Energy Performance Research Articles

Energy performance and wind exposure of windward, lateral, and leeward high-rise photovoltaic facades

The growing demand for sustainable energy solutions leads to the integration of photovoltaic/thermal (PV/T) modules into building facades. This study evaluates and compares the energy potential, wind load, and environmental benefits of PV/T modules installed on different facades of high-rise buildings. Using advanced computational techniques, including Computational Fluid Dynamics (CFD), the wind interaction with PV/T modules on windward, lateral, and leeward facades is modeled and analyzed. Each computational process requires over two weeks to complete due to the complexity of the simulations. The results demonstrate that the leeward facade is more effective for electricity generation, while the windward and sideward facades perform better for thermal energy storage. Maximum energy outputs of 217 kW for thermal energy and 73 kW for electrical energy are recorded, depending on wind conditions. Additionally, energetic and exergetic efficiencies reach 55.2 % and 17.7 %, respectively. The study also finds that the leeward facade has the greatest impact on reducing CO2 emissions. These findings provide valuable insights into designing optimal PV/T facades for high-rise structures, expanding the range of structural designs and offering opportunities for implementing mitigation measures to enhance system durability and efficiency. The novelty of this research lies in the detailed comparative analysis of PV/T performance across multiple facades, offering a practical framework for future sustainable building designs.

Energy and Exergy Performance Analysis of Solar-Assisted Thermo-Mechanical Vapor Compression Cooling System

Air conditioning is vital for indoor comfort but traditionally relies on vapor compression systems, which raise electricity demand and carbon emissions. This study presents a novel thermo-mechanical vapor compression system that integrates an ejector with a conventional vapor compression cycle, incorporating a thermally driven second-stage compressor powered by solar energy. The goal is to reduce electricity consumption and enhance sustainability by leveraging renewable energy. A MATLAB® model was developed to analyze the energy and exergy performance using R1234yf refrigerant under steady-state conditions. This study compares four solar collectors—evacuated flat plate (EFPC), evacuated tube (ETC), basic flat plate (FPC), and compound parabolic (CPC) collectors—to identify the optimal configuration based on the collector area and costs. The results show a 31% reduction in mechanical compressor energy use and up to a 44% improvement in the coefficient of performance (COP) compared to conventional systems, with a condenser temperature of 65 °C, a thermal compression ratio of 0.8, and a heat source temperature of 150 °C. The evacuated flat plate collectors performed best, requiring 2 m2/kW of cooling capacity with a maximum exergy efficiency of 15% at 170 °C, while compound parabolic collectors offered the lowest initial costs. Overall, the proposed system shows significant potential for reducing energy costs and carbon emissions, particularly in hot climates.

Introducing the concept of acoustic personalised environmental control systems (Acoustic PECS) within the framework of IEA EBC Annex 87

The availability of systems that can locally adjust environmental parameters holds the potential to enhance building occupant satisfaction by considering individual sensitivities, expectations, and needs. To this aim, Personalised Environmental Control Systems (PECS) are being studied as solutions that can provide individually controlled environments in the immediate surroundings of an occupant, without affecting directly the entire space and other occupants' environment. The concept has been primarily developed to address individual control of the thermal environment and perceived air quality, as in chairs with heating/cooling functions and desks equipped with personalized ventilation systems. By extending the concept of PECS to the acoustic domain, a framework on Acoustic PECS is here introduced and exemplified. The study builds on ongoing research within the IEA EBC - Annex 87, dedicated to investigating the Energy and Indoor Environmental Quality Performance of Personalised Environmental Control Systems.

