Efficiency Of Thermal Power Plants Research Articles

Thermal power plant upgrade via a rotating detonation combustor and retrofitted turbine with optimized endwalls

In the past decade, pressure gain combustion research has promised over 10 percentage-points of increase in power plant thermal efficiency. Alas, to realize such potential gain, one must effectively couple the turbine with the detonation combustor, whose exhaust conditions differ substantially from current state of the art gas turbines. This paper presents a modeling approach that enables a superior thermodynamic cycle with a rotating detonation combustor and a retrofitted gas turbine by including a diffuser downstream of the combustor and by contouring the turbine endwall, while preserving the airfoil geometry. We propose a multi-step optimization strategy, parametrizing the endwall geometry with a few control points, without altering the airfoil geometry, and with the stage turbine efficiency as objective function. In a first step the turbine performance is assessed with steady inlet conditions by solving the steady three-dimensional Reynolds-Averaged Navier-Stokes equations. In a second step, the inlet conditions are unsteady, as predicted from a detonation combustor and a diffuser, and three-dimensional full unsteady simulations are performed with an unsteady Reynolds-Averaged Navier-Stokes solver. By altering the vane endwall, the steady optimization yielded an efficiency increase of 12% relative to the baseline, while the unsteady optimization resulted in 21% increase compared to the datum turbine. Finally, a full engine analysis demonstrated the superiority of pressure gain combustion which included a realistic thermodynamic cycle of the combustor, the diffuser and the optimized turbine components.

Перспективи використання композиційного рідкого палива в енергетиці

Uninterrupted supplying of the national economy with gas, oil, coal, electric and thermal energy is one of the conditions for guaranteeing its economic and political independence and national security. The enterprises of power engineering, working on traditional hydrocarbon energy resources, in particular on solid fuel (coal), annually produce tens millions tons of ash and slag waste and hundreds of millions of cubic meters of gaseous emissions. The consequences of coal using as an energy carrier are the most significant for the environment and human health (in comparison with other fuels). In the case of coal combustion, nitrogen and sulfur-containing (NOx and SOx) oxides, volatile organic compounds (ash and dust), large amounts of carbon dioxide (CO2) and carbon monoxide (CO) gases per unit of energy produced, as well as various traces of metals can be spread over large areas and have a strong influence on human health. As a promising approach to reduce the harmful impact on the environment and to increase the efficiency of thermal power plants, it is proposed to use composite liquid fuel (CLF) instead of pulverized and layerwise combustion of coal. The use of composite liquid fuels based on coal is promising for several reasons. First, as a basis, one can take coals of different grades, in particular, brown coal, the use of which as an energy raw materials is connected with certain difficulties due to their high moisture content and the tendency to spontaneous combustion, as well as coal mined by a hydraulic method, its small classes and coal sludge. Second, with the appropriate selection of components, it is possible to obtain fuel with specified properties and use it in various power units. At the same time, the use of CLF makes it possible to increase the completeness of combustion of solid fuel particles due to the effect of "microexplosion" of suspension droplets, while the maximal combustion temperature decreases here, and, accordingly, the emissions of soot, benzo(a)pyrene, and nitrogen oxides are reduced. The transition of coal-fired power plants from traditional solid fuel (coal) to composite liquid fuels will solve several global problems. The first is the utilization of a wide class of waste from coal and oil refining. This will enable one not only to utilize the already accumulated waste, but also to prevent the accumulation of waste generated again. The second is connected with the decrease in the concentration of anthropogenic emissions from coal energy enterprises (SOx by 40%, NOx by 20%), which will lead to the decrease in negative impact on the environment. The third is the rational use of natural resources. This can lead to saving the fuel costs alone by hundreds of millions of UAH per year.

