Energy-saving Efficiency Research Articles

Selecting suitable passive design strategies for residential high-rise buildings in tropical climates to minimize building energy demand

Passive design strategies (PDS) are a fitting solution to reduce the ever-growing energy cost of residential high-rise buildings in tropical regions. However, PDSs’ building energy saving potential significantly varies with local climate conditions, but it has been sparsely investigated. Hence, this study investigated the energy-saving efficiency of eight common PDSs integrated into a typical residential high-rise building in three sub-climates: extremely hot humid (0A), very hot humid (1A), and warm humid (3A) defined by ASHRAE for the tropical climate. This study developed a Building Performance Analysis (BPA) workflow with a BIM-based simulation framework and local and global sensitivity analyses for the building energy analysis. The global sensitivity analysis revealed that low e-coating on glasses is the most influential PDS for 0A and 1A climates, but it has a negative effect in the sub-climate zone 3A. The low-conducting exterior walls are the most effective PDS in the sub-climate zone 3A, but they are poorly performed in the other two sub-climate zones. Based on the energy calculation and sensitivity analysis, this study proposes the best PDS groups, saving up to 40.1%, 63.5%, and 31.7% of average annual building consumption in the sub-climate zones, 0A, 1A, and 3A climates.

Pilot-scale capacitive deionization for water softening: Performance, energy consumption, and ion selectivity

Capacitive deionization (CDI) has emerged as an efficient process for hardness control than traditional water-softening technologies. However, few systematic studies have been conducted on water softening using pilot-scale CDI systems. For industrial applications, it is essential to investigate deionization performance, energy consumption, and selectivity for divalent cations through pilot-scale studies. In this study, we examined the deionization performance and energy consumption of a pilot-scale CDI process for effective water softening. The key operational variables analyzed were the applied voltage (200–300 V (i.e., 1.0–1.5 V per pair)), feed concentration (550–1250 mg/L), recovery ratio (50–80 %), flow rate (3–5 L/min), and adsorption/desorption time (80–180 s). Within this range, a high voltage, low feed concentration, low recovery ratio, high flow rate, and long adsorption/desorption times are advantageous for the total dissolved solids (TDS) removal ratio. In terms of energy efficiency, expressed as TDS removal per unit energy consumption, a low voltage, low feed concentration, low recovery ratio, fast flow rate, and long adsorption/desorption time are beneficial. Additionally, we investigated the selective removal of Ca2+ over Na+ under various operating conditions, as well as its impact on enhancing energy efficiency. The pilot CDI system achieved a Ca/Na selectivity coefficient of approximately 2.4 and it was analyzed to achieve up to 45 % energy-saving efficiency compared to nonselective systems (i.e., selectivity coefficient = 1). The results of this study are expected to provide valuable data for the application of CDI to water softening and hardness control processes.

Thermophysical properties and energy-saving efficiency of phase change microcapsule foamed cement composite insulation materials

The addition of phase change materials (PCMs) to building envelopes can improve building thermal stability and reduce energy consumption. In this study, phase change paraffin microcapsules are combined with foamed cement to create composite thermal insulation materials with varying mass ratios of microcapsules. A heat transfer characterization experimental platform was established to investigate the heat transfer laws. The incorporation of phase change microcapsules (MPCMs) into foamed cement resulted in a reduction in thermal conductivity. The thermal conductivity of the test blocks exhibited a linear relationship with the mass ratio of MPCMs, with an average thermal conductivity of 0.053 W/(m-K) observed for 20 % MPCMs. The impact of foamed cement containing MPCMs on building energy consumption was analyzed in five different climate zones in China using EnergyPlus. The results show that energy savings are more significant in cities with higher heating demand. In non-cold regions, energy savings are highest when the phase change temperature is close to the local annual average temperature. The optimal energy saving program is evaluated by energy consumption simulation. The results show that it achieves the highest energy savings in Harbin, which saves a total of 1074,007 kWh. Additionally, it has the highest energy saving rate in Beijing, with a rate of 14.66 %.

