Performance Simulation Research Articles

Performance Simulation and Optimization of Cylindrical Mirror-Spliced Parabolic Trough Solar Collector

This paper proposes a new type of solar trough collector with a spliced cylindrical mirror and develops a new ray-tracing method to predict and optimize its performance. The mirrors of this system are composed of multiple cylindrical mirrors whose centers are on a parabola, and the normal vector of the centers of each cylindrical mirror is consistent with the normal vector of the parabola point where it is located. The new ray-tracing method is based on the transverse distribution of solar radiation, and it has been validated with Soltrace, with the maximum intercept factor error in the calculations being less than 0.31%. This paper compares the spliced cylindrical mirror trough solar system with the conventional parabolic trough system and finds that the influence of cylindrical, spherical, and coma aberration can be reduced to negligible levels by adjusting the system design. At the same time, the slope error and cost of the cylindrical mirror are much less than the parabolic mirror so it has better performance from numerical simulation. The spliced cylindrical mirror system can be further optimized to achieve an annual net efficiency of 65.52% in the north–south horizontal axis tracking mode.

Cooling Energy Challenges in Residential Buildings During Heat Waves: Urban Heat Island Impacts in a Hot-Humid City

Ignoring Urban Heat Island (UHI) effects may lead to an underestimation of the building cooling demand. This study investigates the impact of the UHI on the cooling demand in hot-humid cities, employing the Local Climate Zones (LCZs) classification framework combined with the Urban Weather Generator (UWG) model to simulate UHI effects and improve building performance simulations. The primary aim of this research is to quantify the influence of different LCZs within urban environments on variations in the cooling energy demand, particularly during heat waves, and to explore how these effects can be incorporated into building energy models. The findings reveal significant discrepancies in both the average and peak cooling demand when UHI effects are ignored, especially during nighttime. The most intense UHI effect was observed in LCZ 2.1, characterized by compact mid-rise and high-rise buildings, leading to a cooling demand increase of more than 20% compared to suburban data during the heat waves. Additionally, building envelope thermal performance was found to influence cooling demand variability, with improved thermal properties reducing energy consumption and stabilizing demand. This research contributes to the theoretical understanding of how urban microclimates affect building energy consumption by integrating LCZ classification with UHI simulation, offering a more accurate approach for building energy predictions. Practically, it highlights the importance of incorporating LCZs into building energy simulations and provides a framework that can be adapted to cities with different climatic conditions, urban forms, and development patterns. This methodology can be generalized to regions other than hot-humid areas, offering insights for improving energy efficiency, mitigating UHI effects, and guiding urban planning strategies to reduce the building energy demand in diverse environments.

Midwave infrared resonant cavity detectors with >70% quantum efficiency

We report resonant cavity infrared detectors with a peak wavelength of 4.54–4.58 μm that combine external quantum efficiency (EQE) exceeding 70% with spectral bandwidth 20–40 nm and ≤2% EQE at all non-resonance wavelengths between 4 and 5 μm. A 300-nm-thick absorber assures that most of the radiation propagating in the cavity produces photocurrent rather than parasitic loss. The cavity is formed by heterogeneously bonding a midwave infrared (MWIR) nBn detector chip to a GaAs/AlGaAs distributed Bragg reflector, etching away the GaSb substrate, forming mesas with diameter ≈100 μm, depositing a Ge spacer, and then depositing a single-period Ge-SiO2 top mirror. At all temperatures between 125 and 300 K, the responsivity at 150 mV bias exceeds 2.2 A/W and the EQE exceeds 61%. When the thermal background current for a realistic system scenario with f/4 optic that views a 300 K scene is derived from the observed EQE spectra, the resulting specific detectivity D* of 7.5 × 1012 cmHz½/W at 125 K operating temperature is 4.5 times higher than for a state-of-the-art broadband MWIR HgCdTe device. Simulations of the cavity performance indicate that EQE > 90% may be feasible following minimization of parasitic optical loss and maximization of the photocarrier collection efficiency. Potential applications include free space optical communication, chemical sensing, on-chip spectroscopy, and hyperspectral imaging.

