Proposed Trigeneration System Research Articles

Energy, Exergy, Economic, and environmental assessment of a trigeneration system for combined power, cooling, and water desalination system driven by solar energy

Energy efficiency, exergy efficiency & destruction, economic, environmental, and error analysis analyses have been presented for the proposed trigeneration system. The metrics have provided an inclusive understanding of the proposed system's ability to effectively convert energy inputs to useful outputs while minimizing losses and waste. The goal is to optimize the cycle performance and find the most efficient configuration for meeting the Middle East's energy, cooling, and freshwater needs using a sustainable, solar-driven trigeneration system. The study has observed a system's increased energy and exergy efficiencies by 60.34 to 63.27 % and 25.98 to 29.59 % for the direct normal Irradiance (DNI) values varied from 600 W/m2 to 1000 W/m2. The total energy saving accounted by the proposed configuration is 4,453,220 USD/year as compared to the commercial electricity which includes the net energy production, energy saving through ejector and absorption cooling, and cost of water purification (through Reverse Osmosis Plant) in one year. The payback period of the plant mentioned in this is evaluated by 6.66 years. The CO2 mitigation is evaluated by 22,185.24 MT/year and the other pollutants can also be mitigated like SO2 by 40.425 MT/year and NOx by 136.415 MT/year.

Analysis of a novel concentrated solar power and magnetohydrodynamic liquid metal units integrated system with hydrogen production

The engineers are very interested in concentrated solar power (CSP) due to its renewable energy source nature. However, for this technology to grow, it is crucial to integrate efficient, cost-effective subsystems. On the other hand, since liquid metal magnetohydrodynamic (LMMHD) power generation systems can operate at high temperatures of 600 °C–3000 °C, they are ideal for use as a subsystem of a CSP-based plant to improve efficiency. The use of waste heat recovery units is another method of increasing efficiency and preventing exergy losses. Taking these points into consideration, the proposed trigeneration system includes an LMMHD, a CSP, and humidification-dehumidification and proton exchange membrane units to produce power, freshwater, as well as hydrogen, respectively. Performance evaluation of the presented system includes thermodynamic and thermoeconomic considerations. The results show that the presented system produces 11.87 kW of power, 6.1 m3/h of hydrogen, and 860.2 L/h of freshwater with an energy utilization factor of 45.81%, a total exergy efficiency of 4.63%, and a unit cost of 19.57 $/kWh. The receiver is the most destructive component of the system, with 256.9 kW of exergy destruction. Further, the parametric study indicates that it is possible to maximize the energy efficiency of the system by changing the concentration ratio of the receiver.

Thermodynamic, exergoeconomic and exergoenvironmental analyses and optimization of a solid oxide fuel cell-based trigeneration system

This study proposes a trigeneration system based on solid oxide fuel cell (SOFC) for generating power, cooling and heating simultaneously. The system mainly contains a SOFC, a gas turbine (GT), an organic Rankine cycle (ORC), a steam ejector refrigerator (SER) and a heat exchanger. The thermodynamic, exergoeconomic and exergoenvironmental models of proposed trigeneration system are developed, and the effects of design parameters on system performances are analyzed. The results indicate that the system average product cost and environmental impact per unit of exergy increase with SOFC inlet temperature and working pressure, the pinch point temperature difference and evaporating pressure of Generator, while decrease with the current density of fuel cell. Finally, optimization is performed to achieve the optimal exergy-based performance. It is revealed that though the system exergy efficiency is decreased by 7.64% after optimization, the system average product cost and environmental impact per unit of exergy are significantly reduced.

Performance comparison and risk assessment of BIPVT-based trigeneration systems using vapor compression and absorption chillers

A building integrated photovoltaic-thermal (BIPVT) system, which generates both electrical and thermal energy, is an encouraging technique to significantly reduce building energy consumption. This paper compares the thermoelectric performance of two BIPVT-based trigeneration systems using vapor compression and absorption chillers for supplying the cooling load of the building. Dynamic simulation of the system performance using TRNSYS shows that the annual electrical solar fraction of the system is on average 6% higher using an absorption chiller in comparison with using a vapor compression chiller; whereas, the annual thermal solar fraction of the system is 27% lower using absorption chiller than that using vapor compression chiller. It is also found that although the electrical energy generation by the two systems is slightly different, the thermal energy generation of the system using a vapor compression chiller is about 5.5% less than that using an absorption chiller, due to the consumption of more thermal energy of the absorption chiller and thus, better cooling of the photovoltaic panels. The deterministic economic analysis indicates that despite the higher coefficient of performance of the vapor compression chiller, the payback time of the system with the absorption chiller is 4 years lower than that with the vapor compression chiller, in which the hot water generated by the system in warm months is useless. The stochastic economic analysis based on the Monte Carlo algorithm shows that the probability of the net present value of the system with an absorption chiller and a vapor compression chiller is 98.42% and 70.83%, respectively. The probability of the internal rate of return of the system with an absorption chiller and with vapor compression is also 24% and 20%, respectively. All indicators show that using the absorption chiller in the proposed trigeneration system is far less risky than using a vapor compression chiller.

