Potential Energy Savings Research Articles

ENERGY EFFICIENCY EVALUATION OF WASTEWATER TREATMENT PLANTS: A METHODOLOGICAL PROPOSAL FOR ITS BENCHMARKING

To evaluate the energy performance of wastewater treatment plants (WWTPs), reliable, robust and holistic methods are needed. The data envelopment analysis (DEA) method, which allocates a flexible set of weights to input and output variables, has previously been used to benchmark the energy efficiency (EE) of WWTPs. However, this methodological approach suffers from discriminatory power, which makes it difficult to rank WWTPs and compare their performances because the EE scores are estimated under nonhomogeneous conditions. To overcome these limitations and to better understand the water-energy nexus, in this study, the EE of a sample of WWTPs was evaluated by allocating common weights to variables for all WWTPs in a DEA model (DEA-CSW). Evaluated WWTPs were shown to have a poor energetic performance, with an average EE score of 0.372. This means that WWTPs could save 62.8% of their current energy use. Potential energy savings were estimated to be 118,206,789 kWh/year, which is equivalent to 29,552 tons of CO2eq/year. Based on a DEA-CSW approach, only one WWTP was identified as energy efficient; therefore, it is the best performer among the assessed WWTPs. Significant differences in the weights allocated to energy and pollutants removed from wastewater were reported by the DEA-CSW and DEA allocating flexible weights. Hence, under the latter methodological approach, some relevant variables, from the functionality perspective of WWTPs, were ignored in the EE assessment. This study demonstrates the relevance of using suitable methods to benchmark the energy performance of WWTPs to avoid misleading conclusions therefore, avoiding misguided regulatory decisions.

Exploring energy efficiency and savings potential of a horizontal domestic drain water heat recovery system in high-rise apartment buildings

In residential buildings, domestic hot water (DHW) used for showering and handwashing produces significant amounts of hot drain water (DW), which is typically wasted. This study proposes a horizontal drain water heat recovery (DDWHR) unit to capture waste heat from DW and improve overall DHW system efficiency with the focus on thermal exchange in a compact installation suitable for high-rise apartment buildings. Experiments under different operating conditions were conducted to evaluate the DDWHR unit’s thermal performance and energy-saving potential. Results showed that the proposed DDWHR unit achieved energy efficiency of 90–95%, depending on operating conditions, due to high heat recovery rates. In the entire DHW system, the DDWHR unit demonstrated approximately 15% heating energy savings compared to conventional DHW setups. Also, nationwide adoption of the DDWHR unit in two-person apartments could reduce gas costs by about 14% annually. The findings of this study indicate that the horizontal DDWHR unit can effectively promote sustainable DHW use in high-rise residential buildings and offers a promising solution for improving energy efficiency in DHW systems.

Energy-saving and carbon reduction analysis of series/parallel combination for heat pump and chiller in a hotel building

Taiwan is known for its hot and humid climate, where buildings rely on air conditioning systems to provide comfortable conditions. Specifically in commercial buildings such as hotels, apart from being required to provide comfortable indoor conditions, they need to provide hot water 24 h for guests, leading to the common application of chiller and heat pump systems in hotels. With the rise of the Taiwanese tourism industry, many hotels have been newly built or renovated. However, during the planning and construction stages, considerations may be limited by personnel experience, operational difficulties, installation costs, or the desire to simplify operations. This often results in the separate consideration of heat pump systems and chiller systems, leading to unnecessary resource and energy waste. Therefore, this study takes place at a hotel building in Taichung located in Central Taiwan. Designing a series/parallel system between the heat pump and chiller systems. Through a control system and a real-time recording system, controllable factors were analyzed, such as system equipment supply/return water temperature, outdoor relative and enthalpy, and occupancy rate change. Additionally, energy-saving potential was evaluated from the collected data through linear regression. The results show that when the outdoor air temperature, outdoor enthalpy, and occupancy rate are low, the parallel system is more energy-efficient due to the higher energy consumption of the chiller under low load conditions, which is suitable for winter. Conversely, the series system is more energy-efficient than under hot weather and high indoor load conditions, making it suitable for use in the summer.