Noncircular coherent signal direction of arrival estimation for coprime array: A subspace‐based interpolation approach

AbstractTo address the array aperture loss caused by mainstream direction of arrival (DOA) estimation algorithms for coherent signals using matrix interpolation techniques, a non‐circular (NC) coherent signal direction‐finding method that fully utilises covariance matrix information is proposed. The received data is firstly extended by leveraging its NC properties. Then, eigenvalue decomposition is performed on the covariance matrix to extract the signal subspace, which is mapped to a uniform linear array signal subspace via a mapping matrix. The first row of the covariance matrix corresponding to the signal subspace is employed to construct a Toeplitz matrix, and nuclear norm minimisation method is applied to recover the missing information. Finally, to avoid extra NC phase searching, the reduced‐dimension method is applied to obtain the estimation results. Performance analysis and simulation results show that the proposed algorithm achieves improvements in computational complexity, source estimation capability, and estimation accuracy.

LiDICS: a light dynamics interface for multi-domain simulation based on the FMI-standard

The assessment of adaptive façades faces several challenges, including the representation of adjustable material and geometric properties within building performance simulation. This paper introduces a methodical and model-based interface dedicated to this issue. Adjustable material and geometric façade properties can be captured and continuously adapted within the building performance simulation using this model, without the need to reinitialise the simulation as required with matrix-based methods. The method comprises two steps: model training and export. Model training transforms ray-tracing-based sampling outcomes into an algebraic function. Model export generates a Functional Mock-up Unit. The LiDICS method is applied to switchable membrane cushion constructions with complementary printing patterns. The model training achieves a high accuracy ( r 2 = 99.4 % ). Subsequently, an inter-model validation is conducted using annual simulation from the RADIANCE 3-phase method, likewise resulting in high accuracy ( r 2 = 98.5 % ). Lastly, a brief analysis is conducted to compare four operation strategies regarding coupled comfort and energy assessment.

Interscalable material microstructure organization in performance-based computational design

Various parameters can be integrated in material-based computational design in architecture. Materials are the main driver of these processes and evaluated with the constraints related to the form, performance, and fabrication techniques. However, current methodologies mostly involve investigating already existing materials. Studies on computational material design, in which new materials are developed by designing their microstructures in response to the performative issues, are generally undertaken at the material scale, and not adopted to the architectural design process yet. To resolve this issue, the methodology titled Interscalable Material Microstructure Organization in Performance-based Computational Design (I2MO_PCD) is developed and presented in three stages, including (1) identification of different types of material microstructures, (2) computational material design, and (3) prototyping. Data-based material modelling and visualization, and algorithmic modelling techniques are utilized, followed by various performance simulations as a part of an iterative process. New microstructure organizations are designed computationally, organized under three main groups as linear-curvilinear, crystal and metaball-voronoi. The outcomes of different performance analyses, including structure, radiation, direct sun hours, acoustics and thermal bridge were compared. Thus, the role of geometrical organization of microstructures, scales and material types in different performance computations were identified, by designing and fabricating synthetic materials.

Experimental, numerical simulation and design methodology of axial compression performance of combined steel columns for modular buildings

Load-supporting columns of modular buildings are their key load-bearing components, but fewer research studies have been conducted so far. To investigate the effects of initial defects of components, bolt-hole sizes, end stiffness, and component slenderness ratios on the axial compressive performance of load-supporting columns, this paper carries out a full-scale modeling experimental study and parametric finite element analysis. Subsequently, the test and finite element results were compared with the predicted results of the specifications in China (GB 50017-2017), the United States (ANSI/AISC 360-22), and Australia (AS 4100-2020) to assess the appropriateness of the specifications. The results show: It is recommended that small-section high-strength bolts be used to connect the load-supporting columns. When the overall and local defect magnitude meets the accuracy requirements, the magnitude size has little effect on the component bearing capacity. The direction of the overall bending defect has little effect on the initial stiffness and peak load-carrying capacity of the steel tube spandrel column. When the regularized slenderness ratio of the components is less than 0.4, the reduction of the hinged restraint capacity is less than 10% compared with that of the stiffened restraint capacity. The Chinese specification can be used for component design and its predictions are on the conservative side. As the section width-to-thickness ratio becomes larger, the predictions of the U.S. specification change from an accurate prediction to one with too large an error. The Australian specification predictions were all on the unsafe side, but most components had errors of 10% or less. The results of this paper help to promote the development of modular building technology.

