Theory Of Thermoeconomics Research Articles

Environmental thermoeconomic performance analysis of gas turbine combined cycle under off‐design conditions

AbstractAlthough the gas turbine combined cycle (GTCC) system has better environmental performance, it still emits pollution gases such as CO2 and NOx. It is reasonable and necessary to add the environmental cost to the power production cost of the GTCC system. Based on the structure theory of thermoeconomics, through the reasonable pricing of pollutants (considering the environmental costs of CO2 and NOx emission), the system environmental thermoeconomic cost (ETC) model is developed in this study, which achieves absolute internalization of environmental costs. Taking GTCC with different gas turbine (GT) operation strategies as the research object, the influences of different operation strategies and environmental conditions on the GTCC system ETC are studied. The results of this study show that it is beneficial to maintain higher turbine inlet temperatures (T3) and turbine outlet temperatures (T4), thus ensuring better GTCC environmental thermoeconomic performance, and GTCC with the operation strategy (using inlet guide vane (IGV) control to maintain T3 at the design value and then to keep T4 at its maximum value (IGVT3‐650‐F) has the lowest ETC, which are 0.09429 $/kW·h at 75% gas turbine load rate (GTLR) and 0.10079 $/kW·h at 50% GTLR, respectively; reducing the emission of pollutants can reduce the unit ETC; for the combustion chamber, as the pollutant generation component of GTCC unit, it is most affected by the environmental damage cost; reducing the inlet air temperature can improve the system environmental thermoeconomic performance.

Multi-objective optimization of gas turbine combined cycle system considering environmental damage cost of pollution emissions

Currently, most of the performance analysis and optimization design of the gas turbine combined cycle (GTCC) units ignore the economic loss to the environment caused by the pollutant emissions. In this paper, based on the structure theory of thermoeconomics, an environmental thermoeconomic cost model is established. And then an annual total cost model is established, which can reflect the real economic performance. Based on the comprehensive analysis of the energy, economy and environment, with the objectives of the higher exergy efficiency, less annual total cost and lower specific CO2 emission rate, a multi-objective optimization study of the GTCC unit is conducted using the genetic algorithm (GA) in this paper. Pareto frontiers for the multi-objective optimization has been obtained with GA, and in turn a design plan can be selected from the Pareto frontier according to the preference. The multi-objective optimization results show that the optimized system can greatly increase the system environmental thermoeconomic performance. Moreover, the effects of main variables on the economic performance index of the optimized system are investigated. The results show that the natural gas price has the greater impact on the economic performance index compared with the pollutants environmental damage cost and the non-energy cost.

Thermoeconomic Diagnosis of the Sequential Combustion Gas Turbine ABB/Alstom GT24

In this study, we used the thermoeconomic theory to evaluate the impact of residue cost formation on the cost of electricity generated from natural gas burned in a gas turbine that applied sequential combustion; we also analyzed the impact of the combustion process on the additional fuel consumption to compensate for a malfunction component. We used the Alstom GT24 gas turbine, which applied sequential combustion and generated 235 MW of power. Thermoeconomic analysis indicated that the exergy cost of power generation was 626.33 MW (30.42% corresponded to irreversibility costs, and 29.22% and 2.84% corresponded to the formation costs of physical and chemical residues, respectively). The exergoeconomic production cost of gas turbine was 10,098.71 USD/h, 34.76% from external resources and 65.24% from capital and operating costs. Thermoeconomic diagnosis revealed that a compressor deterioration (of 1-% drop in the isentropic efficiency) resulted in an additional fuel consumption of 4.05 MW to compensate for an increase in irreversibilities (1.97 MW) and residues (2.08 MW); the compressor generated the highest cost (49.9% of additional requirement). Thus, our study can identify the origin of anomalies in a gas-turbine system and explain their effects on the rest of the components.

Thermoeconomic cost analysis on operation strategies of gas turbine combined cycle under off-design conditions

In this paper, the thermoeconomic cost model of a typical gas turbine combined cycle (GTCC) system is established based on the structure theory of thermoeconomics. Because the operation strategy is the basis of the research on the design/off-design condition of GTCC unit. Therefore, the GTCC thermoeconomic performances with different strategies using the inlet guided valve (IGV) control are compared based on the GTCC cost model to analysis the influence of the main parameters on the unit thermoeconomic cost of each component. The variation rules of the thermoeconomic performances of the GTCC unit under design/off-design operating conditions influenced by the operating strategy and ambient temperature are revealed. The results show that the GTCC with the IGV T3-650-F operation strategy has the lowest thermoeconomic cost. Changing the operation strategy of gas turbine (GT) can reduce the generator (GEN) unit thermoeconomic cost. And higher GT inlet/outlet temperature is helpful to reduce the thermoeconomic cost of combined cycle under off-design conditions. The investment on the steam turbine (ST) and the irreversibility of the combustion chamber (CC) have the important influence on the thermoeconomic cost of GTCC system. Reducing the air compressor (AC) inlet air temperature can reduce the thermoeconomic cost of GTCC system.

