Search Results (304)

Urban environments, particularly university campuses, are increasingly exposed to thermal discomfort due to the Urban Heat Island (UHI) effect and intense solar radiation. This study evaluates the effectiveness of passive and hybrid cooling strategies, specifically sun-sail shading and mist cooling, in enhancing outdoor thermal comfort (OTC) in a university courtyard. The Van Dyck courtyard at the American University of Beirut, located on the East Mediterranean coast, was selected due to its heavy use between 10 am and 2 pm during summer, when ambient temperatures ranged between 32 and 36 °C and relative humidity between 21 and 33%. Thermal variations across four seating areas were analyzed using ENVI-met, a high-resolution microscale model validated against on-site data, achieving Mean Absolute Percentage Errors of 4% for air temperature and 5.2% for relative humidity. Under baseline conditions, Physiological Equivalent Temperature (PET) exceeded 58 °C, indicating severe thermal stress. Several mitigation strategies were evaluated, including three shading configurations, two mist-cooling setups, and a combined system. Results showed that double-layer shading reduced PET by 17.1 °C, mist cooling by 1.2 °C, and the combined system by 20.7 °C. Shading minimized radiant heat gain, while mist cooling enhanced evaporative cooling, jointly bringing thermal sensations closer to slightly warm–comfortable conditions. These cooling interventions also have sustainability value by reducing dependence on mechanically cooled indoor spaces and lowering campus air-conditioning demand. As passive or low-energy measures, shading and mist cooling support climate-adaptive outdoor design in heat-stressed Mediterranean environments. Full article

To address the poor thermal insulation and freeze resistance of rural outdoor toilets in cold regions—key obstacles to achieving the UN Sustainable Development Goal (SDG) 6.2 and popularizing rural sanitary toilets—this study fills the literature gap of insufficient research on passive solar heating systems tailored for rural toilets in cold climates. Using TRNSYS simulation, Plackett–Burman key factor screening, single-factor experiments, and Box–Behnken response surface methodology, we optimized the system with building envelope thermal parameters and Beijing’s typical meteorological year data as inputs, taking January’s average indoor temperature as the core evaluation index. Results indicated six parameters (solar wall area, air cavity thickness, vent area ratio, vent spacing, exterior wall insulation thickness, and heat-gain window-to-wall ratio) significantly influence indoor temperature (p < 0.05). The optimal configuration was as follows: solar wall area 3.45 m², window-to-wall ratio 30%, exterior wall insulation thickness 200 mm, vent spacing 1800 mm, air cavity thickness 43 mm, and vent area ratio 5.7%. Post-optimization, the average temperature during the heating season reached 10.81 °C (79.5% higher than baseline), with January’s average, maximum, and minimum temperatures at 7.95 °C, 20.47 °C, and −1.42 °C, respectively. This solution effectively prevents freezing of flushing fixtures due to prolonged low temperatures, providing scientific support for the application of passive rural toilets in China’s cold regions. Full article

This study proposes a novel multi-porous heat exchanger (MPHEX) as a passive, sustainable alternative to variable refrigerant flow (VRF) air conditioning systems, addressing the growing environmental burden of cooling demand. Through high-fidelity Lattice Boltzmann Method simulations of coupled heat and fluid transport, the MPHEX design is optimized to minimize exergy destruction. A case study for Tunisian conditions demonstrates that permeability optimization, when combined with solar-assisted preheating, reduces total exergy destruction by over 60% and increases the coefficient of performance (COP) by up to 20%, all while eliminating active mechanical regulation. The numerical results confirm strong experimental feasibility, positioning the MPHEX as a scalable, low-energy, and low-maintenance cooling solution for sun-rich regions. Full article

To scientifically address the low productivity issue of traditional solar desalination systems, the current review intends to investigate the effect of design changes and performance improvement of solar stills with external and internal condensers. This review highlights that elements such as coolant techniques, the geometry of the condenser, and material features (e.g., nanofluids or surfaces of wettability) have a pivotal impact on maximising output. The results show that the combination of external condensers in solar stills is remarkably effective, where the efficiency ranges between 24% and 165% in distillate yield depending on the design modifications, which include the use of nanofluids, reflectors, and phase change materials (PCMs). In this regard, internal condensers explicitly display significant performance advances, with water production improvements of more than 150% in improved stepped designs and 60% in capillary film designs. To guarantee the maximum production of fresh water, this review proposes a number of adjustments to elevate the overall performance of solar stills, such as condensers with enhanced mechanisms of heat transfer or passive cooling strategies, which enable solar stills to be more practical in achieving the sustainable desalination of water across a wide range of climatic regions. Indeed, the enhancement of the efficiency of solar desalination technologies would support the United Nations Sustainable Development Goal 6 (Clean Water and Sanitation), providing access to safe and affordable drinking water for all. Full article

