Search Results (311)

This work uses battery-coupled power electronic converter systems and distributed backstepping controllers to improve the reliability of electrical distribution networks. The motivation is to prevent blackouts such as the 28 April 2025 outage in Spain, Portugal, and the south of France. It is now accepted that a rapid rise in solar power injections caused AC overvoltage above grid code limits, triggering photovoltaic (PV) park disconnections as overvoltage self-protection. This case study considers near-Zero-Energy Buildings (nZEBs) connected to the Madeira Island isolated microgrid, where PV power installation is increasing excessively. The main university facility will be upgraded as an nZEB, using roughly 3000 m² of unshaded rooftops plus coverable parking areas to install PV panels. Optimizing the profits/energy cost ratio, a PV power system of around 560 kW can be planned, and the Battery Storage System (BSS) energy capacity can be estimated. The BSS is connected to the university nZEB via backstepping-controlled multilevel converters to manage PV and BSS, enabling the building to contribute to voltage and frequency regulation. Distributed multilevel converters inject renewable energy into the medium-voltage network, regulating active and reactive power to prevent overvoltages shutting down the PV inverters. This removes sustained overvoltage and maximizes PV penetration while augmenting AC grid reliability and resilience. When there is excess solar power and reactive power is insufficient to reduce voltage, controllers slightly curtail PV active power to eliminate overvoltage, maintaining operation with minimal revenue loss while preventing long interruptions, thereby improving grid reliability and power quality. Full article

The decarbonization of the residential sector is a critical component of the European Green Deal, particularly in transition economies like Poland. This study proposes a comprehensive techno-economic optimization of a deeply retrofitted single-family house aiming for net-zero energy building (NZEB) status. The research specifically focuses on the Polish coastal climate zone, characterized by distinct humidity, wind, and temperature profiles compared to inland regions, which significantly influence the efficiency of air-to-water heat pumps (ASHP). Based on a real-world energy audit, the study simulates the synergy between a deep thermal envelope upgrade and a hybrid system comprising an ASHP, photovoltaics (PV), and battery energy storage (BES). This paper presents a detailed economic analysis of such hybrid systems under the new Polish ‘net-billing’ prosumer mechanism. The study evaluates the impact of electricity tariff structures (flat-rate G11 vs. time-of-use G12w) on the investment’s profitability. By calculating key performance indicators—including the levelized cost of energy (LCOE), net present value (NPV), and self-sufficiency ratio (SSR)—the research assesses various system configurations. The initial evaluation indicates that while deep retrofitting significantly reduces heating demand, integrating battery storage plays a critical role in enhancing economic returns under the net-billing framework. The analysis demonstrates that the optimized hybrid system (9.0 kWp PV + 10 kWh BESS) achieves an average annual self-sufficiency ratio (SSR) of 49.8% and reduces the non-renewable primary energy (EP) indicator to 0.0 kWh/(m²·year). Economically, the investment yields a positive NPV of €3194, an IRR of 5.25%, and a LCOE of €0.184/kWh, which is 34% lower than projected grid prices. Furthermore, switching to a time-of-use tariff (G12w) generates an additional 11% (€139) in annual savings. These quantitative findings provide actionable guidelines for policymakers and investors, confirming the financial viability and environmental benefit (annual reduction of 6.12 MgCO₂) of NZEB standards in coastal areas. Full article

Thermal bridges at window installations significantly influence the energy performance and indoor comfort of buildings, particularly in nearly zero energy buildings (nZEB). This study investigates the impact of window mounting-position on thermal-bridge intensity at window-to-wall junctions using finite element method (FEM) simulations of representative junction configurations. Mounting depth, frame alignment relative to the insulation layer, and junction detailing were systematically varied to quantify their effect on linear thermal transmittance (ψ-values) and internal-surface temperatures. The results show that relatively small changes in mounting position can markedly reduce thermal-bridge effects; the most effective strategy combines installing the window within the insulation layer at an optimal depth of 7–12 cm. Across the studied configurations, ψ decreased from traditional installation values of 0.27 W/(m·K) to 0.02 W/(m·K) for installation in the insulation layer, and with frame overlap and frame extenders, the ψ-value can be further reduced, reaching 0.005 W/(m·K) in the best case. Applying external insulation increases the minimum internal-surface temperature by at least 2 °C compared with cases without frame covering. In the case study of a historical building retrofitted to Passive House (PH) standard, installing windows in the insulation layer reduced annual heating demand from 32 kWh/m² to 24 kWh/m². The additional investment is economically justified, with a simple payback period of about 25 years, decreasing to around 20 years assuming a 3% annual increase in energy prices. These findings demonstrate that optimised window positioning is an effective and economically viable measure to improve the energy performance, durability, and sustainability of high-performance buildings. Full article

