Of the various waste and side streams created in a kraft pulp mill, the biological sludges from the wastewater treatment plant are some of the most problematic to handle. Incineration is becoming a common solution as landfilling is no longer permitted by legislation in many countries, but this is also problematic due to the high moisture content, poor drying characteristics, and high ash content in the solids. This study evaluates the technical potential of mild hydrothermal carbonization (HTC) at 160 °C for 3 h to improve the energy efficiency of on-site incineration as a biosludge handling method. HTC treatment transforms wet organic substrates into a hydrophobic carbonaceous material (hydrochar). The heating value and elemental composition of both the sludge and the hydrochar product were analyzed. Based on this, a hydrothermal carbonization model developed earlier was adjusted for the feedstock, and process integration modelling performed to evaluate the performance impact on the p... [more]

The main objective of this research is to assess the impact of energy certificate ratings (EPCs) on the value per m2 of Portuguese housing sales. Data from 289 Portuguese municipalities between 2014 and 2019, analysed with a fixed effects panel and method of moments quantile regression, were used. EPCs with high energy efficiency ratings (e.g., A+, A, B, and B-) are used as a proxy for dwellings with “green” or “environmentally friendly” certificates. On the other hand, ratings with a low energy efficiency (e.g., C, D, E, and F) are used as a proxy for dwellings with “non-green” or “not environmentally friendly” certificates. The results support that EPCs associated with green housing increase the value per m2 of housing sales, and those associated with non-green housing decrease the sales value. It was also found that municipal GDP, tax/financial incentive policies for energy efficiency, and the number of completed dwellings in new constructions for family housing will increase sales... [more]

As Korea has declared to realize a net-zero emission by 2050 in the Paris Agreement, the country has begun to implement national energy efficiency policies through the Green Standard for Energy and Environmental Design (G-SEED) certification and revision of building insulation thickness standard. However, some studies have reported the ineffectiveness of G-SEED certification and insulation thickness standard in reducing the energy consumption in certain buildings. Therefore, this study investigated the effectiveness of G-SEED certification and the revision of buildings’ insulation thickness standard, and evaluated the energy consumption of courthouse buildings. In addition, this study investigated the total annual energy consumption (electricity, gas, and heating energy) per gross floor area of courthouse buildings located in the central and southern regions of South Korea. Although many studies about the energy consumption analysis of non-residential buildings have been performed prev... [more]

The use an inverter is one of the representative ways to utilize regenerative braking energy in railway systems. Due to the nature of urban railways that generate a large amount of regenerative energy, the economic advantages are clear. However, in the case of the existing inverter operation method, a method of operating the inverter using the threshold voltage is used, which has a disadvantage in that power cannot be utilized between the no-load voltage and the threshold voltage. Therefore, in this paper, we propose an optimal location selection method and capacity calculation method for installing a regenerative inverter in an urban rail system, and a control method according to the train brake position to increase the regenerative energy utilization rate. First, the inverter capacity and location were selected by selecting the maximum regenerative energy generation for each substation section through the train performance simulation (TPS) based DC power simulation (DCPS). An inverte... [more]

One of the biggest challenges of a modern enterprise is finding a balance between achieving environmental goals and being competitive in the era of Industry 4.0 requirements. The digital revolution is forcing companies to overcome various challenges that contribute to reducing energy consumption. Micro and small enterprises carry out activities in the field of energy efficiency by implementing measures to save energy and reduce total energy consumption. However, these activities are limited by many barriers to resources, which means that these activities are much smaller than those in large companies. The purpose of this study was to assess the performance of micro and small enterprises following environmental objectives in improving energy efficiency. The research study, based on a structured and standardized survey questionnaire, was conducted with the use of the CATI technique between April and May 2022 among the owners of micro and small enterprises operating in Poland. The study s... [more]

Even if flat glass is 100% recyclable, only 1% is currently handled in circular or closed-loop supply chains (CLSCs) in Sweden. This has an unnecessary environmental impact, indicating not only the potential for more energy-efficient solutions but also the challenges that need to be understood. The purpose of this article is to increase the knowledge of challenges in applying different types of more or less energy-efficient CLSCs for flat glass. Through a literature review, an overview of CLSC types, together with challenges in different areas, is provided. The CLSC types and challenges are corroborated in a flat glass context, including focus groups and expert interviews. Four CLSC types—two CLSCs based on remanufacturing, one on reconditioning, and one on reuse—are identified. A framework provides implications for both literature and practice. It contains 19 challenges—such as lack of large-scale actors, lack of material knowledge, lack of knowledge of customers’ behavior, lack of pr... [more]