Energy performance evaluation of the ASHRAE Guideline 36 control and reinforcement learning–based control using field measurements

This study evaluates the energy performance of ASHRAE Guideline 36–compliant control (ASHRAE 36 control) and reinforcement learning (RL)–based control through experimental field tests and a simulation study. Three field tests were conducted at Oak Ridge National Laboratory’s commercial building test facility in Oak Ridge, Tennessee: a baseline with a baseline conventional control, a test with ASHRAE 36 control, and a test with RL-based control. The selected ASHRAE 36 controls were trim and respond control, as well as variable air volume (VAV) box control. We compared the measured supply air temperature of the rooftop unit, VAV box supply air temperature, and VAV box supply airflow rate across the three test cases. The field data indicated that ASHRAE 36 controls operated as specified by ASHRAE Guideline 36. Based on these data, ASHRAE 36 control achieved a 45 % reduction in hourly averaged HVAC energy consumption compared with the baseline, and RL-based control achieved a 66 % reduction. These potential annual energy savings were confirmed using a calibrated whole-building energy model. Compared with the baseline, ASHRAE 36 control reduced HVAC energy consumption by 42 %, and RL-based control achieved a 54 % reduction. Furthermore, RL-based control reduced total HVAC energy consumption by 21 % more than ASHRAE 36 control.

Investigating the thermal performance of a pipe-encapsulated movable PCM wall and its impact on reducing indoor heat gain during summer

The utilization of phase change materials (PCM) in building envelopes is considered to be an effective technology for reducing energy consumption during building operations. In this study, a novel approach is presented for integrating PCM into walls by encapsulating it using pipes, allowing for its mobility through the use of compressed air. Four experimentally validated thermal models, pipe-encapsulated movable PCM (PEM-PCM) wall (Model 1), wall with PCM fixed to the exterior (Model 2), wall with PCM fixed to the interior (Model 3), and wall without PCM (Model 4), were proposed to compare their energy efficiency in summer. Different upper threshold limits (Ttr,up) and lower threshold limits (Ttr,low) were employed to explore the impact of various threshold combinations control strategies on the thermal performance of the wall. The results show that the most effective operating scheme is Ttr,up of 27 °C and Ttr,low of 25 °C. In terms of long-term operation, cumulative summer indoor heat gain of Model 1 is 10.65 %, 10.85 % and 11.4% lower than that of Model 2,3 and 4. Notably, September demonstrates the greatest potential for energy savings, with Model 1 reducing the monthly cumulative indoor heat gain by 54.12% compared to Model 4.

Thermal Oxidation Degradation Characteristics and Kinetic Analysis of Waste Shell Powders for Efficient Utilization and Environmental Protection

ABSTRACT The thermal oxidation degradation and kinetic behavior of four waste shell powders: Hyriopsis cumingii, abalone, scallop, and clam were investigated. The thermal oxidation degradation process was elucidated using thermogravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and the Coats-Redfern method. This process typically occurs in four stages, with the decomposition of CaCO₃ (Stage III) being pivotal. Notably, clam and scallop powders exhibited the highest CaO yields of approximately 55.1% and 55.0%, respectively. Although abalone powder had a lower yield of 50.2%, it demonstrated the lowest activation energy of 118.08 kJ/mol in Stage III, suggesting potential energy and cost savings during CaO conversion. High-temperature calcination altered the chemical composition and microstructure of the shell powders, resulting in rough and porous CaO surfaces conducive to heavy metal ion and pollutant adsorption. The research provides a theoretical framework and experimental validation for the sustainable utilization of calcined shell powders, fostering efficient shell resource management and environmental protection.

Enhancing energy efficiency in Bangladesh’s readymade garment sector: the untapped potential of LED lighting retrofits

