Dynamic multiphysics model for solar array

An approach to model the solar cell system with coupled multiphysics equations (photovoltaic, electro-thermal, direct heating and cooling processes) within the context of the resistive-companion method in the Virtual Test Bed computational environment is presented.. Appropriate across and through variables are defined for the thermal terminal of the system so that temperature is properly represented as a state variable, rather than as a parameter of the system. This allows enforcement of the system power conservation through all terminals, and allows simultaneous solutions for both the electrical potentials and the system temperature. The thermal port built accordingly can be used for natural thermal coupling. The static and dynamic behaviors of the solar array model based on the approach are obtained and validated through comparison of simulation results to theoretical predictions and other reported data. The electro-thermal modeling method developed here can be generally used in the modeling of other devices, and the method to define the across and through variables can also be generalized to any other interdisciplinary processes where natural coupling is required     

A commercial solar cell array design

Solar cell arrays designed for space use are not suitable for terrestrial electric power generation applications. The environment on Earth is much different and the commercial price range for these applications is much lower than that for space applications. This paper describes solar cell array designs that provide protection from the terrestrial environment and at the same time bring the array price down from about $100 per watt (space design price) to about $25 per watt. Optical efficiency of the concentrator design is 76 per cent. The thermal characteristics of the arrays have been measured and electrical performance data is presented.     

A solar furnace using a horizontal heliostat array

A two-component solar furnace, condenser-heliostat combination, is described in which the condenser faces downward at 30° towards a heliostat comprised of numerous rows of plane mirrors mounted on a horizontal turntable. It is shown that for a south-facing condenser, with the angle of the final flux beam limited to 30° below the horizontal, the rows of heliostat mirrors may be mounted so they overlap, resulting in a reduction of the edge losses occurring when the heliostat mirrors are all held in a single plane. The over-all size of the heliostat turntable is calculated for a 6-hour workday throughout the year, and a suggestion is made for using the heliostat control mechanism to provide shutter action. The saving in flux possible by the elimination of an independent shutter is estimated at about eight per cent.     

光伏方阵支撑架抗风研究

根据当地基本风压,精确计算光伏方阵与撑架各连接点螺栓和支架所受的拉力、挤压力和剪切力。结合流体力学,设计最佳的方阵内部排风间隙,可以降低整个方阵所受的风荷载,从而优化方阵支撑架的设计,降低投资。     

The mini-flasher: a solar array test system

The mini-flasher has been developed to provide a simple and mobile instrument to control solar array basic functionality and use comparative measurements to detect damages. The paper recalls the technological evolution which led to flashers or LAPSS, their complexity, and their accuracy which was countered by loss in operational flexibility. The mini-flasher principles of operation are briefly given as well as a summary of the user manual and an example of the result. Although the system was developed in the spacecraft technology environment, its mobility probably makes it a useful tool for the field verification of terrestrial solar arrays performance.     

Photovoltaic solar cell array used for supplemental power generation

A study of the performance of a silicon cell non-tracking photovoltaic array has been made over a three year period. The array provided power in parallel with commercial utility power in a shared mode which makes use of all the solar energy generated. Tests of degradation, dirt accumulation, compatability with telephone plant, and day by day performance were performed. A method is developed for predicting the energy output of a non-tracking array based on standard global insolation measurements.     

Experimental investigation of concentrated solar air-heater with internal multiple-fin array

This paper presents the results of experimental validation of energy conversion in a concentrated solar air-heater with internal multiple-fin array. A novel high temperature solar air heater was proposed to convert solar energy to heat for space heating in climatic conditions of Poland.The aim of the study was to verify the previously created mathematical model of heat transfer processes. The collector’s performance was analysed experimentally against the reduced temperature difference. During the experiments, an electrical air heater was used to change the air temperature at the inlet of the receiver according to the test demands. Additionally, two daily performance evaluation tests were done. During the tests the all-day measured data was collected automatically and recorded at 1-min intervals. Hourly and daily thermal efficiency was calculated. Validation of the model showed its correctness and proved that the model can be accepted.     

