Modeling the current-voltage characteristics of thin-film silicon solar cells based on photo-induced electron transfer processes

Power conversion efficiency of p-i-n type microcrystalline silicon (c-Si:H) solar cells has been analyzed in terms of sequential processes of photo-induced electron transfer. The effect of the excitonic state on the charged carrier generation has been studied compared to a conventional scheme in which only charged carriers are taken into account for the operation of the solar cells. A numerical model has been developed to calculate current-voltage characteristics of solar cells on the basis of two types of charged carrier generation processes (exciton process and charged carrier process). The light trapping effect due to a textured back surface reflector (BSR) was embedded in the numerical model by using the effective medium theory in combination with the matrix method in the field of the electromagnetic theory of light. As an application of this modeling, it was found that the reported data of the power conversion efficiency were not explained by the conventional charged carrier process model and that the combined model of the charged carrier process with the exciton process well explains the performance of the p-i-n type c-Si:H solar cells. In this way, the typical power conversion efficiencies were estimated to be 10.5% for the device (i-layer thickness: 1.8 m) with the BSR (period: 600 nm; height: 250 nm) and 8.6% for the device with the flat reflector under the condition that the fractions of the exciton process and charged carrier process were 60% and 40%, respectively.     

Battery powered electric vehicles charged via solar photovoltaic arrays developed for light agricultural duties in remote hilly areas in the Southern Mediterranean region

In the Southern Mediterranean region hilly and remote areas are afflicted with the high cost of diesel fuel, problematic supply, poor or non-existent grid connections and lack of maintenance technicians to service farm grid generation systems and machinery. A prototype Battery Powered Electric Vehicle (BPEV) charged using a solar photovoltaic array (10 kWp) was installed at a monastery situated at Achkout (Lebanon) with a total agricultural area of 50 ha, 10 ha of which was devoted to viticulture. The purpose of this was to investigate the potential for the cleaner production of power hence reducing the use of diesel fuels in agriculture. Data collected from the test site is presented and used to validate a numerical model. The numerical model was then used to extend the study further to the other countries bordering the Mediterranean Sea which have different levels of solar irradiance. Currently the average cost of diesel fuel within the EU is at an all-time high of 1.32 €/L. A life cycle costing determined that if the current trends in inflation in the EU continue and that fuel costs increase by 7.5% per annum, then battery powered electric vehicles charged using solar photovoltaics are economically viable in areas of high solar irradiance. The numerical model was then used to determine the outcome of using lithium titanate batteries instead of conventional lead-acid batteries. Adoption of the described system for a 10 ha vineyard would result in annual fuel saving of 4200–5200 L of diesel depending on which location in the Mediterranean area a system such as this is installed.     

Photo-induced electron transfer processes in thin-film solar cells

Power conversion efficiency of single heterojuntion and bulk heterojunction thin-film solar cells has been analyzed in terms of sequential processes of photo-induced electron transfer. Furthermore, a numerical model was developed to predict current-voltage characteristics of solar cells on the basis of photo-induced electron transfer processes. As an application of this modeling, the power conversion efficiency was analyzed for the donor/acceptor (CuPc/C60) heterojunction under various conditions. In this way, the maximum power conversion efficiency, under 1 sun AM 1.5 solar illumination, was estimated to be 6.1% for the optimum single heterojunction structure. As for the bulk heterojunction structure, a vertical lattice (alternating donor/acceptor lamellae perpendicular to a substrate) structure was proposed and the maximum power conversion efficiency was estimated to be 10.8%. It was concluded that the power conversion efficiency of the vertical lattice bulk heterojunction cell could be increased up to ca. 15% by the improvement of the hole mobility of the donor film.     

