Passive Solutions Research Articles

Heat transfer enhancement of phase-change materials (PCMs) based thermal management systems for electronic components: A review of recent advances

Thermal control of electronic components using phase-change materials (PCMs) in heat sinks is an efficient method that has attracted the attention of numerous researchers. However, because of its poor thermal conductivity restrict their usage for cooling electronic components. Hence, to overcome this issue, thermal conductivity enhancers (TCEs) are used. The aim of this article is to conduct a review of different TCEs techniques applied on the PCM-based heat sinks. Included are recent papers on experimental and numerical works with an emphasis on analysing the impact of using TCEs such as fins, foams and nanoparticles for improving the thermal performance of the PCM-based heat sinks. According to the litterature, few studies have been conducted on PCM-based heat sink under intermittent conditions. In addition, there is a lack of numerical works on hybrid heat sinks that showed great thermal cooling than coventional heat sinks. Furthermore, it seems that the interesting heat transfer capabilities of nanoparticles systems, as passive solutions for electronic thermal management are preferable. Because of their high thermal conductivity, high heat storage and with light weight than fins and foams as TCEs techniques. Other conclusions and future perspectives are introduced.

Design and evaluation of dual passive hydrogen recovery subsystem for 10 kW PEMFC

Many active hydrogen recovery systems have been proposed for medium-to-large scale proton exchange membrane fuel cells (PEMFCs). However, relatively few passive solutions for hydrogen recovery in PEMFC systems of such size are available. Accordingly, the present study proposes a novel passive hydrogen recovery system incorporating two vacuum ejectors (one high-flow rate and one low-flow rate) for a 10 kW PEMFC. MATLAB/Simulink models are constructed of the PEMFC system and all its major components. The validity of the simulation model is confirmed via a comparison with the experimental data reported in the literature. Further simulations are then performed to investigate the effects of the fuel stack active area and working temperature on the hydrogen recirculation performance and hydrogen stoichiometric ratio. Overall, the results show that the proposed dual vacuum ejector system increases the fuel cell efficiency to 52.16% and maintains the average fuel cell efficiency at 52.12%.

ARCHITECT’S RESPONSE ON UTILISATION OF INTERLOCKING STABILISED SOIL BLOCKS AS AN ALTERNATIVE BUILDING MATERIAL FOR HOUSING PROJECTS IN SOUTHWEST NIGERIA

Housing has become a major concern in Nigeria and requires sustainable intervention. The United Nations' position on the advantages of Interlocking Stabilised Soil blocks (ISSBs) in the year 2009 is fundamental to its usage for affordable housing delivery in developing nations. Considering the fact that the recent global economic challenges impacted the Nigerian economy, housing, recorded to be deficient by the Ministry of Housing in 2015 is a concern due to the tremendous rise in the cost of materials. This study assessed architects' response to the adoption of ISSBs as an alternative building material for Housing Projects in Southwest Nigeria towards recommending its widespread adoption for economical building construction works. The objectives were; to examine the role of architects in building material specifications; to explore characteristics of ISSBs that make them viable as an alternative building material, and to assess architects' response to the adoption of ISSBs. The study adopted a Mixed Method of Research in carrying out the assessment. Relevant literature was reviewed and necessary data were collected through interviews granted to the targeted respondents towards providing in-depth knowledge of ISSBs. Structured Questionnaires were administered to architects who are lecturers in selected schools of architecture who are members of the Association of Architectural Educators or registered with the Architects Registration Council of Nigeria. A total of 66 questionnaires were returned from the 70 administered. Findings revealed that architects have a huge role in building material specifications. ISSBs offer a passive solution to building challenges (better thermal comfort, quality indoor

Neural-Assisted Synthesis of a Linear Quadratic Controller for Applications in Active Suspension Systems of Wheeled Vehicles

This article presents a neural algorithm based on Reinforcement Learning for optimising Linear Quadratic Regulator (LQR) creation. The proposed method allows designing such a target function that automatically leads to changes in the quality and resource matrix so that the target LQR regulator achieves the desired performance. The solution’s stability and optimality are the target controller’s responsibility. However, the neural mechanism allows obtaining, without expert knowledge, the appropriate Q and R matrices, which will lead to such a gain matrix that will realise the control that will lead to the desired quality. The presented algorithm was tested for the derived quadrant model of the suspension system. Its application improved user comfort by 67% compared to the passive solution and 14% compared to non-optimised LQR.

