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Highlights • The first city-level building energy efficiency benchmarking system for China. • A model considering the influence of operation parameters on energy consumption. • A systematic methodology of building energy benchmarking is proposed. • The model is a valuable analysis support tool for building energy managers. Abstract The city-level public building energy efficiency benchmarking system has an important guiding value for building energy-saving work, especially for Beijing, with its high energy-consumption density and both long heating and air-conditioning periods. This paper analyzed the characteristics of large-scale office buildings in Beijing and gives a detailed description of the process of establishing a public building energy efficiency benchmarking system for large-scale office buildings in Beijing, China, including data investigation and verification, Energy Usage Intensity(EUI) calculation, determining independent and dependent variables, developing and testing the benchmarking model, and deriving the benchmarking rating table. Then the first city-level public office building energy efficiency benchmarking system in China is established based on 88 large-scale office buildings in Beijing. The results showed that the model's performance index R2 is 0.667 and gives a good representation. The process has a strong potential for replication for other cities in China and even for a national energy-consumption evaluation system. [ABSTRACT FROM AUTHOR]

• The data requirements of quota methods are summarized, and a city-scale database containing 670 credible government office buildings is established. • By comparing the processes, the results and applicability, the selection basis of quota methods under different conditions is refined. • A flow chart of the formulation process and method selection of city-level building energy consumption quotas is constructed. • It is proposed that special attention should be paid to the outliers, and the characteristics of outliers in Chongqing are summarized. Energy consumption quota policies are effective management measures to promote energy conservation and emission reduction in China. Cities need to choose an appropriate method to formulate local energy consumption quota standards. This paper is based on the data of 670 government office buildings in Chongqing and the selected quantile method (QM), quota-level method (QLM) and multiple linear regression (MLR) method, which are widely used in the formulation of city-level energy quotas. By comparing their interpretability, evaluation, consistency and stability, the application conditions and applicability of each method are summarized. MLR has the strongest explanatory power but the highest requirements for the technology and information dimensions. The QLM is more explanatory and stable than the QM and is more suitable for the initial stage of energy quota management. When using the QLM, we should consider scientific classifications and reasonable quota levels. Special attention should be given to "outliers" with abnormal evaluations of the quota results. The outliers in Chongqing are characterized as buildings that have been used for more than 10 years and have an area of less than 5000 m2. Finally, this paper constructed a flow chart of the formulation process and method selection to help policymakers better understand how to choose the most appropriate method and identify inefficient buildings. [ABSTRACT FROM AUTHOR]

Abstract: It is not feasible to apply the traditional prediction method to predict hourly building cooling load at the urban energy planning stage because of the limited building information and complexity of energy prediction. This paper presents a simplified prediction model: Hourly Cooling Load Factor Method (HCLFM) that can provide quick and fair estimate of building cooling load for large-scale urban energy planning. The paper introduces the assumptions and principles of the proposed method, as well as discussing the implication and limitation of the approach. As a verification and demonstration, the method is applied to an office building in Beijing. The predicted results show that the dynamical trend of the cooling load is reasonable. The study further analyzes the potential causes of prediction errors and the significance of various cooling load influence factors. [Copyright &y& Elsevier]

The large public building energy consumption (BEC) is the focus of Building Energy Saving, therefore, it is necessary to study the characteristics of BEC to find out the important factors affecting BEC. For this purpose, 27 office buildings in the west of Inner Mongolia Autonomous Region were studied, based on statistical analysis of the researched basic information and energy consumption bill of these buildings. This paper focused on the determination of the significant factors affecting the total and subentry energy consumption intensity (ECI) of office building, as well as the establishment of standardized linear regression models between these selected factors and total and subentry ECI. Firstly, eleven continuous variables, three independent categorical variables, and the climate factor were selected and analyzed the impact on total and subentry ECI by statistical software SPSS20.0, in order to find out the significant influencing factors. Then based on the results of curve fitting, standardized models of total and subentry ECI and their respective significant impact factors were established using multiple linear regression analysis. The regression results showed that the electricity use percentage of the total equivalent electricity consumption was an important factor affecting the total ECI of office building in the west of Inner Mongolia Autonomous Region. Finally, univariate analysis of variance (ANOVA) was conducted between the three independent categorical variables and the total and subentry ECI, and the results showed that these factors had no significant effect on the ECI of office building. Process of the regressive model establishment and the results of analysis of variance could both guide us to propose more targeted energy saving measures. [ABSTRACT FROM AUTHOR]

