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Electrochromic (EC) glazing provides a promising solution to actively adjusting the sunlight and radiant heat through windows in response to building visual and thermal environmental requirements, and control strategies play a critical role in the application of EC technology in buildings. However, there is a conflict between the visual and thermal environmental requirements for EC regulation during a cooling season. To solve this problem, this paper developed a predictive control strategy for EC glazing. It was achieved based on two theoretical models which could predict the energy performance of EC glazing at different tint states, including the solar radiation heat transmitted through the glazing and lighting energy consumption. The optimum glazing state was determined based on real-time minimized energy consumption. Study results showed that the predictive control strategy outperformed the rule-based control strategy, with percentage energy saving of an office room in Beijing, China from 8.04% to 12.78% over an entire cooling season. In addition, the paper evaluated the energy-saving of using EC glazing under the predictive control strategy in 28 Chinese cities. The results indicated that EC glazing was highly applicable in most of cities with energy saving from 2.35 kWh/m2 to 5.04 kWh/m2 over an entire cooling season. • A predictive control strategy for EC glazing was developed. • Theoretical models were established to predict the EC glazing energy performances. • Real-time minimized energy consumption determined the optimum EC glazing state. • Balance between the visual and thermal environment requirements was achieved. • The energy-savings of using EC glazing in 28 Chinese cities were assessed. [ABSTRACT FROM AUTHOR]

Split-pane electrochromic (EC) windows enable the control of glare and the effective utilization of sunlight by adjusting the color of individual window panes. However, existing EC control methods are often limited to specific cases or require extensive simulation work, resulting in a deficiency of generic control approaches. To solve this issue, this paper proposed a novel approach to EC window zoning control based on glare prediction. This method evaluated real-time discomfort glare for each EC window pane and effectively adjusted the tinting state of the split panes to mitigate glare. A typical office setting in Beijing was selected to simulate the impact of utilizing this method on the light environment and energy conservation. The simulation results demonstrate that this approach could effectively keep the discomfort glare probability (DGP) below 0.4, which belongs to perceptible glare. Compared to EC whole window control, it reduced the tinting area multiplier hours by 63.64%–71.43%, managed UDI values within the range of 40%–90%, and reduced lighting energy consumption by over 40.98%. The results confirmed the accuracy of the proposed method in glare control, the improvement of the lighting environment, and the significant reduction in lighting energy consumption, enhancing its substantial energy-saving potential. [ABSTRACT FROM AUTHOR]

• A sizing method considering the joint effect of T a and RH was developed. • A capacity design correction factor (K) was proposed and evaluated. • Frosting caused the outdoor air design temperature for space heating to drop by 1.8–3.5 °C. • Maximum decrease rates of output heating capacity caused by frosting was 43.8–50.0% • A cloud picture was given by using the values of K in 278 Chinese cities. In cities, there are thousands of wastewater treatment plants. The treated tail water drained from them is clean relatively, and has a stable flow rate. Extracting heat from it through tail water source heat pumps (TWSHP) for space heating can decrease the building heating energy consumption significantly. Besides, by integrating with thermal energy storage (TES), it can realize the goal of peak load shifting, especially in commercial buildings. However, there is few reports on its experimental investigations or engineering applications till now. To promote the application of TWSHP integrated with TES system, it was designed for the space heating of a technology park in Beijing, and a control method was proposed to decrease the operating cost by using the valley electricity. Then, utilizing its operating parameters in the heating season of 2021–2022, its heating performance was analyzed. Results indicate that the proposed system has good heating performance. The average COPs of TWSHP units and the system in the heating season are 7.08 and 4.41, respectively. Compared with gas-fired boiler, its carbon emission decreased by 62.53%. By using the TES system, the power consumption during valley period of power grid increases by 581.23%, realizing the goal of peak load shifting. [ABSTRACT FROM AUTHOR]

