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powered microcontroller-based data acquisition system for unattended remote measurements. The system was designed around the ST62E20 8-bit microcontroller and applied for solar radiation monitoring. The measurement system uses the SolData silicon-cell pyranometer as the solar radiation sensor. The data from the sensor is collected by means of on-chip A/D converter and stored in a serial EEPROM until uploaded to a portable computer. Keeping the DAS in a low-power mode, which is only interrupted when measurements are to be taken or when a computer is connected to retrieve the stored data, minimizes power consumption. An on-chip timer provides an interrupt to awaken the system from its low-power wait mode at 10-min intervals to sample and store the data. At the end of each data collection period, the acquired data will be transmitted to the computer through the RS232 serial port for subsequent analysis. System can automatically takes measurements and records the data, can be easily operated and does not require any programming expertise.
powered microcontroller-based data acquisition system for unattended remote measurements. The system was designed around the ST62E20 8-bit microcontroller and applied for solar radiation monitoring. The measurement system uses the SolData silicon-cell pyranometer as the solar radiation sensor. The data from the sensor is collected by means of on-chip A/D converter and stored in a serial EEPROM until uploaded to a portable computer. Keeping the DAS in a low-power mode, which is only interrupted when measurements are to be taken or when a computer is connected to retrieve the stored data, minimizes power consumption. An on-chip timer provides an interrupt to awaken the system from its low-power wait mode at 10-min intervals to sample and store the data. At the end of each data collection period, the acquired data will be transmitted to the computer through the RS232 serial port for subsequent analysis. System can automatically takes measurements and records the data, can be easily operated and does not require any programming expertise.


= =
= USING REMOTELY SENSED DATA TO ESTIMATE SURFACE ALBEDO AND ABSORBED PHOTOSYNTHETIC ACTIVE RADIATION =
== Authors ==
== Authors ==
DAVID L. TOLL, DAVID A. SHIREY, DAN S. KIMES
== Abstract ==
Paper studies the use of narrow band satellite radiance data such as that provided by the NOAA AVHRR to provide synoptic and repetitive values of land surface albedo and APAR. Field spectrometer is used to simulate AVHRR band reflectance and M A R estimates with pyranometer data for albedo estimation were used to test and develop algorithms to estimate albedo and APAR. The test site was the FIFE tall grass prairie in Kansas, USA. Analysis of results indicated the correction of surface anisotropy and estimation of a shortwave mid-IR (1.30-4.00 pm) were the most significant steps evaluated towards the derivation of a surface albedo. The estimation of APAR from AVHRR visible band reflectance data for a dense plant canopy may be completed by a simple linear transformation. The vegetation density through estimates of an NDVI may explain part of the variation in the linear transformations.
= STATISTICAL-MATHEMATICALMODEL OPTIMIZING PHOTOVOLTAIC ARRAY INCLINATION =
== Authors ==
G.Goglia, G.Mascia, R.Gattelli
== Abstract ==
The paper describes the system used in the experiment which is equipped with an automatic tracking device fit to keep both a photovoltaic module and a pyranometer in the orthogonal position to the sun. The system can perform adjustments to the azimuth as well as to the elevation angle every four minutes from sunrise to sunset, thus allowing to collect a range of data for each of the above said parameters and their relevant mean value per day, month, season and year. Data analysis and processing by statistical inferences and calculation of probabilities method, permit to have at one's disposal-in a given period- the most probable value of the parameters under examination.
= ROTATING SHADOW BAND PYRANOMETER IRRADIANCEMONITORING FOR PHOTOVOLTAICGENERATION EST1MATION =
== Authors ==
Edward C. Kern, Jr., Miles C. Russell
== Abstract ==
A new instrument has been developed to simplify and ruggedize the accurate field measurement of global horizontal, direct normal and horizontal diffuse solar irradiance. The rotating shadow band pyranometer performs the functions of a pyranometer, a pyrheliometer and sun- tracker at a lower cost and without precision set-up and frequent re-alignment.


= COMPARISON BETWEEN PYRANOMETERS AND ENCAPSULATED SOLAR CELLS AS REFERENCE PV SENSORS. OUTDOOR MEASUREMENTS I N REAL CONDITIONS =
== Authors ==
F. Chenlo, N. Vela and J. Olivares
== Abstract ==
== Abstract ==
This paper analyzed three types of reference sensors for outdoor mea-surements and PV installation monitoring purposes have been analyzed: pyranometers, reference solar cells and equivalent technology solar cells (ETSC) with the same type and encapsulation system as -
PV modules. A l l of the set points measured with - an automatic acquisition system along a sunny and completed day on tilted and fixed platform and - analuzed by statistical linear regression passing to the (0,O)point allow the determination of the calibration values of reference sensors. The ob- tained calibration deviation value for ETSC using a pyranometer as reference sensor was + 2% and a value of + 0 . 5 % when the reference sensor was other ETSC. With this method the spectral mismatch and temperature corrections and special ground preparation are not necessary for the Madrid condi-- Lions. The same analysis is helpful to reject non-linearity and badly encapsulated sensors. Finally paper concluded that a single solar cell with the same technology, encapsulation system, frame and - box connection as the PV modules, with a precision resistor, as the best reference sensor for outdoor PV measurements.


= =
= A SIMPLE WAY TO IMPLEMENT THE DIRECT COUPLING OF PV GENERATOR AND BA'ITERY IN ENERGY SIMULATION MODELS =
== Authors ==
== Authors ==
V.A.P. van Dijk, E.A. Alsema, K. Blok and W.C. Turkenburg
== Abstract ==
This paper investigated the accuracy of the approximation model using measured data of a PV street-light system. The average overestimation of the array output for the investigated periods is 6%, due to systematic errors at irradiation levels below 300 W/mz and at high module temperatures. Comparisons are made to a more elaborate calculation method based on a one-diode model for a PV module. The latter model gave a better accuracy of 2%. However, if pyranometer irradiation data are used instead of reference cell data an overestimation of up to 10% for both models was found. It is therefore concluded that the error introduced by the approximation model may be acceptable in comparison with the uncertainty introduced by using pyranometer data.


= A New Technique for Tracking the Global Maximum Power Point of PV Arrays Operating Under Partial-Shading Conditions =
== Authors ==
Eftichios Koutroulis, Frede Blaabjerg
== Abstract ==
== Abstract ==
In this paper, a new method to track the global MPP is presented. This method is based on controlling a dc/dc converter connected at the PV array output, such that it behaves as a constant input-power load. The proposed method has the advantage that it can be applied in either stand- alone or grid-connected PV systems comprising PV arrays with unknown electrical characteristics and does not require knowledge about the PV modules configuration within the PV array. The experimental results verify that the proposed global MPP method guarantees convergence to the global MPP under any partial- shading conditions. Compared with past-proposed methods, the global MPP tracking process is accomplished after far fewer PV array power perturbation steps.
Compared with the past-proposed global MPPT techniques, the method proposed in this paper has the advantage that it can be applied in PV arrays with unknown electrical characteristics and does not re- quire knowledge of the PV modules configuration within the PV array. The experimental results verify that the proposed method guarantees convergence to the global MPP under any partial- shading conditions. Additionally, the global MPPT process is accomplished with significantly less PV array power perturbation steps than those obtained using past-proposed techniques. The proposed method can easily be incorporated into any existing MPPT control system in both high nominal-power-rating PV systems and low-power energy harvesting applications.


= =
= Efficient Approaches for Modeling and Simulating Photovoltaic Power Systems =
== Authors ==
== Authors ==
Weidong Xiao, Fonkwe Fongang Edwin, Giovanni Spagnuolo, Juri Jatskevich
== Abstract ==
This study provides a simplified PV-cell model and its parameterization, guaranteeing that the I–V characteristic curves pass through the typical q points given in manufacturers’ datasheets. A simplified PV model is developed showing the detailed parameterization, which is based on the given information of the manufacturer datasheet. Furthermore, several power interface models are provided for fast simulation purpose. STC A classical two-stage power processing system with intermediate dc link used as a string inverter, as well as a single-stage conversion unit used in distributed module-dedicated PV applications, are VMPP taken as application examples. The generalized modeling approach is thoroughly evaluated by comparing the simulation results with the experimental data of a practical 2.4-kW grid-tied PV solar VOCS unit. The proposed methodology is shown to have advantages over conventional modeling approaches to simulate long-term grid-tied operation.


