Reduce Building Energy Consumption Research Articles

Carbon reduction potential of housing retrofits: Evidence from China

Carbon emissions have become a major contributor to global climate change, with the building sector representing one-third of the global energy demand, and the residential sector accounting for 70 % of final energy demand worldwide. The energy consumption for building cooling has grown rapidly in recent years. Housing retrofits have shown potential in improving building energy efficiency and thus aligning with objectives for energy-saving and carbon emissions reduction in the residential sector. Based on survey data from 28 provinces in China, this study estimates the impacts of housing retrofits on the building energy consumption for air conditioners, as well as impacts on the resulting carbon emissions. Employing Endogenous switching regression to mitigate self-selection bias and the consequent endogeneity problem, the analysis reveals that housing retrofits can reduce building energy consumption and consequent carbon emissions. Furthermore, factors including household characteristics, building attributes and geographic location can influence both residential energy consumption and carbon emissions. In addition, low-income households, families with children and those living in self-owned houses can benefit the most from housing retrofits. This study also offers recommendations to reducing household energy consumption and carbon emissions through improved renovation practices. These insights are instrumental for policymakers in identifying targeted policy objectives across diverse demographic groups. The findings hold relevance for other developing countries with large amounts of inefficient housing stock during rapid urbanization, and those prone to global warming, aiding their pursuit of Sustainable Development Goals.

Enhancing Building Energy Efficiency: Leaf Transpiration Inspired Construction of Lignin-Based Wood Plastic Composites for Building Energy Conservation

Incorporating phase change materials (PCMs) into buildings represents a strategic method for reducing reliance on air conditioning systems and decreasing energy usage consequently. Inspired by leaf veins providing channels for transpiration, lignin porous carbon (LPC) was synthesized by chemical activation, showing a vein pore structure. The capillary network system of the LPC provided more channel to adsorb PCM through surface tension and capillary force, achieving an impressive loading capacity of LPC for polyethylene glycol (PEG) (75%), which demonstrated exceptional heat storage capability (133.21 J/g). The lignin-derived wood-plastic composite (L-WPC) was further prepared. With the gradual increase of LPC/PEG, the latent heat of L-WPC increased gradually. The ΔHm, ΔHc and energy storage efficiency of L-WPC-50 (incorporated 50 wt% LPC/PEG-75) reached 39.99 J/g, 42.65 J/g and 90.26%, respectively. The vein pore structure of LPC also provided a thermal conductivity link for L-WPC. L-WPC-50 demonstrated an increased thermal conductivity (0.66 W/(m·K)) and a reduced thermal diffusion coefficient (0.24 mm2/s), optimizing the effectiveness of the phase transition. Additionally, L-WPC-50 displayed satisfactory mechanical properties and dimensional stability, with tensile strength, bending modulus and water absorption thickness swelling rate measuring 14.40 MPa, 1043.72 MPa, and 1.61% respectively. It introduced a feasible approach for utilizing biomass in enhancing building energy efficiency, marking a significant stride towards reducing building energy consumption and advocating sustainable energy practices.

Building a sustainable future: Exploring the nexus between climate awareness and thermal insulation choices in new home construction

Climate change is considered a major threat to the environment and society as a whole. Reducing building energy consumption through the use of thermal insulation is one way of combating climate change. This study examines the impact of climate change awareness on the pre-construction decision of Lebanese homeowners to use thermal insulation in their new homes. A model building consisting of a typical 160 m2 single-family home was used and its thermal loads were calculated in two cases: insulated and uninsulated case, in three different locations in Lebanon: Beirut, Chtaura, and Bcharre-Arz. The thermal loads were calculated using two methods: the degree-days empirical method, and the Hourly Analysis Program software numerical method. The computations showed energy reduction ranging between 23% in the coastal region to 52% in high mountains when thermal insulation of thickness 5 cm was used. The investment payback period ranged from 4.3 years in the coastal region to 1.5 years in the high mountains. A survey addressed to 100 respondents was used to understand how Lebanese homeowners’ decision to use thermal insulation was affected by knowledge of the obtained results. The survey results showed that climate change awareness has a high impact on this decision; however, the cost seems to play an important role in the owners’ final decision on whether or not to use thermal insulation. Spreading awareness about climate change and the payback periods of building thermal insulation will increase its use since the number of respondents refusing to use thermal insulation drastically decreased after being informed about its payback period.