• A novel three-stage decision-making approach for office buildings design considering 'Energy','Comfort', and 'Cost'. • The establishment of an optimization and decision-making model by applying NSGA-II and TOPSIS methods. • Two-year monitored data and post-occupancy evaluation for energy audit and thermal comfort. • The evidence of a case study demonstrates the feasibility of the proposed method and solutions. China, with the largest energy consumption system in the world, faces numerous challenges in achieving the government's commitment to reach a carbon-peak and carbon–neutral target. As the most common public building type in terms of floor area, office buildings have great potential for energy saving and emissions reduction. To meet this target, building designers target passive solutions that can meet the thermal comfort needs of occupants and also reduce energy consumption. This study aims to develop a decision-making method to select optimal solutions from among tens of thousands of design options considering the factors of energy consumption, comfort, and cost. We developed a novel optimization decision approach with the above-mentioned three objectives. The model consists of three stages: 1) the establishment of the reference building model, 2) sensitivity analysis to identify the main influencing variables and 3) the establishment of the optimization and decision-making model by applying NSGA-II and TOPSIS methods. By applying this three-stage decision-making model, this paper first proposes cost-effective passive design solutions for office buildings throughout the Hot Summer and Cold Winter climate zone. Finally, an office building in Shanghai was chosen as a case study to demonstrate the practical implementation of the proposed solutions through a post-occupancy evaluation with a two-year energy auditing and thermal comfort survey. It is evident that the proposed solutions provide support for the new low energy building design guide for office buildings along with necessary revisions to the existing standards for the Hot Summer and Cold Winter climate zone in China. [ABSTRACT FROM AUTHOR]

China building energy codes (CBEC) have been introduced for over two decades but little has been publicized in literature. LEED on the contrary is the most publicized building environmental assessment scheme. To enable better understanding of the compliance standards of CBEC, this paper presents the energy performance assessment results (represented by energy and energy cost savings) of three office buildings in China (one in Beijing and two in Shanghai) using the current versions of CBEC and LEED. The energy and energy cost savings of the three buildings were predicted based on hour-by-hour simulations using the weather data and energy tariffs of Beijing and Shanghai where the three studied buildings are located, and their actual building and system characteristics. The study revealed that LEED in general sets more stringent requirements than CBEC in indoor design conditions, building envelope characteristics and air-conditioning system features. Amongst various building end uses, energy use for air-conditioning was found dominating the assessment results, and the use of energy efficient measures not forming part of the baseline criteria, could lead to 2 to 5% reduction in the overall building energy use. The two schemes were benchmarked against BEAM Plus and their weaknesses were also unveiled. [ABSTRACT FROM AUTHOR]

A large part of energy consumption in homes, offices and commercial spaces is related to Heating, Ventilation and Air-conditioning (HVAC) devices. The effective parameter on the consumption of HVAC systems is internal heat gains that arise from occupants, electric equipment and lighting. In order to reduce the energy consumption of these systems, internal heat gains should be predicted accurately. Since there are few investigations performed on the prediction of internal heat gains, in this paper, three predictive models, namely multiple regression model, Levenberg–Marquardt back-propagation (LM-BP) model and similar days method based on combined weights, have been deployed. By assessing the influential factors on internal heat gains, fundamental theories, structures, equations and parameters of these models are thoroughly proposed. To examine the prediction techniques, an office building in China was considered. It was found that all the proposed models have high accuracy; however, the LM-BP neural network showed the most precision among other models with RMSE = 15.59, MAE = 10.16 and MAPE = 6.35. This model had a higher agreement with the actual internal heat gains compared to the predetermined working programs in the ASHRAE standard 90.1. The proposed models used in this study can lead to providing a theoretical base for scholars and engineers to improve the predictive control of HVAC systems, which plays an important role in enhancing thermal comfort, saving energy of residential buildings. [ABSTRACT FROM AUTHOR]

