Energy Savings In Buildings Research Articles

An approach to energy conservation in lighting systems using luminaire-based sensor for automatic dimming

Lighting systems account for a significant proportion of energy consumption in buildings. Therefore, energy conservation within these systems can greatly enhance overall building energy efficiency. This study proposes a control strategy for LED lamps by adjusting lighting intensity and improving the performance of electric luminaires. The approach involves implementing an automated dimming system that adapts lighting intensity based on surrounding light levels. A system comprising an ambient light sensor, microcontroller, power supply module, dimming controller, and lamp was developed. The sensors measure brightness within a specified range in real time, and the microcontroller analyzes and compares this data against the brightness settings for specific areas. The designed control system was tested in a laboratory setup to demonstrate its effectiveness in a controlled environment. Results showed a 75.65% reduction in power consumption compared to standard lamps in a simulated environment, highlighting its potential for significant energy savings in buildings and its contribution to environmental sustainability.

Room-temperature phosphorescent transparent wood

Transparent wood with high transmittance and versatility has attracted great attention as an energy-saving building material. Many studies have focused on luminescent transparent wood, while the research on organic afterglow transparent wood is an interesting combination. Here, we use luminescent difluoroboron β-diketonate (BF2bdk) compounds, methyl methacrylate (MMA), delignified wood, and initiators to prepare room-temperature phosphorescent transparent wood by thermal initiation polymerization. The resultant PMMA has been found to interact with BF2bdk via dipole-dipole interactions and consequently enhance the intersystem crossing of BF2bdk excited states. The transparent wood matrix can provide a rigid environment for BF2bdk triplets and serve as oxygen barrier to suppress non-radiative decay and oxygen quenching. The prepared afterglow material has the characteristics of diverse composition, long afterglow emission lifetimes, and high photoluminescence quantum yield. This afterglow transparent wood also demonstrates potential application value in areas such as high mechanical strength, good hydrophobicity, and high cost-effectiveness.

Radiative Warming Glass for High-Latitude Cold Regions.

Traditional window glazing, with inherently adverse energy-efficient optical properties, leads to colossal energy losses. Energy-saving glass requires a customized optical design for different climate zones. Compared with the widely researched radiative cooling technology which is preferable to be used in low-altitude hot regions; conversely in high-latitude cold regions, high solar transmittance (Tsol) and low mid-infrared thermal emissivity (εMIR) are the key characteristics of high-performance radiative warming window glass, while the current low-emissivity (low-e) glass is far from ideal. To address this issue, Drude's theory is used to numerically design a near-ideal film with specified electron density (ne) and electron mobility (µe). The fabricated hydrogen-doped indium oxide (IHO) could achieve high Tsol (0.836) and low εMIR (0.117). Energy-saving simulations further reveal a substantial decrease in annual heating energy consumption up to 6.6% across high-latitude regions (climate zones 6 to 8), translating to a corresponding reduction in CO2 emissions (20.0kg m-2), outperforming 1165 high performance commercial low-e glass. This radiative warming glass holds the promise of making a significant contribution to sustainable building energy savings specifically for high-latitude cold regions, advancing the goal of carbon neutrality.

Utilizing biomass-derived activated carbon hybrids for enhanced thermal conductivity and latent heat storage in form-stabilized composite PCMs

ABSTRACT In this study, the focus was on developing multifunctional organic form-stabilized composite phase change materials (PCMs) to efficiently manage thermal energy and promote sustainable energy utilization. The novel composite PCMs were designed and synthesized by incorporating Methyl stearate (MtS) as the PCM with pristine activated carbon derived from coconut shells (CAC) and thermally enhanced CAC@Graphene nanoplatelets (GnP) hybrid matrices. Particularly, the combination of CAC90@GnP10/MtS allowed the composite PCM to exhibit excellent thermophysical responses, capitalizing on the unique properties and synergistic effects of each component. The resulting composite PCM from this combination demonstrated remarkable performance, with a high loading ratio of 70% and a latent heat of 160.87 J/g, which is 27.52% higher than that of the pristine CAC-supported PCM. The test results indicated that the chemical and crystal structure of MtS remained unaffected after the composite formation. The thermal conductivity of CAC90@GnP10/MtS was found to be 102.85% higher than CAC/MtS and 195.83% higher than MtS alone. The enhancement in thermal conductivity was further validated through observed reductions in melting and solidification times, as well as analysis using infrared thermal imaging. In conclusion, the development of these intelligent, multifunctional composite PCMs, which utilize CAC@GnP hybrids as supporter scaffolds and thermal conductivity enhancers for MtS, holds great promise for effective sustainable energy usage and thermal energy management systems in various fields like waste heat utilization, energy-saving buildings, constant temperature protection, thermal management of electronic devices, aerospace industry, textiles, automotive, and renewable energy systems.