TiO2及负载Fe(Ⅲ)可见光催化H2O2降解扑草净的协同效应

以TiO2P25(TIO-P25)及Fe(NO3)3为前驱物制备TiO2负载Fe3+多相催化剂Fe/TIO-P25,研究Fe/TIO-P25可见光催化H2O2降解扑草净的协同效应.XRD、XPS、EDS及SEM结果表明,Fe元素以Fe2O3形式高度分散于TiO2表面,负载量约1.5%(wt%),未对TIO-P25的粒径及形貌产生明显影响,Fe/TIO-P25的粒径约20~40nm;光催化结果表明,Fe/TIO-P25能可见光催化H2O2降解扑草净,反应30min降解率达100%,远大于TIO-P25的催化活性,负载Fe与TIO-P25之间存在明显的协同效应;通过对反应体系的荧光光谱分析显示,扑草净的降解涉及较单纯羟基自由基(·OH)过程更为复杂的反应机理.     

光热光电驱动的海岛型太阳能海水淡化装置研制与性能分析

针对偏远海岛淡水资源和常规能源缺乏问题,综合利用光热与光伏驱动,通过技术设计、数学计算、传热传质、模拟测试、性能分析等程序研制一种适用于海岛的太阳能海水淡化装置。并在光热模式、光热光伏模式、电加热模式下测试了装置的性能。实验结果表明:1）淡化装置在光热模式下的平均产水速率为225 mL/h,在光热光伏模式下的平均产水速率为332 mL/h,比光热模式提高了47.6%,而电加热模式平均产水速率可达到1910 mL/h,反映了中高温太阳能集热管的重要性;2）淡化装置的最佳实验条件为:蒸发舱温度为103℃,冷却水温度为41℃,环境温度为30℃,在此条件下的瞬时产水量高达2389 mL/h,各因素的影响程度顺序为蒸发舱温度>冷却水温度>环境温度;3）淡化装置在光热和光热光伏模式下的单位面积产水量分别为2172,1167 mL/（m2·d）,太阳能蒸馏过程的最小热耗为2.03 kW·h/m3。     

新型三维多孔光热材料制备及其高盐废水处理应用

高盐废水处理存在处理难度大和能耗成本高等问题.近年来发展的界面光蒸汽水处理技术以绿色、高效和低能耗等特点成为了目前水资源回收利用领域的研究热点.本研究以纤维状结构的碳化氮（h-CN）修饰石墨烯（r-GO）,通过水热反应制备了新型三维多孔石墨烯复合材料（3D h-CN/r-GO）,并以硝基苯和苯酚作为模拟污染物,考察了其光热蒸发处理高盐废水的性能.研究结果表明,所制备的3D h-CN/r-GO材料具备宽光谱吸收范围和多级孔道结构,并呈现出快速热响应的特点.在模拟太阳光照条件下,光蒸汽转化效率可达90.4%.并且在处理过程中可实现硝基苯和苯酚等常见挥发性污染物的吸附,其吸附容量分别为67.6 mg·g^-1和57.5 mg·g^-1.而且,3D h-CN/r-GO可实现长时间稳定的光热水体蒸发回收,且对污染物及盐分截留率高达98%左右,冷凝水体达到污水处理的排放标准.因此,本研究为高盐废水的低能耗和低成本处理提供了一种新的技术.     

O3/UV降解水中的乙酸和硝基苯

利用O3 /UV和O3/H2O2降解了水中的乙酸,结果表明,在相同条件下处理60min后,O3/UV对乙酸的去除率仅比单独臭氧化处理提高了3%,而O3/H2O2在此条件下完全降解乙酸.O3/UV在处理硝基苯过程中却显示较好的氧化降解能力,通过分析表明,硝基苯降解过程中所产生的副产物H2O2对有机物的去除具有很重要的作用.因此,O3/UV氧化降解能力的提高可能有2方面的原因,紫外光对有机物的活化作用;中间产物H2O2催化臭氧分解产生了高活性的羟基自由基. 单独紫外光催化臭氧分解产生羟基自由基的效率极低.     

