Generator-absorber Heat Exchange Research Articles

Energy, economic, and environmental evaluation of a GAX-based cross-type absorption-resorption heat pump

Thermally driven absorption heat pump is regarded as one of the most promising methods to efficiently utilize low-grade heat, reduce energy consumption and greenhouse gas emissions. However, there are still limitations when using it at low ambient temperature in cold regions, and its application is limited by their low system performance. In this study, we proposed a novel Generator-absorber heat exchange (GAX) based NH3/H2O cross-type absorption-resorption heat pump driven by waste flue gas, which amalgamates the absorption-resorption and GAX cycles, yielding a dual advantage of diminished heat source temperature and operating pressure requirements. Additionally, it substantively enhances the system's performance by capitalizing on the cross-type solution cycle integration. A mathematical model has been developed and the results have been compared and validated with those reported in the literature. The proposed system is comprehensively studied from the view of energy, exergy, economic and environmental (4E) analysis to determine its advantages and disadvantages. The results reveal that the proposed system achieves a maximum COP of 2.742 under specific operating conditions, which is 82.8% higher than the conventional absorption heat pump (AHP), and 30.57% higher than the conventional GAX-AHP. Besides, the addition of a compressor can significantly enhance the performance of the system at lower driving heat source temperatures. At a PH/PL pair of 1.7/0.47 MPa, the static payback period is 4.113 years, with the heating capacity of 88.51 kW and the supply water temperature of 54.6 °C, showcasing favorable system performance. Furthermore, the total atmospheric pollutant emissions could be reduced by 30,998 kg/year compared to the conventional heating method.

Simulation studies on GAX based absorption cooling and power cycle using a mixture of ammonia-water working fluid and aluminium oxide nano particles

The present work is focused on analyzing the influence of nano material aluminium oxide on the performance of generator absorber heat exchange ammonia-water absorption refrigeration system. Matlab code has been used to simulate the performance of the combined cycle. The effect of refrigeration, absorber and condenser temperatures on the combined cycle performance have been studied. The results of the analysis indicate that the performance of the combined cycle is higher by 15 to 20% when Al2O3 nano particles were added when compared to the same cycle without the addition of nano particles.

Global sensitivity analysis of a generator-absorber heat exchange (GAX) system’s thermal performance with a hybrid energy source: An approach using artificial intelligence models

• Temperature, heat and flow measurements of an experimental GAX cycle. • Evaluation of artificial intelligence (AI) techniques for multivariate modeling. • Artificial neural networks represent the GAX system with the best accuracy. • AI model coupled to the PAWN method for a global sensitivity analysis of GAX cycle. • COP is affected the most by the temperature measured at the generator inlet. Generator-absorber heat exchange (GAX) systems represent a promising alternative to substitute environmentally harmful refrigeration devices based on conventional vapor compression, as long as a proper analysis of thermal performance and the complex interactions of heat transfer that occur into GAX cycle is taken in consideration. In this research, a cooling process based on a GAX system that uses ammonia-water working fluid and a hybrid source (natural gas-solar) is studied to analyze the variables that affect the system’s thermal performance. The work’s novelty is the hybridization between artificial intelligence (AI) modeling and the global sensitivity analysis (GSA) developed with the PAWN method. Experimental data was obtained from a system with a cooling capacity of 10.5 kW (3 Ton), designed to work at heat source temperatures of 200 °C. The measured variables were the temperatures at generator, heat at evaporator, and working fluid volumetric flow. Three AI techniques (artificial neural networks, genetic programming, and support vector machines) were evaluated for modeling the thermodynamic cycle. Results obtained from the PAWN method applied to the artificial neural network, since it was the best AI model, indicates that the operational parameters with a greater impact in the system’s performance are the inlet temperature at the generator (30.7 %) and the heat measured at the evaporator for NH 3 (27.4 %), for the first output COP N H 3 . For the second output COP H 2 O , the inlet temperature at the generator (32.5 %) and the and heat measured at the evaporator for H 2 O (26.7 %), have a greater impact for such output. The proposed IA-GSA methodology contributes to the development of operational decision-making related to instrumentation, operation performance, and corrective and/or preventive maintenance actions of GAX systems. The developed thermal performance model has potential for implementation in embedded systems (smart sensors) as a critical element in control and optimization strategies to improve the performance of these cycles.