Since 2021, the design and construction of nearly zero-energy buildings (nZEBs) have been mandatory for European Union Member States. Subsequent requirements for the building sector, characterized by high energy demand and significant environmental impact, include the minimization of carbon footprint and the introduction of climate-neutral building standards. The carbon footprint comprises both embodied emissions related to materials and construction processes and operational emissions resulting from building use. This paper analyzes both types of carbon footprint using a residential building that is part of an experimental housing estate consisting of 44 semi-detached buildings as a case study. Analyses of energy consumption optimization and carbon footprint reduction were conducted at both the individual building scale and the scale of the entire housing complex. The estate was developed in two stages. In the first stage (completion of construction in 2024), the primary criterion for technology selection was investment cost while maintaining compliance with applicable technical and building regulations. Prior to the implementation of the second stage, the investor conducted a social participation process in the form of a survey among future users. The survey addressed environmental aspects of the newly designed buildings and enabled the selection of materials, technologies, and energy sources aligned with user preferences. The results indicate that environmental aspects are important to future users; however, investment decisions are strongly balanced against economic factors. At the same time, the energy analyses demonstrate that a substantial reduction in the operational carbon footprint can be achieved, enabling a significant progression toward climate neutrality, both at the level of individual buildings and across the entire housing estate. Social participation, therefore, becomes an important element in the pursuit of climate neutrality in buildings. However, it must be taken into account already at the design stage. The results of the analyses carried out in the article showed that, taking into account public participation in the design process and user recommendations, the selected optimal variant (W5) allows for a reduction in the EP index by over 90% compared to the variant based on standard low-cost solutions (W0) (EP (W0) = 243.64 kWh/(m² year); EP (W5) = 18.42 kWh/(m² year). In terms of the embodied carbon footprint, the optimal option W5 allows for a reduction of over 30% in the embodied carbon footprint of the building structure (W0—51,585.32 [kgCO₂e]; W5—35,537.87 [kgCO₂e]). The optimal variant indicated by users (W5) allows for a reduction in the operational carbon footprint by approximately 80% compared to the basic variant (W0): W0—604,189.50 [kgCO₂e/kWh]; W5—247,402.0 [kgCO₂e/kWh]. The results obtained indicate that public participation is not only a complementary element of the design process, but it can also be a key component of the decarbonisation strategy in residential construction. Involving future users in the decision-making process increases the likelihood of achieving long-term greenhouse gas emission reductions and supports the implementation of long-term climate policy goals. Full article

The high energy consumption in the building sector and the increasing impacts of climate change have necessitated the transition to net-zero-energy buildings (NZEBs), in which energy retrofit strategies play a key role. However, neglecting moisture transport and climatic design while improving energy efficiency often leads to reduced building performance, material deterioration, worse occupant health, and indoor environmental problems. This review examines in detail the basic mechanisms of moisture transport, including diffusion, capillary action, and airborne moisture transport, and illustrates how poor moisture control affects thermal performance and resident health. Additionally, a comparative analysis of the impact of retrofit strategies implemented in different climatic regions on energy efficiency, carbon emission reduction, moisture-related failures and net-zero goals is conducted. At the same time, the need exists to incorporate awareness regarding the adverse effects on the health of occupants. This systematic review analyzed 120 peer-reviewed studies published from 1994 to 2026, covering different climatic regions (e.g., cold, temperate, warm–humid, etc.). The analysis found that the energy savings rates were reported to range from 18% to 45%, while the moisture-related failures in inappropriately retrofitted buildings were observed to increase by up to 32% in some cold regions. This research review provides a comprehensive advisory framework for domestic residents to take remedial steps until retrofit experts gain access in order to prevent health risks from mold and moisture ingress, which can contribute to a healthy lifestyle and a net-zero-energy building. Full article

