Search Results (1,075)

The high energy intensity of public buildings, especially those with HVAC systems, calls for advanced control strategies such as Model Predictive Control (MPC) to balance energy efficiency and thermal comfort. However, the performance of MPC relies critically on the accuracy and robustness of building cooling and heating load calculations, which remain challenging, particularly for buildings with complex dynamic characteristics. This study proposes a simplified modeling-based MPC approach and investigates the influence of three different load calculation methods on controller performance: a physics-driven white-box model, a data-driven black-box model, and a novel Closed-Loop Load Grey Model (CLLGM). Under identical outdoor conditions during summer cooling operation, the three controllers exhibit distinct performance disparities: although the proposed CLLGM-based controller only reduces the load prediction MAPE by 0.63% compared with the black-box model, it improves the temperature control stability index (TDI) by 80.43% and increases the comprehensive score from the MPC multi-objective optimization function by 16.55%. Its key advantage is that it can use on-site temperature measurements as feedback to correct the cooling load, making it better suited for simulation and computation in MPC. Full article

Climate change poses a growing threat to global health, yet healthcare systems contribute substantially to environmental harm through energy use, waste, and greenhouse gas (GHG) emissions. Among hospital departments, Intensive Care Units (ICUs) are among the most resource- and energy-intensive, generating disproportionately high greenhouse gas (GHG) emissions. The aim of this systematic review is to synthesize the literature on the environmental footprint of ICUs and to develop evidence-based strategies for creating sustainable ‘Green ICUs’ in accordance with the PRISMA 2020 guidelines. Peer-reviewed studies published between 2012 and October 2025 were identified through searches of major biomedical databases. Eligible studies examined the impacts of climate change on human health and infectious diseases, the ecological footprint of medical imaging and personal protective equipment, and sustainability interventions relevant to adult intensive care units. The environmental footprint of ICUs ranges from 88 to 178 kg CO₂-equivalents per patient per day. High electricity consumption, especially from heating, ventilation, and air-conditioning (HVAC) systems, along with single-use medical supplies and diagnostic imaging, drives this impact. Life-cycle assessments consistently demonstrate that reusable textiles, optimized energy systems, and rationalized diagnostic practices significantly reduce emissions and waste. Educational and behavioral interventions were effective in reducing unnecessary consumable use while maintaining patient safety. A “Green ICU” model integrating energy efficiency, sustainable procurement, waste reduction, and staff education can substantially reduce environmental harm without compromising quality of care. Full article

Accurate performance prediction of variable-speed centrifugal chillers is important for building energy optimization and the development of digital twins in HVAC systems. In practice, obtaining extensive operational data is costly, creating a prevalent “small-sample” dilemma under which conventional data-driven models are prone to overfitting with poor extrapolation capability. While recent Physics-Informed Neural Networks (PINNs) incorporate system-level thermodynamic constraints (e.g., COP definitions), they typically treat the centrifugal compressor as a thermodynamic black box, neglecting its inherent fluid dynamic characteristics; consequently, extrapolated predictions may be physically inconsistent or fall into unsafe operating regions such as compressor surge. To address this gap, this paper proposes an Aero-thermodynamic Physics-Informed Neural Network (Aero-PINN) that introduces three mechanisms into the PINN loss function: (1) dimensionless aerodynamic similarity mapping governed by affinity laws, (2) a surge boundary constraint that prevents non-physical extrapolations, and (3) an aerodynamic–electrical energy coupling validation. Experimental validation on 420 real-world variable-speed test records shows that the Aero-PINN achieves a COP RMSE of 0.04 and a COP MAPE of 0.3%, outperforming standard MLP and polynomial baselines. Moreover, 100% of the extrapolated operating points satisfy all fluid dynamic safety and energy efficiency constraints. This framework provides a reliable, physics-constrained small-sample learning approach, facilitating factory calibration and reduced-test digital modeling for chiller plants. Full article

Indoor air quality (IAQ) in educational buildings plays a critical role in the health, cognitive performance, and well-being of occupants. Aging university facilities often rely on outdated ventilation systems that are not designed to meet current demands or respond to dynamic occupancy levels. This study investigates the performance and feasibility of various advanced ventilation strategies in comparison to an existing balanced mechanical ventilation (BMV) system in a university classroom accommodating 100 students. Using a Dynamic Building Energy Simulation Program, simulations were conducted to evaluate IAQ (using CO₂ levels), energy consumption, and thermal comfort under three retrofitting scenarios: BMV, demand-controlled ventilation (DCV), and hybrid ventilation combining natural and mechanical airflow. The simulations indicate that DCV cuts annual HVAC energy use by 33% relative to the baseline, while the hybrid strategy achieves the greatest reduction of 42% and maintains CO₂ levels and thermal comfort within recommended limits. Although hybrid systems provide seasonal advantages, their complexity may limit applicability. In addition to technical analysis, this study also explores the financial and tax-related challenges associated with retrofitting ventilation systems in university buildings. Investment payback periods, operational costs, and potential tax incentives are discussed to evaluate economic viability. Overall, the endorse hybrid ventilation as the most cost-effective strategy where mixed-mode control is feasible, and DCV as a practical alternative for buildings unable to employ natural ventilation. Full article