Thermodynamic modelling for absorption refrigeration cycles powered by solar energy and a case study for Porto Alegre, Brazil

The objective of this study is to develop explicit thermodynamic models for absorption refrigeration systems. The models include recent advances in calculating thermodynamic properties of ammonia-water system, the parabolic trough solar collector (PTC) model and the storage tank model. The configurations studied are the single-stage cycle (SAR-C) and the generator-absorber heat exchange absorption refrigeration cycle (GAX-C). However, the procedure can be extended to other cycles or to other refrigerant-absorbent pairs. The thermodynamic model was validated with published experimental results. In terms of coefficient of performance (COP), the models of both cycles showed excellent accuracy. The average relative errors were 6.91% and 1.34%, respectively. A parametric study was performed to determine the feasible evaporation temperatures. A critical mass flow ratio was also determined. It was found that higher evaporator temperatures and lower condenser temperatures increased COP. A case study was also conducted for the city of Porto Alegre in the south of Brazil. During the summer and spring, a maximum cooling load of 18.89 kW was reached in December, while the minimum cooling load of 11.31 kW was reached in March. The system is suitable for a commercial office with a peak cooling load between 12 and 16 h.

Deconstruction and reconstruction of heat driven absorption refrigeration and absorption power cycle with 3-D methods

Advanced absorption cycles, such as the generator-absorber heat exchange (GAX) absorption refrigeration cycle and Honigmann power cycle, are not easy to be intuitively expressed in traditional T-s or P-h diagram, due to their complex heat and mass coupling relationship. With 3-dimensions (3D) methods, additional information can be intuitively expressed which can motivate researchers to propose creative and novel advanced absorption cycles with complex internal heat and mass coupling. In this study, a classic high-performance branched GAX (b-GAX) was graphicly analyzed by introducing 3D methods. The b-GAX cycle was deconstructed in 3D space and reconstructed by projecting the cycle to traditional P-T and P-X plates. Implicit parameters like intermediate concentration and deflation ratio were exhibited intuitively. The performance of the system has a better linear correlation with these new parameters than operation parameters. The Honigmann progress was also graphicly expressed with the 3D methods. By extracting implicit parameters, the new method is expected to play a role in helping to understand complex thermodynamic cycles and propose advanced high-performance cycles.

Thermodynamic design, evaluation, and optimization of a novel quadruple generation system combined of a fuel cell, an absorption refrigeration cycle, and an electrolyzer

In this article, a solid oxide fuel cell system is combined with a generator absorber heat exchanger absorption refrigeration cycle and a proton exchange membrane electrolyzer unit to use most of the fuel energy and recover waste heat and material. This quadruple-generation system produces electric power, refrigeration, heating, and hydrogen from natural gas as the primary energy source for the system. The thermodynamic and environmental performances of the system are studied comprehensively to identify the effects of the key operating parameters on the system operation. The results show that as fuel cell current density increases from 2000 to 8000 A/m2; the system energy and exergy efficiencies decrease by nearly 20%, but the unit carbon dioxide emission increases by 30.38%. Also, the energy and exergy efficiencies are maximized, and the unit carbon dioxide emission is minimized at a specified value of fuel utilization factor. Additionally, increasing the steam to carbon ratio has a damaging effect on the system efficiencies but leads to higher unit carbon dioxide emission. Then, the genetic algorithm is applied to optimize the condition, so the highest exergy efficiency is attainable. The optimization results demonstrate that an exergy efficiency as high as 0.6443 is achievable.

Which methane-fueled fuel cell is of superior performance in CCHP applications; solid oxide or molten carbonate?

The employment of safe and efficient energy conversion methods in various industries is of paramount importance. Fuel cell technology is a reliable prime mover for energy systems. In this paper, a comprehensive study is conducted to compare the thermodynamic, exergo-economic, and environmental facets of employing two types of fuel cells, embracing solid oxide fuel cell and molten carbonate fuel cell, as a driver in a trigeneration system producing cooling, heating, and power. The subsystems consist of a heating unit and a generator-absorber heat exchanger for the solid oxide fuel cell-driven system, and two heating processes for the molten carbonate fuel cell-driven system. The comparisons are made for 1 MW power generation by the fuel cells operating at ambient pressure and 0.85 for the fuel utilization factor. Simulation results show that under the baseline design conditions, the energy and exergy efficiencies of the solid oxide fuel cell-driven system are 74.1% and 37.9%, respectively, whilst these efficiencies for the molten carbonate fuel cell-driven system are 78.5% and 52.4%, correspondingly. Additionally, the comparisons reveal that the molten carbonate fuel cell-driven system outperforms the solid oxide fuel cell-driven one in terms of thermodynamic and environmental performances, but it is also more costly.

