scholarly journals Optimization of ORC Power Plants for Geothermal Application in Kenya by Combining Exergy and Pinch Point Analysis

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6579
Author(s):  
Alvin Kiprono Bett ◽  
Saeid Jalilinasrabady
Keyword(s):  
Flow Rate ◽  
Power Output ◽  
Geothermal Energy ◽  
Power Plants ◽  
Working Fluid ◽  
Pinch Point ◽  
Turbine Inlet ◽  
Point Analysis ◽  
Condenser Temperature ◽  
Installed Capacity

Geothermal energy is a sustainable renewable source of energy. The installed capacity of geothermal energy in Kenya is 847.4 MWe of the total 2.7 GWe. This paper presents the effect of six different working fluids to optimize the geothermal of 21.5 MWe of reinjected brine at a single-flash power plant in Kenya. Engineering Equation Solver (EES) code was used to design and optimize simple organic Rankine (ORC) and regenerative cycles. The objective was to combine pinch point analysis and exergy analysis for the optimum utilization of geothermal energy by varying the turbine inlet pressure, pinch point, and reinjection temperature. The turbine inlet pressures, and pinch points were varied to obtain optimum pressures for higher net power output and exergy efficiencies. As the pressure increased, the efficiencies and net power generated increase to optimal at turbine inlet pressures between 2000 and 3000 kPa. By maintaining a condenser temperature at 46.7 °C, the turbine outlet pressures were 557.5 kPa for isobutene, 627.4 kPa for isobutane, 543.7 kPa for butene, 438.9 kPa for trans-2-butene, 412.3 kPa for R236ea, and 622.9 kPa for R142b. For the pinch point of 10 °C, the working fluid with a lower net power is trans-2-butene at 5936 kW for a flow rate of 138.8 kg/s and the highest reinjection at 89.05 °C. On the other hand, R236ae had a flow rate of 398.2 kg/s, a higher power output of 7273 kW, and the lowest reinjection temperature of 73.47 °C for a 5 °C pinch point. In the pinch point consideration, the suitable fluid will depend on the best reinjection temperatures. The pinch point affects the heat transfer rates and effectiveness in the heat exchangers. The best pinch point is 10 °C, since the reinjection temperatures are the highest between 83 and 89 °C. The analysis showed that for unlimited reinjection temperatures, basic ORC is suitable. The regenerative cycle would be best suited where reinjection temperature is constrained by brine geochemistry.

Analysis and Comparison of the Performance of an Inverted Brayton Cycle and Turbo-Compounding With Decoupled Turbine and CVT Driven Compressor for Small Automotive Engines

2016 ◽  
Author(s):  
P. Lu ◽  
C. Brace ◽  
B. Hu ◽  
C. Copeland
Keyword(s):  
Fuel Consumption ◽  
Power Output ◽  
Heat Recovery ◽  
Power Plants ◽  
Waste Heat ◽  
Ambient Pressure ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Partial Load ◽  
Exhaust Heat

For an internal combustion engine, a large quantity of fuel energy (accounting for approximately 30% of the total combustion energy) is expelled through the exhaust without being converted into useful work. Various technologies including turbo-compounding and the pressurized Brayton bottoming cycle have been developed to recover the exhaust heat and thus reduce the fuel consumption and CO2 emission. However, the application of these approaches in small automotive power plants has been relatively less explored because of the inherent difficulties, such as the detrimental backpressure and higher complexity imposed by the additional devices. Therefore, research has been conducted, in which modifications were made to the traditional arrangement aiming to minimize the weaknesses. The turbocharger of the baseline series turbo-compounding was eliminated from the system so that the power turbine became the only heat recovery device on the exhaust side of the engine, and operated at a higher expansion ratio. The compressor was separated from the turbine shaft and mechanically connected to the engine via CVT. According to the results, the backpressure of the novel system is significantly reduced comparing with the series turbo-compounding model. The power output at lower engine speed was also promoted. For the pressurized Brayton bottoming cycle, rather than transferring the thermal energy from the exhaust to the working fluid, the exhaust gas was directly utilized as the working medium and was simply cooled by ambient coolant before the compressor. This arrangement, which is known as the inverted Brayton cycle was simpler to implement. Besides, it allowed the exhaust gasses to be expanded below the ambient pressure. Thereby, the primary cycle was less compromised by the bottoming cycle. The potential of recovering energy from the exhaust was increased as well. This paper analysed and optimized the parameters (including CVT ratio, turbine and compressor speed and the inlet pressure to the bottoming cycle) that are sensitive to the performance of the small vehicle engine equipped with inverted Brayton cycle and novel turbo-compounding system respectively. The performance evaluation was given in terms of brake power output and specific fuel consumption. Two working conditions, full and partial load (10 and 2 bar BMEP) were investigated. Evaluation of the transient performance was also carried out. Simulated results of these two designs were compared with each other as well as the performance from the corresponding baseline models. The system models in this paper were built in GT-Power which is a one dimension (1-D) engine simulation code. All the waste heat recovery systems were combined with a 2.0 litre gasoline engine.