Building energy efficiency evaluation based on fusion weight method and grey clustering method

The renovation and evaluation of building energy-saving projects can provide important support for building an energy-saving society. The study proposes using the contract energy management model to analyze building energy-saving projects and construct an evaluation index system. We also innovatively integrated the Analytic Hierarchy Process and Entropy Weight Method to calculate the weights of indicators, in order to leverage the effective influence of subjective and objective factors. Finally, we used Grey Cluster Analysis to obtain the evaluation effect of building energy-saving projects. Through weight calculation and evaluation analysis, it was found that the energy-saving rates of year-end electricity consumption and air conditioning electricity consumption in buildings after energy-saving renovation were 59.80% and 54.95%, respectively. The overall effectiveness of energy-saving buildings was above 50%, indicating a significant energy-saving effect. In the indicator evaluation system, the weight results of energy-saving service company indicators were relatively high, with values of 0.52, 0.48, and 0.51, respectively. The transformation effect was relatively good. The building energy-saving cost and economic benefits obtained from a 65% energy-saving rate were 3 million yuan and 530,000 yuan, respectively, which were significantly better than the simulation results of other energy-saving rates. The contract energy management model based on the fusion weight method and grey clustering method has superiority, which is effective for evaluating building energy-saving projects. It also provides technical reference and scientific suggestions for building energy-saving renovation.

Experimental Study on Mechanical Properties of Cured Sand Combined with Plant-Based Bio-cement (PBBC) and Organic Materials.

Bio-cement is a green and energy-saving building material, which has received wide attention in the field of ecological environment and geotechnical engineering in recent years. The aim of this study is to investigate the improvement effect of plant-based bio-cement (PBBC) in synergistic treatment of sand with organic materials, to highlight the effective use of tap water in PBBC, and to analyze the crack evolution pattern during the damage of specimens by using image processing techniques. The results showed that tap water can be used as a solvent for PBBC instead of deionized water. The characteristic trend of urease solutions prepared at different temperature environments was obvious, and the activity value of urease solution with low concentration is positively correlated with the ambient temperature, although the activity value is not high, it is not easy to inactivate. The incorporation of organic materials increased the peak stress up to 1809.30kPa compared to the specimens modified only by PBBC. The damage of the specimens under uniaxial compression consisted of four stages: compaction, elastic deformation, pre-peak brittle damage and post-peak macroscopic damage. The corresponding crack evolution is the interpenetration of small-sized cracks into large-sized main cracks. The large-sized main cracks transform into penetration cracks before damage, and the small-sized cracks are distributed around the penetration cracks. The crack evolution parameters obtained by MATLAB processing are positively correlated with the strain.

An Electro‐Driven Dynamic and Multicolored Radiative Thermal Regulation Material for All‐Year‐Round Building Energy Saving