Thermodynamic and thermoeconomic analyses of a new dual-loop organic Rankine – Generator absorber heat exchanger power and cooling cogeneration system

This study aims to produce power and cooling by applying exhaust heat. To this end, a hybrid dual-loop organic Rankine – Generator absorber exchange cycle is designed and studied. Furthermore, a thermoeconomic analysis is an essential requirement to study the performance of a thermal cycle. For this reason, the thermoeconomic analysis of this cycle is performed. The dual-loop organic Rankine cycle used in the present study has one low-temperature loop and one high-temperature loop in which R143a and Water are used as working fluids, respectively. Also, in the generator absorber exchange refrigeration loop, ammonia-water is applied as a working fluid. In this research, the impact of pressure and temperature of the first evaporator as well as the generator temperature on exergy efficiency, thermal efficiency, total exergy destruction, exergy destruction ratio, net output power, the heat transfer rate of all components, and the coefficient of performance of the Generator absorber exchange section of the hybrid cycle are evaluated. The results indicate that with increasing the temperature of the first evaporator from 620 K to 680 K, the quantities of exergy efficiency, thermal efficiency, total exergy destruction, and net output power increases with the highest increase being 19.96%, 26.54%, 5.67%, and 32%, respectively. The highest exergy destruction ratio happens in the first turbine at the temperature of the first evaporator equal to 620 K, and the pressure of the first evaporator equal to 9 MPa. With increasing the temperature of the generator from 423 K to 448 K, for the generator absorber exchange refrigeration section of the hybrid dual-loop organic Rankine – Generator absorber exchange refrigeration cycle, the coefficient of performance increases by 3.69%. For the system, the exergoeconomic factor indicates that 13.39% cost of the system is relevant to the investment costs and the remaining is related to the cost of exergy destruction.

Seasonal performance assessment of three alternative gas-driven absorption heat pump cycles

When designing a gas driven heat pump, the selection of the cycle impacts both on complexity and efficiency. Among absorption cycles, the nominal efficiency usually increases with complexity. However, heat pumps are required to operate over a wide range of conditions, of different temperatures and capacity. In this research, three alternative cycles, i.e single-effect (SE), generator-absorber heat-exchange (GAX) and vapor-exchange (VX) for a gas-driven air-source ammonia-water absorption heat pump are compared, considering small-scale space heating as target application. For each cycle, both full-load under various temperature conditions and seasonal performances are predicted by means of numerical simulations. Small capacity appliances are usually equipped with fixed geometry restrictors, meaning that the solution mass flow rate is driven by the pressure difference across the associated restrictor valve. This feature is included in the modeling assumption as it affects the temperature of the generator and, ultimately, the performance at the various conditions. At full load, the VX cycle resulted to achieve the highest Gas Utilization Efficiency (GUE), followed by the GAX and SE. The differences among the cycles are higher at low thermal lift conditions, where the GAX effect is achieved in both the GAX and VX cycles, while are limited at high thermal lift. Looking at the seasonal performances, calculated on the basis of the method prescribed in the European standard EN 12309, the differences among the cycles became much narrower, with the Seasonal GUE ranging between 1.427 (SE) and 1.493 (VX). The small differences in terms of seasonal performances are explained considering that, in the prescribed working conditions, the GAX effect is only partially exploited.

Modeling and Analysis of a Solid Oxide Fuel Cell Based Trigeneration System with an Oxygenated Fuel by Using an Exergoeconomic Methodology for Power, Heating and Cooling Production

In the present study, thermo-economic analysis of a combined solid oxide fuel cell (SOFC) with a gas turbine, a generator-absorber heat exchanger (GAX) and heating process heat exchanger for heating, cooling and power production as a tri-generation system is conducted. Also, an external steam reformer is applied to convert methanol as oxygenated fuel to hydrogen for the electrochemical process of the SOFC. The influence of the primary design parameters (anode inlet temperature and current density) on several variables (energy and exergy efficiencies, exergy destruction, SUCP and unit costs of the products) are examined. Results showed that energy efficiency of proposed system was 55% higher than standalone SOFC. It was found that the maximum exergy destructions occurred in fuel and water mixer, after burner and SOFC. Unit cost of cooling was higher than the other products in the proposed system. It was equal to $220.3/GJ at a specific condition, while unit cost of power and heating were $34.22/GJ and $1.24/GJ, respectively. That was because cooling system needed more components than other systems.

