Indoor Energy Research Articles

Vertically oriented low-dimensional perovskites for high-efficiency wide band gap perovskite solar cells.

Controlling crystal growth alignment in low-dimensional perovskites (LDPs) for solar cells has been a persistent challenge, especially for low-n LDPs (n < 3, n is the number of octahedral sheets) with wide band gaps (>1.7 eV) impeding charge flow. Here we overcome such transport limits by inducing vertical crystal growth through the addition of chlorine to the precursor solution. In contrast to 3D halide perovskites (APbX3), we find that Cl substitutes I in the equatorial position of the unit cell, inducing a vertical strain in the perovskite octahedra, and is critical for initiating vertical growth. Atomistic modelling demonstrates the thermodynamic stability and miscibility of Cl/I structures indicating the preferential arrangement for Cl-incorporation at I-sites. Vertical alignment persists at the solar cell level, giving rise to a record 9.4% power conversion efficiency with a 1.4 V open circuit voltage, the highest reported for a 2 eV wide band gap device. This study demonstrates an atomic-level understanding of crystal tunability in low-n LDPs and unlocks new device possibilities for smart solar facades and indoor energy generation.

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.

Additive engineering for Sb2S3 indoor photovoltaics with efficiency exceeding 17%

Indoor photovoltaics (IPVs) have attracted increasing attention for sustainably powering Internet of Things (IoT) electronics. Sb2S3 is a promising IPV candidate material with a bandgap of ~1.75 eV, which is near the optimal value for indoor energy harvesting. However, the performance of Sb2S3 solar cells is limited by nonradiative recombination, which is dependent on the quality of the absorber films. Additive engineering is an effective strategy to fine tune the properties of solution-processed films. This work shows that the addition of monoethanolamine (MEA) into the precursor solution allows the nucleation and growth of Sb2S3 films to be controlled, enabling the deposition of high-quality Sb2S3 absorbers with reduced grain boundary density, optimized band positions, and increased carrier concentration. Complemented with computations, it is revealed that the incorporation of MEA leads to a more efficient and energetically favorable deposition for enhanced heterogeneous nucleation on the substrate, which increases the grain size and accelerates the deposition rate of Sb2S3 films. Due to suppressed carrier recombination and improved charge-carrier transport in Sb2S3 absorber films, the MEA-modulated Sb2S3 solar cell yields a power conversion efficiency (PCE) of 7.22% under AM1.5 G illumination, and an IPV PCE of 17.55% under 1000 lux white light emitting diode (WLED) illumination, which is the highest yet reported for Sb2S3 IPVs. Furthermore, we construct high performance large-area Sb2S3 IPV minimodules to power IoT wireless sensors, and realize the long-term continuous recording of environmental parameters under WLED illumination in an office. This work highlights the great prospect of Sb2S3 photovoltaics for indoor energy harvesting.

Research on Application of Composite Facades for Civilian Reconstruction of Industrial Heritage in Cold Regions Based on Thermal Buffering Effect

Previous studies on the civil transformation of industrial heritage have been conducted mainly from the perspective of architectural history, culture and aesthetics, but rarely focus on energy-saving and the comfort of the new users. Most industrial heritage facades are of high conservation value, but efforts to preserve the authenticity of the facade can lead to the application of limited energy-saving technologies, ultimately resulting in poor indoor thermal environments. Therefore, it is valuable to research how to solve the contradiction between protecting the authenticity of the preserved facades of industrial heritage and improving the indoor environmental performance. This paper proposes two composite facade application strategies based on thermal buffer effects, takes two composite facades renovation methods of Shenyang Dongmao No. 2 Warehouse as an example, utilizes the natural environmental resources to enhance the spatial quality of industrial heritage. With the help of DesignBuilder software modelling simulation analysis, in-depth comparative analysis of the two types of composite facades on the indoor thermal environment of the industrial heritage of the impact and scope. Key findings show that the application of two different composite facade retrofitting techniques not only protects the skin texture of the wall, but also effectively increases the indoor temperature and reduces the indoor energy consumption of the industrial heritage. The composite facade of the external solid wall and the internal glass is more stable in raising the indoor temperature, more effective in reducing the building energy consumption, and more suitable for the civilian transformation of industrial heritage in cold areas. The research findings provide reference for studies on the civil transformation of industrial heritage, and serve as technical references for architects.

