Combined Cogeneration System Research Articles

Exploring energetic, exergetic, economic and environmental (4E) performance of waste heat power generation in nuclear power plant systems: A perspective of pattern recognition

Combined cogeneration systems are employed to recover waste heat from the sCO2 cycle in nuclear power generation systems. However, dealing with their multidimensional and nonlinear design and optimization spaces is a complex challenge for designers. In this study, the combined cogeneration system is parameterized and modeled: 4E models including energetic, exergetic, economic and environmental are established for sCO2 combined Organic Rankine Cycle (sCO2/ORC) and trans-critical CO2 Cycle (sCO2/tCO2) respectively. Several decision variables and five performance indicators are selected. To gain a deeper understanding of the mechanisms and optimize the combined cogeneration system, pattern recognition methods including the Self-Organizing Map (SOM), an unsupervised competitive learning approach, and Statistical Sobol Global Sensitivity Analysis methods are proposed. These techniques help identify key parameters and system patterns within the design space. Then, the Non-Dominated Sorting Whale Optimization Algorithm (NSWOA) is adopted to build a Pareto-optimal decision space, and the SOM and PCPs are proposed to visualize and mining based on pattern recognition and graph visualization interaction. The design parameters of the top cycle, P2, PRc, and x, have been confirmed as having a substantial impact on the system's performance. The multiple attributes, criterions and objectives problems in the combined cogeneration system are ultimately simplified to “Economy-Environment”, double objectives problem, and three trade-offs’ solutions are discussed: prioritizing economics, prioritizing the environment, and finding a balanced economic-environmental compromise. Pattern recognition method provides decision-makers with a fresh perspective for gaining a deeper understanding of the multi-criteria objectives space and potential trade-offs. The integration of pattern recognition into the thermodynamic, economic, and environmental models outlined in this paper represents a substantial and valuable advancement in the analysis and optimization of combined cogeneration cycles.

A power dispatch model for a ferrochrome plant heat recovery cogeneration system

A Organic Rankine Cycle waste heat recovery cogeneration system for heat recovery and power generation to relieve grid pressure and save energy cost for a ferrochrome smelting plant is investigated. Through the recovery and utilization of previously wasted heat from the facility’s internal smelting process off-gases, the cogeneration system is introduced to generate electrical power to supply the on-site electricity demand and feed electricity back to the utility grid when it is necessary and beneficial to do so. In addition, the cogeneration system generates cooling power through a lithium bromide-water solution absorption refrigeration cycle to meet the cooling requirements of the plant. The heat recovery process for power generation is modeled and the optimal power dispatching between the on-site loads and the utility grid is formulated as an economic power dispatching (EPD) problem, which aims to maximize the plant’s economic benefits by means of minimizing the cost of purchasing electricity from the utility and maximizing revenue from selling the generated electricity to the grid. Application of the developed model to a ferrochrome smelting plant in South Africa is presented as a case study. It is found that, for the studied case, more than $1,290,000 annual savings can be obtained as a result of the proposed heat recovery power generation system and the associated EPD model. In addition to this, more than $920,000 annual savings is obtained as a result of the generated cooling power via the proposed absorption refrigeration system. The combined cogeneration system is able to generate up to 4.4MW electrical power and 11.3MW cooling power from the recovered thermal energy that was previously wasted.

Integration of a Solid Oxide Fuel Cell with an Absorption Chiller for Dynamic Generation of Combined Cooling and Power for a Residential Application

Our novel idea is a highly efficient, zero emission solid oxide fuel cell (SOFC) system that can be dynamically dispatched to produce electricity, hydrogen fuel, and cooling in various amounts to meet energy and power demands of a single residence. Although SOFC systems exhibit high electrical efficiency, in practical applications almost half of the fuel energy is converted to heat. The SOFC high temperature (high quality) heat can be used as the primary thermal energy source to supply cooling or heating or to produce extra electricity through a bottoming cycle. In this study the waste heat from the fuel cell is captured and processed through an absorption chiller (AC) to provide cooling for meeting the cooling demand of a single residence. High purity hydrogen gas can also be produced by the SOFC system as an energy co-product using the tri-generation concept of lower fuel utilization followed by hydrogen separation from the anode off-gas. Hydrogen as an energy carrier can be stored for later use, as fuel for transportation use in a fuel cell electric vehicle. The integration of an absorption chiller and hydrogen separation unit with an SOFC could create a highly dispatchable system that can meet the dynamics of measured residential power and cooling while producing hydrogen fuel for fuel cell electric vehicle demand. Dynamic dispatch and control strategies are needed to safely operate such an SOFC system, keep it within the required operating envelope, and avoid premature degradation. A spatially resolved dynamic model was developed in Matlab/Simulink to simulate the dynamic operating characteristics of an SOFC system. A commercially available 1.5 kW SOFC system was selected and acquired for model verification and performance evaluation. Preliminary results from the dynamic model of the SOFC show that the SOFC exhaust retains sufficient quality heat for use in an absorption chiller. A dynamic absorption chiller model is developed to study the dynamic characteristics and the performance of the combined co-generation system. Actual dynamic data from a single residential house located in Irvine California is used as an input to evaluate the dynamic operation of the SOFC-AC model. The integrated Tri-generation system was then evaluated in terms of efficiency, capacity, dynamic operation and control to meet the measured power, cooling, and fuel demands of the residence. The proposed system may offer a high efficiency and low emissions conversion solution that meets the dynamic demands for residential power, cooling, and transportation end-uses.