Simulation analysis of performance optimization of gas-driven ammonia-water absorption heat pump

The generator-absorber heat exchange ammonia-water absorption heat pump has a relatively high efficiency and the COP is improved by recovering internal heat. In order to resolve the problem that generator-absorber heat exchange effect becomes less obvious or even fails under the working condition of large temperature lift, a novel system is proposed to recover the rectification heat and absorption heat by solution split method. Compared with the method of using total strong solution to recover absorption heat after extracting rectification heat, the method of solution split avoids the problem of high temperature of inlet strong solution of the solution cooled absorber, and improves the internal heat recovery capacity of the system. When using solution split method to recover the rectification heat and absorption heat, the solution split ratio K has an important influence on the system performance. This paper will theoretically study the selection range of the solution split ratio K and the effect of evaporation temperature, cooling water temperature and generation temperature on the optimum split ratio K. Compared to the system that uses the total strong solution to recover the rectification heat and absorption heat, the performance of the novel system is significantly improved, and the novel system performance coefficient can be increased by up to 15.7%.

Thermodynamic, exergoeconomic, and environmental evaluation of a new multi-generation system driven by a molten carbonate fuel cell for production of cooling, heating, electricity, and freshwater

Because of the ever-growing demand for energy in today’s world, new efficient multi-generation systems are much sought after. Analyzing the practicality and performance of such innovative systems, especially ones utilizing novel energy conversion technologies, has been a popular subject among scientists. In this paper, a comprehensive assessment of a novel multi-generation system driven by a molten carbonate fuel cell is presented from thermodynamic, exergoeconomic, and environmental viewpoints. The proposed system consists of a molten carbonate fuel cell for electricity generation, a heating process heat exchanger for superheated steam generation, a generator-absorber heat exchanger cycle for generating cooling load, and a desalination subsystem for producing freshwater. To investigate the performance of the system, the influences of two important parameters, namely current density and fuel cell operating temperature, are studied on the generated cell voltage as well as the production rates of the products, the energy and exergy efficiencies, the cost rate, the cost per unit exergy, and the carbon dioxide emission rate. According to the results, the net electrical power production and the energy and exergy efficiencies of the proposed system are 1439 kW, 79.9%, and 51.9%, respectively. Also, the investment cost rate of the system is 30.4 $/h, which results in the production of the mentioned outputs with a total cost per unit exergy of 21.6 $/GJ. Moreover, the carbon dioxide emission rate of the system is found to be 247 kg/MWh.

Thermo-economic analysis of a novel hybrid multigeneration system based on an integrated triple effect refrigeration system for production of power and refrigeration

Multigeneration systems provide substantial benefits in terms of improving efficiency and economics as well as environmental benefits. In this study, a multigeneration system is proposed for generating power and triple effect refrigeration at different evaporation temperatures. The system hybridizes a 25 MW recuperative Brayton cycle with an organic Rankine cycle (ORC) and an integrated refrigeration system that combines a branched generator–absorber heat exchange (GAX) absorption refrigeration system with a dual-evaporator cascade carbon dioxide-ammonia compression refrigeration system. The exhaust gas from the Brayton cycle is divided into two streams: one is supplied to the generator of the GAX cycle and the remaining is supplied to the ORC for additional power generation. Results show that additional power generation by ORC increases thermal efficiency from 0.394 to 0.510 and reduces the levelized cost of electricity from $75.5/MWh to $64.4/MWh. The integration of GAX cycle and cascade cycle is beneficial from both thermodynamic and economic viewpoints. Due to their integration, the coefficient of performance of the cascade cycle increases substantially from 2.37 to 4.69. Also, the levelized cost of cooling for the production of triple effect refrigeration decreases from $0.08/ton-hr to $0.059/ton-hr. Environmental analysis shows that the development of multigeneration system can lead to avoiding 24,185 tons of CO2 per year. The proposed multigeneration system brings a possibility to efficiently recover the waste energy for additional power generation and refrigeration production at different temperatures. Waste energy recovery by the ORC and GAX cycle as well as the integration of the GAX cycle with a cascade refrigeration cycle provide good potential for cleaner production of all products with improved efficiency, economics and environmental benefit.