Modelling and numerical simulation of heat transfer and hydrodynamic performance of multi-pass parallel flow condensers – A novel algebraic method to determine flow distribution

In multi-pass parallel flow condensers (MPFCs), refrigerant flow maldistribution poses a significant challenge, deteriorating heat transfer performance. A robust flow distribution prediction method is crucial for the accuracy and applicability of an MPFC model. This study originally develops a new algebraic method to determine refrigerant distribution in tube-passes for MPFCs. This algorithm can be directly integrated with the authors' previously developed 2-D distributed-parameter model for MPFCs with liquid-vapor separation (MPFCs-LS). The novel algorithm applies to conditions where: 1) the inlet tube of the first tube-pass is positioned arbitrarily along the vertical inlet header, and 2) the mediate headers have or lack liquid-vapor separation. The new condenser models are validated by comparing the predicted results with the experimental data of an MPFC and an MPFC-LS. The predicted heat transfer capacity and pressure drop show deviations within ±5% and ±35%, respectively. Results also reveal that the optimal position of the inlet tube is one tube pitch downward from the top of the inlet header under the given configuration and conditions. The best position of the inlet tube, compared with the worst case, improves the flow distribution by 67%, reduces the pressure drop by 68% and increases the heat transfer by 0.5%.

Thermodynamic coupling performance analysis and simulation of aerated oil medium steel-BMC joint surface

In order to study the thermal coupling properties of aerated oil medium steel-basalt mineral composite (BMC) joint surface and establish an accurate and convenient simulation analysis method. The calculation method of the actual contact area ratio weight matrix of the aerated oil medium steel-BMC joint surface was studied. The virtual material theory model of the thermal coupling performance of the aerated oil medium steel-BMC joint surface was established by combining it with the virtual material theory. Based on the virtual material method, the thermodynamic coupling performance of the aerated oil medium steel-BMC joint surface was studied by finite element simulation, and compared with the experiment and numerical simulation methods of fractal theory. The results show that the temperature and strain changes of BMC specimen with virtual material method have a good coincidence with the experimental results, and the relative error is minimal. At the same time, the virtual material simulation model is simple, less computation and higher efficiency. It is proved that the method in this paper has better precision and convenience.

Analysis of hydrodynamic performance and acoustic characteristics of loop propellers

To improve the efficiency and stealthiness of marine operations of autonomous underwater vehicles (AUVs), 12 loop propellers with different structural parameters are selected as research subjects. The Reynolds-averaged Navier–Stokes equations method is used to simulate the flow field result around the loop propellers and is combined with detached eddy simulation and the acoustic analogy method for hydrodynamic analysis and noise prediction. The influence of three structural parameters, namely the number of propeller blades, the thickness of propeller blades, and the pitch of propeller blades, on the hydrodynamic and noise performance of the propeller is investigated, and the loop propeller structure with the optimal hydrodynamic and noise performance is selected. The research results indicate that increasing the number of propeller blades and increasing the pitch of the loop propeller can significantly improve the thrust and torque of the propeller and effectively reduce the noise. However, increasing the thickness of the propeller blades can also increase the thrust and torque of the propeller, but it will sacrifice the noise performance of the loop propeller to a certain extent. The sensitivity of the noise performance with respect to the blade thickness is significantly higher than that of the two parameters of blade number and pitch. To verify the accuracy of the hydrodynamic and noise performance simulation results, this study conducted hydrodynamic and noise performance tests on the preferred loop propeller structure in the towing pool and anechoic pool and successfully verifies the reliability of the numerical simulation method used in this study for the prediction of the propeller performance by comparing the test data with the simulation results. This study provides theoretical support for the design optimization of loop propellers and helps to promote the design of high-efficiency and low-noise propellers in complex marine environments.

