Hydrogen and Syngas Production from Gasification of Lignocellulosic Biomass in Supercritical Water Media

Novel biomass-processing technologies have been recently used for conversion of organic wastes into valuable biofuels like bio-hydrogen. Agricultural wastes are available and renewable energy resources to supply energy demand of the future. The purpose of this study is to investigate the production of hydrogen-rich syngas from wheat straw, walnut shell, and almond shell

Performance Analysis of Six Electro-Optical Crystals in a High-Bandwidth Traveling Wave Mach-Zehnder Light Modulator

In this study, a traveling wave Mach-Zehnder intensity modulator (TW-MZM) was designed and optimized for six different electro-optical (EO) crystals: lithium niobate (LNB), potassium niobate (KNB), lithium titanate (LTO), beta barium borate (BBO), cadmium telluride (CdTe), and indium phosphide (InP). The performance of each EO crystal, including optical and radio frequency (RF) loss, applied voltage, and modulation bandwidth, was estimated and compared. The results suggest that, in theory, KNB, LTO, BBO, and CdTe have the potential to outperform LNB. However, it should be noted that the loss associated with KNB and LTO is comparable to that of LNB. The findings demonstrated that BBO and CdTe exhibit a modulation bandwidth exceeding 100 GHz and demonstrate the lowest loss among the considered crystals based on the assumed geometry

Variable flow and optimization of chiller loading effect on energy saving for screw vapor compression-single effect absorption hybrid chiller plant in hospital mechanical room ‒ case study: Tehran heart hospital

Chiller plants are the most energy consuming system during summer season in residential, commercial and hospital buildings. The highly variable cooling demand of the buildings connected to a hybrid chiller plant included absorption and vapor compression chillers to achieve higher energy efficiencies is one of the important issues. Cooling load sharing strategies and apply the variable water flow system in chiller plant have a significant impact on energy consumption and consequently with more productivity and environmentally protected. This paper examines the behavior and pattern of energy consumption in a hybrid chiller plant that includes a combination of two air-cooled screw vapor compression and three single effect absorption chillers. In order to properly understand the pattern of energy consumption, an existing mechanical room in a hospital in Tehran has been studied for five months, and its energy consumption has been compared with the optimized model. The results indicate that the sequence of the chiller function and the way in which they are placed in the circuit during a partial load, is in highest importance in view point of energy saving also by Applying of variable water flow system for optimized chiller loading the more energy saving is achieved for hybrid absorption and vapor compression chiller plant

Determining the Quadratic Electro-Optic Coefficients for Polycrystalline Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) Using a Polarization-Independent Electro-Optical Laser Beam Steerer

A polarization-independent electro-optical (EO) laser beam steerer based on a bulk relaxor ferroelectric polycrystalline Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) was developed in this study to steer light ranging from visible to mid-IR wavelengths. A large number of the resolvable spots was achieved with this EO steerer. A Fourier-transform infrared (FTIR) spectroscopy was employed to determine the refractive index of the polycrystalline PMN-PT over a wide range of optical wavelengths. Besides measuring the transmission of this material, the capacitance bridge analysis was used to characterize the effect of temperature on the dielectric constant of PMN-PT. The performance of the steerer over a variety of wavelengths was simulated using COMSOL Multiphysics. The deflection angle for the wavelengths of 532, 632.8, 1550, and 4500 nm was measured in the lab in terms of mrad.mm/kV at two different temperatures and compared to the simulation results. The quadratic Kerr electro-optic coefficient and the halfwave electric field were determined for those four wavelengths at two different temperatures. The results showed polycrystalline PMN-PT has a large quadratic EO coefficient for visible light, almost as large in the near IR, but drops significantly in the mid-IR. No significant temperature dependency for the EO coefficients was observed for any of those four wavelengths

Modeling and Optimization of R-717 and R-134a Ice Thermal Energy Storage Air Conditioning Systems Using NSGA-II and MOPSO Algorithms

In this study, an Ice Thermal Energy Storage (ITES) is integrated to an office building air-conditioning system as a full load storage system. The R-134a and R-717 refrigeration systems by exergy, economic and environmental considerations are modeled and investigated separately. Two multi-objective optimization algorithms: Non-dominated Sorting Genetic Algorithm-II (NSGA-II) and Multi-Objective Particle Swarm Optimization (MOPSO), are engaged to obtain the optimal design parameters which lead to the optimal objective functions, exergy efficiency and total cost rate. The optimum point from Pareto frontier of each optimization algorithm is selected for both refrigerants by using TOPSIS decision making method, and energy demand of the new system is compared to the conventional one. The results indicated that by using NSGA-II and MOPSO algorithms for the R-717 refrigerant based system, the optimum design parameters lead to electricity consumption decrease by 11% and 8% more than R-134a refrigerant based system, respectively. Furthermore, the results showed that NSGA-II is more capable to achieve more effective solutions. At the optimum point of NSGA-II for R-717 based system, the exergy efficiency and total cost rate are 49% and 255USDh−1 respectively. While the annual CO2 emission is 11% lower than the R-134a based system

The Potential of Wind for Energy Production and Water Pumping in Saravan County

Sustainable sources of energy are vital for energy production in remote areas which have difficult access to electricity and grid. Thus, in this paper an initial evaluation of wind resource for over 18 months was done to evaluate the potential of wind energy as a power generation source in a remote village in Saravan county, southeastern Iran. The Weibull distribution is employed to model the wind data at three heights: 10, 30 and 40 meters. The Weibull distribution presented in this study indicates a good compatibility with the measured wind data. Different wind speed parameters such as monthly and diurnal wind speed profiles at different heights, wind direction, turbulence intensity, and etc. have been estimated and analyzed. The results showed the studied site has not the sufficient wind speed and power for development of commercial wind power plants. But the studied site may be suitable for development of small and residential wind turbines. Therefore in the next part of study, energy production of different small wind turbines has been estimated. It was concluded that one of the small wind turbines which has the highest net energy production of 33,685 kWh/ yr and highest capacity factor of 25.6% can be suitable for non-grid connected electrical and mechanical applications, such as local consumption, battery charging, and water pumping. In the last phase of study, the water pumping potential of the studied area has been investigated