AbstractRational dynamic thermal regulation of both solar and thermal regions is of significant importance for building energy saving. In this work, an electro‐driven dynamic radiative thermal regulation material (EDRTRM) capable of switching the thermal regulation capacity between the heating, white cooling, and multicolored cooling (blue, green, and yellow) modes is designed. These multi‐modes with high thermal regulation power and color variation are achieved through a synergistic material combination involving an electrochromism of Prussian blue (PB) and the electrodeposition of copper (Cu) with a polyformaldehyde (POM)‐based mid‐infrared (MIR) emitter. Optical characterization confirmed the superior spectral performance of materials, with a remarkable modulation capability of power density up to 659 W m−2, indicating an exceptional heating and cooling performance, which is evidenced by a temperature modulation difference of up to 11 °C. Notably, the EDRTRM under a multi‐colored cooling mode also achieves a temperature reduction of ≈ 4–6 °C. The EnergyPlus simulations demonstrate that the EDRTRM can save a huge amount of energy consumption of 16.56 MJ m−2 in cities with seasonal temperature variations such as Beijing. This dual‐functional design not only maximizes thermal regulation capabilities but also satisfies aesthetic requirements, showcasing its potential for widespread practical application.

Robust fluorinated cellulose composite aerogels incorporating radiative cooling and thermal insulation for regionally adaptable building thermal management.

Passive radiative cooling (PRC) is an emerging sustainable technology that plays a key role for achieving the goal of carbon neutrality. However, several challenges remain for PRC materials in their practical application in building thermal management, including overcooling problems and unsatisfactory cooling efficiency caused by solar absorption and parasitic heat gains. In this work, fluorinated cellulose-based composite aerogels (FCCA) integrating thermal insulation and PRC were developed by a facile manufacturing strategy that combined phase separation and freeze-drying. P(VdF-HFP) was utilized to promote the formation of nano/micro porous architectures in FCCA, resulting in a decrease in the thermal conductivity of the aerogel to 0.034 W m-1 K-1 while simultaneously increasing its solar reflectance and infrared emissivity (8-13 μm) to 95.74 % and 97.15 %, respectively. The aerogel cooler achieved a sub-ambient cooling temperature of ~9.68 °C during the daytime and maintained its cooling effectiveness even on cloudy days. The fluorinated aerogels demonstrated excellent hydrophobicity and chemical durability after outdoor exposure and heat aging tests. This work opens up a new pathway to design low-cost cellulose-based materials for efficient thermal management of energy-saving buildings around the world.

Application of Triple Glazing Thickness Optimization Based on Artificial Fish Swarm Algorithm

In response to the growing demand for energy-efficient building designs in cold northern regions, this study explores the optimization of triple glazing thickness to maximize the transmission of solar energy within the wavelength range of 300-2000 nm. The optimization employs the Artificial Fish Swarm Algorithm (AFSA), which is used to iteratively determine the optimal combination of glass thicknesses. A transmittance model of solar radiation through triple glazing is established, where the thicknesses of the three glass layers are treated as variables. The study shows that the optimized thickness combination significantly enhances the indoor heating effect by maximizing solar energy incidence, offering theoretical support and practical guidance for energy-saving building designs in cold climates. Parameter settings of the AFSA, including perception range, step size, and crowding factor, are analyzed to understand their influence on optimization performance. The results suggest that AFSA efficiently addresses complex optimization problems, demonstrating its potential in optimizing material properties for energy-efficient applications. Future directions include multi-objective optimization considering additional factors such as thermal insulation and cost, algorithmic improvements to enhance search accuracy, and experimental validation of the results in real-world conditions. This research provides a scientific foundation for integrating advanced optimization algorithms into the sustainable design of building materials.

Comparing the improvement of occupant thermal comfort with local heating devices in cold environments

Local heating can improve the thermal comfort of occupants and save energy in buildings in cold environments; however, few studies have investigated the effects of heat-transfer modes. Here, we aimed to evaluate different local heating measurements including five-sided enclosed radiant panel, heating plate, and fan heater using climate chamber experiments with 20 participants in cold environments (14 °C). Skin temperature and thermal perception votes under two radiation types with low and high power, one condition of conduction, and one condition of convection were collected and analyzed (RL, RH, CD, and CV). Under conditions RH, CD, and CV, the investigated parameters significantly improved by three local heating devices, with foot skin temperature rising by 0.46 °C, foot thermal sensation rising by 1.25 scores, and overall thermal comfort increasing by 0.36 score; however, their energy consumption varied greatly. In contrast, no significant improvement was observed in the RL group. Additionally, direct application of heat at sites of palpable cold discomfort was not always the optimal approach, and heating other parts of the body may provide significant alleviation. We recommend that the surface temperature of local heaters based on conduction and radiation for heat transfer should not be lower than 40.38 °C and 52.15 °C, respectively. To maintain thermal comfort, air outlet temperature should not be lower than 34.56 °C for convection type heaters. Our results provide technical and experimental basis for designing energy-saving buildings.