Purpose Previous studies emphasized the substantial energy-saving potential of light emitting diode (LED) lighting systems, especially in the clothing industry. However, the specific quantification of energy conservation potential in industrial factories, particularly in Bangladesh’s readymade garment (RMG) sector, remains unexplored. The purpose of this study is to investigate the potential energy savings and efficiency improvements of lighting systems in Bangladesh’s RMG sector using LED technology. Design/methodology/approach Understanding and optimizing energy consumption is crucial in the RMG sector because this sector contributes significantly to the country’s export earnings. For this, an RMG factory was surveyed and possible lighting system retrofitting was estimated and compared. Findings The adoption of energy-efficient lighting options, particularly LED, could decrease the current lighting energy usage from 15% to 7.5% in Bangladesh. First, this study reveals, that the reduction of annual energy consumption was determined to be 18,220 kWh due to the retrofitting of the lighting system with LED tube. Second, it conducts real-time measurements to assess the suitability of in-building lighting systems, providing insights into the current scenario. Lastly, it evaluates the economic and environmental benefits of the proposed lighting system in the RMG industries. Due to the retrofitting of the lighting system, the reduction of equivalent CO2 gas emissions was found to be 119.896 tCO2. Originality/value For the first time, this study explored the potential for enhancing energy-efficient lighting system design through retrofitting in the RMG industry, with a focus on Bangladesh. By addressing these aspects, this study aims to contribute to the advancement of energy efficiency and conservation efforts in the RMG sector, ultimately fostering sustainable industrial development in Bangladesh and beyond.

Analysis of user behavior and energy-saving potential of electric water heaters

As global energy resources get more limited and environmental problems worsen, it is crucial to enhance energy efficiency and reduce energy consumption in end-use products. This research focuses on electric water heaters, a significant household energy consumer, and collects a large amount of data through questionnaires and analyzes the current usage patterns of water heater use, as well as the impact of the users’ personal characteristics and energy-saving consciousness on usage behaviors. It also evaluates the energy-saving potential under different scenarios, considering both consumer behaviors and product efficiency levels. Results indicate that a substantial number of users still purchase high-energy-consuming water heaters and fail to adjust temperatures according to their specific needs, resulting in considerable energy waste. Electric water heaters exhibit significant potential for energy savings, with the efficiency of the product and user behaviors identified as key factors influencing overall energy consumption. The study provides important insights into the usage behavior of electric water heaters and offers actionable recommendations for manufacturers and government agencies: advocating the use of certified energy-efficient water heaters, raising public awareness of energy efficiency in appliance use, etc., which is in line with the country’s goals of energy conservation and environmental sustainability.

Hygrothermal behavior of hemp concrete and conventional concrete: a comparative analysis

This study presents an in-depth comparative analysis of the hygrothermal behavior of hemp concrete and conventional concrete, with a focus on their energy-saving potential and moisture regulation capabilities. Through detailed numerical simulations, the research examines how these two materials perform under identical climatic conditions, highlighting key differences in their ability to retain heat and manage moisture. The results reveal that hemp concrete provides up to 80% less thermal energy dissipation through building walls compared to conventional concrete, making it a far superior material for thermal insulation. In addition, hemp concrete exhibits improved moisture regulation, which not only enhances indoor comfort but also promotes healthier living environments by preventing excessive humidity. The study emphasizes hemp concrete's potential in significantly reducing energy consumption in buildings, thus promoting its application in sustainable construction. While hemp concrete lacks the mechanical strength required for load-bearing applications, its numerous environmental benefits, cost-effectiveness, and suitability for non-structural components make it an attractive choice for eco-friendly construction projects. This research also paves the way for future exploration of innovative uses for hemp-based materials in green building practices.

Approach Proposal for Energy-Efficient Retrofit of Historic Buildings with Comparative Analysis of EU Research Projects

Within the framework of the building section, the existing building stock is a research area with a high potential for energy savings, as it is a crucial energy consumption source. Studies are being carried out on many existing building stocks to prevent and reduce the increasing energy consumption and negative situations due to climate change and global warming. It is seen that parameters such as energy efficiency are considered as a whole with conservation in intervention methods, especially in European countries, since only conservation is insufficient for historical buildings, which are one of the primary sources of important existing building stock. Preserving cultural identity values and energy efficiency are the primary intervention criteria. By considering these two intervention criteria in balance and as a whole, the permanence and sustainability of the buildings for future generations is ensured. In this regard, comprehensive, large-scale, and multinational projects supported by the European Union (EU), especially in European countries, are carried out. In line with the conclusions drawn from the detailed and systematic analysis, comparison, and evaluation of the projects, the study proposed an approach and intervention model for future studies. The determined projects were examined in detail regarding purpose, scope, target, strategy, content, and project outcome outputs. Systematic inferences were made through the analysis in line with the data obtained. Comparisons and evaluations were made on approach information, objectives, analysis methods, technology and software used, active-passive and renewable energy systems, monitoring and tracking systems, and project output data obtained at the project's end to make the intervention's effects sustainable. As a result, a comprehensive approach model for energy-efficient retrofitting intervention approaches has been proposed in line with the conclusions obtained from the analysis, comparison, and evaluations of energy-efficient retrofitting of historic buildings. Thus, the approach model obtained with the study will guide the creation of intervention models for the studies to be carried out on energy-efficient retrofits in historical buildings.