Integration of a Solid Oxide Fuel Cell with an Absorption Chiller for Dynamic Generation of Combined Cooling and Power for a Residential Application

In this study the waste heat from a 2.5 kW solid oxide fuel cell (SOFC) is captured and processed through a 1.5 kW absorption chiller (AC) to provide cooling for a single residence. The integration of an AC with an SOFC could create a highly dispatchable system that can meet the dynamics of measured residential power. A spatially resolved dynamic model was developed in Matlab/Simulink to simulate the dynamic operating characteristics of an SOFC system. A dynamic AC model was developed to study the dynamic characteristics and the performance of the combined co-generation system. Actual dynamic data from a single residential house was used as an input of the SOFC-AC model. For a single week, the SOFC was capable of following the highly dynamic load with an average efficiency of 56%. The AC generated 15.6 kWh of cooling with an average COP and cooling of 1.09 and 0.65 kW, respectively.

The thermodynamic efficiency characteristics of combined cogeneration system of 120MW

The thermodynamic efficiency characteristics of combined cogeneration system of 120MW

Proposal and performance assessment of novel combined ORC and HDD cogeneration systems

In this paper, four combined cogeneration systems including the Humidification-Dehumidification Desalination (HDD) and Organic Rankine Cycle (ORC) are investigated from thermodynamic and economic viewpoints. In the first scenario, the outlet water flow of ORC condenser enters the HDD directly as feed water. In the second scenario, the temperature of ORC condenser outlet water rises in a heat exchanger by the ORC evaporator heat source outlet flow before entering the HDD. In the third scenario, the ORC evaporator heat source outlet flow passes through a heat exchanger to heat the HDD feed water. The fourth scenario is a combination of scenarios (I) and (III) so that it contains both of them in one configuration. In all the scenarios the ORC waste heat either from its condenser or evaporator is utilized. Results show that the ORC with toluene produces more power and that scenarios (IV) and (II) produce more desalinated water compared to the other scenarios. It is also observed that, compared to seven working fluids, using n-heptane as a working fluid in these two scenarios results in the highest distilled water production rate. It is concluded that the least distilled water unit cost is achieved by the scenarios (I) and (II), respectively and that using n-heptane, among the other working fluids, brings about the least unit cost for produced distilled water.

Thermo-Economic Analysis of Combined Cycle MED-TVC Desalination System

Abstract In the present work, thermo-economic model of a superstructure combined cogeneration power plant is studied. Engineering Equation Solver “EES” code is used to study the enhancement of the thermal performance, the environmental impact and the economics cost of the plant. Optimum design point for maximum production of power and water is obtained, through developing mathematical model of separate system, and combined cogeneration system, at different operating conditions. Also, economics model, including capital cost of each unit, fuel cost, operating and maintenance cost, is developed. It is concluded that, the combined cogeneration system can save about 20.6% of Total Annual Cost “TAC” compared with separate power and water production system. The cogeneration plant consists of Gas Turbine (GT), Heat Recovery Steam Generator (HRSG), Steam Turbine (ST) and Multi Effect -Thermo Vapor Compressor Desalination System (MED-TVC).

Multi-objective optimization for the design and synthesis of utility systems with emission abatement technology concerns

The sustainable design configuration of utility systems incorporating pollutant emission abatement technologies has an important influence on economic cost, pollutant emission, and energy consumption of the process industry. In this paper, four typical cogeneration systems that address different emission reduction technologies are proposed as candidate structures for utility system design. The proposed systems are a gas boiler-based cogeneration system firing clean natural gas, circulating fluidized bed boiler-based cogeneration system incorporating SO2 abatement during combustion, pulverized coal boiler-based cogeneration system encompassing desulfurization and denitration after combustion, and gas–steam combined cogeneration system firing clean natural gas. The equipment performance, energy consumption, material consumption, pollutant emission, and investment and operation cost models of these cogeneration systems, as well as the corresponding emission abatement processes, are established. A multi-objective mixed integer nonlinear programming (MOMINLP) model is formulated to determine the equipment type (or cogeneration system and emission abatement technology), equipment number, equipment design capacity, and equipment operation load while simultaneously combining the multiple objectives of minimization of economic cost, minimization of environmental effect, and maximization of exergy efficiency. The original MOMINLP model is converted into a multiple objective mixed integer linear programming (MOMILP) model through linear approximation, unit size discretization, and relaxation. The augmented ε-constraint method is applied to identify the set of Pareto optimal solutions with respect to the aforementioned objective functions. An example of industrial utility system design optimization was presented. In addition, the best combination of cogeneration system for utility system structure under different objective was introduced. The sensitivity of the solutions to the primary energy source price and power to heat ratio was conducted.