This study investigates the architectural design factors that influence the adoption of eco-friendly solar energy technologies for the partial retrofitting of older residential buildings in densely populated urban areas in a developed country. This research study employs a mixed-method approach, combining quantitative and qualitative frameworks along with comparative analysis and utilizing standard fact-finding procedures to examine the adoption of eco-friendly energy systems and their integration into existing infrastructures. The feasibility study, complemented by a detailed technical investigation, identifies several significant factors affecting the intention to undertake sustainable solar retrofitting. These factors include performance expectations, facilitating conditions, motivation, price/value perceptions, and environmental knowledge. This study highlights key constraints and tipping points that influence households’ decisions to implement light retrofitting and explores three distinct system configurations to enhance cost-effectiveness. The insights gained from this research study are valuable for a range of stakeholders, including homeowners, designers, technology developers and manufacturers, real estate developers, builders, and government entities. The findings guide effective strategies to encourage eco-friendly retrofits through both passive and active systems, contributing to future environmental sustainability goals. This research study addresses a gap in the literature regarding the environmental sustainability of solar retrofitting in densely populated urban settings in developed countries. Addressing the pressing issue of global warming contributes to advancing sustainable solar housing technologies and provides a comprehensive foundation for the early stages of the design process. Full article

This study presents the design and implementation of a prototype dual-function photovoltaic window system that integrates flexible solar panels for dynamic shading and a compact lithium battery for local energy storage. The methodology involves developing an experimental setup where translucent, flexible photovoltaic panels are retrofitted onto a standard residential window. The system is connected to a charge controller and a small-capacity lithium-ion battery pack. Key performance metrics, including solar irradiance, power generation efficiency, reduction in thermal transmittance, and battery state of charge, are continuously monitored under varying real-world environmental conditions. The integrated panels can significantly reduce solar heat gain, thereby lowering indoor ambient temperature and reducing the building’s cooling load. Simultaneously, the system will generate sufficient electricity to be stored in the lithium battery, providing a self-contained power source for low-draw applications such as lighting or charging personal devices. This research highlights the viability of developing cost-effective, multi-functional building components that transform passive architectural elements into active energy-saving and power-generating systems in terms of green environment goals. Full article

Global freshwater scarcity continues to escalate due to pollution, climate change, and population growth, making innovative sustainable desalination technologies increasingly vital. Solar stills offer a simple and eco-friendly method for freshwater production by utilizing renewable energy, yet their low productivity remains a major limitation. This study experimentally evaluates and quantifies several established enhancement techniques under real climatic conditions to improve evaporation and condensation efficiency. The integration of porous materials, such as black rocks, significantly improves thermal energy storage and management by retaining absorbed heat during the daytime and releasing it gradually, resulting in an average 30% increase in daily distillate production (SD = 6 mL). Additionally, forced convection using small fans enhances humid air removal and evaporation rates, increasing the average yield by approximately 11.4% (SD = 2 mL). Optical concentration through lenses intensifies solar irradiation on the evaporation surface, achieving the highest performance with an average 50% improvement in water output (SD = 5 mL). The incorporation of Phase Change Materials (PCM) is further proposed to extend thermal stability during off-sunshine hours, with materials selected based on a melting point range of 38–45 °C. To minimize nocturnal heat loss, future designs may integrate radiative cooling materials for passive night-time condensation support, by applying a radiative cooling coating to the condenser plate to enhance passive heat rejection to the sky. Overall, the validated combined use of renewable energy-driven desalination, thermal storage media, and advanced strategies presents a practical pathway toward high-efficiency solar stills suitable for sustainable buildings and decentralized water supply systems in arid regions. Full article

Given that building energy consumption accounts for a significant portion of total energy consumption, passive building technologies have demonstrated tremendous potential in addressing energy crises and the greenhouse effect. As a passive building technology, the Trombe wall (TW) can utilize solar energy to enhance building energy efficiency. However, due to their reliance on direct solar radiation patterns and limited thermal inertia characteristics, traditional TW systems exhibit inherent efficiency limitations. By integrating phase change materials (PCMs), TW systems can achieve high thermal storage performance and temperature control flexibility within a narrow temperature gradient range. By integrating functional materials, PCM-TW systems can be made multifunctional (e.g., through thermal catalysts for air purification). This has significant engineering implications. Therefore, this paper systematically reviews the development timeline of TWs, focusing on the evolution of PCM-TW technology and its performance. Based on this, the paper particularly emphasizes the roles of three key operational parameters: structural characteristics, thermophysical material design, and operational management. Importantly, through comparative analysis of existing systems, this paper identifies the shortcomings of current PCM-TW systems and proposes future improvement directions based on the review results. Full article