Characteristics and Application Analysis of a Novel Full Fresh Air System Using Only Geothermal Energy for Space Cooling and Dehumidification

To effectively reduce building energy consumption, a novel full fresh air system with a heat source tower (HST) and a borehole heat exchanger (BHE) was proposed for space cooling and dehumidification in this paper. The cooling system only adopts geothermal energy to produce dry and cold fresh air for space cooling and dehumidification through the BHE and HST, which has the advantage of non-condensate water compared to BHE systems integrated with a fan coil or chilled beam. Based on the established mathematical model of the cooling system, this paper analyzed the system characteristics, feasibility, operation strategy, energy performance, and cost-effectiveness of the proposed model in detail. The results show that the mathematical model has less than 10% error in estimating the system performance compared to the practical HST–BHE experimental set up. Under the specific boundary conditions, the cooling and dehumidification capacity of this system increases with the decrease in the air temperature, air moisture content, and inlet water temperature of the HST. The optimal cooling capacity and the system COP can be achieved when the air–water flow ratio is at 4:3. A case study was conducted in a residential building in Shenyang with an area of about 1800 m2. It was found that this system can fully meet the cooling and dehumidification demand in such a residential building. The operation strategy of the cooling system can be optimized by adjusting the air–water flow ratio from 4:3 to 3:2 during the early cooling season (7 June–1 July) and end cooling season (3 August–1 September). As a result, the average COP of the cooling system during the whole cooling season can be improved from 6.1 to 8.7. Compared with the air source heat pump (ASHP) and the ground source heat pump (GSHP) for space cooling, the proposed cooling system can achieve an energy saving rate of 123% and 26%, respectively. Considering that the BHE of the GSHP can be part of the proposed HST–BHE cooling system, the integration of the HST and GHSP for space cooling (and heating) is strongly recommended in actual applications.

Application of Renewable Energy in Green Buildings and Energy Consumption Optimization

INTRODUCTION: With the increasing global awareness of sustainable development and environmental protection, green building has become one of the important development directions in the construction industry. The application of sustainable type energy in the construction industry is of great significance in reducing building energy consumption and environmental pollution. This study aims to explore the application of sustainable types of energy and conduct research on energy consumption optimization. OBJECTIVE: The aim of this study is to analyze the current situation of the application of sustainable types of energy in the construction industry, to explore its impact on the energy consumption of buildings, and to propose corresponding optimization strategies in order to achieve the goal of sustainable development of green buildings in China. METHODS: This study adopts a combination of literature review and case study; firstly, a literature review on the application of sustainable types of energy, sorting out its technical characteristics and application effects; then, several typical cases are selected to analyze its energy application and energy consumption in buildings; finally, relevant strategies and suggestions for optimizing the energy consumption are put forward by combining the results of the literature review and the case study. RESULTS: Through the literature review and case analysis, it is found that sustainable types of energy, such as solar energy and wind energy, have been widely used in buildings and achieved certain energy-saving effects. However, there are also some problems, such as inefficient energy utilization and high cost. To address these problems, this study proposes a series of optimization strategies, including suggestions for optimizing energy system design, improving energy utilization efficiency, and reducing energy costs. CONCLUSION: This study concludes that the application of sustainable types of energy in green buildings is an important way to optimize building energy consumption and sustainable development. Through measures such as optimizing energy system design and improving energy utilization efficiency, building energy consumption can be further reduced, environmental pollution can be reduced, and the development of the construction industry can be promoted. However, further research and practice are still needed to continuously improve relevant technologies and policies to promote the application and development of sustainable types of energy in buildings.

