Authors:Sibel YILMAZ EKİNCİ; Seda SANCAKLI, Adam LAW, John Michael WALLS Abstract: Reflection from the front glass of solar modules causes over 4% optical loss leading to a significant decrease in module efficiency. Single layer solution gelation (sol-gel) anti-reflective (AR) coatings are effective over a narrow range of wavelengths, whereas reflection losses can be reduced over a broader wavelength when multilayer broadband AR coatings are applied. In this work, three different multilayer AR coatings including 4-layer SiO2/ZrO2, 4-layer SiO2/ITO, and 6-layer SiO2/ZrO2 were deposited using magnetron sputtering. The abrasion resistance is important because the coatings will be subject to regular cleaning cycles. A variety of abraders including Felt pad, CS-10 and CS-8 under different loads are used. The optical performance and durability of these coatings were analyzed using a spectrophotometer, optical microscope, scanning electron microscope, and scanning white light interferometer. No damage was observed after abrasion of the coatings with a felt pad under 1 and 2 N loads. However, there was a slight increase in Weighted Average Reflection. When coatings were tested with CS-10 and CS-8 abraders, coatings with ZrO2 resulted in higher scratch resistance in comparison to coating with ITO. However, all-dielectric broadband AR coatings are more durable and have better optical performance compared to single layer sol-gel coatings. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Helin Ülgen ELMACIOĞLU; İrem ÖZSEVGİN, Cennet KOCABIYIK, Nezir Yağız ÇAM, Levent BİLİR Abstract: With the continuous worldwide energy use increase, energy efficiency is gaining high importance. Consequently, many methods have been investigated for potential energy savings. One of these methods is the use of heat recovery systems. These systems basically re-use waste heat and reduce energy consumption. Also, they are increasingly used to reduce heating and cooling demands of buildings. Their main feature is to provide fresh air to the place which is heated by the exhaust air with the help of a heat exchanger (HEX) working between two different temperature sources. The most commonly used types of heat exchangers in ventilation systems are cross-flow and counter-flow heat exchangers. Cross-flow heat exchangers have a thermal efficiency in the range of 50-75% while counter-flow heat exchangers have 75-95%. Many studies have been carried out to increase the efficiency of this type of heat exchangers. In this study, different designs of cross-flow and counter-flow exchangers are compared using ANSYS Fluent software. The aim is to determine how the plate surface geometry affects heat transfer and pressure drop. It is aimed to find the optimum design with maximum efficiency, high heat transfer and low pressure drop for heat exchangers. As a result, it has been observed that thermal efficiency increased from 18% to 60% when changing from cross flow to counter flow in flat plate design, while it increased from 25% to 77% in enhanced plate designs. For enhanced designs, counter flow heat exchanger is 52% more efficient than cross flow heat exchanger. Also, improvements to increase the surface area and turbulence in both flow types have increased heat transfer and thermal efficiency. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Nam TRAN; Thao HUYNH VAN, Khanh HUYNH, Luan NGUYEN, Ngan NGUYEN, Diem HUYNH, Danh DİNH, Cong NGUYEN Abstract: This study evaluated biogas production potentials from local biomass feedstocks comprising of rice straw (RS), steamed lemongrass (SL), bagasse (BA) and desiccated coconut (DC) on super-intensive shrimp sludge (SS) anaerobic digestion. A series of batch anaerobic digestion experiments was conducted at an organic loading rate of 50 g-VS L-1 and a C/N ratio of 25 under mesophilic conditions. The results indicate that co-digested biomass substrates are more suitable than single sludge except for DC supplementation, which exhibited a severe pH inhibition for methanogenesis activities. A reactor supplemented with BA achieved the highest overall biogas production (126.78 L kg-VSadded-1), which increased biogas yields 53.70% compared to a mono-sludge reactor. Furthermore, reactors with RS and SL increased biogas yields by 26.40% and 29.21%, respectively. Irrespective of initial materials, the H2S concentration in biogas compositions was measured at very high levels (23,710 - 65,040 ppm) after 10-15 days of digestion, while a decreasing trend was recorded for the remaining digestion period (16 - 60 days), yet still maintained relatively high levels (5,873 - 9,155 ppm). The study suggests that future works should focus on pH neutralization within the reactor with DC substrates and H2S removal in biogas composition. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Ahmet Erhan AKAN; Aytac Perihan AKAN Abstract: In this study, techno-economic and environmental feasibility analyses of a wind turbine for different hub connection heights were investigated using RETScreen Expert energy analysis program. Çerkezköy district of Tekirdağ province was chosen as the region in which the wind turbines will be constructed. According to the analysis of hourly wind speed data recorded by a meteorology station established in Çerkezköy, it can be easily said that the annual average wind speed for 10 m altitude is 5.305 m/s and the directions of the prevailing winds are between NE (45o) and ENE (67.5o). The model of the wind turbine chosen in the present study is the Sinovel 1500/77, and techno-economic and environmental evaluations were made for the hub connection heights of 65, 80 and 100 m. In accordance with the study results, when the payback period is evaluated in terms of energy production cost and greenhouse gas reduction potential, the wind turbine with 100 m hub connection height exhibits better results than others with 65 and 80 m. It is thought that this study will guide selecting a suitable hub height for wind power plants and wind turbines that are planned to be established in Çerkezköy, one of the largest industrial regions of Turkey to obtain cost-effective and environment-friendly conditions. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Tarık TUFAN; Hasan KÖTEN Abstract: Energy harvesting, which is a popular subject, can be defined as the use of energy released by environmental forces such as earth-shaking, wind, etc. Civil engineering structures also harvest energy in a different way. Thanks to this energy harvest, the modal properties of structures such as natural frequency, mode shape can be estimated from the response histories taken from the structure. Modal properties of the structure give an impression of the health of the building. However, an important question comes to mind: Did the energy harvesting of the structures sufficiently drive the modes used to detect damage' Or in other words, has it exceeded a certain amount of energy to drive the modes' If the mode in question is not sufficiently excited, it can be interpreted as a harbinger of damage for an undamaged structure in the analysis using these modes. For this reason, it is an important issue to determine to what extent the modes are driven. In this study, the aforementioned subject has been explored with the title "Mode Excitation Energy" using the modal plot method. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Pınar USTA; Başak ZENGİN Abstract: Buildings are responsible for most of the energy consumption in countries, thence energy saving in buildings is a high priority issue. Windows and glazing types are one of the factors that greatly affect the performance of buildings, both in terms of thermal comfort and energy consumption for heating or cooling. The proper selection of window glazing is one of the effective strategies to minimize energy consumption. In this study, an office building was designed to determine the most suitable glazing type for office buildings, which is the main purpose, and the energy efficiency of the building was examined with Openstudio and Energyplus software. Energy modeling of the office building was conducted for four different types of glazing by using VRF systems for air-conditioning and a dedicated outdoor air system for ventilation. The effect of different windows glazing system properties on the energy performance and total energy need was calculated by considering the fixed indoor thermal and visual comfort conditions were evaluated. The study results indicated that energy consumption can reduce about 24.88 kBtu/ft2 (25%) using suitable glazing material. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Tapan GOGOİ; Utpal DUTTA Abstract: In this study, the performances of a combined power and cooling system are compared at solar, solar storage (SS), and storage mode of operations using therminol–LT (TLT) and solar salt as storage media. In the solar mode, the entire water heated in a collector field is used to drive subsequently an organic Rankine cycle and an absorption cooling system. In the SS mode during high radiation (950 W/m2), thermal energy storage (TES) is used to store a fraction of hot water for later use during the storage mode at nighttime. The system produced 1.1 MW of power and 2.455 MW of cooling during the solar mode at low radiation (640 W/m2). At the SS mode, with TLT as a storage fluid, the power increased to double, however the cooling reduced by 12.22%. During the storage mode, the TLT based system produced 0.553 MW of cooling. During the SS mode with solar salt, the power and cooling increased, however, the nighttime cooling reduced significantly with solar salt. The total energy and the overall system efficiency was more with solar salt compared to those of TLT. The energy output and the system efficiency were the maximum at 950 W/m2 without TES. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Nagı Reddy B; Sahithi Priya KOSİKA, Manish Patel GADAM, Jagadhishwar BANOTH, Ashok BANOTH, Srikanth GOUD, B. Abstract: In this paper, a new non-isolated buck-boost converter with positive output is designed. This buck-boost converter contains two active switches which operates synchronously. Hence, the control circuit for the given converter is simple. Compared with the conventional buck-boost converter, the newly designed topology has few advantages such as positive output voltage and quadratic voltage gain. Due to the quadratic voltage gain, this converter can achieve wide voltage conversion ratios without the use of extreme (very low or high) duty ratios. The output voltage of this proposed converter is common ground with the input voltage and its polarity is positive. The continuous conduction mode operation (CCM) of the converter is deeply analyzed in steady state conditions. The necessary component design equations are also obtained along with the switching stresses. The MATLAB/Simulink software is used to design and simulate the proposed converter. The simulated results as well as the comparisons are provided to evaluate the effectiveness of the proposed buck-boost converter. PubDate: Thu, 31 Mar 2022 00:00:00 +030
Authors:Ram Kumar PAL; K Ravi KUMAR Abstract: The overall performance of parabolic trough solar collector (PTSC) based power plants could be improved by introducing the Direct steam generation (DSG) in the receiver of the solar collector. However, the thermal-hydraulic instability induced in the DSG process is a severe issue for the commercial application of the technology. The concentrated solar flux falling on the dry portion of the absorber before or after solar noon generates a high circumferential thermal gradient in the stratified flow region. In this work, numerical analysis of thermo-hydrodynamics of DSG has been performed to study the effect of position of solar flux profile using CFD solver ANSYS Fluent 2020R1. The TPF in the solar collectors is modeled through two-fluid modeling approach. The inlet mass flow rate and operating pressure for PTSC are considered as 0.6 kg/s, and 100 bar, respectively. The solar beam radiations are considered as 750 W/m2 and 1000 W/m2. The obtained results revealed that temperature distribution at the absorber outer surface varies in the range of 585 K to 643 K. The maximum circumferential temperature difference is observed as 55.5 K. The volume fraction of vapor at the absorber outlet are found as 0.31 and 0.37 respectively for DNI 750 W/m2 and 1000 W/m2. The corresponding pressure losses are 316 Pa and 350 Pa, respectively. The obtained results could be employed to characterize the thermal behavior of the DSG solar collectors. The model is useful to configure the solar field operation for optimum performance. PubDate: Thu, 31 Mar 2022 00:00:00 +030
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