This article presents the accumulated technical and scientific knowledge from energy performance upgrade work in emblematic and essential municipal and public buildings in Crete and the Greek islands, such as the Venetian historical building Loggia, which is used as the Heraklion City Hall, the Natural History Museum of Crete, Pancretan Stadium, the municipal swimming pool of the municipality of Minoa Pediadas, the indoor sports hall in Leros, primary schools, high schools and a cultural center. Each one of the aforementioned buildings has a distinct use, thus covering almost all different categories of municipal or public buildings and facilities. The applied energy performance upgrade process in general terms is: (1) Mapping of the current situation, regarding the existing infrastructure and final energy consumption. (2) Formulation and sizing of the proposed passive measures and calculation of the new indoor heating and cooling loads. (3) Selection, sizing and siting of the proposed active measures and calculation of the new expecting energy sources consumption. (4) Sizing and siting of power and heat production systems from renewable energy sources (RES). Through the work accomplished and presented in this article, practically all the most technically and economically feasible passive and active measures were studied: insulation of opaque surfaces, opening overhangs, natural ventilation, replacement of openings, daylighting solar tubes, open-loop geo-exchange plants, refrigerant or water distribution networks, air-to-water heat pumps, solar thermal collectors, lighting systems, automation systems, photovoltaics etc. The main results of the research showed energy savings through passive and active systems that can exceed 70%, depending mainly on the existing energy performance of the facility. By introducing photovoltaic plants operating under the net-metering mode, energy performance upgrades up to zero-energy facilities can be achieved. The payback periods range from 12 to 45 years. The setup budgets of the presented projects range from a few hundred thousand euros to 7 million euros. Full article

The intensification of thermal extremes increases the need for strategies that protect indoor comfort and reduce the energy demand of active systems. This study employs EnergyPlus dynamic simulations to evaluate how passive thermal design solutions for heating and cooling can minimize indoor temperature fluctuations. The analysis covers multiple locations to identify the most effective techniques for improving indoor thermal performance and energy efficiency. Results demonstrate that passive thermal strategies offer a sustainable and efficient approach to adapting buildings to extreme temperature variations, thereby reducing dependence on mechanical systems. The greatest reduction in energy demand is achieved by increasing the envelope’s thermal mass, particularly in hot and temperate climates. Enhanced insulation and green roofs are more effective in cold and humid climates. In addition, solar control measures, such as external shading and reduced glazing areas, help lower indoor temperatures in high-thermal-radiation regions. Full article

Solar photovoltaic systems now produce the lowest-cost electricity in history and coupling with agriculture in agrivoltaics increases crop yields. This indicates solar will continue to experience explosive growth. Concerns exist, however, about the long-term end-of-life decommissioning of solar farms. For example, due to fossil fuel decommissioning mismanagement, Alberta is inundated with orphaned oil and gas wells that have remediation cost estimates of CAD$100 billion. Such comparisons have prompted preemptive legislation targeting solar farms, but is the fear justified? This study addresses this question by (1) analyzing warranted and actual lifespans of key agrivoltaic system components, (2) experimentally measuring microclimate impacts of two agrivoltaic arrays (fully powered with electricity extraction and unpowered to simulate post-inverter-failure conditions) and (3) quantifying agrivoltaic yield gains based on crops previously shown to respond positively to such conditions. Experimental results indicate that unpowered photovoltaic shading not only moderates soil temperatures but also enhances soil moisture conservation relative to unshaded conditions. This study demonstrates that agrivoltaic systems, even after the cessation of power generation, can continue to deliver meaningful agronomic and economic value through passive shading and policy frameworks should adapt to this dual-use reality. Integrating agronomic co-benefits into decommissioning policy supports long-term farm productivity and climate resilience. Full article