This paper presents a design research study that develops a comprehensive conceptual framework for an integrated digital twin system for architectural heritage. The framework aims to explore mechanisms for real-time monitoring and the coupled regulation of structural health, microclimatic conditions, and energy performance. In the context of the ongoing global warming emergency, this framework supports climate adaptation strategies for heritage sites. It enables a fully coordinated operational process encompassing real-time sensing, predictive analysis, coupled control, and decision support. In the structural dimension, the framework is designed to utilise sensors to monitor and warn against cracks, settlement, and deformation, whilst integrating models to analyse stress conditions. In the microclimate dimension, the study envisages predicting and adjusting HVAC and lighting systems based on environmental parameters and footfall monitoring data via algorithms, with the aim of balancing occupant comfort with humidity control and mould prevention. Regarding energy, the framework optimises equipment operation through smart metering and algorithms and we propose a modelling tool for the quantitative assessment of energy-saving retrofit effects. Furthermore, the framework incorporates the establishment of an open-access dataset covering structural, microclimate, and energy use data, providing data standards and a foundation for subsequent empirical research. Full article

The built environment in the EU accounts for 40% of the total energy consumption and 36% of the total greenhouse gas emissions. To address the inefficiency of existing buildings, renovation could reduce their total energy consumption by 5–6% and lower carbon dioxide emissions by approximately 5%. A retrofit solution for existing buildings involves the use of lightweight prefabricated systems, some of which include integrated HVAC components that are able to enhance their functionality. Indeed, such prefabricated facade elements with integrated HVAC systems can represent a minimally invasive method for reducing the energy consumption of an existing building. To assess the potential of this approach, a full-scale mock-up of a prefabricated timber facade with integrated HVAC system was tested at the Facade System Interactions Lab (FSIL) of Eurac Research, Bolzano. The experimental data were used to develop a calibrated and validated 3D finite element model in COMSOL Multiphysics. The validated model was used to evaluate the facade’s thermal performance under standard heating conditions through a proposed equivalent thermal transmittance indicator (U_eq). Results show that the active facade achieves 0.07 W m⁻² K⁻¹, compared to 0.21 W m⁻² K⁻¹ for the passive facade with identical materials but without active components. Full article

The decarbonization of the building stock by 2050, as set by the European Green Deal, calls for an unprecedented wave of energy renovations. Yet, reliable evidence on the real costs and performance of retrofit interventions remains scarce. This paper presents the results of a large-scale technical and economic analysis conducted on 34 residential buildings, all renovated under a national Italian programme supporting energy efficiency improvements. For each building, pre- and post-renovation energy performances were assessed using standardised procedures, while detailed investment cost data were collected for all implemented measures, including envelope insulation, HVAC system upgrades, and renewable integrations. By combining these datasets, the study evaluates the actual cost-effectiveness of different retrofit strategies, revealing the true financial effort required to achieve substantial energy improvements. The results highlight both the opportunities and limitations of current approaches, showing a significant gap between theoretical models and real outcomes. The findings contribute to the European debate on the economic sustainability of deep renovation policies. Full article

Heating, Ventilation, and Air Conditioning (HVAC) systems used in modern buildings are among the largest contributors to energy consumption. Therefore, it is necessary to carefully balance between thermal comfort and energy efficiency when operating these systems. This study proposes a Symbolic Discrete Controller Synthesis (SDCS) approach for HVAC management that simultaneously enforces comfort-band constraints at the supervisory level and optimizes energy efficiency. Unlike traditional continuous controllers tuned per zone, the proposed method coordinates zone-level actuation through discrete power levels and node-level constraints (including an aggregate peak cap), exploiting thermal inertia to redistribute service over time without increasing comfort-band violations. Experimental evaluations on a multi-zone building model demonstrate that the SDCS approach provides comparable small comfort violations and provides superior energy savings when benchmarked against Model Predictive Control (MPC) and traditional Proportional-Integral-Derivative (PID) controllers. These results highlight the potential of SDCS as a robust and scalable solution for sustainable building management and energy-aware HVAC coordination in multi-zone buildings. Full article