Development of a multi-generating complex with combined fuel in the production of hydrogen and oxygen

The article presents the research result on increasing the energy efficiency of thermal power plants (TPP). The centralized production of hydrogen at thermal power plants by multigeneration is proposed. A multigeneration complex was developed with additional production of hydrogen and oxygen. An exergy and economic analysis was carried out for TPPs with an electrical capacity of 230 MW and a thermal capacity of 394 Gcal/h. The comparison of the TPP in the current mode and in the multigeneration mode at its transfer to the nominal mode with the aim of additional production of hydrogen and oxygen was performed. The efficiency of the plant transition to the multi-generation mode with both economic analysis and exergy analysis has been proved.

What Does Cost Structure Have to Say about Thermal Plant Energy Efficiency? The Case from Angola

This paper analyzes the efficiency of thermal power plants in Angola by means of a two-stage Data Envelopment Analysis (DEA) approach. In the first stage, a novel super-efficiency DEA model for undesirable outputs (CO2 emission levels and discharge of polluted water) is initially used to measure their efficiency levels. Then, in the second stage, relevant cost structure variables frequently used to describe a productive technology are employed as analytical thresholds for assessing energy production performance either in terms of capital or labor-intensity levels. Precisely, bootstrapped regression trees are used to discriminate super-efficiency scores yielding an energy production performance predictive model based on the technology type as proxied by its cost structure and their respective thresholds, since Angolan thermal plants are heterogeneous. Findings suggest that Angolan power plants are old and labor intensive, as some of them date back to the colonial era, and that lack of capital investment should be revised in favor of installing carbon capture devices. The approach developed here consists of a valuable approach for identifying priorities when technologically updating a heterogeneous thermal industry to face pollutant concerns.

The Vapor of Thermal Deaerators as a Factor of their Energy Efficiency

The effect of the vapor of thermal deaerators on the energy efficiency of these heat-and-mass transfer apparatus and the thermal power plant as a whole is considered. Problems of reducing the vapor flow rate and its use in design and operation of Russian thermal power plants are neglected. Unjustified fuel losses in thermal deaerators of poor design and the lack of control over the vapor and its recovery are exemplified. The theoretical vapor flow rates necessary for different flow patterns of deaerated water and desorbing agent in deaerators are determined. A significant advantage in the energy efficiency of the countercurrent design over the once-through design is demonstrated. It is shown that the standardized specific vapor flow rates for thermal deaerators of different types are justified inadequately. The possibility of effective deaeration of water at a specific vapor flow rate that is substantially lower than the standard one and very close to the theoretically necessary value is proved based on experimental data. It is demonstrated that there is a wide margin to improve the energy efficiency of thermal power plants by rationally using the vapor heat of thermal deaerators. A necessary condition for increasing the energy efficiency of thermal power plants is shown to be the recovery of the vapor heat and mass of thermal deaerators. To this end, the vapor coolers should be made of corrosion-resistant materials and the vapor condensate should be used in the water-steam cycle of the power plant. Another important way to improve the efficiency is to maintain the vapor flow rate consistent with the operating mode of the deaerator, which can most effectively be done by monitoring the residual content of corrosive gases in the deaerated water. A schematic of a deaeration plant with the vapor flow rate controlled by monitoring the residual oxygen content in the deaerated water is proposed. The vapor flow rate in such a plant is kept necessary and sufficient to maintain the rated desorption efficiency of dissolved oxygen in all thermohydraulic deaeration modes, thus preventing the operation of the deaerators at insufficient or excessive vapor flow rate.

Techno-economic evaluation of the novel hot air recirculation process for exhaust heat recovery from a 600 MW hard-coal-fired boiler

To increase the efficiency of thermal power plants, we have recently proposed and analyzed a novel exhaust heat recovery process called hot air recirculation (HAR), applied to a brown-coal-fired power unit as a test case. However, the performance of HAR, applied to a hard coal-fired power unit, is not clearly understood yet. In this study, the HAR process was redesigned to match the actual supply air and flue gas layout of a hard-coal-fired boiler. The thermo- and techno-economic performances of HAR, as well as the conventional bypass flue (CBF) process, applied to a 600 MW hard-coal-fired power unit, were analyzed in detail. The results indicate that, when the boiler exhaust heat is recovered from 122 to 90 °C, the net coal savings, initial capital cost, and payoff period of HAR are 3.49 g/(kW·h), $1.473 million, and 1.34 years, respectively, whereas those of CBF are 2.98 g/(kW·h), $2.528 million, and 3.04 years, respectively. Therefore, it is established that HAR can benefit a hard-coal-fired power plant with a greater saving on coal consumption and a more economical project investment, in addition to providing a safe and reliable operation, as compared to similar processes.

