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Summary: The Energy and Evaluation Special Committee of the China Price Association proposed two types of bill for battery energy storage (BES) subsidies in 2017: the first was that energy storage should be subsidised based on the initial installation capacity of BES system, while the second was that it should be subsidised based on the energy discharged by the BES system during the operational period. The economic benefits of a distributed photovoltaic (PV) system or a distributed system with PV and BES in the overall life cycle are discussed in the context of an industrial zone in Shanghai. The results suggest that the net present value (NPV) of a PV‐BES system with an optimised configuration is higher than the NPV of a PV system alone. The NPV of a distributed PV system with four different BESs is found to decrease in the order Li‐ion > NaS > VFB > Pb‐C because of the characteristics of their batteries. The NPVs of PV‐BES systems increase in equal proportion to the increase in the BES subsidy based on installation capacity for these four BES systems, while they show an inequable growth rate of earnings for the same BES subsidy based on the energy discharged over the operational period. The second bill for BES subsidy is more beneficial to the BES industry than the first, as it encourages higher pay for more work. [ABSTRACT FROM AUTHOR]

Under the influence of haze, the concentration of fine particles (PM2. 5) in the atmosphere is higher, which makes the direct radiation of solar energy lower and the scattered radiation increases. Therefore, the irradiance received by the surface of the photovoltaic module is reduced. The existing power generation estimation formula should be revised, hence a new formula for estimating power generation is proposed with the error range ± 5% from the actual power generation. Moreover, this paper explores the effect of PM2. 5 concentration on irradiance, irradiation and power generation. Through a photovoltaic roof test in a household in Shanghai, the irradiance control variable method and similar day principle are used to analyze the irradiance loss and power generation loss caused by PM2. 5, and to fit the relationship between them. At the same time, the concept of photovoltaic power generation loss index is proposed, which provides reference for the installed capacity of photovoltaic system and the reliability of photovoltaic system in the future . [ABSTRACT FROM AUTHOR]

Highlights • An index is developed to detect building shadows from Sentinel-2 A MSI imagery. • The proposed shadow index was found insensitive to water and low albedo. • The proposed index over-preformed P algorithm, NSVDI, SI and the improved Fmask. • The index can detect contiguous building shadows cast by fine urban structures. Abstract Images from Multispectral Instrument (MSI) on Sentinel-2A are useful for studies of urban environments and their spatio-temporal changes. However, the frequent occurrence of building shadows in urban areas brings about great challenges in urban studies. Existing building shadow indices are not effective for Sentinel-2A MSI images due to that these indices do not make full use of the rich spectral information contained in Sentinel-2A. In this study, we propose a combinational shadow index (CSI) to address this challenge. In the formulation of CSI, three features, including the proposed shadow enhancement index (SEI), the normalized difference water index (NDWI) and the NIR band (B8), were combined to separate spectrally similar objects, such as building shadows, water and low albedo features at the Earth surface. The accuracy and robustness of CSI were tested by using six data sets from four cities, including Beijing, Shanghai, Guangzhou and Shenzhen in China. The performance of CSI was compared with three existing shadow indices, i.e., P algorithm, the normalized saturation-value difference index (NSVDI) and the shadow index (SI). Results show that CSI can detect building shadows with fine structures in both clear and cloudy images more effectively and worked well on large areas too. CSI can separate shadows from water and low albedo features as measured by a spectral discrimination index (SDI). Compared with the existing building shadow indices, CSI can improve the performance of building shadow detection by combining the feature information of SEI, NDWI and NIR band, and yielded satisfactory results for extracting building shadows from Sentinel-2A MSI imagery. [ABSTRACT FROM AUTHOR]

PV windows provide thermal insulation, daylight use and power generation simultaneously. Present investigation aimed to evaluate the energy performance of 3 types of PV windows under 5 climates of China, and particularly to clarify the influences of transmittance and orientation on its energy performance. The present work involves: (i)the experimental testing that had been carried out; (ii)validation of the EnergyPlus model of natural ventilated double PV (NVDPV) window; (iii) prediction of the energy performance of the 5 PV windows under typical climates of China based on the validated model; (iv) applicability discussion of the PV windows under different climates and influence of transmittance and orientation. The results reveal the highest energy saving rate obtained by NVDPV window in the 5 cities. The NVDPV window integrated PV glass with transmittance of 10% delivered better energy performance than the window with transmittance of 5% under climates of Harbin, Beijing, Shanghai and Shenzhen. The south facing windows achieved least building electricity consumption under the climates of Harbin, Beijing, Shanghai, and Lhasa. Exceptionally, the east facing windows achieved least electricity usage under the climate of Shenzhen. The achievements from the present work provide a reliable criterion for the optimized design of PV windows. • Energy performance of PV windows was predicted with EnergyPlus under different climates. • Thermal, optical and electrical models of natural ventilatedPV window were validated. • The natural ventilated PV window delivered the best annual energy performance. • Transparency and orientation of the PV window were optimized for different cities. [ABSTRACT FROM AUTHOR]