Fire-Safe Aerogels and Foams for Thermal Insulation: From Materials to Properties.

The ambition of human beings to create a comfortable environment for work and life in a sustainable way has triggered a great need for advanced thermal insulation materials in past decades. Aerogels and foams present great prospects as thermal insulators owing to their low density, good thermal insulation, mechanical robustness, and even high fire resistance. These merits make them suitable for many real-world applications, such as energy-saving building materials, thermally protective materials in aircrafts and battery, and warming fabrics. Despite great advances, to date there remains a lack of a comprehensive yet critical review on the thermal insulation materials. Herein, recent progresses in fire-safe thermal-insulating aerogels and foams are summarized, and pros/cons of three major categories of aerogels/foams (inorganic, organic and their hybrids) are discussed. Finally, key challenges associated with existing aerogels are discussed and some future opportunities are proposed. This review is expected to expedite the development of advanced aerogels and foams as fire-safe thermally insulating materials, and to help create a sustainable, safe, and energy-efficient society.

Dynamic optical and thermal modulation of electrochromic smart windows and sunglasses based on benzothiadiazole-extended viologen derivatives

Smart windows can regulate indoor lighting and heat intensity by isolating external light and heat, thereby achieving the goal of saving building energy consumption. However, traditional smart windows require additional power consumption to adjust color changes and thus regulate transmittance, and can only achieve relatively single control of light intensity and heat. Developing smart windows with dynamic photothermal modulation remains challenging. This paper reports two novel benzothiadiazole extended viologen derivatives DBTBB and DBTBH. The carboxymethylcellulose sodium hydrogel-state electrochromic devices based on DBTBB and DBTBH showed good electrochromic performance including a low operating voltage, a rapid response time, a high optical contrast, excellent cycling stability, and a large coloration efficiency. A dynamic photothermal modulation electrochromic smart window self-powered by a small commercial solar panel was constructed using the electrochromic hydrogel based on DBTBB, which could sense the changes in external irradiating light intensity and dynamically adjust the indoor light and heat without additional consumption of electricity, and the adjusting capability increased with the increase of irradiating light intensity. In addition, the application in smart color changing sunglasses self-powered by a solar panel was also investigated, the electrochromic sunglasses showed dynamic transmittance modulation in response to irradiating light intensities with good cycling stability, a gradual change in purple color from light to dark was observed as the irradiating light intensity increased from 105 → 225→415 → 650→920 lux. Moreover, both text and a colored logo were clearly displayed under different irradiating light intensities. This provides new methods for electrochromic applications in commercial settings and improving human quality of life, thereby creating new possibilities in the increasingly intelligent world.

Quantitative determination of vacuum degree of glass with photoelasticity

Vacuum glass is an environmentally friendly and energy-saving building glass. The degree of vacuum, which is a key factor associated to its characteristics, is of great interest to monitor during the service time. In this study, a real-time inspection method based on photoelasticity has been proposed to determine the vacuum degree of glass. The isochromatic phase map is achieved by means of real-time phase shifting while the polarized light passes through the glass and is recorded with a polarization camera. After the stress state of the glass near the support is analyzed with numerical modeling based on the stress-optic law and Mueller matrix multiplication, the relationship between the vacuum degree of glass and the equivalent radius near the support is established. An experimental illustration is presented on a piece of vacuum glass, which shows that the equivalent radius is effective parameter in identifying the degree of vacuum for the glass structures.

