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Energy and Exergy Analysis Of a 44MW Bagasse-based Cogeneration Plant in India
Abstract
In this article, energy and exergy analysis of an ongoing, 44-MW, heat-matched, bagasse-based cogeneration plant of Ugar Sugar Works Ltd (USWL), located in Belgaum, India is presented. In the analysis, exergy methods with more conventional energy analysis are employed to assess the thermodynamic efficiencies and losses. The performance of the plant was estimated, and a detailed break up of energy and exergy losses for the considered plant has been presented. The fuel energy savings ratio of the cogeneration plant is estimated in comparison with separate generation plants. The plant performs with energy and exergetic efficiency of 65% and 25%, respectively. Energy losses mainly occurred in the boiler exhaust and condenser, where 35 MW and 27 MW is lost to environment, respectively. The percentage ratio of the exergy destruction to total exergy destruction was found to be maximum in the boiler system (71%) of fuel exergy input or 45% of the physical exergy input. The total exergy destruction in the plant's components is 58% of physical energy input. The plant's fuel energy savings ratio is 8.2%. Because of its inherent combustion irresistibility, the boiler is the major contributor to the plant's overall inefficiency. The inefficiencies in bagasse-fired boilers can be reduced to some extent by increasing the pre-heated, excess air supply and generating steam at possible high pressure and temperature. In terms of technology development, only cogeneration plants with exergetic efficiency close to that of overall efficiency of the conventional power plant be suggested
... For a combined heat and power plant, the overall exergy efficiency can be written as [41][42][43]: ...
... Soltani et al. [28] investigated a biomass multi-generation energy system that produces electricity, steam, hot water, district heating and timber heating: significant increases in both the energy and exergy efficiencies were observed in the biomass multi-generation systems compared to conventional systems. A fuel energy savings ratio of 8.2% was reported by Kamate and Gangavati [43] for a biomass cogeneration plant over the generation of heat and power in two separate plants. To model and evaluate a (sawdust) biomass-fired multi-generation energy system using energy and exergy analysis. ...
The growing demand for energy is particularly important to engineers with respect to how the energy produced by heat and power plants can be used efficiently. Formerly, performance evaluation of thermal power plants was done through energy analysis. However, the energy method does not account for irreversibilities within the system. An effective method to measure and improve efficiency of thermal power plant is exergy analysis. Exergy analysis is used to evaluate the performance of a system and its main advantage is enhancement of the energy conversion process. It helps identify the main points of exergy destruction, the quantity and causes of this destruction, as well as show which areas in the system and components have potential for improvements. The current study is a comprehensive review of exergy analyses applied in the solid fuels heat and power sector, which includes coal, biomass and a combination of these feedstocks as fuels. The methods for the evaluation of the exergy efficiency and the exergy destruction are surveyed in each part of the plant. The current review is expected to advance understanding of exergy analysis and its usefulness in the energy and power sectors: it will assist in the performance assessment, analysis, optimization and cost effectiveness of the design of heat and power plant systems in these sectors.
... Also, a good attempt has been made by researchers in energy and exergy analysis of the cogeneration system. Kamate and Gangavati [61]. presented energy and exergy analysis of a 44-MW bagasse based cogeneration plant of a sugar mill. ...
... In an organic Rankine cycle operating on different working fluid, the exergy topological method was used to present a quantitative estimation of the exergy destroyed [31] - p  Exergy analysis of an advanced combined cogeneration plant has been done [19] - p  By using second law analysis the chemical and physical exergy and exergy destruction of the cogeneration system was calculated. [62] p p  Exergy analysis of a heat-matched bagasse-based cogeneration plant was employed to evaluate overall and component efficiencies and to identify and assess the thermodynamic losses [110] 5 kW  p  Design and exergy method optimization of a 5 kW power output polymer electrolyte fuel cell with a cogeneration application has been analyzed for maximum system efficiency and minimum entropy generation, fuel cell temperature and voltage should be as high as possible in the range of application [61] 44 MW p p  Energy and exergy analysis of a bagasse-based cogeneration plant has been analyzed to assess the thermodynamic efficiencies and losses [70] p p  In combustion gas turbine cogeneration system with reheat energetic and exergetic efficiencies have been defined [18] - p  Exergetic and engineering analyses of two cogeneration cycles, one consisting of a gas turbine and the other of a gas turbine and steam turbine have been analyzed [107] p p  A cogeneration-based district energy system was analyzed for efficiency analysis, accounting for both energy and exergy considerations. The exergy efficiencies are generally found to be more meaningful and indicative of system behaviour than the energy efficiencies [132] - p  The exergy analysis for cogeneration in cement plant was used by means of genetic algorithms to reach the maximum exergy efficiency. ...