Performance Optimization and Economic Analysis of Geothermal Power Generation by Subcritical and Supercritical Organic Rankine Cycles

2016 ◽  
Author(s):  
Changwei Liu ◽  
Tieyu Gao ◽  
Jiangnan Zhu ◽  
Jiamin Xu
Keyword(s):  
Economic Analysis ◽  
Power Output ◽  
Performance Optimization ◽  
Supercritical Condition ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Working Fluids ◽  
Turbine Inlet ◽  
Net Power Output ◽  
Subcritical Condition

In a sustainability context, using renewable energy sources to hedge against increasing consumption of fossil fuels and reduce greenhouse gas emissions becomes increasingly important. The geothermal resource has a great application prospect due to its rich reserves and convenient utilization, and Organic Rankine Cycle (ORC) is a effective method to convert the low-grade geothermal to electricity. To improve the performance of geothermal ORC system, working fluid selection, system parameter optimization and the cycle design are the main approaches. Zeotropic mixtures may show superiority as ORC working fluids due to the temperature glides during the phase transitions, which leads to better temperature matches between the working fluid and the heat source/sink. Moreover, owing to the changing temperature during the transition from liquid to vapor in the vapor generator, supercritical ORC provides a great potential in geothermal utilization and irreversibility reduction. This paper displays an investigation on the performance optimization and economic analysis of various working fluids under subcritical and supercritical conditions. To avoid the silica oversaturation, the geothermal water reinjection temperature should not be less than 70 °C. Turbine inlet temperature, condenser outlet temperature as well as turbine inlet pressure (for supercritical ORC) are optimized to maximize the net power output. Moreover, economic analysis is conducted by taking heat exchanger area per unit power output (APR) and the specific investment cost (SIC) as indicators under the optimal net power output condition. The results shows that working fluid with a medium critical temperature yields greater net power output in supercritical ORC and mixture produces larger net power output compared with its pure components in subcritical ORC. Compared with isobutane (R600a) under subcritical condition, isobutane/isopentane (R600a/R601a) and isobutane/pentane (R600a/R601) under subcritical condition, R134a and R1234ze(E) under supercritical condition yield 3.9%, 3.8%, 8.5% and 8.8% more net power outputs, respectively. In addition, R600a/R601a and R600a/R601 under subcritical condition own higher APR and SIC while R134a and R1234ze(E) under supercritical condition possess lower APR and SIC.

scholarly journals Simulation of Producer Gas Fired Power Plants with Inlet Fog Cooling and Steam Injection

2006 ◽  
Vol 129 (3) ◽  
pp. 637-647 ◽  
Author(s):  
Mun Roy Yap ◽  
Ting Wang
Keyword(s):  
Natural Gas ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Power Output ◽  
Power Plants ◽  
Steam Injection ◽  
Combined Cycle ◽  
Producer Gas ◽  
Turbine Inlet ◽  
Cycle Systems