Innovative Energy Design for Energy Efficient Buildings - An Example from the Bullitt Center

In recent years, the extreme climate caused by global warming has brought serious consequences to the world. In order to alleviate the problem of global warming, many scholars have started to analyse energy-saving green buildings. Taking the Bullitt Center as an example, this paper illustrates the innovative applications of energy-efficient buildings in solar power generation, rainwater collection and utilization, toilet water conservation and resource utilization and room temperature regulation. It focuses on the differences in the use of solar power generation in winter and summer, the process of purification of rainwater into water, the comparison between composting toilets and vacuum toilets and the steps of regulating the room temperature by windows and ground-source heat pumps. This paper also talks about the limitations of these innovative applications. It could probably give reference to the subsequent construction of buildings, thus promoting energy saving and emission reduction in buildings and mitigating global warming.

Adaptive Control for Hydronic Radiant Heating System Using Occupant Behaviors in Residential Building

This study proposes an occupant-centric control strategy for residential heating systems, aiming to enhance thermal comfort and reduce energy consumption. A sensor station utilizing a frequency-modulated continuous wave radar sensor was developed to detect occupancy and infer activities within residential spaces. By analyzing field measurement data, schedules for occupancy and activities were established. These schedules were then used to implement a variable control strategy for the hydronic radiant heating system, adjusting its operating characteristics based on the identified activities. The proposed control strategy, which includes resetting the indoor set temperature during unoccupied periods and adjusting it during sleep to account for changes in metabolic rate and clothing insulation, resulted in significant energy savings. Compared to continuous operation, the hydronic radiant heating system’s energy consumption was reduced by approximately 21% on peak load days and up to 34% over three winter months. This study demonstrates the potential of occupant-centric control for achieving substantial energy savings in residential buildings while maintaining occupant thermal comfort.

A Multimode Dynamic Color-Changing Device for Smart Windows Based on Integrating Thermochromic and Electrochromic Properties.

Electro- and thermochromic materials have been greatly applied in smart windows and displays due to the excellent properties of color variation and solar radiation. However, the mono color and single response to voltage and temperature hinder their application and development. Here, a multimode dynamic color-changing device (T/ECD) was developed by integrating the electrochromic property of synthetic viologen dyes and the thermochromic properties of hydroxypropyl acrylate (HPA). The T/ECD achieves four modes of optical regulation, namely, colorless transparent state, tinted transparent state, colorless opaque state, and tinted opaque state, which can be regulated independently/coordinately using heat and voltage. The optimized T/ECD switched color at 1.2 V with 15 s or adjusted the transparent/opaque state at >34 °C with 46 s. In addition, based on the red viologen (ViO-R), green viologen (ViO-G), and blue viologen (ViO-B) dyes, colorful T/ECDs were successfully designed and fabricated, and T/ECDs have excellent cycling properties, expanding the application requirement. Moreover, we demonstrated their application in smart windows and privacy protection. The design philosophy and successful exploration have great prospects for energy-saving buildings, displays, and information masking/storage systems.

Thermal-deformation behaviors of the primary sealants in double, triple, and multi glazed insulating glass units

Polyisobutylene (PIB), commonly used as the primary sealant of double, triple, and multi glazed insulating glass units (IGUs), provides the key moisture barrier function and determines the expected lifespan of the IGUs and even the entire glass curtain wall systems (GCWSs). Slipping and debonding of the PIB, caused by temperature changes, have resulted in numerous instances of premature failure of building envelopes. However, available research is inadequate in accurately evaluating the service environment of IGUs and thermal-deformation behaviors of this energy-saving building material. This paper presented a simplified method for analyzing the thermal environment of IGUs, considering outdoor air temperature, solar radiation, wind speed, and angle to the horizontal. A numerical modeling method was proposed and validated with the heat transfer tests. Three finite element (FE) models were built and utilized for the precise analysis of temperature-induced deformations of double, tripled, and quadruple glazed IGUs. Simplified calculation formulas for the maximum thermal deformation of PIB in the X and Y directions under different temperature conditions were obtained, taking a new concept “cavity-to-pane ratio” into consideration. Finally, the relationship between the PIB’s temperature-induced deformation and its probability was proposed. The results show that the IGUs in Beijing suffer more than 22 % of their time in harsh service conditions where the difference between indoor and outdoor temperatures exceeds 20 °C. For DIGUs, the maximum temperature-induced deformations of the PIB in X (along the short side of the panel) and Y (along the long side of the panel) directions are 0.142 and 0.214 mm, respectively, corresponding to shear strains of 28.4 % and 42.8 % for the PIB with a thickness of only 0.5 mm. For TIGUs, the maximum deformations increase to 0.159 and 0.239 mm, corresponding to shear strains of 31.8 % and 47.8 %. For QIGUs and the other multi-glazed IGUs, these values can increase to 36.8 % and 55.4 % or more. The methodology proposed in this paper aims to lay the groundwork for further addressing premature failure issues and optimizing edge bond constructions of multi-glazed IGUs.