Accelerating decarbonization in hot-climate buildings requires integrated retrofit strategies that address energy performance, environmental impact, thermal comfort, and economic feasibility within a unified decision framework. This study develops and validates a simulation-driven multi-criteria approach to evaluate retrofit packages across three representative ASHRAE hot sub-climates (1B, 2B, 2A). An academic building was modeled using DesignBuilder (Stroud, UK) and validated in accordance with ASHRAE Guidelines. The retrofit analysis integrates envelope enhancements (insulation and reflective coatings), glazing-integrated photovoltaics (GIPV), rooftop photovoltaics (RTPV), and a Dedicated Outdoor Air System (DOAS). The performance evaluation incorporates dynamically simulated energy consumption, operational CO₂ emissions, thermal comfort indicators (PMV and DCH), and techno-economic metrics (IRR, ROI, PBP). Weighting factors were derived from a structured stakeholder consultation to reflect context-sensitive sustainability priorities. The results indicate energy reductions of approximately 51–57% and carbon emission reductions of 40–53% across the examined zones, while discomfort hours decreased by roughly 42–46%. This demonstrates significant improvements in thermal comfort under integrated retrofit strategies, particularly with DOAS integration, highlighting the importance of ventilation-driven comfort enhancement. Economic feasibility was climate-dependent; envelope-focused solutions yielded high returns, while integrated strategies delivered balanced environmental and economic performance. The proposed framework enables systematic, climate-specific prioritization of retrofit alternatives and supports scalable, economically viable NZEB transitions in rapidly expanding hot-climate educational infrastructure. Full article

Accurate energy forecasting is critical for the financial and environmental sustainability of the hospitality sector, particularly in energy-intensive subtropical climates. This research addresses a significant gap by conducting a comprehensive, comparative analysis of six machine learning algorithms—Artificial Neural Networks (ANN), Random Forest (RF), XGBoost, Radial Basis Function (RBF), Autoencoder, and Decision Trees—to predict the hourly energy consumption of a hotel in Cuba. We significantly enhance predictive performance through a novel hybrid ensemble scheme, integrating voting, stacking, and blending techniques. Furthermore, this study pioneers a long-term forecasting methodology by utilizing a Long Short-Term Memory (LSTM) model to project the hotel’s energy demand over a 50-year horizon, providing the strategic insight necessary for evaluating major retrofits. Our results demonstrate that ensemble methods, particularly blending, achieve superior accuracy and stability, with correlation coefficients up to 0.975 and the lowest error metrics. The subsequent high-fidelity predictions, including an analysis revealing a minimal specific CO₂ emission of 0.025 kg from natural gas use, provide a quantitative foundation for formulating sustainable energy policies, incentivizing investment in efficient technologies, and ensuring that long-term emission reduction targets are both financially viable and technically robust. Full article

Buildings account for nearly 40% of global energy use and 36% of CO₂ emissions, positioning Net-Zero Energy Buildings (NZEBs) as vital for climate mitigation. However, large-scale adoption remains limited by technical, economic, and policy barriers. This study systematically reviews 1285 peer-reviewed articles (2015–2025) from Scopus and Web of Science, following PRISMA guidelines and thematic analysis to assess renewable energy integration and efficiency strategies. Results indicate that 70% of studies highlight emissions reduction and cost savings as key NZEB benefits, while 60% cite high storage costs and 45% report grid integration challenges. Only 30% of studies address policy dependency, revealing a research gap. Effective measures include passive solar design (up to 25% heating load reduction), high-performance envelopes (15–40% energy savings), and smart energy management (10–20% efficiency gains). Persistent obstacles involve high upfront costs, renewable variability, and rapid technological obsolescence. Achieving NZEB viability requires integrating energy-efficient design, affordable renewables, advanced storage, and coherent policy frameworks to accelerate the transition toward a sustainable, NZEB-built environment. Full article