= Failure Analysis Techniques for Microsystems-Enabled Photovoltaics =
== Authors ==
Benjamin B. Yang, Jose L. Cruz-Campa, Gaddi S. Haase, Edward I. Cole Jr., Paiboon Tangyunyong, Paul J. Resnick, Alice C. Kilgo, Murat Okandan, Gregory N. Nielson
== Abstract ==
== Abstract ==
Paper explored the reliability of MEPV devices utilizes tools such as electrical characterization, EL, multi wavelength OBIC, and physical failure analysis to establish an effective set of failure analysis techniques for the technology. These methods are used to characterize MEPV de- vices and localized failure sites. EL and above-band-gap OBIC were demonstrated as methods to evaluate MEPV cell efficiency. The below-band-gap OBIC was shown to be an effective method to separately verify electrical connectivity of an MEPV cell.
Paper has also demonstrated good resilience to reverse bias voltage degradation. We found significant increases in leakage current, possibly because of avalanche breakdown, at voltage stresses exceeding –80 V. The minor increases in leakage current without the behavior of avalanche breakdown were observed after 600 h of voltage stress at –50 V. The evolution of the for- ward bias I–V curves correlated to the number of new defects, which was later verified using forward bias EL. Additional tests will enable development of a reliability model for reverse bias stress. The inclusion of additional stress testing such as temperature cycling and damp heat will lead to a comprehensive model to predict reliability. The failure analysis of accelerated testing samples will provide insight on how to further enhance the reliability of MEPV.
The failure analysis techniques described in this paper were found to be effective for MEPV and are likely good candidates to examine similar micro fabricated PV devices, which include those with other materials systems such as III–Vs. The difference in band gap in the case of III–Vs, however, means that different detectors and optical stimulus may be required. These defect localization methods can be used to evaluate individual cells in large MEPV arrays, which undergo stress tests. In addition, they can potentially serve as an early screening tool to identify future early failures in MEPV and other micro-PV arrays.


= =
= Maximum Efficiencies of Indoor Photovoltaic Devices =
== Authors ==
== Authors ==
Monika Freunek (Mu ̈ller), Michael Freunek, Leonhard M. Reind
== Abstract ==
Paper study the efficiency problems for IPV devices.
Energy-efficient electronics, such as used in sensor nodes, with an average power consumption in the range of microwatts en- able new application fields, e.g., in building automatization. For bandgaps above 1.40 eV, the ideal maximum efficiency for LED and fluorescent light increases dramatically with a maxi- mum close to 60% for an RGB white LED at 1.90 eV and 67% for a sodium discharge lamp. In the measurements, we achieved a maximum efficiency of 16% with a GaInP cell with an energy gap of 1.88 eV.
For energy gaps below 1.40 eV, the scattering of the results that are obtained for available small modules due to differences in the material quality or module integration might mask effects caused by the spectral response of the material.
IPV modules need to be further optimized for indoor appli- cations. This is especially true for modules from materials other than the traditional amorphous photovoltaic cells. P3HT:PCBM organic modules reached efficiencies close to those of standard amorphous solar cells. Given their low-cost production, the use of organic modules could, already at their current state of devel- opment, be an option for applications that require only a short lifetime.
For long-term applications, Ga(In)P, CdTe, and high-quality Si modules currently seem to be promising. In some application cases, the design of PV-powered devices, such as sensor nodes or presence detectors, and of the light sources will already be part of the planning of the building. In these cases, the use of concentrator PV cells without the need for a tracker will be possible, and the PV converter could be matched to the bandgap of any LED lighting applied.
An interesting result also for power beam applications that are based on laser radiation is the prediction from the detailed balance model of an increased efficiency with increased bandgap for a matched monochromatic emitter.


= Crack Statistic for Wafer-Based Silicon Solar Cell Modules in the Field Measured by UV Fluorescence =
== Authors ==
M. Ko ̈ntges, S. Kajari-Schro ̈der, and I. Kunze
== Abstract ==
== Abstract ==
The UV FL method is applicable to find cracks in PV modules in the field after about a 2-year exposure time in Germany. We verified again that cracks in wafer-based silicon PV modules are a common issue: In total, we found that 4.1% of the solar cells in the PV modules show at least one crack. Typically, we find an exponential-shaped histogram distribution of the number of cracked cell occurring in PV modules. For the crack type “cross crack,” which is caused by the production process and not changed by transportation, installation, and service life, we find a binominal-shaped histogram distribution of the number of cracked cells occurring in PV modules. This agrees well with the assumption of a randomly occurring crack initiation during or prior to module assembly. The fact that the other crack types follow other distributions lets us conclude that these cracks are not the result of random failures during production. Instead, we conclude that these other crack types grow after the PV modules leave the factory during transport, installation, and service life of the module. The propagation of most of these cracks follows the stress as induced by the mechanical load applied to the PV module. However, the high probability of cracking found parallel to the busbar indicates also a great influence of the cell interconnect ribbon to the crack direction. In order to protect the solar cells, it is therefore crucial to analyze and decrease the mechanical loads applied to the cells of a PV module during transportation, installation, and during its live time.


= =
= Investigating Voltage as a Function of the Reduced Junction Area for Thin Silicon Solar Cells That Utilize Epitaxial Lateral Overgrowth =
== Authors ==
== Authors ==
Christian Reichel, Filip Granek, Martin Hermle, and Stefan W. Glunz
== Abstract ==
This paper successfully demonstrated ELO for a reduced junction area. Unfortunately, reduced junction areas did not lead to the expected increase in voltage. We assume that the voltages of current ELO solar cells are largely limited by the quality of the lateral overgrowth region. Thus, to enhance this voltage and to perform a more comprehensive analysis, we will need to improve ELO Si quality. The mask material will need to be replaced with a dielectric that has a closer thermal expansion coefficient to Si. Currently, the thermally grown SiO2 has a thermal expansion coefficient that differs greatly from Si, generating defects at the interface between Si and SiO2 . Solving this problem will allow us to expose other sources that create a loss in Vo c , including solar cell geometry and orientation. Switching to a new dielectric will also enable further optimization of the growth conditions. Once these improvements have been implemented, the relationship between the voltage will be reexamined.