Design and Implementation of Solar-Powered Pumping System in IKN Nusantara Area

Solar-powered pumping systems are an alternative to providing a sustainable and independent water source. This system declines the dependency on fossil fuels, which generate no greenhouse gas emissions while operating. This paper presents the design, implementation, and performance testing of a solar-powered submersible water pump in Bumi Harapan and Bukit Raya Village to provide a supplementary water source for residents. To meet the daily water supply requirement of 10 m3 in two identical water towers, a 1.1 kW rated power water pump and a 2.2 kW photovoltaic system are chosen. A solar pump controller with the ability to switch power sources from photovoltaic to grid is used in the system to maintain a consistent water supply if needed. Based on performance simulations using PVSyst software, the designed systems cannot fulfill daily water requirements. However, they are expected to fill both water towers with a daily average supply of 5.78 m3 for the Bumi Harapan site and 9.23 m3 for the Bukit Raya site. These inabilities occurred because the pumps must operate with an elevation head that is more remarkable than the specifications. Performance tests using a solar power meter (SPM) and power quality analyzer (PQA) showed that the electric submersible pump (ESP) will supply water with a flow rate that depends on solar irradiance. Based on the data collection, the ESP successfully operates near its rated capacity during the peak sun hour.

Modeling and parametric study of tubular high temperature steam electrolysis (HTSE) cell for enhanced hydrogen production

High-temperature steam electrolysis (HTSE) achieves high efficiency in hydrogen production and plays a critical role in advancing hydrogen-based energy frameworks. Progression from single-cell to multi-cell stacks is essential, but this transition is hindered by the complex interplay of electrical, flow, and thermal management. Modeling is crucial for addressing these complexities, allowing for simulation of cell and stack performance. In this study, 2D axisymmetric modeling of HTSE cell in tubular configuration is performed. A tubular HTSE cell is fabricated and tested in solid oxide electrolysis (SOEC) mode and impedance modeling of the cell is conducted from 200 °C to 820 °C, analyzing cell behavior transition with temperature. Multiphysics modeling parameters are acquired experimentally and modeling results align well with the experimental data. Further cell analysis is carried out with the developed model by acquiring parameters that are challenging to measure experimentally. The study also determines optimal flow conditions for HTSE cells through parametric variations.

Prediction of Pollutant Emissions from a Low-Speed Marine Engine Based on Harris Hawks Optimization and Lightgbm

With the rapid development of data science, machine learning has been widely applied to research on pollutant emission prediction in internal combustion engines due to its excellent responsiveness and generalization ability. This article introduces Lightgbm (LGB), which belongs to ensemble learning, to predict the pollutant emissions from a low-speed two-stroke marine engine. The dataset used to train LGB was derived from a one-dimensional performance simulation model of the engine, which was rigorously verified for its reliability by experimental data. To further improve the forecast performance of the LGB model, we used Harris Hawks Optimization (HHO) to automatically optimize the hyperparameters of the model, and finally, we analyzed the importance of the model features. The results show that changes in engine control parameters have significant influences on NOx and soot emissions from the engine, which can serve as the basis for the selection of the LGB model features; the LGB model was able to accurately predict pollutant concentrations from the engine with much higher accuracy than a single decision tree (DT) model; combining with HHO, the predictive ability of the LGB model was significantly improved, such as for the validation set prediction results, the mean absolute error (MAE) was reduced by about 20%, the mean squared error (MSE) was reduced by about 30%, and the coefficient of determination (R2) was increased by about 0.005; and the importance analysis of the model features indicated that the combustion condition of the fuel was highly correlated with the generation of the pollutants, and the fuel injection phases can be adjusted in practice to achieve highly efficient and low-emission processes of combustion. The results of this study can provide references for the development of a new generation of highly efficient and low-pollution marine engines.

