Sudjito Soeparman

Performance Enhancement of Dye-Sensitized Solar Cells Using a Natural Sensitizer

Dye-sensitized solar cells (DSSCs) based on natural sensitizers have become a topic of significant research because of their urgency and importance in the energy conversion field and the following advantages: ease of fabrication, low-cost solar cell, and usage of nontoxic materials. In this study, the chlorophyll extracted from papaya leaves was used as a natural sensitizer. Dye molecules were adsorbed by TiO2 nanoparticle surfaces when submerged in the dye solution for 24 h. The concentration of the dye solution influences both the amount of dye loading and the DSSC performance. The amount of adsorbed dye molecules by TiO2 nanoparticle was calculated using a desorption method. As the concentration of dye solution was increased, the dye loading capacity and power conversion efficiency increased. Above 90 mM dye solution concentration, however, the DSSC efficiency decreased because dye precipitated on the TiO2 nanostructure. These characteristics of DSSCs were analyzed under the irradiation of 100 mW/cm2. The best performance of DSSCs was obtained at 90 mM dye solution, with the values of , , FF, and efficiency of DSSCs being 0.561 V, 0.402 mA/cm2, 41.65%, and 0.094%, respectively.

3D Numerical and Experimental Study on Paraffin Wax Melting in Thermal Storage for the Nozzle-and-Shell, Tube-and-Shell, and Reducer-and-Shell Models

Paraffin melting experienced in the nozzle-and-shell, tube-and-shell, and reducer-and-shell models in thermal storage with 3D numerical and experimental approach has been studied. The numerical study aims to evaluate the melting process and discover temperature distribution, liquid-solid interface, liquid fraction, and the average surface Nusselt number, while the aim of this experimental study is to determine the distribution of melting temperature. The comparison of temperature distribution between the numerical approach and experimental one indicates a good agreement. The comparison result between the three models shows that the melting process of the nozzle-and-shell model is the best, followed by tube-and-shell and reducer-and-shell models, successively. To finish the melting process, the time required is 6130 s for the nozzle-and-shell model, while tube-and-shell model requires 8210 s and reducer-and-shell model requires 12280 s.

Experimental Study of the Cross Flow Turbine

The experimental study was intended to investigate characteristics of the cross flow turbine based to the three models designed on the same runner diameter with different runner length of each. The Flow rates were measured by magnetic flow meter, the forces were detected by using spring balance and turbine speeds were detected by tachometer. The performance characteristics are shown by the relation of Power and efficiency versus jet entry arc, as well as the relation of Power and efficiency versus ratio between diameter and width of runner. The study indicated that the efficiency of the models were slightly difference, the highest efficiency indicated by the turbine with the ratio between length of runner and the diameter of the runner was 2; It was corresponding to the 75 degree entry arc.

Visualization of bubbles formation on the boiling process in tapering heat pipe with variation of evaporator to condenser diameter ratio

In the present study, a new tapering heat pipe design had been developed to enhance the thermal performances. Boiling visualization in the tapering heat pipe is investigated to provide the detailed information of bubbles nucleation. Experiment was conducted in the tapering heat pipe with variation of the evaporator (d) to condenser (D) diameter ratio. The values of d/D are varied at 1/1; 1/2; 1/3 and 1/4. Heat load was generated at the evaporator section using heater DC-Power supply at 30, 40 and 50 Watt. The visualization technique was developed by using a transparent glass tube and the images of boiling bubbles were captured by SLR camera. The glass tube inclination is 45 o and integrated with the NI-9211 and c-DAQ 9271 module. K-type thermocouple was set at the evaporator and condenser sections for measurement of boiling temperatures in the tapering heat pipe. Based on the results, it can be noted that variations of heat load and diameter ratio (d/D) of the evaporator and condenser affect the size and shape of boiling bubbles, as well as the nucleation temperature on the tapering heat pipe. The heat transfer coefficient tends to increase at a heat load of 50 W and diameter ratio d/D=1/4.

Increased Melting Heat Transfer in the Latent Heat Energy Storage from the Tube-and-Shell Model to the Combine-and-Shell Model

The melting of paraffin in thermal storage tube-and-shell and combine-and-shell models was conducted with the numerical research aim of decreasing the charge time through changing the shape of the tube into combining form. The results discussed are temperature contour, liquid-solid interface contour, temperature distribution, liquid fraction, and the average Nusselt number. The results show that the charge time in the tube-and-shell model is 2000 s, while the combine-and-shell model is 1200 s, meaning an overall decrease in charge time in the combine-and-shell model by 40% when compared to that of the tube-and-shell model.

Performance Analysis of a Combined Blade Savonius Wind Turbines

The Savonius wind turbine has a lower performance than other types of wind turbines which may attract more study focus on this turbine. This study aimed to improve wind turbine performance by combining a conventional blade with an elliptical blade into a combined blade rotor. The analysis was performed on three blade models in computational fluid dynamics (CFD) using ANSYS_Fluent Release 14.5. Then the results were verified experimentally using an open wind tunnel system. The results of the numerical simulation were similar to the experimental and showed that the combined blade rotor has better dragging flow and overlap flow than the conventional and elliptical blade. Experimental verification showed that the combined blade was to increase the maximum coefficient of power (Cpmax.) by 11% of the conventional blade and to 5.5% of the elliptical blade.

