• Energy Research

In geothermal power plants with dual pressure cycle technology, the optimisation of turbine inlet parameters depending on the pressure and temperature of the geothermal fluid is a very important parameter affecting the production capacity of such plants. In combined systems, where the second stage (low pressure) is fed by the first stage (high pressure), failure to determine the appropriate operating conditions leads to the problem of not achieving optimum performance. In this context, the study aims to develop a methodology for predicting the performance of the system, based on the geothermal water temperatures entering and leaving the heat exchangers, in order to clearly see the effect of the operations carried out within the scope of optimising the turbine inlet parameters on the system behaviour. In this study, EBSILON (R) Professional software developed by Steag GbmH was utilised to simulate the determined correlations. The effect of the heat exchangers (preheater, evaporator and superheater) in both stage-1 and stage-2 on the temperature profiles and heat gains were determined at 10-17 bar, 126.5-165 degrees C for Turbine-1 and 4-8 bar, 84-135 degrees C for Turbine-2. Optimum turbine inlet temperature and pressure have been determined for maximum heat input and exergy efficiency. In this context, each cycle in the Energy Converter System (ECS) was first simulated by changing the turbine input parameters and then thermal analyses of the system were performed using the performance outputs obtained from the simulation software. For turbine-1, it is observed that heat transfer decreases in stage-1 with increasing pressure and temperature, while heat transfer increases in stage-2 fed from stage-1. After 12 bar and 136 degrees C, the heat transfer of the ECS started to increase and the maximum heat transfer amount was reached at 17 bar and 155 degrees C. However, it was determined that the exergy efficiency of the ECS started to decrease after 15 bar and 147.6 degrees C. For turbine-2, it was found that the increase in pressure and temperature decreases the ECS heat transfer but increases the exergy efficiency. As a result of numerous iterations with EBSILON (R) Professional software, a maximum exergy efficiency of 50.53% was achieved in turbine-1 (15 bar, 147.6 degrees C) and turbine-2 (8 bar, 114 degrees C).

The present paper dealt with the performance analyses and improvement probabilities detection for the present geothermal power plant. In addition, the present study aimed to present an analysis methodology for manufacturers and users to detect deficiencies, inadequacies and probable improvements for a present system. In this study, a geothermal power plant was used as a sample system for the analyses. Analyses were applied to the plant regarding energy, exergy, economic and environmental aspects. After comprehensive analyses, it was observed that the power consumption of the fans shows dramatic change depending on the seasons. For this reason, if the location and site conditions of the facility are suitable, performing the cooling processes with water-cooled condensers instead of air-cooled condensers was suggested. Moreover, by keeping the acceptance of saturated steam inlet at the turbine, it is thought that an increase in system performance will be achieved by designing a pump system that can increase organic fluid pressures up to partially higher pressures. In addition to all these, it was recommended to analyse the effect of integrating a superheater to bring the organic fluid to the superheated vapour phase at the turbine inlet.

Abstract The increasing need for fossil energy along with waste gases led to both the increase in the environment pollution and search for alternative energy sources. The most important criterion here is to maintain sustainability and find a zero-emission source. In this regard, since hydrogen is obtained from the water electrolysis or the digestion of hydrocarbons, it is one of the alternative clean energy sources. Despite intense usage of the hydrogen in the refineries and industries, it is also predicted to be common use of hydrogen in power systems as fuel soon. The present study analysed the change in performance of gas turbines depending on water injection into the air before the compressor. In the study, two different gas turbine systems (non-recuperative and recuperative) is designed. For the use of hydrogen as a fuel for the designed gas turbine systems, the injected water amount was increased from 0 kg-water/s to 46 kg-water/s, while the GT-Turbine inlet pressure increased from 4 bar to 20 bar. For these circumstances, the performance of the gas turbine systems investigated depending on injected water-air mass flow ratio and GT-Turbine inlet pressure. After comprehensive analyses, the maximum net power production, thermal and exergy efficiencies of the non-recuperative gas turbine were calculated as 58,459 kW, 22.33% and 23.07% at 20 bar and 0.031 injected water/air mass flow ratio. The maximum net power production, thermal and exergy efficiencies of the recuperative gas turbine system were calculated as 131,307 kW, 50.16% and 52.70% at 4 bar and 0.057 injected water/air mass flow ratio.

Performance data from a geothermal power plant that uses a dry-type working fluid (n-Pentane) was evaluated. The experimental working conditions of the geothermal power plant were recorded. By using these recorded data the structural and parametrical optimisation of the plant was applied. As a structural modification, the probable performance of the plant was scrutinised by considering the integration of a superheater into the plant. For both present and structurally optimised cases, parametric optimisations were made as an operational modification. During the analyses, the high and low pressure Organic Rankine Cycles (ORCs) of the energy converter plant were optimised for varying turbine inlet temperatures and pressures. After comprehensive analyses, it was concluded that superheating the working fluid by structural modification (superheater integration) had a negative effect on the system performance. On the other hand, together with parametric analyses, a considerable improvement in system performance was obtained. For all cases and parametric values, the system was also evaluated in terms of environmental effect.

