Reduce Building Energy Research Articles

Enhancing the thermal storage performance of biochar/paraffin composite phase change materials: Effect of oleophobic modification of biochar

Composite phase change materials (PCMs) possess excellent temperature-regulating capabilities, which can effectively reduce building energy consumption, ultimately contribute to energy saving and carbon reduction. In this study, oleophobic modification was carried out on the Zn modified - white pine biochar. The resultant oleophobic material (Zn-WPC-A) showed excellent supporting capability in the preparation of paraffin wax (PW)/biochar composite PCMs (PW/Zn-WPC-A). The oleophobic properties of biochar could effectively prevent PW leakage, and resulted in a high PW loading rate of 84.26% and an encapsulation efficiency of 82.26%. Zn-WPC-A demonstrated good physical and chemical compatibility with PW. The inclusion of Zn-WPC-A effectively promoted the nucleation in the crystallization process of PW. PW/Zn-WPC-A exhibited a thermal conductivity 3.28 times that of pure PW, displaying excellent thermal responsiveness. The fusion enthalpy of PW/Zn-WPC-A was 107.2 J/g. Furthermore, it displayed excellent stability within the working temperature range with no leakage observed. Simulated housing application experiments illustrated that the use of PW/Zn-WPC-A as building insulation material effectively slowed down the variation rate of indoor temperature. Therefore, the composite PCM using oleophobic modified biochar as supporting material showed excellent thermal performance and strong temperature-regulating capability.

Green Retrofitting of Building using BIM-based Sustainability Optimization

The construction industry consumes around 55 percent of Pakistan’s annual energy and is the country’s most energy-intensive sector. It is, therefore, significant to devise a novel and effective model of green retrofitting of current buildings based on Building Information Modelling (BIM) which aims to reduce building energy consumption to effectively meet diversified climatic concerns and to promote sustainable structures. This research aims to reform the existing building by modifying the design parameters for an inefficient building envelope based on BIM simulation and data optimization results to optimize the overall energy consumption. BIM tools, such as Autodesk Revit and DesignBuilder have been used for the evaluation of the optimized energy-efficient design by comparing different design alternatives. After a detailed analysis, this research has concluded that the existing building is consuming a high amount of annual energy. With the help of BIM tools, which possess advanced algorithms for an effective optimization process, a list of ‘green’ solutions i.e., optimal designs has been generated, out of which the optimal and cost-effective design saved 46% of energy in total. In this study, the design variables selection has been fulfilled according to the local environmental sustainability.

Optimization of energy-saving renovation technology for existing buildings in a hot summer and cold winter area

Retrofitting existing buildings significantly improves indoor thermal comfort and reduces building energy consumption and greenhouse gas emissions. The optimal combination of energy-saving technologies can improve the energy performance of a specific building. The effective energy-saving renovation of existing buildings is vital for improving the poor indoor comfort and high building energy consumption caused by the inadequate thermal performance of the external enclosure structure. This study proposed a new multi-objective optimization model based on Latin hypercube sampling (LHS). It combines a genetic algorithm (GA) with an artificial neural network (ANN) to evaluate and optimize the technology used for retrofitting projects, aiming to provide solutions for the energy-saving renovation of existing buildings. This study selected an old building in a hot-summer and cold-winter area for the retrofitting project, aiming to optimize indoor comfort, building energy consumption, and retrofitting cost. The proposed model was used to determine the optimum energy-saving technology combinations suitable for the building. The results showed that the optimized model could be used to explore conflicting objectives and determine the Pareto front when retrofitting existing buildings. Subsequently, the optimal technology combinations included using energy-efficient PVC Low-E double-glazed windows (5+6A+5) and XPS insulation with a thickness of 0.315m for the roof and external walls.

Energy savings in HVAC systems by continuous monitoring. Results of a long term monitoring campaign on buildings.

The European EPBD (Energy Performance in Buildings Directive) imposes mandatory inspection of HVAC systems with the aim of reducing building energy consumption and CO2 emission. Even if an inspection methodology was developed by HARMONAC IEE project, only few member states include mandatory inspection in national legislation. The methodology was tested on 400 buildings around Europe, showing some general problems on HVAC control. The main issue concerns HVAC system monitoring: without reliable energy consumption data, it is really difficult to achieve the EPBD main aim, the reduction of energy consumption. In this paper some examples are shown, demonstrating the importance of energy monitoring and correct HVAC control set up.