Entropy generation versus transition time of heat exchanger during transient processes

The flexibility of thermal power plants plays a critical role to accommodate high penetration of fluctuant renewable energy. Heat exchanger is the key device restricting the flexibility and energy efficiency of thermal power plants owing to its large thermal inertia. Therefore, evaluation of the additional entropy generation and transition time for the heat exchanger during transient processes is important, which are quantitative measures of the efficiency and flexibility. Consequently, dynamic models of a heat exchanger are developed. The dynamic behaviors of the heat exchanger are analyzed using numerical simulation and entropy generation analyses. The relationship between additional entropy generation and transition time is determined. Results show that: when flow rate decreases and temperature increases, this relationship is synergetic for hot fluid, metal wall and heat exchanger. The opposite correlation occurs when flow rate increases and temperature decreases. However, the cold fluid has the contrary tendency. The augmentation in heat transfer resistance reduces the additional entropy generation and transition time, whereas the effect of increasing the range of the boundary disturbances, such as temperature and flow rate, is on the contrary. For a heat exchanger, the additional entropy generation versus the transition time can be described by an exponential function.

Analysis on Peak-shaving Energy Efficiency of Thermal Power Plant with High Temperature Thermal Energy Storage

Integration of energy storage infrastructures into electrical grids represents a crucial milestone in the transition towards energy systems with high penetration of renewables. However, the high cost of the currently available technologies is a significant barrier for their implementation on the industrial scale. High temperature thermal energy storage systems, in combination with bottom steam cycles, are being investigated as potential cost effective alternatives to traditional large-scale energy storage technologies. In this study, by adding a high temperature heat storage device in the cold (hot) section of the reheating pipeline and taking the 300MW extraction steam turbine as the research object, it is concluded that the introduction of the high temperature heat storage device can improve the consumption of wind power and greatly reduce the power supply of the coal-fired unit. The coal consumption rate is analyzed. The ideas and methods for solving the energy consumption of the renewable energy and reducing the peak energy consumption are provided.

Improving Thermal Power Plant Efficiency

Energy is the most important requirement for the growth and development of a nation since it is the basic necessity for every sector. The most common form of energy used is electricity. Electricity is the form of energy that is used both commercially and non-commercially. Thus, generation of electricity is the most significant requirement. Thermal electric power generation is one of the major methods for generation of electricity. But generation of electricity is it enough. It has to be done in the most effective and efficient manner. Owing to acute importance of electricity, it is important that it is done in the most efficient manner so that losses are minimized, outputs are maximized, optimum utilization of resources is done and reduction in the overall cost of the power plant can be achieved. Such outputs are even more important in the present era where sustainable development has become the most important requirement. The present research will analyze the factors affecting efficiency of a power plant. The study will further analyze the effect of operational practices & choice of fuel on efficiency of thermal power plant and the technologies available for improving the thermal power plant efficiency. The research will analyze the ways to optimize the thermal power plant through review based and theoretical analysis. The present research will be a review based work wherein an in depth analyses of the existing literature will be done. The conceptual model thus formed from the review will then be verified through qualitative analysis using thematic analysis method. The respondents (N=8) will be acclaimed professors and research associates in the field of thermal energy. Based on the findings from the review and qualitative analysis, conclusion will be drawn and discussion will be presented wherein all the research questions will be answered. Finally, the future prospective based on the present research will be presented.