Room-temperature flexible phase change material with high emissivity and high enthalpy for building energy saving

Summer heatwave events become more and more frequent, building cooling load continues to rise, and the traditional cooling method using air conditioning consumes a lot of energy. New technologies and materials with high efficiency, energy saving and low cost are urgently needed to solve the problem of high energy consumption in buildings. In this paper, by combining phase change storage technology with passive cooling technology of sky radiation, a new type of high-emission flexible composite phase change material (CPCM) was prepared using polypropylene hollow fiber (PP hollow fiber), Styrene-Ethylene-Butylene-Styrene (SEBS) and paraffin wax (PA). The prepared CPCM with excellent thermophysical properties, including a latent heat of 175.19 J/g, room temperature flexibility, the contact angle of the hydrophobic test of 129.15°, and the infrared emissivity of the atmospheric window of 0.942. The cooling experiment results show that the maximum temperature difference between CPCM and the environment is 2.6 °C lower than the ambient temperature. In addition, the simulation results show that the external surface temperature of the CPCM roof can be reduced by 23.15 K at the highest compared with a common roof, and the maximum energy saving can reach 13.24 W/m2. Compared with the high emissivity roof without CPCM, the external surface temperature is further reduced by 0.47K, the delay time is 50min, and the maximum energy saving can reach 0.76 W/m2. It's worth getting excited that CPCM can delay the opening time of air conditioning for 10 days. In addition, the application efficiency of cities in typical climate regions is simulated, and outstanding energy-saving efficiency is obtained, among which the maximum saving energy in Guangzhou is as high as 20.16 W/m2. The successful preparation of the novel CPCM material provides a new direction for the development of radiation-cooling technology.

Research on Energy-Saving Efficiency and Influencing Factors of Green and Low-Carbon Enterprises Based on Three-Stage DEA and Tobit Models

Implementing the “dual-carbon” objective has profoundly affected China’s businesses, prompting a continuous process of transformation and innovation. Green, low-carbon transformation, upgrading, and sustainable development have emerged as the means to achieve high-quality company growth, with firms playing a crucial role in achieving the “dual-carbon” target. By prioritizing firms’ green, low-carbon, and sustainable growth, not only can their economic efficiency be improved, but it also serves as a vital measure to advance high-quality development. To achieve this objective, it is crucial to analyze the elements that impact the energy-saving effectiveness of businesses to develop optimization tactics that can enhance their competitiveness. This study combines the three-stage Data Envelopment Analysis (DEA) and the Tobit model to assess the energy-saving efficiency of green and low-carbon firms from 2018 to 2022. The analysis focuses on selected samples from various areas and industries. The study investigates the relationship between energy-saving effectiveness and different regional and industrial parameters, considering the distinct attributes of each firm and the key elements that influence its energy-saving performance. The findings indicate that green, low-carbon firms typically demonstrate suboptimal energy-saving efficiency but have considerable room for improvement. Upon considering environmental concerns, it becomes clear that the primary limitation on energy-saving performance is the lower efficiency of the enterprise scale. The energy-saving efficiency of green, low-carbon firms varies significantly across different regions and industries. On average, northern firms in the energy-saving and carbon reduction industry, as well as the resource recycling industry, have higher energy-saving efficiency compared to southern enterprises. In contrast, the environmental protection industry in southern firms demonstrates a better average energy-saving efficiency compared to their northern counterparts. Employee quality, policy support, and automation are key factors that greatly enhance the energy-saving efficiency of firms in both regions. Enterprise size has a beneficial impact on the energy-saving efficiency of southern firms but a negative impact on northern enterprises. Moreover, the industry and financial structures exert a detrimental influence on enhancing the energy-saving efficiency of green and low-carbon firms. Thus, in order to improve the energy-saving effectiveness of businesses, it is essential to utilize the elements that have a positive influence on energy-saving performance and reduce the impact of those that have negative impacts. This strategy will enhance the energy-saving efficiency of businesses and promote the development of an environmentally friendly and low-carbon society.

Energy-saving and economic analysis of the data center cooling system using magnetic bearing chillers under different climate conditions

Magnetic bearing chiller has excellent Coefficient of Performance, but the high initial investment makes it challenging to find a balance between energy-saving efficiency and economic potential. This paper proposes two energy-saving retrofits with water-side economizers, using efficient centrifugal chillers (Plan 1) and magnetic bearing chillers (Plan 2), respectively, to replace the existing cooling system of a case data center in Nanchang. Energy models of three cooling systems are developed to analyze the energy efficiency and performance. Compared to the existing cooling system, the operation time of Full free cooling and Partial free cooling for Plan 1 and Plan 2 reach 2489 and 1324 h, respectively. Result in energy savings of 63.19 % and 64.54 %, and power usage effectiveness reduce 0.341 and 0.349, respectively. Because the annual chiller COP of Plan 2 is 6.7 % higher than that of Plan 2, Plan 2 saves additional 3.96 % annual energy consumption compared to Plan 1. Furthermore, the energy-savings and economy of the retrofit plans in five typical climate cities in China are discussed. The energy savings rates for Plan 1 and Plan 2 are 61.4%–64.7 % and 62.1%–65.6 %, respectively, and their dynamic payback periods are 2.02–5.15 years and 2.16–5.6 years.

