Phase Transformations in Mn–Al and Mn–Bi Magnets by Repeated Heat Treatment

Transactions of the Indian Institute of Metals - A stepped heating cycle in a tube furnace at 1000 °C for 1 h followed by holding at 400 °C for 1 h...     

Optimization of key factors affecting hydrogen production from food waste by anaerobic mixed cultures

Key factors (inoculums concentration, substrate concentration and citrate buffer concentration) affecting hydrogen yield (HY) and specific hydrogen production rate (SHPR) from food waste in batch fermentation by anaerobic mixed cultures were optimized using Response Surface Methodology with Central Composite Design. The experiments were conducted in 120 ml serum bottles with a working volume of 70 mL. Under the optimal condition of 2.30 g-VSS/L of inoculums concentration, 2.54 g-VS/L of substrate concentration, and 0.11 M of citrate buffer concentration, the predicted maximum HY and SHPR of 104.79 mL H₂/g-VS_added and 16.90 mL H₂/g-VSS.h, respectively, were obtained. Concentrations of inoculums, substrate and citrate buffer all had an individual effect on HY and SHPR (P < 0.05). The substrate concentration and citrate buffer concentration had the greatest interactive effect on SHPR (P = 0.0075) while their effects on HY (P = 0.0131) were profound. These results were reproduced in confirmation experiments under optimal conditions and generated an HY of 104.58 mL H₂/g-VS_added and an SHPR of 16.86 mL H₂/g-VSS.h. This was only 0.20% and 0.24%, respectively, different from the predicted values. Microbial community analysis by PCR-DGGE indicated that Clostridium was the pre-dominant hydrogen producer at the optimum and worst conditions. The presence of Lactobacillus sp. and Enterococcus sp. might be responsible for the low HY and SHPR at the worst condition.     

Implementation and Analysis of Electricity Generation by Thermoelectric

This paper presents an implementation and analysis of producing electricity by thermoelectric principle. The paper describes an experimental thermoelectric prototype to investigate the electric generation. Firstly, the appropriated design of the thermoelectric unit is constructed as a laboratory prototype to measure performance of the electricity generated under the condition of on-load and no-load. All parameters are recorded such as voltage (V), current (A), and both sides temperature range (ΔT). Secondly, the power output of the prototype is analyzed. The experimental, results shows that while no-load temperature range (ΔT) from 0 – 110°C, the output voltage (V) was up to 1.17 V at 110 °C and with 2 Ω-loads the output current (I), voltage (V), and power (W) were 212.6 mA, 0.850 V and 180.71 mW respectively. For 10 thermoelectric source connected in series, while no-load and 2 Ω-loads, the output voltage (V) was at maximum of 13.57 V and minimum of 1.213 V at 110 °C. This can be seen that the voltage output from the power output is fluctuated. Therefore a proper design of buck-boost converter is necessary to stabilize the output voltage for purpose of charging battery application.     

System performance of a three-phase PV-grid-connected system installed in Thailand: Data monitored analysis

PV-grid-connected systems are worldwide installed because it allows consumer to reduce energy consumption from the electricity grid and to feed the surplus energy back into the grid. The system needs no battery so therefore the system price is very cheap comparing to other PV systems. PV-grid-connected systems are used in buildings that already hooked up to the electrical grid.Finding efficiency of the PV-grid-connected system can be done by using a standard instrument which needs to disconnect the PV arrays from the grid before measurement. The measurement is also difficult and we lose energy during the measurement.This paper will present the system performance of a PV-grid-connected system installed in Thailand by using a monitoring system. The monitored data are installed by acquisition software into a computer. Analysis of monitored data will be done to find out the system performance without disconnecting the PV arrays from the system. The monitored data include solar radiation, PV voltage, PV current, and PV power which has been recorded from a 5 kWp system installed of amorphous silicon PV at Rajamangala University of Technology Suvarnabhumi, Nonthaburi, Thailand. The system performance of the system by using the data monitored is compared to the standard instrument measurement. The paper will give all details about system components, monitoring system, and monitored data. The result of data analysis will be fully given.     

A Modified-Simplified MPPT Technique for Three-Phase Single-State Grid-Connected PV Systems

Nowadays, the single state inverter for the grid-connected photovoltaic (PV) systems is becoming more and more popular as they can reduce circuit complexity resulting in less power losses of the inverter. This paper focuses on the use of model predictive control (MPC) to control a 3-phase and 2-level single-state grid-connected inverter in order to regulate the PV maximum power point (MPP). The algorithm of MPC scheme was done to measure the simultaneous current signal including predicting the next sampling current flow. The reference current (I_d*) was used to control the distribution of electrical power from the solar cell to the grid. To be able to control the maximum power point tracking (MPPT) when the sunlight suddenly changes, so that a developing MPPT based on estimation current perturbation and observation (ECP&O-MPPT) technique was used to control the reference current. This concept was experimented by using MATLAB/Simulink software package. The proposed technique was tested and compared with the old technique. The simulation results showed that the developed MPPT technique can track the MPP faster when the light changes rapidly under 1,000 W/m², 25°C standard climatic conditions. The MPPT time was 0.015 s. The total harmonic distortion (THD) was 2.17% and the power factor was 1.     

Non-sterile bio-hydrogen fermentation from food waste in a continuous stirred tank reactor (CSTR): Performance and population analysis

Bio-hydrogen production from food waste by anaerobic mixed cultures was conducted in a continuous stirred tank reactor (CSTR). The hydraulic retention time (HRT) was optimized in order to maximize hydrogen yield (HY) and hydrogen production rate (HPR). The maximum hydrogen content (38.6%), HPR (379 mL H₂/L. d) and HY (261 mL H₂/g-VS_added) were achieved at the optimum HRT of 60 h. The major soluble metabolite products were butyric and acetic acids which indicated a butyrate-acetate type fermentation. Operation of CSTR at HRT 60 h could select hydrogen producing bacteria and eliminate lactic acid bacteria and acetogenic bacteria. The microbial community analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that the predominant hydrogen producer was Clostridium sp.     

Enhanced bio-hydrogen production from sugarcane juice by immobilized Clostridium butyricum on sugarcane bagasse

Immobilized Clostridium butyricum TISTR 1032 on sugarcane bagasse improved hydrogen production rate (HPR) approximately 1.2 times in comparison to free cells. The optimum conditions for hydrogen production by immobilized C. butyricum were initial pH 6.5 and initial sucrose concentration of 25 g COD/L. The maximum HPR and hydrogen yield (HY) of 3.11 L H₂/L substrate·d and 1.34 mol H₂/mol hexose consumed, respectively, were obtained. Results from repeated batch fermentation indicated that the highest HPR of 3.5 L H₂/L substrate·d and the highest HY of 1.52 mol H₂/mol hexose consumed were obtained at the medium replacement ratio of 75% and 50% respectively. The major soluble metabolites in both batch and repeated batch fermentation were butyric and acetic acids.