In power electronic applications, often a galvanic isolation barrier has to be passed. An example of this is the feedback control of isolated DC/DC converters where the secondary voltage has to be passed to the primary side where the control circuitry lies. For these applications, the use of optocouplers is well known in terrestrial applications. However, optocouplers tend to suffer degradation from the radiation damage induced by the space environment. For this reason, some space grade DC/DC converters use some form of magnetic feedback. In this paper, a magnetic analog isolator is presented. It will allow for passing an analog voltage through an isolation barrier by means of a magnetic transformer based circuit. It will be based on an LLC DC/DC converter so the gain between both sides of the isolator can be tuned. Design methodology will be presented so the circuit can be tailored for any foreseen application. In this paper, a simulation of its application in a Latching Current Limit... [more]

The energy improvement of building stock is essential to achieve a low-carbon economy. The improvement of façades is among the most common measures to reduce energy consumption. However, the effect of thermal bridges is undervalued in most cases. This study assesses the effect of improving building façades and thermal bridges. For this purpose, a case study is assessed for all climate zones in Spain, both in current and future scenarios, considering operational patterns from the COVID-19 pandemic. The study shows that the application of energy conservation measures focusing on reducing the thermal transmittance of façades and the linear thermal transmittance of thermal bridges has a more significant energy and environmental effect than other, more economical energy conservation measures that do not improve the effect of thermal bridges. Likewise, the application of energy conservation measures to improve façades can reduce carbon dioxide emissions but are far from achieving the 90% red... [more]

The publication concerns the problem of adopting proper environmental conditions in the assessment of mold development in the so-called thermal bridges in the form of corners. The paper discusses the factors determining the development of mold and the models that predict its growth. The conditions of the internal microclimate, which is used in hygrothermal diagnostics of walls, were also recalled. Thermal bridges are areas where mold development takes place, therefore the climatic conditions in the room taken for their assessment—As it is currently applied—Are considered inappropriate. This thesis is confirmed by the results of in situ studies of changes in temperature and relative humidity in the area of corners. Some of these findings are presented in the work. On their basis, the author introduces the concept of the so-called geometric climate that would take into account the change of these parameters within thermal bridges of the corner type.

Integrated electrical and heating networks (IEHNs) effectively improve energy utilization efficiency, reduce environmental pollution and realize sustainable development of energy. To realize the accurate, comprehensive and fast perception of the integrated electrical and heating networks, it is necessary to build a state estimation model. However, the robust state estimator of IEHNs based on the temperature drop equation, flow balance equation and power balance equation still have the problems of convergence and low computational efficiency. In this paper, a fast state estimation method based on weighted least absolute value is proposed, which makes partition calculation of ring-shaped heating network and radiant heating network under certain assumptions. Simulation results show that the method improves the efficiency of the robust state estimator on the premise of high accuracy.

Heat pumps are increasingly seen as efficient and cost-effective heating systems also in industrial applications. They can drastically reduce the carbon footprint of heating by utilizing waste heat and renewable electricity. Recent research on Stirling cycle-based very high temperature heat pumps is motivated by their promising role in addressing global environmental and energy-related challenges. Evaluating the environmental footprint of a heat pump is not easy, and the impacts of Stirling cycle-based heat pumps, with a relatively high temperature lift have received little attention. In this work, the environmental footprint of a Stirling cycle-based very high temperature heat pump is evaluated using a “cradle to grave” LCA approach. The results for 15 years of use (including manufacturing phase, operation phase, and decommissioning) of a 500-kW heat output rate system are compared with those of natural gas- and oil-fired boilers. It is found that, for the Stirling cycle-based HP, the... [more]

