Energy Systems Engineering / Enerji Sistemleri Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4752
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Article Stochastic 1-D Reactive Transport Simulations To Assess Silica and Carbonate Phases During the $co_2$ Reinjection Process in Metasediments(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2024) Erol, SelçukOne proposed method to mitigate carbon emission is to mineralize the $CO_2$ in deep geothermal reservoirs while mixing the coproduced CO2 with the effluent fluid for reinjection. The injection fluid temperature fluctuates due to the mixing process between CO2-charged water and the effluent fluid, and compressor interruptions change the thermodynamic conditions that influence the fluid- rock interaction in the reservoir. Mineral dissolution or precipitations are associated with changes in permeability and porosity that affect the flow and, eventually, the lifespan of the reservoir. A combined stochastic–reactive transport simulation approach is useful for inspection purposes. Moreover, the stochastic algorithm validates the deterministic reactive transport simulation and demonstrates the time evolution of a chemically reacting system in the reservoir. This study examines a range of injection temperatures between 80 °C and 120 °C to evaluate silica and calcite precipitation along a flow path. One-dimensional (1-D) reactive transport and compartment- based stochastic reaction-diffusion-advection Gillespie algorithms are carried out. The 1-D model represents a reservoir feed zone of around 2300 m. Two common metasediment rock types are evaluated for inspection. The first one is the muscovite schist, which has approximately 60% quartz, and the second is the quartz schist, consisting of roughly 90% quartz. The stochastic method can be applied more effectively if the chemical system is completely defined with proper reaction rates as a function of temperature. The mixing ratio of the coproduced $CO_2$ over the effluent fluid is around 0.0028. Simulation results show that $CO_2$ is partially sequestrated as calcite within the first 10 m of the entrance to the reservoir and plugs the pores completely in the muscovite schist scenario. Chalcedony and α-cristobalite precipitate as secondary minerals evenly along the flow path. $CO_2$ injection into a quartz schist layer is more appropriate for geochemical interactions below 120 °C.Article Citation - WoS: 7Citation - Scopus: 8Update for Reactive Transport Modeling of the Kızıldere Geothermal Field To Reduce Uncertainties in the Early Inspections(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2023) Erol, Selçuk; Akın, Taylan; Akın, SerhatThe development of carbon capture and storage techniques has become essential to reduce and mitigating CO2 emissions to the atmosphere. CarbFix1 and CarbFix2 projects carried out in Iceland demonstrated that the emissions of waste CO2 gas from geothermal power plants can be captured and mixed with the effluent geofluid and subsequently injected back into the geothermal reservoir. This experience gained in the CarbFix projects expanded into other geothermal fields around Europe, and one of the demonstration sites is the geothermal field in Turkey, Kızıldere. This paper focuses on the results of an updated study on early field evaluations with reactive transport simulations. In the new three-dimensional numerical model, the geological formations and fault zones were updated according to the well-logs data. Based on the tracer tests performed in the field, the anisotropic permeabilities between the wells were evaluated and imposed into the model. Geofluid chemistry, mineral components, and the volume fractions used as input in the simulations are modified depending on the performed laboratory experiments on the metamorphic schists taken from the geothermal site (i.e. X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning-electron microscope (SEM), and batch reactor tests). Different thermodynamic databases such as Lawrance Livermore National Laboratory (LLNL) and Thermoddem databases were tested using PHREEQC and TOUGHREACT programs for consistency with experiments. The thermodynamic conditions and the geofluid-rock-CO2 interactions prevent the mineralization of CO2 in the reservoir. This outcome differs from CarbFix projects in terms of the carbonization process, but the CO2 injection is still reliable with solubility-trapping in a geothermal reservoir to partially mitigate the emission. Roughly, 200 kt of CO2 in 10 years can be safely injected into the geothermal reservoir. According to the new analysis, the ratio of magnesium, sodium, and