小球藻来源溶解有机质的光化学降解特性

利用三维荧光光谱-平行因子分析(EEM-PARAFAC)手段结合吸收光谱分析,研究了小球藻指数期和稳定期培养液中溶解有机物(DOM)在秋季天然太阳辐射作用下的光降解动力学特征.结果表明,小球藻生长过程中除能产生短波激发类腐殖质组分C1(其荧光峰的激发/发射波长位置为240,335 nm /406 nm)及类蛋白质组分C3(225,275 nm/334 nm)外,还会形成长波激发类腐殖质组分C2(260,395 nm /502 nm),表明C2组分并非仅有传统认为的陆源属性,同时也具有自生源属性.稳定期培养液的吸收光谱在250~300 nm范围内出现的肩峰,可用于指示水环境中现场自生源的贡献.不同生长时期培养液中DOM的吸收系数和荧光组分的降解动力学都符合一级反应方程.稳定期类腐殖质荧光组分(C1和C2)的光降解程度略高于指数期,但指数期类色氨酸组分(C3)的光降解程度略高于稳定期.经太阳辐照6 d后,小球藻培养液的吸收系数a₃₅₀及各荧光组分的平均损失率分别达到83.0%、84.0%、64.8%和80.0%,对应的半衰期只有1.6~5.0 d,揭示出藻类自生来源的DOM具有很强的光化学降解活性.     

南京冬季晴天及雾-霾天气纳米气溶胶粒子谱日变化比较

利用2017年12月南京气溶胶数浓度与气象参数资料,比较研究晴天及雾-霾天中10~1000nm纳米气溶胶粒子谱日变化规律及差异特征.结果表明,单峰谱型出现与污染加重有明显关系,分别出现在晴天午后、霾严重污染阶段和污染消散阶段、浓雾过程,峰值粒径分别为晴天（20~100nm）、霾天（27~144nm）和雾天（34~122nm）.3种天气条件下,晴天较强的太阳辐射和较低的湿度适合小粒子生成,核模态占比在晴天最高;霾天气象场适合爱根态粒子大量稳定存在,爱根态占比在霾天最高;雾天大量气溶胶吸湿增长,导致积聚态占比在雾天最高.在霾天污染物累积阶段,大量积聚态粒子对核模态、爱根态粒子的碰并增长作用抑制核模态、爱根态粒子生成,核模态和爱根态粒子浓度变化率为-91.0%和-62.5%,而积聚态为89.7%.浓雾过程对爱根态粒子清除作用最明显.     

An epicuticular multilayer reflector generates the iridescent coloration in chrysidid wasps (Hymenoptera, Chrysididae)

Chrysidid wasps in the subfamily Chrysidinae are brood parasitoids or cleptoparasites of other insects and famous for their cuticular iridescence. In this study, we examine the dorsal abdominal cuticle of the chrysidid wasp Hedychrum rutilans to identify the underlying color mechanism. Using scanning electron microscopy, reflectance spectral analysis, and theoretical calculations, we demonstrate the presence of an epicuticular multilayer reflector consisting of six lamellae with a thickness of 185 nm each. The lamellae exhibit a rough surface probably functioning as spacers between the individual layers. The reflector has a measured reflectance maximum at λ = 630 nm, i.e., in the red part of the visible spectrum of light at normal incidence and the reflectance maximum shifts to green as the angle of incidence increases. Complementary theoretical modeling corroborates the view that the epicuticular multilayer generates the iridescent color of the chrysidid cuticle. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

京津冀及周边民用散煤燃烧控制对北京市PM2.5的影响

为评估京津冀及周边“2+26”城市农村居民面源污染控制成效,揭示其对北京市秋冬季重污染天气PM_2.5污染的改善作用,及其对PM_2.5组分硫酸盐形成机制的影响,采用空气质量模型对北京市2018—2019年秋冬季5次重污染事件进行了模拟. 结果表明:①在“2+26”城市平原地区民用散煤削减90%的控制情景下,区域PM_2.5浓度最大值由324 μg/m3降至251 μg/m3,下降了23%. 北京市城区PM_2.5浓度由139 μg/m3降至124 μg/m3,下降了11%;同时,北京市城区SO₂、硫酸盐浓度分别降至6.2、14.9 μg/m3,分别下降了45%、24%. ②农村居民面源污染控制前北京市硫酸盐浓度的正贡献来源主要受水平平流输送过程影响,控制后水平平流输送过程仍起主导作用,但该过程在水平平流输送、垂直平流输送、水平扩散、垂直扩散这4个物理过程中的绝对重要性上升了2%;此外,农村居民面源污染控制后垂直扩散清除过程对硫酸盐浓度的贡献下降了33%,气溶胶二次转化过程的贡献下降了25%,但SO₂向硫酸盐转化的速率加快,其小时转化率上升了1.44%. ③ISAM源解析方法结果表明,控制情景下区域工业过程是影响北京市SO₂浓度的最主要行业源因素,平均贡献率为65%,硫酸盐工业过程源的平均贡献率为82%. 区域来源分析表明,北京市SO₂来源主要为外地源输送,硫酸盐主要来源与SO₂一致,其中河北省贡献较大,其对SO₂、硫酸盐的平均贡献率分别达43%、40%. 研究显示,控制情景下污染期间北京市PM_2.5污染改善,且污染物浓度、形成过程和来源贡献均发生明显变化.      

