Light-induced changes in the solar cell parameters and temperature coefficient of n-C/p-Si heterojunction solar cell

Amorphous carbon (a-C) is a potential material for the development of low-cost and high-efficiency solar cell. We report the study of the influence of light soaking up to 100 h on n-C/p-Si heterojunction solar cell. It is observed that the deterioration in the fill factor and the efficiency are significantly smaller as compared to that observed in a-Si:H solar cell. Variations in the temperature coefficients of the I–V characteristics subjected to light degradation and recovery has also been investigated. A good correlation between change in the temperature coefficient and the degradation/recovery state of cell's conversion efficiency has been observed.     

循环悬浮式烟气半干法脱硫技术的实验研究

建立了烟气处理量1500Nm^3／h的中试试验台，对循环悬浮式半干法烟气脱硫工艺进行了实验研究。研究了运行参数（包括烟气在吸收塔内的停留时间，Ca／S，绝热饱和温距，浆滴粒径，入口二氧化硫浓度，入口烟温等），脱硫灰再循环等因素对脱硫塔内和整个系统脱硫效率的影响。研究结果表明运行参数中绝热饱和温距、钙硫比以及浆滴粒径的变化对系统脱硫效率的影响明显，循环灰的增加有利于提高脱硫效率。图18表2参9     

A simple approach to determine the solar cell diode ideality factor under illumination

A simple approach, which can estimate the diode ideality factor of a high efficiency pn junction solar cell under illumination by using its current-voltage data, is explained. We have proposed that an analytical method based on Lambert W-function is sufficient for the extraction of the diode ideality factor of a solar cell modeled by double junction behavior with considerable compliance. Various illumination intensities are also considered in order to specify the reliable limit of the method. The dependence of the ideality factor and the reverse saturation current with light intensity has also been investigated in order to provide insight into the alteration of electrical conduction at junction interface at room temperature.     

Light induced degradation in nanocrystalline Si films and related solar cells: Role of crystalline fraction

Silicon thin films with different crystalline volume fractions have been deposited at different power and pressure conditions. Structural properties of the films have been investigated. The effects of crystalline volume fractions and grain sizes on the degradation of photoconductivity have been studied. Single-junction solar cells have been fabricated with protocrystalline and nanocrystalline Si as absorber layer. Protocrystalline silicon solar cells show less than 1% degradation upto 50 h of light soaking. Then the cells degrade upto 500 h and thereafter become steady. Nanocrystalline solar cells show degradation initially and become steady after 10 h of light soaking. Using protocrystalline silicon as absorber layer the solar cell efficiency degrades 9% before stabilization, whereas using nanocrystalline silicon as absorber layer (X_c～65%) the solar cell efficiency degrades 2.9%. Stabilized efficiency of the second type of cell is better than that of the first cell, but initial efficiency is higher for the first cell (η=7.1%).     

Influence of temperature and electrolyte saturation on rate and efficiency of oxygen cycle in VRLAB

The paper discloses the influence of the temperature and electrolyte saturation of the active block (positive and negative plates and AGM separator) on the rate and efficiency of the oxygen cycle (OC) in valve-regulated lead-acid batteries (VRLAB).Applying steady-state cyclic linear sweep voltammetry and measuring the gas flow leaving the cell, the rate and efficiency of OC were measured at constant temperature and electrolyte saturation as a function of the negative plate potential. The obtained results show that at constant potential of the negative plate the rate of the OC depends slightly on temperature. However, the efficiency of the OC strongly depends on the temperature—the higher the temperature, the lower the OC efficiency.The experimental results for the influence of the electrolyte saturation on the rate and efficiency of the oxygen cycle show that the saturation is the main rate- and efficiency-limiting factor. Combining the gas diffusion approach, porosimetric analysis of the NAM and AGM separator and the recently proposed model of the reactions that take place during the operation of OC, the mechanism of the influence of the electrolyte saturation on the rate and efficiency of the oxygen cycle was elucidated. It was shown that the optimal saturation value is about 93%.     

