Impact on Overall Efficiency of Component Efficiency Increases for an Existing Thermal Electrical Generating Station

2002 ◽  
Author(s):  
Marc A. Rosen
Keyword(s):  
Exergy Analysis ◽  
Large Temperature ◽  
Efficiency Improvement ◽  
Combustion Heat ◽  
Component Efficiency ◽  
Pertinent Information ◽  
Electrical Generator ◽  
Overall Efficiency ◽  
Exergy Analyses ◽  
Exergy Losses

Most electrical generating utilities are striving to improve the efficiencies of their existing thermal electric generating stations, many of which are old. Exergy methods have been shown to provide meaningful insights that can assist in increasing the efficiency of conventional coal-to-electricity technologies. Here, exergy analysis is used to assess measures for improving the efficiencies of coal-fired electrical generating stations. This scope of the study is limited to minor practical improvements, which can be undertaken with limited effort and cost and are not overly complex. The plant considered is the coal-fired Nanticoke Generating Station (GS) in Ontario, Canada. The findings suggest that the results of exergy analyses should be used, along with other pertinent information, to guide efficiency improvement efforts for thermal generating stations. Also, efficiency improvement efforts should focus on plant components responsible for the largest exergy losses: the steam generator (where large losses occur from combustion heat transfer across large temperature differences), the turbines, the electrical generator and the transformer. Possible improvements in these areas should be assessed in conjunction with other criteria, and other components should be considered where economically beneficial improvements can be identified.

Enthalpy and Exergy Analysis of Domestic Desiccant Air Conditioner With Cooling Dehumidification and Heating Humidification Using Process Simulator

2011 ◽  
Author(s):  
Shun Hirano ◽  
Yoshinori Hisazumi ◽  
Tsukasa Hori ◽  
Tsutomu Wakabayashi ◽  
Akira Kishimoto ◽  
...  
Keyword(s):  
Exergy Analysis ◽  
Cooling Capacity ◽  
Air Conditioner ◽  
Air Conditioners ◽  
Evaporative Cooler ◽  
Humidified Air ◽  
Process Simulator ◽  
Exergy Analyses ◽  
Direct Evaporative Cooler ◽  
Exergy Losses

To popularize the use of desiccant air conditioners in residences, a system that can supply cooled and dried air in summer as well as heated and humidified air in winter is proposed. An evaporative cooler that affords an increase in cooling capacity and the amount of humidification is used in this system. The results of the enthalpy and exergy analyses, performed using a process simulator, showed that significant exergy losses occurred at the blower, heater, and desiccant rotor. In addition, exergy loss occurred at the direct evaporative cooler in heating humidification. Furthermore, it was found that there exists an optimal water temperature that yields peak exergy efficiency from the desiccant rotor.

scholarly journals Comparative studies of Cu-Cl Thermochemical Water Decomposition Cyles for Hydrogen Production

2018 ◽  
Vol 61 ◽  
pp. 00009
Author(s):  
Funmilayo Osuolale ◽  
Oladipupo Ogunleye ◽  
Mary Fakunle ◽  
Abdulfataah Busari ◽  
Yetunde Abolanle
Keyword(s):  
Hydrogen Production ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Chemical Species ◽  
Efficiency Improvement ◽  
Water Decomposition ◽  
Step Cycle ◽  
Efficiency Increase ◽  
Production Stages ◽  
Parametric Studies

This research focuses on thermodynamic analysis of the copper chlorine cycles. The cycles were simulated using Aspen Plus software. All thermodynamic data for all the chemical species were defined from literature and the reliability of other compounds in the simulation were ascertained. The 5-step Cu–Cl cycle consist of five steps; hydrolysis, decomposition, electrolysis, drying and hydrogen production. The 4-step cycle combines the hydrolysis and the drying stage of the 5-step cycle to eliminate the intermediate production and handling of copper solids. The 3-step cycle has hydrolysis, electrolysis and hydrogen production stages. Exergy and energy analysis of the cycles were conducted. The results of the exergy analysis were 59.64%, 44.74% and 78.21% while that of the energy analysis were 50%, 49% and 35% for the 5-step cycle, 4-step cycle and 3-step cycle respectively. Parametric studies were conducted and possible exergy efficiency improvement of the cycles were found to be between 59.57-59.67%, 44.32-45.67% and 23.50-82.10% for the 5-step, 4-step and 3-step respectively. The results from the parametric analysis of the simulated process could assist ongoing efforts to understand the thermodynamic losses in the cycle, to improve efficiency, increase the economic viability of the process and to facilitate eventual commercialization of the process.

scholarly journals CFD-Exergy analysis of the flow in a small-sized Venturi

2020 ◽  
Vol 307 ◽  
pp. 01037
Author(s):  
Ahmed Razali ◽  
Mohammed Baghdad ◽  
Ahmed Ouadha
Keyword(s):  
Exergy Analysis ◽  
Velocity Gradients ◽  
Exergy Losses ◽  
Different Parts