The growing energy supply, demand has created an interest towards the plant equipment efficiency and the optimization of existing thermal power plants. Also, a thermal power plant dependency on fossil fuel makes it a little bit difficult, because of environmental impacts has been always taken into consideration. At present, most of the power plants are going to be designed by the energetic performance criterion which is based on the first law of thermodynamics. Sometimes, the system energy balance is not sufficient for the possible finding of the system imperfections. Energy losses taking place in a system can be easily determined by using exergy analysis. Hence, it is a powerful tool for the measurement of energy quality, thereby helps to make complex thermodynamic systems more efficient. Nowadays, economic optimization of plant is also a big problem for researchers because of the complex nature. At a viewpoint of this, a comprehensive literature review over the years of energy, exergy, exergoeconomic and economic (4-E) analysis and their applications in thermal power plants stimulated by coal, gas, combined cycle and cogeneration system have been done thoroughly. This paper is addressed to those researchers who are doing their research work on 4-E analysis in various thermal power plants. If anyone extracts an idea for the development of the concept of 4-E analysis using this article, we will achieve our goal. This review also indicates the scope of future research in thermal power plants.
... For that reason, the present work will include both energy and exergy analysis to make the investigation be more understandable and effectively in the cogeneration performance.By cooperating energy and exergy, analyses has been approved as the most effective methodologies to evaluate the energy systems. Kamate and Gangavati[27] undertook the analysis on 44 MW bagasse based cogeneration plant in India. They summarized equations, and the methodologies to determine the exergy flow of each component. ...
... Bagasse fuelled back pressure combined with condensing type steam turbine cogeneration plant (Configuration 2) Ugar sugar mills Ltd cogeneration plant[27] ...
... The highest percentage of electrical power worldwide is produced by using various steam turbines. Steam turbines today can be found not only in many different power plants [1][2][3][4][5] but also it can be used in ship steam propulsion systems [6][7][8], for simultaneous production of heat and electrical power [9,10], and for various other purposes. ...
In this paper, two-cylinder steam turbine, which operates in nuclear power plant is analyzed from the energy viewpoint. Along with the whole turbine, energy analysis is performed for each turbine cylinder (High Pressure Cylinder-HPC and Low Pressure Cylinder-LPC). A comparison of both cylinders shows that the dominant mechanical power producer is LPC, which a lso has much higher energy loss and much lower energy efficiency. Therefore, any potential improvement of this steam turbine should be based dominantly on th e LPC, which also has a dominant influence on energy analysis parameters of the whole observed turb ine. The whole turbine produces real (polytropic) mechanical power equal to 1247.69 MW, has energy loss equal to 352.70 MW and energy efficiency equal to 77.96%. According to obtained energy efficiency value it can be concluded that the whole analyzed stea m turbine is comparable to main marine propulsion steam turbines, while its energy efficiency is much lower in comparison to steam turbines from conventional steam power plant s which operates by using superheated steam.
... Steam operating parameters (temperature, pressure and mass flow rate) in each operating point from Fig. 1 are found in [30] and presented in Table 2 for the real (polytropic) steam expansion process of both analyzed turbines (BPT and CT). Steam specific enthalpies, specific entropies and steam quality in each operating point from Fig. 1 are also presented in Table 2 they are calculated by using NIST REFPROP 9.0 software [31]. ...
This paper presents thermodynamic (energy and exergy) analysis of backpressure (BPT) and condensing (CT) steam turbines from cogeneration system. Based on the measurement data from exploitation it is performed calculation of main operating parameters for both turbines and its comparison. Analysis shows that BPT develops significantly lower mechanical power (22821.90 kW) in comparison to CT (30893.10 kW), but also BPT has more than four times lower energy and exergy power losses when compared to CT. Due to much lower losses, BPT has significantly higher energy and exergy efficiencies (93.26% and 94.95%, respectively) in comparison to CT (82.63% and 83.87%, respectively). Energy and exergy power of a steam flow related to both observed turbines show that the BPT is the dominant heat supplier for all heat consumers inside the cogeneration system.
... To be noted that the increase in steam generation pressure and temperature causes a reduction in exergy losses, thereby leading to an increase in efficiency [71]. Another way to increase the efficiency could be by increasing the quantity of preheated excess air in the RSB fired boilers [72]. Notably, the geometry of RSB feedstock also plays a vital role in RSB gasification [73]. ...
The Indian sugar industry’s growth and residual lignocellulosic sugarcane bagasse (RSB) generation rate are complementary to each other. It is estimated that over 75–90 million tonnes of wet RSB are produced annually from 600 operational sugar mills in India. Therefore, the efficient utilization of residual bagasse needs immediate attention from sugar industries and the scientific community worldwide. Albeit recently developed technologies have shown promising prospects for the sustainable conversion of RSB into fuels and value-added chemicals, there is an apparent lack of consensus among the scientific community on technical understanding and commercial applicability of current RSB conversion technologies. This review discusses applications of RSB in Indian industries for electricity generation, concrete manufacturing from RSB ash, nanocomposite production, as well as pulp and paper, furfural, furfuryl alcohol, bioethanol, and value-added chemical production. Besides, the conversion of RSB major component lignin to fuel and high-value specialty chemicals has been discussed. Moreover, the government of India policies and subsequent revisions in 2018 to promote biomass and RSB conversion technologies has been presented. Subsequently, major challenges associated with the implementation of different conversion technologies have been explored. Overall, it is observed that there is a huge opportunity in India to utilize the RSB for value-added chemicals production, pulp, and paper production, electricity generation, and other applications. Nevertheless, the Government of India current policies directed towards promoting the RSB uses primarily for electricity production via cogenerations.