Experimental investigation on NH3–H2O generator-absorber heat exchange (GAX) absorption heat pump

Compared with conventional fuel-direct-burning heating systems, heat-driven absorption heat pump has high efficiency. To further improve the heating performance, generator-absorber heat exchange (GAX) absorption heat pump was developed, but its experimental research was not enough. The parameters tested were usually just COP and heating capacity in the existing literature, the variation of some internal parameters were rarely measured and analyzed. Besides, the latent heat exchange between the generator and the absorber could not continue normally under high thermal lift (TCON-TEVA) and low thermal thrust (TGEN-TABS), instead, more sensible heat is transferred, the temperature overlap decreases or even disappears, and the circulation process of GAX cycle approaches to that of single-effect cycle. This phenomenon is named “cycle degradation”, and is crucial to understand the working principle of GAX for optimal design and control. The cycle degradation was only simulated under low evaporation temperature, but has not been analyzed with experimental data, the influence rules of other external operational parameters on the phenomenon are also not clear. Therefore, a prototype of GAX absorption heat pump is built up, many internal and external parameters are measured and used to investigate the cycle degradation and overall performance under different testing conditions. During the experiment, the COP is in the range of 1.185–1.506, the cycle degradation occurs when the “lifting factor (Eq [18])” is lower than 2.3. Moreover, the performance improves with the increase of driving temperature or low-grade heat source temperature, and deteriorates due to the rise of supply water temperature.

Energy and exergy analysis of a modified absorption cycle: A comparative study

Detailed exergy analysis is conducted on a branched generator-absorber heat exchanger (branched GAX) cycle and the system performance is compared to that for the GAX cycle thermodynamically. By considering the physical and chemical exergies, exergy destruction in each component of the system is calculated and its contribution to the overall exergy destruction is revealed. Parametric studies are also performed to investigate the effects on the coefficient of performance (COP) and the exergy efficiency of some design variables. The results indicate better performance for the branched GAX cycle from the viewpoints of energy and exergy efficiencies. The branched GAX system, however, depends strongly on the condenser temperature which can be accounted as a disadvantage. It is observed that the branched GAX gains an advantage of about 14% in the COP and exergy efficiency for the condenser temperature of 30 °C, however, this advantage goes away as the condenser temperature reaches 50 °C. Furthermore, the total exergy destruction in the branched GAX cycle amounts to 5.17 kW, i.e., 10.6% lower than that for the GAX cycle.

Configurations of solar air source absorption heat pump and comparisons with conventional solar heating

A solar air source absorption heat pump (ASAHP) is analyzed to explore the suitable configurations of advanced solar heating systems. A single-effect (SE) and a generator-absorber heat exchange (GAX) ASAHP, driven by a flat-plate collector (FPC), evacuated tube collector (ETC), compound parabolic concentrator (CPC) and parabolic-trough collector (PTC) are modeled. A parametric study and comparative analysis of different solar heating systems indicate that the CPC-SE, PTC-SE, and PTC-GAX are suitable configurations. Comparisons with the conventional direct solar heating (DSH) show that the ETC-DSH performs the best among all the DSH systems, only the PTC-SE and PTC-GAX are advantageous over it under a solar radiation of 800 W/m2. At an ambient temperature of 7 °C, the CPC-SE performs better than the ETC-DSH only when the solar radiation is above 1000 W/m2. The PTC-GAX becomes worse than the PTC-SE if the solar radiation is below 650 W/m2 and even becomes inferior to the ETC-DSH if the solar radiation is below 400 W/m2. Besides, the applicability domain of the CPC-SE is very narrow, the efficiency improving rate (EIR) of the CPC-SE is about 15% under a favorable condition. The PTC-SE and PTC-GAX had a much wider applicability domain, and the maximum EIR value is about 24% and 36%, respectively. Reducing air pollution is very important for the applications of the solar ASAHP systems.

Experimental investigation on a GAX based absorption heat pump driven by hybrid liquefied petroleum gas and solar energy