The lack of freshwater and the low efficiency of the traditional solar stills have led to the search to find a technology that can enhance desalination by use of vacuum-enhanced solar still technology. This review intends to investigate the impact of integrating a vacuum into solar stills, which include vacuum membrane distillation (VMD), nanoparticle-enhanced solar stills, multi-effect/tubular solar stills, geothermal integration and parabolic concentrator solar stills. The most important findings show that the productivity improves greatly: vacuum-assisted solar stills give up to 133.6% more product using Cu₂O nanoparticles, and multi-effect tubular stills under vacuum (40−60 kPa) show a doubling in freshwater productivity (7.15 kg/m²) in comparison to atmospheric operation. Geothermal cooling and vacuum pump systems show a 305% increase in productivity, and submerged VMD reached 5.9 to 11.1 kg m⁻² h⁻¹ with solar heating. Passive vacuum designs further reduce the energy used down to a specific cost, using as little as USD 0.0113/kg. Nevertheless, membrane fouling, initial cost, and the complexity of the system can still be termed as the challenges. This review highlights the significance of vacuum-enhanced solar stills to address the critical issue of freshwater scarcity in arid regions. The integration of vacuum membrane distillation, nanoparticle and heat recovery into vacuum-enhanced solar stills enabled us to improve the economic feasibility. We conclude that vacuum technologies significantly boost the efficiency and economic feasibility of solar desalination as a potential approach to sustainable desalination. Specifically, these inventions will contribute to providing a renewable and cost-effective solution for freshwater production. Further investigations are required to overcome the existing challenges, such as system complexity and membrane fouling, to effusively comprehend the efficacy of vacuum-enhanced solar stills to ensure sustainable water management. Full article

This study assessed the impact of 39 active and passive energy efficiency measures on the energy demand of a prototype dwelling, modeled through parametric simulations in DesignBuilder across nine climatic zones in Chile, classified according to the Köppen system. Each measure was evaluated individually (single-measure scenarios); three variation levels were evaluated to quantify their relative influence on energy demand. Results indicate that passive strategies are more effective in cold and humid climates, where increasing wall insulation thickness reduced energy demand by up to 45%, and improving airtightness achieved a 43% reduction. In contrast, in tundra climates or areas with high thermal variability, some measures, such as green façades or overhangs, increased energy demand by up to 49% due to the loss of useful solar gains. In desert climates, characterized by high diurnal temperature variation, thermal mass played a more significant role: high-inertia walls without additional insulation outperformed lightweight EPS-based solutions. The findings suggest that measure selection must be climate-adapted, prioritizing high-impact passive strategies and avoiding one-size-fits-all solutions. This work provides quantitative evidence to inform residential thermal design and support climate-sensitive energy efficiency policies. This study delivers a single-measure comparative atlas; future research should integrate multi-measure optimization together with comfort/cost metrics. Full article

This research investigates the integration of green cores as central biophilic elements in residential architecture, proposing a climate-responsive design methodology grounded in architectural optimization. The study begins with the full-scale refurbishment of a compact urban apartment, wherein interior partitions, fenestration and material systems were reconfigured to embed vegetated zones within the architectural core. Light exposure, ventilation potential and spatial coherence were maximized through data-driven design strategies and structural modifications. Integrated planting modules equipped with PAR-specific LED systems ensure sustained vegetation growth, while embedded environmental infrastructure supports automated irrigation and continuous microclimate monitoring. This plant-centered spatial model is evaluated using quantifiable performance metrics, establishing a replicable framework for optimized indoor ecosystems. Photosynthetically active radiation (PAR)-specific LED systems and embedded environmental infrastructure were incorporated to maintain vegetation viability and enable microclimate regulation. A programmable irrigation system linked to environmental sensors allows automated resource management, ensuring efficient plant sustenance. The configuration is assessed using measurable indicators such as daylight factor, solar exposure, passive thermal behavior and similar elements. Additionally, a post-occupancy expert assessment was conducted with several architects evaluating different aspects confirming the architectural and spatial improvements achieved through the refurbishment. This study not only demonstrates a viable architectural prototype but also opens future avenues for the development of metabolically active buildings, integration with decentralized energy and water systems, and the computational optimization of living infrastructure across varying climatic zones. Full article

Pipeline systems are essential across various industries for transporting fluids over various ranges of distances. A notable application is natural circulation through thermo-syphoning, driven by temperature-induced density variations that generate fluid flow in closed loops. This passive mechanism is widely employed in sectors such as process engineering, oil and gas, geothermal energy, solar water heaters, fertilizers, etc. Natural Circulation Loops eliminate the need for mechanical pumps. While this passive mechanism reduces energy consumption and maintenance costs, maintaining stability and efficiency under varying operating conditions remains a challenge. This study investigates thermo-syphoning in a rectangular closed-loop system and develops optimal control strategies like using a Linear Quadratic Regulator (LQR) and Model Predictive Control (MPC) to ensure stable and efficient heat removal while explicitly addressing physical constraints. The results demonstrate that MPC improves system stability and reduces energy usage through optimized control actions by nearly one-third in the initial energy requirement. Compared to the LQR and unconstrained MPC, MPC with active constraints effectively manages input limitations, ensuring safer and more practical operation. With its predictive capability and adaptability, the proposed MPC framework offers a robust, scalable solution for real-time industrial applications, supporting the development of sustainable and adaptive natural circulation pipeline systems. Full article