Exergy Flow Diagrams Research Articles

Thermo-economic investigation and comparative multi-objective optimization of dual-pressure evaporation ORC using binary zeotropic mixtures as working fluids for geothermal energy application

This contribution performs an energy, exergy, and exergoeconomic (3E) analysis of a dual-pressure evaporation organic Rankine cycle system employing twenty different binary zeotropic mixtures as working fluids for power production from a geothermal field. To this end, the designed system is modeled, invoking the mass and energy conservation laws and the exergy and cost balance analyses. Specific Exergy Costing (SPECO) procedure is utilized to provide practical insights into the exergoeconomic aspect of the system. Comparative optimization based on the multi-objective genetic algorithm is accomplished for each mixture in order to simultaneously maximize the exergy efficiency and minimize the total cost rate using the design variables of pressure factor in low-pressure and high-pressure stages, mixture fraction, pinch point temperature differences in low-pressure and high-pressure heat exchangers, and degree of superheat in the high-pressure heat exchanger. In this regard, the Pareto frontiers are drawn for the system with all twenty different binary zeotropic mixtures. The optimal point for each mixture is obtained via the decision-making technique of LINMAP. Subsequently, the LINMAP is re-utilized to find the preferred mixture. The optimization results suggest the R123/C2Butene (96.89/3.11) mixture for this system as the optimum working fluid, considering a trade-off between a low-cost rate of $88.0651 per hr and a high exergy efficiency of 64.07 %. Finally, the exergy flow diagram is plotted to provide the exergy flow rate and the amount of exergy destruction in each segment of the system considering the optimal working fluid. In the proposed system, exergy destruction chiefly occurs within the low-pressure preheater with a value of 1061 kW, followed by the low-pressure turbine and condenser with magnitudes of about 669 kW and 266 kW, respectively.

Extended exergy analysis of a novel integrated absorptional cooling system design without utilization of generator for economical and robust provision of higher cooling demands

The focus of this study is on designing a novel system for the provision of high-capacity cooling and heating loads (4000 kW) with the utilization of absorption technology to increase economic viability and COP value of existing cooling plants via lower-grade waste heat sources (70 °C-90 °C). To achieve this aim, in the novel system, an integration including the LiBr-water solution based absorptional heat transformer (AHT), and absorptional cooling cycle (ACC), and flat plate solar collector (FPSC) systems was proposed. In the integration, the utilization of the generator in the cooling cycle was avoided with the interaction of the high-temperature LiBr-water solution (120 °C-150 °C) from the AHT system and ACC system evaporator. In this way, both the additional cost of the boiler and heat source and the enhancement of economic viability and COP value were achieved. Energy, economic, traditional, and extended exergy, sustainability, and environmental analyses were implemented in this novel system. The COP value for the cooling system was determined to be 3.10 from energy analysis. This result forms a significant indicator for achieving of the main focus of the current study with the proposed novel system. The annual heating and cooling duty generations with this novel system were computed as 52.37 GWh and 52.40 GWh, respectively. In the context of economically comparing the proposed system to other plants with similar scale that already exist, the initial overall expenditure, yearly operational expenses, and the time it takes to recover the investment for the proposed system were set at $4.56 million, $3.12 million, and 1.75 years, respectively. It is worth noting, though, that these figures fall within the range of $6–8 million, $5–7 million, and 5–10 years, respectively, for the currently operational plants. This result indicated that the proposed system provides a robust alternative to the existing cooling-heating cogeneration systems in terms of main output generation and is more economically viable. Also, the novel system gained annually US$3.89 million in energy costs. The conventional exergy analysis results were summarized by forming an exergy flow and loss diagram, namely, the Grassmann diagram. In addition, in this current study, the novel extended exergy flow diagram indicating extended exergy content components, energy carriers of the proposed system, and exergy product rate streams was also proposed and drawn for the proposed system.