Multi-source looped district cooling (MLDC) systems exhibit promising application potential owing to their ability to utilize various renewable energy resources. The load dispatch for multiple sources is considered a critical factor during operation owing to its effects on the energy and hydraulic performance. However, few studies have investigated the behavior of energy and hydraulic performance under different load dispatch ratios (LDR s). In addition, straightforward methods for determining the optimal load dispatch of MLDC systems have not been introduced. This study investigated the relationship between the load dispatch and operating performance and proposed a fundamental method to achieve optimal load dispatch for MLDC systems and overcome the existing challenges. A double-source looped district cooling system was selected as the case study, and its Modelica model was developed. Subsequently, we investigated the relationship between the LDR s and operating performance, and verified the existence of an optimal LDR (LDR opt), which achieves the best hydraulic performance and lowest energy consumption. Finally, a dataset constructed using a hybrid optimization algorithm was employed to develop a multi-variable data-driven model for predicting LDR opt under various load conditions. This study provides a valuable framework and recommendations for further investigation of the optimal control of MLDC systems. • The Modelica model of an MLDC system in Beijing was developed and validated. • The hydraulic and energy performances under different load dispatch ratios was investigated. • The existence of the LDR opt for the MLDC system was verified. • A multi-variable linear prediction model of LDR opt was developed. [ABSTRACT FROM AUTHOR]

• Reinforcement learning (RL) is introduced to the large-scale MLDC systems. • Performance gaps between RL control and rule-based control are analyzed. • Time lag of RL control and rule-based control has been investigated. • RL control achieves maximum energy savings of 12.99%. Large-scale multi-source looped district cooling (MLDC) systems are expected to be a promising solution to support decarbonization goals and combat climate change owing to their advanced structure. Differential pressure control is one of the most common methods to improve the energy and hydraulic performance of MLDC systems. Traditional rule-based control (RBC) and model-based control may not be appropriate for large-scale systems because of the need for expert knowledge and accurate models. Reinforcement learning control (RLC) has attracted considerable research attention owing to its efficiency and flexibility. However, very little is known about RLC in large-scale heating, ventilation, and air conditioning (HVAC) systems and complex issues. Therefore, this study employs a reinforcement learning technique to optimize the differential pressure setpoints of multiple cold sources, which can achieve energy savings and fulfill hydraulic head demands simultaneously. In this study, a Modelica model of a large-scale MLDC system in Beijing was developed as a virtual environment. The Modelica-Python co-simulation testbed for RLC was then implemented. The results show that RLC can save up to 12.99% of the annual distribution energy consumption while achieving a good hydraulic performance. As an information base for a variety of stakeholders, this study offers a reinforcement learning solution that can improve the operating performance of large-scale HVAC systems. [ABSTRACT FROM AUTHOR]

Thermochromic (TC) window has been developed as an effective approach to realize building energy saving by regulating solar transmittance according to temperature stimuli; however, the non-uniform transmission and absorption of the solar spectrum result in a significant color shift and temperature increase. This study investigates the radiometric, photometric and colorimetric performances of four different TC windows with an experiment-verified model. The simulation and calculation are conducted under measured spectrum conditions in Beijing; subsequently, a comprehensive evaluation method for daylight-thermal environment method is conducted. The results show that all selected TC windows possess an energy efficiency between 3.0% and 7.9%, improve daylight availability from 2.8% to 18.8%, and reduce discomfort hours by up to 111 h. Two hydrogel TC windows improve the quality of dynamic transmitted daylight by nearly 7% considering correlated color temperature and color rendering index; the HETS hydrogel TC window is found to be the most suitable for Beijing. Finally, to increase the application potential of TC windows in Beijing, several material properties are desired, including high transition temperature with high solar modulation capability, high and uniform visible light transmittance, and low emissivity. This process for the optimization of climate-responsive material can be further adopted in other areas. • Four different thermochromic windows are compared for the Beijing climate. • The annual dynamic spectrum of Beijing is measured and adopted as a boundary condition. • The model is verified by experiments based on measured meteorological conditions. • Comprehensive evaluation, including radio, photo, and color aspects, is conducted. • Constructive suggestions on regionally suitable window characteristics are given. [ABSTRACT FROM AUTHOR]

