Modeling and supervisory control design for a combined cycle power plant

The traditional control strategy based on PID controllers may be unsatisfactory when dealing with processes with large time delay and constraints. This paper presents a supervisory model based constrained predictive controller (MPC) for a combined cycle power plant (CCPP). First, a non-linear dynamic model of CCPP using the laws of physics was proposed. Then, the supervisory control using the linear constrained MPC method was designed to tune the performance of the PID controllers by including output constraints and manipulating the set points. This scheme showed excellent tracking and disturbance rejection results and improved performance compared with a stand-alone PID controller’s scheme

New techniques for the analysis of flexible operation of gas turbine based systems

In the current European energy market, gas power plants are required to operate in cyclical modes to fill the gaps in renewable energy supply. Renewable sources have dispatch priority due to their relatively low variable operational costs. However, because of their high unpredictability, conventional power plants such as Combined Cycle Power Plants (CCPP) now operate with frequent load changes to fill the gaps in supply by participating in the balancing market. Substantial efforts to develop innovative solutions to the new challenges are invested by the commercial and research community, where investigation into improving understanding of complex part-load operation is of utmost techno-economical importance. To date, main techniques used to simulate part-load operation of CCPPs were developed in the late twentieth century and are based on cumbersome and iterative methods requiring initial approximation of variables. In the wake of recent large scale renewable power installations, these techniques are not effective enough to carry complex optimisation studies to adopt CCPPs to quickly evolving market conditions. A number of improvements have been proposed; however, these modified methods are not able to cope with the required complexity and flexibility of studying various component layout optimisations and their impact on techno-economic performance. The current work pursues a novel method for part-load performance estimation of CCPPs, which is less complex, more effective, and can be seamlessly applied to any further optimisation studies. Initially the technique has been developed based on binarycoded genetic algorithm. The method enables simulation of part-load performance without the need for making initial guess of variables, thus simplifying the procedure. The method has been validated against commercial software showing good agreement in the results. However, it has been concluded that the method does not provide a long term benefit to the research community because it is fundamentally based on search space iterations with unavoidable residual (error) in the solution, and requiring significant computational time. The complex optimisation studies conducted by other authors require a much simpler and flexible method. This led to the development of a novel Direct Solution Method (DSM), which provides a simple solution with zero residual without need for cumbersome iterations. The DSM has been validated against commercial software showing good agreement; thus proving to be a promising alternative to the existing techniques. To improve understanding of part-load gas turbine operation, a set of comprehensive maps have been developed. A Gas Turbine Operational Map allows study and visualisation of complex trade-offs arising from gas turbine load reduction strategies. The load change strategy will determine the life consumption of critical gas turbine components, which led to the development of a Life Consumption Map which takes into account low cycle fatigue and creep mechanisms

Lost in optimisation of water distribution systems? A literature review of system operation

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Optimisation of the operation of water distribution systems has been an active research field for almost half a century. It has focused mainly on optimal pump operation to minimise pumping costs and optimal water quality management to ensure that standards at customer nodes are met. This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly optimal pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiquality water distribution systems. Uniquely, it also contains substantial and thorough information for over one hundred publications in a tabular form, which lists optimisation models inclusive of objectives, constraints, decision variables, solution methodologies used and other details. Research challenges in terms of simulation models, optimisation model formulation, selection of optimisation method and postprocessing needs have also been identified

Thermal performance and economic analysis of supercritical carbon dioxide cycles in combined cycle power plant

A closed-loop, indirect, supercritical Carbon Dioxide (sCO2) power cycle is attractive for fossil-fuel, solar thermal and nuclear applications owing to its ability to achieve higher efficiency, and compactness. Commercial Gas Turbines (GT’s) are optimised to yield maximum performance with a conventional steam Rankine cycle. In order to explore the full potential of a sCO2 cycle the whole plant performance needs to be considered. This study analyses the maximum performance and cost of electricity for five sCO2 cascaded cycles. The plant performance is improved when the GT pressure ratio is considered as a design variable to a GT to optimise the whole plant performance. Results also indicate that each sCO2 Brayton cycle considered, attained maximum plant efficiency at a different GT pressure ratio. The optimum GT pressure ratio to realise the maximum cost reduction in sCO2 cycle was higher than the equivalent steam Rankine cycle. Performance maps were developed for four high efficient cascaded sCO2 cycles to estimate the specific power and net efficiency as a function of GT turbine inlet temperature and pressure ratio. The result of multi-objective optimisation in the thermal and cost (c$/kWh) domains and the Pareto fronts of the different sCO2 cycles are presented and compared. A novel sCO2 cycle configuration is proposed that provides ideal-temperature glide at the bottoming cycle heat exchangers and the efficiency of this cycle, integrated with a commercial SGT5-4000F machine in lieu of a triple-pressure steam Rankine cycle, is higher by 1.4 percentage point

Development of electrical resistivity imaging methods for geological and archaeological prospecting