Comparative and optimal study of energy, exergy, and exergoeconomic performance in supercritical CO2 recompression combined cycles with organic rankine, trans-critical CO2, and kalina cycle

The bottom cycle in supercritical carbon dioxide (sCO2) recompression Brayton combined cycle (RCBC) effectively recovers substantial waste heat for electricity generation, enhancing energy utilization. The recovery efficiency is significantly influenced by the bottom cycle configurations and specific working conditions. Besides, implementing these bottom cycles introduces challenges related to increased system dimensions and design complexity. The present study aims to understand and evaluate the characteristics and optimal trade-offs of various bottom cycles, including trans-critical, subcritical, and non-azeotropic mixed working fluids, by establishing 3E (energy, exergy and Exergoeconomic) models for sCO2/tCO2, sCO2/ORC, and sCO2/KC combined cycle systems. To analysis and enhance interpretability, statistical Global Sensitivity Analysis (GSA) alongside unsupervised learning-based Self-Organizing Map (SOM) techniques and parametric analysis are employed. These methods identify key parameters and discern system patterns. Subsequently, the Non-Dominated Sorting Whale Optimization Algorithm (NSWOA) and entropy weight-based Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) are applied to establish a Pareto-optimal decision space and identify compromised ideal design points for each combined cycle. The results quantitatively rank sensitivity for objective variables within the design space in different combined cycles and visually represent system nonlinearity and coupling relationships in 2D weight planes using SOM. The TOPSIS trade-off points based on the Pareto frontier for the three combined cycles are ηth = 45.08 %, cp,tot = 8.5199 $/GJ, ηth = 45.13 %, cp,tot = 8.3739 $/GJ, and ηth = 48.97 %, cp,tot = 8.4783 $/GJ, respectively. Integrating machine learning techniques provides a comprehensive understanding of system patterns, offering valuable insights for decision-makers in the design and optimization of combined cogeneration cycles.

Numerical simulation of a fractional Davey–Stewartson model via a conservative scheme: preservation of mass, energy and momenta

In the present manuscript, we depart from a two-dimensional form of the nonlinear Davey–Stewartson system from fluid dynamics, consisting of two partial differential equations with two unknown functions, one of them is complex-valued and the other real-valued. This model possesses four conserved quantities, namely, the mass, the energy and two momenta. In a first stage, the mathematical model is generalized to the fractional scenario considering Riesz fractional operators and three different orders. We prove mathematically that this system also possesses four quantities that are preserved in time, and which are fractional extensions of the classical mass, energy and momentum operators. Motivated by this fact, we introduce a numerical scheme for the mathematical model by making use of fractional-order centred differences. By using similar arguments as in the analysis of the continuous system, we propose some discretizations of the mass, the energy and the momenta, and we proved theoretically that these quantities are also conserved in the discrete case. In our theoretical analysis, we establish mathematically the properties of consistency for the mathematical model as well as for the discrete conserved quantities. Computationally, the finite-difference scheme is implemented using a fixed-point algorithm. Various computer simulations are performed to illustrate the conservation of the discrete quantities. Finally, we provide some interesting perspectives of research at the end of this work. This report is the first work in which a conservative finite-difference scheme for the Davey–Stewartson system is designed and rigorously analysed for the conservation properties, for both the integer-order and fractional cases.

Dynamic characteristics and energy performance of a magnetically induced multi-array piezoelectric energy harvester with asymmetric potential wells

Dynamic characteristics and energy performance of a magnetically induced multi-array piezoelectric energy harvester with asymmetric potential wells

Assessing the reliability of a ship energy performance simulation tool through on-board data

To mitigate the environmental impact of shipping on climate change, it is nowadays urgent to explore energy efficiency and cost-effective measures by means of reliable digital tools. These are becoming essential for assisting the design of new ships and the refurbishment of the existing ones, as well as for assessing and optimizing the energy performance of a ship during its entire life-cycle. This paper focuses on the verification of the reliability of a novel ship energy dynamic simulation tool, developed for the calculation of the energy, economic, and environmental performance of large ships, the design and optimization of energy system layouts and operational logics, as well as the definition of design and management guidelines for ships. The reliability of the developed model was verified through the use of data measured onboard an existing sample cruise ship. The verification procedure is conducted for assessing the reliability and for exploiting the potentiality of dynamic analysis for a more precise evaluation of ships energy loads, temperature levels, and necessary sizes of possible saving technologies. The validated tool will enable reaching two different goals: i) to evaluate different energy system layouts and to define the optimal one for achieving the present imposed targets and constraints, ii) to obtain a large amount of data for allowing the implementation of the digital twin approach in the maritime sector. The model validation was successfully achieved and very low or negligible deviations, lower than 4%, of numerical data vs. measurements were observed. Through the validated simulation tool approximately 23.4 GWh of primary energy from polluting fuels over two weeks is computed. In addition, the model provided insights into the flow rate, temperature levels, and energy flows of the ship energy system, necessary for identifying the amount of thermal energy to be recovered as well as potential solutions to enhance the energy efficiency of the entire system.