Photothermal synergistic modulation of patterned VO2-Based composite films for smart windows

Vanadium dioxide (VO2) emerges as promising material for smart windows due to its ability to dynamically modulate the characteristics of near-infrared light during phase transition, accompanied by a relatively high luminous transmittance (Tlum). However, traditional VO2-based smart windows have predominantly emphasized achieving high solar modulation ability (ΔTsol), often overlooking the modulation of emissivity (ε) of long-wave infrared (LWIR). This oversight makes it challenging to achieve optimal energy-saving effects. To address this, patterned smart window composite films are designed and optimized by using Fabry-Pérot cavity to achieve dual-band coordinated regulation of sunlight and thermal radiation, which can greatly improve the energy-saving efficiency. The obtained composite film has a great low-temperature luminous transmittance (Tlum-L=50.4 %) and a high solar modulation ability (ΔTsol = 13.9 %). Meanwhile, the composite film can adaptively adjust its emissivity, with emissivity values of 0.67 and 0.18 at high and low temperatures, respectively, endowing it with excellent thermal radiation regulation capabilities. The development of patterned composite films is of great significance in the field of thermal control smart windows, which has great potential in improving the energy efficiency of buildings and enhancing resident comfort.

Study on multi-band spectral regulation performance of single-layer thermochromic coatings based on VO2 core-shell particles for building energy conservation

The spectral regulation performance of smart windows significantly impacts building energy consumption. Compared to thermochromic coatings that modulate only the sunlight band, those capable of multi-band modulation-including both sunlight and mid-to-far infrared bands-have the potential to further reduce energy consumption in buildings. The thermochromic coating based on multi-layer structures with multi-band modulation ability reported so far is unsuitable for practical application due to its complex preparation process and high cost. This study proposed a single-layer smart window coating utilizing core@VO2 particles to achieve multi-band modulation. This single-layer coating offers the advantages of simple preparation and convenient construction. We investigated the influence of parameters such as the shell-to-core ratio, particle volume fraction, and refractive index of the substrate on the spectral radiative properties using the FDTD method. Additionally, the impacts of variations in these parameters on energy consumption and carbon dioxide emissions were analyzed using EnergyPlus. The simulation results indicated that the core@VO2 nanoparticle coating possessed a maximum solar modulation ability of 27.6%, luminous transmittance of 48.15%, and maximum emissivity modulation ability of 16.7%. Compared with traditional low-e coatings, the maximum energy-saving efficiency increased by 7.36%. This study provides valuable insights for enhancing the energy efficiency of thermochromic smart window coatings.

Maximizing the Average Environmental Benefit of a Fleet of Drones under a Periodic Schedule of Tasks

Unmanned aerial vehicles (UAVs, drones) are not just a technological achievement based on modern ideas of artificial intelligence; they also provide a sustainable solution for green technologies in logistics, transport, and material handling. In particular, using battery-powered UAVs to transport products can significantly decrease energy and fuel expenses, reduce environmental pollution, and improve the efficiency of clean technologies through improved energy-saving efficiency. We consider the problem of maximizing the average environmental benefit of a fleet of drones given a periodic schedule of tasks performed by the fleet of vehicles. To solve the problem efficiently, we formulate it as an optimization problem on an infinite periodic graph and reduce it to a special type of parametric assignment problem. We exactly solve the problem under consideration in O(n3) time, where n is the number of flights performed by UAVs.