真空太阳集热管阵列反射器设计

真空管太阳集热器（管阵列）是太阳热水器集热与传热的重要部分,设计的好坏将对热水器的热效率、产水量、生产成本产生直接影响。由于真空集热管成本较高,若采用密排,不仅单位面积成本太高,而且与连集管的联结存在技术困难,背向太阳的吸热面也得不到利用。因此,一般采用间隔一定距离排列,背面采用反射器,以利用管间空隙进入的阳光。反射器的设计在于使吸热管尽可能多地吸收反射光线。图１所示是一些较为常见的反射器,既有简单的,也有复杂的,需要根据所要求的运行温度、经济性等选用。吸热管对进入管空间的太阳辐射的收集可通过两种反射方式:…     

自带光源的便携式太阳电池阵列测试系统

介绍了一种自带光源的便携式太阳电池阵列测试系统。该系统可以在无交流电源的现场对太阳电池组件和阵列进行快速测试，既可直接利用自然光源，也可利用自带光源测量。测试结果可在仪器的液晶模块显示，也可通过USB接口在上位机显示。该系统以TI公司的DSP芯片TMS320LF2407为核心，采用总线结构和模块化思想进行设计，具有易于维护和扩展性好等特点。     

An array of directable mirrors as a photovoltaic solar concentrator

Calculations of the optics of heliostats for use in large thermal power towers have been carried out in considerable detail, chiefly by Vant-Hull et al.[1, 2]. This paper describes a simplified method for calculating the images generated by a special type of concentrator, i.e. an array of independently steered mirrors on a single frame, intended to direct the solar image onto a flat photovoltaic solar cell target. The case of interest is one in which the field of illumination on the target is as uniform as possible, and the emphasis is thus on small “rim angle” geometries (a configuration which also minimizes mirror interference effects). Calculations are presented for constructing the individual mirror target images in terms of three angles: (1) The angle between the photovoltaic target normal and the reflecting mirror (celled here the mirror position angle). (2) The angle between the target center and the sun as measured from the center of the reflecting mirror, and (3) The angle at which the plane defined by the center of the sun, the mirror center and the target center intersects the plane of the target.The overall system efficiency for various mirror configurations, charaterized by such parameters as the maximum mirror angle (i.e. “rim angle”), target-mirror plane separation, and mirror aiming accuracy is discussed in terms of the specifications desirable in an optical concentrator designed specifically to illuminate uniformly a photovoltaic solar cell target.     

Optimal sizing of solar array and inverter in grid-connected photovoltaic systems

A new analytical approach is presented for finding the optimum ratio of photovoltaic array capacity to rated inverter input capacity in grid-connected photovoltaic systems. At optimum, the sizing ratio ranges from close to 1 for high insolation sites to well above 2 for low insolation conditions depending also on inverter characteristics and component costs. The sizing is more critical in low insolation conditions and the improvement of the economic performance thus obtained may be up to 20% compared to an inverter capacity equal to the PV-array. The optimum region is quite flat and up to ±20% deviations from the optimum point typically cause less than 2% losses. The analytical method coincides well with detailed numerical simulations for several locations (latitudes 33–60°N) and PV-array orientations used in the verification.     

Nanostructured solar cell based on spray pyrolysis deposited ZnO nanorod array

In this paper we present a realization of an extremely thin absorber (ETA) layer solar cell by the chemical spray pyrolysis method. CuInS₂ absorber was deposited onto a blocking layer coated ZnO nanorods grown on a transparent conductive oxide. Layers and cells were characterized by optical and Raman spectroscopy, and scanning electron microscopy. Current–voltage, spectral response and electron beam induced current measurements were applied to solar cells. ZnO nanorod cell showed twice higher short circuit current density than the flat reference. ETA cells with efficiency of 2.2% (j=12 mA/cm², V_oc=425 mV, FF=43%) and of 2.5% were prepared using TiO₂-anatase and an indium sulfide blocking layer, respectively.     

A solar cavity-receiver packed with an array of thermoelectric converter modules

We report on the design of a solar cavity-receiver packed with an array of thermoelectric converter (TEC) modules, which enables efficient capture of concentrated solar radiation entering through a small aperture. A 1 kW demonstrator (proof-of-concept) containing 18 TEC modules, each consisting of Al₂O₃ absorber/cooler plates, and p-type La_1.98Sr_0.02CuO₄ and n-type CaMn_0.98Nb_0.02O₃ thermoelements, was subjected to peak solar concentration ratios exceeding 600 suns over its aperture. The TEC modules were operated at 900 K on the hot side and 300 K on the cold side. The measured solar-to-electrical energy conversion efficiency was twice that of a directly irradiated TEC module. A heat transfer model was formulated to simulate the solar cavity-receiver system and experimentally validated in terms of open-circuit voltages measured as a function of the mean solar concentration ratio. Vis-à-vis a directly irradiated TEC module, the cavity configuration enabled a reduction of the re-radiation losses from 60% to 4% of the solar radiative power input. Theoretical considerations for TEC with figure-of-merit higher than 1 indicate the potential of reaching solar-to-electrical energy conversion efficiencies exceeding 11%.     