OPTIMIZING ENERGY EFFICIENCY: A COMPREHENSIVE ANALYSIS OF BUILDING DESIGN PARAMETERS

This study explores the critical role of financial incentives, energy performance certifications, government policies, and advanced technologies in driving the adoption of energy-efficient building practices. Financial incentives, such as tax credits, rebates, and grants, are shown to significantly reduce the upfront costs associated with energy-efficient technologies, making these innovations more accessible to developers and building owners. The research highlights the effectiveness of energy performance certifications, like LEED and Energy Star, in enhancing the market value and energy performance of buildings by providing a structured framework for evaluating sustainability. Government policies and building codes, including the International Energy Conservation Code (IECC) and ASHRAE standards, are identified as key drivers of energy efficiency, compelling developers to meet stringent performance standards. Additionally, the integration of renewable energy technologies, such as solar panels and geothermal heat pumps, alongside smart building automation systems, plays a vital role in reducing energy consumption and improving operational efficiency. However, regional disparities in the availability of financial incentives and enforcement of policies present challenges to widespread adoption. The study concludes that expanding financial support, strengthening policy enforcement, and increasing public and industry awareness of the long-term financial and environmental benefits of energy-efficient buildings are essential for accelerating the transition to sustainable building practices. By addressing these challenges, the construction industry can make significant strides toward reducing energy consumption, lowering greenhouse gas emissions, and achieving global sustainability goals.

Integrating sustainable finance into energy policies: A comprehensive study on the influence of green investments on energy performance in OECD nations

Integrating sustainable finance into energy policies: A comprehensive study on the influence of green investments on energy performance in <scp>OECD</scp> nations

Effect of age hardening precipitates on the corrosion performance of laser Powder-Directed energy deposited CuNi2SiCr

This study explores Laser Powder − Direct Energy Deposition (LP-DED) processing of CuNi2SiCr and the effect of heat treatment on corrosion behavior. The findings pave the way to increasing the life of the components and the possibility of refabrication upon failure. LP-DED manufactured CuNi2SiCr was subjected to solution treatment followed by age-hardening at 500℃ for 1,3,5 and 7 h. The microstructure analysis showed the formation of Cr3Ni precipitates due to a higher cooling rate in the LP-DED process. Upon aging, Ni3Si, Ni2Si, and CrSi2 precipitates evolved. Due to the Orowan phenomenon, microhardness increases with the aging time as the number of precipitates along the grain boundary increases with the aging time. The 5-hour aged sample exhibited the best corrosion resistance due to precipitation coherency in the matrix and the medium-sized precipitates with uniform precipitation-free zones (PFZ) in the grain boundary.

Experimental study of the energy and exergy performance of a solar parabolic dish concentrator integrated with thermal energy storage

Concentrating solar power is rapidly becoming a mainstay of solar energy systems, with the parabolic dish concentrator being a common and high-performing option for medium-temperature applications. This study investigates the thermal performance of a parabolic dish concentrator integrated with phase change material based thermal energy storage. Energy and exergy efficiencies are compared for a water-based storage tank in thermosyphon circulation mode, both with and without phase change materials encapsulation. Various phase change materials capsules were strategically positioned within the tank in a certain position, which satisfies the melting temperature of the studied phase change materials. Steam generation was also measured and correlated with solar irradiation intensity. This study aims to address the changes in energy and exergy efficiencies for the system integrated with latent heat storage encapsulation. Results show the highest overall energy efficiency 46.7% was achieved with copper cylindrical capsules, while the base case without phase change materials yielded the highest overall exergy efficiency 5.23%, closely followed by the copper cylindrical capsule 4.94%. Peak energy and exergy efficiencies reached 79.37% and 11.12%, respectively. The copper cylindrical capsules provided the optimal balance between thermal and storage performance without compromising efficiency.