With an increasing share of renewable energy technologies in our energy systems, the integration of not only direct emission (from the use phase), but also the total life cycle emissions (including emissions during resource extraction, production, etc.) becomes more important in order to draw meaningful conclusions from Energy Systems Analysis (ESA). While the benefit of integrating Life Cycle Assessment (LCA) into ESA is acknowledged, methodologically sound integration lacks resonance in practice, partly because the dimension of the implications is not yet fully understood. This study proposes an easy-to-implement procedure for the integration of LCA results in ESA based on existing theoretical approaches. The need for a methodologically sound integration, including the avoidance of double counting of emissions, is demonstrated on the use case of Passivated Emitter and Rear Cell photovoltaic technology. The difference in Global Warming Potential of 19% between direct and LCA based emi... [more]

Increasing awareness of resource sustainability and waste management has led to the search for solutions while promoting circular economy principles. Among all kinds of lignocellulosic biomass available, one with growing interest is municipal forestry and greening waste (MFGW). MFGW makes up an important part of waste streams of municipal solid waste and is a potential feedstock for biological conversion in a lignocellulosic biorefinery. This work studied the fermentable sugars production from MFGW after steam explosion (SE) pretreatment combined with other pretreatments such as dilute acid, organosolv, and metal salts. A range of pretreatment conditions was evaluated according to different parameters: sugars recovery, degradation product generation, and enzymatic hydrolysis yield. At selected pretreatment conditions (diluted acid plus SE, 195 °C, 10 min, and 60 mg H2SO4/g MFGW), 77% of potential sugars content in MFGW was obtained. The effect of solids loading and enzyme dose on gluco... [more]

As most residents spend more than 90% of their time in buildings, acceptable and reasonable control of both indoor thermal comfort and air quality is imperative to ensure occupants’ health status and work productivity. However, current control strategies generally take either thermal comfort or indoor air quality as a single loop, rather than the concurrent control of two. To analyze their mutual influence, this study investigated the performance of three multi-control approaches, i.e., proportional integral derivative (PID) control of thermal comfort and a fixed outdoor air ratio, PID control of thermal comfort and design outdoor air rate, and PID control of thermal comfort and occupancy-based demand-controlled ventilation. As a pilot study, three typical control methods were implemented to a multi-zone building via OpenModelica modeling. The results indicate that indoor air temperature can be well-maintained under three control methods, however, the CO2 concentration under the fixed... [more]

With high sensitivity and strong tolerance capability for the fault resistance, the fault component-based directional relay (FCBDR) has drawn considerable attention from industry and academia. However, the best application environment for FCBDR no longer exists when considering the large-scale connection of the doubly fed induction generator (DFIG)-based wind farms. Through a detailed analysis of the superimposed impedance of DFIG, this paper reveals that the performances of FCBDRs may be shown negatively impacted by the fault behaviors of DFIG when the crowbar protection inputs. In addition, this paper proposes a mitigation countermeasure to deal with those issues. The proposed countermeasure takes advantage of the different superimposed impedance features of DFIG compared with that of the synchronous generator (SG) to enhance the adaptability of the conventional FCBDRs. Extensive simulation results show that the proposed countermeasure can differentiate the fault direction clearly un... [more]

The main purpose of the article was to identify and present the current situation and changes in higher education in the field of electricity and energy studies in the European Union countries. The specific objectives include determining the degree of concentration of education in the fields of electricity and energy in the EU countries, showing the directions of their changes, types of dominant education in this field, establishing the correlation between education in the fields of electricity and energy and the parameters assessing the achievement of circular economy assumptions in the energy sector. All Member States of the European Union were deliberately selected for research. The research period covered the years 2013−2018. The source of the materials is a literature review on the subject and Eurostat data. For the analysis and presentation of materials, methods such as descriptive, tabular, graphical, dynamics indicators with a constant basis, Gini concentration coefficient, con... [more]

