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- MakaleYalnız künye2026Scopus SJRQ1Experimental 4E analysis (energy-exergy-economic-environmental) of hybrid parabolic trough collector-thermoelectric generator-phase change material cogeneration system
Guclu, Tamer; Cuce, Pinar Mert; Cuce, Erdem
Hybrid solar cogeneration systems are critical for enhancing energy utilisation and mitigating the intermittency of solar resources. This study presents a comprehensive 4E (Energy-Exergy-Economic-Environmental) experimental analysis of a novel hybrid system that uniquely integrates a Parabolic Trough Collector (PTC), a small-scale steam turbine, a Thermoelectric Generator (TEG) assembly, and a Phase Change Material (PCM) thermal storage unit. The system's performance was investigated under 15 distinct operating conditions, varying initial water masses (0.1, 0.15, 0.2 kg) and operating pressures (6, 8, 10, 12, and 14 bar). Experimental results demonstrated the system's adaptive cogeneration capabilities. At 14 bar and 0.2 kg, the system achieved its maximum Solar-to-Electricity efficiency of 0.42%. At this operating condition, the highest collector thermal efficiency was 25.25% (at 6 bar), and the maximum overall energy and exergy efficiencies were 8.43% and 1.45%, respectively. A key finding was the system's adaptive electrical output: at low pressures (6 bar), the TEG acted as a crucial co-generator, supplying up to 55% of the electricity, whereas at high pressures (14 bar), the turbine dominated, accounting for 88-90% of the output. Furthermore, the study experimentally confirmed that latent heat transfer was the dominant heat transfer mechanism for the PCM, with latent heat contributing ∼445 kJ (55%) of the 805 kJ total energy stored. The thermo-economic analysis confirmed the system's viability, yielding a Simple Payback Period (Spp) of 6.9 years and a competitive Levelised Cost of Energy (LCOE) of $0.101/kWh. The system is projected to save 118.8 kg of CO2 and 660 L of water annually. The results validate the thermodynamic and economic feasibility of the integrated PTC-Turbine-TEG-PCM concept as a flexible solution for small-scale solar cogeneration.
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İncele - MakaleAçık Erişim2024Scopus SJRQ3Exergetic Analyses of Detonation Engine Cogeneration Plants
Çakmak, Bahar; Karaali, Rabi
Efficiency improvements are very important in all research and technology. Detonation engines are high technology devices. In the last decades they attracted attention by many researchers. However, detonation engines for cogeneration are not researched efficiently. This article is about the detonation engines cogeneration cycles which analysed by using 1. and 2. law of thermodynamics and exergy analyses methods by the authors. The exergetic performance analyses, their advantage and disadvantages of the ZND-HRSG detonation engine cogeneration cycles were obtained. The exergetic performance analyses were done for various excess air rates to obtain the variations of the combustion exit pressures and temperatures, exergy efficiencies, electric heat rates, SFC and other parameters of their performance. Also, an optimization analysis was done for the ZND-HRSG by searching the optimum values for different excess air rates. The results showed that, the ZND-HRSG cycle have the optimum values of the performance at 1.6-1.8 of the excess air rates.
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İncele - MakaleAçık Erişim2022Scopus SJRQ2Investigation of inlet air pressure and evaporative cooling of four different cogeneration cycles
Karaali, Rabi
The objective of this study was to search the effects of the inlet air compressor pressure and evaporative cooling of four different cogeneration plants that are absorption cooling (ab), basic (bsc), air heating (airh), and air fuel heating (airfh) cogeneration systems by using the first law and the second law of thermodynamics, and the exergy analysis methods. For analysis, a program is written by the author in the FORTRAN programming language. Decreasing the atmospheric pressure or increasing the installation altitude of the plants increases the Z factor (ratio of lost exergy to useful exergy) of the four cycles about 10-13%. Also, decreasing inlet air pressure decreases the specific work about 25-28%, and the fuel energy saving ratio of the four cycles decreases about 29-30%. The method of water spray cooling of the compressor inlet air especially in the summer months, the humidity increases and the evaporative cooling can be obtained. By using this method, the ratio of lost exergy to useful exergy can be decreased for the four cycles about 0.5-2%. Also, the specific work of the four cycles can be increased about 1.2-6%.