Building Energy Savings and Power Output Augmentation of Roof Mounted PV Using Co-Located Rooftop Reflectors

Abstract Photovoltaic panels (PVs) installed on building rooftops yield a positive influence on the thermal performance of the building due to the shading of the PV panels, decreasing cooling loads while causing a smaller increase in heating loads. Additionally, the electrical power output of PV panels has been shown to be increased by including reflectors between PV rows, concentrating the solar flux onto the active portion of the panels. When implemented into the spaces between the rows of a roof-mounted PV array, reflectors might further improve the positive thermal effects of rooftop installed PV arrays. This work focuses on predicting rooftop heat flux and temperature for a building rooftop equipped with PV panels and reflectors. The Saved Energy Load (SEL), Additional Energy Load (AEL), PV power output, rooftop heat flux and the utility factor (ratio of positive building energy impacts to negative building energy impacts) are reported parametrically for variations in the rooftop absorptivity and reflector area for three United States locations. Utility factors of 375, 140 and 160 are found for Phoenix, Boise and Dayton, respectively, for a reflector covering the full area between panels with a roof having a minimal absorptivity. A building in Phoenix exhibits a 15% increase in the utility factor of the PV-building system when reflectors are incorporated compared against a PV-building system without reflectors, while a building in Dayton showed a 22% increase in utility factor when reflectors are included between the rows of a roof-mounted PV array.

Achieving Broadband Microwave Shielding, Thermal Management, and Smart Window in Energy‐Efficient Buildings

AbstractEnergy‐efficient building materials are eye‐catching for reducing indoor energy consumption via eliminating electromagnetic interference and pollution, controlling the thermal transfer, and promoting sunlight harvesting and providing a comfortable living environment. To realize broadband microwave shielding, the elaborate control of microstructures has showed great potential and research direction. By composition regulation and structure design with various dimension, the synergistic effects including conductive networks, interfacial polarization, magnetic coupling, dipole polarization, and dielectric‐magnetic synergy, can significantly improve electromagnetic (EM) shielding capacity. Thermal management including thermal conversion, thermal storage, thermal radiation, and thermal conduction has enormous potential in enhancing the sustainability and energy efficiency for future buildings. Smart windows are able to switch optical transmittance and colors, which is contributed to saving building energy. Herein, in this review, the recent progress of broadband shielding, thermal management, and smart window in the field of energy‐efficient buildings is summarized, from the aspects of materials, mechanisms, and scenarios. Further, the main bottlenecks and problems are discussed, and potential research opportunities are further highlighted.

Testing the use of daylight-linked control systems to address integrative lighting and energy savings in office buildings

Daylight-linked control systems (DLCSs) are used to maintain constant work plane illuminance and save energy. If properly calibrated, they could be used to guarantee circadian requirements fulfilment as well. In this study, the functioning of a closed-loop proportional dimming system is simulated based on on-field measurements. Simulations are performed calibrating the system to achieve different targets: three work plane task illuminances (300 lx, 500 lx, 750 lx) and one melanopic equivalent daylight illuminance (melEDI) value (250 lx) alternatively. Four electric light CCT profiles (stable at 3000 K, 4000 K, and 6500 K, and variable during the day) are considered. Results demonstrate that when the system is calibrated according to work plane illuminance, melEDI values are always fulfilled under clear sky and with overcast sky when task illuminance and CCT are high. When the system is calibrated to meet circadian requirements, the CCT choice is crucial to guarantee work plane illuminance.