A Review on Optimal Energy Management in Commercial Buildings

The rising cost and demand for energy have prompted the need to devise innovative methods for energy monitoring, control, and conservation. In addition, statistics show that 20% of energy losses are due to the mismanagement of energy. Therefore, the utilization of energy management can make a substantial contribution to reducing the unnecessary usage of energy consumption. In line with that, the intelligent control and optimization of energy management systems integrated with renewable energy resources and energy storage systems are required to increase building energy efficiency while considering the reduction in the cost of energy bills, dependability of the grid, and mitigating carbon emissions. Even though a variety of optimization and control tactics are being utilized to reduce energy consumption in buildings nowadays, several issues remain unsolved. Therefore, this paper presents a critical review of energy management in commercial buildings and a comparative discussion to improve building energy efficiency using both active and passive solutions, which could lead to net-zero energy buildings. This work also explores different optimum energy management controller objectives and constraints concerning user comfort, energy policy, data privacy, and security. In addition, the review depicts prospective future trends and issues for developing an effective building energy management system, which may play an unavoidable part in fulfilling the United Nations Sustainable Development Goals.

Improving building thermal comfort through passive design – An experimental analysis of phase change material 3D printed concrete

As the effects of climate change are felt around the world, it is important to consider more sustainable practices in every industry to reduce greenhouse gas emissions and preserve resources. Sustainable practices in the building sector and construction industry include incorporating passive design solutions into the building design and constructing with recycled materials. In this research the main passive design solution considered is thermal energy storage by latent heat capacity of phase change materials (PCMs). Construction with bricks is widely used in the developing world, allowing much potential for the use of recycled brick aggregate in construction composites. This research is the first of its kind on PCM inclusion by aggregate impregnation of recycled brick aggregate in 3D printed concrete (3DPC). Two cavity façade sections are 3D printed using two concrete mix designs - the first, in which 64% of the natural aggregate in the mix is replaced with recycled brick aggregate, and the second, adjusted from the first by an addition of PCM to the pores of the recycled brick aggregate by vacuum impregnation, creating concrete with a total average latent heat capacity of 7360 J/kg. These façade sections are used in four sets of thermal tests in Stellenbosch, South Africa. It is concluded that by latent heat storage, PCM delays heat transfer through the PCM-3DPC passive design façade section, significantly increasing the time that internal ambient temperatures remain within standardised ranges of thermal comfort, and reducing the maximum internal ambient temperatures by up to 3.9 °C. Minimal leakage of PCM is proven by effectiveness of the PCM in the PCM-3DPC façade section after five months of exposure to outdoor ambient spring and summer conditions.

Assessment of latent energy storage systems for thermal management applications in hot and dry climatic condition

Currently, energy is the driving force behind almost everything and its demand is rapidly increasing, with a projected rise of 77 % by 2050. Amidst this, it is imperative to use the available energy more judiciously. Energy conservation and efficiency needs to be implemented in every domain of application. The use of passive measures can be utilized for implementing energy conservation. One such method is to use Phase Change Materials (PCMs), which has the potential to absorb enormous amounts of thermal energy by undergoing phase change. PCMs can be applied for refrigeration, heating, ventilation, air-conditioning, and thermal management applications. One of the drawbacks of PCM is their low thermal conductivity for which PCM enhancement is to be studied and implemented. The objective of this study is to discuss PCMs, their properties and potential applications for energy conservation and energy efficient operation. The study discusses heat transfer enhancement of PCMs using nanoparticle incorporation. It also assesses the potential energy savings that can be incurred with PCM implementation within building elements and efficiency improvement of solar photovoltaic panels. It is observed that PCM incorporation in buildings can result in heat transfer reduction by 50% and energy storage potential can be increased by 22%. It is also observed PCM implementation in PV panels increase their efficiency by 0.5–3% which is passive solution, with no auxiliary power input required.

Engine Order Cancelation in a super sports car cabin

Active noise control (ANC) has been used in several systems to improve acoustic performance while avoiding increases in the size and weight required by passive noise control solutions. This paper considers an ANC application aimed at controlling the sound field in the cabin of a supersports car with a naturally aspirated engine. This work studies the performance of a system that employs microphones and loudspeakers in the car cabin and uses a reference signal obtained from CANbus data. The controller exploits a multichannel, multi-order Fx-LMS algorithm to control the sound only in the region surrounding the driver's ears. Due to the nature of the car, this ANC application provides an interesting and challenging case study due to the rapidly changing acoustic excitation provided by the engine. The paper therefore describes a system for noise reduction, focusing on engine order reduction, aiming at achieving control during the most representative manoeuvre known as the "Wide-Open Throttle" (WOT). The investigated controller - acting locally and only on some orders simultaneously - shows good sound attenuation over the entire spectrum, with peaks of reduction exceeding 10 dB, and achieving a 5% overall decrease in the loudness, which is calculated according to ISO 532-1.