Operation strategy optimization and heat transfer characteristic analysis of photovoltaic/thermal module series connected with flat plate solar collector: System experimental study

Flat plate solar collector (FPSC) produces only thermal energy without electricity, whereas the photovoltaic thermal (PV/T) module produces electricity and low-temperature thermal energy. This paper presents a low-cost method to strengthen the functional uniqueness of individual PV/T and FPSC components through connecting a PV/T module in series with the other component. Under various water volume conditions, an experimental test on high mass flow rate was carried out. Results showed that the FPSC produced a better heating contribution and that reverse heat transfer of the PV/T module might be reduced by changing the operation strategy. The water volume is a crucial factor that influences the system's available heating time, a system that operates in the optimal water volume range will produce greater energy savings. Furthermore, the maximum values of the thermal, electrical, exergy, and primary energy-saving efficiency were 51.91 %, 13.52 %, 19.13 %, and 87.20 %, respectively. The optimal water volume distribution range of the system is 160–180 L. With an average annual decrease of 2.96 t in CO2 emissions, the system provides a 4.28-year payback period and saves 5285.71 USD in electricity costs throughout its life cycle. The novel system performs extremely well in terms of energy and cost efficiency.

A Smart Window with Passive Radiative Cooling and Switchable Near-Infrared Light Transmittance via Molecular Engineering.

Smart windows with synergetic light modulation have heightened demands for applications in smart cars and novel buildings. However, improving the on-demand energy-saving efficiency is quite challenging due to the difficulty of modulating sunlight with a broad bandwidth in an energy-saving way. Herein, a smart window with switchable near-infrared light transmittance and passive radiative cooling is prepared via a monomer design strategy and photoinduced polymerization. The effects of hydrogen bonds and fluorine groups in acrylate monomers on the electro-optical properties as well as microstructures of polymer-dispersed liquid crystal films have been systematically studied. Some films show a high contrast ratio of 90.4 or a low threshold voltage (Vth) of 2.0 V, which can be roll-to-roll processed in a large area. Besides, the film has a superior indoor temperature regulation ability due to its passive radiative cooling and controllable near-infrared light transmittance properties. Its radiative cooling efficiency is calculated to be 142.69 W/m2 and NIR transmittance could be switched to below 10%. The introduction of a carboxylic monomer and fluorinated monomer into the system endows the film with a highly efficient temperature management capability. The film has great potential for applications in fields such as flexible smart windows, camouflage materials, and so on.

How Do Developers Influence the Transaction Costs of China’s Prefabricated Housing Development Process? An Investigation through the Bayesian Belief Network Approach

The implementation of prefabricated housing (PH) has become prevalent in China recently due to its advantages in enhancing production and energy-saving efficiency within the construction system. However, stakeholders may not always fully realize the benefits of adopting PH due to the emergence of transaction costs (TCs) in the development process of such projects. This study investigated the strategies for developers to make rational choices for minimizing the TCs of the PH project considering their own attributes and external constraints. A Bayesian Belief Network model was applied as the analytical method, based on surveys conducted in China. A single sensitivity analysis indicated that developers influence the TCs of PH through the following three most impactful factors: prefabrication rate, PH experience, and contract payment method. Integrated strategies are recommended for developers in various situations based on a multiple sensitivity analysis. Developers facing challenges due to high prefabrication rates are advised to reduce the risks by procuring highly qualified general contractors and adopting unit-price contracts. For developers with limited PH experience, adopting the Engineering–Procurement–Construction procurement method is the most efficient way to reduce their TCs in the context of China’s PH market. This study contributes to the current body of knowledge concerning the effect of traders’ attributes and choices on TCs, expanding the application of TC theory and fulfilling the study on the determinants of TCs in construction management.

Research on Boiler Energy Saving Technology Based on Internet of Things Data

This paper proposes a heat demand prediction model that analyzes the heat behavior of heat users, and analyzes the heat behavior data of heat users through a clustering algorithm to predict their heat demand. This paper is based on the supply-demand balance strategy to reduce the heat loss during the transmission of heat medium, and then improve the energy-saving efficiency of the boiler. The traditional boiler energy-saving and consumption reduction method is to optimize the boiler combustion parameters, improve the fuel combustion efficiency and waste heat recovery technology through the Internet of Things and big data technology. The method of balancing the heat-using end with the load of the boiler at low usage frequency is seldom considered. Therefore, this paper predicts the heat demand of the heat-using end by analyzing its thermal behavior, and balances the heat demand and boiler heat supply under the condition of meeting the heat demand. Finally, through simulation experiments, the validity of the model is verified, and the trend and data can be well predicted in the short-term heat demand prediction.