This review paper discusses the technological advancements and innovative strategies of heating, ventilation, and air conditioning (HVAC) systems for buildings. Buildings are a major contributor to energy consumption and greenhouse gas (GHG) emissions, representing about 35% of global final energy use and 26% of energy-related GHG emissions. In Canada, the building sector accounts for roughly 31% of energy demand and 18% of total GHG emissions, with HVAC systems responsible for 40–50% of this energy use. The current challenges, emerging trends, and future prospects for HVAC and related technologies are systematically reviewed to promote sustainability, affordability, and resilience in buildings. The literature scanning begins with an overview of the prevailing energy scenario in buildings, HVAC technologies, and other regulatory and policies. The paper thoroughly examines the critical role of HVAC systems in reducing energy consumption, minimizing environmental impact, improving building affordability and enhancing occupant health and productivity. It discusses emergent technological opportunities, energy efficiency measures, sensors, smart controllers, Internet of Things (IoT) and AI-based technologies. The paper highlights the barriers to adopting new technologies and strategies. It provides an evolving topography of HVAC technologies, their current state and emerging directions to tackle environmental challenges, including net zero energy and zero carbon building goals. The review suggests that while there are promising advancements in HVAC technology, further research and practical demonstrations of innovative solutions are necessary to maintain the momentum in building modernization efforts. Full article

Hydrogen fuel cell buses (HFCBs) offer a promising zero-emission solution for sustainable public transportation. However, the high energy consumption of auxiliary systems, particularly heating, ventilation and air conditioning (HVAC), significantly impacts overall vehicle efficiency by increasing hydrogen consumption. This study investigates the influence of the HVAC load on the energy efficiency of hydrogen fuel cell buses under different driving conditions and seasonal ambient temperatures. Using a MATAB/Simulink-based simulation framework, the interaction between the fuel cell system, battery dynamics, and HVAC operation is modeled to quantify energy consumption under urban, highway and mixed driving conditions. Simulation was conducted at 7 °C and 35 °C with varying HVAC load levels of 50% and 100% to represent harsh winter and summer conditions. Results demonstrated that HVAC operation can account for a substantial portion of total energy consumption, reducing the vehicle range and fuel cell efficiency. Full article

Phase change materials (PCMs) have emerged as a key enabler of high-performance, low-carbon buildings through latent heat-based thermal energy storage. This paper presents a systematic and critical synthesis of advances in PCM technologies for building applications published between 2022 and 2025, analyzing over 300 peer-reviewed studies to evaluate thermal performance, economic viability, environmental impact, and climate adaptability across three integration approaches: passive, active, and hybrid systems. The studies analyzed show that passive envelope integration employing macroencapsulated or form-stable PCMs in walls, roofs, and glazing is reported to deliver 15–45% energy savings with payback periods of 8–15 years, primarily through enhanced thermal inertia and indoor temperature stabilization. Active systems, which couple PCMs with HVAC, heat pumps, or air handling units, are found to achieve 20–40% energy reductions and shorter payback periods (3–8 years) by enabling load shifting, peak shaving, and improved coefficient of performance (COP). Hybrid configurations integrating passive and active strategies with AI-driven control demonstrate, in the literature, the highest potential, with reported energy savings of up to 50%, though they entail greater complexity and capital cost. The review further highlights material-level innovations, including ternary composite PCMs, bio-based alternatives, and nano-enhanced formulations that address intrinsic limitations such as low thermal conductivity (0.1–0.3 W/m·K for organics) and cycling instability. Despite significant progress, critical gaps persist in standardized testing protocols, long-term field validation, comprehensive lifecycle assessments, and real-world scalability, particularly in tropical and cold climates. By bridging material science, building physics, and energy system engineering, this work provides a forward-looking roadmap to accelerate the deployment of PCM-based solutions in the global decarbonization of the built environment. Full article

As the electrification of the automotive industry accelerates, the importance of small-scale motors used in applications such as HVAC systems and water pumps is growing. To design small motors that exhibit high efficiency and high output within limited spaces, applying axial flux motors (AFMs) instead of conventional radial flux motors (RFMs) can maximize the power density within the same volume, offering advantages in both weight reduction and miniaturization. This study proposes an optimized end-turn layout design to mitigate back-EMF imbalance in AFMs utilizing PCB stators. Optimization results demonstrated that the structure employing a non-adjacent end-turn layout with equalized average end-turn heights (BCAACB type) exhibited the best performance in terms of average resistance and phase resistance variance, effectively mitigating back-EMF imbalance. The validity of the optimized end-turn structure was verified through finite element analysis (FEA). The analysis confirmed that the motor’s back-EMF balance was improved, and the magnitude of phase resistance was reduced. This reduction led to lower copper loss, thereby increasing overall efficiency. Furthermore, the variance in resistance for each phase was minimized, resulting in enhanced electrical balance. The results of this study are expected to contribute to enhancing the applicability of PCB stators in small motor design. Full article