AtıfOpenAlex4İncele - MakaleAçık Erişim2022Scopus SJRQ3Evaluation of four different cogeneration cycles by using some criteria
Karaali, Rabi; Keven, Arzu
The purpose of this article is to evaluate four different gas turbine cogeneration cycles which are basic, absorption cooling, air heating and air fuel heating cogeneration cycles by using the most important six evaluation criteria for different excess air coefficient, different compression rates, and different compressor inlet air temperatures. These six evaluation criteria are electrical heat ratio, exergy efficiency, incremental heat rate, artificial thermal efficiency, fuel energy saving ratio, and specific fuel consumption. It is seen that the air-fuel heating cogeneration cycle is the most efficient among the cycles examined for a certain compressor compression ratio, followed by the air heating, basic, and absorption cooling cycles.
AtıfScopus20WoS18OpenAlex30İncele - MakaleYalnız künye2017Scopus SJRQ3EFFECTS OF AMBIENT CONDITIONS ON PERFORMANCE OF GAS TURBINE COGENERATION CYCLES
Karaali, Rabi; Öztürk, Ilhan Tekin
In this paper, effects of the ambient conditions on performance of cogeneration cycles are analyzed by Using exergy analysis method. These cogeneration cycles are the simple cycle, the air preheating cycle, the air-fuel preheating cycle and the inlet air cooling cycle. Also; these cycles are evaluated thermodynamically for different air and fuel mass ratio and the performance of these cycles are compared. The electrical power generation increases about 10-15 % by decreasing the inlet air temperature of the compressor from 25 degrees C to 0 degrees C. However, the thermal power decreases about 10 % with decreasing inlet air temperature. During the summer, the electric power can be easilyincreased 2-7 % by injecting water into the inlet air of the compressor. The exergetic efficiency of cycles is decreased 11-13 %; by decreasing the compressor inlet air pressure from 101.3 kPa to 70.18 kPa. But this change decreases the electric power generation about 25 %. The highest exergy efficiency is obtained for the air-fuel preheated cycle. The simple cycle is the best among the four cycles to obtain high heat rate and heat exergy. The effects of all ambient conditions on these cycles are considered simultaneously, analyzed and compared With each other in this study.
AtıfWoS3İncele - MakaleYalnız künye2017Scopus SJRQ3Performance analyses of gas turbine cogeneration plants
Karaali, Rabi; Oztürk, Ilhan Tekin
In this study, some improving methods of gas turbine cogeneration cycles are applied on a simple cogeneration cycle. These methods are preheating air, preheating air and fuel, inlet air cooling by using evaporative cooling and absorption cooling. These cogeneration systems are evaluated with respect to energy efficiency (energy utilization factor), exergetic efficiency, electric and heat power, electric-heat energy rate, artificial thermal efficiency and fuel energy saving ratio and are compared with each other. In these analyses, the thermodynamic parameters such as compressing ratio, air and fuel mass ratio and compressor inlet temperatures of the cycles are used. It is concluded that these parameters can be listed from most effective to least effective as air fuel ratio, pressure ratio and compressor inlet temperature. It is also concluded that the most efficient cycle is found to be the air-fuel preheated cycle for obtaining more electric power and less heat power, and the simple cycle is the most suitable one for obtaining more heat power and less electric power.
AtıfScopus6İncele - MakaleAçık Erişim2017Scopus SJRQ2Efficiency improvement of gas turbine cogeneration systems; [Poboljšanje učinkovitosti kogeneracijskih sustava plinske turbine]
Karaali, Rabi; Öztürk, İlhan Tekin
In this study eight methods are evaluated for a gas turbine cogeneration cycle to improve the efficiency. These methods are increasing gas turbine inlet air temperature, cooling the inlet air of the compressor, air preheating, fuel preheating, increasing compressor inlet air pressure, increasing air excess rates, steam injection, and humidification of the inlet air of the compressor. These methods are studied in order to compare their effects on the performance of the systems. The effects of these methods on the exergetic efficiency depend on the kind of the cogeneration cycle. By combining recuperation, preheating fuel and steam injection methods high efficiency can be achieved. The combined methods give the best results under variable heat demands of the market. An appropriate combination of the efficiency improvement methods may increase the exergetic efficiency about 20 %. The results show that efficiency improvement methods must be applied together whenever it is possible.
