Energy Analysis Framework Research Articles

Space-time CutFEM on overlapping meshes I: simple continuous mesh motion

We present a cut finite element method for the heat equation on two overlapping meshes: a stationary background mesh and an overlapping mesh that moves around inside/“on top” of it. Here the overlapping mesh is prescribed by a simple continuous motion, meaning that its location as a function of time is continuous and piecewise linear. For the discrete function space, we use continuous Galerkin in space and discontinuous Galerkin in time, with the addition of a discontinuity on the boundary between the two meshes. The finite element formulation is based on Nitsche’s method and also includes an integral term over the space-time boundary between the two meshes that mimics the standard discontinuous Galerkin time-jump term. The simple continuous mesh motion results in a space-time discretization for which standard analysis methodologies either fail or are unsuitable. We therefore employ what seems to be a relatively uncommon energy analysis framework for finite element methods for parabolic problems that is general and robust enough to be applicable to the current setting. The energy analysis consists of a stability estimate that is slightly stronger than the standard basic one and an a priori error estimate that is of optimal order with respect to both time step and mesh size. We also present numerical results for a problem in one spatial dimension that verify the analytic error convergence orders.

Effects of the U.S. inflation reduction act on SMR economics

The U.S. Inflation Reduction Act (IRA) of 2022 provides a wide array of tax credits and other incentives for low-carbon energy. The technology-neutral clean generation production tax credit (PTC) (Section 45Y of the U.S. Internal Revenue Code) and the technology-neutral investment tax credit (ITC) (Section 48E) lower the net cost of new electricity generation projects with zero or negative greenhouse gas emission rates. We evaluate the impact of the IRA legislation—specifically the PTC and ITC—on the cost-competitiveness of small modular reactors (SMRs). We use the Argonne Low-carbon Energy Analysis Framework (A-LEAF) model to calculate the capacity factor of an SMR with a range of hypothetical variable operating and maintenance (O&M) costs in the Electric Reliability Council of Texas (ERCOT) electricity market. We selected ERCOT for market modeling because of its competitive structure, available data, and extensive use in prior literature. We use a discounted cash flow model to calculate the SMR’s net present value based on the market prices and capacity factors from A-LEAF, hypothetical ranges of capital and variable O&M costs, and other input parameters, with or without the IRA tax credits. We determine the SMR owner’s optimal choice of PTC or ITC for the hypothetical ranges of capital and variable O&M costs. We also evaluate potential shifts in the SMR owner’s optimal choice of PTC or ITC based on historical patterns of nuclear capital cost overruns in the United States. We also assess the sensitivity of our results to longer PTC period and electricity prices from the New England market, which tend to be higher than electricity prices in ERCOT. We find that even with the IRA tax credits, only SMRs with low capital and variable O&M costs would be economically feasible in the low-price ERCOT market scenario modeled. A longer PTC period and higher-price market such as New England, however, would significantly expand the economic feasibility of SMRs in the United States.

Carbon trading practices adoption for sustainable construction: A study of the barriers in a developing country

AbstractThe construction industry provides infrastructure and structures to society by consuming a substantial quantity of non‐renewable energy, which results in significant carbon dioxide emissions. Carbon dioxide (CO2) could pose a serious danger to the economy of any nation if proper measures are not put in place with the country being one of the leading producers and end‐users of fossil fuels in the world. This article seeks to evaluate the barriers to the adoption of carbon trading practices (CTP) in the construction sector with the view to ensuring low carbon usage. The article adopted quantitative approach with data obtained using questionnaire. Mean Item Score (MIS), standard deviation (SD), factor analysis and Kruskal–Wallis test was carried out in relation to the research questions. The study showed that the most significant barriers to the adoption of carbon trading are difficulties in obtaining finance, attitude to environmental sustainability and climate change, lack of cost‐effective abatement options and methods, lack of awareness of carbon market opportunties and risk in changes in the rules governing participation and credit among others. This study provides valuable insights into barriers of CTP in construction and will help stakeholders concerned with building energy performance to develop a functional framework for energy analysis in buildings to prepare possible risk analysis from the onset of project design spanning through completion.