= Short-Circuit Current Losses in Back-Contacted Back–Junction Si Solar Cells: Experiment and Simulation of the Charge Collection Probability =
== Authors ==
Christian Reichel, Filip Granek, Martin Hermle, and Stefan W. Glunz
== Abstract ==
Paper investigated short-circuit current density losses due to recombination in back-contacted back-junction silicon solar cells. 2-D simulations of the charge carrier collection probability fc using the reciprocity theorem analyzed the losses. Hence, the direct calculation of current density without calculating the excess charge carrier concentration Δn and integrating the normal gradient of Δn over the collecting p-n junction was possible. The inhomogeneous continuity equation for Δn can, therefore, be transformed into a homogenous PDE for fc , enabling a much easier and faster determination of the Jsc losses of back-contacted back-junction silicon solar cells. In order to compare experimental and simulated results of solar cells with different pitch distances and base resistivity, Gaussian-like diffusion profiles for the emitter, BSF, and FSF, and a sophisticated optical model have been applied. The experimentally determined bulk charge carrier life- times and surface recombination velocities of undiffused and diffused regions have been used as input parameters for the simulations. It has been found that the measured local and global EQE of the solar cells could be well reproduced by the simulations, allowing a deeper understanding of the effects of the rear-side dimensions, i.e., pitch distance, and the base resistivity on the losses in current density. Thus, the presented simulation model pro- vides a powerful tool to find the optimal rear-side dimensions and optimize the diffusion profiles in order to obtain high current density values as an important step toward increasing the efficiency of back-contacted back-junction silicon solar cells.
= Direct Monitoring of Energy Lost Due to Soiling on First Solar Modules in California =
== Authors ==
J. Riley Caron, Bodo Littmann
== Abstract ==
This study reveals clear region- specific soiling trends as well as insight into the amount of rainfall required for full recovery of module performance. Soiling rates of up to 11.5% per month are observed in heavy agricultural areas. As little as 0.5 mm of rainfall is sufficient to completely clean a dirty frameless module in regions with lighter soiling rates.
With soiling rates of less than 1.0% per month in the low desert and peak rates of 11.5% per month in heavy agricultural regions of the Central Valley, it is clear that soiling trends vary greatly across California. The maximum soiling rates measured in this study are significantly less than rates seen in other studies in other parts of the world. Furthermore, the 20–30% soiling loss levels measured by AlBusairi and Mo ̈ller are the result of higher average relative humidity and dusty rains [8], conditions not encountered in our region of study. The modules in this study were installed at a 25◦ module tilt. For other tilt orientations, and especially for tracker systems, further analysis is needed to evaluate losses.
= Efficient Approaches for Modeling and Simulating Photovoltaic Power Systems =
== Authors ==
Weidong Xiao, Fonkwe Fongang Edwin, Giovanni Spagnuolo, Juri Jatskevich
== Abstract ==
This paper has presented a general approach to modeling and simulating PV power systems with regard to electrical engineering perspectives. A simplified PV model is developed showing the detailed parameterization, which is based on the given information of the manufacturer datasheet. Since the majority of PV power system is grid-tied, the modeling process focuses on two common power interfaces that include the two- stage power conversion with IDCL and single-stage conversion without IDCL. The MIC that is called “micro inverter” is also included for the simulation study. Due to the high-frequency switching nature of the MIC, the proposed averaged modeling approach demonstrates a simulation speed advantage, which is significantly faster than the conventional physical model. The simplified PV model is thoroughly evaluated by comparing the simulation results with the dataset provided by the product manufacturer. The performance index of NRMSD is used to illustrate the modeling accuracy. Furthermore, the 24-h data of a practical 2.4-kW grid-tied PV power system are also used to verify the proposed modeling method that is valid for a long-term simulation.
= Low-Temperature Concentrated Light Characterization Applied to Intermediate Band Solar Cells =
== Authors ==
Pablo G. Linares, Antonio Mart ́ı, Elisa Antol ́ın,  ́In ̃igo Ramiro, Esther Lo ́pez, Corrie D. Farmer, Colin R. Stanley, Antonio Luque
== Abstract ==
This paper described a novel low-temperature concentrated light characterization technique, and we apply it to the study of the so-called intermediate band solar cell (IBSC). This type of cell is characterized by hosting an intermediate band (IB) that is capable of providing both high current and high voltage. In most of its practical implementations, which are carried out by means of quantum dot (QD) structures, the energy band-diagram shows additional confined energy levels. These extra levels are responsible for an increase in the thermalization rate between the IB and the conduction band, which produces the degradation of the open-circuit voltage VO C . The original implementation of a setup that combines concentrated light and low temperature conditions is discussed in this paper. In this context, photo-generated current (IL )−VO C characteristics that are measured on QD-IBSC are presented in order to study their recombination, as well as their VOC recovery.
= Uncertainty in Photoconductance Measurements of the Emitter Saturation Current =
== Authors ==
Andrew F. Thomson, Ziv Hameiri, Nicholas E. Grant, Chris J. Price, Yan Di, and Jack Spurgin
== Abstract ==
Paper determined uncertainty in photoconductance (PC) measurements of the emitter saturation current density (J0 e ). A Monte Carlo method is used to calculate the impact of uncertainty from the input parameters including the test equipment calibration, the intrinsic-recombination model, and the measured sample’s thickness, doping, and optics. The uncertainty in the measurement of J0e is calculated, where paper found that these sensitivity to input uncertainty depends on the measurement mode, transient decay, or quasi-steady-state PC. For quasi-steady-state measurements, the uncertainty in J0e is largely affected by thickness and generation uncertainty. For transient measurements, thickness un- certainty dominates the uncertainty in J0 e . The wafer doping and measured voltage data has little impact on the resultant J0e uncertainty. Paper found, in the case study, that measurements of J0e to be accurate within 3%–6% when using the transient mode, and 4%–7% using the quasi-steady-state mode.
= A Maximum Power Point Tracker for Long-Term Logging of PV Module Performance =
== Authors ==
Uwe Zimmermann, Marika Edoff
== Abstract ==
== Abstract ==
This paper presented a monitoring system for the field test of photovoltaic modules. The system is designed for the monitoring of individual modules under maximum power point (MPP) conditions that allow the extraction of the energy yield of different modules under optimum conditions. It can also be used to monitor the performance and long-term stability of modules under realistic field conditions. The monitoring system consists of an individual MPP tracker attached to each module under test. The measurement data are transmitted to a central multichannel data logger by means of analog voltages proportional to the current at MPP of the modules.


= =
= Solar Profiles and Spectral Modeling for CPV Simulations =
== Authors ==
== Authors ==


== Abstract ==
== Abstract ==
In this paper, a computer model for the simulation of solar flux distribution in the direct and circumsolar regions of the beam irradiation is presented. The model incorporates circumsolar ratios (CSRs) and spectral transmittance. It is used to demonstrate the importance of realistic solar flux distributions as source inputs in high-concentration concentrator photovoltaic simulations. Realistic solar flux distributions are achieved by treating the Sun as an inhomogeneous extended light source. Flux distributions incident on lenses of various entry apertures are generated and used to investigate the losses in incident flux resulting from tracking errors and CSR variation. It is found that, for a Seattle-based concentrating system with an entry aperture of 0.5◦, a ∼5% loss in net annual incident flux occurs with a uniaxial tracking error of 0.3◦, and a ∼20% loss occurs with a uniaxial tracking error of 0.4◦. This analysis is at the primary concentrator stage; hence, it only considers the flux incident on the surface of the initial concentrating lens. The summation of flux at this primary stage does not account for further losses at the receiver because of optical misalignment.

Revision as of 12:41, 12 February 2014

Implementation of an Economic System to Measure Solar Radiatio

Authors

Mohamed Darwish, Omar G. Angulo Castro, Ricardo Valenzuela, Alejandro Ortega, Gildardo Jimenez

Abstract

A data acquisition system based on a pyranometer, data acquisition board and a computer to record and display the data are developed Pyranometer based in solar cell, National Instrument USB-6008 as data acquisition, LABView as interface system. Made this a considerably cheap system. The pyranometer was physically located on the top of the roof, reading was taken every 30 minutes during 33 days in January, March, April and May (why not Feb?), no night readings. All measurements from 6:00 am to 6:00 pm. Location at 31.19’07’’N and 110.56’45’’O, 1000 meters above sea level. Result shows a reading error within 7% and above 2%.

Solar Irradiance Estimation Based on Photovoltaic Module Short Circuit Current Measurement

Authors

Rodney H.G. Tan, Priscilla L.J.Tai, V.H. Mok

Abstract

This paper using the estimation method of solar irradiance based on the short circuit current output produce by the photovoltaic module. Paper trying to prove the feasibility of this method with desired accuracy. Paper introduced Photovoltaic Module Model as a circuit model, according to the property of its solar cell diode, derived the relation between short circuit currents and the solar irradiance leads to this. By acquiring the datasheet for solar cells diodes from their manufacturers, parameters for this relation can be derived using mathematical models. By considering these parameters, the solar irradiance can be estimated. However, the result shows that the highest error can reach 15.9%, making this estimation not a very ideal method for high accuracy applies but only for rough estimation while expensive measure device like pyranometers are desired.

PV-based Li-ion Battery Charger with Neural MPPT for Autonomous Sea Vehicles

Authors

M. C. Di Piazza, M. Luna, M. Pucci, G. Vitale

Abstract

Photovoltaic battery charger based on a DC-DC boost converter for a small size marine autonomous vehicle is developed. Neural-based technique is used to estimate the solar irradiance on the basis of the actual PV panel voltage and current to provide maximum output. This techniques is called Growing Neural Gas, and is exploited to realize a virtual Pyranometer to acquire instant solar irradiance. The GNG network is a self-supervised system to create best topology for the vehicle. GNG then is trained to learn data by experiment, and then recalling these by online calculation to estimate the irradiance. On the basis of this estimate, maximum power point tracking (MPPT) can be realized.

Accurate measurements of solar irradiance for evaluation of photovoltaic power profiles

Authors

Filippo Spertino, Member, IEEE, Paolo Di Leo, Valeria Cocina

Abstract

Based on five meteorological stations and the yearly experimental results, this paper discuss an observed phenomenon called ‘broken clouds’. This phenomena lead to noticeable peaks in measurement and PV power system. This effect occurs when clouds around sun amplified the beam irradiance, causing 20% more irradiance observed up to 500 W/m^2 lasting for minutes. It represent that investigation for this phenomena can be very useful to generate desired peak power. This still need for further study.