Thermodynamic performance evaluation of a novel solar-assisted multi-generation system driven by ammonia-fueled SOFC with anode outlet gas recirculation

The cracking of ammonia to produce hydrogen and nitrogen at high temperatures, without carbon dioxide emissions, has great potential for future energy development. Hence, a novel solar-assisted multi-generation system driven by ammonia-fueled SOFC with anode outlet gas recirculation is proposed and the thermodynamic models are constructed. Under the design conditions, the exergy efficiency, and primary energy saving rate of the novel system in summer are 47.83%, and 51.36%, respectively, while in winter, they are 50.52%, and 52.01%, respectively. Meanwhile, the thermodynamic performances of the new system and two reference systems are compared, in which the reference system 1 isn't coupled with a solar collector, and SOFC adopts an anode outlet gas recirculation layout, the reference system 2 has neither coupled solar collector nor anode outlet gas recirculation arrangement for SOFC. The results demonstrate that the anode outlet gas recirculation layout and coupling solar collectors in SOFC help to reduce the fuel consumption of the system. Moreover, the subsystem's exergy flow diagrams under the design condition reveal the exergy destruction of the components. And the impacts of key factors including SOFC operating temperature, fuel utilization rate, direct normal irradiance, and hydrogen recovery factor are analyzed.

Thermodynamic analysis of biomass and liquefied natural gas complementary CCHP system with liquid air energy storage

Biomass gasification, as a green energy, can be integrated with natural gas combined cooling, heating and power system to realize energy cascade utilization and reduce carbon emissions. This paper proposes a biomass gasification and liquefied natural gas complementary system, including biomass gasifier, gas turbine combined cycle, liquid air energy storage, and absorption chiller, to use more biomass efficiently. The system uses a liquid air energy storage system to absorb excess exhaust from the compressor and solves the compressor's surge when using low calorific value gas. This integration can raise mixed burning ratio of gas to 0.9 without modifying GT. The thermodynamic model of the system is established, and the evaluation indicators are proposed. Based on the rated power of a 270 MW gas turbine, the thermodynamic performances of the system under design conditions are simulated by Aspen Plus. The exergy flow diagrams of the three seasons are obtained. When the ambient temperature changes, the exergy destruction of gas turbine changes the most, and its exergy destruction in winter is 8.3% of the rated power lower than in summer. Besides, the heating exergy destruction of syngas reaches 76.8% for preheating feed water. The performances of the system under off-design conditions are discussed. When the mixed burning ratio of syngas and natural gas increases to 0.9, the input power of liquid air energy storage is 92 MW, and the output power is 53 MW. The electric efficiency of the system with liquid air energy storage increases by 5.6% compared to the system without liquid air energy storage. By selecting the design pressure of liquid air energy storage, the exergy efficiency can be increased by 6.5% when the mixed burning ratio is 0.9.

Energy and exergoeconomic assessments of a renewable hybrid ERC/ORC integrated with solar dryer unit, PEM electrolyzer, and RO desalination subsystem

In this investigation, a zero-dimensional model of a renewable generation system encompassing a solar-geothermal driven Proton Exchange Membrane (PEM) electrolyzer integrated with Organic Rankine Cycle (ORC), Ejector Refrigeration Cycle (ERC) and Reverse osmosis (RO) unit is expressed with respect to energetic, exergetic, economic, and exergoeconomic points of view. Cooling and heating energies, electricity, distilled water, Hydrogen (H2), Oxygen (O2) are the key products of the mentioned system. In order to acquire the influences of the solar collector numbers, area ratio, and pressure drop of the ejector and working fluid of solar collectors on the efficiency of the hybrid unit, a set of equations were coded in MATLAB and Engineering Equation Solver (EES). The exergy destruction rate, exergy efficiency, and exergy destruction ratio of each subsystem and exergy flow diagram of all subsystems were evaluated in this study. Afterward, the results of the sensitivity analysis were used for multi-criteria optimization in three various layouts that the LINMAP as well as the fuzzy TOPSIS decision makings and Gray Wolf Optimizer (GWO), are considered to get the optimal result. The results have indicated that the main variables analyzed are more affected by the variation in the number of the flat plate solar collector. Besides, in the second optimization scenario, the TOPSIS selects the optimal solution of exergy efficiency and unit exergy cost of the product of 3% and 19.77 $/Gj, while the LINMAP selects 3.001% and 19.80 $/Gj point.