Utilizing molecular states of carbon quantum dots (CQDs) to efficiently harvest outdoor and indoor energy via luminescent solar concentrator

Luminescent solar concentrators (LSCs) offer a huge potential for electricity generation due to their ability to harvest direct and diffused light. Among numerous fluorophores for LSCs, carbon quantum dots (C-QDs) are promising candidates due to their non-toxic nature, tunable optical features, and cost-effective synthesis. State-of-the-art LSCs utilizing C-QDs focus on solar energy harvesting, while their potential to harness indoor light for electricity generation is yet to be explored. In this study, we rationally fabricated C-QDs based LSC for efficient energy harvesting under both outdoor and indoor illuminations. Through a facile solvothermal pyrolysis technique, we synthesized the molecular states assisted C-QDs exhibiting a strong absorbance in the visible region that matched well with the outdoor and indoor light spectra. Laminated LSCs were fabricated by coating C-QDs/polyvinyl alcohol (PVA) film (photoluminescence quantum yield 71 %) on two glass substrates and joining them with an interlayer of refractive index matching polymer. Given geometry not only protects C-QDs/PVA film from external damage but also prevents light scattering losses that were prominent in an open C-QDs/PVA layer. External efficiency (ηext) of the small-to-large area LSCs under different illuminations were estimated using an analytical approach. The results showed that under outdoor (air mass 1.5 global spectrum) illumination and without scattering background, a large-area (10 × 10 × 0.6 cm3) LSC at an optimized concentration of C-QDs exhibited ηext of 3.1 %. When connected with the silicon PV cell, the same LSC yielded a power conversion efficiency (ηPCE) of 0.34 %. Among various indoor illuminations (light-emitting diode (LED)-daylight, LED-warm white, and fluorescent-daylight (CFL)), the best performance was shown under LED-daylight with the ηext and ηPCE of 7.4 % and 0.30 %, respectively. This study offers enormous potential for the adoption of C-QDs based LSC not only in building exteriors (such as windows and facades) but also in the places where artificial lights are used.

Crowd Density Level Classification for Service Waiting Room Based on Head Detection to Enhance Visitor Experience

The crowd within a confined space can potentially lead to air stagnation in waiting areas. Constantly running air conditioning throughout the day to balance air circulation may result in excessive energy consumption by the building. To address this issue, Heating, Ventilating, and Air-Conditioning (HVAC) systems are employed to manage and regulate indoor energy usage. However, sensor-based detection often fails to capture human variables promptly, resulting in less accurate density readings. Camera footage proves to be more reliable than sensors in accurately detecting crowds. This research utilizes You Only Look Once version 8 (YOLOv8), a robust algorithm for object detection, particularly effective in crowd detection for images, along with Convolutional Vision Transformer (CvT) for crowd density level classification into "Normal" and "Crowded" levels. CvT enhances classification accuracy by incorporating function from Convolutional Neural Network (CNN) in model training, including receptive field, shared weights, etc. By integrating YOLOv8 and CvT, this method focuses on accurately classifying crowd density levels after identifying human presence in the waiting area (indoor). Evaluation metrics include mean Average Precision (mAP) for YOLOv8, and accuracy, precision, recall, and f1-score for CvT. This approach directly influences the management of HVAC systems.

Determination of light-independent shunt resistance in CIGS photovoltaic cells using a collection function-based model

Shunt resistance Rsh is a critical parameter for photovoltaic cells designed for low light indoor applications because it negatively affects the open circuit voltage, fill factor, and conversion efficiency. Standard CIGS cells are known to have low Rsh and are, therefore, unpromising candidates for indoor energy sources. In this paper, we extend the original work of Virtuani et al. by determining the electrical specifications of many CIGS cells with copper contents [Cu]/([Ga]+[In]) as low as 0.33 and gallium contents between 0.28 and 0.81. First, IV data are fitted by a standard single-diode electrical circuit model for each illumination, resulting in light-dependent parameters. Then, we use a procedure based on a single dataset of electrical variables, i.e., independent of light, corrected by the experimental collection function, which captures light-dependent physical mechanisms. In this way, we are able to correctly reproduce the illuminance dependence of the electrical response of the PV cell over three orders of magnitude, in particular with a fixed value of the shunt resistance. The highest Rsh is obtained with a low copper composition of 0.5, regardless of the gallium composition.