Аналіз тенденцій та напрямів розвитку теплової електроенергетики в Україні

The current state of electricity generation systems in Ukraine is reviewed and analyzed. The dynamics of volumes and structure of electricity production and the specific fuel consumption for its supply are presented. Technologies and measures to improve the efficiency of thermal power plants (TPP) are presented with regard for current conditions of rapid development of renewable energy. The possible transition of country's power industry from fossil fuels to renewable sources (solar and wind energy) is considered in details. Such a transition is accompanied by the integration of a significant part of the variable power generation from renewable energy sources with unguaranteed generation of electricity (solar and wind power plants) into the electric grid. The proposed scenario of transition to 100% renewable electricity generation is divided to four stages with the development and modernization of TPP based on fossil fuels is analyzed as a necessity for the implementation of this scenario. It is substantiated that the modern electric system should combine all types of generation and any types of consumers responsible for situational demand for their services, change in real time the parameters and topology of the electric grid according to the current operating conditions. The flexibility and reliability of the Integrated Power System of Ukraine during the transformational transition can be provided by highly maneuverable combined-cycle power plants and fast-start power plants using fossil fuels.

Measuring the Ecological Efficiency of Thermal Power Plants: Evidence from Pakistan

This paper assesses the environmental and economic efficiency of thermal plants operating on fossil fuels in Pakistan using methods based on data envelopment analysis. Using the material balance principle, we find that cost- and carbon-efficient points can only be obtained simultaneously by switching to gas. However, under an assumption of variable returns to scale, these points can still be obtained without this conversion through the application of best practices. Furthermore, about 26% of costs and about 34% of carbon emissions can be reduced without a switch to gas, but instead by using technically efficient inputs; this approach can also lead to a significant reduction in electricity prices and considerable environmental benefits. Power plants operating on residual fuel oil are significantly more technically efficient than plants operating on gas. Nonetheless, both types of plants have an equal share in forming the metafrontier as exhibited by the meta-technology ratio. There is a definite need to make plants more efficient by using the best possible combination of inputs and overhauling. Bootstrap results also suggest that further improvement in efficiency is possible.

Novel post combustion CO2 capture in the coal-fired power plant employing a transcritical CO2 power generation and low temperature steam upgraded by an absorption heat transformer

This paper deals with a double effect heat transformer-aided carbon dioxide capture unit with transcritical carbon dioxide power generation for a coal-fired steam power plant. In the proposed system a double absorption heat transformer is used to upgrade low energy level steam into high-level and drive carbon dioxide capture unit. Also, a transcritical carbon dioxide power generation that is utilized captured carbon dioxide to generate power and compensate a portion of the required electrical energy of the carbon dioxide capture unit. This system avoids extracting high-grade temperature steam extracted from high-pressure stage of steam turbine and hence overall thermal efficiency of power plant increases compared to the reference systems. Comprehensive thermodynamic and economic evaluations are conducted to reveal the feasibility of the presented system. The results show that the evaporator temperature has the highest effect on net power output. An increase of 10 K in the evaporator temperature from 80 °C to 90 °C, leads to a reduction of 4.9% in generated power. However, a 50% increase in carbon dioxide capture rate from 40% to 90%, leads to a rise of 23.4% in the exergy destruction rate. Moreover, the payback period is approximately 4 years and 6 months.

Improving the efficiency and reliability of electric power generation at incineration plants