Efficient space heating in a Portuguese Public Building Replacement of a Liquefied Petroleum Gas Boiler by Heat Pump

Buildings are responsible for approximately 40% of the total world annual energy consumption, putting them among the largest end-use sectors. Especially important has been the increase of energy consumption in HVAC systems, which has become essential in the demand for thermal comfort. The introduction and recent amendments to the European Energy Performance of Buildings Directive demonstrate growing recognition among the policy community of the importance of energy efficiency in the building sector. The implementation of energy efficient measures, without compromising comfort level of building’s occupants, can significantly reduce energy consumption in buildings, the energy bills and the correspondent greenhouse gas emissions. In the building sector there are several energy conservation measures that can be implemented to reduce building energy consumption, namely four main areas: space heating, space cooling, domestic hot water and artificial lighting. This paper presents a simple case study used to compare an efficient electric heat pump with a conventional system for a public building space heating purposes. The study has been performed using two software tools: Cype and EnergyPlus.

Porous NiMoO4 Nanosheet Films and a Device with Ultralarge Optical Modulation for Electrochromic Energy-Storage Applications.

Reducing building energy consumption, improving aesthetics, and improving occupant privacy as well as comfort by dynamically adjusting solar radiation are important application areas for electrochromic (EC) smart windows. However, the current transition metal oxides still cannot meet the requirements of neutral coloration and large optical modulation. We report NiMoO4 nanosheet films directly grown on fluorine-doped tin oxide glasses. The as-grown NiMoO4 film not only achieves neutral coloration from transparent to dark brown but also shows an ultralarge optical modulation (86.8% at 480 nm) and excellent cycling stability (99.4% retention of maximum optical modulation after 1500 cycles). Meanwhile, an EC device demonstrating good EC performance was constructed. These results will greatly promote the research and development of binary transition metal oxides for both EC and energy-storage applications, and NiMoO4 films may be an excellent candidate to replace NiO films as ion-storage layers in complementary EC devices with WO3 films as EC layers.

Experimental and numerical investigation on the charging and discharging process of a cold energy storage for space cooling of buildings

To address the current issue of the difficulty to use the hot outdoor environment during summer nights to provide coolness for phase change materials (PCM) and thus reduce building energy consumption in hot summer areas, a novel cold energy storage unit has been proposed. It replaces the hot outdoor environment with other free or cheap cold sources. An experimental setup is built to investigate the cold storage and release performance of the PCM storage unit. Later, the well-validated numerical model is conducted to further explore thermal performance of the PCM storage unit. The numerical result indicates that the cold storage process can be completed from 64.33 min to 96.56 min when the water inlet temperature varies from 10 °C to 16 °C. Further, during the cold release process, the PCM storage unit can reduce the temperature of the hot air by a maximum of about 8–12 °C when the air inlet temperature ranges from 32 °C to 38 °C. The cold release efficiency is varied between 81.65 % and 96.44 %. In conclusion, the findings provide a promising way for cold storage and space cooling of buildings in hot summer areas through the cold energy storage unit.

Analysis of the impact of energy consumption data visualization using augmented reality on energy consumption and indoor environment quality

This study proposes augmented reality (AR) as one of the methods to effectively reduce energy consumption in smart homes while maintaining an acceptable level of indoor environmental quality (IEQ). The experiment was conducted for a total of 90 min in an environment chamber where IEQ could be controlled, and participants were able to adjust the IEQ as desired throughout the duration of the experiment. Targeting a total of 21 participants, data on energy consumption, IEQ, and psychological response were collected under two conditions: (i) without providing energy consumption data through AR software, and (ii) with providing energy consumption data. The results show that AR software can positively impact energy consumption reduction. Also, reducing energy consumption through AR software did not significantly affect the psychological response to the subjects’ IEQ, suggesting that AR software can be used as an effective tool for reducing energy consumption without compromising occupant comfort concerning IEQ. In other words, when occupants are satisfied with indoor environments and are aware of their energy consumption, it means that energy consumption can be reduced for economic benefits. The results of this study suggest potential economic and social benefits from reducing building energy consumption.

