Combined Gas-steam Power Plant Research Articles

Energy, environmental and economic investigations of cruise ships powered by alternative fuels

In recent years, methanol, ammonia and methane–hydrogen blends are currently receiving most of interest as green fuels enabling energy transition in the maritime sector. In this work, the energy, environmental and economic performances offered by these alternative fuels applied to modern large-size cruise ships are investigated. Overall, 5 different routes, three different operating conditions (maneuvering, port and navigation) and summer–winter seasons have been accounted for. Due to the enhanced fuel flexibility of gas turbines, attention is here focused on power configurations integrating combined gas electric and steam plants with reciprocating engines. First, a cogeneration efficiency optimization study has been carried out considering variable ship operating conditions. Interestingly, combined gas steam power plants resulted to cover up to 68% of the overall thermal power request and to provide energy savings when electrical power demand exceeds 15 MW during navigation and maneuvering. Methane–hydrogen blends enabled the highest cogeneration efficiencies (i.e. ≈82%). Successively, environmental impact of power plants is assessed by means of the Energy Efficiency Design Index and Carbon Intensity Indicator, whose attained values have been shown to comply with regulation limits up to 2025 and 2050, respectively, under ammonia and methane–hydrogen feeding conditions. On the contrary, methanol appears a valuable option only for a short-term energy transition perspective, since compliance with regulations lapses before 2028. Finally, investments and operational costs for power plants have been computed to assess their economic viability. In the current scenario, comparable costs result for ammonia and methanol fueled cruise ships, while 40–60 M€increase in operational expenditure is achieved at 25-th year by methane–hydrogen blends due to the high price still affecting green hydrogen.

Comparative analysis and optimization of thermodynamic behavior of combined gas-steam power plant using grey-taguchi and artificial neural network

In the published studies, to the best of the authors’ understanding, the grey Taguchi-based statistical technique has not been applied for the optimization of combined gas-steam power plants. In view of this, seven essential input parameters namely compressor inlet air temperature, pressure ratio, fuel temperature, volumetric flow rate of fuel, gas turbine maximum temperature, compressor efficiency, and turbine efficiency are chosen with the aim of determining the optimal combination of design variables that maximize the net power generation, thermal efficiency, exergetic effciency, and minimize the specific fuel consumption. Also, the impact weight of each parameter on output indicators has been evaluated. While the Taguchi approach helps to create an orthogonal array of L27 (3^7), the ANOVA method determines the contribution of each input argument on the objective function. Unlike the Taguchi and ANOVA optimization methodology, the grey relational analysis is performed to transform the multi-objective function into a single objective by way of estimating its grey relational grade. The most favorable combination of input parameters is determined as A1B1C1D1E3F3G3 and under this state, the optimum values of power generation, thermal efficiency, exergetic efficiency, and specific fuel consumption are found to be 259911 kW, 64.9 %, 66.27 %, and 0.1839 kg/kWh respectively. Moreover, the contribution ratio on the output characteristic of the combined cycle is found to be maximum for turbine efficiency (42.41 %) and minimum for fuel temperature (0.59 %). The effectiveness of the grey-Taguchi method is acknowledged and validated using an artificial neural network technique in MATLAB.

Naftna industrija i klimatske promene

Even though the problem of climate changes has been known for many years, many people still identify weather conditions with climate, without considering the length of their duration. The catastrophic predictions regarding the warming of our planet due to irresponsible human behavior can often be found in media. At the other side, geologists are aware that during the geological history of our planet there were much warmer periods than today, and that these intervals did not inevitably result in the mass extinction of the living world, but in some cases even favored the maximum development of some species and the formation of new one. The oil companies which are marked as the major emitters of greenhouse gases as the most important cause of global warming struggle with this problem with different strategies. Generally, these strategies can be reduced to the two most important ones - ignoring the problem such as US and Arab companies and taking a proactive approach in European one. In Serbia, the only oil company, NIS Gazpromneft, has a proactive approach like other companies in Europe and region. The company has transformed to Energy Company that adopted its business strategy to sustainable development by reconstructing of Pancevo Refinery and starting two energy projects - the construction of the combined gas-steam power plant Pancevo and the Plandiste wind farm.