Improving powertrain efficiency through torque modulation techniques in single and dual motor electric vehicles

Battery Electric Vehicles (BEVs) typically experience reduced powertrain energy efficiency under low-torque operating conditions. This issue can be mitigated by torque modulation, i.e., alternating driver torque demand between zero and an appropriate value. This paper aims to maximize the efficiency improvement of torque modulation and investigate its potential in two powertrain topologies: single and dual motor powertrains. To this end, optimal modulation strategies are proposed for both powertrains, considering overall powertrain energy losses and specific powertrain characteristics. Additionally, the adverse impact on driver comfort and powertrain durability due to the pulsating torque is examined. The results suggest that the proposed optimal modulation strategies can enhance powertrain efficiency while maintaining acceptable levels of driver comfort and powertrain durability. In addition, complementary modulation and torque distribution can be applied in the dual motor powertrain to provide further energy-saving potential and reduced impact on driver comfort.

Assessing energy efficiency and its dynamic changes in the water sector integrating heterogeneity and carbon emissions

Enhancing the energy performance of water utilities is a critical step towards achieving a net-zero carbon industry. Traditional energy performance assessments in the water industry often overlook heterogeneity among water companies and fail to account for changes in energy efficiency (EE) over time. To address these shortcomings, this research employs Stochastic Frontier Analysis (SFA) techniques to assess energy performance of two types of water companies such as Water and Sewerage Companies (WaSCs) and Water-only Companies (WoCs) within a single energy frontier model. Empirical analysis of water companies in England and Wales reveals an average EE score of 0.940 over the 2010–2020 period, suggesting a 6% energy-saving potential. English and Welsh water industry exhibited an overall 0.3% annual improvement in energy productivity change (EPC). This improvement was primarily attributed to efficiency changes (average 1.005), which offset the negative shift in technology change (average 0.998), while the scale effect remained negligible (average 1.000). WaSCs experienced a slight increase in EPC, with an average value of 1.018, indicating an improvement in energy productivity. In contrast, WoCs exhibited a decrease in EPC, with an average value of 0.989, suggesting a decline in energy productivity. These disparities were due to opposite shifts in the efficient production frontier; WaSCs had a positive shift (average 1.012), while WoCs had a negative shift (average 0.984). The study also highlights the impact of regulatory policies on energy performance. The 2009 price review involved modest improvements (average EPC = 1.013), while the 2014 price review yielded unfavorable results (average EPC = 0.993), emphasizing the need for long-term policies to facilitate sector-wide transformation towards carbon neutrality.

An analysis of the rebound impact of energy consumption and the factors that influence it in China's agricultural productivity

With China's agricultural sector being a major contributor to both the national economy and energy consumption, the rebound effect—the phenomenon where energy efficiency improvements lead to increased energy use—poses significant challenges to sustainable energy use. The motivation for this study stems from the need to understand the extent of this rebound impact and its underlying drivers, particularly in the context of China's agricultural modernization efforts. This study examines the rebound effect of energy consumption in China's agricultural productivity and the factors influencing it over the period from 1990 to 2023. Using a Generalized Method of Moments (GMM) model, this research analyzes the relationship between energy consumption, agricultural productivity, and several influencing factors, including technological innovation, rural-urban migration, and financial development. The results reveal that (1) energy efficiency improvements have led to a significant rebound effect in China's agricultural sector, limiting potential energy savings, (2) technological advancements have mitigated the rebound effect to some extent, but the effect remains substantial, (3) rural-urban migration has contributed to labor shortages, increasing mechanization and energy demand, and (4) financial development has positively influenced both agricultural productivity and energy use, exacerbating the rebound effect. The study suggests that policymakers should focus on developing stricter energy efficiency standards and promoting technological innovations that reduce energy intensity in agriculture, while also addressing labor migration challenges to curb the rebound impact and achieve more sustainable agricultural growth.

