Sukruedee Sukchai

Design and Implementation of an Interleaved Boost DC-DC Converter for PEM Fuel Cells

This paper elaborates a design and implementation of a 2-phase interleaved boost DC-DC converter as the power conditioning circuit for PEM fuel cells. The converter ripple current is analyzed so as to determine the inductance value, which would draw the fuel cell ripple current less than 4 % of its nominal value for a longer lifetime and efficient operation. Compact design is benefited from reduced inductor core volume due to paralleled connection as well as microprocessor-based control. Practical implementation is also discussed. Selection of simulation and experimental results is presented to validate the design methodology. The converter has the maximum output power of 1 kW at the output voltage of 120 V with the efficiency better than 92 %.

Investigation on Thermal Absorptivity of PCM Matrix Material for Photovoltaic Module Temperature Reduction

Photovoltaic (PV) system experience challenges from module temperature (Tmod) increasing particularly due to stagnation of thermal energy (TE) on its surface. Efforts to reduce the Tmod is widely experimented in many ways, like incorporating latent heat storage material (PCM) with PV module to reduce the Tmod through radiation and convection heat transfer. This paper focuses on selecting of an effective thermal absorption material for the fabrication of PCM matrix and optimization of the critical spacing between the PV module and PCM matrix. The thermal absorptivity of Aluminum (Al) and Copper (Cu) were analyzed with and without coated absorber at different spacing conditions. It was observed that Al tube matrix with coated absorber was absorbed 3.0 °C more than copper at 6 mm distance from module. Hence further studies on the Tmod reduction will be effective with the use of Al as PCM matrix tube.

Characterization and Spectral Selectivity of Sn-Al2O3 Solar Absorber

In present work, tin-pigmented alumina (Sn-Al2O3) solar absorber on the aluminium substrate was successfully prepared by anodic anodization and further characterized by different methods. The phase, morphology, reflectance (R) and thermal conductivity of the Sn-Al2O3 solar absorber were measured by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) equipped with energy dispersive X-ray (EDX) analyzer, and Ultraviolet-visible-near infrared spectrophotometer in the wavelength of 300-2500 nm. The solar absorptance (α) was calculated based on the relationship of the spectral reflectance, R(λ), and the solar spectral irradiance of AM 1.5, Is(λ), in the wavelength interval of 300-2500 nm. As the results, the surface color of the Sn-Al2O3 film was dark-black color. The XRD pattern of Sn-Al2O3 films was indexed as aluminium and tin phases. The chemical composition of the Sn-Al2O3 films composed of tin (Sn), aluminum (Al) and oxygen (O) elements. The average thickness of the produced films was 18.9 μm. It was found that Sn-Al2O3 films showed the low R (0.09) and high α (0.93) values for the whole wavelength 300-2500 nm, corresponding to theoretical properties of the solar absorber. Therefore, it can be concluded that the Sn-Al2O3 film on aluminium substrate can be applied to be the solar absorber in solar collector due to high α, which is similar to the commercial solar absorbers.

Energy and Exergy Analysis of Thermal Energy Storage Prototype by Using Concrete Material in Thailand

The research was performed on thermal energy storage prototype in Thailand. Concrete was used as the solid media sensible heat material in order to fulfill local material utilization which is easy to handle and low cost. Saturated steam was used for heat transfer fluid. The thermal energy storage prototype was composed of pipes embedded in a concrete storage block. The embedded pipes were used for transporting and distributing the heat transfer medium while sustaining the pressure. The heat exchanger was composed of 16 pipes with an inner diameter of 12 mm and wall thickness of 7 mm. They were distributed in a square arrangement of 4 by 4 pipes with a separation of 80 mm. The storage prototype had the dimensions of 0.5 x 0.5 x 4 m. The charging temperature was maintained at 180°C with the flow rates of 0.009, 0.0012 and 0.014 kg/s whereas the inlet temperature of the discharge was maintained at 110°C. The performance evaluation of a thermal energy storage prototype was investigated in the part of charging/discharging. The experiment found that the increase or decrease in storage temperature depends on the heat transfer fluid temperature, flow rates, and initial temperature. The energy efficiency of the thermal energy storage prototype at the flow rate of 0.012 kg/s was the best because it dramatically increased and gave 41% of energy efficiency in the first 45 minutes after which it continued to rise yet only gradually. Over 180 minutes of operation time, the energy efficiency at this flow rate was 53% and the exergy efficiency was 38%.

Comparative Analysis of Exergy and Efficiency for Stratified Thermal Storage Tank with Solar Flat Plate and Evacuated Tube Collectors

In recent years, solar water heating technology has got the major importance in water heating applications. For the efficient and effective working of solar water heaters, storage of the hot water is the main issue in this water heating technologies. This paper mainly presents the exergy and efficiency comparison between the solar flat plate water heater and evacuated tube water heater. A five level stratified thermal storage tank is designed and developed for this analysis. At each level of the tank, temperature of the water is collected for each one hour interval from 9:00 to 16:00 hours in both cases and the overall exergy and efficiency of the two water heaters were calculated. The average efficiency of all the levels for flat plate and evacuated tube collectors are 7.91% and 8.20% respectively. The overall system efficiency is obtained as 39.54% for flat plate and 41.00% for evacuated tube solar collector. At each level exergy is calculate for both systems and the average exergy of all the levels for flat plate collector is 4.243 kW and for evacuated tube solar collector is 4.371 kW.