Optimizing the dimensional ratio and orientation of residential buildings in the humid temperate climate to reduce energy consumption (Case: Rasht Iran)

Today, the increase in the number of cities and greenhouse gas increases has led to the intensification of global warming. The construction industry has had a significant impact on this crisis. Therefore, using passive solutions such as optimizing building proportions and proper orientation in any climate can significantly help reduce building energy consumption and greenhouse gases. The research aims to optimize the proportions of residential buildings and their orientation to minimize the building's energy consumption in the city of Rasht with a moderate climate. For this purpose, a three-story building with dimensions of 1:1 was selected, and the energy consumption of the building, including the load of cooling, heating, and lighting, was calculated in the north-south and east-west dimensions up to the ratio of 1–10. This research has used validated software to calculate energy consumption. Then, the most optimal mode was selected in terms of proportionality; the energy consumption of the building with a different orientation compared to the geographical north was calculated for each degree up to 360°. The results showed that the energy consumption of the building with a ratio of 1:4 with east-west elongation was 155.29 kWh/m2, which has the lowest energy consumption compared to other modes and is also compatible with the construction and building industry. Also, the building with zero-degree orientation to the geographic north and east-west elongation has the lowest carbon dioxide production and annual energy consumption, which are 2107 kg/m2 and 146.28 kWh/m2, respectively. By using two primary parameters, i.e., building orientation and aspect ratio, this research presents a valid innovation in optimizing the energy consumption of buildings. This research is focused on the detailed analysis of the environmental performance of a building in Rasht climate and determining the best form and orientation to reduce energy consumption and environmental efficiency.

Planning and design of an architectural energy supply system based on photovoltaic-thermal technology

China’s building energy consumption is growing and the energy consumption of the whole process of buildings accounts for more than 46.5% of the country’s total energy consumption, of which the proportion of energy consumption used for heating, ventilation and air conditioning is as high as 50%. Solar energy has the greatest potential to achieve energy conservation in buildings. Buildings are the best carrier for solar energy utilization because of the advantages of local collection and local application. The combination of solar energy and buildings can meet a variety of energy and health needs in buildings, among which solar photovoltaic and CSP building integration technology is an important way to reduce building energy consumption and improve indoor air quality. This article presents a PV/T-based thermal storage wall system that efficiently utilizes solar energy. It outlines the PV/T technology’s fundamental principles and provides a detailed description of the system’s construction and operation, highlighting critical components like the solid thermal storage medium and heat transfer via a heat pump. The analysis indicates improved energy utilization and favorable economic feasibility. This technology offers a practical solution for the construction industry, promoting sustainable energy practices and environmental conservation.

Thermal performance of a wooden pipe-embedded building envelope using a low-grade heat source in extreme cold climate conditions

A pipe-embedded wall can effectively reduce building energy consumption in winter. Most of the research on this concept to date has used traditional building materials such as concrete and brick. This paper reports on a wooden pipe-embedded wall allowing more flexible pipe locations, which can be used to reduce heat load in winter. An experimental assessment was developed to investigate the building assemblies thermal performance and the results were used to develop an understanding of its thermal energy saving potential, and as an input for the validation of a numerical model of same. A 3D computational fluid dynamics model of the pipe-embedded wall was developed and applied to assess the thermal performance of the wall under boundary conditions beyond the capabilities of the experimental assessment. Further, the influence of five parameters including the outdoor temperature and pipe positions were studied. A method was proposed for selecting the pipe layer's optimal location. The results show dual thermal impacts of the pipe layer: active heating and passive insulation. Using 8°C water reduces internal surface heat transfer by 42.5% under -20°C outdoor temperature conditions. This is akin to an 18°C outdoor temperature rise. Furthermore, another interesting result is that increasing the wall material thermal resistance can sometimes increase energy consumption. This study provides a reference for designing and optimizing net zero energy buildings in extreme cold climate conditions.