Decarbonising the existing residential sector is a central priority of European energy policy, yet masonry buildings from the early 2000s remain significantly underrepresented in net-zero energy building (NZEB) research. This study addresses this critical gap by evaluating a holistic deep retrofit of a representative single-family house in Cracow, Poland, providing a scalable model for the Central European housing stock. The methodology integrated structural and systemic interventions: eliminating thermal bridges via balcony removal, enhancing the envelope with 0.25 m of mineral wool (λ = 0.036 W/m K), and installing innovative active triple-glazed windows (U_w = 0.85 W/m² K) with integrated electric heating foils. The energy system was transformed by replacing a coal-fired boiler with an 8 kW air-to-water heat pump and a 7 kWp photovoltaic array, complemented by a green roof on the western pitch for passive thermal buffering. Verified results demonstrate a radical reduction in the non-renewable primary energy (EP) index from 224.56 kWh/(m²·a) to 0.00 kWh/(m²·a), achieving full compliance with stringent “WT 2021” standards. Economic analysis reveals that the integrated approach is financially viable, with a simple payback time (SPBT) of 7.1 years when supported by available subsidies. This study concludes that the integration of active glazing, high-performance insulation, and nature-based solutions offers a replicable and economically sound roadmap for transforming legacy housing into zero-emission assets. Full article

In response to growing energy demands and climate pressure in hot regions, this study presents an integrated techno-economic and environmental assessment of building envelope retrofit strategies aimed at facilitating the transition of existing buildings toward Nearly Zero-Energy Building (NZEB) targets. Three advanced retrofit solutions—radiative coatings (RC), glazing-integrated photovoltaic (GIPV) systems, and solar green roofs—are evaluated using a validated building performance simulation framework across four representative climatic zones in Egypt. The results demonstrate that radiative coatings provide the most favorable economic performance, achieving return on investment (ROI) values between 12.37% and 21.72% and payback periods ranging from 3.5 to 6.2 years. Solar green roofs and GIPV systems deliver substantial reductions in annual electricity consumption and operational CO₂ emissions, with their performance strongly influenced by climatic conditions and cooling demand intensity. Solar green roofs achieve ROI values of 5.15–6.54% with payback periods of 11.7–14.9 years, while GIPV systems yield ROI values of 4.0–5.24% and payback periods between 14.6 and 17.1 years. Overall, the findings indicate that climate-adapted envelope retrofit strategies can significantly enhance building energy performance while providing measurable economic and environmental benefits. This study offers a robust, data-driven basis for retrofit prioritization and policy formulation in hot regions. Full article

Hospitals are the most energy-intensive buildings in the tertiary sector because they have continuous and high demand for heating and cooling (to meet strict thermal comfort conditions), hot water, kitchen facilities, electricity, etc. Investigation of the energy performance of hospital buildings is crucial for defining energy savings and developing benchmarks and design guidelines for nearly Zero-Energy Hospitals (nZenHs). This study investigates the energy efficiency of hospital buildings in Greece and the necessary retrofit strategies to transform them to nearly Zero-Energy Buildings (nZEBs). Six building typologies were recognized, based on the building’s floor plan, and energy upgrade scenarios were investigated for each typology. The first scenarios aimed at improving the building’s energy efficiency, and the last one exploited the use of renewable energy source (RES) systems to minimize energy consumption. More specifically, a rooftop photovoltaic system was examined. The results showed differences in hospitals’ energy performance according to typology and climatic zone. They strongly confirm that hospitals can be transformed into buildings with nearly zero-energy consumption, irrespective of their design. The significant energy savings achieved by transforming hospitals into NZEBs highlight the crucial role in enhancing energy efficiency in tertiary sector buildings. Full article

Achieving Net-Zero Energy Building (NZEB) performance through retrofitting requires identifying optimal measures that effectively enhance energy efficiency. Determining these optimal retrofit strategies typically involves running thousands of building energy simulations, which imposes a substantial computational burden. To address this challenge, a novel machine learning-based framework is proposed to optimize retrofit strategies for NZEBs under future climate change scenarios. A Non-Dominated Sorting Genetic Algorithm (NSGA-III) is employed to minimize both annual energy consumption and the Predicted Percentage of Dissatisfied (PPD), while simultaneously ensuring net-zero energy balance, thereby generating a Pareto front of optimal solutions. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is then applied to rank the Pareto-front solutions and identify the most favorable retrofit scenario. The results show that the proposed framework reduces optimization time by at least a factor of two compared with simulation-only optimization. Leveraging these computational savings, the framework evaluates a suite of passive and renewable measures across multiple future timeframes to capture the influence of climate change on retrofit performance. The findings indicate that achieving NZEB under future climate conditions requires higher levels of thermal insulation and greater renewable integration than under present-day conditions. Under the Shared Socioeconomic Pathways (SSP) framework, optimal insulation levels in the fossil fuel-dependent scenario are lower than in the sustainable scenario by up to 18% in C-type (warm temperate), 12% in D-type (snow), and 13% in E-type (polar) climates. The combined retrofit measures can reduce annual energy consumption by up to 80% and lower PPD by as much as 67% compared to the base case. Full article