A hybrid deterministic-diffuse approach to the analysis of vibration transmission across finite junctions

The average vibro-acoustic performance of a junction between two-dimensional structural elements is often quantified by its diffuse vibration reduction index, especially for building structures. Existing prediction methods either assume an infinite junction length or consider non-diffuse transmission. In this work an approach for predicting the diffuse vibration reduction index of finite junctions of arbitrary complexity is developed. First, the mean and (co)variance of the diffuse coupling loss factor of a finite junction are obtained within the hybrid deterministic-statistical energy analysis framework. Dedicated basis functions are proposed to efficiently describe the interface displacements of the diffuse subsystems. Subsequently, the relation between the mean vibration reduction index and the coupling loss factor is established. It is demonstrated that this relation involves both the mean and the variance of the coupling loss factor. Additionally, the relation between the variance of the vibration reduction index and the (co)variances of the coupling loss factors is derived. Finally, the proposed approach is both numerically validated and compared to experimental results for several finite junctions between building elements, which are modelled as plates. For the numerical validation, the results obtained with the proposed approach are compared with those of an ensemble of junctions with the same bare structure but with point masses attached at random locations on the walls and floors. The validations demonstrate that an accurate prediction of the mean and variance of the diffuse vibration reduction index is possible when the uncertainty across the random ensemble is sufficiently large. The comparison to experimental results involves T and X junctions between directly coupled plates. At low and medium frequencies, the experimental data are well captured within the 95% confidence interval of the hybrid model results. At high frequencies, the uncertainty on the hybrid results is very small; such differences with the experimental data are caused by modelling errors.

An integrated energy analysis framework for evaluating the application of hydrogen-based energy storage systems in achieving net zero energy buildings and cities in Canada

The integration of hydrogen-based energy storage systems into urban residential buildings is a promising method to reduce urban greenhouse gas emissions and achieve clean energy supply. However, a comprehensive energy evaluation method that accurately reflects the system lacking. To address this gap, this study proposes a robust integrated energy analysis framework for evaluating the application prospect of hydrogen-based energy storage systems in urban residential buildings. The framework involves building energy analysis modeling, uncertain modeling, and energy management optimization modeling and provides comprehensive energy analysis results that fully consider urban characteristics. The study evaluates the economy, environment, and energy development potential of hydrogen-based energy storage systems in 20 Canadian cities. The results indicate that the implementation of hydrogen-based energy storage systems in residential buildings in these cities resulted in annual economic costs ranging from 10,682 Canadian dollars to 234,689 Canadian dollars, annual reduced carbon emissions ranging from 29 kg CO2e to 20,712 kg CO2e, and annual energy potential rate ranging from 45.28% to 223.92%. The study found that hydrogen storage has an economic advantage in hydrogen-based energy storage systems, whereas battery storage has environmental and energy potential advantages. The proposed energy analysis framework can provide techno-economic references for Canadian planners to plan a reasonable hydrogen roadmap for urban residential buildings.

Energy consumption in China's ICT sectors: From the embodied energy perspective

Understanding the energy consumption associated with information and communication technology (ICT) is essential for the sustainable development of a digital economy. Previous studies have mainly focused on the impact of ICT on direct energy consumption, and few have studied the embodied energy of ICT sectors. This paper develops an embodied energy analysis framework by integrating the input-output model and structural path analysis to examine the embodied energy of China's ICT sectors. It not only identifies key consumer sectors, final demand and primary sources, but also tracks critical supply chain paths. The results show that the embodied energy of ICT sectors in 2018 was 216.22 million tons of standard coal equivalent, which is nearly three times as much as their direct energy. Communication Equipment was the largest consumer with a share of 30.2%. Export, fixed capital formation and urban consumption were the main final demand, accounting for 57.1%, 25.4% and 12.8%, respectively. It is worth noting that 75.1% of ICT sectors' embodied energy indirectly originated from non-ICT sectors such as Smelting of Metals. This finding indicates that ICT sectors indirectly consume more energy from their upstream sectors, which can explain why the embodied energy of ICT sectors is much greater than their direct energy. In addition, critical supply chain paths that transfer more embodied energy, such as “Smelting of Metals→Electronic Components→Export”, are extracted. Finally, some suggestions are proposed from production, consumption and path-based perspectives, which can provide new insights into the sustainable development of ICT sectors and the digital economy.