OcAPO: Fine-grained occupancy-aware, empirically-driven PDC control in open-plan, shared workspaces

Passive Displacement Cooling (PDC) is a relatively recent technology gaining attention as a means of significantly reducing building energy consumption overheads, especially in tropical climates. PDC eliminates the use of mechanical fans, instead using chilled-water heat exchangers to perform convective cooling. In this paper, we identify and characterize the impact of several key parameters affecting occupant comfort in a 1000m2 open-floor area (consisting of multiple zones) of a ZEB (Zero Energy Building) deployed with PDC units and tackle the problem of setting the temperature setpoint of the PDC units to assure occupant thermal comfort and yet conserve energy. We tackle two key practical challenges: (a) the zone-level (i.e., occupant-experienced) temperature differs significantly, depending on occupancy levels, from that measured by the ceiling-mounted thermal sensors that drive the PDC control loop, (b) sparsely deployed sensors are unable to capture the often-significant differences in ambient temperature across neighboring zones. Using extensive real-world coarser-grained measurement data (collected over 60 days under varying occupancy conditions), (a) we first uncover the various parameters that affect the occupant-level ambient temperature, and then (b) devise a trace-based model that helps identify the optimum combination of PDC setpoints, collectively across multiple zones, while accommodating variations in the occupancy levels and weather conditions. Using this trace-based model, our OcAPO system can assure ambient temperature experienced by occupants within a tolerance of 0.3°C. In contrast, the existing approach of occupancy-agnostic, rule-based setpoint control violates this tolerance interval more than 80% of the time. However, this initial model requires unnecessary and continual database lookups and is unable to derive finer-grained setpoints, thereby potentially missing opportunities for additional energy savings. We thus collected data for another 15 days, with finer-grained setpoint control in increments of 0.2∘ under varying occupancy conditions in the second phase. To determine PDC setpoints efficiently, we subsequently used the empirical data to train a KNN-based regression model. Additional studies on our real-world testbed demonstrate the regressor-based OcAPO approach is able to assure occupant-level ambient temperature within a narrow 0.2°C tolerance. We also demonstrate that the regression version of OcAPO can reduce the opening percentage of PDC valves (an indirect proxy for energy consumption) by 58.9% under low occupancy compared to the trace-based model.

Controlling the Size of Hydrotalcite Particles and Its Impact on the Thermal Insulation Capabilities of Coatings.

This study focuses on the development of high-performance insulation materials to address the critical issue of reducing building energy consumption. Magnesium-aluminum layered double hydroxides (LDHs), known for their distinctive layered structure featuring positively charged brucite-like layers and an interlayer space, have been identified as promising candidates for insulation applications. Building upon previous research, which demonstrated the enhanced thermal insulation properties of methyl trimethoxysilane (MTS) functionalized LDHs synthesized through a one-step in situ hydrothermal method, this work delves into the systematic exploration of particle size regulation and its consequential effects on the thermal insulation performance of coatings. Our findings indicate a direct correlation between the dosage of MTS and the particle size of LDHs, with an optimal dosage of 4 wt% MTS yielding LDHs that exhibit a tightly interconnected hydrotalcite lamellar structure. This specific modification resulted in the most significant improvement in thermal insulation, achieving a temperature difference of approximately 25.5 °C. Furthermore, to gain a deeper understanding of the thermal insulation mechanism of MTS-modified LDHs, we conducted a thorough characterization of their UV-visible diffuse reflectance and thermal conductivity. This research contributes to the advancement of LDH-based materials for use in thermal insulation applications, offering a sustainable solution to energy conservation in the built environment.