Pyrazine-Based Iodine-Containing Biocidal Materials: Enhanced Energy Performance and Reduced Corrosion Risk.

Biosafety is crucial to the common interests of all humanity. Currently, global biosafety governance is a challenge and poses significant opportunities. With the escalating challenges posed by microorganisms, there is an urgent need to develop advanced biocidal materials. In this work, we introduce a class of iodine-containing high-energy biocidal materials, utilizing pyrazine rings with good thermal stability as nitrogen-rich high-energy backbones, to address the issues of corrosion and hygroscopicity associated with N-H acidic protons in traditional iodine-containing azole compounds. Employing nucleophilic substitution and coupling reactions, we successfully synthesized two distinct series of eight compounds (Series A: BQDI, BQFI, BQDIO; Series B: BBQ3I, BBQ4I, BBQNI, MBQ5I, and MBQDI), which exhibit a high iodine content and enhanced detonation pressure. Notably, compounds BQDIO and BBQNI show detonation pressures of 13.70 and 16.52 GPa, respectively, both exceeding the 10 GPa of traditional iodine-containing biocidal materials. This improvement is crucial for expanding the diffusion range of biocidal substances and enhancing the biocidal efficiency of these materials. Pyrazine-based iodine-containing compounds have revolutionized the performance of biocidal materials, addressing corrosion issues and paving the way for the development of efficient, stable, and safe biocidal materials.

Analysis of the Impact of Funding Policies for the Energy Refurbishment of Buildings Using Dynamic Simulations

Dynamic simulations can accurately estimate the thermal demands for space heating and cooling in buildings, as well as the energy and economic performance of specific energy refurbishment actions. This study aims to evaluate the energy and economic savings resulting from the adoption of particular energy measures applied to a cluster of residential condominium buildings, also considering some possible Italian funding policies. To this scope, dynamic simulation models of several buildings with different features in terms of geometry, shape, and thermo-physical properties are considered. The selected buildings are representative of the most common buildings in the city of Naples, Southern Italy. Two scenarios regarding the possible penetration of the refurbishment actions are considered: the “25% scenario”, where 25% of buildings in the Naples municipality adopt the selected measures, and the “100% scenario”, where all buildings adopt such energy refurbishment actions. The results of the simulations, reported over different time periods, compare the economic, energy, and environmental benefits of the specific energy measures. This study evaluates the replacement of conventional natural gas-fired boilers with natural gas-fired condensing boilers, as well as the use of thermal insulation on the external walls of the buildings. The primary energy demand for space heating decreased by 28% when the proposed energy measures were implemented in all buildings of the Naples municipality.

A spatiotemporal analysis approach for multidimensional assessment of renewable energy development in ASEAN countries

The Association of Southeast Asian Nations (ASEAN), an integration of diverse geographies and economies, presents a unique opportunity to harness the vast potential of renewable energy. Based on panel data from 2011 to 2020, the current study employs both the entropy weight method and the system coupling method to assess the spatiotemporal performance of renewable energy development in terms of economic, social, and environmental dimensions across the entire ASEAN region. The Renewable Energy Performance (REPer) Index has been proposed to quantify development performance. The results show that the ASEAN region as a whole has improved by 19.72 % in REPer over the years, with some minor variations between member countries. Among all the member states, Malaysia had the highest REPer of 0.716 in 2020, followed by Singapore and Indonesia (0.678 and 0.497, respectively). Myanmar had the least advanced renewable energy sector, with an REPer of 0.268. These findings offer a comprehensive understanding of how renewable energy sources are distributed across ASEAN member states and how their development patterns change over time. By identifying the gaps and disparities in renewable energy development among the member states, the current study provides policy recommendations to promote better cooperation in the development of renewable energy sources.