Changes in the temperature coefficients of the characteristics of amorphous silicon solar cells subjected to light degradation and recovery

Measuring changes in temperature coefficients is an effective way to estimate the performance of a solar cell. We investigated changes in the temperature coefficients of the I–V characteristics of amorphous silicon (a-Si) solar cells subjected to light degradation and recovery. There is a good correlation between change in the temperature coefficient (Ψ) and the degradation/recovery state of a cell’s conversion efficiency (η). This relationship can be expressed by Ψ_η=−0.0052Δη−0.45. Therefore, the temperature coefficient corresponding to the degradation/recovery state can be estimated.     

Accelerated degradation in amorphous silicon solar cells by a combination of current injection and light insolation

A new degradation technique for amorphous silicon solar cells comprising of a combination of current injection and insolation has been developed. Compared to the conventional light degradation technique, current-induced degradation which involves forward biased current stress, results in a lower stabilized cell parameters including efficiency. This stabilized efficiency is, however, independent of the amount of current injected. The excess degradation is recovered under light illumination. The stabilized value of the conversion efficiency is within experimental error identical to that observed in long term, illumination only degradation. The method is fast, accurate and reliable. Its reliability has also been tested for single junction solar cells having intrinsic layers of different band gaps, as well.     

Pool boiling characteristics of nano-fluids

Common fluids with particles of the order of nanometers in size are termed as ‘nano-fluids’ which have created considerable interest in recent times for their improved heat transfer capabilities. With very small volume fraction of such particles the thermal conductivity and convective heat transfer capability of these suspensions are significantly enhanced without the problems encountered in common slurries such as clogging, erosion, sedimentation and increase in pressure drop. This naturally brings out the question whether such fluids can be used for two phase applications or in other words phase change in such suspensions will be assistant or detrimental to the process of heat transfer. The present paper investigates into this question through experimental study of pool boiling in water-Al₂O₃ nano-fluids. The results indicate that the nano-particles have pronounced and significant influence on the boiling process deteriorating the boiling characteristics of the fluid. It has been observed that with increasing particle concentration, the degradation in boiling performance takes place which increases the heating surface temperature. This indicates that the role of transient conduction in pool boiling is overshadowed by some other effect. Since the particles under consideration are one to two orders of magnitude smaller than the surface roughness it was concluded that the change of surface characteristics during boiling due to trapped particles on the surface is the cause for the shift of the boiling characteristics in the negative direction. The results serve as a guidance for the design of cooling systems with nano-fluids where an overheating may occur if saturation temperature is attained. It also indicates the possibility of such engineered fluids to be used in material processing or heat treatment applications where a higher pre-assigned surface temperature is required to be maintained without changing the fluid temperature.     

Role of buffer layer at the p/i interface on the stabilized efficiency of a-Si solar cells

Light induced degradation of single junction and double junction a-Si:H solar cells has been studied. Cells with and without buffer layers at the p/i interfaces have been fabricated. It is found that light induced degradation is faster in the cells with buffer layers. Defect density increases faster and degraded efficiency with respect to the initial efficiency decreases at a higher rate for the cells with buffer layers. Spectral response study for double junction cells shows that collection efficiency decreases for the bottom cell only. So it is found that the absolute stabilized efficiency is highest for a double junction cell with buffer layer at the top cell only.     

Combination effect of ZnO and activated carbon for solar assisted photocatalytic degradation of Direct Blue 53

The degradation efficiency of AC–ZnO composite photocatalyst was evaluated with solar light using an azo dye Direct blue 53 (DB53) at room temperature. Activity measurements performed under solar radiation have shown good results for the photodegradation of DB53. The synergistic effect observed was ascribed to an extended adsorption of DB53 on activated carbon followed by its transfer to ZnO where it was photocatalytically degraded. The enhanced photocatalytic activity of AC–ZnO when compared to ZnO is found to be due to this synergistic effect. A study on the effects of various parameters like concentration of dye, amount of catalyst and initial pH on the photodegradation of DB53 has been carried out to find optimum conditions.     