Do blue-green roofs yield optimal thermal performance? Synergy analysis of the combination of green roofs and water retention layer

Blue-green roofs can potentially enhance the outdoor thermal environment in urban areas and reduce indoor energy consumption. By integrating a water retention layer with green roofs, blue-green roofs maximize environmental benefits through rainwater storage and increased evapotranspiration. This study evaluates the thermal performance of blue-green roofs during summer and examines their potential for microclimate improvement and energy savings. The study investigates the individual and interactive effects of the blue-green roof components by measuring the upper and lower surface temperatures with incremental application of soil, blue, and green layers and analyzing their synergistic benefits. The results indicate that blue-green roofs exhibited a cooling effect of up to 7.5 °C on the upper surface temperature and up to 17.4 °C on the lower surface temperature, showing the greatest potential for improving indoor and outdoor thermal comfort. The synergistic effect of the blue-green roof was −0.80 °C on the upper surface and +1.59 °C on the lower surface. This research provides an in-depth investigation into the thermal performance of blue-green roofs in both indoor and outdoor spaces, highlighting their synergistic effects through incremental application. This contributes to climate-responsive architectural design and practices aimed at enhancing energy efficiency in building retrofitting for hot climates.

Recent Developments of Next-generation Smart Window using Metal Electrodeposition

Due to the energy and environmental crisis, indoor energy efficiency is of great importance. One of the solutions to cope with the problem is adopting a device with energy-saving functionality. From that perspective, smart window technology has received the foremost attention as of great potential, because it could modulate the solar energy stream such as light and heat. In addition to that, smart windows could offer visual aesthetic operation to our daily lives. Despite many technical attempts, no technology has been commercialized abruptly due to the restrictions or disadvantages. One of the rising options is a smart window based on reversible metal electrodeposition, as metal electrodeposits possess high contrast with color neutrality, and high coloration efficiency for privacy state. Since 2017, reversible metal electrodeposition-based smart window technology has been emerging, and advancing in terms of cycling, bistability, and color uniformity. This review aims to summarize the current technological trends and directions for the development of reversible metal electrodeposition-based smart window technologies.

Application of energy scheduling algorithm based on energy consumption prediction in smart home energy scheduling

To effectively optimize household energy management, enhance user comfort, and ensure the stability of the power grid, this paper directs its focus towards household equipment and presents inter-household and indoor energy scheduling algorithms. Grounded in a two-dimensional dynamic device priority framework and predictive device operation modeling, this study demonstrates that the utilization of scheduling algorithms can avert grid overload scenarios during periods of low electricity prices. This results in more consistent hourly electricity consumption and a substantial peak-to-average ratio reduction of up to 44.86 %. Additionally, the application of the continuous wavelet neural network algorithm proves to be proficient in accurately forecasting home device operations. When the time was 17.5 h, the actual energy consumption of the water heater was 7.12 kWh, which was 0.78 kWh more than the predicted energy consumption. Utilizing scheduling algorithms, as opposed to not employing them, led to notable reductions in electricity expenses, demonstrating a cost savings rate of 15.32 % on the third day. Additionally, it facilitated decreased usage of the power grid. When the time was 18 o'clock, the power consumption of the grid using scheduling algorithms was 0.24 kWh, which was 0.25 kWh lower than that without scheduling algorithms. Following the implementation of the scheduling algorithm, minimal deviation in device startup times was observed during periods of high comfort, with offsets ranging from 0 h. The research methods employed demonstrate efficacy in orchestrating energy distribution among households and indoor spaces, thereby striking a harmonious balance between energy conservation and user comfort.