Zonal demand-controlled ventilation strategy to minimize infection probability and energy consumption: A coordinated control based on occupant detection

Due to the outbreak of COVID-19, an increased risk of airborne transmission has been experienced in buildings, particularly in confined public places. The need for ventilation as a means of infection prevention has become more pronounced given that some basic precautions (like wearing masks) are no longer mandatory. However, ventilating the space as a whole (e.g., using a unified ventilation rate) may lead to situations where there is either insufficient or excessive ventilation in localized areas, potentially resulting in localized virus accumulation or large energy consumption. It is of urgent need to investigate real-time control of ventilation systems based on local demands of the occupants to strike a balance between infection risk and energy saving. In this work, a zonal demand-controlled ventilation (ZDCV) strategy was proposed to optimize the ventilation rates in sub-zones. A camera-based occupant detection method was developed to detect occupants (with eight possible locations in sub-zones denoted as ‘A’ to ‘H’). Linear ventilation model (LVM), dimension reduction, and artificial neural network (ANN) were integrated for rapid prediction of pollutant concentrations in sub-zones with the identified occupants and ventilation rates as inputs. Coordinated ventilation effects between sub-zones were optimized to improve infection prevention and energy savings. Results showed that rapid prediction models achieved an average prediction error of 6 ppm for CO2 concentration fields compared with the simulation under different occupant scenarios (i.e., occupant locations at ABH, ABCFH, and ABCDEFH). ZDCV largely reduced the infection risk to 2.8% while improved energy-saving efficiency by 34% compared with the system using constant ventilation rate. This work can contribute to the development of building environmental control systems in terms of pollutant removal, infection prevention, and energy sustainability.

Enhancing the Grinding Efficiency of a Magnetite Second-Stage Mill through Ceramic Ball Optimization: From Laboratory to Industrial Applications

Ceramic ball milling has demonstrated remarkable energy-saving efficiency in industrial applications. However, there is a pressing need to enhance the grinding efficiency for coarse particles. This paper introduces a novel method of combining media primarily using ceramic balls supplemented with an appropriate proportion of steel balls. Three grinding media approaches, including the utilization of steel balls, ceramic balls, and a hybrid combination, were investigated. Through an analysis of the grinding kinetics and the R–R particle size characteristic formulas, the study compares the breakage rate and particle size distribution changes for the three setups. The results indicate that employing binary media effectively improves the grinding efficiency for +0.3 mm coarse particles while maintaining the energy-saving advantages of ceramic ball milling. Simultaneously, the uniformity of the ground product is ensured. This proposed approach has been successfully validated in industrial applications, providing robust theoretical support for the expansion of ceramic ball milling applications.

Expanded titanium-bearing blast furnace slag phase change aggregate: Preparation, performance and phase change energy storage mortar application

Expanded titanium-bearing blast furnace slag (ETS), containing rich connected pores, largely accumulated, due to low hydration activity and particle strength. In this study, the pore system of ETS was fully utilized to load paraffin for fabrication of phase change aggregate (PCA), and then the PCA was used to prepare phase change energy storage mortar (PCEM) and mechanical properties, thermal performances and energy-saving efficiency were subsequently evaluated. The results indicated that the 28-day and 56-day compressive strength of mortar containing 100 % PCA reached to 7.8 MPa and 8.6 MPa. The energy saving efficiency of building reached to 8.1 %, the peak indoor temperature of building decreased by 1.2 °C and 2.3 °C in spring and summer, respectively. These facts give confidence of ETS consumption in building energy-saving materials.

Transmittance optimization of tunnel shading shed for maximum energy savings and traffic safety: When replacing tunnel lighting in threshold zone

Tunnel shading shed instead of tunnel lighting is one of the ideal ways to reduce the tremendous energy consumption at the entrance (section 2.1), but at present the length of tunnel shading shed and illuminance inside tunnel shading shed rarely meet the relevant technical requirements (section 2.2). Although some literature estimated the energy saving benefits of tunnel shading shed when replacing tunnel lighting in the threshold zone (section 2.2.1), there is no study on the conditions for maximum energy saving, the impact of energy saving on safety and the energy-saving efficiency in all time and all weather. To solve the above problems, suggest a multi-objective optimization condition of transmittance for maximizing energy savings improving traffic safety (section 3.3.2). In addition, propose an efficient sunlight simulation method based on finite element partitioning (section 3.3.1), derive a formula for precise energy-saving efficiency of tunnel shading shed (section 4.2.1), and analyze factors affecting energy-saving efficiency. The results show that: Suitable transmittance can simultaneously maximize the energy savings of tunnel shading shed (section 4.2.2) and improve traffic safety in the tunnel portal area (section 4.3). And the energy-saving efficiency on sunny summer days is not the greatest. It provides the theoretical and methodological support for making full use of sunlight and saving tunnel lighting electric energy.