Increasing energy demand, decarbonization commitments, and growing expectations for thermal comfort are driving the need for more adaptive and efficient climate control in residential buildings. This review synthesizes contemporary intelligent HVAC control strategies, including model-predictive control (MPC), deep reinforcement learning (DRL), data-driven forecasting, and hybrid approaches. Following PRISMA guidelines, a set of studies published between 2010 and 2025 was systematically screened and analyzed to identify the dominant methodological trends, data requirements, implementation architectures, and evaluation practices reported in the literature. This review highlights how these methods differ in modeling assumptions, computational complexity, robustness to uncertainty, and suitability for residential environments characterized by stochastic occupancy and heterogeneous building stock. In addition, we examine enabling technologies such as sensing infrastructures, pricing signals, and embedded computation, as well as barriers to real-world deployment, including data availability, interpretability, and integration with existing building systems. The findings provide a consolidated framework for understanding the capabilities and limitations of intelligent HVAC control and outline research gaps that remain for achieving scalable, user-centered, and energy-efficient operation in residential buildings. Full article

The design of thermal strategies applied in buildings based on the use of renewable energies can play an important role in the development of a built environment that is better adapted to the climate. This paper is focused on the application of a renewable solar energy system coupled with a Heating, Ventilation and Air-Conditioned (HVAC) system to promote occupants’ thermal comfort (TC) and indoor air quality (IAQ) in buildings during heating season. In the building thermal design, a building thermal dynamic model is used to calculate the temperatures of the opaque and transparent building surfaces, the temperature of the water supply ducts, the TC level and the IAQ level, among other variables. The TC conditions of the occupants were evaluated using the Predicted Mean Vote index, commonly used in the literature in similar studies. IAQ was assessed by the usual carbon dioxide concentration in environments where most of the pollution is of human origin. The numerical study was carried out in a virtual residential building consisting of two floors and seven compartments. The building is occupied at night and at midday. Two cases were studied, considering, respectively, the non-use and use of the solar HVAC system. The solar HVAC system consists of solar water collectors, installed above the roof area, and thermo-convector heat exchangers, installed inside each occupied space. The results show that the application of this solar HVAC system in a Mediterranean-type climate is able to guarantee, during occupancy, acceptable TC levels in three compartments and near acceptable TC levels in one compartment. Regarding IAQ, acceptable level can be achieved throughout the day. Full article

The current global context, characterized by climate change and increased indoor occupancy, has necessitated prolonged daily operating hours for ventilation systems. Coupled with rising living standards, these factors have elevated occupants’ expectations for Indoor Environmental Quality (IEQ), driving a demand for quieter equipment which is a significant challenge for HVAC engineering. This study evaluates the acoustic attenuation performance of various casing constructions to quantify the impact of sheet metal stiffness compared to insulation thickness. Experimental measurements of the Radiated Sound Power Level (LwA) were conducted on a heat recovery unit across octave bands from 63 Hz to 16,000 Hz, ensuring a measurement uncertainty within ±0.5 dB as per ISO 3741 precision requirements. The methodology involved testing multiple enclosed configurations against a reference open-top unit, varying mineral wool insulation thickness from 40 mm to 100 mm (with optional 25 mm linings) and inner sheet metal thickness between 0.8 mm and 2.0 mm. The results indicate that enclosing the unit significantly reduced radiated sound power levels compared to the exposed reference. While the standard configuration with 50 mm insulation yielded 49.8 dBA, modifying the casing structure generated superior attenuation. Notably, a configuration utilizing a 2.0 mm inner sheet resulted in a radiated sound power level of 46.9 dBA, a result found to be statistically significant (p < 0.05) when compared to the baseline. This performance is statistically comparable to the 46.7 dBA recorded for the maximum insulation assembly, confirming the validity of structural stiffening as an equivalent alternative to bulk insulation. Consequently, the increased panel stiffness achieved approximately 94% of the attenuation efficiency provided by the thickest insulation option. The data demonstrates that increasing panel stiffness effectively reduces transmission, offering performance levels comparable to significantly thicker insulation layers. The study concludes that optimizing casing stiffness represents a superior strategy for noise control in high-density residential applications, as it decouples acoustic performance from the unit’s external dimensions, offering a high-attenuation solution that preserves a compact spatial footprint. Full article