Many developed countries are increasingly interested in renewable energy sources (RESs) as a result of environmental changes and the depletion of fossil fuels in recent years. Since geothermal energy can be used as both a source of electricity and heat, it occupies an important spot among renewable energy sources. In this study, soft-computing ensemble models (SCEMs) based on supervised deep neural network (SDNN) models supported by the forward stepwise regression (FSR) method are used in estimating the power generation from geothermal resources. Outputs of the FSR process led SDNN phase. Adaptive Moment Estimation (ADAM) and Nesterov-accelerated Adaptive Moment Estimation (NADAM) methods were used to optimize SDNN models. For the daily power generation, the best performance has been shown by the model of SDNN optimized using ADAM optimizer with a coefficient of determination (R2) of 0.9807 and root mean square error (RMSE) of 0.0466, respectively.

In this study, the integration of a Parabolic Trough Collector with different power cycles was investigated on an annual basis in terms of Energy, Exergy, Economics and Environmental under different meteorological conditions. A parabolic trough collector with 500 collectors with a gross and net aperture area of 432,000 and 817.43 m2, was installed in a place that has a high solar energy potential. With a Parabolic trough collector, hourly Direct Normal Irradiation, wind speed, wind direction, ambient temperature and incident angle values were obtained for the 15th of each month for a year. The performance of the 3 power cycles with 6 different configurations using the Parabolic trough collector as the heat source was comprehensively analyzed and compared. During the dynamic data use and various commonly used power systems comparing study, it was aimed to answer the most commonly asked questions by the researchers in this area. To do this, the effect of direct normal irradiation and incident angle on the performance of systems to reach the maximum net power was studied. After calculations, the maximum net power was not found on July 15 (12:00) when the maximum direct normal irradiation (840.868 W/m2) was seen. The maximum net power (67867 kW) was found on September 15 (12:00) when the incident angle was minimum (1.71°) along with the high direct normal irradiation. Steam Rankine Cycle, Organic Rankine Cycle and Kalina Cycle performance comparisons were made both annually depending on time and with different configurations and fluids. In addition to tangibly showing the superiority of incident angle on direct normal irradiation, the present study aimed to present the best-performing system configuration for the researcher, user, scientists, and manufacturers. Interestingly, while the Organic Rankine Cycle with heat exchanger with R123 showed better performance in terms of power production and carbon dioxide emission reduction, the Kalina Cycle was found much more feasible in terms of economics.

Abstract In this paper, a subcritical and supercritical organic Rankine cycle (ORC) are designed to recover exhaust gas waste heat of biogas fuelled combined heat and power (CHP) engine. The CHP engine is located in Belgium and uses biogas as fuel which is produced from the digestion of domestic wastes by anaerobic digestion. R245fa is selected as working fluid. First, the system parameters as net power, mass flow rate, pumps total power consumption, total evaporator exergy inlet, thermal efficiency and exergy efficiency are improved by changing turbine inlet temperature and pressure. After which second low analysis of the overall system and system components are determined for the best performed subcritical and supercritical cycles. Compared with subcritical ORC, the supercritical ORC has shown better performance. The best performed cycle net power, thermal efficiency and exergy efficiency are evaluated as 79.23 KW, 15.51% and 27.20% for subcritical ORC and 81.52 kW, 15.93% and 27.76% for supercritical ORC, respectively.

Abstract In this study, the advantages of the ORC were used to improve overall performance of a simple gas turbine (GT) located in a wood production facility. In addition to ORC, a steam boiler (SB) is also coupled with the GT to improve overall performance and to produce needed steam. During study, benzene, cyclohexane, hexane, R11, R123, R600, R601 and toluene were used as working fluid. During parametric optimisation of ORC, entering pressure of turbine rose from 10 bar to 35 bar, while entering pressure of turbine rose from saturated steam temperature to fluid’s maximal temperature. The best performing working fluid was found as benzene for ORC turbine inlet pressure between 10 bar and 25 bar. Above 25 bar ORC-turbine inlet pressure, R123 showed the highest performance. The maximum ORC net power production, thermal and exergy efficiencies were found as 1076.76 kW, 21.14% and 47.00% for ORC used R123 at 230 °C and 35 bar. However, although ORC with R123 has the highest net power production, the payback periods of ORC with R11 is minimum (2.5 years). At this ORC turbine inlet parameters, performance parameters of the cogeneration system were found the highest as thermal efficiency 69.19% and exergy efficiency 75.51%.

Abstract In this study, a novel organic fluid-filled regenerative heat exchanger used heat recovery ventilation (OHeX-HRV) system was designed. Five organic-based fluids (R11, R123, R245fa, n-Pentane and Isopentane) were selected by considering operating conditions. Indoor air exit temperature, outdoor air inlet temperature and recovered heat by regenerative heat exchanger were analysed depending on varying airspeeds ( V air = 1,2,3 m/s) and outdoor environment temperatures (0–40 °C). As a result of the study, it was observed that recovered heat decreased as the outdoor environment temperature approaches from 0 °C to comfort temperature of indoor environment (24 °C). In contrast, the amount of heat recovered increased as the outdoor environment temperature diverges from indoor comfort temperature. The amount of recovered energy increased directly related to increasing airspeed thanks to increasing air mass flow. Among selected working fluids, n-Pentane (10.812 kJ/kg) and Isopentane (10.716 kJ/kg) used OHeX-HRV system resulted in the highest energy recovery per unit air mass. From n-Pentane used OHeX-HRV system, hourly energy recovery was calculated as 426.22 kJ/h when airspeed was 3 m/s. After comprehensive analyses, it was concluded that n-Pentane which has also superiority in terms of safety and environmental impact showed the best heat recovering performance when used in proposed OHeX-HRV system.