Temporal variability of iron concentrations and fractions in wetland waters in Sanjiang Plain, Northeast China

Chemical forms, reactivities and transformation of iron fractions in marshy waters were investigated with cross-flow filtration technique to study the iron environmental behavior. Iron fractions were divided into four parts: acid-labile iron (pre-acidification of unfiltered marshy water samples, 0.7 μm), high-molecular-weight iron (0.7-0.05 μm), medium-molecular-weight iron (0.05-0.01 μm), and low-molecular-weight iron ( 0.01 μm). The cross-flow filtration suggested that iron primarily exist in both the 0.7 μm and 0.01 μm size fractions in marshy waters. Rainfall is the key for rain-fed wetland to determine fate of iron by changing the aquatic biochemical conditions. By monitoring the variation of iron concentrations and fractions over three years, it was found that dissolved iron and acid-labile iron concentrations exhibit a large variation extent under different annual rainfalls from 2006 to 2008. The seasonal variation for iron species proved that the surface temperature could control some conversion reactions of iron in marshy waters. Low- molecular-weight iron would convert to acid-labile iron gradually with temperature decreasing. The photochemical reactions of iron fractions, especially low-molecular-weight iron had occurred under solar irradiation. The relative proportion of low-molecular-weight in total dissolved iron ranging from 28.3% to 43.2% were found during the day time, which proved that the observed decreasing concentration of acid lability iron was caused by its degradation to low molecular weight iron.     

复合材料太阳翼基板声学疲劳特性研究

研究航天器在声激励下的疲劳行为及其演变规律,对证航天器的运行安全。针对碳纤维蒙皮-铝蜂窝的太阳翼基板声致疲劳问题,使用耦合FE/BEM方法,建立航天器太阳翼基板的数值分析模型,以声学试验结果为依据,对仿真模型进行验证。噪声激励持续作用60 s后,损伤率分布呈沿结构长轴对称状态,疲劳危险点处最大损伤率D=0.0232,太阳翼基板未出现疲劳破坏,最短疲劳寿命T=2.58×103s。太阳翼基板中心区域为结构设计薄弱处,该区域在多阶模态下的应力水平较高,疲劳寿命较短,极易导致疲劳破坏。     

Start-up of the anammox process from the conventional activated sludge in a hybrid bioreactor

The anaerobic ammonium oxidation (anammox) process was successfully started up from conventional activated sludge using a hybrid bioreactor within 2 months. The average removal efficiencies of ammonia and nitrite were both over 80%, and the maximum total nitrogen removal rate of 1.85 kg N/(m³.day) was obtained on day 362 with the initial sludge concentration of 0.7 g mixed liquor suspended solids (MLSS)/L. Scanning electron microscope (SEM) observation of the granular sludge in the hybrid reactor clearly showed a high degree of compactness and cell sphericity, and the cell size was quite uniform. Transmission electron microscope photos showed that cells were round or oval, the cellular diameter was 0.6--1.0 μupm, and the percentage of the anammoxosome compartment was 51%--85% of the whole cell volume. Fluorescence in situ hybridization analysis (FISH) indicated that anammox bacteria became the dominant population in the community (accounting for more than 51% of total bacteria on day 250). Seven planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass and affiliated to Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia sp., a new anammox species. In addition, the average effluent suspended solid (MLSS) concentrations of outlets I (above the non-woven carrier) and II (below the non-woven carrier) were 0.0009 and 0.0035 g/L, respectively. This showed that the non-woven carrier could catch the biomass effectively, which increased biomass and improved the nitrogen removal rate in the reactor.     

