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In considering the global power generation industry, fossil fuel power plants still dominates where LNG presents one of the major clean fuel source. Although Taiwan remains as one of the main importers of LNG in the world, the cold energy was not utilized effectively which only accounts for 8% of total. Especially, the hot and humid local climates caused the Gas turbines to work under low efficiency which presents significant room for improvement when inlet cooling technology was imposed. In this research, the inlet cooling process using mechanical chillers, absorption chillers, and LNG cold reclaim technology were simulated using the Thermoflex software in a tpical combined cycle environment. The waste heat from the power plant was further utilized for Sea water desalination purposes under MED process. Simulation result indicated that , in using 2% of the waste heat from the plant, and produce 60 tons per hour of fresh water , at the cost of power output reduction of 1 %. Further simulation result also validated the economic feasibility which warranted engineering application potentials.

The objective of this programme of research is to produce a method for assessing and optimising the performance of advanced gas turbine power plants for electricity generation within the Brazilian electric sector. With the privatisation of the Brazilian electric sector, interest has been given to the thermal plants and studies have been carried out along with the use of other alternative fuels rather than fossil fuels. Biomass is a fuel of increasing interest for power generation systems since it is clean and renewable. Essentially all biomass power plants in the Brazilian market today operate on a steam Rankine cycle, which has a poor efficiency. The Brazilian electricity market has paid attention on Biomass integrated gasification gas turbine (BIG/GT) combined cycle plants where solid biomass is gasified. A simple chemical model for representing the gasifier in the power plant is presented and optimisation of the gasification process has been applied. The method for assessing the performance of power plants takes into account not only energy, but it applies the exergy method, which uses the second law of thermodynamics and works out the destruction of energy inside plant components and energy losses rejected to atmosphere. A thermoeconomic model for assessing the power plant has also been described. The optimisation of the assessment method of power plants using exergy and thermoeconomics has been proposed based on genetic algorithms. This new technique has been fairly successful at solving optimisation problems and is easy to implement. The decision of applying genetic algorithms is due to the complexity of the mathematical model applied in the performance assessment of power plants. The assessment of combined cycles like gas / steam cycle, gas / air cycle, gas / steam / freon cycle, gas / air / freon cycle and chemically recuperated gas turbine have been investigated. The application of the overall assessment method helps to understand different and very expensive choices of power plants before making final decisions.

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Simulators for power plants can be used for many different purposes, like training for operators or for adjusting control systems, where the main objective is to perform a realistic behaviour for different operating conditions of the power plant. Due to an increased amount of variable energy sources in the power system, the role of the operators has become more important. It can therefore be very valuable for the operators to try different operating conditions like island operation. The aim of this thesis is to model the power system of a general combined-cycle power plant simulator. The model should contain certain components and have a realistic behaviour but on the same time be simple enough to perform simulations in real time. The main requirements are to simulate cold start, normal operation, trip of generator, a controlled change-over to island operation and then resynchronisation. The modelling and simulations are executed in the modelling software Dymola, version 6.1. The interface for the simulator is built in the program LabView, but that is beyond the scope of this thesis. The results show a reasonable performance of the power system with most of the objectives fulfilled. The simulator is able to perform a start-up, normal load changes, trip of a generator, change-over to island operation as well as resynchronisation of the power plant to the external power grid. However, the results from the changing-over to island operation, as well as large load losses during island operation, show an unreasonable behaviour of the system regarding the voltage magnitude at that point. This is probably due to limitations in calculation capacity of Dymola, and the problem has been left to further improvements due to lack of time. There has also been a problem during the development of a variable speed regulated induction motor and it has not been possible to make it work due to lack of enough knowledge about how Dymola is performing the calculations. Also this problem has been left to further improvements due to lack of time.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 102 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 80-81).

