Theoretical efficiency limit and realistic losses of indoor organic and perovskite photovoltaics [Invited]

Indoor organic and perovskite photovoltaics(PVs)have been attracting great interest in recent years.The theoretical limit of indoor PVs has been calculated based on the detailed balance method developed by Shockley–Queisser.However,realistic losses of the organic and perovskite PVs under indoor illumination are to be understood for further efficiency improvement.In this work,the efficiency limit of indoor PVs is calculated to 55.33%under indoor illumination(2700 K,1000 lux)when the bandgap(E_(g))of the semiconductor is 1.77 eV.The efficiency limit was obtained on the basis of assuming 100%photovoltaic external quantum efficiency(EQ_(EPV))when E≥E_(g),there was no nonradiative recombination,and there were no resistance losses.In reality,the maximum EQEPV reported in the literature is 0.80–0.90.The proportion of radiative recombination in realistic devices is only 10^(−5)–10^(−2),which causes the open-circuit voltage loss(ΔV_(loss))of 0.12–0.3 V.The fill factor(FF)of the indoor PVs is sensitive to the shunt resistance(R_(sh)).The realistic losses of EQE_(PV),nonradiative recombination,and resistance cause the large efficiency gap between the realistic values(excellent perovskite indoor PV,32.4%;superior organic indoor PV,30.2%)and the theoretical limit of 55.33%.In reality,it is feasible to reach the efficiency of 47.4%at 1.77 eV for organic and perovskite photovoltaics under indoor light(1000 lux,2700 K)with V_(OC)=1.299 V,J_(SC)=125.33μA/cm^(2),and FF=0.903 when EQE_(PV)=0.9,EQE_(EL)=10^(−1),R_(s)=0.5Ωcm^(2),and R_(sh)=10^(4) kΩcm^(2).

基于Flexible YOLOv7的输电线路绝缘子缺陷检测和故障预警方法

电力设备的平稳运行是保障居民生产生活的重要前提。输电线路绝缘子缺陷尺寸较小,传统的目标检测算法通常难以识别到缺陷目标,误检、漏检率较高。针对不同材质绝缘子缺陷检测存在目标过小、遮挡、背景复杂等难题,提出了一种基于Flexible YOLOv7的绝缘子缺陷检测算法。该算法继承了YOLOv7网络的E-ELAN结构、Rep重参数化和辅助训练策略,并且在特征提取的过程中集成GAM注意力机制以放大显著的跨维度接受区域,通过高效的Ghost SPPCSPC结构减少模型训练过程中的参数冗余,引入Efficient IOU Loss重点关注高质量的anchors提升原始模型的检测精度。最后通过图像后处理技术对绝缘子缺陷进行等级划分与精细计算,并结合算法部署开发了绝缘子缺陷故障检测系统用于故障的提前预警。实验结果表明,该算法在密集目标、遮挡、小目标缺陷检测中的平均准确率AP、召回率Recall、相关指标F1指标均领先于当前先进的几类目标检测算法,在复杂环境下的绝缘子缺陷检测和故障预警方面具有一定的现实意义。

Dust Deposition’s Effect on Solar Photovoltaic Module Performance:An Experimental Study in India’s Tropical Region

A solar PV panel works with maximum efficiency only when it is operated around its optimum operating point or maximum power point.Unfortunately,the performance of the solar cell is affected by several factors like sun direction,solar irradiance,dust accumulation,module temperature,as well as the load on the system.Dust deposition is one of the most prominent factors that influence the performance of solar panels.Because the solar panel is exposed to the atmosphere,dust will accumulate on its surface,reducing the quantity of sunlight reaching the solar cell and diminishing output.In the proposed work,a detailed investigation of the performance of solar PV modules is carried out under the tropical climatic condition of Chennai,India,where the presence of dust particles is very high.The data corresponding to four different dust samples of various densities at four solar irradiation levels of 220,525,702,and 905 W/m^(2)are collected,and performance analysis is carried out.Based on the analysis carried out,the maximum power loss is found to be 73.51%,66.29%,65.46%,and 61.42%,for coal,sand,brick powder,and chalk dust respectively.Hence,it can be said that coal dust contributes to the maximum power loss among all four dust samples.Due to heat dissipation produced by dust deposition,the performance of solar PV modules is degraded as the temperature rose.

Decomposition of China＇s Industrial Environmental Total Factor Productivity Sources： Analysis Based on Factor Input and Pollution Treatment

Following slack-based inefficiency measurement method and Luenberger productivity index, this paper decomposes industrial environmental TFP index by input factors and output to estimate the sources of China＇s industrial environmental TFP. Results indicate that （1） China＇s industrial environmental TFP increased between 2001 and 2007 but declined in 2008 under the effect of global financial crisis; （2） input utilization productivity contributes 1/3 to industrial environmental TFP and pollution treatment productivity contributes about 2/3, which means that pollution treatment will effectively increase industrial environmental TFP; （3） capital utilization productivity contributes I/6 to input productivity and labor utilization productivity contributes about 5/6, which means that progress of labor production technologies is an effective means to increase industrial environmental TFP; （4） COD treatment productivity contributes roughly 2/3 to pollution treatment productivity, and S02 treatment productivity contributes about 1/3, which shows that priority on COD treatment will more effectively increase industrial environmental TFP.