Thermoeconomic Optimization of Steam Pressure of Heat Recovery Steam Generator in Combined Cycle Gas Turbine under Different Operation Strategies

The optimization of the steam parameters of the heat recovery steam generators (HRSG) of Combined Cycle Gas Turbines (CCGT) has become one of the important means to reduce the power generation cost of combined cycle units. Based on the structural theory of thermoeconomics, a thermoeconomic optimization model for a triple pressure reheat HRSG is established. Taking the minimization of the power generation cost of the combined cycle system as the optimization objective, an optimization algorithm based on three factors and six levels of orthogonal experimental samples to determine the optimal solution for the high, intermediate and low pressure steam pressures under different gas turbine (GT) operation strategies. The variation law and influencing factors of the system power generation cost with the steam pressure level under all operation strategies are analyzed. The research results show that the system power generation cost decreases as the GT load rate increases, T4 plays a dominant role in the selection of the optimal pressure level for high pressure (HP) steam and, in order to obtain the optimum power generation cost, the IGV T3-650-F mode should be adopted to keep the T4 at a high level under different GT load rates.

Study on the Coupling Effect of a Solar-Coal Unit Thermodynamic System with Carbon Capture

Based on the structural theory of thermo-economics, a 600 MW unit was taken as an example. An integration system which uses fuel gas heat and solar energy as a heat source for post-combustion carbon capture was proposed. The physical structure sketch and productive structure sketch were drawn and a thermo-economics model and cost model based on the definition of fuel-product were established. The production relation between units was analyzed, and the composition and distribution of the exergy cost and thermo-economic cost of each unit were studied. Additionally, the influence of the fuel price and equipment investment cost of the thermo-economic cost for each product was studied. The results showed that the main factors affecting the unit cost are the fuel exergy cost, component exergy efficiency, and irreversible exergy cost of each unit, and the main factors affecting the thermo-economics cost are the specific irreversible exergy cost and investment exergy cost. The main factors affecting the thermal economics of solar energy collectors and low-pressure economizers are the invested exergy cost, negentropy exergy cost, and irreversible exergy cost of each unit.

Relative Free Energy Function and Structural Theory of Thermoeconomics

This paper explores the advantages of using relative free energy instead of exergy to build a mathematical theory of thermodynamic costs to diagnose malfunctions in thermal systems. This theory is based on the definition of a linearized characteristic equation that represents the physical behavior of each component. The physical structure of the system described by its energy interrelationships is called “primal”, and its derivatives are the costs and consumptions. The obtained costing structure is the mathematical “dual” of its primal. The theory explains why the F and P cost assessment rules and any other suggestion may (or may not be) rational under a given disaggregation scheme. A result of the theory is a new thermodynamic function, called the relative free energy, and a new parameter called deterioration temperature due to a component’s deterioration cause, characterized by a h-s thermodynamic trajectory describing the effects on the exiting stream. The relative free energy function allows for an exact relationship between the amount of used resources and the increase in entropy generation caused by the deterioration path of the component. This function allows the obtaining of, for the first time, an appropriate characteristic equation for a turbine and a new definition of efficiency that does not depend on the environment temperature but on its deterioration temperature. Also, costing with relative free energy instead of exergy may open a new path for more precise and straightforward assessments of component deteriorations.