Development of ReShadS, a climate-responsive shading system: Conception, design, fabrication, and small-scale testing

Integrating computational technologies to produce dynamic and intelligent architecture that can enhance building thermal performance and meet users' requirements and routines is broadly classified as responsive architecture. This seems to be a viable solution for façades, reducing energy demand during the building operational phase. However, scientific content regarding responsive components' fabrication, operation, and performance evaluation is not yet consolidated. This paper comprehensively presents the design and fabrication processes of a low-cost responsive shading system prototype, accounting for materials' characterization, software, responsive functionality, and its performance evaluation regarding thermal and illuminance management. The analysis is based on the Adaptive Comfort Model and Useful Daylight Illuminance parameters. Preliminary results indicate the system's feasibility in managing temperature and illuminance within the comfort zone by 58 % and 82 % of data points, respectively. The resulting prototype and the responsive management strategy contribute to the emerging responsive architecture field toward reducing building energy consumption.

Economic optimization of exterior wall insulation in Chinese office buildings by coupling artificial neural network and genetic algorithm

Envelope insulation is an essential measure to reduce building energy consumption and is the focus of many building energy codes. In China, the current standard (GB 55015-2021) only specified limit values for the thermal conductivity (U) of the exterior walls, and it ignored variations in building characteristics and internal parameters. Therefore, it is difficult for architects to quickly determine the exterior wall U-value in building design and retrofit. To address this issue, the exterior wall U-values of office buildings in China were economically optimized by TRNSYS, ANN, and GA. To begin with, the effect of enhancing exterior wall insulation on the heating and cooling energy consumption of office buildings was investigated by TRNSYS software, taking into account variations in building characteristics. Moreover, the exterior wall U-values of office buildings were optimized by coupling ANN and GA. The results showed that the design values of the GB 55015-2021 did not achieve the optimal results in China, and the most economical exterior wall U-value was 0.24 W/(m2·K) in Harbin, 0.24 W/(m2·K) in Beijing, 0.42 W/(m2·K) in Changsha, 1.82 W/(m2·K) in Guangzhou, 0.66 W/(m2·K) in Kunming. Compared with the pre-optimization, the annual life cycle cost of building heating and cooling reduced by 0.96 % in Harbin, 2.07 % in Beijing, 1.44 % in Changsha, 1.68 % in Guangzhou, and 7.37 % in Kunming. In addition, variations in building parameters should be considered in the design phase of new buildings or in the renovation of old buildings, such as internal heat gain, which may lead to different optimal results.

Thermochromic Hydrogels with Adjustable Transition Behavior for Smart Windows.

With the fast economic development and accelerating urbanization, more and more skyscrapers made entirely of concrete and glass are being constructed. To keep a comfortable indoor environment, massive energy for air conditioning or heating appliances is consumed. A huge amount of heat (>30%) is gained or released through glass windows. Using smart windows with the capability to modulate light is an effective way to reduce building energy consumption. Thermochromic hydrogel is one of the potential smart window materials due to its excellent thermal response, high radiation-blocking efficiency, cost-effectiveness, biocompatibility, and good uniformity. In this work, polyhydroxypropyl acrylate (PHPA) hydrogels with controllable lower critical solution temperature (LCST) were prepared by photopolymerization. The transition temperature and transition rate under "static transition" conditions were investigated. Unlike "static" conditions in which the transition temperature was not affected by the initial and final temperature and heating/cooling ramp, the transition temperature varied with the rate of temperature change under dynamic conditions. The "dynamic" transition temperature of the PHPA hydrogel gradually increased with the increase of the heating rate. It was the result of the movement of the molecular chains lagging behind the temperature change when the temperature change was too fast. The results of the solar irradiation experiment by filling PHPA hydrogels into double glazing windows showed that the indoor temperature was about 15 °C lower than that of ordinary glass windows, indicating that it can significantly reduce the energy consumption of air conditioning. In addition, a wide range of adjustable transition temperatures and fast optical response make PHPA hydrogels potentially applicable to smart windows.