Biomass can be converted to energy via direct combustion or thermochemical conversion to liquid or gas fuels. This study focuses on burning producer gases derived from gasifying biomass wastes to produce power. Since the producer gases are usually of low calorific values (LCV), power plant performance under various operating conditions has not yet been proven. In this study, system performance calculations are conducted for 5MWe power plants. The power plants considered include simple gas turbine systems, steam turbine systems, combined cycle systems, and steam injection gas turbine systems using the producer gas with low calorific values at approximately 30% and 15% of the natural gas heating value (on a mass basis). The LCV fuels are shown to impose high compressor back pressure and produce increased power output due to increased fuel flow. Turbine nozzle throat area is adjusted to accommodate additional fuel flows to allow the compressor to operate within safety margin. The best performance occurs when the designed pressure ratio is maintained by widening nozzle openings, even though the turbine inlet pressure is reduced under this adjustment. Power augmentations under four different ambient conditions are calculated by employing gas turbine inlet fog cooling. Comparison between inlet fog cooling and steam injection using the same amount of water mass flow indicates that steam injection is less effective than inlet fog cooling in augmenting power output. Maximizing steam injection, at the expense of supplying the steam to the steam turbine, significantly reduces both the efficiency and the output power of the combined cycle. This study indicates that the performance of gas turbine and combined cycle systems fueled by the LCV fuels could be very different from the familiar behavior of natural gas fired systems. Care must be taken if on-shelf gas turbines are modified to burn LCV fuels.

Optimum Performance Improvements of the Combined Cycle Based on an Intercooler–Reheated Gas Turbine

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Thamir K. Ibrahim ◽  
M. M. Rahman
Keyword(s):  
Gas Turbine ◽  
Power Output ◽  
Thermal Efficiency ◽  
Power Plants ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Optimum Level ◽  
Simulation Code ◽  
Operation Conditions ◽  
Turbine Inlet

The performance enhancements and modeling of the gas turbine (GT), together with the combined cycle gas turbine (CCGT) power plant, are described in this study. The thermal analysis has proposed intercooler–reheated-GT (IHGT) configuration of the CCGT system, as well as the development of a simulation code and integrated model for exploiting the CCGT power plants performance, using the matlab code. The validation of a heavy-duty CCGT power plants performance is done through real power plants, namely, MARAFIQ CCGT plants in Saudi Arabia with satisfactory results. The results from this simulation show that the higher thermal efficiency of 56% MW, while high power output of 1640 MW, occurred in IHGT combined cycle plants (IHGTCC), having an optimal turbine inlet temperature about 1900 K. Furthermore, the CCGT system proposed in the study has improved power output by 94%. The results of optimization show that the IHGTCC has optimum power of 1860 MW and thermal efficiency of 59%. Therefore, the ambient temperatures and operation conditions of the CCGT strongly affect their performance. The optimum level of power and efficiency is seen at high turbine inlet temperatures and isentropic turbine efficiency. Thus, it can be understood that the models developed in this study are useful tools for estimating the CCGT power plant's performance.

scholarly journals Comparison of single and double stage regenerative organic rankine cycle for medium grade heat source through energy and exergy estimation

2019 ◽  
Vol 8 (2) ◽  
pp. 141 ◽  
Author(s):  
Ghalya Pikra ◽  
Nur Rohmah
Keyword(s):  
Heat Source ◽  
Flow Rate ◽  
Power Output ◽  
Thermal Efficiency ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Energy And Exergy ◽  
Net Power Output

Regenerative organic Rankine cycle (RORC) can be used to improve organic Rankine cycle (ORC) performance. This paper presents a comparison of a single (SSRORC) and double stage regenerative organic Rankine cycle (DSRORC) using a medium grade heat source. Performance for each system is estimated using the law of thermodynamics I and II through energy and exergy balance. Solar thermal is used as the heat source using therminol 55 as a working fluid, and R141b is used as the organic working fluid. The initial data for the analysis are heat source with 200°C of temperature, and 100 L/min of volume flow rate. Analysis begins by calculating energy input to determine organic working fluid mass flow rate, and continued by calculating energy loss, turbine power and pump power consumption to determine net power output and thermal efficiency. Exergy analysis begins by calculating exergy input to determine exergy efficiency. Exergy loss, exergy destruction at the turbine, pump and feed heater is calculated to complete the calculation. Energy estimation result shows that DSRORC determines better net power output and thermal efficiency for 7.9% than SSRORC, as well as exergy estimation, DSRORC determines higher exergy efficiency for 7.69%. ©2019. CBIORE-IJRED. All rights reserved

scholarly journals STUDI AWAL KARAKTERISTIK TEMPERATUR DAN TEKANAN PADA ALIRAN SIRKULASI ALAM DI FASILITAS UJI UNTAI FASSIP-02 MENGGUNAKAN SIMULASI CFD