Engineering and scaling-up ceramic tiles with humidity self-regulation functionality

The humidity regulation in the interior spaces of buildings by means of passive solutions that do not require energy consumption is a topic of great interest due to the current needs for comfort and energy efficiency. This paper addresses the engineering of humidity regulating ceramic tiles that incorporate a functional coating formulated from gibbsite together with other common raw materials whose moisture regulating capacity has been demonstrated previously. A multi-layer coating tile system has been proposed, consisting of the following elements: an engobe layer, the functional coating with the regulating capacity, a decoration by inkjet technology and a protective topcoat glaze.This system has been analysed with moisture adsorption–desorption tests. The moisture regulation capacity and the effect of the coating thickness on this property have been determined, allowing to optimise the functionality.Finally, an analysis of the humidity regulation has been performed on the basis of demonstrators or small-sized cubicles that simulate the conditions of final use in rooms of buildings. The results show the different behaviour of the demonstrator with functional tiles in relation to conventional tiles, with an indoor ambient humidity that remains in the comfort zone for longer periods of time.

Mass transport in oscillatory electroosmotic viscoelectric flow in a hydrophobic microchannel with steric effect

We conduct a numerical study of viscoelectric and steric effects on an oscillatory electroosmotic flow (OEOF) and their impact on the mass transport of a passive solute through a hydrophobic microchannel. In many applications of electroosmosis, zeta potentials as high as 100–200 mV can be found; in such a situation, the Debye–Hückel approximation is no longer valid, and the steric effect must be considered because the crowding of finite-sized ions close to the microchannel walls. In addition to the previous effect, the local viscosity can be increased due to the viscoelectric effect for strong electric potentials induced in the electric double layer. Earlier works have studied the mass transfer caused by an OEOF; however, the combined effects’ influence has not been considered. This research suggests that under an appropriate combination of the viscoelectric and steric effects, together with the microchannel hydrophobicity, the mass transport can be controlled and notably enhanced compared with the case where such effects are disregarded. An interesting behavior occurs for relatively high values of the steric factor ν, where there is a linear dependence between the mass transport and the viscoelectric factor ; in contrast, for low values of ν, the relationship is non-linear.

A Reference Framework for Zero Energy Districts in Panama Based on Energy Performance Simulations and Bioclimatic Design Methodology

The need for efficient buildings to contribute to sustainable development has led to the proposal of goals and regulations in different countries linked to net zero energy objectives, following approaches specific to their regions. Such regulations are not yet developed in a developing country such as Panama. Thus, this study develops the first framework for Zero Energy Districts (ZED) in Panama based on passive and active solutions through dynamic simulation. For this, an existing urbanization area consisting of 34 residential buildings, called the existing case (EC), was studied. After undergoing a design based on the bioclimatic methodology, a redesigned case (RC) is proposed to maintain thermal comfort and reduce energy consumption. Key redesign factors are the buildings’ shape, orientation, glazing, the use of shadows, material of the walls, and the air conditioning configuration. Results showed energy consumption decreases by 37.5% when considering all buildings with natural ventilation, reaching ranges of positive net energy (+356.50 kWh/m2y). In the case of nearly ZED in Panama, the ranges could be considered between 14 and 180 kWh/m2y. This balance indicates that there is potential on site to develop zero energy districts.

Design of a passive flow control solution for the mitigation of vortex induced vibrations on wind turbines blade sections as a response to extreme weather events

The goal of the present work is to perform exploratory assessments on the suitability of microcylinder devices to mitigate wind turbine blade vortex induced vibration in small cross flow regimes, specially occurring under adverse weather events. For this purpose, the deep stall behavior of the NACA0021 has been evaluated for the first time on a wide range of high angles of attack (50°–130°) by means of CFD assessments, and the effects of microcylinders have been studied in terms of the reduction of aerodynamic coefficient magnitudes and fluctuations. In a first step, the passive flow control solution at 90° has been analyzed for a total number of investigated cases equal to 15, keeping constant the diameter of the microcylinders and varying the relative positions of these devices with respect to the blade. Mitigations of the load standard deviations between 63% and 97% across all the tested angles of attack have been found. Additionally, genetic programming (GP) was used to obtain a more general viewpoint of the effect of the microcylinders on the aerodynamics forces. Assessments of the flow fields confirm that properly located microcylinders disrupt the coherent vortical structures in the wake, responsible for periodic loading on the blade section.