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Thermodynamic and economic analysis of performance evaluation of all the thermal power plants : a review

Surging in energy demand makes it necessary to improve performance of plant equipment and optimize operation of thermal power plants. Inasmuch as thermal power plants depend on fossil fuels, their optimization can be challenging due to the environmental issues which must be considered. Nowadays, the vast majority of power plants are designed based on energetic performance obtained from first law of thermodynamic. In some cases, energy balance of a system is not appropriate tool to diagnose malfunctions of the system. Exergy analysis is a powerful method for determining the losses existing in a system. Since exergy analysis can evaluate quality of the energy, it enables designers to make intricate thermodynamic systems operates more efficiently. These days, power plant optimization based on economic criteria is a critical problem because of their complex structure. In this study, a comprehensive analysis including energy, exergy, economic (3-E) analyses, and their applications related to various thermal power plants are reviewed and scrutinized.The National Natural Science Foundation of China, Hubei Provincial Natural Science Foundation of China, Key Project of ESI Discipline Development of Wuhan University of Technology and the Scientific Research Foundation of Wuhan University of Technology.https://onlinelibrary.wiley.com/journal/20500505am2020Mechanical and Aeronautical Engineerin

Design Optimization and Dynamic Simulation of Steam Cycle Power Plants: A Review

After more than one century from its first use for electric power production, steam cycles are still the object of continuous research and development efforts worldwide. Indeed, owing to its favorable thermodynamic properties, steam cycles are not only used in coal-fired power plants but in a large variety of applications such as combined cycles, concentrated solar power plants and polygeneration plants. On the other hand, to cope with the efficiency and flexibility requirements set by today’s energy markets, the design and the operation of steam cycles must be carefully optimized. A key rule is played by the simulation and optimization codes developed in the last 30 years. This paper provides an introduction to the main types of simulation and optimization problems (design, off-design operation and dynamic), an overview of the mathematical background (possible solution approaches, numerical methods and available software), and a review of the main scientific contributions

Thermo-economic analysis for optimal selection of desalination techniques based on combined cycle power plant

PhD ThesisScarcity of water has become a challenging problem for countries in arid and semi-arid regions. Seawater desalination is considered to be one of the main sources of potable water in areas such as the Middle East and North Africa, with dependency on desalination reaching 90% in some of the Gulf Cooperation Council (GCC) countries. Libya is one of those counties which suffers from a lack of natural water resources. This study focuses on the prospect of coupling desalination plants with existing Combined Cycle Power Plant (CCPP) to produce potable water. This study was based on seawater in the north of Libya and on a source of brackish water in the south of Libya at Waddan City. The study begins by considering the improvement that could be achieved in CCPP performance by cooling the inlet air using a waste heat driven Absorption Chiller (AC) and then continues to determine the optimal selection of the desalination technique suitable for the environmental conditions in Libya. The methodology depends on validated simulation models developed from IPSEpro software. The CCPP model was validated against vendor data and the AC was validated against manufacturer data. Different desalination units, Multi-Effect Desalination with Thermal Vapour Compression (MED-TVC), two-pass Reverse Osmosis (RO) and Single Effect Desalination (SED) desalination systems were modelled and validated against actual operation data. After validation the performance of each model was investigated from energy, exergy and economic standpoints for design and off-design conditions using real Libyan environmental data. This study has, for the first time, compared the exergy efficiency, power consumption and economic characteristics of different configurations of two-pass RO with energy recovery devices such as a Pressure Exchanger (PX) and an Energy Recovery Turbine (ERT). The results shows that when PX is used in the first and second stages of RO the exergy efficiency increases by 81% and the specific power consumption declines of more than 100%. MED-TVC Gain Output Ratio (GOR) and exergy efficiency are improved by adding a preheater on the distillate water stream to increase the feed water temperature, and the amount of steam extracted from the CCPP is reduced. A comparison between two-pass RO or MED-TVC coupled with a CCPP has been carried out using thermodynamic and economic analysis. The result shows that the N. M. Eshoul PhD Thesis ii Newcastle Uinversity power plant exergy efficiency deceases by about 4% when MED-TVC desalination plant is coupled with a CCPP but only 0.5% when RO is coupled with a CCPP. Also the net power output declines by about 22.5MW when MED-TVC desalination is used but only 5MW when the CCPP is coupled with a RO with PX desalination plant. In addition, economic analysis shows that RO desalination is a better process compared with MED-TVC, either standalone or coupled with CCPP. An exergy and economic analysis of two different desalination technologies to produce drinking water from brackish water was investigated. The analysis shows that the exergy efficiency of a single-pass RO unit is nearly double that of single effect desalination and the cost of water produced by a single effect desalination unit is higher than that of a single-pass reverse osmosis unit by about 60%. This confirms that reverse osmosis is the suitable desalination system in Libya.Ministry of Education and the Cultural Affairs Department of the Libyan Embassy in London for providing managerial and financial suppor