Development of Data Acquisition System for Hybrid Power Plant

Authors

Aryuanto Soetedjo, Yusuf Ismail Nakhoda

Abstract

Data acquisition system integrated wind speed monitor, Pyranometer and PV temperature measurement is realized. Low cost PV module is used as PV sensor. LABView is used as monitoring both wind speed and Pyranometer, and a SCADA system used to control the system is introduced by L. Wang and K.H. Liu in ‘mplementation of a Web-Based Real-Time Monitoring and Control System for a Hybrid Wind-PV-Battery Renewable Energy System’. Pyranometer works at 10 V and 30mA. Low error down to 3.45% for solar irradiance measurement is realized. Work represent that high accuracy integrated measurement system to monitor both wind a solar irradiance can be achieved at a considerably cheap price.

A Neural Network-Based Low-Cost Solar Irradiance Sensor

Authors

Fernando Mancilla-David, Francesco Riganti-Fulginei, Antonino Laudani, Alessandro Salvini

Abstract

Pyranometer is too expensive to be exploited in PV plants(?). To solve this, this paper introduced an approach to maximize efficiency based on neural networks. PV cell as irradiance sensor and a temperature senor and a low cost controller is used to realize this is introduced here to lower the cost. To use neural network (NN), a training set is introduced for learning, according to PV array mathematical model. After setting up the model, dataset was generated through experimental synthesis. System provide data for model to compute the irradiance. Compared to commercial Pyranometer(LM-10 HTD), this system provide a matched regression line, represents its high accuracy. However, paper did not give further discussion about the ignorance of peak irradiance due to algorithm.

An Improved Model-Based Maximum Power Point Tracker for Photovoltaic Panels

Authors

Loredana Cristaldi, Marco Faifer, Marco Rossi, and Sergio Toscani

Abstract

A model-based maximum power point tracker is said to be able to offers a better dynamic performance than observation based MPPT system. It even did not require direct irradiance measurement. This paper built a circuit model. Meanwhile, it take generated thermal energy into account as uncoverted solar irradiance.

A New Approach to Maximum Power Point Tracking for Photovoltaic Panels

Authors

Loredana Cristaldi, Marco Faifer, Marco Rossi, Sergio Toscani

Abstract

MPPT( Maximum Power Point Tracker) system is designed and this paper shows a method that applied no direct measurement for solar irradiance for this system. This methods based on preset model, based on solar cell circuit model. According to measured circuit cell temperature, module voltage and current, the irradiance can be calculated. This system does not require radiometer that appeared in many model based MPPT systems. Its result shows a acceptable average error within 5%, although with several high error point as high as 25%.

A Prototype of an Integrated Pyranometer for Measuring Multi-Parameters

Authors

Faiz Syazwan, Abdul Aziz1, Shahril Irwan Sulaiman, Hedzlin Zainuddin

Abstract

System was design integrated with Pyranometer and temperature sensor module. Solar cell is used as sensor to build Pyranometer. Compare to commercial Pyranometer, this integrated solar censor can provide measurement with error between -6.01% and +2.92%.

Simulation and energy management of an experimental solar system through adaptive neural networks

Authors

R.H. Fouad, M.S.Ashhab, A. Mukattash, S. Idwan

Abstract

A solar system is built integrated a solar trainer that contains a photovoltaic panel, a DC centrifugal pump, flat plate collectors, storage tank, a flowmeter for measuring the water mass flow rate, pipes, pyranometer for measuring the solar intensity, thermocouples for measuring various system temperatures and wind speed meter. For Pyranometer, an artificial neural network is applied based on the difference between measured data and pre-learnt data. To increase accuracy, short term prediction is modeled according to Kaczmarz’s algorithm. Adaptation technique is introduced to improve the accuracy. ANN is used as a technique to compensate for system parts degradation, environmental variations, time changes and modeling errors. Result shows that adaptive ANN is more accurate than non-adaptive ANN system.

Spectrally Selective Sensors for PV System Performance Monitoring

Authors

Anton Driesse, Daniela Dirnberger, Christian Reise, Nils Reich

Abstract

A spectrally matched reference solar cell is design to replace Pyranometer to measure plane of array(POA). System used two sensor with different non-overlapping spectral responses. Author used two sensors to measure the distribution of typical solar spectra. This method is proved to be useful for monitoring CdTe and CIS modules.

Performance Testing using Silicon Devices – Analysis of Accuracy

Authors

Manajit Sengupta, Peter Gotseff, Daryl Myers, Thomas Stoffel1

Abstract

This paper reviews the issues that will arise from the use of silicon detectors for PV performance measurement in the field based on measurements from a group of pyranometers mounted on a 1-axis solar tracker. Investigation is done on the impact of spectral sensitivity of silicon devices to find out why silicon based devices have more significant measurement difference. Experiment found that both Global Horizontal Irradiance(GHI) and Direct Normal Irradiance(DNI) measurements using silicon instruments have errors that are dependent on zenith angle. King et. al. (1998) correction have been devised to correct for these spectral errors.

Online Photovoltaic Array Hot-spot Bayesian Diagnostics from Streaming String-Level Electric Data

Authors

Shahar Ben-Menahem, Stephen C. Yang

Abstract

Paper introduced prototype MAP-based, in-operation incipient hot-spot failure diagnostics and prognostics algorithm running on a central database server. This can be an effective and minimal-cost diagnostics solution. For a small 4-string array, the total hardware cost will amount to less than $100. This system can realize low-cost hot-spot fault detection, diagnostics and prediction in the same time.

Power Rating Uncertainty Analysis of Electrical Performance of Photovoltaic Modules

Authors

Haitao Liu

Abstract

Paper shows that more attention should be given to the reference devices such as reference cell, reference module or pyranometer which contribute majority of uncertainty components. Research based on uncertainty analysis for electrical performance parameters. Paper shows that this uncertainty analysis can be estimated for both flat plate PV modules and concentrating PV modules or assemblies in practice.

Miniature pyranometer with asteroid shape thermopile

Authors

Jiangang Zhang, Zhengwei Wu, Zhan Zhao, Xin Guan

Abstract

A miniature pyranometer with a novel asteroid shape thermopile is designed with reduced size as small as 8mm by 4mm by 0.5mm. Output shows linear relation with irradiance. Resolution reached 0.191mV/10^5Lux. The thermopile unit is formed by sputtering technology, and the radiation absorption layer (Si3N4 film) is deposited above the thermopile layer by plasma-enhanced chemical vapor deposition. Silicon membrane is formed after the deposition.

Design Of A Photovoltaic System For A Rural House

Authors

M.Aminy, N.Barhemmati, A.Hadadian, F.Vali

Abstract

In this paper, calculation mean energy consumption of a rural area house, situating near Meshkin-dasht of Karaj providence in Iran is done. Using solar data registered in this area, the required electrical energy was calculated to be 2.88KWh with available mean solar radiation of 6 hours and rate of 6250MJ/m2. According to the calculations, 11 photovoltaic panels of 45W power and 2, 12V and 120Amph batteries as well as 2, 700W inverter are required. The rural house was considered for supplying AC electricity.

PERFORMANCE ASSESSMENT WITHOUT PYRANOMETERS: PREDICTING ENERGY OUTPUT BASED ON HISTORICAL CORRELATION

Authors

Anastasios Golnas, Joseph Bryan, Robert Wimbrow, Clifford Hansen, and Steve Voss

Abstract

An methodology is introduced. It can calculate the expected output of one or more systems in a regional fleet based on the measured power output from a subset of the total fleet. Method based on the correlation of historical data. With input information consisted of historical performance correlation and inter-system distance information, this method that can predict the energy output of a single PV system that belongs to a regional fleet by using information from other systems in that fleet. The best performing algorithm successfully predicted the weekly generation within 5% of the measured value between 73% and 96% of the time. When the accuracy threshold is relaxed to 10% the success rate varies between 91% and 99%. The monthly generation was predicted successfully at even higher rates – between 85% and 100% for a 5% threshold, and between 96% and 100% for a 10% threshold.