Structural reliability analysis based on interval analysis method in statistical energy analysis framework

The high-frequency vibration often happens in the aerospace and shipping field, and the durative high-frequency vibration will affect the work of engineering structures. It is very worth studying the structural reliability caused by high-frequency vibration, and the reliability analysis is an effective method to evaluate the structural safety level. So far, the research on structural reliability analysis in the high-frequency range is very few, and the aim of this paper is to provide a new method by which the structural security level in the high-frequency range can be evaluated. To begin with, the statistical energy analysis (SEA) parameters with measurement errors are represented by the interval variables consisting of the lower bound and upper bound, and the power balance equation with parameter intervals and input power intervals is established. Next, the modal energy interval of each subsystem is obtained by the interval analysis method. Finally, the performance function that can be used to evaluate the structural security level is provided. A simplified rocket fairing structure and a seven-plate coupling structure are respectively used as examples to demonstrate the usefulness of the presented method.

Diffuse sound absorption modelling of complex finite absorbers using a hybrid deterministic-statistical energy analysis approach

This contribution presents a numerical approach to quantify the response of an absorber in a diffuse reverberation room. Conventionally, this is done by considering an infinite absorber coupled to an acoustic halfspace. It is, however, well known that the diffuse absorption coefficient for a finite absorber can be quite different due to what is referred to in literature as the edge effect. A finite size correction has been developed previously, but it is only applicable to homogeneous absorbers and is based on a computationally costly quintuple integration. This contribution presents an alternative approach in which a deterministic model, e.g. using the finite element or modal transfer matrix method, is coupled with a statistical model of the room using a hybrid deterministic-statistical energy analysis framework. With this framework, also the theoretical uncertainty on this diffuse sound absorption that is inherent in the diffuse field assumption can be quantified, i.e. the variance of sound absorption results that can be theoretically expected across an ensemble of reverberation rooms of the same volume. The methodology is numerically and experimentally validated for several absorber types.

Mode count and modal density of nonsymmetric cross-ply laminated composite beams

Fiber-reinforced composites are used in many weight critical applications owing to their high strength-to-weight and stiffness-to-weight ratios. In certain applications, fiber-reinforced composites are subjected to broadband excitation sources that act over a significant portion of the audible frequency range leading to the response of a large number of higher order structural modes. In predicting the response levels of such systems, regardless of whether it is modeled in isolation or using a statistical energy analysis framework, it becomes necessary to quantify the number of resonant modes available to receive and store energy within a frequency band. Conventionally, the mode count and modal density are two parameters used for this purpose. Generally, the analysis of the mode count and modal density of anisotropic fiber-reinforced composite structures have received considerably less attention compared to their isotropic metallic counterparts, and as a result a number of key analytical formulations are yet to be derived and investigated. In this work, the modal distribution and density of nonsymmetric cross-ply laminated composite beams coupled in bending and longitudinal extension are analyzed. A wave approach is used to derive an expression for the mode count of the beam having generalized boundary conditions. Using numerical examples and nonlinear regression analysis, simplified expressions are then obtained for the average mode count function of the beam for different boundary conditions. An analytical expression for the modal density is obtained by taking the differential of the average mode count function with respect to frequency. The wave approach employed in this study is validated based on comparison with results from past literature in addition to finite element simulations. The expression for the modal density is also validated using a finite element model and is shown to be independent of boundary conditions.