Design and experimental characterization of a propane-based reversible dual source/sink heat pump

The current paper presents the design and energy performance analysis of a propane-based reversible Dual Source/Sink Heat Pump (DSHP). DSHPs offer an alternative to conventional water to water and air to water heat pumps, leveraging the strengths of both technologies in an efficient manner. The developed prototype incorporates an innovative Dual Source/Sink Heat eXchanger (DSHX), enabling the unit operating in various modes, including space heating, space cooling, and domestic hot water production using brine, air or both simultaneously as a source/sink. The DSHX serves as as both a condenser or an evaporator, directly rejecting or absorbing heat from air and/or brine. By eliminating secondary loops and defrost cycles, the DSHX minimizes energy losses. The main novelty of this work lies in the DSHX that integrates external units typically duplicated in DSHPs into a single component, eliminating the need for split refrigerant flow rates, thus avoiding maldistribution, refrigerant charge increase and draining valves. A steady state experimental campaign was conducted in a climatic chamber to characterize the DSHP prototype and validate the DSHX performance models. Heating capacity up to 11.2 kW and COP values up to 4.7 were achieved at nominal compressor speed by supplying hot water at 35 °C with an ambient temperature of 7 °C. Similarly, when producing cold water at 7 °C, cooling capacity and EER reached 9.8 kW and 3.6, respectively, at nominal compressor speed using air as heat sink at 35 °C. The effects of various operating parameters on the overall coefficient of performance and heat duty in both heating and cooling modes, considering air or brine as heat source/sink are analyzed in detail. Results demonstrate enhancements of approximately 15 % in capacity and efficiency compared to earlier work. Moreover, four deterministic models were created in order to predict the behaviour of the DSHX and validated against experimental results, reaching deviation values below 15 %.

Building shape optimization based on interconnected embodied and operational energy and carbon impacts

Strategic building design decisions informed by a comprehensive life cycle impact assessment hold substantial potential in addressing global energy consumption and carbon emissions, with buildings accounting for 40% of energy consumption and 37% of emissions. While building operational energy (OE) has traditionally received greater attention, the dynamic trade-offs between OE and embodied energy (EE) in building design are often overlooked. Design decisions, such material selection and building shape, can present conflicting considerations between OE and EE. Addressing these impacts in isolation may fail to achieve comprehensive reductions in energy consumption and carbon emissions. This study highlights the necessity of a holistic approach to design decisions such as building shape and material selection, emphasizing the importance of considering both OE and EE simultaneously. Our literature review confirms a gap in studies that consider these factors together in the context of building shape optimization. To analyze the interconnectivity of building shape design, material choice, and the trade-offs between OE and EE, we devised two parametric test cases with identical features but using two different insulation materials: hemp-based and glass wool. The analysis allows us to (1) evaluate the impact of integrating total lifecycle impact on building shape design optimization, in comparison to designs that focus solely on OE; (2) assess how the selection of materials, specifically hemp-based versus glass wool insulation, influences optimized building shape and carbon emissions reduction; and explore the benefits of bio-based materials by analyzing performance variations in the two insulations case studies. Our findings reveal that although OE typically has a larger impact over a building’s lifetime, the optimal building shape can still vary significantly based on the EE contribution. The benefit of bio-based material is context-dependent, varying with factors such as the building shape discussed in this paper, as well as other factors such as climate. In our test cases, we observed that shape variations resulted in up to a 17.9% change in OE due to different building shapes, and a 60.7% variation in the envelope’s surface area, while the building area remained unchanged. This expanded understanding will facilitate more informed and sustainable decision-making in the construction and design industries, addressing the often-overlooked interconnectivity of OE and EE.

Energy and exergy performances of low-density polyethylene plastic particles assisted by microwave heating.

Plastic waste can exist naturally for hundreds of thousands of years and harm humans, animals, and the environment. In this study, the energy and exergy performances (absorbed energy, energy efficiency, absorbed exergy, and exergy efficiency) of LDPE (low-density polyethylene) plastic particles assisted by microwave heating based on the experimental data as affected by microwave power, feeding load, and chamber volume were evaluated and analyzed. The results showed that as the microwave power raised from 500 to 900 W, the feeding load changed from 10 to 30g, and the chamber volume decreased from 200 to 100ml, (a) the absorbed energy at the heating time of 60min increased from 19.73kJ, 5.84kJ, and 22.71kJ to 37.69kJ; (b) the energy efficiency for the whole heating process increased from 1.10%, 0.32%, and 1.26% to 2.09%; (c) the absorbed exergy at the heating time of 60min increased from 0.308, 0.091, and 0.091 to 0.724kJ; and (d) the exergy efficiency for the whole heating process increased from 0.017, 0.005, and 0.023 to 0.040%, respectively.