Estimation of Photovoltaic Power Generation Output based on Solar Irradiation and Frequency Classification

Authors

P. Attaviriyanupap, K. Tokuhara, N. Itaya, M. Marmiroli, Y. Tsukamoto, Y. Kojima

Abstract

In this paper, a method to estimate total power output of clustered photovoltaic power generation system (PV systems) is proposed. The proposed method make use of the real- time communication between pyranometer, current/voltage sensors, and control center to estimate power output of PV systems based on solar irradiation and power flow in the feeder, where PV systems are connected. The proposed method is divided into low-frequency and high-frequency component estimations. The low-frequency component is estimated based on the correlation between solar irradiation and energy generated from PV systems. On the other hand, the high-frequency component is estimated based on the frequency classification of power flow. The estimation is divided into low-frequency and high- frequency components estimation. The low-frequency component of PV power output is estimated based on the correlation between solar irradiation and energy generated from PV systems. The high-frequency component of PV power output is estimated based on the frequency classification of power flow in the feeder, where PV systems are connected. Simulation results show that error is approximately 3-4% of installed capacity for offline and online estimation. Simulation results also show that the accuracy of the proposed method can be improved by including load model in the low-frequency component estimation process.


Performance Improvement of SHWS by Increasing Thermal Efficiency Using Insulation Materials and Optimum Position of Solar Collectors

Authors

Jannatul Ferdous, Md Sanzidul Islam, Nabil Shaker, Bonny Amin Khan, A. Azad

Abstract

Solar Hot Water System(SHWS) is designed. Pyranometers were placed on roof of a two storied building having fine surrounding aperture. Two channels of the same data acquisition card are used for Global Horizontal Irradiance (GHI) and Diffuse Irradiance (DIF) data. The solar radiation values are predicted using meteorological parameters as these parameters are related to nature. The monthly averaged daily diffuse radiation is calculated using Angstrom like correlation. The total radiation on the tilted surface plane is also estimated.

Implementation of an intelligent sensor for measurement and prediction of solar radiation and atmospheric temperature

Authors

Joa ̃o M. Gomes∗,Pedro M. Ferreira†, Anto ́nio E. Ruano‡

Abstract

An intelligent sensor is developed for acquiring temperature, solar radiation data and estimate cloudiness indexes, and use these measured values to predict temperature and solar radiation in a close future. This can be used in systems related to thermal comfort in buildings and to the efficient and intelligent use of solar energy. Pyranometer is introduced to regularly measure solar radiation. Neural networks of the type NARX, which use the acquired data to forecast the cloudiness index, solar radiation and temperature, in the next four hours period. The cloudiness estimation neural network was trained with images from the TSI, the difference of results were observed. This result influences the prediction of the radiation by NARX algorithm.

Improved Structure of Solar Tracker with Microcontroller based Control

Authors

M. Amir Abas, M. Hilmi Fadzil S, Samsudin A.Kadir, A. Khusairy Azim

Abstract

A new mechanical structure for solar tracker was designed and presented. The structure implements two stepper motors for free rotation on X and Y axis. The rotation is intelligently controlled by a pre-programmed 2K microcontroller device PIC 18F4560 which provides simple programming strategy through C language. The designed algorithm is based on the measurement of intensity of solar radiation which is captured by an ultra violet sensitive device known as Pyranometer. The system has been tested and the results show very significant impact on the mechanical design, controlling algorithm and also the cost of the development.

A METHOD FOR SIMULTANEOUS BROADBAND SOLAR RADIATION CALIBRATION AND AEROSOL OPTICAL DEPTH RETRIEVAL

Authors

JINHUAN QIU

Abstract

A method is presented to calibrate pyrheliometer and pyranometer data using in-situ measurements of Direct Solar Radiation (DSR) and Global Solar Radiation (GSR). This method directly used World Radiation Reference (WRR, 1367.07 w/m2) as calibration standard, and it can be used to estimate or correct historical radiation records. Simultaneous pyranometer calibration and aerosol optical depth (AOD) retrieval introduced. Based on sensitivity of global solar radiation on aerosol optical parameters and surface albedo, this method is developed to calibrate pyrheliometer and pyranometer data using in-situ measurements of direct solar radiation and global solar radiation.

LONG TERM PERFORMANCE ANALYSIS OF PV MODULE IN THE GOBI DESERT OF MONGOLIA

Authors

Amarbayar Adiyabat, Kenji Otani1, Namjil Enebish, Naruush Enkhmaa

Abstract

This paper presents the evaluation results of a long-term performance of 2 type PV module from actual data measured over a period of more than 6 years in the Gobi Desert of Mongolia. For the purpose of estimating solar energy potentials and durability of PV systems in the Gobi desert area, a data acquisition system, which includes crystalline silicon (c-Si), polycrystalline silicon (p-Si) modules and precision pyranometer, thermometer and anemometer, have been installed. The paper indicated high output gain due to the extremely low ambient temperature and the module performance ratio showed high values in winter. In summary, the results of the present study show that PV modules with high temperature coefficients, such as crystalline silicon, are advantageous for use in desert area.

SOLAR RADIATION IN YUCATAN PENINSULA, PRELIMINARY ANALYSIS

Authors

Rolando Soler-Bientz, Lifter Ricalde-Cab

Abstract

Paper studied a Solar Radiation patterns on the Yucatan Peninsula in the Energy Laboratory of the Autonomous University of Yucatan using measurements of direct and global radiation on the horizontal plane. The raw data measured every two seconds and average every one minute was recorded automatically using a data­ logger with a pyrheliometer and a pyranometer which were installed on top of an automatic solar tracking system. The diurnal variation and frequency distribution of solar radiation were computed and discussed. Mean daily, monthly and seasonal were calculated from the measured data and analyzed within each calculation period. The results show that for the period of study that the diurnal contribution to the global solar radiation of the diffuse radiation during periods of maximum radiation is approximately 39%. The higher global solar radiations were registered in the month of April and June while the lowest one in October and December.

Estimation of Solar Power Generating Capacity

Authors

Lin Phyo Naing

Abstract

Paper proposes the Mathematical and Neural Network Prediction models for estimation of solar radiation for Singapore. Meteorological and geographical data (latitude, longitude, altitude, month, mean sunshine duration, etc.) were used as inputs to the models. The estimated results are compared with the field data obtained from the pyranometer installed on the solar panel with a tilt of 15°. The relevance and performance of each model in Singapore’s weather context is then evaluated using statistical tools, namely Mean Bias Error, Root Mean Squared Error and Mean Absolute Percentage Error. The results show that the correlation coefficients between the proposed model and the actual daily solar radiation were higher than 90%, thus suggesting a high reliability of the model for evaluation of solar radiation received in Singapore. These models can be used easily for estimation of solar radiation for preliminary design of solar applications.

NOMINAL OPERATING CELL TEMPERATURE (NOCT): EFFECTS OF MODULE SIZE, LOADING AND SOLAR SPECTRUM

Authors

Ruhi Bharti, Joseph Kuitche, Mani G. TamizhMani

Abstract

Paper discussed Nominal Operating Cell Temperature(NOCT). Preliminary results were measured in this paper. It is concluded that the larger size modules exhibit higher NOCT values (~4oC) when compared to smaller size modules under the OC condition as required by the IEC 61215 standard. The OC condition which is required by the IEC 61215 standard always exhibits higher NOCT values (up to 3oC) as compared to RL condition. Also, the choice of irradiance sensor type (pyranometer or reference cell) does not appear to affect the NOCT value. Thus, either pyranometer or reference cell could be used for determining the NOCT.