Estimation of strains in composite cylindrical shells in a statistical energy analysis framework

Broad band Acoustic excitation is one of the critical loading conditions for launch vehicle/spacecraft structures. Estimation of responses of such multimodal systems in a wide band dynamic environment is commonly performed using Statistical Energy Analysis (SEA). In SEA the strains are determined from known velocity responses. These relations are available for plate type structures but not reported for composite cylindrical shells. Empirical relations based on experiments only are reported for isotropic cylindrical shells. In this work, expressions for estimating the strains in the higher order modes of a composite cylindrical shell from its velocity responses are derived. It is seen that the strains estimated using the existing empirical relations of isotropic cylinders, with the elastic properties corresponding to the composite cylinder, will be in large error. Numerical simulations carried out using a finite element model are in good agreement with those determined using the relations presented in this work.

Prediction of Noise Transmission Loss and Acoustic Comfort Assessment of a Ventilated Window using Statistical Energy Analysis

In this paper, a novel analytical method was developed based on statistical energy analysis framework to evaluate sound transmission loss through ventilated windows. The proposed method was compared to numerical and analytical models available in the literature. Results showed the success and advantage of the proposed model in predicting the acoustic performance of the ventilated window and the proposed method proved itself as a low-cost and high-accurate method. Considering the slit-like effect of the inlet and outlet of the ventilated window and channel attenuation is the distinct feature of the proposed method compared to the existing analytical models. This paper also discussed the effectiveness of the ventilated window in the provision of indoor acoustic comfort according to the different types of the outdoor traffic noise spectra and sound transmission loss. The results showed the acceptance of the indoor noise level made by the ventilated window. To recognize how the effective factors improve the acoustic performance of the ventilated window, the effect of window aspect ratio, channel thickness and opening size on Sound Transmission Class (STC) were studied. The results revealed that the ventilated window with higher aspect ratio and wider airflow channel has a higher STC while widening the opening size reduces the sound insulation.

Predicting the sound insulation of finite double-leaf walls with a flexible frame

With double-leaf wall systems such as plasterboard walls, a high sound insulation can potentially be achieved with a relatively low weight. The accurate sound transmission analysis of this type of wall is challenging since the leafs are usually coupled to a common frame, and since the finite dimensions play a role at lower frequencies. Existing analytical models for sound insulation prediction account for the deformation of the wall in an approximate way, while detailed numerical models are computationally very demanding. In this work, a sound insulation prediction model that achieves a high prediction accuracy at a low computational cost is developed. The wall components that display low geometrical complexity, such as the wall leafs and the cavity, are modelled in an analytical way. Sound absorbents in the cavity are modelled as equivalent fluids. The metal studs, which have a highly deformable cross section, are modelled in full detail with finite elements. The sound fields in the sending and receiving rooms are modelled as diffuse; they are rigorously coupled to the deterministic wall model by employing a hybrid deterministic-statistical energy analysis framework. With the resulting room-wall-room model, the airborne sound insulation is predicted for a range of double-leaf plasterboard walls with single, double and triple plating and with different cavity depths. The obtained transmission losses are validated against the results of an extensive set of experimental tests. A very good agreement between predicted and measured transmission loss values is observed. The single number ratings for the airborne sound insulation for nearly all walls differ from the experimental values by 0–2 dB, which is close to the average experimental reproducibility. At the same time, the computational cost is more than three orders of magnitude lower than for recently proposed models of similar accuracy.

A physical supply-use table framework for energy analysis on the energy conversion chain

In response to the oil crises of the 1970s, energy accounting experienced a revolution and became the much broader field of energy analysis, in part by expanding along the energy conversion chain from primary and final energy to useful energy and energy services, which satisfy human needs. After evolution and specialization, the field of energy analysis today addresses topics along the entire energy conversion chain, including energy conversion systems, energy resources, carbon emissions, and the role of energy services in promoting human well-being and development. And the expanded field would benefit from a common analysis framework that provides data structure uniformity and methodological consistency.Building upon recent advances in related fields, we propose a physical supply-use table energy analysis framework consisting of four matrices from which the input-output structure of an energy conversion chain can be determined and the effects of changes in final demand can be estimated. Real-world examples demonstrate the physical supply-use table framework via investigation of energy analysis questions for a United Kingdom energy conversion chain.The physical supply use table framework has two key methodological advances over the building blocks that precede it, namely extending a common energy analysis framework through to energy services and application of physical supply-use tables to both energy and exergy analysis. The methodological advances enable the following first-time contributions to the literature: (1) performing energy and exergy analyses on an energy conversion chain using physical supply-use table matrices comprised of disaggregated products in physical units when the last stage is any of final energy, useful energy, or energy services; (2) performing structural path analysis on an energy conversion chain; and (3) developing and utilizing a matrix approach to inhomogeneous units. The framework spans the entire energy conversion chain and is suitable for many sub-fields of energy analysis, including net energy analysis, societal energy analysis, human needs and well-being, and structural path analysis, all of which are explored in this paper.