With the development trend of large-scale and flexible structures in engineering, the research on drag reduction of structures becomes more urgent. This paper presents a drag reduction design method for box girders based on the bionic method. Through the analysis of the Ostracion cubicus body shape, three features of the “fish mouth”, which were helpful for drag reduction were extracted. Then the bionic design model with the height of the box girder (D) as the design variable was obtained. By attaching lightweight materials to the windward side, the bionic shape of the structure can be realized without changing the loading characteristics of the original structure. Taking a box girder (rectangular cylinder, side ratio B/D = 0.6) as a prototype, the flow around two structures (rectangular cylinder and bionic attachment cylinder) was numerically simulated. The results show that the drag coefficient of the bionic attachment structure is reduced by 66.5%. The reduction of wind-load means t... [more]

Data on the thermochemical plants fed by solid biomass in the north-west area of Italy (Liguria, Lombardy, Piedmont and Aosta Valley) have been organised, analysed and discussed. Moreover, the biomass availability and potential has been evaluated. A total of 28,167 plants have been categorised according to their typology and output: thermo-electric power plants for electricity production, thermal plants for heat production, cogeneration plants for combined heat and electricity production and district heating installations for local heating purposes. In general, separate observations for the different provinces may be drawn. Liguria stands out as the most evident case of under-exploited biomass potential, followed by Aosta Valley, which, however, is rich in hydroelectricity. Lombardy and Piedmont are more virtuous and have several plants in their territory. The construction of new plants and the upgrade of existing ones may bring noteworthy benefits, as well as the use of added value su... [more]

Fossil energy inputs and greenhouse gas (GHG) emissions associated with the cultivation and transport of sugarcane (Saccharum officinarum) for bioethanol production in Tanegashima, Japan, were estimated by life cycle assessment (LCA). The aim was to understand the effects of combined systems of polyethylene mulching treatment (mulching at planting and every ratooning, MM; mulching only at planting, MU; and untreated, i.e., no mulching at all, UU) and cultivar (a cold-tolerant genotype, NiTn18, and a conventional variety, NiF8). The mulch treatments and cultivars were combined to create six cultivation systems that were used to conduct a comparative assessment of cradle-to-gate energy inputs and emissions for bioethanol production. The LCA results showed that the energy inputs and GHG emissions resulting from the MM/NiF8 system were 6.29 MJ L−1 and 0.500 kg CO2e L−1, which were 14% and 23% lower, respectively, than the corresponding values in the UU/NiF8 system. In contrast, the MU/NiF8... [more]

This research work proposed a hybrid model to maximize energy consumption and maximize user comfort in residential buildings. The proposed model consists of two widely used optimization algorithms named the firefly algorithm (FA) and genetic algorithm (GA). The hybridization of two optimization approaches results in a better optimization process, leading to better performance of the process in terms of minimum power consumption and maximum occupant’s comfort. The inputs of the optimization model are illumination, temperature, and air quality from the user, in addition with the external environment. The outputs of the proposed model are the optimized values of illumination, temperature, and air quality, which are, in turn, used in computing the values of user comfort. After the computation of the comfort index, these values enter the fuzzy controllers, which are used to adjust the cooling/heating system, illumination system, and ventilation system according to the occupant’s requirement... [more]

The use of lightweight concrete for the construction of single-family houses has become increasingly popular in Spain. In this paper, single-family houses with different shape factors and window-to-wall ratios are analysed from both a thermal and environmental perspective using Passive House Planning Package (PHPP) software to calculate the energy demand. The study has been carried out for different Atlantic microclimates (coastal, inland, and mountain) in northern Spain. What most affects the thermal energy used for air conditioning is the variation of the microclimates, so the study focuses mainly on this aspect. Operational energy for heating has decreased greatly via the use of high degree of insulation and hence the next task is to decrease the total energy consumed taking into account the embodied energy. Impacts on Primary Energy and Global Warming Potential are calculated using a cradle-to-grave approach. The energy use for heating and domestic hot water is analysed for differe... [more]