Thermoeconomic analysis of co-firing combined cooling, heating, and power system based on energy level

In this work, exergy and exergoeconomic cost analyses are applied to biomass and natural gas co-firing in a combined cooling, heating, and power (CCHP) system, based on the structural theory of thermoeconomics. The thermoeconomic model for the investigated co-firing CCHP system is defined to quantify the productive relationships among the various components. The unit exergy/exergoeconomic cost of all flows in the productive structure are calculated by solving the characteristic equations and exergy/exergoeconomic cost equations together with the auxiliary cost allocation equations. A comparative analysis between the previous auxiliary cost allocation method and the method based on energy level is presented. Moreover, the production performance of components under summer and winter conditions are evaluated based on the exergy cost analysis. The results show that, compared with the previous method, the exergoeconomic costs of electricity with higher energy level increase 21.10 and 22.90 USD/MWh under summer and winter conditions, respectively, while the costs of other products with lower energy level decrease. Furthermore, a sensitivity analysis is presented to analyze the variation of the unit exergoeconomic cost of products with fuel prices and some non-energy factors. In conclusion, the structural theory of thermoeconomics integrated with auxiliary cost allocation equations based on the energy level can provide reasonable and accurate results for multi-product energy systems.

Thermodynamic analysis of air-compression refrigerating machine based on the exergy cost theory

On the basis of the exergy cost theory, a procedure has been developed for carrying out an in-depth thermodynamic analysis of air-compression refrigerating machines and thermal pumps taking into consideration nonequivalence of exergy losses in various links of thermotransformation process and their effect on consumption of exergy supplied to the system. A thermoeconomic model of a single-stage air-compression refrigerating machine was proposed which takes into consideration structural and topological features of the process scheme and interrelation between its elements. For an equivalent mapping of structural and topological features of the refrigerating machine scheme, a parametric flow graph was developed. The procedure uses a matrix form of recording exergy balances which is the most convenient for representation of the thermoeconomic models. In order to obtain reference operating mode of the refrigerating machine, the principle of thermodynamic process idealizing was used. Application of the structural theory of thermoeconomics has made it possible to establish the portion of endogenous and exogenous destruction of exergy in the elements of the refrigerating machine. Numerical implementation of the proposed procedure has made it possible to reveal influence of internal irreversibility in the cycle determined by non-isentropic compression processes in the compressor and expansion in the expander. A significant effect of efficiency of the expansion process in the expander on the exergy efficiency of the air-compression refrigerating machine was established. Influence of the change of ambient temperature on the character of consumption of exergy by each element of the refrigeration machine was estimated. It has been revealed that even a slight change of the ambient temperature significantly affects consumption of “fuel” by each element of the system, while the dependence is linear. Generalized dependences of exergy indicators on variable factors have been obtained which enabled finding of unfavorable operating conditions for equipment with increased energy consumption. It was established that the efficiency factor of the turboexpander has the greatest influence on the change of consumption of exergy of “fuel” in the system.

Thermoeconomic Optimization of a 450 MW Natural Gas Burning Steam Power Plant

The theory of thermoeconomics and local optimization were used to investigate how the cost of the resources consumed by a 450 MW power plant varies with the unit cost of the resources consumed, the technical production coefficients of the productive structure and/or the external demand for the products. In order to accomplish this, the costs of exergy of the productive structure were analyzed under three different conditions by using the relevant characteristic equations. In general, it was found that the thermoeconomic cost of a flow consists of two parts, namely the monetary cost of the fuel exergy (natural gas in the present study) needed to produce the flow, that is, its thermoeconomic cost and the costs due to the productive process (cost of capital equipment, maintenance, etc.). The results show that the steam leaving the boiler has the lowest exergy cost, while the condenser has the highest. The sequential quadratic programming (SQP) algorithm was used to obtain the optimized solutions of each major component of the plant. It was found that substantial operational and capital cost benefits were realized by optimizing most of the major plant equipment (boiler, turbines, feedwater heaters and the pumps). However, optimization of the condenser did not yield any cost benefit in capital equipment cost, but did produce some savings in operational cost.

The improved distribution method of negentropy and performance evaluation of CCPPs based on the structure theory of thermoeconomics

In order to evaluate the performance of components in the large gas-fired combined cycle power plant (CCPP), an improved thermoeconomic analysis method based on the structure theory of thermoeconomics is proposed. First, the fuel-product model is established; the productive structure and the distribution method of negentropy are modified. Negentropy produced and consumed in the gas turbine cycle is also considered. It is proved that the method is reasonable and practical. The exergy cost by the method is higher than that by the traditional method. Then, thermoeconomic model based on structure theory is built by using the improved distribution method of negentropy. Compared with matrix model of thermoeconomics, the accuracy and the effectiveness of the model are verified. The relative error is less than 3%, which is within the permissible range of engineering. Afterwards, relative cost difference and exergoeconomic factor are calculated. The improved relative cost difference is put forward through introduction of non-energy weighting factor. The results indicate that the heat recovery steam generator (HRSG) has a very great potential improvement. The investment on the steam turbine (ST) and the irreversibility of the combustion chamber (CC) should also be paid more attention, the decrease of which makes a great contribution to the decrease of thermoeconomic cost. It shows that the new evaluation index for components of CCPP is reasonable and will support the researches on thermoeconomic optimization of CCPPs.