Passenger transportation sector gasoline consumption due to friction in Southeast Asian countries

Energy demand in the transportation sector across Southeast Asian (SEA) region is rapidly increasing. This poses a challenge to the sector in mitigating greenhouse gas (GHG) emissions because of its heavy reliance on fossil fuels. Decarbonisation efforts tend to focus on the use of low carbon energy, often neglecting frictional losses in vehicles. Therefore, the study aims to determine the fuel cost savings and the environmental impact from reduction of frictional energy losses in passenger cars and motorcycles for selected SEA countries. An energy analysis framework is proposed; estimating a total of USD 42.6 billion/year is wasted through fuel energy loss in moving these vehicles in the selected SEA countries, emitting 109 Mtonne/year of CO2. By implementing relevant tribological improvement strategies, fuel energy savings of USD 18.3 billion/year could be achieved, leading to 46.6 Mtonne/year of CO2 emissions reduction. This level of CO2 emissions reduction, obtained via friction reduction, can contribute between 0.8% and 1.9% towards the committed GHG reduction targets for the selected SEA countries by 2030. It is emphasised that combined effort, from vehicle manufacturers and end-users, is required in implementing relevant friction reduction strategies to avoid backlash from inappropriate use of these strategies.

Bregman Storage Functions for Microgrid Control

In this paper, we contribute a theoretical framework that sheds a new light on the problem of microgrid analysis and control. The starting point is an energy function comprising the “kinetic” energy associated with the elements that emulate the rotating machinery and terms taking into account the reactive power stored in the lines and dissipated on shunt elements. We then shape this energy function with the addition of an adjustable voltage-dependent term, and construct so-called Bregman storage functions satisfying suitable dissipation inequalities. Our choice of the voltage-dependent term depends on the voltage dynamics under investigation. Several microgrid controllers that have similarities or coincide with dynamics already considered in the literature are captured in our incremental energy analysis framework. The twist with respect to existing results is that our incremental storage functions allow for a large signal analysis of the coupled microgrid. This obviates the need for simplifying linearization techniques, and for the restrictive decoupling assumption in which the frequency dynamics is fully separated from the voltage one. A complete Lyapunov stability analysis of the various systems is carried out along with a discussion on their active and reactive power sharing properties.

Optimization of operating parameters in a hybrid wind–hydrogen system using energy and exergy analysis: Modeling and case study

In this study, hybrid renewable energy system based on wind/electrolyzer/PEM fuel cell are conceptually modeled, and also, exergy and energy analysis are performed. The energy and exergy flows are investigated by the proposed model for Khaf region-Iran with high average wind speed and monsoon. Exergy and energy analysis framework is made based on thermodynamic, electro-chemical and mechanical model of the different component of hybrid system. Also, the effects of various operating parameters in exergy efficiency are calculated. The results show an optimum wind speed where the exergy efficiency and power coefficient is at maximum level, and also, when the ambient temperature start to be increased in wind turbine, the efficiencies decrease by a great deal for constant wind speeds. Also, the optimum temperature is calculated by exergy analysis in electrolyzer and fuel cell as 353 and the exergy efficiency of electrolyzer decreases by increasing the membrane thickness. Furthermore, pressure changes affect exergy and energy efficiency in PEM fuel cell. Finally, the electrolyzer and fuel cell efficiencies are calculated as 68.5% and 47% respectively.