POROS ◽  
2018 ◽  
Vol 16 (1) ◽  
Author(s):  
Ainur Roidi Rosidi
Keyword(s):  
Flow Rate ◽  
Power Plants ◽  
Heat Dissipation ◽  
Cfd Simulation ◽  
Reactor Core ◽  
Heat Removal ◽  
Test Facility ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Heating Section

TFASSIP-02 loop is a test facility that is used for research and development of safety technologies for future nuclear power plants based on natural law. This test facility is designed to study natural circulation phenomena caused by differences in fluid density due to temperature differences in the one-phase heat dissipation system during the simulation of heat removal from the reactor core when an accident occurs. FASSIP-02 loop consists of piping components, water heating tanks, water cooling tanks and expansion tanks. The purpose of this study was to understand the conditions of temperature change and pressure of water working fluid based on temperature changes in the heater section which were simulated on the loop geometry FASSIP-02. The research method was carried out in a simulation of Computational Fluid Dynamics using FLUENT 6.3 software. The working fluid in the FASSIP-02 loop uses water with a temperature of 27°C, the flow rate is varied 0.3 m/s and 0.45 m / s, while the temperature in the heating section is 70°C. CFD simulation results show that the increase in the working fluid temperature of the water with a flow rate of 0.3 m/s after passing through the heating section is 39°C, while the temperature increase of the working fluid of the water with a flow rate of 0.45 m/s is 36.6°C. Pressure drops at flow rates of 0.3 m/s and 0.45 m/s each occur in water working fluid before entering through WHT and after passing through the heating section. 

scholarly journals A Project To Estimate The Power Capacity Of Geothermal Power Plants Based On The Enthalpy Of Geothermal Fluid And Plant Design

2021 ◽  
Author(s):  
Obumneme Oken
Keyword(s):  
Power Plant ◽  
Power Output ◽  
Geothermal Energy ◽  
Power Plants ◽  
Hot Water ◽  
Geothermal Resource ◽  
Power Capacity ◽  
Geothermal Fluid ◽  
Single Flash ◽  
Geothermal Power

Surface phenomena that signal the presence of viable geothermal energy can be found in various locations in Nigeria. None of these locations have been explored extensively to determine the feasibility of sustainable geothermal energy development for electricity generation or direct heating purposes. In this context, the present study aims to provide insight into the energy potential of such development based on the enthalpy estimation of geothermal reservoirs. This particular project was conducted to determine the power output from a geothermal resource given an estimated enthalpy of the geothermal fluid. The process route chosen for this project is the single-flash geothermal power plant because of the temperature (180℃) and unique property of the geothermal fluid (a mixture of hot water and steam that exists as a liquid under high pressure). The Ikogosi warm spring in Ekiti State, Nigeria was chosen as the site location for this power plant. To support food security efforts in Africa, this project proposes the cascading of a hot water stream from the flash tank to serve direct heat purposes in agriculture for food preservation, before re-injection to the reservoir. The flowrate of the geothermal fluid to the flash separator was chosen as 3125 tonnes/hr. The power output from a single well using a single flash geothermal plant was evaluated to be 11.3 MW*. This result was obtained by applying basic thermodynamic principles, including material balance, energy balance, and enthalpy calculations. This particular project is a prelude to a robust model that will accurately determine the power capacity of geothermal power plants based on the enthalpy of geothermal fluid, size of the geothermal resource, and different plant designs. I hope that the knowledge gained from the study will promote best practices in geothermal engineering and emphasize appropriate planning for, and implementation of, geothermal plants.

