameters, and especially the level of complete combustion, determines the quality and efficiency of the process. In operational practice, control and analysis of the variability of process parameters is complicated by the high degree of simultaneity of individual transformations, random disruptions of the process and metrological difficulties resulting from high temperature and chemical activity of the materials being processed. The purpose of preparing the model was to obtain a tool for predicting variability of selected process parameters. By definition, model calculations assume no influence of disturbances on output values, which makes it possible to acqui... [more]

This paper studies the architectural implications, in terms of size and space requirements, of battery technologies in a built environment using renewable energy and energy storage technologies. These aspects will be of particular interest as the world transitions to a low carbon future. This paper is the first to focus on the physical size of storage systems required to provide particular storage characteristics. The research used a quantitative case study methodology and focused on the investigation of nine battery technologies based on potential technology and energy consumption scenarios in 2030. Different residential building scales at a local distribution scale are explored considering sub-daily autonomy periods. Four case studies in a 2030 scenario are presented. For each case study, the nominal capacity, spatial requirements and costs are assessed for each technology. A schematic characterisation of the technologies was derived considering their suitability across these aspects... [more]

The increasing use of renewable energy sources (RES) and their integration into transmission systems requires extensive studies to get more benefits from these sources. Stability analysis is one of the most crucial issues in these systems, and therefore needs to be studied in depth. In this paper, an analytical study was conducted for the stability assessment of the Iraqi super grid after adding a solar power plant with a capacity of 1000 MW using both HVAC and HVDC links for comparison purposes. Thus, the objective of this study was to determine the best way to integrate RES into the power grid while improving its performance. The system’s stability was evaluated for two types of faults: line and bus disturbances. The strength of the grid and its ability to absorb the newly added energy was also studied. The simulations were performed with the PSS/E software using the Newton-Raphson method for a 500 km transmission line length. The results showed that the HVDC link outperforms the HVA... [more]

Falling-film drain water heat recovery (DWHR) systems are heat exchangers utilized in residential buildings for recovering energy from greywater. A recent publication by the authors contained a validated model that can be used to predict the performance of DWHR heat exchangers under variable flowrates and temperatures, and this work shows the implementation of the model into Transient System Simulation Tool (TRNSYS) software to perform energy simulations. This work aims to show the different plumbing configurations in which DWHR heat exchangers could be installed, and to simulate their performance under various conditions. The results show that plumbing configuration has a significant impact on energy savings expected from DWHR heat exchangers, and maximum savings are achieved in equal-flow configuration. However, other plumbing configurations provide significant savings, and the mains temperature could dictate which configuration provides higher energy savings.

Several studies have reported the importance of optimally operating the absorption column in a post-combustion CO2 capture (PCC) plant. It has been demonstrated in our previous work how economic model predictive control (EMPC) has a great potential to improve the operation of the PCC plant. However, the use of a general economic objective such as maximizing the absorption efficiency of the column can cause EMPC to drive the state of the system close to the constraints. This may lead to solvent overcirculation and flooding, which are undesirable. In this work, we present an EMPC with zone tracking algorithm as an effective means to address this problem. The proposed control algorithm incorporates a zone tracking objective and an economic objective to form a multi-objective optimal control problem. To ensure that the zone tracking objective is achieved in the presence of model uncertainties and time-varying flue gas flow rate, we propose a method to modify the original target zone with a... [more]