Energy and Exergy Analyses of a New Combined Cycle for Producing Electricity and Desalinated Water Using Geothermal Energy

A new combined cogeneration system for producing electrical power and pure water is proposed and analyzed from the viewpoints of thermodynamics and economics. The system uses geothermal energy as a heat source and consists of a Kalina cycle, a LiBr/H2O heat transformer and a water purification system. A parametric study is carried out in order to investigate the effects on system performance of the turbine inlet pressure and the evaporator exit temperature. For the proposed system, the first and second law efficiencies are found to be in the ranges of 16%–18.2% and 61.9%–69.1%, respectively. For a geothermal water stream with a mass flow rate of 89 kg/s and a temperature of 124 °C, the maximum production rate for pure water is found to be 0.367 kg/s.

Proposal and analysis of a new combined cogeneration system based on the GT-MHR cycle

In this paper, the waste heat from a gas turbine-modular helium reactor (GT-MHR) is utilized to produce power through two Organic Rankine Cycles (ORCs) and pure water by means of distillation processes. An Absorption heat transformer (AHT) is employed to upgrade the lower temperature waste heat in order to run the desalination system. Detailed thermodynamic analyses for the proposed combined cogeneration cycle (CC cycle) are presented and the effects of important parameters on the cycle performance were studied. The proposed cycle performance is then optimized based on the first law of thermodynamics. The results show that the first law efficiency of the CC cycle, at the optimum conditions, is around 7% higher than that of the GT-MHR cycle. It was also concluded that for each 50 °C increase in the gas turbine inlet temperature, the thermal efficiency is increased by around 2.5–4% and the pure water production rate is decreased by around 6.5%. The results also showed that employing R1234yf as working fluid in the ORCs instead of R123 gives almost the same results in the cycle performance.

Efficiency Analysis of Combined Cogeneration Systems with Steam and Gas Turbines

Increasing demand of energy and adverse environmental impact of the use of fossil fuels emphasized the need of using renewable energy. At this stage, cogeneration has come into question. Cogeneration, also called combined heat and power, is a consecutive generation of electrical power and heat energy. It is an efficient and cost-effective means to save energy and reduce emissions of human origin. In this study, a combined cogeneration system has been investigated. This cogeneration system uses a combined gas/steam turbine and draws gap steam from the steam turbine for heat production. Thermodynamic analysis of the system has been done and effects of some design parameters on performance values have been examined.

Analysis of combustion turbine inlet air cooling systems applied to an operating cogeneration power plant

In this work, combustion turbine inlet air cooling (CTIAC) systems are analyzed from an economic outlook, their effects on the global performance parameters and the economic results of the power plant. The study has been carried out on a combined cogeneration system, composed of a General Electric PG 6541 gas turbine and a heat recovery steam generator. The work has been divided into three parts. First, a revision of the present CTIAC technologies is shown, their effects on power plant performance and evaluation of the associated investment and maintenance costs. In a second phase of the work, the cogeneration plant was modelled with the objective of evaluating the power increase and the effects on the generated steam and the thermal oil. The cogeneration power plant model was developed, departing from the recorded operational data of the plant in 2005 and the gas turbine model offered by General Electric, to take into consideration that, in 2000, the gas turbine had been remodelled and the original performance curves should be corrected. The final objective of this model was to express the power plant main variables as a function of the gas turbine intake temperature, pressure and relative humidity. Finally, this model was applied to analyze the economic interest of different intake cooling systems, in different operative ranges and with different cooling capacities.

404 木質バイオマス燃料によるスターリングエンジン/ヒートポンプ複合コージェネレーションシステムのエネルギーバランス(機械力学・計測制御I,環境工学,計測制御・機械力学,流体工学,熱工学,環境工学)

404 木質バイオマス燃料によるスターリングエンジン/ヒートポンプ複合コージェネレーションシステムのエネルギーバランス(機械力学・計測制御I,環境工学,計測制御・機械力学,流体工学,熱工学,環境工学)

Energetic efficiency of cogeneration systems for combined heat, cold and power production

This paper deals with the problem of energetic efficiency evaluation of cogeneration systems for combined heat, cold and power production. Cogeneration systems have a large potential for energy saving, especially when they simultaneously produce heat, cold and power as useful energy flows. Various cogeneration systems for combined heat, cold and power production are designed by means of computer simulation to minimize consumption of the primary energy. Equations of energetic efficiency of this combined cogeneration systems are presented, that relate the primary energy rate (PER) and comparative primary energy saving (Δ q p) to energy parameters of designed systems. Comparison of energetic efficiency of combined cogeneration systems with contemporary conventional separate production of heat, cold and power shows a large potential for energy saving by designed combined cogeneration systems.