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This research focused on modelling process and thermal efficiency analysis by using exergy analysis, for Brayton Recompression Cycle with supercritical carbon dioxide (CO2) as the working fluid for the generation of electrical energy. Recently, the recompression sequence was developed into a supercritical CO2 pilot power plant with a capacity of 252 kW by Sandia National Laboratories. Software of Aspen HYSYS is used for the modelling process and the efficiency identification method was carried out by the exergy analysis of the cycle from the data of pilot plant developed by Sandia National Laboratories. Exergy analysis is used for identifying location the occurs of heat loss (exergy destruction). Based on the pilot plant data, we design larger capacity supercritical CO2 power plant with a capacity of 10 MW and analyses the economic feasibility based on capital expenditure (CAPEX) and operational expenditure (OPEX). The modelling results are validated and have an offset of 5% from the actual data. The results of the exergy analysis show that the largest heat loss occurs in the HTR (High Temperature Recuperator) device, which is 62.9 kW or 15.2% of the available exergy. The overall exergy efficiency of the cycle is 237.1 kW or 57.3% of the available exergy. From the economic feasibility study, it shows the value of 37 million USD for CAPEX and 3.7 million USD for OPEX per year. [ABSTRACT FROM AUTHOR]

Indonesia has the largest geothermal potential in the world, recently Indonesia only utilizes 7% of their geothermal to generate electricity. To increase the electricity production, the development of new geothermal power plant is needed, also the optimization of existing geothermal power plant. There are several types of geothermal powerplant system, depends on steam condition and utilization. This paper aimed to analyze the heat loss occurred in geothermal powerplant system X, also compare the cooling system between direct contact condenser (DCC) and indirect contact condenser (ICC). The comparison study has been simulated by using ASPEN HYSIS software. The method used to analyze the heat loss was by calculating exergy in each stream, so that we can calculate the exergy destruction at each process equipment. The result shows that the turbine produced 60 MW of electricity and largest heat loss occur on cooling tower with percentage about 17.64% for ICC system and 18.41% for DCC. [ABSTRACT FROM AUTHOR]

Aurum and argentum are the most useful metal of all the minerals mined from the Earth. Both of them are noble metal. This research verify the aurum's nobleness compared with argentum based on the adsorption energy of hydrogen atom on the metal surfaces. The adsorption energy can be obtained by studying a simple surface reaction, the adsorption of molecule hydrogen on the metal surfaces. The calculation of adsorption energy was done computationally based on Density Functional Theory. This research found that aurum has the most positive adsorption energy compared with argentum. The more positive the adsorption energy, the harder it will be for hydrogen atom to adsorp to the surface. This result indicates that aurum is more noble than argentum. [ABSTRACT FROM AUTHOR]

Widely used of plastic material regularly produce ecological and environmental issues due to increased number of wastes. Recycle process is an alternative to overcome the plastic waste issues. Effect of using recycled plastic material is molecular structure changes that will affect to its physical and mechanical properties. The melt flow rate's (MFR) materials properties are closely related to the production of plastic products, especially to determine the type of forming process and temperature setting of each material. This study aims to determine the effect of the frequency of recycling on the flow rate properties of Trilene HI 10HO Polypropylene (PP) plastic materials using experimental methods. Based on analysis, the MFR value of recycled polypropylene material has increased as the frequency of recycling is increased. The MFR value did not change much until the 2nd recycling process, but it's changed drastically at the 3rd and 4th recycling process and the MFR value increased 4 times compared to the virgin material. And on the 6th recycling process, the MFR value increased up to 7 times. In addition to changes in the MFR value, recycled materials also have a darker color shift. [ABSTRACT FROM AUTHOR]

Lithium containing manganese and nickel in the form of LiNi0.5Mn1.5O4 (LNMO) as cathode material for Li-ion battery was synthesized with addition of yttrium (Y) as doping element. Characterization and analysis were emphasized to study the effect of Y addition to the crystal structure of LNMO. X-ray diffraction (XRD) technique was employed to obtain diffraction pattern and the crystal structure was determined by using Rietveld analysis. The results shows that LNMO with Y=0 fit with space group Fd-3m with some LixNi1-xO detected as impurities. The addition of Y=0.05 mol and Y=0.1 mol resulted in the change of structure to space group P4332 marked with the emergence of some superstructure diffraction peaks. Yttrium was confirmed to enter 4b site co-existed with Ni and this result is closely related to the increase in lattice parameters of LNMO and crystal unit volume with increasing Y addition. The addition of Y is liable to the formation of more stable (Ni,Y)O6 and MnO6 octahedra and whole crystal structure. The result from this study is important to determine and understand the relationship between structure and physical properties of LNMO with Y doping in order to improve electrochemical performance as cathode material in Li-ion battery. [ABSTRACT FROM AUTHOR]

LiMn1.5Ni0.5O4 samples for lithium-ion battery cathode materials were synthesized by two-step precursors mixing assisted with a sonochemical method. Lithium hydroxide, manganese acetate tetrahydrate, and nickel acetate tetrahydrate were used as the precursors. One and two-step precursor mixing was carried out using high-intensity ultrasonic Ti-horn (20 kHz, 750 watts) in distilled water. The one-step sample was prepared by mixing lithium hydroxide, manganese acetate tetrahydrate, and nickel acetate tetrahydrate together in a molar ratio of 2:3:1 in the distilled water and applying the sonification. While the two-step one was prepared by mixing manganese acetate and nickel acetate together in a molar ratio of 3:1 priorly, to obtain a mixed Ni-Mn oxide, and then lithium hydroxide powder was added into the dried mixture. After sufficiently drying at 150℃ the mixtures were then calcinated and sintered for 10 hours at 400 and 800℃, respectively. The sample structures were characterized by X-ray diffraction (XRD), while the properties were analyzed using electrochemical measurements. The XRD results indicate that both synthesized LiNi0.5M1.5O4 samples have cubic spinel structures. The two-step sample has lower purity and conductivity. However, the charge and discharge properties show that the two-step sample has a lower specific capacity but higher cyclability. [ABSTRACT FROM AUTHOR]