Graphical abstract
... The typical efficiency of power plants in developing countries remains around 32-35% [52]. Numerous studies have investigated both energy and exergy analyses to demonstrate complete magnitudes, location, and causes of losses in a thermal power plant [92] [93]. On top of that, significant assessment of individual component efficiency can also be observed. ...
Rapid depletion of fossil fuels due to the growing demand for energy has resulted in a worldwide concern to improve energy conversion efficiency. Yet, the energy conversion of conventional fossil fuel power generation plants remains relatively low (less than 40%) and a huge amount of energy is wasted in the form of heat, leading to global warming issues. Recycling and recuperating even a small portion of energy losses could provide a huge impact on energy saving and minimize the reliance on fossil fuels. Thermophotovoltaic system appears to be a potential candidate to capture, recover, and convert waste heat energy into useful electricity. This paper presents an overview of the recent development of thermophotovoltaic technology for waste heat recovery applications. Each component in the thermophotovoltaic system including thermophotovoltaic generator/heat source, thermal emitter, spectral filter and thermophotovoltaic cells is vital and can be engineered to achieve a better heat-to-electricity conversion efficiency. Recently, researchers have shown great interest in near-field thermophotovoltaic systems where higher power intensity can be captured by the thermophotovoltaic cell, thus improving the overall system performance. Furthermore, the potential locations for energy scavenging in thermal power plants is investigated based on the on-site temperature measurement. In Malaysia, it is estimated that around 3,831 GWh of waste heat energy could be saved in operational thermal power plants. This review will contribute to the knowledge for future development thermophotovoltaic systems in waste heat recovery applications while summarizing the potential locations for energy scavenging in thermal power plants.
... 107 Saidi et al 187 conducted a study on a 5 kW polymer electrolyte fuel cell with cogeneration application and applied exergy approach for optimization of the system. Kamate et al 188 analyzed a 44-MW bagasse-based cogeneration system of a sugar mill based on energy and exergy concepts. In this study, results showed that the boiler was the main reason for inefficiency of the plant. ...
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. Several thermal power plants in combined cycles are reviewed comprehensively in the present study. Results of the studies based on energy, exergy, and economic analyses are represented for each type of thermal power plants. Integrating thermal power plants with other cycles will enhance the energetic efficiency. Systems integrating will increase investment cost for the power plants. Exergy analysis provide useful information for enhancement of plants’ efficiency.
... Kamate and Gangavati [4] performed an energy and exergy analysis of bagasse-based cogeneration plant, located in Belgaum in India. The capacity of the plant was 44-MW. ...
The exergy analysis for different components of 45 MW cogeneration thermal power plant of Qena Paper Industry Company (QPIC) was studied. The study was carried out to analyze each component separately and to identify and quantify the exergy losses for each component in the cogeneration power plant. In addition, the effect of varying the reference ambient temperature on this analysis was investigated. The results showed that, the exergy destruction rate increases with increasing the ambient air temperature in all system components. The major contribution to exergy destruction comes from the boiler and it increases as the ambient air temperature increases. In addition , at full load operation and ambient temperature of 18 o C, 23 o C, 29 o C, 36 o C and 45 o C the percentage of the exergy destruction for boiler, deaerator and condenser are 78.9%, 79%, 80%, 80.2%, 80.5% and 3.6%, 3.5%, 3.5%, 3.4%, 3.3% and 3.1%, 2.5%, 1.87%, 1.1%, 0.6%, respectively. Keywords-steam power plant; cogeneration; ambient temperature ; exergy analysis; exergy destruction; exergy efficiency. I. INTRODUCTION Cogeneration power plant is an efficient, clean and reliable approach to generating electrical energy as well as supplying thermal energy using a single fuel. Namely, cogeneration that sometimes uses discarded heat by recycling this waste heat, achieves a dramatic improvement in the system's efficiency. Otherwise, it extracts heat at any point during the expansion in the turbine to produce thermal energy for industrial applications. The main advantages of cogeneration are, the comparatively higher efficiencies, reduce air emissions such as nitrous oxide (N 2 O), sulfur dioxide (SO 2) and carbon dioxide (CO 2) which increases the greenhouse effect associated with climate change. Nowadays, about 80% of electricity in the world is approximately produced from fossil fuels (coal, petroleum, fuel-oil, natural gas) thermal power plants, whereas 20% of the electricity is compensated from different sources such as hydraulic, nuclear, wind, solar, geothermal and biogas [1, 2]. Energy consumption is one of the most important indicator showing the development stages of countries and living standards of communities. Population increment, urbanization, industrializing , and technologic development result directly in increasing energy consumption. This rapid growing trend brings about the crucial environmental problems such as contamination and greenhouse effect. Generally, the performance of