Indoor photovoltaics: A numerical model of dye-sensitized solar cells based on indoor illumination for the Internet of Things applications

Since dye-sensitized solar cells (DSSC) have a suitable efficiency in the invisible region, they present a promising avenue for sustainable energy generation, particularly in the context of indoor environments where ambient lighting prevails. This paper proposes a novel numerical model tailored to assess the performance of DSSCs under indoor lighting conditions, with a specific focus on their potential application in powering Internet of Things (IoT) devices. By considering factors such as radiation intensity and spectral composition, particularly from common indoor light sources like Light Emitting Diodes (LEDs) and Fluorescent lights, the model offers insights into the efficiency and viability of DSSCs in indoor settings. Since empirical analyses are difficult and expensive, the existence of a numerical model that investigates cell behavior under indoor illumination can be beneficial for developing such cells. In conducting verifying analyses under varying lighting conditions, the study demonstrates notable efficiencies of DSSCs, with LED 3000 K illumination at 1000 lux intensity yielding the highest performance. While DSSCs may appear less economically viable in environments with readily available electricity, their potential significance lies in providing sustainable energy solutions for IoT devices, thus reducing dependency on conventional power sources and contributing to environmental sustainability. The scientific significance of this research lies in its contribution to understanding the behavior of DSSCs under indoor lighting, offering insights into their potential applications in powering IoT devices. By providing a numerical model for evaluating DSSC performance under realistic indoor conditions, this study opens avenues for further research in optimizing DSSC technology for indoor energy harvesting applications, thereby advancing the field of renewable energy and sustainable technology integration.

Enhanced power supply circuitry with long duration and high‐efficiency charging for indoor photovoltaic energy harvesting internet of things end device

AbstractLight is a popular choice as an indoor energy source for Internet of Things (IoT) end devices. However, indoor light sources are intermittent, which can disrupt the operation of IoT end devices, potentially leading to safety concerns or inaccurate data. Therefore, there is a growing need to develop a long‐duration power supply for IoT end devices. The energy from ambient light is harnessed to charge a supercapacitor through an energy manager chip. This supercapacitor serves as the power source for IoT nodes when the ambient light is unavailable. Nevertheless, as the voltage of the supercapacitor drops below the operating threshold, the IoT end node will eventually shut down. This paper proposes a circuit that utilizes a Joule Thief circuit, booster converter, and capacitor stack‐up circuit to extract the remaining energy from the supercapacitor and boost the voltage, thereby extending the operational lifespan of IoT end nodes. Additionally, capacitor stack‐up circuits significantly enhance charging efficiency. PSpice design and simulations confirm circuit feasibility. High‐efficiency charging and long‐duration IoT nodes suggest replacing traditional batteries with supercapacitors, reducing environmental impact.

Trade-Off Judgement for Daylighting and Energy Consumption in the High and Large Space of the University Gymnasium in Beijing

Taking the high and large space of the University of Science and Technology Beijing Gymnasium as this research object, this paper analyzes the influence of different window positions, window-to-wall ratio (WWR), solar heat gain coefficient (SHGC), heat transfer coefficient (K), and visible light transmittance (VT) on the total indoor energy consumption in winter and summer and obtains the relationship between the daylight factor and VT formed when the window is opened per unit area. Through energy consumption simulation, the variation law and calculation formula for indoor total energy consumption are obtained. The results show that the SHGC and K of the exterior window have a significant influence on the total energy consumption. By using the energy consumption simulation of different types of exterior windows, it is concluded that the SHGC of the south-facing window is negatively correlated with the variation of air conditioning energy consumption per unit area Δe1,w, while the others are positively correlated. Moreover, the SHGC and K of the skylight have the most significant influence on the Δe1,w. The total energy consumption decreases and then increases with the increase in the window area, and there is a lowest point, so the right side of the lowest point is less than or equal to 105% of the lowest total energy consumption as a reasonable window area zone. Finally, a progressive optimization method for weighing daylighting and energy consumption in university gymnasiums in Beijing is proposed.

Anti-Fatigue Tandem Organic Photovoltaics for Indoor Illumination.