Multimode vibration control of stay cables using pseudo negative stiffness MR damping system

At present the vibration control of stay cable suffers from low damping effectiveness in single mode vibration caused by the limitation of damper installation position as well as the poor modal compatibility, that is, a rapid degradation performance when the actual mode deviates from the designed optimal mode. In this paper, one practical semi-active magnetorheological (MR) damper based control solution is proposed to address the problems faced in multi-modal vibration control of stay cables. The semi-active pseudo negative stiffness (PNS) control strategy takes full account of the MR damper’s mechanical characteristics and the demands of the stay cable vibration control. Compared with the linear equivalent model, the proposed time-varying model exhibits more details of the damping force and the nonlinear response of the damped stay cable, which shows its essential role in the optimal design of MR-PNS scheme. Then the optimal design method of MR-PNS multi-modal vibration control for stay cable is summarized by taking the first three modes vibration control of the J20 cable in Nanjing Baguazhou Yangtze River Bridge as simulation examples. The simulations of cross-modal, multi-modal and wind-induced vibration cases are conducted respectively, while the results show that the optimal designed multi-modal MR-PNS scheme can simultaneously exceed the passive maximum modal damping ratio within first three modes. The advantages of the proposed MR-PNS method in high damping efficiency and modal compatibility could be verified by comparing with the passive multi-modal damping solution.

A Numerical Study of the Suitability of Phase-Change Materials for Battery Thermal Management in Flight Applications

Battery pack specific energy, which can be enhanced by minimising the mass of the battery thermal management system (BTMS), is a limit on electric fixed-wing flight applications. In this paper, the use of phase-change materials (PCMs) for BTMSs is numerically explored in the 3D domain, including an equivalent circuit battery model. A parametric study of PCM properties for effective thermal management is conducted for a typical one-hour flight. PCMs maintain an ideal operating temperature (288.15 K–308.15 K) throughout the entire battery pack. The PCM absorbs heat generated during takeoff, which is subsequently used to maintain cell temperature during the cruise phase of flight. In the control case (no BTMS), battery pack temperatures fall below the ideal operating range. We conduct a parametric study highlighting the insignificance of PCM thermal conductivity on BTMS performance, with negligible enhancement observed across the tested window (0.1–10 W m−1 K−1). However, the PCM’s latent heat of fusion is critical. Developers of PCMs for battery-powered flight must focus on enhanced latent heat of fusion, regardless of the adverse effect on thermal conductivity. In long-haul flight, an elongated cruise phase and higher altitude exasperate this problem. The unique characteristics of PCM offer a passive low-mass solution that merits further investigation for flight applications.

BIM-supported automatic energy performance analysis for green building design using explainable machine learning and multi-objective optimization

Supported by the combination of the advanced BIM technique with intelligent algorithms, this paper develops a systematic framework using explainable machine learning and multi-objective optimization to realize the automatic prediction and optimization of building energy performance towards the sustainable development goal. There are three critical parts incorporated, including the DesignBuilder simulation, BO-LGBM (Bayesian optimization-LightGBM) and an explainable method SHAP (SHapley Additive explanation)-based prediction and explanation of building energy performance, and AGE-MOEA algorithm-based multi-objective optimization (MOO) under sources of uncertainty. It has been verified in a case study for green building design. Results show that: (1) The predictive BO-LGBM model can make a highly precise prediction in agreement with the simulation data, reaching up the R2 larger than 93.4% and MAPE smaller than 2.13%. From the SHAP calculation, features related to the HAVC (Heating Ventilation and Air Conditioning) system tend to contribute more to affecting the prediction results. (2) The AGE-MOEA-based optimization can identify a set of Pareto optimal solutions in simultaneously minimizing the building energy consumption, CO2 emission, and indoor thermal discomfort degree, arriving at the highest optimization rate of 13.43% under proper adjustment of certain features. (3) In the MOO task, the consideration of model and data uncertainty by prediction intervals and Monte-Carlo simulation can further increase the optimization rate by around 4.0% than the deterministic scenario, resulting in more desired strategies in optimizing the green building performance. In short, this paper enriches the area of green building development. For one thing, it raises the transparency and interpretability of machine learning to make the prediction more convincing. For another, it efficiently determines the passive and active design solutions along with the detailed profile of influential factors for green building design.