potassium varies in solid solution series of feldspars and clay minerals as albite end-member and montmorillonite/illite end-members, respectively. The evaluations of solid solution reactions are relatively limited in the law of mass action approach used by PHREEQC and TOUGHREACT. © TÜBİTAK.Article Citation - WoS: 1Citation - Scopus: 1Energy and Exergy Analysis of a Geothermal Energy Sourced Hot-Air Drying System(Inderscience Enterprises, 2023) Helvacı, Hüseyin Utku; Keleş, Nazlı; Gökçen Akkurt, GüldenA geothermal energy-sourced drying system was tested for the thin-layer drying process of tomato slices at air temperatures of 40 degrees C, 50 degrees C and 60? and velocities of 0.5 m/s and 1.5 m/s to investigate system performance in terms of the first and second laws of thermodynamics. The energy and the exergy efficiency of the system were found to be 6.6% and 22.31%. The energy utilisation and energy utilisation ratio were calculated in the range of 1.271 kW-5.102 kW and 9.644%-39.56%, respectively. The exergy destruction, exergy efficiency and improvement potential of the drying chamber varied between 0.0198 kW-0.2621 kW, 59.74%-81.95% and 0.00486 kW-0.07396 kW, respectively.Article Citation - WoS: 1Citation - Scopus: 1Thermodynamic Re-Assessment of a Geothermal Binary Power Plant Operated in a Moderate-Temperature Geothermal Field(Inderscience, 2023) Özcan, Zeynep; Gökçen Akkurt, GüldenAn existing organic rankine cycle power plant which uses isobutane as working fluid is re-evaluated for different working fluids. The plant is first modelled by EES software; then the model is simulated for different working fluids obtaining heat transferred through the heat exchanger, net work output, energy and exergy efficiencies, and mass flowrate of the working fluid. Two parametric studies are conducted to evaluate the thermodynamic performance of the plant under a range of turbine inlet temperature (130°C–155°C) and geothermal resource temperature (152°C–161°C) for each working fluid. The study reveals that the highest cycle energy and exergy efficiencies are observed for R-152a at any geothermal resource temperature. R-152a resulted with 13.1% and 58.2% cycle energy and exergy efficiency, respectively at operation condition, whilst the lowest efficiency and net work output is calculated under n-butane presence.Article Citation - WoS: 1Performance Analysis of Thermal Storage Assisted Cooling Tower With Night Cooling(Gazi Üniversitesi, 2020) Ouedraogo, Kiswendsida Elias; Toprak, KasımAs global warming and water scarcity issues continue to grow, it is essential to increase resources efficiency for air conditioners and power plants. In order to increase the efficiency, the systems need to be modified to take the advantages of the low night temperature and thermal storage tanks. In this study, the low night temperature and thermal storage tanks effects on the cooling tower is studied using TRNSYS. Using a chiller operating from 8:00 to 16:00 as a case study, hot water from the condenser is partially stored on daytime and cooled slowly during the night. The storage tank volume is optimized by considering two big tanks and five small tanks. The results show that night cooling reduces cooling water temperature by 5.8 degrees C or 21.8% while the cooling efficiency is increased by 36%. The thermal storage tanks enable to have the low continuous flow rate and help to reduce the fan power by 67.1%. On the storage side, compared to two tanks system, the tanks volume is reduced by 16.5% when 5 tanks are used. In theory this reduction can go up to 50% by increasing the number of tanks and reducing their individual size.Article Citation - WoS: 7Inertia and Droop Controller for a Modern Variable Speed Wind Turbine To Provide Frequency Control in a Microgrid(Gazi Üniversitesi, 2020) Hassan, Ali; Altın, Müfit; Bingöl, FerhatThe increasing penetration of modern Variable Speed Wind Turbines (VSWTs) in microgrids creates the problem of frequency stabilization due to reduced inertia of the power system. To emulate the Inertia Response of the conventional synchronous machines, wind turbines can be provided with an inertia emulation controller. The modeling presented in this paper aims at equipping the modern Type D wind turbine with inertia response and primary frequency control (PFC) capabilities. Two controllers - inertial and droop, are implemented and their frequency control capabilities are compared in an isolated power system which consists of a conventional steam turbine generator and a wind farm. The results suggest that proposed controllers help in better frequency control performance in the microgrid.