Theoretical framework for energy analysis of hypersaline pressure retarded osmosis

Pressure retarded osmosis (PRO) has traditionally been focused on the mixing of seawater and river water, but in pilot scale tests, this mixing scheme has been found to be economically unattractive due to power densities that are too low. One way of obtaining higher power densities may be through use of hypersaline draw solutions. In this work, the theoretical framework for calculation of the free energy of mixing, the maximum extractable work in batch and co-current PRO systems, and the potential power densities of hypersaline solutions is presented. Calculations show that very high values in all categories are realizable. By diluting 26wt% (saturated NaCl) to seawater concentration, 15.7kWh/m3 draw is released and a maximum power density of 143W/m2 membrane can be obtained with a commercially available FO membrane. In cases where the hypersaline solution is the limiting solution, large losses of energy can be expected if the process is carried out as a constant pressure single stage operation. To minimize losses, a serial setup can be applied. Although the practical challenges for hypersaline PRO may be greater than for seawater based PRO, the high potential gains may make hypersaline PRO a more promising way of making the PRO concept realizable.

Energy efficiency analysis based on DEA integrated ISM: A case study for Chinese ethylene industries

The petrochemical industry evaluation is affected by numerous factors. Many previous studies proposed a use of data envelopment analysis (DEA) as a methodology for energy efficiency analysis in the petrochemical industry. However, excessive decision-making units (DMUs) of DEA model result in difficulties in evaluation and comparison of the different DMUs. In this paper, a new energy analysis framework of petrochemical industrial processes based on DEA integrated interpretative structural model (ISM) is proposed. The ISM method is brought up based on the partial correlation coefficient method to find the main factors and basic reasons that affect the energy consumption of the ethylene production system, which serve as the inputs of the DEA. Meanwhile, ethylene, propylene and C4 productions of the ethylene production system sever as the outputs of the DEA. Then the fractional DEA model is solved by using the linear programming method. The proposed evaluation method can overcome the shortcomings of the DEA model mentioned above, and also is able to reflect the effectiveness of the DMUs and guide the improvement directions of the ineffective DMUs based on slack variables. Our approach is applied in the energy efficiency analysis of Chinese ethylene industry in the petrochemical field. The empirical results show that the proposed energy consumption analysis method is valid and efficient in improvements of energy efficiency in ethylene production systems.

Research on the Prediction of Impact Sound Insulation to a Homogeneous Wall

In this paper, a theoretical model to evaluate impact sound transmission through a homogeneous wall is proposed. The model which is based on the Statistical Energy Analysis framework exhibits a system with room-wall-room. For the purpose to explore the mechanism of impact sound transmission through a wall, the impact sound reduction index between two rooms are predicted. Meanwhile, the variation of impact sound reduction index with the walls properties are also taken into account. The results reveal that the density, elastic modulus and thickness of a homogeneous wall have diverse effects on its impact sound insulation and can be chosen adequately to achieve ideal insulation values.It provides an approach to optimize impact sound insulating properties of the walls.

Reducing the total life cycle energy demand of recent residential buildings in Lebanon

Buildings require a substantive amount of energy for their operation. Recent studies have found that indirect requirements, such as the embodied energy associated with their construction and the transport-related energy of their users can be even more significant. A complete life cycle energy analysis of buildings in a Mediterranean context has seldom been undertaken.This paper relies on a multi-scale life cycle energy analysis framework to determine the energy use profile of recent residential buildings in Lebanon by taking into account embodied, operational and user transport energy requirements. It studies a representative case study building in Sehaileh, a suburb of the capital Beirut, over 50 years and identifies the most effective ways to reduce energy use across the different life cycle stages and scales of the built environment.Results show that the life cycle energy demand is dominated by transport energy (49%) followed by operational (33%) and embodied (18%) requirements. The main ways to reduce this life cycle energy demand comprise relocating jobs outside of the capital, putting in place an adequate public transport network, improving town planning to favour pedestrians and rely on gas or renewable energy sources instead of electricity when possible, notably for domestic hot water.