BSDF Data generation for daylight applications: A call for international standardization

Standardized methods for generating angle-dependent, bidirectional, solar-optical properties for complex fenestration systems do not exist, which means that energy and daylight evaluations in building performance simulations often suffer from major inaccuracies. This position paper provides an overview of state-of-the-art data-driven methods for characterizing light scattering properties of fenestration materials and blind systems (e.g. fabrics, metal slats, patterned glazing), validation via laboratory, simulation and field tests, and salient issues in support of standardization of such methods via the International Standardization Organization (ISO). The ISO standard is intended to provide the fundamental underpinnings for recently mandated daylight standards that rely on bidirectional scattering distribution function data for climate-based daylight modelling and building performance simulations.

Coupled theoretical modelling for the photoelectric performance by the concave-bent flexible PV module

Flexible PV module can fit with complex building skins and provide electricity for the building users. However, for the concave bent PV module, the special structure will cast shadow on itself, resulting in power loss during the working conditions, which is rarely investigated in previous studies. Combined optical-electrical-thermal model is decoupled to describe the realistic physical field and predict the concave module's electrical power output and working temperature. The beam shading ratio (BSR) and the diffuse shading ratio (DSR) are proposed based on the microfacet subdivision, which describes the real-time solar irradiance distribution and quantify the influence of self-shadow on the photoelectric performance by the concave-bent module under dynamic real-time working conditions. The concave PV module with the longitudinal/lateral layout is constructed and outdoor experiments are conducted to collect the data for the theoretical model verification. The parametric analysis is carried out to investigate the influence of inclination, curvature, and azimuth, demonstrating that increasing inclination and curvature angles raise power loss due to shading. Weather data of four cities are imported into the model to conduct annual performance simulation with longitudinal/lateral installation respectively. The model established in this paper has significant value for performance prediction in complex surface photovoltaic systems.

Thermo-economic investigation of transcritical Carbon Dioxide solar-thermal power plants, Part 1: System modeling and simulation for design with validation of results

This study comprises the engineering design and economic assessment of a novel trans-critical-point Carbon Dioxide cycle integrated with a solar Parabolic Trough Collector (PTC) power plant. A 1-MW facility with a Rankine transcritical CO2 cycle providing combined heat and power for a small industrial facility in Texas was proposed as the baseline power plant to perform the analysis. A design and modeling effort was performed in Engineering Equation Solver (EES) for the many systems and components of the power plant, including the solar field, the power block, and sub-components such as turbomachinery and heat exchangers. The model created enabled the simulation of plant performance for the median day of each month in the year by inputting meteorological TMY3 data, and results were extrapolated to estimate the annual energy and monetary income yield. Data processing was performed with MATLAB. Economic analysis included estimation of capital and O&M costs for the baseline plant. Results were verified through empirical performance simulation, using System Advisor Model (SAM), a software provided by NREL. The levelized cost of energy (LCOE) for the modeled plant was $0.2915/kWh, as calculated with EES/MATLAB, and $0.305/kWh, as calculated with SAM, resulting in a difference of less than 5%, between the two different simulation approaches. The design and simulation work presented herein provides the means to perform an optimization analysis, which reveals important clues as to how the energy cost could be reduced so as to make this technology a competitive alternative within the energy market.

Disaggregation of climatic variables using a novel stochastic approach and its application in building performance simulation studies

Daily weather data, both observed and synthesized, are available for most locations worldwide but not at the sub-daily temporal scale, which is desirable for building performance analysis. In this context, we introduce a novel stochastic methodology based on pattern mapping for disaggregation of daily data into sub-daily (hourly) time resolution. The methodology has been tested and validated for three weather variables required for energy simulation (temperature, relative humidity and solar radiation). This approach yields better results than existing methodologies for the selected climate variables. Process efficiency is maintained even with the limited input data. Its stochastic nature enables time-invariant pattern mapping to generate future weather files. The annual ‘space conditioning energy’ was simulated to assess building performance accuracy using weather files for the hottest, coldest, average and test reference years (TRY) from disaggregated and observed datasets. Results show that the pattern mapping disaggregation methodology accurately downscales daily to sub-daily data.