A novel nitrogen pipeline system for recycling pressure energy: System model and energy efficiency economic analysis

• Developed a novel nitrogen system with pressure energy recovery. • Reduced the energy consumption of compression by recovering the cold energy. • The exergy flow diagrams revealed the path of energy-saving and efficiency. • The exergy efficiency of the system increased from 48.92% to 65.78% mostly; • Guide system design by the sensitivity analysis of power generation pressure. The depressurization0 process by throttling causes a large amount of pressure energy loss in the nitrogen delivery process. We propose a novel nitrogen piping system (NNPS) and determine the key technical parameters to recover the pressure energy. The NNPS recovers nitrogen pressure energy for power generation and uses post-expansion cold energy to further reduce feedstock nitrogen temperature and compression energy consumption. We selected an NPS in China as a case study to analyze the performance of the NNPS under various operating conditions through energy, exergy, and economic analysis. In addition, a sensitivity analysis of the pre-expansion pressure was carried out. Results show that when the two throttling processes are replaced by the expansion process, the power generation per unit mass flow rate is 77.37 kW, and the energy consumption per unit mass flow rate of the compressor is reduced by 24.49 kW. Moreover, the energy efficiency and the exergy efficiency are 18.67% and 16.86% higher in NNPS compared with those in the NPS, respectively, with the shortest payback period of 113.2 days. When the expansion outlet pressure is 1.6 MPa, the system is suitable for construction when the pre-expansion pressure is higher than 2.0 MPa.

Control-oriented dynamic modeling and thermodynamic analysis of solid oxide electrolysis system

Solid oxide electrolysis cell (SOEC) is a potential technology for increasing renewable energy penetration by turning excess power into hydrogen-based chemical energy, due to its high efficiency. In light of the intermittency of renewable energy, SOEC has to operate in a dynamic-changing environment. Therefore, dynamic modeling and thermodynamic analysis of solid oxide electrolysis systems are crucial for control design and efficient operation. In order to address various voltage losses, this paper develops a dynamic model of the solid oxide electrolysis system, in which the stack voltage is derived based on the electrochemical mechanism. The stack temperature is described by considering the dynamics of convective and radiative heat transfer between the layers. Dynamics of balance of plant (BOP) are modeled based on the mass and energy conservation laws. The model accuracy is verified by the polarization curve under different temperatures. The effects of temperature and current density on the electrolytic voltage are discussed. Three different operation modes (endothermic, thermoneutral and exothermic) are discussed in terms of different current density regions, where the balance between the electrochemical loss and reaction heat consumption varies. Steady-state energy and exergy flow diagrams are used to compare the energy consumption of different components in terms of different inlet temperatures, aiming to determine the optimal conditions with maximum system efficiency. The electrolyzer is revealed as the component with the highest energy consumption and exergy destruction. Dynamic simulation of the stack temperature is carried out in response to various control inputs and disturbances. Dynamic simulation exhibits the response rapidity of variables, strong couplings and different variation trends (monotone, overshoot or initial inverse response), due to the different time scales of electrochemical reaction, gas flow and heat transfer. This study lays a solid foundation for system optimization and dynamic control design.

Thermo-economic appraisal and operating fluid selection of geothermal-driven ORC configurations integrated with PEM electrolyzer

In this paper, a thermoeconomic layout of a renewable production unit embracing a geothermal-based proton exchange membrane (PEM) electrolyzer integrated with the organic Rankine cycle (ORC) is expressed with respect to exergetic, energetic, and exergoeconomic points of view. First, some probable amendments to the base ORC plant design are here poked and collated to boost the ORC recovery efficiency; ORC systems with the internal heat exchanger (IHE), open feed organic fluid heater (OFOH), closed feed organic fluid heater (CFOH), and a combination of IHE-CFOH is assessed. The exergy destruction rate, net present value, exergy destruction ratio, and exergy flow diagram of all ORCs are evaluated. Afterward, the best configuration with seven various ORC operating fluids is scrutinized by optimization of its NPV, cost rate, exergy efficiency, and hydrogen production rate using LINMAP, TOPSIS, and Shannon Entropy, as well as the VIKOR decision makings, and Gray Wolf Optimizer. The results have indicated that the optimum payback period is 5.07 years, and total destruction is 599.13 kW can be obtained with ORC/IHE-PEM operated with R113. Moreover, the optimal condition reveals the optimum cost rate, hydrogen production rate, and exergy efficiency of 26.32 $/hr, 4.202 kg/h, and 40.66%, respectively.