Building energy savings by green roofs and cool roofs in current and future climates

The global energy demand has greatly impacted greenhouse gas emissions and climate change. Since buildings are responsible for a large portion of global energy consumption, this study investigates the energy-saving potential of green roofs and cool roofs in reducing building energy consumption. Using an integrated approach that combines climate change modeling and building energy simulation, the study evaluates these strategies in six global cities (Cairo, Hong Kong, Seoul, London, Los Angeles, and Sao Paulo) under current and future climate change scenarios. The results show that in future climates, the implementation of green and cool roofs at the city level can lead to substantial annual energy reductions, with up to 65.51% and 71.72% reduction in HVAC consumption, respectively, by 2100. These findings can guide the implementation of these strategies in different climatic zones worldwide, informing the selection and design of suitable roof mitigation strategies for specific urban contexts.

Sensitivity Analysis and Optimization of Energy-Saving Measures for Office Building in Hot Summer and Cold Winter Regions

To effectively reduce building energy consumption and enhance indoor thermal comfort, this study developed a sensitivity analysis and multi-objective optimization method for an office building in Hangzhou considering the effects of parameter interactions. We utilized Latin hypercube sampling (LHS) to sample the parameters and subsequently simulated the energy consumption and discomfort hours for the building’s four orientations. Following this, Gaussian process regression models were established, and the feature importance ranking method (FIRM) alongside an interaction effects method were employed to quantify the sensitivity of 10 parameters. Lastly, a multi-objective optimization was performed for total energy consumption and discomfort hours, yielding a set of Pareto-optimal solutions. Through the VIKOR method, the optimal solution within the Pareto set was identified, resulting in three sets of optimal solutions.

Layer-stacked polyaniline/silver nanowire composite film for multicolor electrochromic smart windows with dual-band optical modulation

Dual-band electrochromic smart windows (DESWs) have attracted widely concern for their potential in significantly reducing building energy consumption by selectively controlling near-infrared (NIR) and visible light (VIS) transmittance. However, its monotonous color changes limit its large-scale application. In this study, we designed a DESW based on the layer-stacked polyaniline (PANI)/silver Nanowires (Ag NWs) composite films. When PANI films is stacked layer by layer with Ag NWs, it not only performs dual band regulation, but also exhibits impressive electrochromic performance with rich color conversions (light yellow, yellow-green and blue-black). The four-layer PANI/Ag NWs composite film outperformed the pure single-layer PANI film because of the faster electron transfer, its coloring time and bleaching time at 525 nm were shortened to 6.7 s and 18.0 s, respectively, and the coloring efficiency was increased to 45.5 cm2 C-1. After 2500 cycles, the PANI/Ag NWs films tend to have better cycle stability. Therefore, the incorporation of Ag NWs enhances the electrochromic performance of PANI films, providing valuable insights for advancing single-component organic electrochromic materials.

Preparation and performance study of a novel radiant panel for thermal and cooling storage with phase change materials

Phase change radiant panels (PCRPs) with thermal storage can enhance the heat capacity of buildings, and reduce building energy consumption. In this paper, a composite phase change material (CPCM) was prepared by paraffin wax-lauric acid/expanded graphite (PW-LA/EG) and applied to radiant panels. This CPCM exhibits a broad temperature range for phase change (10°C - 40°C), with EG at the optimal mass fraction of 14% and PW-LA at the optimal ratio of 1:1. It has a moderate latent heat capacity, a thermal conductivity of 1.692 W/mK, and excellent thermal stability. Furthermore, the simulations were performed in this paper, and the year-round comfort, thermal storage/release characteristics, and the influencing factors of PCRPs were evaluated by TRNSYS software. The results show that the PCRP can enhance indoor comfort throughout the year and exhibit excellent thermal storage and release properties. The analysis of influencing factors indicates that the thickness of the PCM has a small impact on the PCRP. It is recommended that a radiant panel coverage rate of at least 70% and a water supply time of 10 h in summer and 8 h in winter. These optimized parameter values can offer valuable guidance for the design and practical application of PCRPs. Practical application Phase change materials have been widely studied as materials used for thermal energy storage. The radiant panel with phase change materials can enhance the heat capacity of buildings, and reduce building energy consumption. This paper proposes a phase change radiant panel that can be used to solve the problem of year-round energy storage of radiant panels in hot summer and cold winter areas. Furthermore, this paper uses TRNSYS software to study the performance of the phase change radiant panels and offers valuable guidance for the design and practical application of PCM radiant panels.