In this paper, a first- and second-law analysis of vapor compression refrigeration is presented to estimate and propose the replacement of R134 with working fluids having less global warming potential (GWP) and less exergy destruction and irreversibilities. Six different refrigerants were studied, namely, R717, R1234yf, R290, R134a, R600a, and R152a. A thermodynamic model was designed on Engineering Equation Solver (EES) software, and performance parameters were calculated. The model was deployed on all six refrigerants, while the used output parameters of performance were cooling capacity, coefficient of performance, discharge temperature, total exergy destruction, relative exergy destruction rates of different components, second-law efficiency, and efficiency defect of each component. The performance parameters were estimated at different speeds of the compressor (1000, 2000, and 3000 rpm) and fixed condenser and evaporator temperatures of 50 °C and 5 °C, respectively. The isentropic... [more]

The aim of this paper was to examine whether the COVID-19 epidemic has slowed the fulfilment of one of the core tasks of the energy sector “Ensure Access to Affordable, Reliable, Sustainable and Modern Energy for All” (SDG7) taking into account corporate social responsibility. Four research questions and hypotheses were posed, relating to the perspectives of local authorities, the activities of large energy companies, the impact of the epidemic on the implementation of the SDG7 and, in addition, to the understanding of CSR principles from the point of view of ordinary entrepreneurs. A qualitative descriptive analysis based on two reliable databases and a survey procedure (Question 4) was used to answer the research questions posed. The goal was achieved by positively confirming three hypotheses and testing one negatively, relating to COVID-19’s slowing role in SDG7 implementation. The analysis showed that the 2020−2021 epidemic in Poland has led to more initiatives in this area, contra... [more]

Smart grid plays a vital role in energy management systems. It helps to mitigate the demand side management of electricity by managing the microgrid. In the modern era, the concept of hybrid microgrids emerged which helps the smart grid management of electricity. Additionally, the Internet of Things (IoT) technology is used to integrate the hybrid microgrid. Thus, various policies and topologies are employed to perform the task meticulously. Pakistan being an energy deficient country has recently introduced some new policies such as Energy Wheeling Policy (EWP), Energy Import Policy (EIP), and Net Metering/Distributed Generation Policy (NMP) to manage the electricity demand effectively. In addition, the Energy Efficiency and Conservation Act (EECA) has also been introduced. In this paper, we present the overview and impact of these policies in the context of the local energy market and modern information and communication mechanisms proposed for smart grids. These new policies primaril... [more]

Over the last few decades, energy efficiency has received increasing attention from the Architecture, Engineering, Construction and Operation (AECO) industry. Digital Twins have the potential to advance the Operation and Maintenance (O&M) phase in different application fields. With the increasing industry interest, there is a need to review the current status of research developments in Digital Twins for building energy efficiency. This paper aims to provide a comprehensive review of the applications of digital twins for building energy efficiency, analyze research trends and identify research gaps and potential future research directions. In this review, Sustainability and Energy and Buildings are among the most frequently cited sources of publications. Literature reviewed was classified into four different topics: topic 1. Optimization design; topic 2. Occupants’ comfort; topic 3. Building operation and maintenance; and topic 4. Energy consumption simulation.

This paper discusses fuel cell electric vehicles and, more specifically, the challenges and development of hydrogen-fueled buses for people accessing this transportation in cities and urban environments. The study reveals the main innovations and challenges in the field of hydrogen bus deployment, and identifies the most common approaches and errors in this area by extracting and critically appraising data from sources important to the energy perspective. Three aspects of the development and horizons of fuel cell electric buses are reviewed, namely energy consumption, energy efficiency, and energy production. The first is associated with the need to ensure a useful and sustainable climate-neutral public transport. Herewith, the properties of the hydrogen supply of electric buses and their benefits over gasoline, gas, and battery vehicles are discussed. The efficiency issue is related to the ratio of consumed and produced fuel in view of energy losses. Four types of engines−gasoline, di... [more]

The quality of human nutrition has acquired significant improvements thanks to the opportunity to store food in suitable temperature conditions. Refrigeration has allowed the slowing of chemical and biological degradation and hence the waste of foodstuff, but at the same time increases energy consumption. These effects impact the environment and the sustainability performance of the cold chain, and drive consumers’ choices. The stakeholders of the chain are, therefore, constantly looking for improvement actions to reduce environmental impacts. This paper aims to provide a methodology for prioritizing and assessing the energy efficiency measures for cold chains in terms of quality losses and specific energy consumption, distinguishing between technological, maintenance, and managerial opportunities. This analysis is based on the cold supply chain tool, developed under the H2020 project ICCEE (“Improving Cold Chain Energy Efficiency”) which focuses on a holistic approach, not looking onl... [more]