Distillation column optimization: A formal method using stage-to stage computations and distributed streams

This work addresses the complexities of optimizing the number of stages in a distillation column, which typically lead to challenging non-linear mixed-integer optimization problems. To simplify this, we employ distributed streams, thereby eliminating discrete degrees of freedom. To avoid sophisticated initialization procedures, the optimization problem is reformulated by employing a sequence of stage-to-stage calculations, each reduced to maintaining only the MESH (mass, equilibrium, summation, heat) equations for a single stage.Our numerical experiments show the efficiency and stability of solving the simplified optimization problem in various scenarios, including single and multiple distillation columns. For a single column scenario, we compare the accuracy of our optimization method with a full enumeration approach. Additionally, for a pressure swing flowsheet designed to separate an azeotropic mixture, we illustrate potential energy savings by optimizing a stage distribution versus using a predetermined stage distribution.

Optimizing Compressed Air Operations for Electrical Energy Savings: A Case Study in Pharmaceutical Packaging Manufacturing

This study in pharmaceutical packaging manufacturing focuses on improving compressed air efficiency through targeted strategies at both the source and user levels by establishing a baseline to analyze energy consumption patterns. Key measures, including minimizing air leaks, adjusting pressure, and optimizing compressor performance, aim to achieve a 20-50% increase in efficiency, thereby supporting environmental sustainability. The User Point and Source Point approaches are expected to lower Specific Power Consumption (SPC), with data collected from December 2020 to May 2022 providing insights into potential energy savings. Establishing this baseline, based on machine runtime and productivity, offers a solid foundation for evaluation. Results show a 23% reduction in compressor electricity usage and a 7-8% decrease in compressed air consumption. A structured improvement process and strong collaboration between engineering and management are essential for enhancing productivity and achieving sustainable energy efficiency in the industrial sector.

Cooling Effectiveness of the Sustainable Cooling Solution for Cattle: Case Study in Poland

Recently, the dairy sector has been ever more affected by global warming. This study aimed to test a novel conductive cooling system for cattle that was successfully implemented and evaluated under summer thermally challenging weather conditions in Poland. The system consists mainly of the chiller, tank, and chilled water-driven mattress, designed to prioritize animal well-being. The experimental evaluation was carried out on three Friesian dry cows, housed on different types of bedding—commercial water mattress, straw, and cooling water mattress—and supplied with water at 10 °C (day) and 16 °C (night). The cooling water mattress’ surface temperature was twice as low as that of the commercial water mattress. The animal’s thermal comfort was assessed with physiological and behavioral reactions. The cooling effect on animals’ bodies was demonstrated with a lower reticulorumen temperature of the cooled cow (p < 0.05) than the reference ones. The local effect of cooling was proved with an 8 °C-lower skin temperature after the cow’s resting period. The presented study opens a new research direction toward dairy cattle’s welfare, sustainability, and the food–energy–water nexus, based on potential energy and water savings.

A novel ventilation method: Experimental measurement and numerical simulation of vertical single-row inclined slit ventilation

Existing ventilation technologies often struggle to balance the limited airflow supply with the demands of indoor ventilation and air circulation in winter. This paper introduces a novel ventilation method, vertical single-row inclined slit ventilation (VSISV), which channels airflow through multiple inclined slits spaced at specific intervals along a vertical supply air duct. By ensuring continuity of the upstream and downstream slit jets, a continuous downward airflow is formed, enhancing both winter ventilation performance and indoor air circulation. The method was experimentally measured, with a focus on comparison to the IJV system. At the same airflow rate, it not only efficiently transports the supply air heat from the upper indoor area to the floor but also exhibits strong horizontal diffusion capability. The RNG turbulence model was selected for numerical simulation, focusing on indoor thermal comfort, air quality, and energy-saving potential. The results indicate that, at the same airflow rate, this method effectively maintains high indoor thermal comfort, directs airflow downward from the ceiling, reduces thermal stratification in the upper zone, achieves a more uniform and elevated indoor temperature, enhances indoor air quality, and demonstrates substantial energy-saving potential. This provides valuable insights for energy conservation, emission reduction, and the optimization in winter building ventilation systems.