Application of optical film with micro-lens array on a solar concentrator

A plastic solar concentrating optical film with horizontal cylinder micro-lens array (HCMA) is presented in this study. The solar concentrator (SC) is in the form of optical film with HCMA and it is attached on the surface of a solar cell. This film is a polymethylmethacrylate (PMMA)-based optical layer. Compared with a plain solar collecting optical film without HCMA, the solar collecting optical film with HCMA can reduce the opportunity of reflection as light arrives at the surface and therefore can increase the refraction coefficient. As a result, the gain of photovoltaic power can be improved with the SC. Light is efficiently refracted by the HCMA and absorbed by the solar cell without the need of a solar tracking mechanism. Optimization of geometrical parameters of HCMA such as contact angle and gap (interspace) between each horizontal cylinder micro-lens is designed by simulation. The procedures of fabrication include reflow process, nickel-cobalt (Ni-Co) electroplating, and molding process. The measurement equipment of NEWPORT Oriel 91160+MODEL 6285 is utilized to measure the parameters such as open-circuit voltage V_oc, short-circuit current I_sc, and fill factor F.F., relating to the efficiency of the complete system. The experimental results show that a gain of photovoltaic power of about 3.30% is obtained with a contact angle of 62° and a gap of 15 μm.     

Prediction of solar array power output based on limited measured data

A methodology to predict solar cell/array power output based on the measurement of I_sc, V_oc and two points near P_mp is presented. The theory eliminates the need for precise measurement of cell/string maximum power point. The theory offers considerable cost and time reduction in the electrical evaluation of solar panels having BSF/BSFR type solar cells. A good match (within±2%) between the theoretical and experimental I-V characteristics is reported except near V_oc.     

Over 30% transparency large area inverted organic solar array by spray

We report the fabrication and characterization of large scale inverted organic solar array fabricated by all-spray process. The inverted polymer solar cell geometry consists of four layers, in the order of ITO-Cs₂CO₃-(P3HT:PCBM)-modified PEDPT:PSS, on a glass substrate. With semitransparent PEDPT:PSS as anode, the encapsulated solar array shows more than 30% transmission in the visible-near IR range. Optimization of device is done by thermal annealing, and the optimal annealing conditions are shown to be different in single-cell test device and the multiple-cell array. Solar illumination has been demonstrated to improve solar array efficiency up to 250%. Device efficiency of 1.80% was observed with the array under AM1.5 irradiance. Our preliminary data have shown that the performance enhancement under illumination only happens with sprayed devices, not devices made by spin coating. This means that solar cells made with our spray-on technique performs better under sunlight, which is beneficial for solar energy application.     

Medicinal herb drying using a photovoltaic array and a solar thermal system

Drying of medicinal herbs should take place as soon as possible after harvesting; otherwise insects and fungi, which thrive in most conditions, render them unusable. Conventional drying methods such as open sun drying and conventional-fuel dryers are not suitable; since they may yield a less quality product and/or may increase the drying cost and/or time. Moreover, they may not be reliable and environmentally safe. Therefore, the trend is toward using controlled-nonconventional drying methods, to improve the quality of the product to be dried and at the same time to decrease the drying cost and time. These methods use renewable energy sources for their operation, which are highly recommendable. This work proposes and develops a new controlled drying method; which uses a solar collector and a bio-gas fuel to heat the drying air, and a stand-alone photovoltaic (PV) system to feed the electrical load of the dryer. The designed control technique ensures correct and continuous operation of the dryer’s subsystems. Also, this work presents the dynamic modeling for the different components in the solar thermal system, which is responsible for heating the drying air. The results indicate the high effectiveness of the drying method.     

Simulation model for sizing of stand-alone solar PV system with interconnected array

Solar PV arrays made of interconnected modules are comparatively less susceptible to shadow problem and power degradation resulting from the aging of solar cells. This paper presents a simulation model for the sizing of stand-alone solar PV systems with interconnected arrays. It considers the electricity generation in the array and its storage in the battery bank serving the fluctuating load demand. The loss of power supply probability (LPSP) is used to connote the risk of not satisfying the load demand. The non-tracking (e.g., fixed and tilted) and single-axis tracking aperture arrays having cross-connected modules of single crystalline silicon solar cells in a (6×6) modular configuration are considered. The simulation results are illustrated with the help of a numerical example wherein the load demand is assumed to follow uniform probabilistic distribution. For a given load, the numbers of solar PV modules and batteries corresponding to zero values of LPSP on diurnal basis during the year round cycle of operation are presented. The results corresponding to the surplus and deficit of energy as a function of LPSP are also presented and discussed to assess the engineering design trade offs in the system components.Furthermore, a simple cost analysis has also been carried out, which indicates that for Delhi the stand-alone solar PV systems with fixed and tilted aperture arrays are better option than those with single-axis tracking aperture (with north–south oriented tracking axis) arrays.