Optimizing design of household scale hybrid solar photovoltaic + combined heat and power system

Authors

P. Derewonko, J. M. Pearce

Abstract

This paper investigates the feasibility of implementing a hybrid solar photovoltaic (PV) + combined heat and power (CHP) and battery bank system for a residential application to generate reliable base load power to the grid in Ontario. Deploying PV on a large-scale has a penetration level threshold due to the inherent power supply intermittency associated with the solar resource. By creating a hybrid PV+CHP system there is potential of increasing the PV penetration level. One year of one second resolution pyranometer data is analyzed for Kingston Ontario to determine the total amount of PV energy generation potential, the rate of change of PV power generation due to intermittent cloud cover, and the daily CHP run time required to supply reliable base load power to the grid using this hybrid system. This analysis found that the vast majority of solar energy fluctuations are small in magnitude and the worst case energy fluctuation can be accommodated by relatively inexpensive and simple storage with conventional lead-acid batteries. For systems where the PV power rating is identical to the CHP unit, the CHP unit must run for more than twenty hours a day for the system to meet the base load requirement during the winter months. This provides a fortunate supply of heat, which can be used for the needed home heating. It was found that in the Kingston, Ontario area, 50% of the available solar energy is lost due to cloud cover. By plotting a histogram of the change in solar energy per second throughout the year, it was found that the vast majority of solar energy fluctuations are small in magnitude and are associated with the natural daily cycle of solar energy. The worst case energy fluctuation can be handled by relatively inexpensive lead-acid batteries. For the hybrid system to run effectively, the CHP unit must be on for more than twenty hours a day year round, resulting in high natural gas costs and emissions. The system presented in this paper must be optimized by changing key variables such as the base load power requirement, the PV array tilt angle and the size of the PV array.

EXPERIMENTAL SETUP FOR MULTIPARAMETRIC CHARACTERIZATION OF PHOTOVOLTAIC PANELS

Authors

Aimé Lay-Ekuakille, Amerigo Trotta, Fabio Miduri, Rita Carella, David Alonso

Abstract

This paper represents an effective method of prediction of the energy produced by the photovoltaic systems and an acceptable method of their characterization by using an experimental setup. The prediction of the energy produced by a photovoltaic system is generally made through software which uses algorithms that describe the trend of the efficiency of the panels depending on the temperature, the radiation and, in more particular cases, depending on the incident spectrum features.

A improvement for the surface solar insolation retrieval from Geostationary sensor

Authors

Jong-Min Yeom, Kyung-Soo Han, Youn-Young Park, Chang-Suck Lee, Young-Seup Kim

Abstract

This study generated a neural network-based cloud factor retrieval system, which can improve accuracy of SSI estimation for cloudy condition. In this study, multilayer feed-forward (MLF) neural network (NN) was employed with Levenberg-Marquardt back-propagation (LM-BP) and early stopping method to avoid the over-fitting. The number of hidden nodes was determined by using trial and error method since too complicated network was apt to be over-fitting, while a too simple network structure will have difficult training the network. The validation of the estimated SSI using NN-based cloud factor was performed with II. pyranometer measurement data obtained from 22 meteorological stations over Korea peninsula. This SSI estimation for cloudy condition showed a good agreement with ground-based measurements (RMSE = 66.0 W/m2). This accuracy indicates that the use of NN-based cloud factor leads an improvement for SSI estimation in comparison with use of previous system of cloud factor.

EFFECTIVE IRRADIANCE ESTIMATION FOR PV APPLICATIONS

Authors

M. Alonso Abella’, E. Lorenzo’, F. Chenlo’

Abstract

Paper experimentally evaluates some of the most referenced methods to estimate the global irradiance incident on tilted surfaces from measured global horizontal irradiance. Angular and spectral effects are also considered for the estimation of the “effective irradiance” to be used by PV modules in PV installations. Angular effects of pyranometers on horizontal surface irradiance measurements and their influence in tilted irradiance estimation are also analyzed. A relationship between the diffuse and global horizontal irradiation models are established. Anisotropic Hay and Perez punctual models are used for tilted irradiance estimation.

EVALUATION OF SOLAR ENERGY POTENTIALS IN GOBI DESERT AREA OF MONGOLIA

Authors

G.Batsukh' ,D.Ochirbaanil, Ch.Lkhagvajavl, N.Enehishl, B.Ganbt' and Ts.Baatarchuluun' Kenji Otani and Koichi Sakuta, Amarbayar Adiyabat3and Kosuke Kurokawa

Abstract

A new data acquisition system has been developed and installed in. The results of the measurements show that an average value of monthly sum of integrated global radiations measured by M-80 pyranometer for every 3 hours are 10% less than global radiations measured by CPR-CM-21 pyranometer for every 10 minutes

A Microcontroller-Based Data Acquisition System for Solar Radiation and Environmental Monitoring

Authors

Raphael Mukaro and Xavier Francis Carelse

Abstract

Paper presents t hardware design and operation of a battery- powered microcontroller-based data acquisition system for unattended remote measurements. The system was designed around the ST62E20 8-bit microcontroller and applied for solar radiation monitoring. The measurement system uses the SolData silicon-cell pyranometer as the solar radiation sensor. The data from the sensor is collected by means of on-chip A/D converter and stored in a serial EEPROM until uploaded to a portable computer. Keeping the DAS in a low-power mode, which is only interrupted when measurements are to be taken or when a computer is connected to retrieve the stored data, minimizes power consumption. An on-chip timer provides an interrupt to awaken the system from its low-power wait mode at 10-min intervals to sample and store the data. At the end of each data collection period, the acquired data will be transmitted to the computer through the RS232 serial port for subsequent analysis. System can automatically takes measurements and records the data, can be easily operated and does not require any programming expertise.

USING REMOTELY SENSED DATA TO ESTIMATE SURFACE ALBEDO AND ABSORBED PHOTOSYNTHETIC ACTIVE RADIATION

Authors

DAVID L. TOLL, DAVID A. SHIREY, DAN S. KIMES

Abstract

Paper studies the use of narrow band satellite radiance data such as that provided by the NOAA AVHRR to provide synoptic and repetitive values of land surface albedo and APAR. Field spectrometer is used to simulate AVHRR band reflectance and M A R estimates with pyranometer data for albedo estimation were used to test and develop algorithms to estimate albedo and APAR. The test site was the FIFE tall grass prairie in Kansas, USA. Analysis of results indicated the correction of surface anisotropy and estimation of a shortwave mid-IR (1.30-4.00 pm) were the most significant steps evaluated towards the derivation of a surface albedo. The estimation of APAR from AVHRR visible band reflectance data for a dense plant canopy may be completed by a simple linear transformation. The vegetation density through estimates of an NDVI may explain part of the variation in the linear transformations.

STATISTICAL-MATHEMATICALMODEL OPTIMIZING PHOTOVOLTAIC ARRAY INCLINATION

Authors

G.Goglia, G.Mascia, R.Gattelli

Abstract

The paper describes the system used in the experiment which is equipped with an automatic tracking device fit to keep both a photovoltaic module and a pyranometer in the orthogonal position to the sun. The system can perform adjustments to the azimuth as well as to the elevation angle every four minutes from sunrise to sunset, thus allowing to collect a range of data for each of the above said parameters and their relevant mean value per day, month, season and year. Data analysis and processing by statistical inferences and calculation of probabilities method, permit to have at one's disposal-in a given period- the most probable value of the parameters under examination.

ROTATING SHADOW BAND PYRANOMETER IRRADIANCEMONITORING FOR PHOTOVOLTAICGENERATION EST1MATION

Authors

Edward C. Kern, Jr., Miles C. Russell

Abstract

A new instrument has been developed to simplify and ruggedize the accurate field measurement of global horizontal, direct normal and horizontal diffuse solar irradiance. The rotating shadow band pyranometer performs the functions of a pyranometer, a pyrheliometer and sun- tracker at a lower cost and without precision set-up and frequent re-alignment.

COMPARISON BETWEEN PYRANOMETERS AND ENCAPSULATED SOLAR CELLS AS REFERENCE PV SENSORS. OUTDOOR MEASUREMENTS I N REAL CONDITIONS

Authors

F. Chenlo, N. Vela and J. Olivares

Abstract

This paper analyzed three types of reference sensors for outdoor mea-surements and PV installation monitoring purposes have been analyzed: pyranometers, reference solar cells and equivalent technology solar cells (ETSC) with the same type and encapsulation system as - PV modules. A l l of the set points measured with - an automatic acquisition system along a sunny and completed day on tilted and fixed platform and - analuzed by statistical linear regression passing to the (0,O)point allow the determination of the calibration values of reference sensors. The ob- tained calibration deviation value for ETSC using a pyranometer as reference sensor was + 2% and a value of + 0 . 5 % when the reference sensor was other ETSC. With this method the spectral mismatch and temperature corrections and special ground preparation are not necessary for the Madrid condi-- Lions. The same analysis is helpful to reject non-linearity and badly encapsulated sensors. Finally paper concluded that a single solar cell with the same technology, encapsulation system, frame and - box connection as the PV modules, with a precision resistor, as the best reference sensor for outdoor PV measurements.