thermal power plants is evaluated through energetic performance criteria based on first law of thermodynamics, including electrical power and thermal efficiency. In recent decades , the exergetic performance based on the second law of thermodynamics has found as useful method in the design, evaluation, optimization and improvement of thermal power plants [3]. Many researchers have already done a good amount of work in the subject of exergy analysis of thermal power plants. Regulagadda et al. [3] achieved a detailed parametric study of energy and exergy analysis of a subcritical boiler-turbine generator for a 32 MW coal-fired power plant in India. Both energy and exergy formulations are developed for the system. This study was conducted for different operating conditions , including different operating pressures, temperatures and flow rates. The results showed that the maximum exergy destruction for the boiler and turbine were 86.7% and 7.6%, respectively. Kamate and Gangavati [4] performed an energy and exer-gy analysis of bagasse-based cogeneration plant, located in Belgaum in India. The capacity of the plant was 44-MW. The analysis was carried out for a wide range of steam inlet conditions selected around the sugar industry export cogeneration plant. They demonstrated that the percentage ratio of the exer
... On the second law analysis applied to bagasse boilers, several works can be found using the input/output method (Prieto and Nebra, 2004; SosaArnao et al. 2006a; Sosa Arnao and Nebra 2006b and 2007), even though the analysis through this method does not permit to see the irreversibilities that happens in each process in the bagasse boiler. On the other hand, few works in this area have been published (Lozano, 1987; Cortez and Gómes, 1998; Kamate and Gangavati, 2010), and therefore this work aims to identify the main irreversibilities, seeking to reduce them. The methodology recommended can be extended to other kinds of boilers. ...
p>The performance of sugar cane bagasse boilers is commonly analyzed through the first law of thermodynamics, using the energy balance method and the fuel lower heating value as calculation base. This work presents a first law analysis using two different methods: the input/output and the energy balance. The employment of the fuel higher and lower heating values as calculation base are presented and discussed. Moreover, a second law analysis is showed, based on two methods: input/output and exergy balance. The methods based on exergy concept permits to observe the main irreversibilities that happen during the steam production in a bagasse boiler.
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The pulp and paper industry is a power-intensive technology so great attention to reducing its own energy consumption and declining the waste of available energy should be devoted. In the current investigation, the energy-exergy approach of a pulp and paper company integrated with a chemical recovery of black liquor (BL) and soda is studied actually for one year. The chemical BL recovery system that has the primary benefits to avoid environmental pollution by burning organic waste and recycling the soda is also comprehensively investigated. Natural gas (NG) and BL are utilized in power boiler (PB) and recovery boiler (RB), respectively. Moreover, in the present implementation, the chemical reactions of NG and BL are presented. The obtained results show that the percentages of energy losses in the condenser, RB, evaporators, and PB are 49.16, 19.28, 14.22, and 3.96%, respectively. The average values of exergy destruction percentages in RB and PB around the year are 41.63 and 33.5%, respectively. The maximum system overall exergy efficiency is 32.09% at an environment temperature of 290 K, whereas the energy efficiency of the system is 53.7%.
In the present study, a thermodynamic analysis of a cogeneration system in a pulp and paper industry under different operating modes i.e., singular and hybrid with a variable ambient temperature is conducted according to actual operating data. For singular operating mode, the power boiler is only employed using natural gas while for hybrid operating mode, the power boiler with the recovery boiler is employed using natural gas and black liquor as main fuels, respectively. The results show that for hybrid operating mode in comparison with the singular one, the thermal efficiency of turbine and condenser is enhanced by 1.36 and 7.7%, respectively while it is reduced by 2.8% for the power boiler. In addition, the overall thermal efficiency under singular and hybrid operating modes is 87.4 and 53.7%, respectively. For hybrid operating mode, the exergy destruction of power boiler decreases by almost 10% compared with that for the singular operating mode. Also, at hybrid operating mode, the soda is recovered with a mass flow rate of 33 tons/hour that is required for the cooking process in the chemical pulp section and additionally the consumption of natural gas in the power boiler is reduced by 11.8%.
Abstract
The performance of sugar cane bagasse boilers is commonly analyzed through the first law of thermodynamics,using the energy balance method and the fuel lower heating value as calculation base. This work presents a first law analysis using two different methods: the input/output and the energy balance. The employment of the fuel higher and lower heating values as calculation base are presented and discussed. Moreover, a second law analysis is showed, based on two methods: input/output and exergy balance. The methods based on exergy concept permits to observe the main irreversibilities that happen during the steam production in a bagasse boiler.