Effect of Orientation and Skylight Area Ratio on Building Energy Efficiency in the Qinghai–Tibet Plateau

The Qinghai–Tibet plateau, with an average altitude of over 4000 m, has low annual average temperatures and a high demand for building heating. This region’s abundant solar energy resources hold substantial practical significance for improving the indoor heat environment and reducing building energy consumption. This paper investigates the impact of orientation and skylight area ratio on building heat load and indoor temperature, using both actual measurement and simulation methods, with a case study of the comprehensive building at Beiluhe Observation and Research Station of Frozen Soil Engineering and Environment (Beiluhe Station), located in the Qinghai–Tibet Plateau region. Initially, a model was established using the EnergyPlus 9.4 software, with orientation variables set from east to west in 15° increments, to simulate the variations in building heat load resulting from orientation changes; simulations were then conducted for three different skylight area ratios under the optimal orientation to evaluate their influence on heat load and indoor temperature. The results show that for the architectural style examined in this paper, the optimal building orientation within the region is 30° south by east, with the optimal orientation range spanning from 45° south by east to due south. Heating load is negatively correlated with the skylight area ratio, and beyond a certain threshold, the rate of decrease in heat load diminishes or even stabilizes. The conclusions of this paper offer guidance for the orientation and skylight design of new buildings on the Qinghai–Tibet Plateau.

Long-term assessment of energy consumption reduction in a building ventilation system with passive particulate matter control technology in the fresh air intake

A particulate matter (PM) control device known as aspiration efficiency reducer (AER) has been developed as an attachment to the fresh air intake in building ventilation systems to reduce building energy consumption and improve the fresh air intake’s quality. Ambient particle laden air is drawn into the fresh air inlet of a mechanically ventilated building via the air handling unit (AHU). The ventilation system particle filters become loaded and clogged with PM, increasing the load on the fan’s motor. Three novel AER devices were tested against an AHU inlet rainhood, and their long-term energy performance assessed. Furthermore, an AER attached to an AHU incorporating single-stage filtration (SSF) was compared against an AHU fitted with rainhoods employing two-stage filtration (TSF). The findings showed AER technology resulted in a 6.6–11.4 % reduction in the AHU’s energy consumption. Finally, the impact of the AER with SSF compared to a rainhood with TSF led to a lowering of the system pressure throughout the entire testing period, reduced filter and labour costs resulting in a 36.5 % reduction in the total costs. AER technology and a ventilation filtration system design tailored to the local environment will result in lower building energy consumption and CO2 emissions.

Fluorine-doped ATO NCs with enhanced LSPR effect for smart windows with adaptive solar modulation

Smart windows with excellent near-infrared (NIR) light shielding capacity and controlled visible light transmittance are expected to reduce building energy consumption and improve indoor comfort. However, the ability of current thermochromic materials to regulate solar gain with the tunable extinction of phase-change materials is still far from optimum. In this work, an fluorine (F)-doped ATO (FATO) nanocrystals (NCs) are designed as a photothermal material to optimize the solar modulation of thermochromic hydrogels. F ion doping can modify the electronic structure of ATO, resulting in a high concentration of oxygen vacancies and free electrons, thereby enhancing the NIR absorption performance and photothermal conversion performance of the ATO NCs. On this premise, the designed smart window based on FATO NCs and thermochromic hydrogels exhibits the remarkable features of excellent NIR shielding, high initial visible transmittance and fast response speed. The window is capable of shielding 99.5% of the solar radiation from 300 to 2500 nm and permitting 75.0% of initial visible light. Moreover, the simulated indoor temperature of the smart window was 17.2 °C lower compared with the black one, demonstrating potentials in practical application of building energy saving.