透明隔热膜对改善光伏组件温度和发电效率的研究

针对太阳光中的近红外光导致光伏组件温升,进而影响光伏组件发电效率的问题,开展了透明隔热膜在降低组件温度并提高发电效率方面的研究。首先,纳米氧化锡锑(ATO)透明隔热膜具有反射红外光,透射可见光的特点。基于此特点,在实验室将自制的纳米ATO隔热涂料涂布在光伏组件专用玻璃上,在分光光度计下检测样品的可见光、近红外光透过率;其次,分别在太阳能模拟器、室外日光下测试隔热性能以及光伏组件的功率特性。实验测试结果表明:实验室自制的纳米ATO透明隔热膜可有效降低光伏组件的工作温度,从而提高其发电效率和使用寿命。     

Structure optimization and damage behaviour of heat-resistant CrMoV tube steels

The heat treatment of a heat-resistant tube steel 12 CrMoV 4 3 has been optimized in relation to its long-term creep resistance. The influence of initial structure and of stress, time and strain on the formation of creep cavities has been determined.

Cooling rates from the austenitizing temperature and tempering conditions were varied during heat treatment. It has been demonstrated that, with an increasing cooling rate down from the austenitizing temperature, the structure tends towards a more finely dispersed precipitation of VCN with formation of grain boundary carbides as well as a higher dislocation density.

The optimum tempering conditions are for 2 h at 725°C. Longer times or higher temperatures lead to degradation of the structure. Creep rupture tests show that a clear influence of the structure on the secondary creep rate and rupture time exists. Both pore size distribution and pore density in the specimen surface are strain- and time-dependent. An influence of stress could not be detected. Pore density in the surface approaches, with increasing strain, a saturation value. This saturation value depends on the initial structure and is related to rupture strain.     

Visual experiment research of the inhaled particle thermophoresis deposition rule in the rectangle turbulent flow tube

In order to solve the problem of removing inhaled particle caused by the combustion source, the dynamics characteristics of the inhaled particle in additional temperature field have to be studied. The dynamics characteristics of the inhaled particle in temperature field are measured in designed and processed a rectangle experiment channel by the PDA instrument. This method is visual. The dynamic characteristic of the particle at 0.15 mm near by water wall surface in boundary layer can be measured through the direction change of beam of PDA light. The movement rules of the inhaled particle in the additional temperature field are obtained through the experiment. The experiment results show that the thermophoresis force has strong influence on the particle which diameter is about 6 μm and the experience formulas are put forward to calculate the thermophoresis deposition efficiency. The thermophoresis deposition efficiency formulas obtained from this experiment is consistent with Batchelor and Shen formulas. The research shows that the PM_2.5 thermophoresis deposition efficiency is direct proportion to the temperature ratio between the inlet temperature and the water wall surface but is not the temperature difference in the rectangle channel.     

Methods for determining the intermediate-axis saturation Characteristics of salient-pole synchronous Machines from the measured D-axis Characteristics

In the analysis of the steady-state performances of saturated synchronous machines using the classical two-axis (d- and q-axis) frame model, the accurate calculation of the machine performances depends to a large extent on their saturation conditions. However, the effect of saturation depends not only on the saturation level in the axis of the resultant machine ampere-turns (intermediate-axis) but also on the phase angle between the resultant ampere-turns and the resultant magnetic flux. This work presents four analytical methods for determining the intermediate-axis saturation characteristics of salient-pole synchronous machines from the measured d-axis saturation characteristics. The accuracies of these four methods have been verified by comparing the measured field currents and load angles of two laboratory salient-pole synchronous machines of different designs with those calculated using an innovated approach which uses the intermediate-axis saturation characteristics directly in the modeling of the saturated synchronous machines. Moreover, the calculated intermediate-axis saturation characteristics have been compared with the measurable ones in the case of one of these machines.     

