Chaya Jivacate

Construction of Tungsten Halogen, Pulsed LED, and Combined Tungsten Halogen-LED Solar Simulators for Solar Cell - Characterization and Electrical Parameters Determination

- characterization of solar cells is generally done under natural sunlight or solar simulators operating in either a continuous mode or a pulse mode. Simulators are classified on three features of irradiance, namely, spectral match with respect to air mass 1.5, spatial uniformity, and temporal stability. Commercial solar simulators use Xenon lamps and halogen lamps, whereas LED-based solar simulators are being developed. In this work, we build and test seven simulators for solar cell characterization, namely, one tungsten halogen simulator, four monochromatic (red, green, blue, and white) LED simulators, one multicolor LED simulator, and one tungsten halogen-blue LED simulator. The seven simulators provide testing at nonstandard test condition. High irradiance from simulators is obtained by employing elevated supply voltage to tungsten halogen lamps and high pulsing voltages to LEDs. This new approach leads to higher irradiance not previously obtained from tungsten halogen lamps and LEDs. From - curves, electrical parameters of solar cell are made and corrected based on methods recommended in the IEC 60891 Standards. Corrected values obtained from non-STC measurements are in good agreement with those obtained from Class AAA solar simulator.

An impedance model of a PV grid-connected system

PV grid-connected systems are rich in nonlinear behaviors. Their operation depends on several factors such as radiation, switching algorithm and maximum power point tracking (MPPT) algorithm implemented in the grid-connected inverter which give rise to a variety of nonlinear behaviors and uncertainties. This paper proposes a passive impedance network as a model that can capture the system behaviors based on scenarios and data observed on the actual PV grid-connected system. A hardware experimental setup is created to imitate the operating characteristics of a PV grid-connected system such as current and voltage on both dc and ac sides. This work emphasizes on the salient features of the system operation and modeling strategies. Because of nonlinearity in the proposed model, the measured data and the Newton-Raphson iterative method are used to determine the model parameters. The study results show that the impedances in the proposed model have shown negative characteristics similar to that commonly found in power electronic converters. The proposed model may be integrated into a sequential, power solver for determining effects on a distribution system.

Experiment and simulation impulse partial discharge behavior in dielectric encapsulations of field-aged PV modules

Due to PV arrays must install inherently in exposed outdoor location or unsheltered and extended large-surface area, an installation of PV module is necessarily tolerable to direct or indirect lightning strikes without failure during the guaranteed service life time of PV module in the field. The primary aim of this paper is to identify the capability of withstand lightning impulse over-voltage of dielectric encapsulations after degradation in field-aged PV modules. In order to fulfill with the research field of insulating materials for deterioration PV module, the impulse partial discharge from charge release in various defects within the dielectric encapsulation between the edge of solar cells and the frame of PV module have been observed as well. For the simulation, the EMTP software and an electrical model of insulating materials of deterioration PV module was used to simulate the impulse partial discharge behavior. As to the experiment, the PV modules were applied by 1.2/50 μs lightning impulse generator into PV modules. It can be found that a number of ringing frequency trains as oscillations were superimposed on the impulse voltage waveform. Furthermore, the simulated result by EMTP deduced that the ringing oscillations caused by partial discharge in the defects of the degradation PV module. In addition, the partial discharge behaviors within the dielectric encapsulation of the PV module were given for some discussions about relevance of the safety in PV modules and their expected service life time in the field.

Performance assessment of PV modules after long field exposure in north eastern of Thailand

The weather of Thailand is generally known as humid topical and seasonal rain by monsoon. In early twenty first century for installing photovoltaic system in the northeast of Thailand, the cumulative wattage of photovoltaic (PV) water pumping units in rural areas was close to 1 MWp, and the PV battery charging system was also nearly 0.2 MWp. However, an assessment of performance parameters has not been wide investigated for carrying out the deterioration of PV modules under long-term field exposure in northeastern Thailand. Fortunately, there were 39 used single-crystalline silicon PV modules over ten years from the northeast of Thailand that have been collected at Clean Energy Systems Group (CES), King Mongkuts University of Technology Thonburi (KMUTT). Consequently, this paper focuses on the assessment of PV module performance parameters after degradation from real operating in the field. Dielectric encapsulations are diagnosed by visual inspection and electrical performance parameters of PV modules are measured at standard test condition by an indoor flash simulator. The diagnosis on physical deterioration in front of PV modules can be characterized into 7 categories. The results of I–V characteristics and performance parameters of the deterioration modules compose of initial performance degradation up to the worst-case degradation condition. Moreover, these results of I–V characteristics are directly correlated with the physical degradation such as browning and delaminating in front of the modules. We also found that, different browning and delaminating patterns in front of the modules may result in a decrease of both I–V characteristic shape and performance parameter.

PV Modules Deterioration with Less than 15 Years Installation in Thailand

This paper presents the investigation on deterioration of PV modules installed in Thailand. The modules under this study were dismantled and collected from KMUTT installation in the Buriram province. Modules were same model of modules that were installed over a thousand of solar water pumping systems and battery charging stations by Green E-san project since end of the 1980s and in earlier of 1990s. There are 35 modules, single crystalline silicon sized 47 Wp, in this study that were exposed in the field with less than 15 years. The experiments consist of visual inspection and measurement of performance at standard test condition (STC 1000 W/m2, 25 °C AM1.5) according to IEC61215:2005 standard. It is found that physical deteriorations and power output degradations. The physical deteriorations in this study can be classified delamination on middle cell, delamination on bus bar, delamination of edge cell and discoloration. For power output degradation, there is no module that was degraded less than 20% of nameplate wattage. There are only 8 of 35 modules (~23%) having power output over 50% of power rating.