Numerical study on heat transfer characteristics of spray cooling double skin façade

Using spray cooling technology to solve the overheating issue in double skin façade (DSF) is an important attempt to reduce building energy consumption. While, the thermal performance of the spray cooling double skin façade (SC-DSF) is not very clear, especially the complicated heat transfer characteristics. In this study, a comprehensive numerical model of SC-DSF system including solar radiation and two-phase flow problem is established by using three-dimensional steady Euler-Lagrange method to analyze the heat transfer characteristics from a microscopic perspective. And the CFD model is validated by the experiment. Meanwhile, a quantitative analysis is conducted to investigate the thermodynamic and kinetic behavior of the SC-DSF in hot humid climate region in China. The influences of outdoor air relative humidity, solar radiation intensity, and outdoor wind speed on the water spray cooling effect of the DSF are analyzed. The cooling efficiency of SC-DSF system is sensitive to the outdoor relative humidity. In a sufficiently cooled condition, the minimum temperature in the cavity is close to the outdoor wet-bulb temperature. The spray cooling efficiency reaches 28.2 % with the outdoor relative humidity of 20 %, but decreases to only 9.3 % as relative humidity rises to 80 %. Outdoor wind speed also has some impact on the spray cooling system, an optimal outdoor wind speed of 1.5 m/s can enhance cooling efficiency by 6.6 %, but it has adverse effect on the cooling efficiency when wind speed exceeds 3 m/s. However, in addition to increasing surface temperature of the DSF, solar radiation has little influence on the cooling performance. Excessive humidity exceeding 80 % and wind speed surpassing 3 m/s may render the spray system ineffective. Therefore, the effects of environmental conditions should be fully considered and utilized in the design and application of spray cooling systems.

Daylighting Glare and Design for Visual Comfort

Daylighting and glare simulation provide architecture students, professionals, and researchers with the knowledge and skillsets to design environments for visual comfort. Conducting simulations is essential for better human health and reducing building energy consumption. This paper evaluates the effectiveness of a mixed-methods approach to designing a glare-free environment in a hot-arid region. It examines daylighting and glare distributions in different scenarios with combinations of architectural daylighting devices, such as shading devices, light shelves, etc., using Rhino 7, DIVA, and ClimateStudio. The study concludes by recommending a practical simulation approach for evaluating glare. In this case study, using a customized shading device/light shelf combined with efficient skylights reduces glare to imperceptible and increases the daylit area by 20%.

Biomimetic Facades: Enhancing Energy Efficiency of Buildings through the Luban Capsule Approach

The effective use of sustainable renewable energy sources is emphasized heavily in the vision for Oman’s energy industry in 2040 as a crucial tactic in reaching the objective of net-zero buildings. This calls for immediate action to reduce greenhouse gas emissions, especially by improving the efficiency of building facades in metropolitan settings. Biomimicry is a potentially effective approach that utilizes natural phenomena as a source of inspiration to develop novel techniques that mimic diverse creatures, their behaviors, and ecosystems. The goal of this article is to investigate the use of biomimicry in building facades, with an emphasis on improving facade thermal performance in order to reduce energy consumption. It explores the development and application of the Luban capsule, an adaptive biomimetic element, as a workable way to improve buildings’ energy efficiency, especially in warm areas. The study emphasizes two key points: a theoretical review of biomimicry methodologies and a critical evaluation of specific case studies that are well-known for their application of adaptive facades designed to mitigate solar heat gain. The Luban capsule, which has Omani roots, was transformed into a biomimetic element by reinterpreting the five leaves, ten stamens, and five calyxes of the Luban flower to create capsule elements with matching number configurations (5, 10, 5). The Luban capsule was then applied to the service buildings on the campus of the Oman College of Management & Technology (OCMT), adjusting their facades in response to the sun’s position along two axes: behavioral aspects (which mimic the Luban flower’s opening and closing mechanism) and organic form (which incorporates the Luban flower’s natural shape) across facades with various elements, orientations, and functionalities. The study concludes with a framework that aims to minimize the need for artificial lighting, lessen dependency on air conditioning, and mitigate glare in diffused light. These projects play a crucial role in implementing sustainable building practices that are in line with Oman’s long-term energy sector vision by reducing building energy consumption and carbon emissions.