An Application of CO₂ as a Refrigerant for Medium Temperature Heat Pumps

This paper presents the energetic and exergetic analysis of a transcritical carbon dioxide based heat pump cycle for heating. Recycled water (tw=25…40 °C) of food production enterprises is taken into account as a source of low potential heat. The theoretical and real CO₂ trans-critical cycles were analysed. Parameters, which characterize cycles from energy and exergy point of view were obtained. The exergy flow diagram (Grassmann diagram) shows that all the components except the internal heat exchanger contribute significantly to the irreversibilities of the system

Optimization of Thermal Conditions of Heat Recovery Boilers with Regenerative Heating in the High-Temperature Section of Isoamylene Dehydrogenation

Improving the efficiency of use of energy resources at large-capacity energy-consuming enterprises in the petrochemical industry in conditions of high internal and external competition is the priority for the development of the fuel and energy industry. This is confirmed by various legislative acts, including the energy strategy of the Russian Federation for the period up to 2035. This research focuses on a high-temperature section of dehydrogenation of isoamylenes into isoprene, the production of which relates (isoprene production relates to large petrochemical enterprises that consume a huge amount of energy resources) to large-capacity energy-consuming industries. To increase the thermodynamic efficiency of the research object, regenerative feedwater heating for heat recovery boilers is proposed due to deeper cooling of fuel and contact gas (the term "contact gas" is used in the technological regulations of an isoprene production company), which are secondary thermal energy resources in this technology. In accordance with the industry’s technology regulations, a block diagram of the initial and improved high-temperature section with the indication of material flows (The term "material flow" refers to the type of substances that are used in the high-temperature dehydrogenation stage of isoamylenes) was developed. The balance equations of the section under consideration are provided, and the thermal efficiency and exergy efficiency for systems utilizing fuel and contact gas are determined. The estimated economic effect was determined in physical terms; it was found to be 2008.58 toe/h. An exergy flow diagram is also provided to show how the system utilizes contact gas.

In-Depth Exergoeconomic Analysis as an Effective Tool for the Development of Energy-Efficient Circuit Solutions in Air-Conditioning Systems (for Example, a Membrane Air Dehumidification System for Seed Storage Premises)

The paper presents a method of in-depth exergoeconomic analysis, as well as an example of its application to select the most energy-efficient method of air dehumidification for storing agricultural products, namely pumpkin seeds. Theoretical dependences are presented for determining the exergy components of moist airflow (thermal, humidity and mechanical, as well as full exergy). The formulas and the methodology for determining the exergy efficiency “net", which reflects only the internal thermodynamic transformations of air in the air-conditioning system and the exergy efficiency “gross", taking into account the amount of exergy from external sources are given. For avisual representation of the calculations and analysis of exergy destruction in the air conditioning systems, exergy flow diagrams are constructed. The results of calculations of the costs of processing air in an air conditioning system are presented in the form of streaming accumulative diagrams. Based on the results of analysis and comparison of exergoeconomic costs, a scheme with combined membrane dehumidification of air was selected to ensure the necessary storage conditions. Еxergy efficiency “net" foranair handling unit with combined membrane dehumidification of air is 16 % higher than exergy efficiency “net"for anair handling unit with condensing air drying, and 48 % more than exergy efficiency “net"foran air handling unit with adsorption method of air drying. Еxergy efficiency “gross" for an air handling unit with combined membrane air drying 43.5 % more than exergy efficiency “gross" for an air handling unit with condensing air drying, and 54.6 % more exergy efficiency “gross" for an air handling unit with adsorption air drying. In addition, according to in-depth exergoeconomic analysis, the cost of air treatment in air conditioning systems is halved.

