نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه مهندسی مکانیک، دانشکده مهندسی، دانشگاه شهید چمران اهواز، اهواز، ایران
2 گروه مهندسی بیوسیستم، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز، ایران
3 گروه مهندسی مکانیک، دانشکده مهندسی، دانشگاه شهید چمران اهواز، اهواز، ایران.
4 گروه مهندسی بیوسیستم، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
This research investigated the technical and environmental feasibility of a solar preheater at the Dehbal Khuzayi CHP plant. The goal was to reduce fossil fuel consumption and boost thermal efficiency by using solar energy for boiler feedwater preheating. Dynamic simulations were performed using TRNSYS software to evaluate and compare the thermal behavior of the system, including evacuated tube and parabolic trough collectors. Weather data and the technical characteristics of the base system were considered in the model, and the model’s validity was confirmed by matching its outputs with experimental data. he results showed that the ETC is capable of producing 26,519 GJ of thermal energy per hectare annually, while the PTC has the capacity to produce 16,239 GJ per hectare annually. The outlet temperature of both collector types is capable of reaching the system’s design temperature during peak solar radiation hours. From an environmental perspective, the use of solar collectors resulted in an annual reduction of 4,243 tons of CO₂-eq in the ETC and 3,096 tons of CO₂-eq in the PTC. The economic analysis showed that the ETC is more economical, with a payback period of 2.7 years and an internal rate of return of 31.9 percent. Overall, the results indicate the high efficiency of integrating solar energy into boiler feedwater preheating and its positive impact on reducing fuel consumption, improving thermal efficiency, and decreasing greenhouse gas emissions at the Dehbal Khuzayi power plant.
کلیدواژهها [English]
Energy, the vital artery of development, faces environmental challenges due to fossil fuel reliance, making renewable technology development imperative for sustainability. Combined Heat and Power (CHP) systems enhance efficiency as a cornerstone of sustainable energy, yet require clean source integration, like solar, to mitigate pollution. Integrating a solar preheater significantly cuts fossil fuel consumption and operational costs of CHP plants by raising boiler feedwater temperature. Precise thermodynamic analysis and performance simulation of these hybrid systems, accounting for solar irradiation variability, are crucial for validation, which studies confirm offers substantial potential for boosting overall efficiency and lowering emissions. Specifically in the sugarcane industry, like at Dehbal Khozaei Company, heating boiler water with steam increases fossil fuel demand, creating a research gap in quantifying this opportunity. This study aims to fill that gap by modeling and comparing evacuated tube and parabolic trough collectors at the Dehbal Khozaei CHP plant, offering a practical optimization guide for management decisions
This study investigates the performance and the technical, environmental, and economic feasibility of integrating solar energy to preheat boiler feedwater at the Dehbal Khozaei CHP plant. The study aims to reduce fossil fuel consumption and enhance the plant's thermal efficiency by substituting part of the natural gas used in the boiler feedwater preheating process with solar energy. The plant's current process involves mixing demineralized water (21°C) and returned condensate (75°C) to 62°C, followed by preheating in a closed heater (92°C) and finally in a deaerator to the boiler entry temperature (133°C), with all required heat supplied by steam extracted from turbine bleeds. To achieve the objective, dynamic simulations of two solar collector types (parabolic trough collector (PTC) and evacuated tube collector (ETC)) were performed in TRNSYS software. The model incorporated precise local meteorological data for the latitude 31.3° N, 48.7° E extracted from Meteonorm software for dynamic analysis. Energy balance calculations using the steady-flow method determined the necessary solar collector area to partially substitute the control steam demand. This substitution directly translates to an increase in the plant’s overall thermal efficiency by reducing reliance on extraction steam. Following the modeling, an economic analysis and an assessment of the potential greenhouse gas emission reductions resulting from this substitution were conducted in RETScreen software, using data from the TRNSYS simulations. The validity of the entire developed TRNSYS model was confirmed by comparing its outputs with field data from a reference solar power plant (SEGS VI) in the Mojave Desert, ensuring the accuracy of the results.
