Roongrojana Songprakorp

Multi-Layered TiO2 Films towards Enhancement of Escherichia coli Inactivation

Crystalline TiO2 has shown its great photocatalytic properties in bacterial inactivation. This work presents a design fabrication of low-cost, layered TiO2 films assembled reactors and a study of their performance for a better understanding to elucidate the photocatalytic effect on inactivation of E. coli in water. The ability to reduce the number of bacteria in water samples for the layered TiO2 composing reactors has been investigated as a function of time, while varying the parameters of light sources, initial concentration of bacteria, and ratios of TiO2 film area and volume of water. Herein, the layered TiO2 films have been fabricated on the glass plates by thermal spray coating prior to screen printing, allowing a good adhesion of the films. Surface topology and crystallographic phase of TiO2 for the screen-printed active layer have been characterized, resulting in the ratio of anatase:rutile being 80:20. Under exposure to sunlight and a given condition employed in this study, the optimized film area:water volume of 1:2.62 has shown a significant ability to reduce the E. coli cells in water samples. The ratio of surface area of photocatalytic active base to volume of water medium is believed to play a predominant role facilitating the cells inactivation. The kinetic rate of inactivation and its behavior are also described in terms of adsorption of reaction species at different contact times.

Impact of photovoltaic grid-connected power fluctuation on system frequency deviation in contiguous power systems

In this paper, a power system with an automatic generation control (AGC) in two contiguous areas are studied to demonstrate speed deviation of a generator due to photovoltaic (PV) power fluctuation in both time and frequency domains. The system is linearized and modeled in state-space representation. The change of the PV power is defined as the input of the system, and the change of speed deviation is defined as the output of the system. The analysis using a unit step function input illustrates that increased change of PV power can affect the speed deviation of generators. Changed PV power on another side can lower overshoot of the change of speed deviation in the study area. Moreover, the system is excited with the sinusoidal waveform input signal imposed on dc signal, and with the scaled solar irradiance data, respectively. In the case of using sinusoidal waveform input, the results show that the magnitude of change of speed deviation can be a function of amplitude and frequency, but is not a function of biasing. In case of the system which has been inputted by using scaled solar datasets, the changes of the speed deviation are observed when the PV power fluctuation occurs.

Experimental Study of Heat Transfer in Soil to Inhibit Microbial Growth Using the Underground Release of Hot Water and a Hydraulic Head Method

ABSTRACT This research aimed to study the effectiveness of heat transfer in soil using the underground release of hot water with a hydraulic head. Pressure heads of 1.0, 1.5 and 2.0 m were utilized for underground release with a nozzle to investigate heat transfer in soil necessary to inhibit microbial growth through underground hot water release using a pressure head of liquid. The nozzle was made of stainless steel pipe (SUS304). The proposed system was designed to inhibit microbes of Ralstonia solanacearum with a hot water volume flow of 300, 400 and 500 ml min−1, while temperature was kept constant at 70 ºC. The hot water released underground provided higher soil temperature with shorter working time. The research found that the number of layers and diameter of drilled holes had a significant effect on soil temperature distributed at various depth levels (y-plan), resulting in enhanced performance (100%) for the inhibition of microbes in an x-plan radius of 15 cm for a shorter time of 20–30 min with one nozzle.

PV industry growth and module reliability in Thailand

The PV applications in Thailand are now installed more than 1.2 GWp cumulatively. It is due to the National Renewable Energy Program and its targets. In the latest Alternative Energy Development Plan (AEDP), the PV electricity production target has increased from 2 GWp to 3 GWp. With this rapid growth, customers and manufacturers seek for module standard testing. So far over one thousands of PV modules per annum have been tested since 2012. The normal tests include type approval test according to TIS standard, acceptance test and testing for local standard development. For type test, the most module failure was found during damp heat test. For annual evaluation test, the power degradation and delamination of power was found between 0 to 6 percent from its nameplate after deployment of 0 to 5 years in the field. For thin-film module, the degradation and delamination was found in range of 0 to 13 percent (about 5 percent on average) from its nameplate for the modules in operation with less than 5 years. However, for the PV modules at the reference site on campus operated for 12 years, the power degradation was ranging from 10 to 15 percent. Therefore, a long term performance assessment needs to be considered to ensure the system reliability.

Investigation of power values of PV rooftop systems based on heat gain reduction

PV rooftop system can generally be installed to produce electricity for the domestic house, office, small enterprise as well as factory. Such a system has direct useful for reducing peak load, meanwhile it also provides shaded area on the roof and hence the heat gain into the building is reduced. This study aims to investigate the shading effect on reduction of heat transfer into the building. The 49 kWp of PV rooftop system has been installed on the deck of the office building located in the middle of Thailand where the latitude of 14 ° above the equator. The estimation of heat gain into the building due to the solar irradiation throughout a day for one year has been carried out, before and after the installation of the PV rooftop system. Then the Newton’s law of cooling is applied to calculate the heat gain. The calculation and the measurement of the heat reduction are compared. Finally, the indirect benefit of the PV rooftop system installed is evaluated in terms of power value.

Effect of Solar Concentrator System on Disinfection of Soil-Borne Pathogens and Tomato Seedling Growth

The development of non-imaging reflectors for circular-cylindrical solar energy receivers has consisted primarily of investigations on symmetrical V-trough and compound parabolic concentrator (CPC) designs, with the latter being favoured recently because of its superior optical collection. However, it has since been realised that asymmetrical versions of such reflectors may be developed and that they have their own limits of concentration and ideality. It was shown that ideal asymmetrical reflectors could achieve substantially greater peak concentration than symmetrical reflectors of the same acceptance angle (Mills and Giutronich, 1979). An important difference, however, is that the performance of the asymmetrical reflector is much higher at one solstice than another because the aperture is adjusted with respect to the acceptance angle envelope. With an asymmetrical collector, the possibility is presented of at least partial bias of the seasonal collector output toward the maximum load period. Such a bias would reduce dumped solar energy in low load periods, allowing a larger usable solar fraction of energy supplied. Phitthayarachasak (Phitthayaratchasak et al., 2005) upgraded the solarization system process to increase its efficiency by applying the asymmetrical compound parabolic concentrator (ACPC) to enable the concentration of more solar radiation by an average of up to 2.5 times. It is convenient to operate because there is no need to adjust the angle of the ACPC unit according to the movement of the sun. The result showed that the soil temperatures at various depths were high enough to inhibit the growth of microbes within a 5 day period. The solarization operating time was distinctly decreased. The solarization system is then a suitable process for destroying or inhibiting the growth of soil microbes which cause plant diseases (Burrafato, 1998; Le Bihan et al., 1997; Bell; 1998). Even though this system is easy to conduct, with less cost, and no pollution, it still needs 4–6 weeks to operate. Therefore, in this study, the CPC combined with an ACPC unit was developed in order to decrease the time for soil microbe inhibition to be closer to the time of traditional steaming methods.