AtıfScopus8WoS6OpenAlex15İncele - MakaleYalnız künye2016Scopus SJRQ3Thermodynamic optimization of a zero CO2 emission cogeneration cycle
Karaali, Rabi; Ozturk, Ilhan Tekin
CO2 emissions that have the greatest negative impact on the greenhouse and the global warming that should be decreased or kept at the same rates. Today fossil fuels share 60 % of total electricity production of the world, which plays an important role on CO2 emissions. Thermal cogeneration and zero CO2 emission cycles have potential for reducing this effect. By taking into consideration the most applicable and important zero CO2 emission cycles, a new cycle is designed. Thermodynamic analyses and optimization of this cycle is studied with FORTRAN code. The optimization results of this cycle show that the maximum exergy efficiency of this new cycle is 64 %, which is 17.6 % higher than (0,544) the one for the air preheated cogeneration cycle (APHCC) and 18.7 % higher than (53,9) the absorption cooling zero CO2 emission cycle (ACZEC). In the introduced new cycle, steam and CO2 in the exhaust gases are condensed so that the condensing energy of them is regained. For that reason, the heat output and the electrical power of the introduced cycle is better than the other cogeneration cycles.
AtıfScopus3İncele - MakaleYalnız künye2015Scopus SJRQ1Thermoeconomic optimization of gas turbine cogeneration plants
Karaali, Rabi; Öztürk, Ilhan Tekin
In this study, a novel thermoeconomic optimization method that is simple and efficient, for real complex cycles is introduced. First, a thermoeconomic analysis method that is called non-linear simplex direct search method is improved for the purposes of this study. The objective of this paper is to apply this method to four cogeneration cycles that are simple cycle, inlet air cooling cycle, air preheated and air-fuel preheated cycles for analyzing and optimizing. The four cycles are thermoeconomically optimized for constant power and steam mass (30 MW and 14 kg/s saturated steam flow rate at 2000 kPa), for constant power (30 MW) and for variable steam mass, and for variable power and steam mass by using the cost equation method and the effect of size on equipment method. The results obtained by the effect of size on equipment and by the cost equations methods are very different from each other. For the case of global optimization, the optimum electricity costs which also correspond to minimum are obtained as 0,0432 $/kWh for simple cycle, 0,0514 $/kWh for inlet air cooling cycle 0,0577 $/kWh for air preheated cycle and 0,058 $/kWh for air-fuel preheated cycle by using cost equations method. (C) 2014 Elsevier Ltd. All rights reserved.
AtıfWoS32OpenAlex39İncele - BildiriYalnız künye2012Scopus SJRQ1The role of cogeneration systems in sustainability of energy
Çakir, Uǧur; Çomakli, Kemal; Yüksel, Fikret
Cogeneration system (CHP) is one of the ways to save the energy and use the energy efficiently. When compared to separate fossil-fired generation of heat and electricity, CHP may result in a consistent energy conservation (usually ranging from 10% to 30%) while the avoided CO 2 emissions are, as a first approximation, similar to the amount of energy saving. In terms of sustainability, one of the primary considerations is energy efficiency. Sustainable energy is considered as a kind of energy which is renewable and continuous, meaning that the use of such energy can potentially be kept up well into the future without causing harmful repercussions for future generations. In this study, environmental benefits and sustainability aspects of cogeneration systems and importance of those systems to the use of sustainable energy are underlined. To support this idea, first we have referred some scientific studies previously made on cogeneration systems and then we have used our own case study. The case study made on gas engined cogeneration system was applied for a hospital to show the sustainability aspects of cogeneration systems.
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