Keywords: Boiler; efficiency; exergy; bagasse.
In this study, the energy and exergy analysis of Al-Hussein power plant in Jordan is presented. The primary objectives of this paper are to analyze the system components separately and to identify and quantify the sites having largest energy and exergy losses. In addition, the effect of varying the reference environment state on this analysis will also be presented. The performance of the plant was estimated by a component-wise modeling and a detailed break-up of energy and exergy losses for the considered plant has been presented. Energy losses mainly occurred in the condenser where 134 MW is lost to the environment while only 13 MW was lost from the boiler system. The percentage ratio of the exergy destruction to the total exergy destruction was found to be maximum in the boiler system (77%) followed by the turbine (13%), and then the forced draft fan condenser (9%). In addition, the calculated thermal efficiency based on the lower heating value of fuel was 26% while the exergy efficiency of the power cycle was 25%. For a moderate change in the reference environment state temperature, no drastic change was noticed in the performance of major components and the main conclusion remained the same; the boiler is the major source of irreversibilities in the power plant. Chemical reaction is the most significant source of exergy destruction in a boiler system which can be reduced by preheating the combustion air and reducing the air–fuel ratio.
C S Kudarihal, Non-member P M Menghal, Associate Member In recent years the possibility of cogeneration has a means for utilising energy efficiently, has been receiving considerable attention in India. The current problems of power in the country lend further validity to cogeneration as one option that could help to quickly fill the gap between power demand and supply. Due to depleting nature of conventional reserves the necessity of renewable source and energy conservation is very much necessary to meet energy demand. Cogeneration emerges as a promising method of energy conservation and bagasse as a renewable energy source. In this paper, an attempt has been made to study techno-economical viability, possible model of cogeneration and sizing of cogeneration plant for sugar plant.
Recent federal incentives in the U.S. concerning tax credits, fuel-use exemptions, and facilitation of sale of electric power to local electric utilities have greatly stimulated interest in industrial cogeneration. In particular, the ability to sell excess or all cogenerated electric power (i.e. arbitrage) has widened the options available to a potential cogenerator. In the present paper we consider a comparison of alternate cogeneration plants with an existing steam-only plant in terms of energy conservation and engineering economics. The concept of marginal cost of production is applied throughout. The criterion of economic selection is acceptable incremental rate of return on incremental investment based on the challenger-defender test of successively greater capital costs. As an example, coal-fired topping steam turbines as well as natural-gas-fired gas turbines and oil-fired diesels with waste-heat boilers are considered to replace a gas-fired steam-only plant and provide a range of electric power for the same thermal load.
In this paper, exergy analysis of a heat-matched bagasse-based cogeneration plant of a typical 2500tcd sugar factory, using backpressure and extraction condensing steam turbine is presented. In the analysis, exergy methods in addition to the more conventional energy analyses, are employed to evaluate overall and component efficiencies and to identify and assess the thermodynamic losses. The analysis is carried out for a wide range of steam inlet conditions selected around the sugar industry’s export cogeneration plant. The results show that, at optimal steam inlet conditions of 61bar and 475°C, the backpressure steam turbine cogeneration plant perform with energy and exergy efficiency of 0.863 and 0.307 and condensing steam turbine plant perform with energy and exergy efficiency of 0.682 and 0.260, respectively. Boiler is the least efficient component and turbine is the most efficient component of the plant.
The cogeneration of steam and electricity has become the norm in the sugarcane industry worldwide. This process has been taken further to a stage where sugar companies can export a substantial amount of energy to the grid. Mauritius and Reunion Islands have implemented state of the art technology in bagasse energy cogeneration. It is on this basis that the potential for cogeneration in Zimbabwe’s sugar industry is being examined. The findings indicate that it is technically feasible to implement such a project. A full economic and financial feasibility study would still need to be done. Two plants of 105 MW each can be put in place, providing about 517 GWh of clean bagasse firm power to the Zimbabwe Electricity Supply Authority. Bagasse would be used during the crop season and coal during the off-crop season. Coal usage during the off-season, will enable the exportation of extra power to the grid. This kind of project, which can save money for the utility, meets about 8% of the country’s electrical energy needs, reduces the amount of foreign currency needed to import electricity, results in improved efficiency in the sugar industry and can avoid the use of 293 750 tonnes of coal, hence avoiding the emission of 885 000 tonnes of carbon dioxide and the production of 47 000 tonnes of coal ash. The sugar millers would accrue revenue benefits equal to those revenues from selling sugar that accrue to the milling activities only.