The present study aims to compare cavitation models in predicting the flow in small-sized cavitating venturis. Three cavitation models, namely Schnerr and Sauer model, Zwart et al. Model and Singhal et al. Model have been compared under the mixture approach. Furthermore, the performance of this device has been assessed using the concept of exergy by quantifying the exergy losses accuring in its different parts. It is found that all models are capable of reproducing the physics of cavitation phenomena within the cavitating venturi. However, the Schnerr and Sauer model return higher values than the others model. It is also observed that most of the exergy losses occur in the converging and diverging parts of the venturi due to higher pressure and velocity gradients in these regions.

scholarly journals Exergy Analysis for Utilizing Latent Energy of Thermal Energy Storage System in District Heating

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1391 ◽  
Author(s):  
Joong Yong Yi ◽  
Kyung Min Kim ◽  
Jongjun Lee ◽  
Mun Sei Oh
Keyword(s):  
Power Generation ◽  
Energy Storage ◽  
Thermal Energy ◽  
Exergy Analysis ◽  
Heat Storage ◽  
Storage System ◽  
District Heating ◽  
Hydraulic Turbine ◽  
Storage Process ◽  
Exergy Losses

The thermal energy storage (TES) system stores the district heating (DH) water when the heating load is low. Since a TES system stores heat at atmospheric pressure, the DH water temperature of 115 °C has to be lowered to less than 100 °C. Therefore, the temperature drop of the DH water results in thermal loss during storage. In addition, the DH water must have high pressure to supply heat to DH users a long distance from the CHP plant. If heat is to be stored in the TES system, a pressure drop in the throttling valve occurs. These exergy losses, which occur in the thermal storage process of the general TES system, can be analyzed by exergy analysis to identify the location, cause and the amount of loss. This study evaluated the efficiency improvement of a TES system through exergy calculation in the heat storage process. The method involves power generation technology using the organic Rankine cycle (ORC) and a hydraulic turbine. As a result, the 930 kW capacity ORC and the 270 kW capacity hydraulic turbine were considered suitable for a heat storage system that stores 3000 m3/h. In this case, each power generation facility was 50% of the thermal storage capacity, which was attributed to the variation of actual heat storage from the annual operating pattern analysis. Therefore, it was possible to produce 1200 kW of power by recovering the exergy losses. The payback period of the ORC and the hydraulic turbine will be 3.5 and 7.13 years, respectively.

Exergy Analysis on a Split-Type Conditioner Using Ejector as an Expansion Device

2014 ◽  
Vol 699 ◽  
pp. 828-833 ◽  
Author(s):  
Sumeru ◽  
Markus ◽  
Farid Nasir Ani ◽  
Henry Nasution
Keyword(s):  
Performance Improvement ◽  
System Performance ◽  
Air Conditioning ◽  
Exergy Analysis ◽  
Energy Savings ◽  
Air Conditioner ◽  
Total Energy Consumption ◽  
Air Conditioning System ◽  
Air Conditioners ◽  
Exergy Losses

Air conditioning system consumes approximately 50% of the total energy consumption of buildings. Split-type air conditioner is the most widely used in residential and commercial buildings. As a result, enhancement on the performance of the air conditioners will yield a significant energy savings. The use of ejector as an expansion device on the split-type air conditioners is one method to increase the system performance. Exergy analysis on a split-type air conditioner uses an ejector as an expansion device at room and outdoor temperatures of 24 °C and 34 °C, respectively, yielded the percentage of exergy reduction up to 40.6%. Also, the exergy losses on in the compressor had the highest impact on the performance improvement of the split-type air conditioner.

The Energy and Exergy Efficiencies of Renewable Energy Utilization in a Building Stock

2013 ◽  
Vol 361-363 ◽  
pp. 335-338
Author(s):  
Xiao Chen
Keyword(s):  
Renewable Energy ◽  
Exergy Analysis ◽  
Hot Water ◽  
Energy Utilization ◽  
Efficiency Improvement ◽  
Building Stock ◽  
Domestic Hot Water ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Heating Mode

An surface water heat pump (SWHP) system and some solar domestic hot water (SDHW) systems were constructed in a building stock located in Xiangtan for the purpose of energy saving and environmental improvement. This study aims to evaluate the energy and exergy efficiencies of renewable energy utilization based on energy and exergy analysis. We found the energy and exergy efficiencies of the SWHP system in heating mode to be 395% and 17.78%, respectively. The energy and exergy efficiencies for the SDHW systems were found to be 34.96% and 17.5%, respectively. Some measures for the exergy efficiency improvement are discussed in this paper.