Thermo-economic Impact from Using Exhaust Gases Heat Lost for Power Generation

The heat lost from gas turbine power plants with exhaust gases represents the most important source for lowering its thermal efficiency. Also, the gas turbine thermal efficiency affected significantly with the ambient surrounding temperature. Al-Najybia gas-turbine power plant in Basrah, Iraq is choosing as a case study. The power plant consists of four units with a capacity of 125 MW for each unit. In the present study, all the calculations are performed for one unit only. Firstly the thermal impact is studied in terms of energy analysis for Al-Najybia gas turbine power plant (GTPP) for different ambient temperature for twelve months. Also, the economic loss a companied the heat lost with exhaust gases for different ambient temperature are estimated. Secondly, the thermo-economic improvement from coupling the GTPP with a heat recovery system is studied. For gas-steam combined cycle, the performance and economic analysis are performed. The results show that, the output power and thermal efficiency are decreased by 0.97 MW and 0.0726% respectively for each unit temperature rise of the ambient temperature. For the combined gas-steam power plant the percentage increasing of the thermal efficiency is approximately 46.4%. The results indicate the combined cycle power plant (CCPP) is very important to increase electrical capacity. From the economic analysis, the economic gain due to using HRB is 75757 $ per month

Analysis of combined cycle efficiency by simulation and optimization

Natural gas has been regarded as the cleanest fuel when compared to the other fossil fuels because of its low emission of greenhouse gases and no particulate matter after combustion. Around 22% of the world’s power production is based on natural gas. Combined gas-steam power plants operating with natural gas are preferred in recent years due to their high efficiency and less emission. To meet the world’s increasing energy demand, natural gas will continue to be used in the future in increasing amounts. For this reason, it is very important to design and operate such systems in optimal conditions. Energy conversion systems can be analyzed in terms of energetic, exergetic, economic, and environmental aspects for a good management. When the overall efficiency is increased, it can be said that these four aspects will also improve. In the present study, the modeling, simulation and optimization studies on the combined gas-steam power plants are performed. The most important parameters which influence the efficiency of such plants are determined. The simulation results indicate that the crucial unit is the combustion chamber. The optimization results show that the most effective parameters in the power production are air/fuel ratio, gas/steam ratio and the pressure ratio for the compressor and, thus, the gas turbine. The thermal efficiency of the plant increases by 22.55% and the exergy destroyed decreases by 22.65% using optimal design variables determined by the optimization algorithm in which the objective function is the thermal efficiency. The study demonstrates that the modeling, simulation and optimization can be used for the optimal design of the plants before invested, for operating the present plants at optimal conditions and for analyzing the systems. The minimum detrimental effect on the environment can be provided by optimal design and operation under optimal conditions. The originality of the study is to use an objective function by defining a new efficiency term for the maximum power production with the minimum exergy destruction which results 23.49% increase in the thermal efficiency and, in the meantime, 23.61% decrease in the exergy destruction. This new efficiency term can be used as an objective function in the solution of the optimization problems related with the efficiency of power generating in order to achieve better results.

Application of an amine-based CO2 capture system in retrofitting combined gas-steam power plants

Natural gas combined cycles (NGCCs) represent the main power generation technology in Italy, with a share of more than 40% of global thermoelectric power production. Due to their high operational flexibility, it is likely that NGCCs will continue to play a very important role in maintaining the reliability of supply in a power generation infrastructure characterized by the increasing spread of renewable energies. In this context, the integration of carbon capture technologies is regarded as an essential step to cope with the long-term climate protection target set by the European Union.This study investigates the retrofitting of three Italian NGCCs with a chemical absorption unit, capturing 90% of the CO2 from the exhaust flue gases. Two main options to meet the heat requirement for solvent regeneration are explored. The first provides for a medium-low pressure steam extraction, representing the main reason for power plant capacity derating. In the second option, steam extraction is partially replaced by external steam production from an auxiliary combined heat and power (CHP) unit that is designed to compensate for the additional power requirement of the CO2 separation and compression system equipment. Depending on the size and complexity of the NGCC, several types of auxiliary system are envisaged, basically differing in terms of the cogeneration technology and degree of integration inside the power block.Simulation results highlighted that the integration of an auxiliary cogeneration unit, besides eliminating power plant derating, has the potential to improve the energy and economic performances of the retrofitted plants to a certain extent.