Effect of hydrogen-enriched natural gas on flue gas waste heat recovery potential and condensing heat exchanger performance

Hydrogen-enriched natural gas (HENG) is one of the significant ways to store, transport, and utilize hydrogen energy. This paper presents the characteristics of HENG and flue gas, energy saving, carbon reduction, and condensate recovery potential of flue gas waste heat. Based on the theoretical and experimental study of the existing flue gas condensing heat exchanger (FGCHE) added at the rail of gas-fired boiler, the performance of the FGCHE under different hydrogen blending ratios is studied. The results show that augmenting the hydrogen blending ratio decreases the volume heating value of HENG, and CO2 content of flue gas. Meanwhile, the mass heating value of the HENG, the water vapor content, and dew point temperature of flue gas increase as the hydrogen blending ratio increases. The flue gas waste heat recovery utilization ratio and energy-saving efficiency of the FGCHE can be promoted. Moreover, the heat transfer capacity of the FGCHE using HENG is enhanced, while the flue gas flow pressure drop is reduced. Compared with the FGCHE used in pure natural gas systems, the all-hydrogen system increases the flue gas waste heat recovery amount by 62.4–120.4 %, reduces the flue gas flow pressure drop by 33.9 %, and reduces the carbon emission by 100 %.

Hierarchical Operation Optimization for Regenerative Braking Energy Utilizing in Urban Rail Traction Power Supply System

The energy feedback system (EFS) is widely accepted to utilize the regenerative braking energy (RBE) in an urban rail traction power supply system (TPSS). However, the sharing relationship of RBE between EFS, traction trains and on-board braking resistors is not clear. In addition, the impact of EFS operation on the sharing of RBE has been rarely studied. This paper proposed a hierarchical operation optimization method for improving the utilization of shared RBE in TPSS through the EFS. An optimizing model for the dynamic start-up voltage threshold of EFS is established, with the objective of minimizing TPSS power consumption. A fast prediction model of train operation information is developed to analyze the steady-state power flow in advance. The optimal solution is searched using a salp swarm algorithm (SSA) on a per second basis. A microsystem of three traction stations and two trains is analyzed. Compared to the conventional constant voltage operation scheme, the optimal solution achieves a maximum additional energy-saving efficiency improvement of 2.44%. Efficient sharing of RBE is identified as the key to achieving energy savings. Regarding the local control part, system stability analysis is verified. Real-time simulation results indicate that the dynamic operating mode of EFS efficiently distributes RBE.

Shading effect and energy-saving potential of rooftop photovoltaic on the top-floor room

Rooftop photovoltaic panels can serve as external shading devices on buildings, effectively reducing indoor heat gain caused by sunlight. This paper uses a numerical model to analyze rooftop photovoltaic panels' thermal conduction, convection, and radiation in hot summer areas as shading devices. The researcher builds an experimental platform to verify the model, exploring the potential for energy savings of photovoltaic rooftop units in the Wuhan area. The results show that after installing photovoltaic panels, the delay performance of the roof increases by 0.5 h, the roof heat flux is reduced by 41.7%, the peak temperature of the roof is reduced by 22.9 °C, and the daily heat gain is reduced by 74.84%. Finally, this paper discusses the impact of high-reflectance and low-reflectance roofs on the shading effect. The study finds that low-reflectance roofs are more energy-efficient in the hot summer, as high-reflectance roofs lead to a 10.8% increase in indoor heat gain when the photovoltaic panel is installed. Finally, a quantitative method for evaluating the comprehensive potential for energy savings is proposed, considering the electricity generation gain of photovoltaic panels and the comprehensive energy-saving efficiency of photovoltaic roofs, which generates a total potential for energy savings rate of 61.06%. The model presented in this paper provides theoretical guidance for analyzing the comprehensive energy-saving effects of photovoltaic rooftop systems and reveals the potential for energy savings of rooftop photovoltaic panels as external shading devices.