The article deals with the problem of waste disposal and, accordingly, landfills in the Moscow Region, which have now become the number 1 problem for the environment in Moscow and the Moscow Region. To solve this problem, incineration plants (IP) will be established in the near future. 4 plants will be located in the Moscow Region that will be able to eliminate 2800 thousand tons of waste per year. Burning of waste results in formation of slag making 25% of its volume, which has a very high temperature (1300.1500°C). An arrangement is considered, in which slag is sent to a water bath and heats the water to 50.90°C. This temperature is sufficient to evaporate any low-temperature substance (freons, limiting hydrocarbons, etc.), whereupon the steam of the low-temperature working medium is sent to a turbine, which produces additional electricity. The creation of a low-temperature thermal power plant (TPP) increases the reliability of electricity generation at the IP. The operation of low-temperature TPPs due to the heat of slag is very efficient, their efficiency factor being as high as 40.60%. In addition to the efficiency of TPPs, capital costs for the creation of additional devices at the IP are of great importance. Thermal power plants operating on slag are just such additional devices, so it is necessary to minimize the capital costs of their creation. In addition to equipment for the operation of TPPs, it is necessary to have a working medium in an amount determined by calculations. From the wide variety of working media, which are considered in the article, it is necessary to choose the substance with the lowest cost.

Methods of Improving the Efficiency of Thermal Power Plants

As one of the most important power sources in modern society, electricity takes up a large proportion of modern energy consumption. Among all those methods of power generation, fossil-fuel thermal power generation is one of the earliest ways of large-scale electricity production. Its popularity in the modern society comes from its stability and controllability. Given the wide applications of electricity around the world, improving the efficiency of thermal power plants would be an effective way to reduce the total energy consumption and protect the environment. The paper discusses the efficiency of energy transition and its determinant during each stage of power generations along with proposals to improve the efficiency of thermal power generation.

Economic analysis of thermal power units operating under unconventional conditions

In the case of deep peak shaving of thermal power units, it can absorb more photovoltaics and wind power, and also reduce the efficiency of thermal power plants and increase the environmental cost of society. This paper analyses the thermal power units under unconventional conditions from several influencing factors. The economics of operation, and innovative consideration of the current on-grid price and the latest government peaking subsidy factor. Firstly, according to the operating state and energy consumption characteristics of thermal power units, the peaking process is divided into conventional peaking, no oil depth adjustment and oil injection depth peaking, and the main factors affecting the deep peaking capacity of thermal power plants are analysed. The peaking energy cost model of thermal power units at different stages, and the actual power plant as the research object, the simulation results under different scheduling strategies are given. The results show that it is the most economical to increase the peaking depth of the unit to 54% of the rated capacity. The research results will provide a reference for better consumption of new energy.

Experimental investigation of conveyor idlers operational characteristics

The efficiency of thermal power plants significantly depends on the efficiency of belt conveyor systems. Conveyor idlers, as key parts of belt conveyors, are often the main cause of bulk material transportation systems failures. Testing the operational characteristics of conveyor idlers in laboratory and exploitation conditions is a prerequisite for any progress in the field of increasing energy efficiency of conveyor systems. This paper describes an analysis and discussion of testing results for different types of conveyor idlers, in terms of their performances under the act of predefined radial load. Tests were conducted on a new conveyor idler’s testing machine developed at the University of Belgrade - Faculty of Mechanical Engineering. The presented tests are performed in order to determine the quality of carrying and return conveyor idlers. The obtained results will help in solving the key problems in the critical areas of conveyor systems and will increase their energy efficiency. Finally, the expected results can potentially reduce the financial and energy losses which conveyor idlers cause in belt conveyor systems, as well as in the whole system of thermal power plants.

Power Plant Thermal Efficiency as a Regulatory Mechanism: Implications for Emission Rates and Levels

In August 2018, the U.S. Environmental Protection Agency (EPA) proposed a new policy – the Affordable Clean Energy rule – to reduce greenhouse gas (GHG) emissions from existing coal-fired electric generating units and power plants. The new rule establishes emissions guidelines, including heat-rate efficiency improvements, for states when developing plans to limit GHG emissions. Past studies have indicated that heat-rate efficiency improvements can increase electricity output, leading to a reduction in emissions rates and an increase in emissions levels – a rebound effect that can temper the emissions-reduction benefits of plant-level heat-rate efficiency. This study adds to the literature by examining data on the relationship of plant-level heat-rate efficiency on the rate and level of GHG emissions. We explored three different types of GHGs – carbon dioxide, methane, and nitrous oxide. Controlling for variation across operators, our results suggest that gains in heat-rate efficiency are associated with higher levels of all three pollutants. Specifically, we found that a ten percent increase in heat-rate efficiency led to an average seven-to-nine percent increase in the level of GHG emissions. Our analysis highlights the need to further study the full effects of heat-rate efficiency policies before such rules are enacted.