Economic Model Predictive Control in Buildings Based on Piecewise Linear Approximation of Predicted Mean Vote Index

Energy shortage is a challenge for many countries, and building energy consumption accounts for a considerable proportion of global energy consumption. The main work of this paper is to optimize the energy consumption of heating, ventilating, and air conditioning (HVAC) systems in buildings based on economic model predictive control (EMPC). The cost in EMPC design includes energy consumption and predicted mean vote (PMV), which is an index that evaluates the thermal comfort of indoor occupants. In order to model the nonlinearity of the PMV index, we propose a lattice piecewise linear (PWL) approximation, which has high approximation precision and facilitates the resulting optimization problem, which is basically a piecewise quadratic programming problem. For the piecewise quadratic programming, we propose a descent algorithm that converges quickly and scales well with the length of the prediction horizon in the EMPC problem. The experimental results demonstrate that the proposed method saves 19.78% of the electricity cost compared to the conventional control strategy and significantly increases indoor comfort. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> — The motivation of this article is to provide a control strategy to reduce building energy consumption and ensure indoor thermal comfort. In most of the existing methods for air conditioning temperature control, the occupants’ comfort hasn’t been considered. In this paper, thermal comfort is described by the PMV index, which is basically nonlinear. In order to model the thermal comfort more accurately, in this paper, the PMV index is approximated piecewise linearly in order to meet the requirements of accuracy and computational efficiency. The resulting optimization problem is not hard to solve, and we provide an efficient algorithm for solving this optimization problem. Preliminary simulation experiments demonstrate that this approach is practical, i.e., it achieves energy reduction and ensures thermal comfort. Our strategy, however, has not yet been deployed in real buildings. In future research, we will propose similar techniques for large-scale systems in order to solve energy optimization problems containing multiple thermal zones and realize the proposed technique in real buildings.

Fabrication of phase change microcapsules with polymer-metal hybrid shell and their utilization potentiality in gypsum composites for energy conservation

This study fabricated a kind of novel phase change microcapsules with a metal-polymer hybrid capsule shell for applying in gypsum materials to reduce building energy consumption. The microstructure, composition and thermal characteristics of the microcapsules were investigated by using techniques such as the scanning electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and differential scanning calorimetry. Their impact on the thermal regulation characteristics of gypsum composite materials was also analyzed through the heating plate test and simulated room experiment. Results show the microcapsules with inner organic polymer and outer copper layer were successfully fabricated. And they exhibited a phase change temperature between 22.3 ℃ and 23.3 ℃ and latent heat between 82.2 J/g to 139.5 J/g. Meanwhile, the thermal inertia and thermal storage capacity of gypsum composites were enhanced by incorporating the final microcapsules. After heated for 40 min, the gypsum composite board with MPCM-Cu shows the ability to reduce the room temperature fluctuation. Furthermore, the thermal performance of MPCM-Cu remains stable after 250 thermal cycles. These results indicate that final microcapsules exhibit the potential for building energy conservation.

All‐Solid‐State Transparent Variable Infrared Emissivity Devices for Multi‐Mode Smart Windows

AbstractSmart windows that incorporate photothermal modulators (PMs) can independently regulate solar transmittance and infrared (IR) emissivity to improve building comfort and reduce energy consumption. Herein, a novel all‐solid‐state variable IR emissivity device (VED) is first designed and fabricated with a high visible irradiation transmittance (T′vis = 0.79) and solar irradiation transmittance (T′sol = 0.75) using an ITO/SiO2/ITO Fabry–Perot cavity structure. The VED exhibits different IR emissivity (ɛ) values at positive (ɛP = 0.80) and negative (ɛN = 0.38) bias, allowing for dynamic regulation of radiation by controlling the electrical conductivity of the indium tin oxide (ITO) layer. Furthermore, an all‐solid‐state PM with a structure of ITO/SiO2/ITO/Glass/ITO/NiO/ZrO2/Li/WO3/ITO, which is capable of independently regulating solar transmittance (ΔT'sol = 0.31) and IR emissivity (Δɛ2.5–25 µm = 0.42), is fabricated. The multi‐mode smart window incorporating PMs can achieve “bright,” “dark,” “warm,” and “cool” modes, making them suitable for deployment in diverse climate zones. The innovative smart window holds a massive potential for use in reducing building energy consumption.