The simulation results showed that the developed thermodynamic model has a low average relative difference of 6% when comparing the hourly fluid temperature output from the solar field with the empirical data from the reference power plant (SEGS VI), which validates the model’s reliability for analyzing the preheating system of the Dehbal Khozaei power plant. Over one working year, the required heat transfer rate for the heater (from 62 to 92 C°) and the deaerator (from 92 to 133 C°) were 22.64 GJ/h and 33.18 GJ/h, respectively at peak capacity. The total annual energy required for preheating was calculated to be 489022 GJ. Simulation of ETC performance revealed a maximum production capacity of 55.16 GJ/h at peak irradiation, enabling it to meet 99% of the thermal demand at baseline conditions. Results indicated that an ETC with an area of 29,000 m² is capable of producing 76,905 GJ of thermal energy annually, supplying about 15.7% of the total feedwater preheating energy requirement. In contrast, PTC with an area of 34,560 m² can produce 56,122 GJ, covering approximately 11.5% of the baseline system's needs. The outlet temperature of both collector types during peak solar hours is capable of reaching the system's design temperature. From an environmental perspective, using solar collectors led to an annual reduction of 4,243 tons of CO₂ eq for the ETC system and 3,096 tons of CO₂-eq for the PTC system, equivalent to removing approximately 777 and 567 gasoline-powered vehicles from the transportation cycle, respectively. The Net Present Value (NPV) of the solar preheating system with ETC was calculated at $128 million after tax. The after-tax Internal Rate of Return (IRR) for this system was 31.9% with a payback period of 7.2 years. For the PTC-based system, the after-tax NPV was $74 million with an IRR of 18.7% and a payback period of 13.5 years. Although both projects are economically viable, the ETC system is recommended as the more economically favorable option for the Dehbal Khozaei CHP plant due to its lower initial investment, shorter payback period, and higher profitability indices. Ultimately, both solar systems act as complementary heat sources and are unable to continuously supply the thermal load throughout the entire year.
The ETC, with a smaller absorption area, offers a higher annual efficiency (producing 15.7% the total energy requirement) compared to the PTC (11.4% of the total energy requirement). Both technologies are capable of supplying the required temperature for boiler feedwater preheating, but ETC creates a greater reduction in CO2-eq emissions (16% versus 11%). The results demonstrate the high effectiveness of integrating solar energy for boiler feedwater preheating and its positive impact on reducing fuel consumption, enhancing thermal efficiency, and lowering greenhouse gas emissions at the Da'bal Khazaee plant. Overall, the Evacuated Tube Collector is introduced as the superior technology for reducing fuel consumption and emissions in this power plant, although both remain complementary sources.
The study was funded by Shahid Chamran University of Ahvaz, Iran, and Grant No. SCU.AA98.29747.
Conceptualization, Ayoub Kaabimofrad, Abbas Asakereh, Ebrahim Hajidavalloo and Mostafa Kiani Deh Kiani; methodology, Ayoub Kaabimofrad, Abbas Asakereh and Ebrahim Hajidavalloo; software, Ayoub Kaabimofrad and Mostafa Kiani Deh Kiani; validation, Abbas Asakereh and Ebrahim Hajidavalloo; formal analysis, Abbas Asakereh; investigation, Ayoub Kaabimofrad; resources, Ayoub Kaabimofrad and Abbas Asakereh; data curation, Ayoub Kaabimofrad; writing—original draft preparation, Ayoub Kaabimofrad; writing—review and editing, Abbas Asakereh, Ebrahim Hajidavalloo and Mostafa Kiani Deh Kiani; visualization, Ayoub Kaabimofrad; supervision, Abbas Asakereh and Ebrahim Hajidavalloo; project administration, Abbas Asakereh; funding acquisition, Abbas Asakereh. All authors have read and agreed to the published version of the manuscript.
All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
During the preparation of this work, the authors did not use any generative AI or AI-assisted technologies.
All data utilized in this study are provided within the text, as well as in the form of tables and figures. Additional data are available from the authors on request.
The authors express their gratitude to the Vice Chancellor for Research and Technology of Shahid Chamran University of Ahvaz, Iran, for providing financial support through the research grant (No. SCU.AA98.29747).
The authors avoided data fabrication, falsification, and plagiarism, and any form of misconduct.
The author declares no conflict of interest.
)