Numerical study of coal and woody biomass co-gasification in oxygen-fed gasifier

The use of biomass in the energy sector is associated with two important tasks: reducing the dependence of energy systems on expensive high-quality fuel, and increasing the environmental efficiency of thermal power plants (by processing carbon-containing waste and, in some cases, reducing harmful emissions). In addition to co-combusiton, other methods of fuels co-processing are possible, including co-gasification. The process of gasification of low-grade fuels can be unstable because of their low calorific value, often accompanied by the formation of tar products, so the addition of coal improves the efficiency of co-conversion. On the other hand, the high reactivity of biomass can contribute to the stabilization of combustion and gasification regimes of fuels with low-reactivity, such as coals with high degree of metamorphism or petcoke. In this paper, the process of pulverized fuel gasification is considered, and limitations on the efficiency associated with the melting of ash are investigated.

NATURAL TESTS OF THE EXPERIMENTAL SAMPLE OF THE THERMOELECTRIC SYSTEM, BASED ON JOINT USE OF HIGH-CURRENT THERMOELECTRIC BATTERIES AND ALL-METAL THERMAL CONDUCTORS

Objectives. The aim of the article is to develop and study a thermoelectric system based on the combined use of high-current thermoelectric batteries and heat pipelines made of high-heatconducting material (e.g. copper or aluminum), to conduct full-scale experimental studies of the experimental sample of thermal power plants.Method. The design of the device of the experimental stand of the prototype on the basis of the combined use of high-current thermoelectric batteries and heat pipelines made of high-heat-conducting material is presented. The technique of full-scale tests of the prototype on a specially created laboratory bench to confirm the adequacy of the results of thermal power plants.Result. Temperature changes in different points of thermal power plants at fixed and different supply currents, temperature changes at the end of the heat pipeline in time at different supply currents of thermal power plants are investigated. The comparison of experimental and calculated data of the prototype is carried out.Conclusion. The results of experimental studies have shown the effectiveness of the developed thermoelectric system for remote separation of the cold source and the cooling object. It is shown that it is possible to increase the efficiency of thermal power plants with the combined use of high-current batteries and heat pipelines made of high-heat-conducting material.

Experimental study of condensation heat-transfer and water-recovery process in a micro-porous ceramic membrane tube bundle

Micro-porous ceramic membrane tube is a new type of condensation material which can synchronously recover both water vapor and its accompanied latent heat from exhausted flue gas. The recovery outcome is helpful to reduce amount of make-up water and enhance boiler efficiency of thermal power plant. In this study, an experiment has been carried out to investigate condensation heat-transfer, water-recovery, and flow-resistance performance of micro-porous ceramic membrane tube bundle (CMTB), respectively. In addition, real exhausted flue gas with inlet flow rate ranging from 390 to 750 m3/h, temperature ranging from 323 K to 373 K was used as experimental feed gas. Results showed that the condensation heat-transfer process got more apparently with increasing of flue gas inlet temperature (from 335.3 K to 364.8 K). In addition, both cooling water flow rate and heat-transfer temperature difference had a remarkable influence on the water-recovery performance of the CMTB, and maximal water-recovery mass flow rate could reach 0.0336 × 103 kg/h. Most of all, velocity drop of flue gas was controlled within an appropriate range (from 28.94 m3/h to 178.78 m3/h). The application analysis on the CMTB gives a good perspective for designing high efficiency membrane-type condenser to recover water vapor from exhausted flue gas and make good use of its latent heat in the thermodynamic system of power plant.