Combination optimization, importance order of parameters and aging consequence prediction for thermal insulation coating with radiation characteristics

Thermal insulation coating (TIC) is beneficial for reducing building energy consumption. In this work, a joint optimization and analysis approach for multi-parameters of TIC was proposed to determine its optimization trend, importance order of parameter and available parameter combinations. Its radiation characteristics and thermal resistance were comprehensively considered. Based on the approach, TIC was evaluated from energy saving rate of cooling (ESRcool), heating (ESRheat), and total energy consumption (ESRtotal) in two climates: hot summer cold winter (Shanghai), and hot summer warm winter (Guangzhou). Results indicated that constantly positive ESRcool was only achieved by optimizing solar absorptivity, while constantly positive ESRheat can be obtained by optimizing different parameters. To guarantee positive ESRtotal, thermal resistance should exceed 0.11 m2·K·W−1 or solar absorptivity should be between 0.2 and 0.6 in Shanghai, while solar absorptivity should be between 0.1 and 0.3 in Guangzhou. For these two cities, the most important parameter was thermal resistance or solar absorptivity. The optimal TIC for Shanghai was “high thermal resistance + low solar absorptivity + low emissivity”, while high emissivity was suitable for Guangzhou. By utilizing the approach and results, energy-saving effect of TIC can be optimized during material design, and influence of material aging can be predicted.

Multi-Objective Optimization Research on the Integration of Renewable Energy HVAC Systems Based on TRNSYS

Well-designed passive buildings can drastically reduce building energy consumption, and optimal design of air conditioning systems is the key to achieving low operating energy consumption in near-zero energy buildings. TRNSYS was used to build the simulation model for a near-zero-energy building and its air conditioning system in Beijing. The Taguchi method was used to sort the design parameters that affect system performance according to the degree of influence and find the best combination of design parameters to optimize the system, which increased the solar fraction of the system by 4.6% and reduced the annual operating energy consumption by 7.32%. For the optimized system, a multi-objective optimization function of the life cycle costs and carbon emissions was established. By comparing the energy consumption, life cycle costs, and carbon emissions of the air conditioning system under different system configurations, optimal configuration solutions under different design target weights were obtained. It was found that using a ground source heat pump system + solar collector system had better energy-savings benefits, but the operating costs were slightly higher. The application of absorption refrigeration can reduce the system operating costs but will increase the initial investment. The best economic benefits were achieved using the ground source heat pump system + solar collector system for heating in winter and the ground source heat pump system for cooling in summer, and the best environmental benefits were obtaining using the ground source heat pump system + solar collector system for heating in winter and the ground source heat pump system + solar absorption refrigeration system in summer, which provides a reference for the optimization design and research of air conditioning systems in near-zero energy buildings.

Investigation on alkali-activated insulation mortar containing high-volume recycled concrete powder for energy-efficient buildings

The influence of recycled concrete powder (RCP) on the thermal insulation of alkali-activated materials remains unclear. Hence, this study develops an innovative alkali-activated insulation mortar, serving RCP and blast furnace slag as the precursor and expanded polystyrene (EPS) beads as fine aggregate, together with air entrainer. Experimental results show that the mortar had satisfactory workability owing to the RCP substitution, supported by appearance and infrared thermal imaging tests. As the ratio increased, the density, compressive strength, and thermal conductivity of the mortar decreased, due to the increasing volume of porous paste and internal air voids. Subsequently, the material design of the mortar was optimized through the adjusted Box-Behnken design. The obtained mortar achieved a high-volume use (61.7 wt%) of RCP, and exhibited an extremely low conductivity (∼0.030 W/(m∙K)) among novel lightweight building materials. Energy simulation further indicates that the optimized mortar can surpass traditional insulation materials, including EPS, polyurethane, and rock wool panels, in reducing air conditioning energy consumption across all seasons and climate zones. This was particularly evident in colder cities such as Harbin and Lhasa. Given that increasing the thermal resistance of the envelope can effectively reduce building energy consumption, the development of such sustainable alkali-activated insulation mortar would undoubtedly contribute to the implementation of energy-efficient buildings.