In the slider-crank mechanism, where the rotational motion is transformed into the translational motion, the input torque is highly variable due to the inertial effect. The consequence of fluctuating torque is that it causes the load upon the prime mover to be inconsistent, which might likely results in higher stresses in the components, higher joint friction, and the necessity for higher driving power. In this paper, a technique of reduction of the dynamic torque and joint forces in the slider-crank mechanism using mechanical resonance is described. A comparative result of the conventional system in the process of gas compression, as a practical application example, is presented. The result shows that the utilization of resonance has the advantage of providing lower dynamic torque and rotating joint forces compared to the conventional operation. Since the compression of the air itself takes effect as a spring compression, in the gas compression process, the narrow torque and force reg... [more]

To date, along with the rapid development of urban rail transit (URT) in China, the evaluation of operational efficiency and energy efficiency has become one of the most important topics. However, the extant literature regarding the efficiency of URT at the line level and considering carbon emissions is limited. To fill the gap, an evaluation model based on slacks-based measure (SBM) data envelopment analysis (DEA) is proposed to measure the efficiencies, which is applied to 61 URT lines in China’s four megacities. The findings are summarized as follows: (1) The average operational efficiency and energy efficiency of URT lines are low, and both have great room for improvement. (2) There are significant disparities in the efficiency of URT lines in the case cities. For instance, the average operational efficiency of URT lines in Guangzhou is higher than that of other cities, while the average energy efficiency of URT lines in Shanghai is higher than that of other cities. (3) The URT lin... [more]

The quality of the housing environment (HE) is an important issue that has a direct impact on the life of inhabitants. Aiming for quality in residential architecture begins with a well-designed HE, with the designing process being a value that is difficult to evaluate. Nowadays, a well-designed HE takes into account the energy efficiency of a building. An appropriate degree of thermal comfort, which is required by inhabitants, needs to be considered at the design stage. Designers can use building certification programs and multi-criteria analysis to motivate investors to construct buildings in accordance with energy efficiency requirements. These systems respond to the needs of energy efficiency, thermal comfort, sustainable heating, and ventilation. Defining ways and methods to evaluate quality in architectural projects will allow the value of the HE to be improved. For this purpose, a multi-criteria analysis of five systems that can be used to evaluate HE quality and energy efficienc... [more]

The article deals with the impacts of economic, ecological, and social development scenarios in ensuring sustainable energy development. EU countries were the statistical bases of the study; the assessment period was from 2000 to 2019. The information bases of the research were the World Bank, the Organization for Economic Cooperation and Development, and the European Commission data. Based on the generalized method of moments, the authors investigated the dependence of energy consumption on economic, environmental, and social development factors. The results confirm the positive relationship between renewable energy consumption and GDP per capita, foreign direct investment, and energy depletion. A negative relationship between the consumption of renewable energy, CO2 emissions, and domestic gas emissions was proved. Based on intelligent data analysis methods (methods involving one-dimensional branching CART and agglomeration), countries were clustered depending on the nature of the en... [more]

Market-based instruments such as white certificates offer the potential to increase efficiency gains, reduce primary energy consumption and make energy systems more resilient. The purpose of this paper is to provide insights into the white certificate scheme through a case study analysis. In light of increasing decarbonization and energy efficiency targets, it is important to rethink the role that policy instruments play in the energy transition, including the energy efficiency obligation schemes within which white certificate schemes fall. We focus on Italy’s white certificate scheme because it is among the longest-lived and has achieved notable results. The scheme is characterized by annually increasing energy savings targets, flexibility, the opportunity to include many interventions, and the role of energy services companies. We provide evidence based on an empirical survey and fill the research gap left by the latest updates to the scheme along with an appraisal of those updates,... [more]

Irradiance variability is one of the main challenges for using photovoltaic energy. This variability affects the operation of maximum power point trackers (MPPT) causing energy losses. The logic of the Perturb-and-Observe MPPT algorithm is particularly sensitive to quick irradiance changes. We quantified the existing relation between irradiance variations and efficiency loss of the logic of the Perturb-and-Observe MPPT algorithm, along with the sensitivity of the MPPT to its control parameters. If the algorithm parameters are not tuned properly, its efficiency will drop to nearly 2%. Irradiance variability causes a systematic energy loss of the algorithm that can only be quantified by ignoring the hardware components. With this, we aim to improve the energy yield estimation by providing an additional efficiency loss to be considered in the calculations.