Review of the Role of Urban Green Infrastructure on Climate Resiliency: A Focus on Heat Mitigation Modelling Scenario on the Microclimate and Building Scale

This systematic review explores the role of urban green infrastructure (UGI) in enhancing climate resilience, focusing mainly on heat mitigation modelling and its application at both urban and building scales. The study analyses 207 articles published in the last five years at the screening stage and 50 at the inclusion stage, highlighting the effectiveness of UGIs in reducing ambient temperatures and improving building energy efficiency through shading and evapotranspiration. Advanced simulation tools like Computational Fluid Dynamics (CFD) and Building Performance Simulation (BPS) are increasingly relied upon, though challenges remain in accurately modelling vegetation and urban-climate interactions. The review identifies critical research gaps, particularly in evaluating UGI’s performance under future climate change and seasonal variation scenarios, emphasising the need for refined simulation techniques. Moreover, the evapotranspiration modelling of UGIs needs to be developed on the BPS scale. Addressing these gaps is essential for optimising UGI design to ensure their effectiveness in future urban climates. The review calls for further studies on long-term UGI resilience, especially in rising global temperatures and evolving urban environments.

A knowledge graph-based framework to automate the generation of building energy models using geometric relation checking and HVAC topology establishment

Building Energy Models (BEM) are widely utilized throughout all stages of a building's lifecycle to understand and enhance energy usage. However, creating these models demands significant effort, particularly for larger buildings or those with complex HVAC systems. While a substantial amount of information can be extracted from Building Information Models (BIM) — which are increasingly accessible and provide necessary data for geometric and HVAC contexts — this information is not readily usable in setting up BEM and typically requires manual translation. To address this challenge, this paper introduces a BIM-to-BEM (BIM2BEM) framework that focuses on automating the generation of HVAC parts of BEM models from BIM data. Core to the methodology is the extraction of HVAC system topologies from the BIM model and the creation of a knowledge graph with the HVAC topology. The topology transformation unfolds in three key stages: first, a geometry-induced knowledge graph is established by examining the geometric relationships among HVAC elements; second, this graph is converted into an informative HVAC topology with enhanced properties from additional data sources; and finally, the informative topology is simplified into a BEM-oriented HVAC topology compliant with BEM platforms such as EnergyPlus. A case study of a large university building with a complex HVAC system showcases that the proposed framework achieves automatic and precise generation of building performance simulation models. The model's predictions are then validated against actual measurements from the building.

Numerical Study of the Cavitation Performance of an Ice-Blocked Propeller Considering the Free Surface Effect

Propeller cavitation performance can be predicted based on model tests or simulations. However, the cavitation performance of an ice-blocked propeller near the free surface differs from that of a propeller in the cavitation tunnel. Therefore, research on the cavitation performance simulation of propellers near the free surface holds crucial scientific significance. In this study, a coupled model was established using Computational Fluid Dynamics (CFD) and the Volume of Fluid (VOF) coupling method. The CFD-VOF model weighted the overlapping grids and simulated the cavitation performance of an ice-blocked propeller using various immersion depths, cavitation numbers, and advance coefficients. The propeller inflow ahead of the propeller and the wake field behind it were controlled to accurately obtain the propeller cavitation performance. Moreover, a comparison was conducted between the cavitation tunnel test results and the numerical simulation results at various immersion depths. When the immersion depth was at a distance of 1D, the effect of the free surface on the propeller cavitation performance became significant. When the immersion depth was at a distance of 9D, the average errors between the numerical simulation and the model test data were within 10%. This study analyzed the cavitation performance of ice-blocked propellers near the free surface and provided valuable insights for the design of ice-class propellers.