Working-fluid selection and thermoeconomic optimisation of a combined cycle cogeneration dual-loop organic Rankine cycle (ORC) system for solid oxide fuel cell (SOFC) waste-heat recovery

A novel combined-cycle system is proposed for the cogeneration of electricity and cooling, in which a dual-loop organic Rankine cycle (ORC) engine is used for waste-heat recovery from a solid oxide fuel cell system equipped with a gas turbine (SOFC-GT). Electricity is generated by the SOFC, its associated gas turbine, the two ORC turbines and a liquefied natural gas (LNG) turbine; the LNG supply to the fuel cell is also used as the heat sink to the ORC engines and as a cooling medium for domestic applications. The performance of the system with 20 different combinations of ORC working fluids is investigated by multi-objective optimisation of its capital cost rate and exergy efficiency, using an integration of a genetic algorithm and a neural network. The combination of R601 (top cycle) and Ethane (bottom cycle) is proposed for the dual-loop ORC system, due to the satisfaction of the optimisation goals, i.e., an optimal trade-off between efficiency and cost. With these working fluids, the overall system achieves an exergy efficiency of 51.6%, a total electrical power generation of 1040 kW, with the ORC waste-heat recovery system supplying 20.7% of this power, and a cooling capacity of 567 kW. In addition, an economic analysis of the proposed SOFC-GT-ORC system shows that the cost of production of an electrical unit amounts to $33.2perMWh, which is 12.9% and 73.9% lower than the levelized cost of electricity of separate SOFC-GT and SOFC systems, respectively. Exergy flow diagrams are used to determine the flow rate of the exergy and the value of exergy destruction in each component. In the waste-heat recovery system, exergy destruction mainly occurs within theheat exchangers, the highest of which is in the LNG cooling unit followed by the LNG vaporiser and the evaporator of the bottom-cycle ORC system, highlighting the importance of these components’ design in maximising the performance of the overall system.

A thermodynamic performance analysis of the agricultural sector of India

Thermodynamic analysis of Indian agricultural sector for a period of 14 years between 2001-2002 and 2014-2015 has been carried out in order to find the thermal efficiency and irreversible losses with the application of the principles of energy and exergy analysis. The devices such as tractors, power tillers using diesel and irrigation pump-sets using electricity, which consumes major portion of the energy inputs are assumed to be the representative of Indian agricultural sector. It is found that during the study period the overall exergy efficiencies (66.05% to 68.46%) are slightly less than corresponding energy efficiencies (66.09% to 68.47%). The energy and exergy flow diagrams and further improvement potential of this important sector are also presented. The results of this study can be used as guidelines for research and development such as analysing sectoral energy and exergy utilisation, providing measures for energy conservation and policy development.

A STUDY OF FIELD GEOTHERMAL POWER POTENTIAL & THERMODYNAMIC CONCEPTS OF PROSPECTIVE BINARY POWER CYCLE BASED GEOTHERMAL POWER PLANT FOR TATAPANI GEOTHERMAL FIELD.

Tatapani Geothermal field is one of the most promising low-enthalpy geothermal fields in central India, located on Son-Narmada lineament in the state of Chhattisgarh, India. The Tatapani geothermal field geological, geo-chemical & reservoir data has been compiled and analysed for evaluating true power potential & better understanding of the field. The low enthalpy geothermal reservoirs can be utilized for power production using Organic Rankine Cycle (ORC) or binary power cycle. Based on previous research works done, the Tatapani geothermal field has been found to be very prospective and has got huge potential for power generation. The binary power cycle has been studied in detail along with thermodynamic concepts. In addition, similar low enthalpy geothermal power plants (conceptual & existing both) have been thoroughly studied in order to understand the concepts and methodology to perform technical feasibility based on thermodynamic and exergy analysis. The literature review covers the previous works done on Tatapani geothermal field including works on other geothermal fields in India along with previous research works for Thermodynamic & Exergy Analysis carried-out for binary geothermal power plants across the world for similar low enthalpy prospects. The methods of performing thermodynamic and exergy analysis for a potential geothermal power plant has been studied and compared. Exergy analysis highlights the areas of primary exergy destruction at various plant components and can be illustrated in the form of exergy flow diagram. The loss of exergy indicates the potential reasons for the inefficiencies within a process and exergic efficiency as conversion of input heat energy from the brine in to useful work output. The exergic efficiencies can be calculated for each component along with exergy destruction. The detailed study has been conducted in order to gather the knowledge regarding conducting the feasibility of setting up binary geothermal power plant at Tatapani from technical point of view using thermodynamic concepts.

