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Article Citation - WoS: 17Citation - Scopus: 24Optimization and Energy Analysis of a Novel Geothermal Heat Exchanger for Photovoltaic Panel Cooling(Pergamon-elsevier Science Ltd, 2021) Jafari, Rahim; Jafari, Rahim; Jafari, Rahim; Automotive Engineering; Automotive EngineeringElectrical energy and conversion efficiency of the photovoltaic (PV) solar panels are measured under standard test conditions in some microseconds at the room temperature (25 degrees C). It also is seen that the actual working conditions, on the other hand, with higher ambient temperature and continuous generated heat in the PV cells can lead to reduction in reduce their electricity generation and long-term sustainability. In the current work, the coolant (water + ethylene glycol) circulates between two heat exchangers; the minichannel heat exchanger is bounded to the PV cells and geothermal heat exchanger is buried underground, and it is set to remove the heat from PV cells to the ground. Six control factors of the geothermal cooling system are considered for the purpose of optimization using Taguchi design and main effect analysis. These parameters are pipe length, soil thermal conductivity, coolant flow rate, adjacent coil distance, pipe inner diameter and pipe thickness. The experimental results show that the average net electricity generation of the cooled PV panel is improved 9.8% compared to the PV panel without cooling system. However, with the same geothermal heat exchanger it drops to 6.2% as the cooled panel number is doubled. The simulation results reveal that the optimum configuration of the geothermal cooling system is capable of enhancing the net electricity generation of the twin cooled panels up to 11.6%. The LCOE of the optimized geothermal cooling system was calculated 0.089 euro/kWh versus the reference panel of 0.102 euro/kWh for the case study of 30 kW PV solar plant.Article Citation - WoS: 15Citation - Scopus: 17Performance Evaluation of Laser Induced Breakdown Spectroscopy in the Measurement of Liquid and Solid Samples(Pergamon-elsevier Science Ltd, 2018) Bilge, Gonca; Sezer, Banu; Boyaci, Ismail Hakki; Eseller, Kemal Efe; Berberoglu, HalilLiquid analysis by using LIBS is a complicated process due to difficulties encountered during the collection of light and formation of plasma in liquid. To avoid these, some applications are performed such as aerosol formation and transforming liquid into solid state. However, performance of LIBS in liquid samples still remains a challenging issue. In this study, performance evaluation of LIBS and parameter optimizations in liquid and solid phase samples were performed. For this purpose,milk was chosen as model sample; milk powder was used as solid sample, and milk was used as liquid sample in the experiments. Different experimental setups have been constructed for each sampling technique, and optimizations were performed to determine suitable parameters such as delay time, laser energy, repetition rate and speed of rotary table for solid sampling technique,and flow rate of carrier gas for liquid sampling technique. Target element was determined as Ca, which is a critically important element in milk for determining its nutritional value and Ca addition. In optimum parameters, limit of detection (LOD), limit of quantification (LOQ) and relative standard deviation (RSD) values were calculated as 0.11%, 0.36% and 8.29% respectively for milk powders samples; while LOD, LOQ and RSD values were calculated as 0.24%, 0.81%, and 10.93% respectively for milk samples. It can be said that LIBS is an applicable method in both liquid and solid samples with suitable systems and parameters. However, liquid analysis requires much more developed systems for more accurate results. (C) 2018 Elsevier B.V.All rights reserved.Article Citation - WoS: 23Citation - Scopus: 29Analysis of Combined Cycle Efficiency by Simulation and Optimization(Pergamon-elsevier Science Ltd, 2017) Balku, SaziyeNatural gas has been regarded as the cleanest fuel when compared to the other fossil fuels because of its low emission of greenhouse gases and no particulate matter after combustion. Around 22% of the world's power production is based on natural gas. Combined gas-steam power plants operating with natural gas are preferred in recent years due to their high efficiency and less emission. To meet the world's increasing energy demand, natural gas will continue to be used in the future in increasing amounts. For this reason, it is very, important to design and operate such systems in optimal conditions. Energy conversion systems can be analyzed in terms of energetic, exergetic, economic, and environmental aspects for a good management. When the overall efficiency is increased, it can be said that these four aspects will also improve. In the present study, the modeling, simulation and optimization studies on the combined gas-steam power plants are performed. The most important parameters which influence the efficiency of such plants are determined. The simulation results indicate that the crucial unit is the combustion chamber. The optimization results show that the most effective parameters in the power production are air/fuel ratio, gas/steam ratio and the pressure ratio for the compressor and, thus, the gas turbine. The thermal efficiency of the plant increases by 22.55% and the exergy destroyed decreases by 22.65% using optimal design variables determined by the optimization algorithm in which the objective function is the thermal efficiency. The study demonstrates that the modeling, simulation and optimization can be used for the optimal design of the plants before invested, for operating the present plants at optimal conditions and for analyzing the systems. The minimum detrimental effect on the environment can be provided by optimal design and operation under optimal conditions. The originality of the study is to use an objective function by defining a new efficiency term for the maximum power production with the minimum exergy destruction which results 23.49% increase in the thermal efficiency and, in the meantime, 23.61% decrease in the exergy destruction. This new efficiency term can be used as an objective function in the solution of the optimization problems related with the efficiency of power generating in order to achieve better results. (C) 2017 Elsevier Ltd. All rights reserved.
