Krissanapong Kirtikara

Amperometric determination of hydrogen peroxide by direct and catalytic reduction at a copper electrode

In a buffer solution at ambient temperature and dissolved oxygen concentration, pH 6.7, copper electrodes could be cycled between the Cu(0)/Cu(II) redox states, by cycling the potential between −0.8 and +0.3 V vs. SCE. At 1 V s−1, the reduction of Cu(II) proceeded with a rate constant of 12.3 s−1 (αC = 0.16, αA = 0.93). The redox couple catalysed the reduction of hydrogen peroxide, with a second-order rate constant of approx. 25 ± 10 M−1 s−1. Amperometric determination of H2O2 at −0.25 V gave a limit of detection (2 × noise) of 1.2 μM (sensitivity = 0.211 mA mM−1 cm−2 up to 2.0 mM), with a response time (steady-state) of 3 to 4 s. A 1 μM change in the O2 concentration gave approx. a 0.04% change in the H2O2 sensitivity. The presence of H2O-soluble copper-complexing anions at low concentrations gave a change in the H2O2 response. At higher anion concentrations (> 20 mM), the rate of electron transfer from the metal was faster than the rate of Cu(II) dissolution. A copper micro-band electrode was used to determine H2O2 in a mixture of glacial acetic acid and chloroform.

Assessment of photovoltaic pumping systems in Thailand - one decade experience

By mid 1999 nearly 1000 rural villages in Thailand have been installed with photovoltaic water pumping units. The cumulative wattage is close to 1 MWp. Over 80% are in the Northeast. We conducted a survey between 1995 and 1998 on 489 units, representing over 80% of the units installed then in that region. Interviews were conducted with 360 water users from 18 villages. The results indicate that 45% of the units have been damaged and broken down. Important sources of damages are motor/pump units (35%) and inverters (19%). Inappropriate siting, lack of adequate preparation of villagers and follow-ups by respective agencies are major factors contributing to the untimely damages and breakdown.

Modeling of Single Phase Inverter of Photovoltaic System Using System Identification

This paper proposes a new method to modeling a power inverter of grid-connected photovoltaic system by using a system identification approach. In this method, the system is considered as a black box of which it is not necessary to know structures and parameters inside. Modeling of one type of grid connected single phase inverter is carried out. Four linear models have been compared, i.e. an Autoregressive with Exogenous (ARX) model, an Autoregressive Moving Average with Exogenous (ARMAX) model, a Box-Jenkins (BJ) model an Output Error (OE) model. Four nonlinear models are studied, i.e, a Nonlinear Autoregressive with Exogenous (ARX) model, a Hammerstein model, a Wiener Model and a Hammerstein-Wiener Model. The best linear model is an Output Error model whereas the best nonlinear model is a Hammerstein-Wiener model with wavelet network estimators. Comparing modeling of the inverter by an Output-Error (OE) model and a Hammerstein-Wiener model, a Hammerstein-Wiener model is better because of its lower order and higher percentage of best fit.

Evaluation of fault contribution in the presence of PV grid-connected systems

An increasing number of distributed generations (DGs) being connected to the utility grid has raised the need for new and more rigorous standards for power quality, safety operation and islanding protection of the grid interconnection. This paper focuses on the fault contribution of a distributed generation, specifically PV grid-connected system in the event of an unintentional islanding. An experimental setup is created using an off-the-shelf grid-connected inverter to emulate the event of a fault occurred on a distribution feeder. An extreme case scenario, according to the IEEE standard, that will result in the highest fault contribution of the PV grid-connected system is considered for conservative results. The experimental results have shown that, without violating the specified criteria in the standard, the grid-connected inverter takes times to detect an islanding condition and stop energizing. The experimental results are used to investigate the fault contribution in a distribution system. This study has shown that higher penetration level of the PV grid-connected systems results in higher fault current which unavoidably has effects on the protective devices. This observation introduces the possibility of selecting and/or upgrading protective devices in a distribution system.

Metal-dispersed conducting polymer-coated electrode used for oxidase-based biosensors

Abstract The reduction current of H 2 O 2 which was generated by enzymatic reaction of glucose was measured at a microparticle-loaded polypyrrole film when glucose oxidase was in the solution or when it was immobilized in the film. This technique has the advantage of enabling detection at a low potential (0.0 V versus SCE). The current was measured at various thicknesses of the film, various concentrations of glucose and various potentials. The results were analyzed by use of previously derived diffusion-kinetic equations. It was found that the electrochemical reduction of H 2 O 2 was the rate-determining step and that the reaction occurred at the interface between the film and the solution.

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.

A microcontroller based islanding detection for grid connected inverter

This paper presents the development of a microcontroller based islanding detection for grid connected inverter with very simple under/over voltage and under/over frequency islanding detection algorithms. The system based on a microcontroller from Microchip Technology Inc. PIC family. A PIC microcontroller searches the under/over voltage and under/over frequency from utility grid and processed the value of voltage and frequency for turned on-off relay between grid connected inverter and utility grid.

CPLD-based islanding detection for mini grid connected inverter in renewable energy

This paper presents the development of a CPLD-based islanding detection for mini grid connected inverter in renewable energy with very simple under/over voltage and under/over frequency islanding detection algorithms. The system was implemented on a single XC9572 complex programmable logic device (CPLD) chip using schematic based and VHDL based synthesis model The CPLD monitor the under/over voltage and under/over frequency of utility grid and processed the value of voltage and frequency for turned on-off relay between mini grid connected inverter and utility grid.

Photovoltaic applications in Thailand: Twenty years of planning and experience

Abstract As at the end of 1996 about 2.5 MWp of PV panels have been installed in Thailand, mostly with Thai government budget. Major applications are publicly funded PV water pumping and battery charging systems in rural areas. A shift to private market applications through roof top grid-connected applications is envisaged in the coming decade.

Improving indoor conditions of a Thai-style mushroom house by means of an evaporative cooler and continuous ventilation

The paper discusses the effect of an evaporative cooling process and continuous ventilation for improving the indoor conditions of a conventional Thai-style mushroom house. A numerical model describing the behaviour of the Thai-style mushroom house model was developed. It was validated by comparing its output with that of the experiment of a small model of a mushroom house. It was found that the combination of evaporative cooling and continuous ventilation reduced the temperature and increased the relative humidity of air inside a mushroom house that is suitable for growing Lentinus.