Performance enhancement of dye-sensitized solar cells (DSSCs) using a natural sensitizer

Dye-sensitized solar cells (DSSCs) based on natural sensitizers have become a topic of significant research because of their urgency and importance in the energy conversion field and the following advantages: ease of fabrication, low-cost solar cell, and usage of nontoxic materials. The natural sensitizer in DSSCs is responsible for the absorption of light as well as the injection of charges to the conduction band of the semiconductor such as TiO2 nanoparticles. In this study, the chlorophyll extracted from papaya leaves was used as a natural sensitizer. Dye molecules were adsorbed by TiO2 nanoparticle surfaces when submerged in the dye solution for 24 h. The concentration of the dye solution influences both the amount of dye loading and the DSSC performance. The amount of adsorbed dye molecules by TiO2 nanoparticle was calculated using a desorption method. As the concentration of dye solution was increased, the dye loading capacity and power conversion efficiency increased. Above 90 mM dye solution conce...

A simulation for predicting potential cooling effect on LPG-fuelled vehicles

Liquefied Petroleum Gas vehicles (LPG Vehicles) provide a potential cooling effect about 430 kJ/kg LPG consumption. This cooling effect is obtained from the LPG phase change from liquid to vapor in the vaporizer. In the existing system, energy to evaporate LPG is obtained from the coolant which is circulated around the vaporizer. One advantage is that the LPG (70/30 propane / butane) when expanded from 8 bar to at 1.2 bar, the temperature is less than −25 °C. These conditions provide opportunities to evaporate LPG with ambient air flow, then produce a cooling effect for cooling car’s cabin. In this study, some LPG mix was investigated to determine the optimum condition. A simulation was carried out to estimate potential cooling effects of 2000 cc engine from 1000 rpm to 6000 rpm. In this case, the mass flow rate of LPG is a function of fuel consumption. The simulation result shows that the LPG (70/30 propane/butane) provide the greatest cooling effect compared with other mixtures. In conclusion, the 2000 cc engine fueled LPG at 3000 rpm provides potential cooling effect more than 1.3 kW, despite in the low engine speed (1000 rpm) only provides about 0.5 kW.Liquefied Petroleum Gas vehicles (LPG Vehicles) provide a potential cooling effect about 430 kJ/kg LPG consumption. This cooling effect is obtained from the LPG phase change from liquid to vapor in the vaporizer. In the existing system, energy to evaporate LPG is obtained from the coolant which is circulated around the vaporizer. One advantage is that the LPG (70/30 propane / butane) when expanded from 8 bar to at 1.2 bar, the temperature is less than −25 °C. These conditions provide opportunities to evaporate LPG with ambient air flow, then produce a cooling effect for cooling car’s cabin. In this study, some LPG mix was investigated to determine the optimum condition. A simulation was carried out to estimate potential cooling effects of 2000 cc engine from 1000 rpm to 6000 rpm. In this case, the mass flow rate of LPG is a function of fuel consumption. The simulation result shows that the LPG (70/30 propane/butane) provide the greatest cooling effect compared with other mixtures. In conclusion, the 2000 ...

Study on Characteristics of Ricinoleic Acid as a Phase Change Material

Today the use of fatty acids as heat storage substance is growing. The use of several types of fatty acids such as oleic acid, palmitic acid, and stearic acid as heat storage materials has been studied. But, ricinoleic acid from castor oil has not been studied yet. This study was conducted to ascertain the characteristics of ricinoleic acid as a heat storage material.Methyl ricinoleic was obtained through transesterification of castor oil by methanol with sodium methoxide catalyst. Methyl ricinoleic was then hydrolyzed using sodium hydroxide in ethanol to produce ricinoleic acid. Ricinoleic acid was identified by FTIR (Fourier Transform Infrared Spectrophotometer) test standard ASTM E 1252-07 and its chemical composition was determined by Gas Chromatography-Mass Spectrometry (GC-MS). The identification of the type, amount, and environment of hydrogen in the compound was determined by Nuclear Magnetic Resonance (NMR). The analysis on characteristics, that is, transition and melting temperatures of material was performed by DSC (Differential Scanning Calorimetry) test standard ASTM D 3419-08.Based on the results of FTIR, GC-MS, 1H-NMR, dan 13C-NMR tests, the spectra that were obtained indicated that the test substances were methyl and ricinoleic acid 70.349%. And, the results of DSC tests indicated that the characteristics of ricinoleic acid absorbed and released latent heat at the temperature from 8.58°C and absorbed sensible heat at the temperature from-7.17°C to 8.58°C.

Simulation Savonius Wind Turbine with Multi-Deflector

This paper aims to study the windmill Savonius with multi-deflector. Multi-deflector placed around the windmill, which aims to reduced negative torque to the returning blade and directing the flow of wind to the advancing blade . CFD analysis with ANSYS software. The initial conditions with variation wind speeds 3, 4, 5 and 6 m / s. The result indicated by velocity distribution at positions 00, 450, 900 and 1350. The largest static torque occurs at position 450 caused by the greater the Coand-like flow, dragging flow and overlap flow. The greater the static torque that occurs with increasing wind speeds.