类单晶纳米片状WO3的制备及其光催化性能

通过调控水热温度、反应pH值和前驱体比例制备了类单晶WO₃纳米片光催化材料,通过XRD,SEM,TEM,XPS,UV-vis和光电流密度测试等手段对WO₃纳米片的形貌、晶型、组成以及电荷分离性能进行了表征,并研究了可见光照条件下其对罗丹明B的催化降解活性.结果表明,研究获得了厚度约10nm,边长尺寸约300~500nm的单斜晶相WO₃纳米片,且纳米片具有连续整齐的晶格结构、较高的能带结构和较好的电荷载流子分离性能.光催化实验结果表明,WO₃纳米片催化降解罗丹明B的反应过程符合一级动力学,反应速率常数为2.91h^-1,是WO₃纳米颗粒催化罗丹明B降解反应速率常数（0.56h^-1）的5.2倍,推测WO₃纳米片较好的催化活性是源于其较高的载流子分离效率.自由基捕获实验证明,可见光照下·OH和·O₂^-均为WO₃纳米片催化降解污染物过程中的活性自由基.循环降解实验证明制备的光催化剂具有良好的稳定性.     

石家庄市冬季一次重污染过程分析与反馈效应研究

为深入探究高ρ（PM_2.5）地区重污染过程的发展变化规律,以石家庄市一次重污染过程（2017年1月13-20日）为例,结合空气质量监测数据、PM_2.5组分测试数据、气象观测资料,从重污染发展阶段（简称"P1阶段"）、维持阶段（简称"P2阶段"）和清除阶段（简称"P3阶段"）分析PM_2.5及其化学组分的变化特征、气象条件和高低空天气形势演变特征,并利用WRF-Chem模型定量研究重污染过程气溶胶反馈效应对典型气象要素的影响.结果表明:①此次重污染过程属于逐步累积增长、快速清除型,在P2阶段ρ（PM_2.5）平均值为241.0 μg/m3,最大值为367.5 μg/m3.②P1和P2阶段高低空大气环流配置稳定,大气边界层高度范围为620.6~712.2 m,风速范围为1.3~2.5 m/s,相对湿度范围为60%~80%.③P2阶段SOR（硫氧化率）和NOR（氮氧化率）均为0.3,ρ（SNA）（SNA为SO₄2-、NO₃-和NH₄+的统称）为128.8 μg/m3,占ρ（PM_2.5）的56.2%;OM[有机质,ρ（OM）=ρ（POA）+ρ（SOA）,其中,POA为一次有机气溶胶,SOA为二次有机气溶胶]是除SNA以外的第二大组分,在P1和P3阶段ρ（POA）大于ρ（SOA）,而在P2阶段ρ（SOA）与ρ（POA）相等,均为28.0 μg/m3,表明在重污染过程中二次污染严重;整个污染过程ρ（NO₃-）/ρ（SO₄2-）为1.0,表明石家庄市移动源和固定源对ρ（PM_2.5）贡献相当.④WRF-Chem模型模拟结果表明,太阳辐射量、温度和大气边界层高度受气溶胶反馈效应的影响在P2阶段的下降量分别为75.1 W/m2、2.7℃和109.9 m,比P1阶段分别高33.6%、91.4%和18.6%,比P3阶段分别高147.0%、305.3%和24.1%.研究显示,此次静稳天气下的重污染过程二次污染严重,气溶胶反馈效应整体使得太阳辐射量、温度和大气边界层高度均向不利于污染扩散的趋势发展,造成石家庄市的ρ（PM_2.5）进一步增加.      