A Novel Pinch Point Design Methodology Based Energy and Economic Analyses of Organic Rankine Cycle

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Jahar Sarkar
Keyword(s):  
Heat Source ◽  
Power Output ◽  
Capital Cost ◽  
Design Parameters ◽  
Working Fluid ◽  
Pinch Point ◽  
Component Size ◽  
Unit Power ◽  
Isentropic Efficiency ◽  
Source And Sink

A generalized methodology for pinch point design and optimization of subcritical and transcritical organic Rankine cycles (ORCs) using both wet and dry fluids is adopted in this study. The presented algorithm can predict the pinch point location in evaporator and condenser simultaneously and optimize the evaporator pressure for best performance with various heat source and sink conditions. Effects of pinch point temperature difference (PPTD), isentropic efficiency, subcooling, superheating and regenerator on the energy and economic performances are discussed for selected working fluids. System yields similar optimum design for both maximum power generation and minimum capital cost per unit power. At optimum condition, ammonia is best in terms of higher thermal efficiency and lower component size, R152a is best in terms of higher net power output and heat recovery efficiency (11.1%), and toluene is best in terms of lower capital cost and cost per unit power output (7060 $/kW). Effect of heat source and sink parameters on both energy and economic performances is significant. Contour plots are presented to select the best ORC design parameters for available heat source condition. PPTD and expander isentropic efficiency have significant effect on performances. However, the effect of subcooling, superheating and regenerator depends on working fluid.

Theoretical and Experimental Evaluation of the EvGT-Process

2000 ◽  
Author(s):  
Torbjörn O. Lindquist ◽  
Per M. Rosén ◽  
Tord Torisson
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
Power Output ◽  
Pilot Plant ◽  
Power Plants ◽  
Saturation Temperature ◽  
Combined Cycle ◽  
Small Scale ◽  
Pinch Point ◽  
Gas Turbine Cycle

Abstract In recent years the interest for new advanced thermodynamical gas turbine cycles has increased. One of the new designs is the evaporative gas turbine cycle. A lot of effort worldwide has been put into predicting the possible efficiency, pollutants, and dynamic behaviour of the evaporative gas turbine cycle, but all results so far have been affected by uncertain assumptions. Until now this cycle has not been demonstrated in a pilot plant. The purpose of this work has been to identify the potential of this cycle, by erecting a pilot plant at the Lund Institute of Technology. The project was financed on a 50/50 basis from the Swedish National Energy Administration and the industrial partners. Three different thermodynamical cycles have been tested in the pilot plant: the simple, the recuperative, and the evaporative cycles. The final pilot plant roughly consists of a 600 kW gas turbine, a hydraulic brake, a recuperator, a humidification tower, an economiser, and a flue gas condenser. All layout and functional analysis were made within the project. The pilot plant is, however, optimized neither for best efficiency nor for best emissions. It has only been built for demonstration purpose. It has been shown from the performance tests that the efficiency for the simple, recuperative, and evaporative cycles are 22, 27, and 35%, respectively, at rated power output. The NOx emissions were reduced by 90% to under 10 ppm, and the UHC and CO were not measurable when running the evaporative cycle at rated power output. The performance of the humidification tower was better than expected. The humidified air out from the humidification tower is always saturated. The pinch point, i.e. the temperature difference between the outcoming water from the humidification tower and the saturation temperature of the incoming air, is around 3°C. The water circuit was closed, i.e. there was no need for additional water, when the flue gases after the flue gas condenser reached a temperature of 35° C. The inhouse heat balance program, used for both cycle optimization and evaluation, has been verified. The evaporative gas turbine cycle has, when optimized, at least the same efficiency as the best combined cycle today, based on the same gas turbine. The evaporative cycle will also show very good performance when used in small scale power plants.

scholarly journals Geothermal Power: Factors affecting the performance of Binary Plants

2015 ◽  
Vol 2 ◽  
pp. 32-49
Author(s):  
Izabela Domanski ◽  
Matthew Cappadona ◽  
Oliver Fuller ◽  
Zeb Krix
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Power Output ◽  
Power Plants ◽  
Plant Performance ◽  
Factors Affecting ◽  
Binary Cycle ◽  
Well Depth ◽  
And Performance

A meta-study is conducted investigating the effect of plant parameters on the power output and efficiency of geothermal binary cycle power plants. Production well depth, geofluid temperature and mass flow rate are the parameters considered. An increase in mass flow rate is shown to increase both power output and efficiency. It is shown that a distinction can be made between two basic types of binary plants based off of mass flow and performance data. The well depth is shown to have no effect on plant performance. In addition, condenser parameters were investigated and the highest efficiency condenser system is determined.

Sign in / Sign up

Export Citation Format

Share Document