Converting Zubair oil field permanent power generation from single cycle into combined-cycle with plant exergy analysis

The combined-cycle power plant is the effective way to increase power and thermal efficiency which can rise thermal efficiency up to 50% corresponding to low heat value of the fuel (LHV). This study focused on converting Zubair Oil Field Gas turbine (ALSTOM GT13E2) from single cycle into a combined cycle power plant. Models suggestion design have been presented with back-pressure steam turbine by Cycle-Tempo (5.1) thermodynamics simulation program, which presents value diagram and exergy flow diagram both are useful to understanding the thermodynamic performance of complicated systems.The result of exergy analysis explicate that huge amount of exergy loss firstly occurs in gas turbine combustor (about 60% due to high irreversibility), and heat recovery steam generation (HRSG) is the second major exergy loss in combined cycle power plant (about 30%) recently apparatus concepts less than 10% of exergy (like compressors and expanders). Also, in this study explained the effect of changing the ambient temperature on the performance of power plant by using four temperature parameters on the four simulation models at constant compression ratio. The results were the increase in gas turbine temperature inlet led to decrease the net power output of the CCPPs. Thermal and exergy efficiencies increase when ambient temperature increase due to growth turbine inlet temperature but this temperature restricted by creep rupture and thermal fatigue for combustor parts and turbine blades metal. Maximum thermal and exergy efficiencies can be reached to 55.74, 53.28% respectively at worst ambient temperature. The calculation results in this study were compared with two previous studies, with considerable differences in input parameters of the gas turbine and steam turbine also, the types of the gas turbine models. finally, the results showed acceptable agreement.

Thermodynamic analysis of a combined cooling, heating and power system based on solar thermal biomass gasification☆

The objectives of this paper are to propose a novel combined cooling heating and power (CCHP) system based on solar thermal biomass gasification, and to present thermodynamic analyses to effectively improve the utilization of distributed renewable energy sources. By adopting the Engineering Equation Solver software, the thermodynamic models of components were constructed, and the simulation procedures, mainly including the heat transfer of the solar cavity receiver and the biomass gasification, were presented. Based on a 100 kW electricity capacity, the design parameters of the CCHP system were obtained to simulate and discuss the thermodynamic performances and the energy and exergy flow diagrams in the cooling and heating operation modes. The influences of the key variable parameters, including the electric load ratio and the solar direct normal irradiance in the off-design work conditions on the thermodynamic performances, were analyzed and discussed. The simulation results indicate that the CCHP system achieves average energy and exergy efficiencies of 56% and 28%, respectively, and the energy ratio of solar to biomass is approximately 0.19 in the full load operating mode. Compared to the conventional biomass gasification CCHP system without solar energy, the increasing ratio of heating value of product gas based on the solar thermal biomass gasification reaches 55.09%, and the biomass saving ratios are approximately 9.22% and 2.02% in the cooling and heating modes respectively, which indicate that the proposed hybrid system is an effective and feasible method to improve the utilization efficiency of biomass energy.