Thermoeconomic cost analysis of CO2 compression and purification unit in oxy-combustion power plants

High CO2 purity products can be obtained from oxy-combustion power plants through CO2 compression and purification unit (CPU) based on phase separation method. To identify cost formation process and potential energy savings for CPU, detailed thermoeconomic cost analysis based on structure theory of thermoeconomics is applied to an optimized CPU (with double flash separators). It is found that the largest unit exergy cost occurs in the first separation process while the multi-stage CO2 compressor contributes to the minimum unit exergy cost. In two flash separation processes, unit exergy costs for the flash separator and multi-stream heat exchanger are identical but their unit thermoeconomic costs are different once monetary cost for each device is considered. For cost inefficiency occurring in CPU, it mainly derives from large exergy costs and thermoeconomic costs in the flash separation and mixing processes. When compared with an unoptimized CPU, thermoeconomic performance for the optimized CPU is enhanced and the maximum reduction of 5.18% for thermoeconomic cost is attained. To achieve cost effective operation, measures should be taken to improve operations of the flash separation and mixing processes.

The method of evaluating operation performance of HVAC system based on exergy analysis

Abstract A simulation model of an airport terminal's the heating, ventilating and air conditioning (HVAC) system is established. Based on simulation calculation, the unit exergy cost, the object exergy efficiency and the exergy loss ratio of each component of HVAC system are obtained by the structural theory of thermoeconomics. The operation performance of HVAC system and the optimum potential of each component are analyzed by those indexes. In order to evaluate the influence of the control strategy to operation efficiency of HVAC system, a new evaluation method is presented which setting ideal operating level as the criterion, using control perfect index ( CPI ) to evaluate operation performance of the HVAC system. And the energy flow process of this HVAC system is divided into two subsystem energy flow processes (the subsystem A and subsystem B ). Evaluation results show that the annual CPI and the optimum potential of the system are about 0.77 and 23%, respectively, when the original strategy is used. The optimum potential of the subsystem A is larger than the subsystem B . Two control strategies, the optimal load allocation control strategy ( Load Allocation Strategy ) and the optimal supply air temperature reset strategy ( SAT Strategy ) are presented and analyzed by this new evaluation method. Simulation calculation results show that the annual CPI of the system with the Load Allocation Strategy and SAT Strategy are about 0.82 and 0.78, respectively. The Load Allocation Strategy can improve the operation performance of the system more greatly than the SAT Strategy . It means that the evaluation method not only can evaluate the operation performance of the HVAC system, but also can give the direction for optimal control of the HVAC system.

Thermoeconomic Optimization of a 1000MW Coal-Fired Unit

In order to decrease the operation cost of a power plant, a 1000MW coal-fired power plant is studied as the research objective, and an evaluation model about unit thermoeconomic cost is built based on the thermoeconomic theory. By using the Matlab calculation tool, the thermoeconomic optimization of the energy system about the plant is presented. The results show that it is necessary to update the correlated equipment to increase its exergy efficiency in the design of the entry unit. Moreover, the exergy efficiency of the boiler is close to the optimum value, as for the steam turbine, its efficiency can be increased with the increment of investment.

Thermoeconomic Analysis of Air Conditioning Systems

In order to decrease the operation costs of air conditioning systems, an evaluation model based on unit thermoeconomic costs of thermoeconomic theory is presented in this paper. By using real components and fictitious components in an air conditioning system, the relationships between the fuel and product are established, and then the operation performances of the air conditioning system can be analyzed and evaluated. The unit thermoeconomic costs can be obtained with the experimental data. The results show that the unit thermoeconomic cost of the system is the lowest when the vaporizing temperature is at 16.3°C, and the unit thermoeconomic cost of the compressor component is the highest. Therefore, the direction and emphases of the technique improvement and performance enhancement are provided.

