Abstract
In the context of energy utilization it is required to harvest maximum possible potential from the available energy sources. Therefore analysis, monitoring and optimization of available energysources and in particular those related to power plants are major requirement in the sector. Generally the energy performances of power plant are evaluated using criteria based on 1st law of thermodynamics. However, subsequent development in the field of thermodynamic studies in particular the exergy analysis was identified as a useful method to design, evaluation, optimization and improvement of power plant performance. It is based on 2nd law of thermodynamics. In this study, it is aimed to find out the potential of exergy efficiency improvement opportunities in coal power plants through exergy flow analysis. A methodology was developed to estimate exergy flows in coal power plants and efficiencies of major equipment in power plant employing 2nd law or exergy analysis. This was done according to general equations which are used in thermodynamics. As a result, set of equations pertaining to the thermodynamics behaviours was established to analyse exergy flows in coal power plants. The methodology was then applied to unit 01 of Lak Vijaya power station (LVPS) in Sri Lanka as a case study. In the process, thermodynamic properties of water-steam cycle of LVPS unit 01 under both design and actual calculation were used to evaluate exergy values of critical states of the cycle as well as the resulting exergy flows and related efficiencies of major equipment. Boiler was identified as the major exergy destruction equipment in power plant and consequently it has less exergy efficiency. Hence boiler sub system was analysed to identify potential of exergy efficiency improvement in coal power plants. The main parameters of boiler were used to identify the exergy flow behaviours of the boiler. An economic analysis was also done for the boiler to identify the benefits. Not only steam generating cost saving in power plant but also reduction of hazardous CO2 emission calculations were carried out.
Highlights
Most of the power plants are designed by the energy performance criteria based on first law of thermodynamics for maximum operating efficiency
The result of Exergy Analysis (2nd law thermodynamic analysis) of coal power plants can indicate the real thermodynamic losses in power generation process and could be employed to find out the improvement required area to improve the efficiency of system
Potential of exergy efficiency improvement in coal power plant is directly related to reduction of exergy destruction in overall power plant
Summary
Most of the power plants are designed by the energy performance criteria based on first law of thermodynamics for maximum operating efficiency. An exergy analysis is a very powerful technique of optimize complex thermodynamic systems by not considering only the maximizing the 1st law efficiency but rather optimizing the operation considering the output, losses, degradation and destruction of the potential and the quality. Exergy is normally destroyed when a process is involved depending on the nature of the process such as level of irreversibility and operating parameters. This destruction is proportional to the entropy increase of the system together with its surroundings. Second law analysis is about understanding irreversibilities in systems It focuses on changes in the quality of energy. The result of Exergy Analysis (2nd law thermodynamic analysis) of coal power plants can indicate the real thermodynamic losses in power generation process and could be employed to find out the improvement required area to improve the efficiency of system
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