In this paper, the energy and exergy analyses of the drying process of thin layer drying of bagasse are investigated. Drying experiments were conducted in a laboratory scale dryer for a wide range of air temperatures (80 to 120°C), velocities (0.5 to 1.5 m/s), humidity of air (9 to 24gm/Kg of d.a) and product thickness (20 to 60 mm). For the system, energy analysis was carried using first law of thermodynamics to estimate the energy utilization ratio (EUR). Exergy analysis was accomplished to determine the magnitude of exergy losses during the drying process by applying the second law of thermodynamics. The energy required for 30% moisture reduction was estimated for different drying conditions, which varied between 1.07 to 1.49 KW-hr Kg -1 . It is observed that the variation of air velocities for a given constant temperature influences the EUR and exergetic efficiency significantly than that for the conditions of varying temperatures for a constant air velocity.
A thermodynamic study of an 88.4 MW cogeneration plant located in the United States is presented in this paper. The feedstock for this actual plant is culm, the waste left from anthracite coal mining. Before combustion in circulating fluidized bed boilers, the usable carbon within the culm is separated from the indigenous rock. The rock and ash waste from the combustion process fill adjacent land previously scared by strip mining. Trees and grass are planted in these areas as part of a land reclamation program. Analyses based on the first and second laws of thermodynamics using actual operating data are first presented to acquaint the reader with the plant's components and operation. Using emission and other relevant environmental data from the plant, all externalities study is outlined that estimates the plant's effect on the local population. The results show that the plant's cycle performs with a coefficient of utilization of 29% and all approximate exergetic efficiency of 34.5%. In order to increase these values, recommended improvements to the plant are noted. In addition, the externality costs associated with the estimated SOâ and NOx discharge from the culm fed plant are lower (85-95%) than those associated with a similarly sized coal fed plant. The plant's cycle efficiencies are lower than those associated with more modern technologies; such as all integrated gas turbine combined cycle. However, given the abundant, inexpensive supply of feedstock located adjacent to the plant and the environmental benefit of removing culm banks, the plant's existing operation is unique from an economical and environmental viewpoint.
A conceptual gas turbine based cogeneration cycle with compressor inlet air cooling and evaporative after cooling of the compressor discharge is proposed to increase the cycle performance significantly and render it practically insensitive to seasonal temperature fluctuations. Combined first and second-law approach is applied for a cogeneration system having intercooled reheat regeneration in a gas turbine as well as inlet air cooling and evaporative after cooling of the compressor discharge. Computational analysis is performed to investigate the effects of the overall pressure ratio r(p), turbine inlet temperature (TIT), and ambient relative humidity p on the exergy destruction in each component, first-law efficiency, power-to-heat ratio, and second-law efficiency of the cycle. Thermodynamic analysis indicates that exergy destruction in various components of the cogeneration cycle is significantly affected by overall pressure ratio and turbine inlet temperature, and not at all affected by the ambient relative humidity. It also indicates that the maximum exergy is destroyed during the combustion process, which represents over 60% of the total exergy destruction in the overall system. The first-law efficiency, power-toheat ratio, and second-law efficiency of the cycle significantly vary with the change in the overall pressure ratio and turbine inlet temperature, but the change in relative humidity shows small variations in these parameters. Results clearly show that performance evaluation based on first-law analysis alone is not adequate, and hence, more meaningful evaluation must include second-law analysis. Decision makers should find the methodology contained in this paper useful in the comparison and selection of advanced combined heat and power systems.
Exergy optimization is presented for an irreversible combined cogeneration cycle which includes three types of irreversibilities: finite rate heat transfer, heat leakage and internal irreversibility. The optimal design conditions at maximum exergy output and maximum exergy efficiency output were determined. The effects of the internal irreversibility, heat leakage and heat to power ratio on the exergetic performance are investigated and the results are discussed. It is shown that the optimal exergetic performance intervals stay approximately constant with power to process heat ratio, but they decrease with irreversibility parameter.
The cement production is an energy intensive industry with energy typically accounting for 50-60% of the production costs. In order to recover waste heat from the preheater exhaust and clinker cooler exhaust gases in cement plant, single flash steam cycle, dual-pressure steam cycle, organic Rankine cycle (ORC) and the Kalina cycle are used for cogeneration in cement plant. The exergy analysis for each cogeneration system is examined, and a parameter optimization for each cogeneration system is achieved by means of genetic algorithm (GA) to reach the maximum exergy efficiency. The optimum performances for different cogeneration systems are compared under the same condition. The results show that the exergy losses in turbine, condenser, and heat recovery vapor generator are relatively large, and reducing the exergy losses of these components could improve the performance of the cogeneration system. Compared with other systems, the Kalina cycle could achieve the best performance in cement plant.