Residential buildings in Mediterranean regions remain major contributors to energy consumption and greenhouse gas emissions. Existing studies often assess renewable energy technologies or innovative building solutions in isolation, with limited attention to their combined performance across different residential typologies. This study evaluates the integrated impact of solar renewable energy systems and smart building technologies on the energy performance of residential buildings in Cyprus. A typology-based methodology is applied to three representative residential building types—detached, semi-detached, and apartment buildings—using dynamic energy simulation and scenario analysis. Results show that solar photovoltaic systems achieve higher standalone reductions than solar thermal systems, while smart building technologies significantly enhance operational efficiency and photovoltaic self-consumption. Integrated solar–smart scenarios achieve up to 58% reductions in primary energy demand and 55% reductions in CO₂ emissions, and 25–30 percentage-point increases in PV self-consumption, enabling detached and semi-detached houses to approach national nearly zero-energy building (nZEB) performance thresholds. The study provides climate-specific, quantitative evidence supporting integrated solar–smart strategies for Mediterranean residential buildings and offers actionable insights for policy-making, design, and sustainable residential development. Full article

The building sector is significantly responsible for the world’s energy consumption and carbon emissions. Net-zero energy buildings (NZEBs) have become an effective solution to move towards sustainability, maximizing energy efficiency, and minimizing carbon footprint. However, achieving net-zero energy targets requires a comprehensive understanding of building performance from the perspectives of technologies, materials, and strategies, for which existing studies have a knowledge gap. This study aims to bridge the knowledge gap within existing studies through an empirical investigation. Based on a review of the literature, this study employs semi-structured interviews in the United Kingdom (UK) with industrial professionals experienced in NZEBs. The qualitative data collected from interview participants are analyzed minutely using NVivo to identify key themes and patterns, including 14 technologies, 12 materials, and seven strategies for NZEBs. Based on the literature review and, more importantly, the interview analysis, a conceptual framework is well established to describe an NZEB as a complex system that must incorporate appropriate technology adoption, careful material selection, and successful strategy implementation into consideration. This study provides a comprehensive understanding of NZEBs from a systematic point of view. It also contributes to the full fulfillment of Sustainable Development Goals (SDGs) established by the United Nations (UN). Full article

The three key design criteria for nearly zero-energy buildings (nZEBs) and climate-neutral buildings are minimizing energy use, ensuring high occupant comfort, and reducing environmental impact. Thermal comfort is one of the main components of indoor environmental quality (IEQ), strongly affecting occupants’ health, well-being, and productivity. As energy-efficiency requirements become more demanding, the appropriate selection of heating systems, their automated control, and the management of solar heat gains are becoming increasingly important. This study investigates the influence of two low-temperature radiant heating systems—underfloor and wall-mounted—and the use of Venetian blinds on perceived thermal comfort in a highly glazed public nZEB building located in a densely built urban area within a temperate climate zone. The assessment was based on the PMV (Predicted Mean Vote) index, commonly used in IEQ research. The results show that both heating systems maintained indoor conditions corresponding to comfort or slight thermal stress under steady state operation. However, during periods of strong solar exposure in the room without blinds, PMV values exceeded 2.0, indicating substantial heat stress. In contrast, external Venetian blinds significantly stabilized the indoor microclimate—reducing PMV peaks by an average of 50.2% and lowering the number of discomfort hours by 94.9%—demonstrating the crucial role of solar protection in highly glazed spaces. No significant whole-body PMV differences were found between underfloor and wall heating. Overall, the findings provide practical insights into the control of thermal conditions in radiant-heated spaces and highlight the importance of solar shading in mitigating heat stress. These results may support the optimization of HVAC design, control, and operation in both residential and non-residential nZEB buildings, contributing to improved occupant comfort and enhanced energy efficiency. Full article