A SIMPLE WAY TO IMPLEMENT THE DIRECT COUPLING OF PV GENERATOR AND BA'ITERY IN ENERGY SIMULATION MODELS

Authors

V.A.P. van Dijk, E.A. Alsema, K. Blok and W.C. Turkenburg

Abstract

This paper investigated the accuracy of the approximation model using measured data of a PV street-light system. The average overestimation of the array output for the investigated periods is 6%, due to systematic errors at irradiation levels below 300 W/mz and at high module temperatures. Comparisons are made to a more elaborate calculation method based on a one-diode model for a PV module. The latter model gave a better accuracy of 2%. However, if pyranometer irradiation data are used instead of reference cell data an overestimation of up to 10% for both models was found. It is therefore concluded that the error introduced by the approximation model may be acceptable in comparison with the uncertainty introduced by using pyranometer data.

A New Technique for Tracking the Global Maximum Power Point of PV Arrays Operating Under Partial-Shading Conditions

Authors

Eftichios Koutroulis, Frede Blaabjerg

Abstract

In this paper, a new method to track the global MPP is presented. This method is based on controlling a dc/dc converter connected at the PV array output, such that it behaves as a constant input-power load. The proposed method has the advantage that it can be applied in either stand- alone or grid-connected PV systems comprising PV arrays with unknown electrical characteristics and does not require knowledge about the PV modules configuration within the PV array. The experimental results verify that the proposed global MPP method guarantees convergence to the global MPP under any partial- shading conditions. Compared with past-proposed methods, the global MPP tracking process is accomplished after far fewer PV array power perturbation steps. Compared with the past-proposed global MPPT techniques, the method proposed in this paper has the advantage that it can be applied in PV arrays with unknown electrical characteristics and does not re- quire knowledge of the PV modules configuration within the PV array. The experimental results verify that the proposed method guarantees convergence to the global MPP under any partial- shading conditions. Additionally, the global MPPT process is accomplished with significantly less PV array power perturbation steps than those obtained using past-proposed techniques. The proposed method can easily be incorporated into any existing MPPT control system in both high nominal-power-rating PV systems and low-power energy harvesting applications.

Efficient Approaches for Modeling and Simulating Photovoltaic Power Systems

Authors

Weidong Xiao, Fonkwe Fongang Edwin, Giovanni Spagnuolo, Juri Jatskevich

Abstract

This study provides a simplified PV-cell model and its parameterization, guaranteeing that the I–V characteristic curves pass through the typical q points given in manufacturers’ datasheets. A simplified PV model is developed showing the detailed parameterization, which is based on the given information of the manufacturer datasheet. Furthermore, several power interface models are provided for fast simulation purpose. STC A classical two-stage power processing system with intermediate dc link used as a string inverter, as well as a single-stage conversion unit used in distributed module-dedicated PV applications, are VMPP taken as application examples. The generalized modeling approach is thoroughly evaluated by comparing the simulation results with the experimental data of a practical 2.4-kW grid-tied PV solar VOCS unit. The proposed methodology is shown to have advantages over conventional modeling approaches to simulate long-term grid-tied operation.

Failure Analysis Techniques for Microsystems-Enabled Photovoltaics

Authors

Benjamin B. Yang, Jose L. Cruz-Campa, Gaddi S. Haase, Edward I. Cole Jr., Paiboon Tangyunyong, Paul J. Resnick, Alice C. Kilgo, Murat Okandan, Gregory N. Nielson

Abstract

Paper explored the reliability of MEPV devices utilizes tools such as electrical characterization, EL, multi wavelength OBIC, and physical failure analysis to establish an effective set of failure analysis techniques for the technology. These methods are used to characterize MEPV de- vices and localized failure sites. EL and above-band-gap OBIC were demonstrated as methods to evaluate MEPV cell efficiency. The below-band-gap OBIC was shown to be an effective method to separately verify electrical connectivity of an MEPV cell. Paper has also demonstrated good resilience to reverse bias voltage degradation. We found significant increases in leakage current, possibly because of avalanche breakdown, at voltage stresses exceeding –80 V. The minor increases in leakage current without the behavior of avalanche breakdown were observed after 600 h of voltage stress at –50 V. The evolution of the for- ward bias I–V curves correlated to the number of new defects, which was later verified using forward bias EL. Additional tests will enable development of a reliability model for reverse bias stress. The inclusion of additional stress testing such as temperature cycling and damp heat will lead to a comprehensive model to predict reliability. The failure analysis of accelerated testing samples will provide insight on how to further enhance the reliability of MEPV. The failure analysis techniques described in this paper were found to be effective for MEPV and are likely good candidates to examine similar micro fabricated PV devices, which include those with other materials systems such as III–Vs. The difference in band gap in the case of III–Vs, however, means that different detectors and optical stimulus may be required. These defect localization methods can be used to evaluate individual cells in large MEPV arrays, which undergo stress tests. In addition, they can potentially serve as an early screening tool to identify future early failures in MEPV and other micro-PV arrays.

Maximum Efficiencies of Indoor Photovoltaic Devices

Authors

Monika Freunek (Mu ̈ller), Michael Freunek, Leonhard M. Reind

Abstract

Paper study the efficiency problems for IPV devices. Energy-efficient electronics, such as used in sensor nodes, with an average power consumption in the range of microwatts en- able new application fields, e.g., in building automatization. For bandgaps above 1.40 eV, the ideal maximum efficiency for LED and fluorescent light increases dramatically with a maxi- mum close to 60% for an RGB white LED at 1.90 eV and 67% for a sodium discharge lamp. In the measurements, we achieved a maximum efficiency of 16% with a GaInP cell with an energy gap of 1.88 eV. For energy gaps below 1.40 eV, the scattering of the results that are obtained for available small modules due to differences in the material quality or module integration might mask effects caused by the spectral response of the material. IPV modules need to be further optimized for indoor appli- cations. This is especially true for modules from materials other than the traditional amorphous photovoltaic cells. P3HT:PCBM organic modules reached efficiencies close to those of standard amorphous solar cells. Given their low-cost production, the use of organic modules could, already at their current state of devel- opment, be an option for applications that require only a short lifetime. For long-term applications, Ga(In)P, CdTe, and high-quality Si modules currently seem to be promising. In some application cases, the design of PV-powered devices, such as sensor nodes or presence detectors, and of the light sources will already be part of the planning of the building. In these cases, the use of concentrator PV cells without the need for a tracker will be possible, and the PV converter could be matched to the bandgap of any LED lighting applied. An interesting result also for power beam applications that are based on laser radiation is the prediction from the detailed balance model of an increased efficiency with increased bandgap for a matched monochromatic emitter.

Crack Statistic for Wafer-Based Silicon Solar Cell Modules in the Field Measured by UV Fluorescence

Authors

M. Ko ̈ntges, S. Kajari-Schro ̈der, and I. Kunze

Abstract

The UV FL method is applicable to find cracks in PV modules in the field after about a 2-year exposure time in Germany. We verified again that cracks in wafer-based silicon PV modules are a common issue: In total, we found that 4.1% of the solar cells in the PV modules show at least one crack. Typically, we find an exponential-shaped histogram distribution of the number of cracked cell occurring in PV modules. For the crack type “cross crack,” which is caused by the production process and not changed by transportation, installation, and service life, we find a binominal-shaped histogram distribution of the number of cracked cells occurring in PV modules. This agrees well with the assumption of a randomly occurring crack initiation during or prior to module assembly. The fact that the other crack types follow other distributions lets us conclude that these cracks are not the result of random failures during production. Instead, we conclude that these other crack types grow after the PV modules leave the factory during transport, installation, and service life of the module. The propagation of most of these cracks follows the stress as induced by the mechanical load applied to the PV module. However, the high probability of cracking found parallel to the busbar indicates also a great influence of the cell interconnect ribbon to the crack direction. In order to protect the solar cells, it is therefore crucial to analyze and decrease the mechanical loads applied to the cells of a PV module during transportation, installation, and during its live time.