Photocatalytic degradation of the dye sulforhodamine-B： A comparative study of different light sources

The photocatalytic degradation of dye pollutant sulforhodamine-B （SRB） in aqueous titanium dioxide （TiO2） dispersions was examined under three lighting regimes： UV light （330 nm〈λ〈 380 nm）, sunlight, and visible light （λ〉450 nm）, all investigated at pH=2.5. Total organic carbon （TOC） and chemical oxygen demand （CODer） assays show that the degradation rate of SRB is much higher when irradiated with UV and sunlight compared with visible light. The temporal concentration changes of SRB illustrated a first-order reaction and the rate constant, k, is 0.197 min^-1, 0.152 min^-1, 0.027 min^-1, respectively, under the three lighting conditions. The final mineralized products were amine compounds identified by infrared spectrophotometry. When irradiated with visible light, the photocatalytic degradation rate could be improved by lowering the H2O2 concentration and inhibited by increasing the H2O2 concentration, but results contrary to the above were obtained when UV light was used for irradiation.     

基于端到端深度学习的有机光伏材料光电转化效率预测

碳中和背景下,亟需开发高效清洁的新型能源,以减少对化石能源的依赖。有机光伏材料作为一种可将太阳能或其他光能直接转化为电能的材料,日益成为一种具有重大应用前景的低碳能源材料。在探索新的高性能有机光伏材料的过程中,机器学习虽然能够提高材料设计效率,但其预测能力极大受制于描述符的开发和选取。利用循环神经网络、卷积神经网络、图神经网络等算法,构建端到端的深度学习模型预测有机光伏材料光电转化效率,所建模型可直接从SMILES符号、分子图像、分子图网络中提取化合物结构信息,而无须人为开发和选取描述符。所得模型不仅能够较为准确地预测有机光伏材料的光电转化效率(其中最优模型五折交叉验证结果和测试集预测结果决定系数均>0.73),而且能够识别影响转化效率的关键结构特征。该研究结果可为新型环境功能材料设计提供理论参考。     

Renewable energy powered evacuated tube collector refrigerator system

This article presents a numerical study of an Evacuated Tube Collector (ETC) based Ammonia-Water absorption refrigeration system. This system utilizes solar energy as an energy source and does not depend on conventional energy sources for its operation. The present system involves the use of hot water as an energy carrier for generator in an absorption system. The analysis system is based on computational model being developed and the thermodynamic properties of working fluids have been used from the computer code. The variation of performance parameters such as heat load of different components, exergy loss, COP_COOLING, COP_HEATING and Exergy efficiency are studied with varying generator temperature. The results indicate that COP_COOLING as well COP_HEATING lies in the range of 0.012–0.498 and 1.012–1.498 respectively and the values obtained are based on the maximum available solar intensity of 0.9 kW/m² which corresponds to the collector area of about 431.7 m² and hot water in the range of 90 °C. It is concluded that the maximum exergy loss is in generator and it is lowest in condenser. The ETC based absorption refrigeration system can be powered by renewable energy sources and does not employ ozone depleting substances.     

Production of ammonia from plasma-catalytic decomposition of urea: Effects of carrier gas composition

Effects of carrier gas composition(N_2/air) on NH_3 production, energy efficiency regarding NH_3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an Al_2 O_3-packed dielectric barrier discharge(DBD) reactor at room temperature. Results show that the presence of O_2 in the carrier gas accelerates the conversion of urea but leads to less generation of NH_3. The final yield of NH_3 in the gas phase decreased from 70.5%, 78.7%, 66.6% and 67.2% to 54.1%, 51.7%, 49.6% and 53.4% for applied voltages of 17, 19, 21 and 23 kV, respectively when air was used as the carrier gas instead of N_2.From the viewpoint of energy savings, however, air carrier gas is better than N_2 due to reduced energy consumption and increased energy efficiency for decomposition of a fixed amount of urea. Carrier gas composition has little influence on the major decomposition pathways of urea under the synergetic effects of plasma and Al_2 O_3 catalyst to give NH_3 and CO_2 as the main products. Compared to a small amount of N_2 O formed with N_2 as the carrier gas, however,more byproducts including N_2O and NO_2 in the gas phase and NH_4 NO_3 in solid deposits were produced with air as the carrier gas, probably due to the unproductive consumption of NH_3, the possible intermediate HNCO and even urea by the abundant active oxygen species and nitrogen oxides generated in air-DBD plasma.