Progress in hole-transporting materials for perovskite solar cells

In recent years the photovoltaic community has witnessed the unprecedented development of perovskite solar cells（PSCs） as they have taken the lead in emergent photovoltaic technologies. The power conversion efficiency of this new class of solar cells has been increased to a point where they are beginning to compete with more established technologies. Although PSCs have evolved a variety of structures, the use of hole-transporting materials（HTMs） remains indispensable. Here, an overview of the various types of available HTMs is presented. This includes organic and inorganic HTMs and is presented alongside recent progress in associated aspects of PSCs, including device architectures and fabrication techniques to produce high-quality perovskite films. The structure, electrochemistry, and physical properties of a variety of HTMs are discussed, highlighting considerations for those designing new HTMs. Finally, an outlook is presented to provide more concrete direction for the development and optimization of HTMs for highefficiency PSCs.

Determination of a suitable set of loss models for centrifugal compressor performance prediction

Performance prediction in preliminary design stages of several turbomachinery components is a critical task in order to bring the design processes of these devices to a successful conclusion. In this paper, a review and analysis of the major loss mechanisms and loss models, used to determine the efficiency of a single stage centrifugal compressor, and a subsequent examination to determine an appropriate loss correlation set for estimating the isentropic efficiency in preliminary design stages of centrifugal compressors, were developed. Several semi-empirical correlations,commonly used to predict the efficiency of centrifugal compressors, were implemented in FORTRAN code and then were compared with experimental results in order to establish a loss correlation set to determine, with good approximation, the isentropic efficiency of single stage compressor.The aim of this study is to provide a suitable loss correlation set for determining the isentropic efficiency of a single stage centrifugal compressor, because, with a large amount of loss mechanisms and correlations available in the literature, it is difficult to ascertain how many and which correlations to employ for the correct prediction of the efficiency in the preliminary stage design of a centrifugal compressor. As a result of this study, a set of correlations composed by nine loss mechanisms for single stage centrifugal compressors, conformed by a rotor and a diffuser, are specified.

Restructuring and differentiated regulatory policies in China’s petroleum industry

China’s petroleum industry is monopolistic in its main business activities.However,the reasonability of this monopoly needs to be discussed according to its technical and economic characters.Research results show that the petroleum pipeline transportation business is naturally monopolistic while other businesses are competitive.Those business activities which can be open to competition but are in fact monopolistic are so owing to administrative order,and run inefficiently as a consequence.In order to improve productive efficiency and reduce efficiency losses,we propose three restructuring patterns of the petroleum industry-the Access Control Model,the Ownership Separation Model,and the Mutual-benefit Network Model.These three models have both advantages and disadvantages.Considering the prevailing practices in the petroleum industry in China,we think that the best choice is the Access Control Model.In order to improve restructuring effects of regulatory patterns,we design three differentiated regulatory policies,including differentiated entry regulation policies,differentiated price regulation policies,and differentiated distribution of different ownership enterprises policies.

Fate of Basal N Under Split Fertilization in Rice with ^(15)N Isotope Tracer

Split fertilization strategy is popularly adopted in rice to synchronize soil nitrogen(N) supply and crop N demand. Attention has been paid more on mid-season topdressing N, but limited on basal N. A clearer understanding of the basal N fate under split fertilization is crucial for determining rational basal N split ratio to improve the yield and reduce the loss to environment. A two-year field experiment with two N rates of 150 and 300 kg Nha^(-1), two split ratios of basal N, 40% and 25%, and two rice varieties,Wuyunjing 23(japonica) and Y-liangyou 2(super hybrid indica), was conducted. Labelled ^(15) N urea was supplied in micro-plots as basal fertilizer to determine the plant uptake, translocation, soil residual, and loss of basal N fertilizer. The results showed that basal N absorbed by rice was only 1.6%–11.5% before tillering fertilization(8–10 d after transplanting), 6.5%–21.4% from tillering fertilization to panicle fertilization, and little(0.1%–4.4%) after panicle fertilization. The recovery efficiency of basal N for the entire rice growth stage was low and ranged from 18.7% to 24.8%, not significantly affected by cultivars or N treatments. Soil residual basal N accounted for 10.3%–36.4% and decreased with increasing total N rate and basal N ratio, regardless of variety and year. 43.8%–70.4% of basal N was lost into the environment based on the N balance. Basal N loss was significantly linearly positive related with the basal N rate and obviously enhanced by the increasing basal N ratio for both varieties in both 2012 and 2013. The N use efficiency and yield was significantly improved when decreasing the basal N ratio from 40% to 25%. The results indicated that the basal N ratio should be reduced, especially with limited N inputs, to improve the yield and reduce the N loss to the environment.