• A dual-objective optimization method from the perspective of designer and user. • Life-cycle energy and economy optimization for building Design Period based on HypE. • Use Low-E insulating glass, rotate the building 18°counterclockwise are beneficial. • Life cycle energy consumption and economy of the case are reduced by more than 15%. Multi-objective optimization of building life cycle energy consumption and cost is very essential for guiding design quantitatively. However, previous studies paid more attention to the potential effect of building energy saving and cost reduction based on design parameters from the perspective of designers, but ignored the potential brought by the willingness of users during operation stage. Therefore, this paper proposes a dual-objective optimization method based on the HypE algorithm, which takes into account users' energy saving intentions in order to maximize the potential of building life cycle energy saving and cost reduction. The application premise of this method is to establish energy and cost calculation model of building life cycle. The method was applied to the design of a small office building in Xi'an city of China, and the scheme were optimized by adjusting 7 design parameters and 2 parameters (cooling and heating temperature) related to the energy saving willingness of the users. The results show that the proposed method can reduce the energy consumption by 15.1%-18.8% and the cost by 2.2%-10.1% during life cycle. The results will continue to be reduced by up to 6.5% and 12.02% if the potential of uers' willingness to save energy continues to be realized. It is proved that the proposed method contributes to the comprehensive evaluation of energy saving and economic effects of architectural design during its life cycle and provides effective theoretical guidance and practical tools for architectural design and optimization. [ABSTRACT FROM AUTHOR]

Abstract: A benchmark study of the energy efficiency of private office buildings in Hong Kong was conducted in 2002 because energy efficiency was declining. In the study, private office buildings were divided into five user groups. For each group, a multiple regression model was developed to find the relationship between Energy Use Intensities (EUIs) and other factors, such as operating hours, for normalization and benchmarking purposes. In this paper we make use of the regression results to study the energy efficiency of private office buildings by different grades. In Hong Kong, office buildings are divided into three grades (A, B, and C) based on the quality of the facility, which is reflected in rental values; a Grade A office building denotes expensive luxury. We found that the EUI of Grade A office buildings is the highest, consuming over 50% of the total energy used in office buildings. Recently, the annual EUI of office buildings has improved even though Grade A floor space is increasing. This may be due to the promotion of the energy efficiency program launched in the last decade. [Copyright &y& Elsevier]

Abstract: Although variable-air-volume system (VAVS) can save much energy compared with other kind of HVAC system (e.g. constant-air-volume system (CAVS), fan-coil system (FCS)), it demands more investment. The rate of return of variable-air-volume system, which is closely related to the energy-saving rate of the system, ought to be taken into account by the engineers in the course of design. China has a wide territory and different climates that will impact on the energy-saving rate of variable-air-volume system. To help the engineers have a good idea of the rate of return of variable-air-volume system in different areas of China, it is necessary to establish such program that can evaluate the energy-saving rate of variable-air-volume system compared to constant-air-volume system and fan-coil system. In this paper, the specific energy models of the primary equipments in HVAC system are established, and the evaluation program for the energy-saving of variable-air-volume system compared to constant-air-volume system and fan-coil system are expounded. The parameters in the energy models, which may impact the validity of the evaluation program, can be obtained from the field-testing data or the performance data provided by the product manual. One small office building is taken as an example, the year-round energy simulations of the three kinds of HVAC systems (variable-air-volume system, constant-air-volume system and fan-coil system) of the same building have been made, and the energy-saving of the variable-air-volume system has been evaluated in six cities of China by the program. The evaluation program can also be used to analyze the energy-saving of variable-air-volume system in medium and big office buildings. [Copyright &y& Elsevier]

• Cooling operation of the multi-energy system (SAAC and GSHP) was discussed, three different operation configurations and their best working condition in a NZEB was analyzed. • Real energy consumption of three working modes wad analyzed and discussed. A 4025 m2 office building was built in Beijing, China, in 2014 as a living laboratory and prototype to explore the technical energy systems of nearly zero energy buildings (NZEBs) in China. Not only the building itself but also the heating, ventilation and air conditioning (HVAC) systems were designed with flexibility to explore their performance. Solar-assisted air conditioning (SAAC) and ground source heat pump (GSHP) systems with different terminal units were designed as HVAC systems for either experimental, comparison, or measurement purposes. In this paper, the cooling operation of multienergy systems is discussed on the basis of actual measurement data. HVAC systems have three possible types of operation configuration types, namely, SAAC priority, GSHP only and multimode. Operation scenarios for these configurations are presented first, and the small-scale simulation was carried out to analyze the performance of SAAC priority and GSHP#1 only mode. It indicates that SAAC could save about 47% of energy than that of GSHP#1. Then, the actual operation performance in 2018 was analyzed by reference to the operation data. Through this study, it is found that 1) multienergy systems of SAAC and GSHP operated well in this NZEBs during the summer season; 2) a 10 RT absorption chiller can work well for an NZEB building of approximately 1000 m2 when outdoor enthalpy is low and the solar radiation is stronger than 400 W/m2 as a result of high building thermal performance and air tightness; 3) SAAC can save about 40 to 50% of energy compared to that of GSHP system when providing services for the same terminal system under the same outdoor weather conditions and 4) The GSHP system is a good complement to the SAAC system which works well in June, September and early July when outdoor enthalpy is low. This study indicates that a combination of GSHP and SAAC systems is highly promising for NZEBs in cold climate zones such as Beijing, where the solar radiation is sound. [ABSTRACT FROM AUTHOR]