The existing calculation and evaluation methods for photovoltaic directly driven air conditioners (PVAC) are often based on a long timescale without considering the short-term rapid fluctuations of environmental parameters. This study proposes a comprehensive method for evaluating real-time zero energy potentials of PVACs. Firstly, an optimal determination method for PV size from the timely energy matching perspective was discussed. Then, the energy generation and consumption based on different time scales in different climate regions were simulated and analyzed. Finally, the zero-energy potentials of PVACs with the optimal PV size in different climate regions were investigated. The potentials were evaluated based on the indices of hourly self-sufficiency, hourly self-consumption, zero energy probability, and PV generation utilization. Besides these indicators, a graphical approach was also provided to enable the visualization of the real-time energy matching performance of PVACs. The results showed that different climatic conditions had significant effects on energy matching performance. Under the premise that the total PV generation can fully meet the electricity consumption of air conditioner, the number of hours that PVAC, without assistance, can realize real-time zero energy consumption only accounts for 26.40% of the whole year in Shenyang and 37.17% in Shanghai. To summarize, the method and indicators for optimizing PV capacity and evaluating dynamic energy matching for different climate zones were proposed from the perspective of achieving real-time zero energy. [ABSTRACT FROM AUTHOR]

The widespread application of advanced renewable systems with optimal design can promote the cleaner production, reduce the carbon dioxide emission and realise the renewable and sustainable development. In this study, a phase change material integrated hybrid system was demonstrated, involving with advanced energy conversions and multi-diversified energy forms, including solar-to-electricity conversion, active water-based and air-based cooling, and distributed storages. A generic optimization methodology was developed by integrating supervised machine learning and heuristic optimization algorithms. Multivariable optimizations were systematically conducted for widespread application purpose in five climatic regions in China. Results showed that, the energy performance is highly dependent on mass flow rate and inlet cooling water temperature with contribution ratios at around 90% and 7%. Furthermore, compared to Taguchi standard orthogonal array, the machine-learning based optimization can improve the annual equivalent overall output energy from 86934.36 to 90597.32 kWh (by 4.2%) in ShangHai, from 86335.35 to 92719.07 (by 7.4%) in KunMing, from 87445.1 to 91218.3 (by 4.3%) in GuangZhou, from 87278.24 to 88212.83 (by 1.1%) in HongKong, and from 87611.95 to 92376.46 (by 5.4%) in HaiKou. This study presents optimal design and operation of a renewable system in different climatic regions, which are important to realise renewable and sustainable buildings. • Models and feasibility of a hybrid system were studied in five climatic regions. • Energy contradictions were studied to improve efficiency with effective solutions. • Intelligent control and sensitivity analysis were studied on the hybrid system. • A machine-learning based optimization method was proposed with advanced algorithms. • Optimal design and operation were conducted for renewable and sustainable buildings. [ABSTRACT FROM AUTHOR]

• A novel coupled optical-electrical-thermal model of the bifacial PV module is developed. • Global irradiances of the front and rear sides are calculated by view factor and irradiance model. • Over 22% of the average bifacial gain can be achieved via yearly performance estimation. • Suggestions for optimizing the bifacial PV module performance are proposed. The bifacial photovoltaic (PV) technology has become prevalent in the global market in recent years as it can simultaneously collect the sunlight from both front and rear sides to achieve high power generation, however, there is limited attention from academic circle on this new technology particularly theory study in multiphysics simulation. This paper develops a comprehensive optical-electrical-thermal model for the bifacial PV module, in which the global irradiances of the tilted front and rear surfaces are obtained through the optical model, the cell temperature through the thermal model, and the power output through the electrical model accordingly. After validation, the coupled model is employed to conduct daily and yearly performance estimations, demonstrating 25.58% and 28.21% of the daily bifacial gain for sunny and cloudy days, respectively, and more than 22% of the yearly bifacial gain for Hong Kong and Shanghai. Besides, it is found that the bifacial gain under low irradiance is relatively high due to high diffuse fraction, indicating that bifacial modules have an advantage in adapting to various weather conditions, especially cloudy days. Furthermore, some suggestions are proposed to optimize the bifacial module by considering the effects of various installation and weather parameters on the PV generation. A tracking bifacial module, installed at an optimum tilt angle with high albedo, elevation, irradiance and wind velocity, but low ambient temperature, could achieve high energy yield, while a bifacial module facing east with high albedo, tilt angle, elevation, diffuse fraction, ambient temperature and wind velocity could achieve high bifacial gain. [ABSTRACT FROM AUTHOR]