In this study, we presented a detailed experimental investigation of an air source liquefied petroleum gas (LPG)-solar driven absorption heat pump (LSAHP) using Generator Absorber heat eXchanger (GAX). The GAX absorption heat pump with a nominal heating capacity of 55 kW uses ammonia-water as working pairs and is powered by hybrid energy sources: a 45 m2 parabolic trough solar collector (PTC) and a direct-fired liquefied petrol gas (LPG) burner. The thermal performance of the PTC was characterized with selected on-sun conditions. Results showed that solar thermal efficiency can reach up to 53.55% with direct normal insolation of 450 W/m2 and inlet thermal oil temperature of 191 °C. Three operation modes were identified based on the driven energy sources: (i) LPG-Solar hybrid mode, (ii) Solar only mode, and (iii) LPG only mode. Under the average ambient temperature of 17.52 °C, 20.0 °C, 8.77 °C the averaged COPs of three modes are 1.54 (mode i), 1.63 (mode ii) and 1.20 (mode iii) respectively. Solar energy contributions reached 40.2% and 55.10% in mode i and mode ii separately which demonstrated the feasibility of the coupling of PTC and GAX heat pump to reduce the dependence on fossil fuel. The impact of operation conditions (ambient temperature, inlet hot water temperature, and LP gas flow rate) on the heating capacity and system performance were investigated under steady-state conditions. Results indicated that higher ambient temperature, higher gas flow rate, and lower inlet hot water temperature benefit the heat pump performance, among which the influence of ambient temperature is the greatest. COP reaches 1.47 with 19 °C ambient temperature and 35 °C inlet hot water temperature. It’s worth noting that COP’ achieves 1.82 under the same condition if we exclude the heat loss of flue gas.

Comparison of absorption refrigeration cycles for efficient air-cooled solar cooling

Absorption chiller is a widely used technology owing to its capability to utilize low grade thermal energy including solar thermal energy and waste heat. Yet, most solar absorption cooling systems need cooling tower to dissipate heat rejection into ambient. The use of cooling tower increases both the initial investment and water consumption, which can be improved by air-cooled solar absorption cooling system. In this paper, to give the best absorption cycle options under different conditions, five absorption refrigeration cycles suitable for air-cooled solar cooling including three double lift absorption cycles and two semi-GAX (Generator-Absorber heat eXchange) absorption cycles were compared. Steady-state simulation is carried out. Efficiencies of these cycles were calculated with LiBr-water and water-ammonia working pairs in the scenario of air-cooled solar cooling. Heat source temperatures of 75–100 °C from non-concentrating solar collector and air temperatures of 20–40 °C were considered. Both air-conditioning condition with evaporation temperature of 5 °C and sub-zero condition with −10 °C were discussed. It is found that mass-coupled semi-GAX absorption cycle with ammonia-water is suitable for air-conditioning with higher heat source temperatures, mass-coupled double lift absorption cycle with water-LiBr is suitable for air-conditioning with lower heat source temperature and mass-coupled double lift absorption cycle with ammonia-water is suitable for sub-zero conditions.

Modelling a solar absorption chiller using positive flash to estimate the physical state of streams and theoretical plate concept for the generator

In this paper a general model for the steady state simulation of a solar absorption chiller is proposed. The novelty of this model is to calculate the physical state of all the streams rather than fix them (especially at the outlet of the condenser and evaporator). The thermodynamic properties of the mixture can be calculated by suitable predictive thermodynamic models, hence the working pair can be changed easily. Using this thermodynamic model, a general Positive Flash model is able to describe all the possible states (sub-cooled, super-heated, biphasic) of the various streams which are all considered as multicomponent mixtures. In the positive flash the same set of governing equations is valid for all phase regions. Another originality of the present study is that the generator is modelled as a distillation column, using the theoretical plate concept: MESH equations (Mass balance, Equilibrium, Summation, Heat balance) were written for each stage. Despite the modular structure of the software, a global solution strategy was implemented, using a Newton-Raphson method. This model is successfully compared to an example in the literature which deals with a GAX (Generator-Absorber heat eXchange) configuration absorption chiller using ammonia/water as the working pair.

Effect of recycling on the thermodynamic and thermoeconomic performances of SOFC based on trigeneration systems; A comparative study

In this study, methane fed trigeneration systems producing power, cooling and heating by means of combination of SOFC, generator-absorber heat exchanger (GAX) absorption refrigeration and heat recovery systems are proposed. Accentuating on the gas recycle of anode and cathode of the SOFC stack, performance of four different suggested configurations are compared with each other. Thermodynamic model is developed for the proposed systems using the mass, energy and exergy balance equations. To give information about the viability of the systems, economic point of view is also taken into account. Meanwhile, the comparison is performed through parametric studies in which the effects of anode recycle and cathode recycle on the net electrical power, energy and exergy efficiency as well as on the unit product cost of trigeneration systems are investigated. The results show that the total energy efficiency of the trigeneration system with anode gas recycle (Tri-SOFC-AR) is 82.5% which is almost 6% larger than that of the simple base case system proposed (Tri-SOFC). In addition, results revealed that among the proposed systems, the one in which the anode and cathode gas recycle (Tri-SOFC-ACR) is used shows the highest exegetic and economic performance in comparison with the other configurations.