• Thermochromic coatings with five different colors were prepared. • Spectral reflectivity and color-changing properties of the samples were measured. • A three-step control method is used to simulate energy performance for an office building model. • Thermochromic coatings are most favorable in areas with uniformly distributed cooling and heating demands. Thermochromic coatings are promising in lowering air conditioning energy consumption of buildings. In this paper, thermochromic coatings with five different colors are prepared and their optical properties are measured. A two-story office building model is established and simulation is conducted to evaluate the energy performance of thermochromic coatings by using a three-step control method based on their dynamic color-changing properties. A comparative analysis is carried out for thermochromic coatings, cool coating and common coating. It is observed that when the building is located in Shanghai, average daily surface temperature of thermochromic coatings is lower than the common coating during cooling period and higher than the cool coating during heating period. Annual energy consumption results indicate that thermochromic coatings can avoid the penalty of increasing heating load for cool coatings. In particular, the annual energy consumption of the office building using thermochromic coatings can be reduced by 4.28–5.02 kWh/m2 compared to the common coating, and 0.73–1.47 kWh/ m2 compared to the cool coating. Simulation of other cities in different climate zones in China reveals that thermochromic coatings have better energy saving effects especially for the areas with hot summers and cold winters, and relatively uniform distribution of cooling and heating demands. [ABSTRACT FROM AUTHOR]

• We selected three benchmarking methods to establish building energy benchmarking models based on a sample of 45 hotel buildings in China. • We compared the three benchmarking methods in terms of consistency, robustness and explanatory ability. • The energy efficiency performance obtained from the three methods were found to be inconsistent. • We came up with suggestions based on comparative analysis for policy-makers to develop building energy benchmarking programs. A reasonable building energy efficiency benchmarking program plays an important role in energy consumption control and supervision. Previous studies have focused on the process of establishing a single benchmarking method, but few have compared the performances and outcomes of different methods. To fill this gap, this paper selects three benchmarking methods—multiple linear regression (MLR) based on Energy Star, stochastic frontier analysis (SFA) and the descriptive statistics method (DSM) based on the national energy consumption standard in China—to develop benchmarking models. We demonstrate each method using data on the energy and building characteristics of 45 four- and five-star hotel buildings located in Chongqing, China. To compare the consistency, robustness and explanatory ability of the three methods, we first utilize the Spearman rank correlation analysis to test whether these methods have consistent energy efficiency ranks and then present Sankey diagrams to further reveal the interactions of the estimated energy efficiency grades obtained from the three methods. It is found that the results of DSM and SFA are most consistent, while MLR vs. SFA and MLR vs. DSM present significant differences in evaluating building energy performance. In addition, DSM is more robust for evaluating the ranks of sampled buildings, while SFA is more robust for evaluating energy efficiency grades. Furthermore, we discuss the explanatory ability of each method. In addition to the building characteristics, the design and operational characteristics of the HVAC system have great effects on building energy consumption. Finally, we present suggestions for policy-makers regarding the development and implementation of the building energy benchmarking program in Chongqing and for the management of buildings with different energy performances to further improve the energy efficiency. [ABSTRACT FROM AUTHOR]

A ceiling-sidewall composite air carrying energy radiant air-conditioning system (ACERS) is presented, and the heating performance of the ceiling-sidewall composite ACERS combined with air source heat pump is investigated by field experiment. The results show that the combined system can meet the heating requirement for office buildings in south-central China, and also have the energy-saving potential. Moreover, the indoor thermal environment under three different installation types, namely the ceiling, the sidewall, and the ceiling-sidewall composite type, is analyzed by using computational fluid dynamic (CFD) simulation. The comparisons of three types indicate that all of them can meet the temperature requirement, but the temperature is more uniform and higher in the composite ACERS. Meanwhile, the temperature gradient in the ceiling ACERS is smaller than that of the sidewall ACERS due to the further heat transfer caused by air penetration. Both the experimental and CFD simulated temperature distribution demonstrates that the shelter of furniture has an impact on the indoor thermal environment, and it should not be ignored in practical engineering. This research shows the feasibility of winter heating by using the ACERS in office buildings, and is helpful for HVAC engineers to design and apply different ACERS types and realize the integration of air conditioning in winter and summer in this area. [ABSTRACT FROM AUTHOR]