Photocatalytic reduction of carbon tetrachloride by natural sphalerite under visible light irradiation

The photoreductive degradation of carbon tetrachloride (CT) in natural sphalerite ((Zn, Fe)S mineral) suspensions irradiated by visible light (VL) is studied in this paper. 92% of CT is degraded in N,N-dimethylformamide (DMF) organic solvent system after 8 h of VL irradiation. The effects of light source, sphalerite dosage, electron donors, dissolved oxygen and CT initial concentration on CT photocatalytic degradation efficiency are discussed. The degradation products are analyzed by gas chromatography-mass spectrometry (GC-MS), and the photocatalytic degradation mechanism is then proposed.     

Photovoltaic cell characteristics for high-intensity laser light

The series resistance value of a photovoltaic (PV) cell required for high-intensity light and the effects of both the α parameter (the ratio of the open-circuit voltage to the bandgap) and temperature on conversion efficiency are investigated by a calculation method derived from the fundamental characteristics of PV cell. The PV cell characteristics for high-intensity laser light, including Si, GaAs, InGaAs PV cells and InGaAs uni-traveling-carrier photodiode (UTC-PD), are experimentally investigated. The small series resistance as large as 20–30 μΩ cm² and the suppression of recombination are important for obtaining higher conversion efficiency, especially for high-intensity laser light.     

Current-induced degradation method for stabilization of a-Si solar cell

Light-induced degradation and light-induced degradation after current-induced degradation of several types of a-Si solar cells were compared in order to investigate the difference between current-induced degradation and light-induced degradation. Very little difference in the efficiency after long-term light irradiation is observed between samples which were degraded by light- after current-induced degradation and those which were degraded by light only. Little difference in the collection efficiency spectra and the depth profiles of the DICE (dynamic inner collection efficiency) is also observed between the cells degraded by these two processes. The possibility of applying the current-induced degradation method to the stabilization of a-Si solar modules is indicated.     

Effect of light-induced metastable defects on photocarrier lifetime

Creation and annealing of light-induced defects and their effect on photocarrier lifetime have been studied at 120 and 300 K using constant photocurrent method (CPM) and steady-state photoconductivity measurements. A hysteresis-like relation is observed between photoconductivity and light-induced defect density. This relation depends on both degradation temperature and light intensity used for the degradation. A broad, resembling a two-component distribution of defect annealing activation energies together with distribution of recombination coefficients account for the observed changes at 120 K. On the other hand, these distributions are narrower and sharply peaked at about 1 eV for the 300 K measurements. Results indicate that defects which are created at the earlier stages of the illumination have smaller annealing activation energies and higher recombination coefficient (capture cross-section) and these are better recombination centers than the defects with higher annealing activation energies.     

Degradation and annealing of amorphous silicon solar cells by current injection: experiment and modeling

In this paper we report in detail on the effect of current injection in amorphous silicon solar cells. A set of devices has been degraded and then annealed at different current intensities. Device performances during the whole experiment have been monitored by current–voltage characteristics and quantum efficiency curves. It has been found that annealing rate increases with current intensity, while stabilized photovoltaic parameters decrease. Time evolution of efficiency and short-circuit current during degradation has been reproduced by a numerical device modeling, resulting in a pronounced increase of defects near the p–i interface. The model also demonstrated that annealing results are not well reproduced if current-induced annealing is not energy selective.     

Three-year performance and reliability analysis of a 4 kW amorphous-silicon photovoltaic system in Michigan

A 4 kW photovoltaic (PV) power system composed of 144 Sovonics R100 amorphous-silicon alloy modules was constructed in southeastern Michigan in early 1987. During more than three years of continuous operation, the system and its components have been reliable and durable. Analysis of array performance has shown initial degradation, followed by stabilization. Cyclic efficiency variations have been found to be related to solar spectrum, ambient temperature and past history of temperature.