Investigating Voltage as a Function of the Reduced Junction Area for Thin Silicon Solar Cells That Utilize Epitaxial Lateral Overgrowth

Authors

Christian Reichel, Filip Granek, Martin Hermle, and Stefan W. Glunz

Abstract

This paper successfully demonstrated ELO for a reduced junction area. Unfortunately, reduced junction areas did not lead to the expected increase in voltage. We assume that the voltages of current ELO solar cells are largely limited by the quality of the lateral overgrowth region. Thus, to enhance this voltage and to perform a more comprehensive analysis, we will need to improve ELO Si quality. The mask material will need to be replaced with a dielectric that has a closer thermal expansion coefficient to Si. Currently, the thermally grown SiO2 has a thermal expansion coefficient that differs greatly from Si, generating defects at the interface between Si and SiO2 . Solving this problem will allow us to expose other sources that create a loss in Vo c , including solar cell geometry and orientation. Switching to a new dielectric will also enable further optimization of the growth conditions. Once these improvements have been implemented, the relationship between the voltage will be reexamined.

Short-Circuit Current Losses in Back-Contacted Back–Junction Si Solar Cells: Experiment and Simulation of the Charge Collection Probability

Authors

Christian Reichel, Filip Granek, Martin Hermle, and Stefan W. Glunz

Abstract

Paper investigated short-circuit current density losses due to recombination in back-contacted back-junction silicon solar cells. 2-D simulations of the charge carrier collection probability fc using the reciprocity theorem analyzed the losses. Hence, the direct calculation of current density without calculating the excess charge carrier concentration Δn and integrating the normal gradient of Δn over the collecting p-n junction was possible. The inhomogeneous continuity equation for Δn can, therefore, be transformed into a homogenous PDE for fc , enabling a much easier and faster determination of the Jsc losses of back-contacted back-junction silicon solar cells. In order to compare experimental and simulated results of solar cells with different pitch distances and base resistivity, Gaussian-like diffusion profiles for the emitter, BSF, and FSF, and a sophisticated optical model have been applied. The experimentally determined bulk charge carrier life- times and surface recombination velocities of undiffused and diffused regions have been used as input parameters for the simulations. It has been found that the measured local and global EQE of the solar cells could be well reproduced by the simulations, allowing a deeper understanding of the effects of the rear-side dimensions, i.e., pitch distance, and the base resistivity on the losses in current density. Thus, the presented simulation model pro- vides a powerful tool to find the optimal rear-side dimensions and optimize the diffusion profiles in order to obtain high current density values as an important step toward increasing the efficiency of back-contacted back-junction silicon solar cells.

Direct Monitoring of Energy Lost Due to Soiling on First Solar Modules in California

Authors

J. Riley Caron, Bodo Littmann

Abstract

This study reveals clear region- specific soiling trends as well as insight into the amount of rainfall required for full recovery of module performance. Soiling rates of up to 11.5% per month are observed in heavy agricultural areas. As little as 0.5 mm of rainfall is sufficient to completely clean a dirty frameless module in regions with lighter soiling rates. With soiling rates of less than 1.0% per month in the low desert and peak rates of 11.5% per month in heavy agricultural regions of the Central Valley, it is clear that soiling trends vary greatly across California. The maximum soiling rates measured in this study are significantly less than rates seen in other studies in other parts of the world. Furthermore, the 20–30% soiling loss levels measured by AlBusairi and Mo ̈ller are the result of higher average relative humidity and dusty rains [8], conditions not encountered in our region of study. The modules in this study were installed at a 25◦ module tilt. For other tilt orientations, and especially for tracker systems, further analysis is needed to evaluate losses.

Efficient Approaches for Modeling and Simulating Photovoltaic Power Systems

Authors

Weidong Xiao, Fonkwe Fongang Edwin, Giovanni Spagnuolo, Juri Jatskevich

Abstract

This paper has presented a general approach to modeling and simulating PV power systems with regard to electrical engineering perspectives. A simplified PV model is developed showing the detailed parameterization, which is based on the given information of the manufacturer datasheet. Since the majority of PV power system is grid-tied, the modeling process focuses on two common power interfaces that include the two- stage power conversion with IDCL and single-stage conversion without IDCL. The MIC that is called “micro inverter” is also included for the simulation study. Due to the high-frequency switching nature of the MIC, the proposed averaged modeling approach demonstrates a simulation speed advantage, which is significantly faster than the conventional physical model. The simplified PV model is thoroughly evaluated by comparing the simulation results with the dataset provided by the product manufacturer. The performance index of NRMSD is used to illustrate the modeling accuracy. Furthermore, the 24-h data of a practical 2.4-kW grid-tied PV power system are also used to verify the proposed modeling method that is valid for a long-term simulation.

Low-Temperature Concentrated Light Characterization Applied to Intermediate Band Solar Cells

Authors

Pablo G. Linares, Antonio Mart ́ı, Elisa Antol ́ın, ́In ̃igo Ramiro, Esther Lo ́pez, Corrie D. Farmer, Colin R. Stanley, Antonio Luque

Abstract

This paper described a novel low-temperature concentrated light characterization technique, and we apply it to the study of the so-called intermediate band solar cell (IBSC). This type of cell is characterized by hosting an intermediate band (IB) that is capable of providing both high current and high voltage. In most of its practical implementations, which are carried out by means of quantum dot (QD) structures, the energy band-diagram shows additional confined energy levels. These extra levels are responsible for an increase in the thermalization rate between the IB and the conduction band, which produces the degradation of the open-circuit voltage VO C . The original implementation of a setup that combines concentrated light and low temperature conditions is discussed in this paper. In this context, photo-generated current (IL )−VO C characteristics that are measured on QD-IBSC are presented in order to study their recombination, as well as their VOC recovery.

Uncertainty in Photoconductance Measurements of the Emitter Saturation Current

Authors

Andrew F. Thomson, Ziv Hameiri, Nicholas E. Grant, Chris J. Price, Yan Di, and Jack Spurgin

Abstract

Paper determined uncertainty in photoconductance (PC) measurements of the emitter saturation current density (J0 e ). A Monte Carlo method is used to calculate the impact of uncertainty from the input parameters including the test equipment calibration, the intrinsic-recombination model, and the measured sample’s thickness, doping, and optics. The uncertainty in the measurement of J0e is calculated, where paper found that these sensitivity to input uncertainty depends on the measurement mode, transient decay, or quasi-steady-state PC. For quasi-steady-state measurements, the uncertainty in J0e is largely affected by thickness and generation uncertainty. For transient measurements, thickness un- certainty dominates the uncertainty in J0 e . The wafer doping and measured voltage data has little impact on the resultant J0e uncertainty. Paper found, in the case study, that measurements of J0e to be accurate within 3%–6% when using the transient mode, and 4%–7% using the quasi-steady-state mode.

A Maximum Power Point Tracker for Long-Term Logging of PV Module Performance

Authors

Uwe Zimmermann, Marika Edoff

Abstract

This paper presented a monitoring system for the field test of photovoltaic modules. The system is designed for the monitoring of individual modules under maximum power point (MPP) conditions that allow the extraction of the energy yield of different modules under optimum conditions. It can also be used to monitor the performance and long-term stability of modules under realistic field conditions. The monitoring system consists of an individual MPP tracker attached to each module under test. The measurement data are transmitted to a central multichannel data logger by means of analog voltages proportional to the current at MPP of the modules.

Solar Profiles and Spectral Modeling for CPV Simulations

Authors

Abstract

In this paper, a computer model for the simulation of solar flux distribution in the direct and circumsolar regions of the beam irradiation is presented. The model incorporates circumsolar ratios (CSRs) and spectral transmittance. It is used to demonstrate the importance of realistic solar flux distributions as source inputs in high-concentration concentrator photovoltaic simulations. Realistic solar flux distributions are achieved by treating the Sun as an inhomogeneous extended light source. Flux distributions incident on lenses of various entry apertures are generated and used to investigate the losses in incident flux resulting from tracking errors and CSR variation. It is found that, for a Seattle-based concentrating system with an entry aperture of 0.5◦, a ∼5% loss in net annual incident flux occurs with a uniaxial tracking error of 0.3◦, and a ∼20% loss occurs with a uniaxial tracking error of 0.4◦. This analysis is at the primary concentrator stage; hence, it only considers the flux incident on the surface of the initial concentrating lens. The summation of flux at this primary stage does not account for further losses at the receiver because of optical misalignment.

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