Energy renovations of the building stock are a paramount objective of the European Union (EU) to combat climate change. A tool for renovation progress monitoring is energy performance certificate (EPC) labelling. The present study tested the effect of different EPC label classifications on a national database, which comprises ~25,000 EPC values from apartment buildings, detached houses, office buildings, and educational, commercial, and service buildings. Analysing the EPC classes labelling resulting from four different EU methods, we estimated the annual renovation rates, costs, energy savings, and CO2 emissions reduction that would affect the national building stock if each of them was adopted, to fulfil the European Climate Target Plan by the year 2033. The ISO 52003-1:2017 two-point and one-point methods determined a very uneven distribution of renovation rates, from 0.45% to ~9%. Conversely, the Directive 15% recently proposed in COM/2021/802 with uniform rates determined smaller... [more]

For decision-making and governance, smart cities depend on tracking data collected via a substantial percentage of wireless sensing nodes. However, several limitations affect Wireless Sensor Network (WSN)-based Internet of Things (IoT) services, such as low battery life, recurrent connectivity problems due to multi-hop connections, and a limited channel capacity. Furthermore, in many systems, clustering and routing are handled independently, which prevents the adaptation of effective strategies for optimal energy usage and prolonged network lifespan. This research gathers data from heterogeneous IoT nodes linked via WSN and distributed across a smart infrastructure. There are two interrelated problems to be addressed with respect to energy efficiency computations: clustering and routing. We provide a new clustering strategy through which efficient routing of critical and regular data is handled. As a result, both clustering and routing have been significantly strengthened, which balanc... [more]

The Architecture, Engineering and Construction (AEC) industry has been utilizing Decision Support Systems (DSSs) for a long time to support energy efficiency improvements in the different phases of a building’s life cycle. In this context, there has been a need for a proper means of exchanging and managing of different kinds of data (e.g., geospatial data, sensor data, 2D/3D models data, material data, schedules, regulatory, financial data) by different kinds of stakeholders and end users, i.e., planners, architects, engineers, property owners and managers. DSSs are used to support various processes inherent in the various building life cycle phases including planning, design, construction, operation and maintenance, retrofitting and demolishing. Such tools are in some cases based on established technologies such Building Information Models, Big Data analysis and other more advanced approaches, including Internet of Things applications and semantic web technologies. In this framework,... [more]

Malaysia’s energy intensity (GWh/GDP) shows an increasing trend since the 1990s, leading to the government’s efforts to promote energy efficiency via policies such as the National Energy Efficiency Action Plan (NEEAP), which includes the Energy Performance Contracting (EPC) initiative. This paper reviews recent publications in industrial Combined Heat and Power (CHP) with a focus on international case studies relevant to Malaysian industries that use industrial steam and highlights trends within the research area. It also provides the basis for more case studies to be performed in the Malaysian industry to improve energy efficiency while also supporting further academic research in the area. Additionally, the paper documents the importance of data collection and analysis as well as demand forecasting, not only for a better understanding of industrial energy systems but also to increase profitability since system loads may vary throughout a typical year. A multi-criteria and comprehensi... [more]

For heritage buildings, energy-efficient retrofitting cannot be applied with the same range of possibilities as with existing buildings. Applying such improvements to heritage buildings can be challenging due to their historic and/or cultural significance and non-standard construction methods. This paper reviews the technical challenges and potential of applying energy efficient retrofit elements in heritage buildings. The retrofitting measures reviewed are draught-proofing, windows, insulation, ventilation, heating, solar photovoltaics and phase change materials. It is possible to significantly reduce energy use in heritage buildings with such retrofits. However, there is no universal way to apply energy-efficient retrofitting in heritage buildings, which is apparent in the literature, where case studies are prevalent.

This work focuses on the geometry effects over the performance of oscillating water column (OWC)-type wave energy converter (WEC) systems and searches for the OWC geometries that enhance the energy efficiencies under the same wave conditions. To analyze the hydrodynamic performances of the WEC systems, an in-house smoothed particle hydrodynamics (SPH) code based on weakly compressible fluid approach is utilized. The energy efficiency enhancement studies of the determined OWC device are carried out with a two-step geometry modification procedure. The first step starts with the validation of the free-surface elevation and orbital velocity time histories. Then, a three-by-three simulation matrix that depends on the geometrical design parameters of chamber length and front wall draft is run at three different wave conditions, and the OWC geometry that produces the maximum energy efficiency is determined. In the second step, the corner regions of the obtained optimal geometry are chamfered,... [more]

Edge devices and their associated computing techniques require energy efficiency to improve sustainability over time. The operating edge devices are timed to swap between different states to achieve stabilized energy efficiency. This article introduces a Cognitive Energy Management Scheme (CEMS) by considering the offloading and computational states for energy efficacy. The proposed scheme employs state learning for swapping the computing intervals for scheduling or offloading depending on the load. The edge devices are distributed at the time of scheduling and organized for first come, first serve for offloading features. In state learning, the reward is allocated for successful scheduling over offloading to prevent device exhaustion. The computation is therefore swapped for energy-reserved scheduling or offloading based on the previous computed reward. This cognitive management induces device allocation based on energy availability and computing time to prevent energy convergence. Co... [more]