Rapid urbanization, global warming and enhanced quality of life have significantly increased the demand of indoor thermal comfort and air conditioning systems are not a luxury anymore, but a necessity. In order to fulfil this need, it is imperative to develop affordable and environmentally friendly cooling solutions for buildings. In this work, the 3E performance (energetic, economic and environmental) of electrically driven water-cooled vapour compression systems and thermally (solar) driven vapour absorption cooling systems are evaluated and the parameters affecting the performance of solar-driven vapour absorption systems are investigated. The energy simulation software TRNSYS is used to simulate the performance of both systems in order to fulfil the cooling needs of an industrial manufacturing building for the typical climate conditions for Lahore, Pakistan. Primary energy saving, initial investment, operational cost, and carbon footprint indices are used to analyse the performance... [more]

An essential aspect of wastewater treatment systems based on membranes is fouling, which leads to a decrease in their performance and durability. The membrane biofouling is directly related to the deposition of biological particles (e.g., microorganisms in the form of biofilm) on the membrane surface. The objective of the study was to investigate the possibility of using nonthermal plasma for membrane treatment to overcome the biofouling problem. The removal of biological cells from the membrane surface was performed in a dielectric barrier discharge (DBD) plasma. The biofoulant (i.e., activated sludge) on the surface of membranes was treated with plasma for 3−10 min, corresponding to a plasma dose of 13−42 J cm−2. Results of biofouling removal studies indicated that the process was very efficient (i.e., lethal effect was also observed) and dependent on the type of membrane and exposure time to the nonthermal plasma. Moreover, investigations of the influence of plasma treatment on extr... [more]

The construction industry is responsible for a high percentage of the energy consumed on the planet and the emission of greenhouse gases, therefore it is considered necessary to rethink many of the processes that this industry carries out in order to reduce its environmental impact. For this, one of the paths could take into account the Life Cycle Assessment of the used materials, for which it is necessary to evaluate this aspect through indicators that allow the qualification and quantification of the weight of these environmental impacts. In this context, this article presents a methodological proposal for the quantitative evaluation of the embodied primary energy and CO2 production at each stage of the life cycle of prefabricated structural systems, taking as case studies eight prototypes from the “Solar Decathlon” competition in its editions of Europe (2014), United States (2015) and Latin America (2015), through a Simplified Life Cycle Analysis, using the Eco Audit tool from CES E... [more]

Data centers (DCs) are becoming increasingly important in recent years, and highly efficient and reliable operation and management of DCs is now required. The generated heat density of the rack and information and communication technology (ICT) equipment is predicted to get higher in the future, so it is crucial to maintain the appropriate temperature environment in the server room where high heat is generated in order to ensure continuous service. It is especially important to predict changes of rack intake temperature in the server room when the computer room air conditioner (CRAC) is shut down, which can cause a rapid rise in temperature. However, it is quite difficult to predict the rack temperature accurately, which in turn makes it difficult to determine the impact on service in advance. In this research, we propose a model that predicts the rack intake temperature after the CRAC is shut down. Specifically, we use machine learning to construct a gradient boosting decision tree mo... [more]

This research attempts to evaluate the impact of renewable electricity generation mix on economic growth and CO2 emissions in Iran from 1980 to 2016. In this regard, by using EViews 10, the Structural Vector Autoregressive model (SVAR) is estimated by imposing the Blanchard and Quah long-run restrictions. The yearly data on real Gross Domestic Production (GDP), the share of electricity generation from renewable sources, and carbon dioxide emissions (CO2) caused by liquid, solid, and gaseous fuels were used. The positive impact of one standard deviation shock of increasing the share of renewable electricity on economic growth was confirmed by using Impulse Response Function (IRF). Contrary to the expectation, the share of renewable electricity in the energy mix is not at a desirable level to lower CO2 emissions, which partly could be explained by the dominant role of fossil fuel in Iran (as an energy-driven country). Moreover, the findings of Variance Decomposition (VD) verified the low... [more]