This work has examined the thermochemical conversion of sugar cane processing wastes (bagasse and cane harvesting trash) for use in the design of pressurised entrained flow gasification power cycles (~20 Barg, 600-900oC). The two key parameters of interest were the residual char yield from initial pyrolysis and the heterogeneous reactivity of the char with respect to carbon dioxide. Char yield and gasification rates were measured by a conventional wire mesh reactor and thermogravimetric (TGA) technique, an in-situ sample charring TGA technique and with an entrained flow reactor specifically designed for this work. The new experimental reactor concept is one of the major contributions of the work. Chars from the entrained flow experiments were characterised by optical microscope, SEM/EDS, TEM/EDS and XPS techniques, to help elucidate the processes occurring during pyrolysis and gasification. The key findings and conclusions of the work were as follows: 1. Initial (pyrolysis) char yields were consistent with the data reported in literature for similar materials. Char yields varied with reaction conditions, from 6 to 49 wt% daf for cane trash and 4 to 40 wt% daf for bagasse. Ash content also had a significant effect on char yield. The char yield for both cane trash and bagasse increased in proportion to the logarithm of system pressure. 2. A relatively simple empirical model for char yield under pressurised entrained flow conditions was formulated. This could predict char yields for both the experimental data in this work and those reported in literature for similar biomass materials. While temperature, pressure and ash content were all significant parameters in the model, the primary fitting parameter was a measure of the contribution of secondary char forming reactions and ongoing pyrolysis to char yield. The identification of this parameter is one of the contributions of this work. 3. The measured initial rate of char gasification by carbon dioxide was 0.06 to 1.2 mg per gram of initial char, over the temperature range 750 to 900oC. The rate of gasification was so low as to not contribute significantly to overall fuel conversion in the reaction residence times iv expected of a commercial gasifier. In essence almost all of the experimentally measured fuel conversion could be attributed to pyrolysis, which resulted in 85-95% fuel conversion. 4. Both the raw materials and the residual chars had low surface areas and negligible microporosity. The majority of the measured surface area may have been associated with the ash component rather than the carbonaceous component, which supported the finding of low reactivity. 5. The silica component of the chars exhibited crystalline silicate formation by migration of metal species over time periods of minutes. These silicates displayed signs of sintering, but otherwise remained physically intact; leaving a characteristic skeleton that corresponded to the original structure in the raw materials. 6. The gasification rate showed a time dependent decrease in the entrained flow experiments. This was attributed to coke formation on the char surface, followed by carbon trapping in the ash component at high levels of conversion. Both findings are significant contributions from this work, because they highlight key mechanisms that hinder fuel conversion in the proposed gasification concept. The broad coverage achieved in this work has provided an overall picture of how fuel conversion progresses during the pressurised entrained flow gasification of sugar cane wastes. It is recommended that many of the aspects highlighted in this work be examined further, to confirm the findings and to investigate the means to avoid the factors identified in this work as hindering fuel conversion.

The shift towards renewable energy has steered the focus of power plant operation towards flexibility and fast response which are more attainable through the use of combined-cycle power plants. These aspects are required to account for the fluctuation of the supply as well as the demand of power that is associated with renewable energy. Combined-cycle power plants consist of a gas turbine as the topping cycle, forming the core of the plant, and a Rankine cycle with a steam turbine as the bottoming cycle. A component called the Heat Recovery Steam Generator (HRSG) forms a connection point between the two cycles. It uses the heat released from the gas turbine to produce high pressure and temperature steam to be sent to the steam turbine. The objective of this project is to develop a model of a combined-cycle power plant in Flownex which can be solved in off-design conditions in order to compare it to plant data. The verification of this model will show that Flownex can be used to effectively and efficiently model a combined-cycle power plant. The process of development of the final Flownex model was achieved using various additional software. Initially, an analytical model was developed in Mathcad (software used for engineering calculations). This software provides a tool for understanding knowns, unknowns and what is being calculated in the system. Manual calculations of the Heat Recovery Steam Generator (HRSG) were done using heat balance equations. A temperature profile of the gas and water/steam in the HRSG was developed so that the duties of each component (economiser, evaporator, superheater) could be calculated. The overall conductance (UA) of each component was calculated in the design mode for the system to be evaluated in off-design mode. The development of an analytical model provided detailed understanding of the process of mathematical modelling used in commercial tools. Thereafter, a model was built in Virtual Plant, a thermodynamic modelling software for assessing plant performance. Virtual Plant uses plant design information and first engineering principles to predict plant performance. Finally, the Flownex model was designed. Flownex uses endpoint values (initial pressure and temperature and outgoing mass flow) and the UA of each component to calculate the characteristics of the flow at each intermediate point. For the single-, double-, and triple-pressure combined-cycle power plant systems, the analytical, Virtual Plant and Flownex models were compared. The results of all the models agreed closely with one another. The triple-pressure design and off-design Virtual Plant and Flownex models were also compared to plant data and it was concluded that Flownex was successful in modelling the design and off-design conditions of a combined-cycle power plant.

A combined cycle is one of the thermal cycles used in thermal power plants. It consists of a combination of a gas and a steam turbine, where the waste heat from the gas turbine is used for steam generation in the heat recovery steam generator. The aim of the diploma thesis was the conceptual design of a combined cycle electricity source and the balance calculation of the cycle. The calculation is based on the thermodynamic properties of the substances and the basic knowledge of the Brayton and Rankin-Clausius cycle. The result is the amount and parameters of air, flue gases, and steam/water in individual places and the technological scheme of the source, in which these parameters are listed.