Efficiency Improvement of Centrifugal Reverse Pumps

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Shahram Derakhshan ◽  
Bijan Mohammadi ◽  
Ahmad Nourbakhsh
Keyword(s):  
Navier Stokes ◽  
Efficiency Improvement ◽  
Test Rig ◽  
Pump Impeller ◽  
Flow Solver ◽  
Wide Range ◽  
The World ◽  
Gradient Based ◽  
Overall Efficiency ◽  
Turbine Mode

Pumps as turbines have been successfully applied in a wide range of small hydrosites in the world. Since the overall efficiency of these machines is lower than the overall efficiency of conventional turbines, their application in larger hydrosites is not economical. Therefore, the efficiency improvement of reverse pumps is essential. In this study, by focusing on a pump impeller, the shape of blades was redesigned to reach a higher efficiency in turbine mode using a gradient based optimization algorithm coupled by a 3D Navier–Stokes flow solver. Also, another modification was done by rounding the blades’ leading edges and hub/shroud interface in turbine mode. After each modification, a new impeller was manufactured and tested in the test rig. The efficiency was improved in all measured points by the optimal design of the blade and additional modification as the rounding of the blade’s profile in the impeller inlet and hub/shroud inlet edges in turbine mode. Experimental results confirmed the numerical efficiency improvement in all measured points. This study illustrated that the efficiency of the pump in reverse operation can be improved just by impeller modification.

A Holistic Approach to GTCC Operational Efficiency Improvement Studies

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Sowande Z. Boksteen ◽  
Jos P. van Buijtenen ◽  
Dick van der Vecht
Keyword(s):  
Power Plants ◽  
Combined Cycle ◽  
Fuel Quality ◽  
Efficiency Improvement ◽  
Ambient Conditions ◽  
Operational Parameters ◽  
Decision Variables ◽  
Wide Range ◽  
Exergy Losses ◽  
Plant Efficiency

Because of the increasing share of renewables in the energy market, part load operation of gas turbine combined cycle (GTCC) power plants has become a major issue. In combination with the variable ambient conditions and fuel quality, load variations cause these plants to be operated across a wide range of conditions and settings. However, efficiency improvement and optimization studies are often focused on single operating points. The current study assesses efficiency improvement possibilities for the KA26 GTCC plant, as recently built in Lelystad, The Netherlands, taking into account that the plant is operated under frequently varying conditions and load settings. In this context, free operational parameters play an important role: these are the process parameters, which can be adjusted by the operator without compromising safety and other operational objectives. The study applies a steady state thermodynamic model with second-law analysis for exploring the entire operational space. A method is presented for revealing correlations between the exergy losses in major system components, indicating component interactions. This is achieved with a set of numerical simulations, in which operational conditions and settings are randomly varied, recording plant efficiency and exergy losses in major components. The resulting data is used to identify distinct operational regimes for the GTCC. Finally, the free operational parameters are used as decision variables in a genetic algorithm, optimizing plant efficiency in the operational regimes identified earlier. The results show that the optimal settings for decision variables depend on the regime of operation.

scholarly journals EXERGIC EFFICIENCY OF THE HEAT RECOVERY UNIT FOR WASTE GASES OF A HEAT ENGINE OF A COGENERATION PLANT

2020 ◽  
Vol 42 (3) ◽  
pp. 56-60
Author(s):  
N. Fialko ◽  
A. Stepanova ◽  
R. Navrodskaya ◽  
S. Shevchuk
Keyword(s):  
Heat Exchanger ◽  
Heat Recovery ◽  
Exergy Analysis ◽  
Heat Engine ◽  
Cogeneration Plant ◽  
Advantages And Disadvantages ◽  
Recovery Unit ◽  
Recovery Schemes ◽  
Exergy Losses ◽  
Complex Methods

The paper presents the results of a study of the efficiency of a heat recovery unit for waste gases of a heat engine of a cogeneration plant. The possibilities of using for this purpose the discrete-modular principle and complex methods of analyzing the efficiency of heat recovery systems, which are based on the methods of exergo-dissipative functions and exergic balances, are analyzed. The design features of the heat exchanger are considered and a conclusion is made about the possibility of presenting it as a system of eight discrete modules. The results of calculating the exergy characteristics for each of the eight heat exchanger modules, performed within the framework of the indicated methods, are presented. A regular decrease in exergy losses and heat-exergy criterion of efficiency is observed during the transition from the first to the eighth module of the heat recovery unit. However, exergy characteristics for the third and fourth modules of the heat exchanger are somewhat higher than the indicated dependence suggests. This indicates the thermodynamic imperfection of these modules. The main exergy losses in all heat exchanger modules are associated with losses due to heat transfer from flue gases to the wall. An insignificant discrepancy between the values ​​of the total exergy losses calculated within the framework of the methods used indicates that both methods can be used in various heat recovery schemes. However, in each specific case, it is necessary to choose a methodology with which it is possible to identify individual elements that need optimization or constructive improvement. Particular attention is paid to the comparative analysis of the selected techniques and consideration of the advantages and disadvantages of their use in various cases. It is noted that the technique based on the integral balance method of exergy analysis can be considered effective due to the small number of initial parameters and the simplicity of the analytical and calculation methods. The advantage of the technique using exergo-dissipative functions is that it allows one to differentiate exergy losses in a heat exchanger and establish the causes and areas of their localization.

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