Exergoeconomic analysis of a combined cycle system utilizing associated gases from steel production process based on structural theory of thermoeconomics

Exergoeconomic analysis plays an important role in finding ways to improve the performance of a complex thermal system. In this article, exergoeconomic analysis had been performed for a combined cycle system, which was proposed by authors, utilizing associated gases (blast-furnace gas, coke oven gas and sintering waste gas) from steel production process based on structural theory of thermoeconomics. Three exergoeconomic indexes (the cost difference, the relative cost difference and the exergoeconomic factor) were calculated to evaluate the thermoeconomic performance of each component. Moreover, the influences of the decision variables (the pressure ratios and the isentropic efficiencies of air compressor and blast-furnace-gas compressor, the temperature of combustion products entering gas turbine, and the isentropic efficiencies of gas turbine and steam turbine) and the capital costs (equipment purchase and fuel) on the unitary exergetic and monetary costs of production were also investigated. The analysis shows the deep relations of the unitary costs to the changes in these parameters and the superiorities of the proposed system emerging gradually through comparing with other systems (the combined cycle system with afterburning chamber in heat recovery steam generator, the combined cycle system without afterburning combustion, and the power generation system of steam turbine).

Numerical model for thermoeconomic diagnosis in commercial transcritical/subcritical booster refrigeration systems

Transcritical/subcritical booster refrigeration systems are increasingly installed and used in Danish supermarkets. The systems operate in both transcritical and subcritical conditions dependent on the heat rejection performance and the ambient conditions. The plant consists of one refrigerant cycle supplying refrigerant for evaporators in both chilled and frozen display cases. In the paper, thermoeconomic theory is used to establish the cost of cooling at each individual temperature level based on operating costs.With a high amount of operating systems, faulty operation becomes an economic, and environmental, interest. A general solution for evaluation of these systems is considered, with the objective to reduce cost and power consumption of malfunctioning equipment in operation. An analysis of the use of thermoeconomic diagnosis methods is required, as these methods may prove applicable. To accommodate the analysis, a numerical model of a transcritical booster refrigeration plant is considered in this paper. Additionally the characteristic curves method is applied to the high pressure compressor unit of the refrigeration plant. The approach successfully determine whether an anomaly is intrinsic or induced in the component when no uncertainties are introduced in the steady state model.

Dynamic Exergetic Cost Analysis of a Space Heating System

The design of heating systems with groundwater source heat pumps (GWHP) is very important for reducing their power consumption. For better design, reasonable analysis of the systems is necessary. In this paper, a dynamic exergy and exergetic cost analysis of a heating system with GWHP is performed in a whole heating season by the use of structural theory of thermoeconomics and the software of TRNSYS. The relative exergy destruction of every component and the exergetic cost of the final product of the system are obtained. The results show that the heat pump has the largest relative exergy destruction under all the working conditions. The terminal unit component has the second largest relative exergy destruction at conditions above 10% load. However, at 10% load, well water transportation component has the second largest relative exergy destruction. The unit exergetic cost of the system final product during the whole heating season is 8.51W/W, similar to the result at 75% load.

Exergetic cost analysis of a space heating system

In order to evaluate and improve the design of space heating systems with groundwater source heat pumps (GWHP), common design practices should be examined. In this paper, a GWHP system with common design is studied. The COP of the heat pump is 3.5 at design condition. The system is divided into five subsystems, and exergetic cost analysis is performed on it based on structural theory of thermoeconomics. The results show that the three largest relative exergy destructions and lowest exergy efficiencies occur in power generation and distribution, heat pump, and terminal unit subsystems with relative exergy destructions of 71.2%, 17.1% and 7.02% and exergy efficiencies of 32.8%, 54.8% and 65.6% respectively. The three subsystems also have the largest increases of unit exergetic costs of 2.04 W/W, 2.15 W/W, and 2.73 W/W respectively. Therefore, designers of GWHP space heating systems should pay close attention to heat pump and terminal unit subsystems, especially to the latter one because of its larger increase of unit exergetic cost. The unit exergetic cost of the system final exergetic product is 7.92 W/W. This value can be used to evaluate the system and compare it with others from the viewpoint of energy conservation.

Optimal design of a cogeneration plant for power and desalination taking equipment reliability into consideration

This paper presents a method for incorporating equipment reliability considerations into the optimal design of cogeneration systems for power and desalination. Design optimization is carried out using thermoeconomic theory using exergy as the transferable material while equipment reliability is carried out using the state–space method that uses the Markov process. Procedure for cost allocation of power and water is described. The procedure is applied in an example cogeneration plant using a simple gas turbine, heat recovery steam generator and MSF seawater desalination plant.