Energy-Efficient Architectural Design of a Banquet Hall with Integrated Tunnel Ventilation: Monitoring Performance During the Transitional Season in China

The construction industry, a significant contributor to global energy consumption and greenhouse gas emissions, is under considerable pressure to adopt transformative approaches. Public buildings, which account for a substantial portion of total energy usage, must balance high standards of thermal comfort with ventilation efficiency. In China, many public buildings are part of urban landscapes, where façade designs often limit natural ventilation. Consequently, technologies like earth-to-air heat exchangers and wind towers are increasingly essential for enhancing natural ventilation. However, research on the efficacy of these systems remains sparse. This study examines the transitional seasonal environment by evaluating the thermal-humidity index of a banquet hall equipped with an earth-to-air heat exchanger system. Using DeST software [DeST 2.0], the study simulates indoor natural ventilation, calculates ventilation rates, and assesses residual heat removal efficiency. The system’s performance is also modeled under various thermal design zones. Results demonstrate that under natural ventilation, the system can achieve a residual heat removal efficiency of up to 490%. Simulations across different climate zones indicate that the system performs best in regions with extreme temperature fluctuations, particularly those with hot summers and warm winters. In these areas, the system reduces the annual temperature difference by up to 56.7%, significantly improving thermal comfort and reducing dependency on air conditioning. In contrast, performance in milder regions like Kunming achieves only a 37.5% reduction in temperature difference. Overall, this study provides valuable insights into energy-efficient design strategies and thermal optimization for banquet halls, with significant potential for energy savings and enhanced occupant comfort.

Optimising Energy Efficiency in Offshore Buildings: Supporting SDG 7 - Clean and Affordable Energy

The offshore oil and gas sector faces significant challenges in reducing its carbon footprint while meeting global energy demand. Offshore structures consume up to 500 MW of energy per day. Despite the potential for 30-40% energy savings with efficiency technologies, only 25% of global platforms implement integrated energy management systems. This study aims to optimize energy efficiency in offshore structures to support SDG 7 - Affordable and Clean Energy. The study uses a multi-method approach, analyzing data from 10 offshore platforms, conducting energy modeling, and cost-benefit analysis. The results show variability in daily energy consumption (423.7 ± 32.5 MW) with key factors such as hydrocarbon production and environmental conditions. Energy efficiency technologies such as hybrid power generation systems and Integrated Energy Management Systems (SMET) show significant potential for savings. The optimization model shows a total potential energy savings of 37.2 ± 2.1%. Economic analysis using Monte Carlo simulations confirms the feasibility of investment with positive NPV for all evaluated technologies. SMET has the most favorable risk-return profile with a mean NPV of 5.8 ± 0.7 million USD. These findings provide important insights for operators and policymakers, emphasizing the importance of a holistic approach to energy management in offshore structures. Implementation of the proposed energy efficiency strategies can contribute significantly to climate change mitigation and the achievement of SDG 7.

Enhancing indoor thermal comfort prediction in tropical regions: A transfer learning strategy in West Bengal

Ensuring energy-efficient building management and sustainability necessitates precise thermal comfort prediction, a task particularly critical in tropical regions with significant energy-saving potential. This study confronts the complexities introduced by humid air conditions and escalating internal and external heat levels. The objective is to devise a sophisticated strategy for predicting indoor personal thermal comfort that enhances prediction accuracy. The proposed method extends beyond previous techniques by incorporating a comprehensive array of thermal comfort factors and their potential interdependencies, while also leveraging a transductive transfer learning strategy to circumvent data sparsity in the target domain. The experimental results indicate the presence of localized feature coupling within thermal comfort datasets, which the proposed CNN-ConvTrans model effectively processes, thereby enhancing predictive efficacy. The primary innovation of this work lies in the development of a novel transfer learning strategy that considers localized feature coupling, integrated with a deep learning model, effectively addressing issues such as class imbalance and data scarcity. This study furnishes an innovative and valuable framework for thermal comfort prediction across diverse environmental settings.