Analysis of the rate of working women's acceptance of partner violence and cultural reflections in Cypriot society.

This case study aims to measure the level of acceptance of violence among women and couples and to reveal the level of acceptance within and outside the families of women who have participated in working life. The concepts of anger and violence, physical, sexual, psychological, emotional, and economic violence, which are the sub-components of violence, violence in dating, and marital relations are examined separately according to Feminism and Social Learning Theory approaches. The Working Group was formed by applying questionnaires to 50 participants from the cities of Kyrenia, Güzelyurt, Lefke, Nicosia, and Magusa and determining the 20 participants with the highest level of acceptance of violence. The 11 people who agreed to the study were interviewed for a Dec of 1 week and 5 sessions ranging from 20 to 30 min. It is observed that women who are subjected to violence have a deep sense of helplessness and accept their helplessness, as well as those women resort to various passive solutions, such as silence and avoiding attitudes that make their partner angrier. The sense of helplessness, as a result of chronic depression, makes it inevitable to experience suicide cases. This study will be particularly important in terms of revealing the levels of domestic and non-family violence exposure and acceptance of violence by women who have participated in working life.

Combined passive and active flow control for fixed-wing micro air vehicles

This study presents the design, implementation, and assessment of a combined passive and active flow control technique with the aim of increasing the aerodynamic performance of fixed-wing Micro Air Vehicles (MAVs). Power consumption restrictions in MAVs support the choice of passive flow control solutions such as the use of a modified (tubercled) wing leading edge. This strategy successfully allows to delay and mitigate aerodynamic stall but detrimental effects are found at pre-stall operating conditions. In order to retrieve the lift-generation capabilities of the baseline wing at pre-stall, a subsidiary active flow control method making use of air blowing was designed and installed in the modified wing. Guidance to the selection of optimum settings was provided by experimental and computational analyses. The resulting hybrid flow control system demonstrated its effectiveness, thus producing generalized lift enhancements irrespectively of the attitude of the wing.

Analyzing the effects of passive design strategies on building ventilation performance and thermal comfort using simulation-based approach

One of the sustainable approaches to improving indoor thermal comfort and building ventilation efficiency, particularly in developing and populated countries, is to implement the optimum passive design solutions. However, the interaction between ventilation performance, indoor thermal comfort, and passive design features of buildings is scarcely studied in the domain of airflow modeling. Therefore, this study aims at assessing the ventilation performance and indoor thermal comfort with regards to passive design strategies, specifically, opening characteristics such as the Opening to Wall ratio (OWR) and Window to Wall ratio (WWR) in a Computational Fluid Dynamics (CFD) environment. The CFD simulations run is found pivotal for determining the spatial variation of Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) to gauge thermal comfort and the natural ventilation performance in terms of air change rate per hour (ACH). The proposed methodology is implemented in classroom spaces of an academic building located in a warm and humid region. In the study, a field investigation is carried out to collect precise temperature and air velocity data needed to validate the resulting CFD model. The findings show that increasing OWR and WWR percentages can enhance ventilation efficiency and indoor thermal comfort.

Saving Energy Through Improving Performance of Double Skin Facades: A Case Study Residential Building in Yazd

The building envelope is one of the most influential factors in energy consumption. Therefore, optimizing the facade of the building with new technologies is one of the most effective passive solutions to provide thermal comfort. The purpose of this research is to design a composite facade, which according to the two main driving forces; the pressure difference caused by the heat flow (air flow and wind force) and the insulation of the air, for a residential building with a typical plan of Yazd in the hot and dry climate of Iran. That can be used to reduce the heating and cooling load of the building. For this purpose, firstly, the effect of two types of two-skin facades - floor-to-floor and all-over two-skin facades - compared to the model without two-skin facades in cooling and heating energy consumption throughout the year was modeled and analyzed with Design Builder version 6.1 software. The results of the constructions show the possibility of reducing about 60% of cooling energy through the creation of air conditioning and 26% of heating energy through the creation of thermal insulation in the residential building simulation model throughout the year by means of two combined shells. The findings of this research lead to the creation of more efficient energy solutions by creating innovation and combining new technologies according to climatic conditions.

Evaluation of the Anticorrosion Properties of Passivation Solution Containing Different Metal Ions Coated on a Steel Surface

Evaluation of the Anticorrosion Properties of Passivation Solution Containing Different Metal Ions Coated on a Steel Surface