Multisource solid waste development of low-carbon ultra-light foamed insulation materials: A feasibility study

The continuous increase in building energy consumption, and the increasing types and quantities of solid waste have seriously hindered the rapid development of social economy. Therefore, reducing building energy consumption while realizing the recycling of waste has become the mainstream topic of environmental protection construction in the new era. An alkali-activated ultra-light foamed insulation material (AFIM) for building walls was prepared using EPS particles as lightweight aggregates. The effects of EPS dosage, particle size, and gradation on the compressive strength, dry density, thermal conductivity, and volumetric water absorption of AFIM were studied. The results showed that while ensuring good mechanical properties of AFIM, EPS particles can significantly reduce the dry density, thermal conductivity, and volumetric water absorption of AFIM. Excitingly, the optimal thermal conductivity and dry density of AFIM were 0.0408 W/(m·K) and 127.03 kg/m3, respectively. The microscopic morphology results showed that there was good compatibility between EPS particles and AFIM slurry, and the interface transition zone (ITZ) between them was dense and without obvious cracks. In addition, the feasibility of AFIM was evaluated from four aspects: performance, energy consumption, carbon emissions, and life cycle cost (LCC). It was encouraged that the performance of AFIM was comparable to that of traditional insulation materials, and showed significant advantages in energy conservation, emission reduction and economic benefits compared to traditional insulatin materials.

Experimental and numerical study of adaptive ventilation and sunlight regulation building envelope combining variable transparency shape-stabilized phase change material

The development of adaptive building envelopes with advanced PCM to reduce building energy consumption is a promising topic. This study proposed an adaptive ventilation and sunlight regulation wall (AVSRW) by combining the variable transparency shape-stabilized PCM (VTSS-PCM), reflective film, and ventilation cavity. The combination of VTSS-PCM and reflective film could passively regulate the solar absorptivity (SA) of AVSRW. The ventilation cavity with airflow control enhanced the heat storage and release efficiency of VTSS-PCM. A dynamic photo-thermal coupling model of the AVSRW was presented and validated by a full-scale experiment in summer and winter conditions. Then, based on the weather data of the typical meteorological year of Changsha, China, the performances of AVSRW on days, months, and a year were evaluated. The impact of three influential factors and their combined effects on the performance of AVSRW were analyzed. Ultimately, a global optimization was conducted to improve the performance of AVSRW, and compared with the massive wall. The results showed that the AVSRW passively decreased its SA on summer days and increased its SA on winter days. The total annual undesired heat exchange (TAHE) of AVSRW first decreased and then increased with the increase of melting temperature (Tm) and thickness (L) of VTSS-PCM. The reflective film had an opposite effect on the annual heat gain (AHG) and annual heat loss (AHL) of AVSRW, resulting in the TAHE remaining unchanged with the increase of reflectivity (R) of the reflective film. The greater the L, the smaller effect of the Tm and R on the AHG and AHL, and the greater the R, the greater effect of the Tm and L on the AHG and AHL. After optimization, the values of the Tm, L, and R corresponding to the optimal solution were 24.60 °C, 0.17 m, and 0.63, respectively. Compared with the reference wall, the AVSRW with the best performance had lower AHG and AHL, and the annual energy-saving rate of the AVSRW reached 43.49%. This study guides the application and parameter optimization of AVSRW in hot summer and cold winter regions.

Daylight performance of horizontal light pipe and shading systems in office room with bilateral opening

Daylighting implementation in the building can reduce building energy use. Previous research about Horizontal Light Pipe and shading systems in the Tropics examined daylighting strategies in a room with a unilateral opening, which receives daylight through a window in one wall. The bilateral openings from two adjacent side windows have the potential to improve daylight distribution and have yet to be discussed in previous research. This research evaluates the daylight level and distribution of HLP and shading systems in a room with a bilateral opening from two adjacent windows. The research method is experimental with simulation using IES-VE (Integrated Environment Solution-Virtual Environment) as a tool. The Daylight Factor (DF) and Uniformity Daylight Factor (UDF) of a room with bilateral openings from two adjacent windows were compared with a room with bilateral openings, HLP, and shading systems. The results indicate that integrating HLP and shading systems in an office room with two adjacent side windows decreases the average Daylight Factor (DF) by 48.74%, bringing the average DF fulfilling the recommended DF level for the office room. HLP and shading systems improve the Uniformity Daylight Factor and percentage of sensor points with DF 2-5%, as high as 56% and 67.38%, sequentially.