The ability of achieving high efficiency makes tandem organic photovoltaics (PVs) a competitive technique in potential indoor applications. Except high efficiency, reliable indoor energy supply also calls for outstanding stability. However, unavoidable unstable voltage supply from the circuit control system for indoor light sources like light emitting diodes (LED) and incandescent lamps would cause carrier density fluctuation and device fatigue driven by periodic light/dark switching. In this work, the strobing-induced fatigue within the bulk heterojunction (BHJ)/interconnecting layer (ICL) interface is first revealed and overcome. Based on reliable and effective interfacial doping between conjugated acceptor and metal oxide, the interfacial capacitance that determines the strobing-induced fatigue, has been significantly restrained. The imbalance carrier migration and fierce inter-layer accommodating during the burn-in stage caused by light strobing are substantially diminished. Benefit from this method, the stability of tandem devices is highly enhanced under strobing indoor illumination, and a champion efficiency (35.02%) is obtained. The method provides guidance for further material design for interconnecting layers in organic photovoltaics.

Indoor environment PV applications: Estimation of the maximum harvestable power

The use of PV modules for powering sensors in an indoor environment requires that, during the design process, the harvestable power be evaluated and compared with the power requirements of the load device to validate their compatibility for a given type of light source and level of illumination. The models reported recently to relate power to illumination during power estimation are seen to result in large estimation errors in the case of an indoor environment. This paper seeks to propose an appropriate model that can be exploited during maximum power estimation in an indoor environment to relate power to illumination level. Proceeding from fitting measured data to the three-diode model of the PV module and based on the errors and execution time, the Grey Wolf Optimisation Algorithm, among others, proved to be accurate for estimating maximum power. The relationship between maximum power and illumination was seen to take the form of a second-degree polynomial. This was validated by comparing the values of power estimated by this model to the measured values as well as values estimated with the linear model, the exponential model, and the model proposed by Joseph Amajama. The proposed model proved to be more accurate than the models reported, recording errors of not more than 5 %, which is acceptable for system design. This will go a long way towards facilitating the design of indoor energy harvesting systems that can be used for powering smart sensors and other IoT devices.

IOT Implementation Energy consumption for Indoor Orchid Cultivation based on WeMos

Orchids are epiphytic plants with high popularity. Orchid is a plant that can process its own nutrients with the help of other media. Parameters that need to be monitored include air temperature, air humidity, and soil moisture. These parameters greatly affect plant growth. Plants can grow well if humidity, temperature, and light intensity are met properly. Good orchid humidity ranges from 50 – 80%. Humidity should not be too high at night and not too low during the day. In addition to humidity, the temperature where you plant orchids must also be maintained. The ideal temperature for orchids is daytime temperatures between 27-30 degrees Celsius and night temperatures between 21-24 degrees Celsius. Based on these problems, a Design and Development Tool for Monitoring Soil Temperature and Moisture on the Growth of Indoor Orchid Plants is Based on WeMos with Indoor Energy. In this design, the results of sensor readings will be displayed in the form of data which will be accessed via the web server on WeMos. To read the temperature, air humidity, and soil moisture, several sensors are used, namely: DHT 22, soil moisture sensor, and a relay connected to a mini water pump using an indoor cultivation method where the energy source uses UV waves by LED light. From the results of the implementation and testing, the growth period will be obtained more faster than the normal cultivation. hopefully, this research will help people who care for orchid plants to be able to monitor their orchid plants efficiently in indoor conditions so that these orchid plants can always be in the best conditions of temperature, light, and soil moisture.

Indoor light energy harvesting technique to energize a heat sensor using polycrystalline solar panel

This paper presents the effect of using different illumination types between the polycrystalline solar panel and the light sources on energy harvesting performance for indoor low-power applications such as heat sensors. The main advantage of indoor energy harvesting is it makes good use of ambient energy from the environment and converts it directly to electricity for small power devices. In this paper, the maximum power of polycrystalline solar panels for four different light illuminations has been investigated under different distances of light sources from the polycrystalline solar panel. Implementation and test results of the effect of varying the distance and the power produced for different light illuminations are presented which highlights the practical issues and limitations of the system.