Zimbabwe has suffered electrical power shortages resulting in electrical energy imports rising to between 40% and 50% of total energy needs. Electricity generation capacity has stagnated at around 2000 Megawatts (MWe) since 1985, when two thermal units totaling were completed at Hwange. The effective capacity is . The current plan is to increase capacity by installing at Hwange at a cost of at least US $ 600 million. Raising this level of capital is difficult hence over the last 15 years there has been a failure to increase capacity. This article is based on a study of bagasse cogeneration in Zimbabwe and Mauritius conducted over a two-year period. It discusses technology improvements that can be made in the sugar sector to improve process and energy efficiency for the purposes of becoming an independent power producer that supplies power to the grid continuously throughout the year. Power plant investment in the sugar industry offers a bridging and realizable alternative for electricity generation in Zimbabwe. Investment in a bagasse (moisturized fiber left when sugar has been extracted from sugarcane) system would require a capital of about US$ 35 million using modern technology based on experiences in Mauritius and Reunion. A technical and economic evaluation and analysis reveals that bagasse power development is technically and economically feasible if electricity is priced at the long-term marginal cost. At current import prices, financial assistance from the global environment facility and/or the clean development mechanism of the Kyoto protocol would be necessary. The solving of the current political and economic problems in the country would pave the way for attracting a technical partner and development, of bagasse power using domestic and international financing.
In this paper we focus on energy flows and specifically on the complex interactions between heat and power generation and use in steam systems along with combustible wastes of the process. Our objective is to present a systematic methodology for the quick targeting of power cogeneration potential in steam systems ahead of designing the power generation network. The devised approach makes effective utilization of combustible wastes and reconciles the use and dispatch of process fuel sources, heating and non-heating uses of steam, and power generation. The new concept of extractable energy is introduced to facilitate a simple calculation of cogeneration potential in the process. Balances around steam headers are used to identify surpluses and deficits. Next, surplus and deficit composite curves are constructed to identify feasible transfers of extractable energy. The result is the identification of the cogeneration target and excess steam that can be used in condensing turbines. This methodology takes a holistic view of the process and can easily be combined with other mass and energy integration techniques. It specifically accommodates both (a) production objectives (mass integration) and (b) heat recovery network targeting and utility selection (energy integration). An example problem is presented to illustrate the methodology.
Legislative regulations in favor of combined heat and power (CHP) production have been implemented in many countries. Although these regulations put different emphasis on power production vs. process heat production, they are based on energy quantities and not on exergy. In order to analyze and compare the exergetic consequences of the various legislations, a relative avoided irreversibility (RAI) is defined. This can be regarded as the exergy loss that is avoided when reference plants with separate production are replaced by an actual CHP plant. Some series of industrial and district heating CHP plants, under varying operational conditions, are used as test cases. It is seen that some, but not all, CHP cases are exergetically beneficial to separate generation. Comparison with the RAI allows a quantitative assessment of the various performance indicators. It is seen that exergetic improvements were only captured to a limited degree by the various energy-based efficiency indicators. Some legislatively defined indicators even appear to discourage thermodynamic improvements.
Efficiencies and other indicators of the performance of combined heat and power (CHP) are reviewed and compared. The emphasis is put on those indicators that are used in the legislation of Belgium (Flanders, Brussels and Walloon regions), the Netherlands, Spain, Portugal, the UK and the USA. These are compared with an exergy based evaluation of CHP. Several series of test cases are run for a boiler and steam turbine (ST) plant and with a gas turbine (GT) plant with heat recovery steam generator (HRSG) and steam turbine. Both plants are simulated with two different steam pressure levels, and varying steam delivery loads by either reducing firing or increasing the condensing tail steam turbine (CTST) loads. All indicators used in the legislations are based on energy. It was seen that only the US, Dutch and Belgian indicators credit the better utilization of a GT system compared to a ST system. All indicators discourage high load on the CTST, and most of them are stronger than if based on the exergy efficiency. Contrary to the evaluation by exergy efficiency, low pressure steam is favored to medium pressure steam by all the indicators.
In this paper, performance assessment of various building cogeneration systems is conducted through energy and exergy efficiencies. The cogeneration plants considered include steam-turbine system, gas-turbine system, diesel-engine system, and geothermal system. Here, the cogeneration operation refers to the simultaneous generation of electrical power and heating for buildings (especially for space heating and hot water). Selected actual operating data are employed for analysis and performance assessment. The same amount of electrical and thermal product outputs is considered for all systems, except the diesel, to facilitate comparisons. Also, the effects of certain operating parameters (e.g., steam pressure, water temperature) on the energy and exergy efficiencies are investigated. The diesel-engine and geothermal systems appear to be thermodynamically more attractive, in that they have higher exergy efficiencies, than steam-turbine and gas-turbine systems. The results demonstrate that exergy analysis is a useful tool in performance assessments of cogeneration systems and permits meaningful comparisons of different cogeneration systems based on their merits. Such results can allow the efficiency of cogeneration systems to be increased, and the applications of cogeneration in larger energy systems to be configured more beneficially, leading to reductions in fuel use and environmental emissions.