Numerical and experimental investigation of Tesla micromixers with different three-dimensional herringbone structures

Laminar flow within channels at the micro- or nano-scale of the microfluidic device restricts the rapid mixing of different fluids, leading to reduced reaction velocity. In this study, different three-dimensional herringbone structures were designed to the Tesla micromixers to enhance transverse flow and vortex flow in the channels. Computational fluid dynamics (CFD) simulation results indicated that the sunken herringbone structure provided the most significant enhancement in mixing. The raised herringbone structure exhibited the best energy performance. When Reynolds number (Re) exceeded 60, the mixing indexes (MI) of the Tesla micromixers were over 90%. The improvement in mixing efficiency by both herringbone structures compensated for the weak mixing performance of the Tesla structure at lower Reynolds numbers (Re=0.2-30). Additionally, the mixing experimental results verified the accuracy of the simulation results. This study could provide guidance for improving the mixing performance of micromixers over a wide range of Reynolds numbers (Re=0-100).

High-fidelity model development of CO2 booster refrigeration systems in supermarkets using field measurements

Supermarket refrigeration systems adopting traditional refrigerants with high global warming potential (GWP) have impacts on global warming for indirect and direct greenhouse gases (GHG) emissions. CO2 is a popular low-GWP alternative. The transcritical operation of CO2 systems worsens their energy performance, but provides recoverable heat as a heat source to reduce gas consumption. To evaluate operation performance, data-driven models, trained by historical data, are weak in implementation with datasets outside the scope of training data; in contrast, theoretical models have better extrapolation ability to calculate all operation conditions of CO2 systems at supermarket. Existing theoretical modeling approaches often lack validation against the limited public-access data, which reduces model reliability for further applications, and adopt oversimplified inference methods for unmeasured variables, which increases the risks of breaking thermodynamic laws and lowering model accuracy. This study therefore develops a steady-state theoretical model for CO2 booster refrigeration systems validated against field measurements from three UK supermarkets. The available measurements are utilized to the best level to ensure model accuracy and physical interpretability. Proposed methods to infer missing variables in CO2 systems include condenser outlet temperature, evaporating temperature, compressor isentropic efficiency and compressor mass flow rate. Results show that proposed inference methods enhance the abilities of the proposed modelling approach to ensure data integrity, avoid breaking thermodynamic laws, and improve model accuracy by reflecting real-time actual values of unmeasured variables rather than rough assumptions. The proposed modeling approach provides satisfactory accuracy validated using high-resolution measurements across the whole year from three real supermarkets.

Investigating energy performance of build-to-rent buildings in england

The domestic sector made up 16% of UK’s total greenhouse gas emissions in 2021. The build-to-rent market is experiencing a rapid expansion, but the energy performance and distinctiveness of this building sector are still generally undiscovered. Therefore, 423 build-to-rent flats from three build-to-rent developments in England were evaluated with top-down approach. Energy use intensities of flats were compared against domestic energy benchmarks and design targets. Possible determinants of energy consumption in build-to-rent flats, including EPC rating, number of bedrooms, air permeability, glazing area and glazing orientation were investigated through correlation analyses. Research discovers discrepancy between actual energy performance of the studied flats and design targets supporting UK’s 2050 net zero target. In this case study, number of bedrooms is identified as the most noticeable factor influencing energy consumption. Results of this study provide an introductory insight of the build-to-rent sector and serve as a starting point to encourage further exploration. Practical application This paper specifically focuses on build-to-rent buildings within the domestic sector. Energy use situations of build-to-rent flats in the UK were investigated with actual measured data provided by a build-to-rent developer. Results demonstrate the discrepancy between energy use in the build-to-rent flats being studied and existing domestic benchmarks. This paper provides insights to researchers, building developers and policymakers regarding the energy performance of this upsurging build-to-rent building sector and its associated influencing factors. It also contributes ideas on the importance of data sharing and development of energy benchmarking of the build-to-rent sector.