Investigation of Greening Façade and Retrofitting strategies on Outdoor Thermal Comfort and Indoor Energy Consumption in New Assiut City, Egypt

Investigation of Greening Façade and Retrofitting strategies on Outdoor Thermal Comfort and Indoor Energy Consumption in New Assiut City, Egypt

Indoor environmental quality and energy use intensity: an empirical post-occupancy evaluation test of on-campus university student housing in Ghana

PurposeTo significantly adopt and improve indoor energy efficiency in building infrastructure in developing countries can be a challenging venture. Thus, this study aimed to assess the satisfaction of indoor environmental quality and its effect on energy use intensity and efficient among student housing.Design/methodology/approachThe study is quantitative and hinged on the contrast theory. A survey of 1,078 student residents living in purpose-built student housing was contacted. Using Post-Occupancy Evaluation and Multiple Linear Regression, critical variables such as thermal comfort, visual comfort and indoor air quality and 21 indicators were assessed. Data on annual energy consumption and total square metre of the indoor area were utilised to assess energy use intensity.FindingsThe study found a direct relationship between satisfaction with indoor environmental quality and energy use intensity. The study showed that students were more satisfied with thermal comfort conditions than visual and indoor air quality. Overall, these indicators contributed to 75.9% kWh/m2 minimum and 43.2% kWh/m2 maximum energy use intensity in student housing in Ghana. High occupancy and small useable space in student housing resulted in high energy use intensity.Practical implicationsInclusions of sustainable designs and installation of smart mechanical systems are feedback to student housing designers. Again, adaptation to retrofitting ideas can facilitate energy efficiency in the current state of student housing in Ghana.Originality/valueEarlier studies have argued for and against the satisfaction of indoor environmental quality in student housing. However, these studies have neglected to examine the impact on energy use intensity. This is novel because the assessment of energy use intensity in this study has a positive influence on active design incorporation among student housing.

Effect of Protective Layer on the Performance of Monocrystalline Silicon Cell for Indoor Light Harvesting.

The development of renewable energy sources has grown increasingly as the world shifts toward lowering carbon emissions and supporting sustainability. Solar energy is one of the most promising renewable energy sources, and its harvesting potential has gone beyond typical solar panels to small, portable devices. Also, the trend toward smart buildings is becoming more prevalent at the same time as sensors and small devices are becoming more integrated, and the demand for dependable, sustainable energy sources will increase. Our work aims to tackle the issue of identifying the most suitable protective layer for small optical devices that can efficiently utilize indoor light sources. To conduct our research, we designed and tested a model that allowed us to compare the performance of many small panels made of monocrystalline cells laminated with three different materials: epoxy resin, an ethylene-tetrafluoroethylene copolymer (ETFE), and polyethylene terephthalate (PET), under varying light intensities from LED and CFL sources. The methods employed encompass contact angle measurements of the protective layers, providing insights into their wettability and hydrophobicity, which indicates protective layer performance against humidity. Reflection spectroscopy was used to evaluate the panels' reflectance properties across different wavelengths, which affect the light amount arrived at the solar cell. Furthermore, we characterized the PV panels' electrical behavior by measuring short-circuit current (ISC), open-circuit voltage (VOC), maximum power output (Pmax), fill factor (FF), and load resistance (R). Our findings offer valuable insights into each PV panel's performance and the protective layer material's effect. Panels with ETFE layers exhibited remarkable hydrophobicity with a mean contact angle of 77.7°, indicating resistance against humidity-related effects. Also, panels with ETFE layers consistently outperformed others as they had the highest open circuit voltage (VOC) ranging between 1.63-4.08 V, fill factor (FF) between 35.9-67.3%, and lowest load resistance (R) ranging between 11,268-772 KΩ.cm-2 under diverse light intensities from various light sources, as determined by our results. This makes ETFE panels a promising option for indoor energy harvesting, especially for powering sensors with low power requirements. This information could influence future research in developing energy harvesting solutions, thereby making a valuable contribution to the progress of sustainable energy technology.