• Regional performance evaluation indexes based on ETD method were developed. • All the ambient conditions over an entire heating season were considered. • The regional performances of ASHPs operated in any regions may be evaluated. • The key factors affecting operating performances of ASHP units were specified. • The regional performances of ASHPs operated in 278 Chinese cities were assessed. During the actual operation of an ASHP unit installed in different climate regions, ambient operating conditions can vary constantly over an entire heating season, thus the actual output heating capacity of ASHP units may vary significantly from region to region. To enable a convenient evaluation of output heating capacity of a space heating ASHP unit installed in different climate regions, regional performance evaluation indexes including T a ′ ¯ , HERR (T a') , β Ta and β RH based on ETD method have been developed. These evaluation indexes are generalized and can be used to evaluate the regional performance of ASHP units operated in any regions. It can also be used to specify the key factors affecting the operating performances of ASHP units in different regions. With the developed evaluation indexes, the regional operating performances of ASHP units installed in 278 Chinese cities were evaluated. The results demonstrated that the total output heating energy for ASHP units operated in Southern Chinese provinces may be lower than those in Northern China. In Shanghai, T a ′ ¯ at −6.0 °C is lower than that at −3.0 °C in Beijing, suggesting the total output heating energy from an ASHP units operated in Shanghai over an entire heating season would be lower than that in Beijing. Furthermore, in southern Xinjiang and northern Fujian Provinces, the total output heating energy from ASHP units may be higher than those operated at the nominal condition. In addition, in Tibet, Beijing, Liaoning, etc., the total output heating energy from the ASHP units would be affected more by T a , thus ASHPs' manufacturers are recommended to develop ASHP units suitable for operation in low temperature ambient. In most regions in southern China, RH would affect more on the total output heating energy from the ASHP units, thus ASHPs' manufacturers are recommended to develop ASHP units having frosting suppression provisions and accurate defrosting measures. [ABSTRACT FROM AUTHOR]

[Display omitted] • The influences of PM 10 concentrations on SPD values are investigated. • A strong influence of PM 10 on SPD could be noticed ranging from 380 to 540 nm. • A band of 510 nm is adopted to establish models and its models has been validated. • Other bands are also validated and the band ranges from 480 to 520 nm. • Quantitative study on SPD under PM 10 levels promotes building energy-efficient design. Daylight refers to a free and valuable resource exhibiting photometric and radiometric features, and the physical parameters commonly used to represent its features are irradiance and illuminance. They are both obtained by the spectral power distribution (SPD) of global irradiance, demonstrating that values noticeably affect indoor thermal and luminous environments. Nevertheless, outdoor particulate matter (PM) significantly affects SPD conditions, and two relative spectral notions, i.e., percentage of spectral irradiance (PSI r) and percentage of spectral illuminance (PSI l), were proposed to study the effects of PM 10 concentrations in radiometry and photometry with a field measurement, Beijing. As a result, the strong impact of PM 10 on PSI r / PSI l can be noticed in the range (380 to 540 nm) (P-value < 0.01) by correlation analysis, and a wavelength of 510 nm was taken to build models between PM 10 and PSI r / PSI l based on regression analysis. With this wavelength, PSI r varies from 0.29 to 0.25%, and PSI l ranges from 0.48 to 0.42% with the increase of PM 10 concentrations from 0.01 to 0.098 mg/m3. With the verification of the model, several bands were further analyzed to comprehensively verify the monotonic correlations, and the band ranging 480 ~ 520 nm were reasonably proved that PSI r /PSI l and PM 10 can be well indicated by each other. As influenced by the complexity of spectral transmittance through the glazing, the mutual characterization between solar spectrum and particulate matters can contribute to the building energy-efficient design and develop indoor thermal and luminous environment research in the future. [ABSTRACT FROM AUTHOR]

• An equivalent temperature drop (ETD) method was developed. • It considered the joint effect of T a and RH on the performances of ASHPs. • The applicability of the ETD method was verified by a field test. • The performances of ASHPs may be conveniently evaluated. • Impacts from either T a or RH may be individually assessed. It has been known that the actual operating performances of a space heating ASHP unit are significantly impacted by the joint effect of ambient air temperature, T a , and relative humidity, RH. To enable a convenient evaluation of the operating performances of a space heating ASHP unit with a reasonable accuracy, an equivalent temperature drop (ETD) method has been developed. The ETD method transferred the impacts of frosting-defrosting on the operating performances of ASHP units into that of an equivalent ambient air temperature drop, so that the joint effects of T a and RH on the actual operating performances of the ASHP units may be assessed using a single parameter of equivalent ambient air temperature. In this paper, the models for predicting the output heating capacity of an ASHP unit operated at both frosting and non-frosting conditions were firstly established through either regression analysis or referring to previous related studies. Secondly, with the availability of the models, the ETD method was developed for evaluating the actual operating performances of ASHP units at different ambient conditions. Thirdly, the developed ETD method was verified by a field study on the operating performances from an ASHP unit installed in Beijing. The field study results demonstrated that for any frosting operating conditions, using the ETD method, a corresponding non-frosting condition at which the field ASHP would output the same heating capacity may be identified. Furthermore, the use of ETD method can also distinguish the individual impacts from either T a or RH on the actual operating performances of an ASHP unit. [ABSTRACT FROM AUTHOR]