First- and second-law thermodynamic analyses of a combined natural gas cyclepower plant: Sankey and Grossman diagrams

The natural gas combined cycle power plant is one of the best options for generating electricity due to its use of low carbon fuels, high efficiency, and operational flexibility. These plants consist of a combination of Brayton and Rankine cycles, and investigation of these cycles is performed in this paper. Here the parameters of pressure and temperature used in the calculations are taken from a combined cycle power plant. The net power output of the system at 25 °C ambient temperature and 101.325 kPa pressure was calculated as 45 and 12 MW for Brayton and Rankine cycles, respectively. In addition, Brayton, Rankine, and combined cycle efficiencies were calculated as 37.5%, 27%, and 47.5%, while the exergy efficiencies were determined as 36%, 44%, and 46%, respectively. In the system elements, the most energy was lost in the combustion chamber and the highest exergy efficiency was achieved in the compressor at 95% level. Impacts of an increase in ambient temperature, compressor pressure ratio, and change on turbine inlet temperature were further investigated. Energy (Sankey) and exergy (Grossman) flow diagrams were further drawn based on the analyses obtained from the combined cycle power plants.

THERMAL ANALYSIS OF THE ISCC POWER PLANT IN KURAYMAT, EGYPT

ABSTRACTIntegrated Solar Combined-Cycle (ISCC) technology combines the benefits of solarenergy with the benefits of a combined cycle. The solar resource partially substitutesthe fossil fuel. In this paper, a thermodynamic exergy analysis of the integrated solarcombined cycle power plant in Egypt was implemented. The data is taken from thedesign documentations of the plant as well as the plant records. Exergy-basedperformance analysis based on the second law of thermodynamics overcomes thelimit of studying the system based on the first law of thermodynamics. It assesses themagnitude of exergy destruction in each part of the system. The plant is a 135 MWehybrid power plant composed of a combined cycle and a 20 MWe solar thermal plant.Exergy destruction throughout the plant is quantified and illustrated using an exergyflow diagram. The exergitic efficiency of each component of the ISCC is calculated.The results showed that the overall thermal efficiency and the 2nd law efficiency of theISCC accounted for 32% and 40.8%, respectively. Also, it was revealed that thecombustion chamber and the solar field represent the sites of the highest exergydestruction in the ISCC (34 % and 42.1% respectively). The sources of the exergydestruction in the combustion chamber and the solar field are discussed in order toidentify the possibility to enhance the performance of the components of majorexergy destruction.

Energy and exergy analyses of a solar powered multi-effect cooling cycle

This study aims to assess the thermodynamic performance of a novel solar powered multi-effect cooling cycle through the cascaded utilisation of energy and exergy. The effects of parameters such as: direct normal irradiation (DNI), turbine inlet temperature, turbine back pressure, and evaporator temperature of ERC were ascertained on the energetic and exergetic performance of the cycle. Exergy destruction occurs throughout the plant components is quantified and illustrated using an exergy flow diagram, and compared to the corresponding energy flow diagram. The exergy efficiency of the cycle was significantly less than its corresponding energy efficiency. Computational analysis further revealed that the maximum exergy losses of more than 34% occur in the solar field followed by 7.25% and 6.75% in the components of ARC and CRC, respectively. Percentage of these exergy losses indicates the sites where the efforts should be made to improve the real performance of proposed cooling cycle.

Exergy Analysis of the Optimized MSFD Type of Brackish Water Desalination Process

This paper presents a detailed thermodynamical exergy analysis of an optimized MSF distillation plant based on the latest published thermodynamics properties of water and seawater software of the Massachusetts Institute of Technology by using design and optimized plant operation data. Exergy flow rates are evaluated throughout the plant and the exergy flow diagram is prepared in both cases. The rates of exergy destruction and their percentages are indicated on the diagram so that the locations of each exergy destruction can easily be identified. The study concludes that as a result of an optimization, making the MSFD unit once-through cooling system to recirculating type by using cooling tower system, the unit's exergy destruction pattern changes meaningfully. Besides, in the three exist thermal desalination plants up to 53 percent of feed water, i.e.; 667 m3/h and the same amount of reject water can be conserved. Though, with this modification, the unit steam consumption has been increased up to 13 ton/h, about 50 percent of design. Moreover, the detail of the study showed that the exergy destruction can be reduced more than 39% in the pumps, and 30% in blowdown and around 29% in distillate streams. For brine heater, an enhance as small as 0.37% is also achieved. In the other hand, the rate of destruction of exergy increased around 25% in the cooling process and above 5% in the evaporators.