The main aim of the manuscript is the identification of key research problems in the field of sustainable development, in the era of implementing the Industry 4.0 concept. The manuscript presents results of the bibliometric analysis in the subject: “Sustainable Industry 4.0”. The bibliometric analysis was realized in three segments: Sustainability, Industry 4.0 and Sustainable Industry 4.0. In the analysis, the following databases were used: Web of Science (WoS), Scopus, Google Scholar. The main purpose of the analysis was to outline the dynamics of publications in the categories: citation, author, country, type document, science field, research area. The review of sources carried out in this way allowed us to identify key research areas and confirm the research thesis adopted in the manuscript. The research thesis: Sustainable Industry 4.0 allows the integration of the Industry 4.0 concept with sustainable development goals. The article is dedicated especially to scientists looking fo... [more]

Few life cycle assessments (LCAs) on willow biomass production have investigated the effects of key geographically specific parameters. This study uses a spatial LCA model for willow biomass production to determine spatially explicit greenhouse gas (GHG) emissions and energy return on investment (EROI), including land use conversion from pasture and cropland or grassland. There were negative GHG emissions on 92% of the land identified as suitable for willow biomass production, indicating this system’s potential for climate change mitigation. For willow planted on cropland or pasture, life cycle GHG emissions ranged from −53.2 to −176.9 kg CO2eq Mg-1. When willow was grown on grassland the projected decrease in soil organic carbon resulted in a slightly positive GHG balance. Changes in soil organic carbon (SOC) associated with land use change, transportation distance, and willow yield had the greatest impacts on GHG emissions. Results from the uncertainty analysis exhibited large variat... [more]

Poor economic performance has limited the diffusion of the combined cooling, heating, and power (CCHP) system. Various factors influence the economic performance of the CCHP system. To analyze the impacts of these different factors and promote the CCHP system, this study evaluated its comprehensive performance through a multi-criteria method, using an amusement park resort in Shanghai as a research case. First, three CCHP systems with different penetration rates were presented and simulated in a transient simulation model for comparison. The economic and environmental performance of these different penetration CCHP systems were evaluated based on the dynamic payback period and carbon dioxide emissions. The impacts of investment cost, energy prices, investment subsidy and a carbon tax on the economic performance of the three systems were discussed, and a sensitivity analysis was used to compare these factors. The results show that the current subsidy can reduce the economic gap between... [more]

In a combustion reaction of hydrocarbon fuel, carbon monoxide (CO) is a gas species that is closely related to air pollution generation and combustion efficiency. It has a trade-off with nitrogen oxide and increases rapidly in case of incomplete combustion or in fuel-rich (Φ > 1) environments. Therefore, it is essential to measure CO concentration in order to optimize the combustion condition. In the case of a steel annealing system, the combustion environment is maintained in a deoxidation atmosphere to prevent the formation of an oxide layer on the steel sheet surface. However, it is difficult to measure the CO concentration in a combustion furnace in real-time because of the harsh environment in the furnace. Tunable diode laser absorption spectroscopy, which has the advantages of non-invasiveness, fast response, and in situ measurement-based optical measurement, is highly attractive for measuring the concentration of a certain gas species in a combustion environment. In this study,... [more]

Global warming is intensifying worldwide, and urban heat islands are occurring as urbanization progresses. The cool roof method is one alternative for reducing the urban heat island phenomenon and lowering the heat on building roofs for a comfortable indoor environment. In this study, a cool roof evaluation was performed using an unmanned aerial vehicle (UAV) and a red, green and blue (RGB) camera instead of a laser thermometer and a thermal infrared sensor to evaluate existing cool roofs. When using a UAV, an RGB sensor is used instead of expensive infrared sensor. Various color space techniques, namely light-reflectance value, hue saturation value (HSV), hue saturation lightness, and YUV (luma component (Y) and two chrominance components, called U (blue projection) and V (red projection)) derived from RGB images, are applied to evaluate color space techniques suitable for cool roof evaluation. This case study shows the following quantitative results: among various color space techniq... [more]