Liquefied natural gas submerged combustion vaporization facilities: process integration with power conversion units

Liquefied natural gas (LNG) vaporization facilities offer an excellent opportunity of primary energy saving by means of integration with power conversion units that is still weakly exploited in actual installations. This work focuses on the evaluation of primary energy saving achievable by the integration of an LNG vaporization facility with a gas turbine and with a cogenerative combined gas-steam power plant. The fuel energy saving ratio is used as the main performance parameter to evaluate the primary energy saving derived by system integration, with respect to conventional submerged combustion vaporization. Twelve possible configurations are analyzed with steady-state calculations. Results show that a primary energy saving greater than 15% with peak values up to 27%, corresponding to 2.98 TJ/year, is achievable. The paper shows that the fuel energy saving ratio can be used as a synthetic and effective parameter to estimate the energy-saving potential of different plant configurations. Copyright © 2011 John Wiley & Sons, Ltd.

Exergetic optimization of single level combined gas–steam power plants considering different objective functions

Combined cycle power plants have been studied in this paper with the aim of optimizing the heat recovery steam generator using a first and second law approach. To this end, a mathematical model has been developed for determining the optimal steam pressure in a one pressure level heat recovery steam generator, considering that the gas turbine is known. Different objective functions have been analysed in this study, some of which refer only to the exergy balance of the heat recovery steam generator while others involve the whole bottoming cycle. Some constraints for the operating parameters of the power plant have also been taken into account, regarding for instance the steam quality at the turbine outlet and the steam turbine blade height. Some numerical results have been reported in the paper, comparing the different objective functions for heat recovery steam generators coupled with several gas turbines; the developed parametric analysis has been performed in order to evaluate the influence of some parameters on both the heat recovery steam generator and the whole bottoming cycle.

A unified approach to assess performance of different techniques for recovering exhaust heat from gas turbines

Exhaust heat from gas turbines can be recovered externally or internally to the cycle itself. Of the technology options for external recovery, the combined gas–steam power plant is by far the most effective and commonly used worldwide. For internal recovery conventional solutions are based on thermodynamic regeneration and steam injection, while innovative solutions rely on humid air regeneration and steam reforming of fuel. In this paper a unified approach for analysing different exhaust heat recovery techniques is proposed. It has been possible to define a characteristic internal heat recovery plane, based on a few meaningful parameters and to identify an innovative scheme for repowering existing combined cycles. The characteristic plane indicates directly the performance obtainable with the different recovery techniques, showing that performances close to combined cycle plants (external recovery) can only be achieved with combined recovery techniques (humid air regeneration, steam reforming of fuel). The innovative repowering scheme, which requires the addition of a gas turbine and one-pressure level HRSG to an existing combined gas–steam power plant, significantly increases power output with fairly high marginal efficiency.

97/01870 Modeling and simulation of energy conversion in combined gas-steam power plant integrated with coal gasification

97/01870 Modeling and simulation of energy conversion in combined gas-steam power plant integrated with coal gasification

97/01560 Modeling and simulation of energy conversion in combined gas-steam power plant integrated with coal gasification

The generation of electric power through the conventional conversion systems may no longer be sufficient to keep pace with the increasing electricity usage and demands. Therefore, an enhancement to these systems can be made by incorporating a topping unit to the existing power plants (thermal, hydroelectric), a direct energy conversion system. Among such is the Magnetohydrodynamics (MHD) system. In an MHD conversion system, electricity is generated when heat energy is converted into electrical energy without the use of mechanical rotating parts. Additionally, the heat energy (ionised gas) required inside the MHD system usually comes from the combustion of fossil fuels. However, this system is still under development in developing countries like South Africa. The current study aims to investigate through simulations and theoretical modelling two existing Open-Cycle Gas Turbines (OCGT) in South Africa (Ankerlig and Gourikwa), which can be converted into Combined-Cycle MHD Gas-Steam Turbines (CCMGST). The processes involved by incorporating the MHD system with these conventional turbines have been further discussed. With setting up a CCMGST in South Africa, the obtained modelling results project an additional generation of electric power which will further improve the existing power generation.

Computer control of combined-cycle power plants: Complete automation and coordination of the plant is possible — From startup through loading, and from full load to shutdown

Complete automation and coordination of the combined gas-steam power plant is possible, from startup through loading, and from full load to shutdown. The control systems described start each piece of equipment, accelerate and synchronize the turbine generators, and direct a complete plant shutdown in the event of a normal stop mode. Software in the system controls gas-turbine blade temperature and regulates steam-throttle pressure.