With the increase in industrialisation coupled with population growth, the demand for power is rapidly increasing, thereby jeoparadising the economic and social growth of the country. In addition to power from conventional sources, the New & Renewable Energy Sources (NRES) has been found to have enormous potential. About 800 MW of power from renewables has already been created while about 2000 MW is likely to be added in near future. Among the NRES, bagasse based co-generation of surplus power in Indian sugar mills has been given a new boost, as more than 3500 MW of surplus power potential exist in sugar mills only (10,700 MW from all industries). These industries are being encouraged by the Govt. of India to generate surplus power & feed to the grid by offering a number of incentive schemes.An attempt has been made in this paper to present energy scenario, co-generation potential, technological options available, incentives for encouraging power generation in sugar industry, techno-economic analysis of co-generated power and future scope of research & development in this vital field.
To meet India's projected power demand over the next 25 years, over 300,000 MWe of new generating capacity will need to be installed. Cogeneration, the combined generation of steam and electricity, is an efficient and cost-effective means to save energy and reduce pollution. Many studies around the world have identified sugar mill cogeneration as an attractive low-cost power option. Most studies estimate the cogeneration potential of India's sugar mills at around 3500 MWe. The United States Agency for International Development (USAID) has implemented a Greenhouse Gas Pollution Prevention (GEP) Project to assist in the direction and pace of India's power sector development. This seven-year, US$19 million effort is funded through the United States' contribution to the pilot phase of the Global Environmental Facility (GEF). The GEF's mission is to assist developing countries in investing in environmental protection initiatives that yield global benefits in terms of reduced or avoided greenhouse gas emissions. Technical aspects of the GEP Project are being managed by the United States Department of Energy's Pittsburgh Energy Technology Center. The objective of the Advanced Bagasse Cogeneration (ABC) Component of the GEP Project is to promote year-round cogeneration in Indian sugar mills with power export using only biomass as a fuel. The structure of the ABC Component, which is implemented through technical assistance and investment subcomponents, and the status of various activities are reviewed. Also, sugar production and economics are reviewed from both a global and local perspective to reveal how they impact the potential for cogeneration projects in Indian sugar mills. Progress in the Indian sugar industry should pave the way for cogeneration projects in other industrial sectors, such as paper, chemicals, and textiles. Contributions from these sectors are important if India is to meet its huge power generation needs.
This paper is Part 2 of the study on the exergetic and thermoeconomic analysis of diesel engine powered cogeneration (DEPC) systems. In Part 1, formulations and procedure for such a comprehensive analysis are provided while this paper provides an application of the developed formulation that considers an actual DEPC plant installed in Gaziantep, Turkey. The plant has a total installed electricity and steam generation capacities of 25.3 MW and 8.1 tons/h at 170 °C, respectively. Exergy destructions, exergy efficiencies, exergetic cost allocations, and various exergoeconomic performance parameters are determined for the entire plant and its components. The exergy efficiency of the plant is determined to be 40.6%. The exergoeconomic analysis is based on specific cost method (SPECO) and it is determined that the specific unit exergetic cost of the power produced by the plant is 10.3 $/GJ.
Variable correlations are usually neglected during parameter estimation. Very frequently these are gross assumptions and may potentially lead to inadequate interpretation of final estimation results. For this reason, variable correlation and model parameters are sometimes estimated simultaneously in certain parameter estimation procedures. It is shown, however, that usually taking variable correlation into consideration during parameter estimation may be inadequate and unnecessary, unless independent experimental analysis of measurement procedures is carried out.
So far, the cumulative capacity of renewable energy systems such as bagasse cogeneration in India is far below their theoretical potential despite government subsidy programmes. One of the major barriers is the high investment cost of these systems. The Clean Development Mechanism (CDM) provides industrialized countries with an incentive to invest in emission reduction projects in developing countries to achieve a reduction in CO2 emissions at lowest cost that also promotes sustainable development in the host country. Bagasse cogeneration projects could be of interest under the CDM because they directly displace greenhouse gas emissions while contributing to sustainable rural development.
This study assesses the maximum theoretical as well as the realistically achievable CDM potential of bagasse cogeneration in India. Our estimates indicate that there is a vast theoretical potential of CO2 mitigation by the use of bagasse for power generation through cogeneration process in India. The preliminary results indicate that the annual gross potential availability of bagasse in India is more than 67 million tonnes (MT). The potential of electricity generation through bagasse cogeneration in India is estimated to be around 34 TWh i.e. about 5575 MW in terms of the plant capacity. The annual CER potential of bagasse cogeneration in India could theoretically reach 28 MT. Under more realistic assumptions about diffusion of bagasse cogeneration based on past experiences with the government-run programmes, annual CER volumes by 2012 could reach 20–26 million. The projections based on the past diffusion trend indicate that in India, even with highly favorable assumptions, the dissemination of bagasse cogeneration for power generation is not likely to reach its maximum estimated potential in another 20 years. CDM could help to achieve the maximum utilization potential more rapidly as compared to the current diffusion trend if supportive policies are introduced.