Thermodynamic and Performance Assessment of an Innovative Solar-Assisted Tri-Generation System for Water Desalination, Air-Conditioning, and Power Generation

Abstract-An innovative tri-generation system powered by solar energy for water desalination, air-conditioning, and electrical power production is proposed and investigated numerically in this paper. The system is designed for small and medium-sized buildings in countries that are rich in solar energy but poor in fossil fuels and water resources. The devised system includes a solar system (evacuated tube collectors and thermal energy storage unit), an Organic Rankine Cycle (ORC), a Humidification and Dehumidification (HDH) water desalination system, and a Desiccant Cooling System (DCS). A detailed parametric study of the developed system is carried out for a wide range of operating conditions and design parameters on the system’s productivity and performance parameters. It is found that: (i) The proposed tri-generation system can deliver high electrical power, fresh water, space cooling capacity, and Energy Utilization Factor (EUF) of 104.5kW, 72.37kg/h, 25.48kW, and 0.2643 respectively. In comparison to the basic system, the EUFimp and ASC,sav parameters were enhanced having maximum values of 69.9% and 41.14% respectively. General numerical correlations derived from the numerical data can predict the system productivity and performance parameters within reasonable error.

Design and thermo-economic evaluation of an integrated concentrated solar power – Desalination tri-generation system

In this work, a concentrated solar power (CSP) tri-generation system that is capable of the simultaneous production of steam, power and freshwater is introduced. The abundantly available direct normal irradiance can potentially allow concentrated solar power systems to become major energy contributors in the desalination market. Since CSPs can generate both thermal and electrical energy, they have been found to be excellent candidates for sustainable operation of large scale desalination systems, in the long term. This paper presents a mathematical model in the form of a Mixed-Integer Nonlinear program (MINLP), which involves a tri-generation system for combined steam and power production, primarily using solar energy to operate steam turbines. Moreover, the option of freshwater production using various desalination technology choices, such as reverse osmosis (RO) and multi-stage flashing (MSF), is also accounted for within the model. Hence, the proposed model offers a very convenient and eco-friendly tri-generation route for steam, power and water production. The proposed systematic method was tested using different feedwater salinities, as well as using different product water flowrates, and electricity prices. According to the results obtained, the water production cost (WPC) associated with a water salinity of 25 g/L resulted in a value of 1.83 USD/m3, which is significantly lower than the WPCs obtained at 35 g/L (2.09 USD/m3) and 45 g/L (2.24 USD/m3). Moreover, a large scale tri-generation system with an overall production capacity of 100,000 m3/d of freshwater resulted in a 60% reduction of the attained WPC value, when compared against a small scale system with a production capacity of 10,000 m3/d of freshwater. The option of exporting electrical energy to the grid using the proposed tri-generation system was also investigated, and a sensitivity analysis was conducted by varying the price of electrical energy. The attained breakeven energy prices were 0.74, 0.79 and 0.82 cent/kWh at 25, 35 and 45 g/L of feedwater salinity, respectively.

Development and multiobjective optimization of a novel trigeneration system based on biomass energy

Biomass energy can play a significant role in achieving sustainable energy production goal, as biomass is considered carbon–neutral fuel when observed from standpoint of the lifecycle. In this paper, a novel trigeneration system has been proposed, incorporating a gasification unit, a solid oxide fuel cell unit, an externally fired gas turbine module, a vapour absorption refrigeration unit, and a hot water generation unit. The proposed trigeneration system has been assessed by energy, exergy, economic and environmental analyses. Furthermore, multiobjective optimization of the proposed trigeneration system has been carried out via response surface methodology. The effects of critical decision variables on the performances of the system have been investigated. The desirability test suggests that the individual desirability value is maximum for levelized cost of electricity followed by fuel energy saving ratio, exergy efficiency of the system and environmental benefit. The combined desirability value (0.949) of the responses is also found to be in the higher side. Thus, it can be said that the setting can be useful in obtaining accurate results for all the responses combined. The proposed plant yields the optimum performance at a pressure ratio of 4.49, current density of 3228.67 A/m2, fuel utilization factor of 0.9, and oxygen utilization factor of 0.1. The results indicate that at the optimum operating condition the proposed system can achieve the maximum exergy efficiency and the fuel energy saving of 55.99% and 52.63%, respectively. The optimum values of the levelized cost of electricity and environmental benefit are estimated to be 0.079$/kWh and 39067.5 $/year, respectively.

Novel design for tri-generation cycle with Parabolic Trough Collector: An exergy-economic analysis

In this work, a new design for the tri-generation cycle with solar energy resources using Therminol 66 in its parabolic thermal solar collectors has been proposed. The solar collectors absorb the solar energy and pass that to the Organic Rankine Cycle (ORC) with n-octane, n-pentane, n-hexane, and n-heptane working fluids. Besides, the energy loss of the evaporator of the organic Rankine cycle has been used for producing thermal load and that of condenser has been utilized for the cooling load generation. In this research, the main innovation is the use of an organic Rankin cycle condenser as the energy source of the absorption refrigeration cycle. Also, the effect of different fluids such as n-octane, n-heptane, n-pentane, and n-hexane on the operation of the whole system has been investigated. The validation of the results has been carried out which showed acceptable agreement and confirms the accuracy of the proposed model. The power coefficient and exergy factor of the cycle have been obtained as 32.72 and 23.83%, respectively. Furthermore, the highest exergy destruction of the proposed tri-generation system occurs in the steam generator, the generator of the absorption refrigeration cycle, and turbine of organic Rankine cycle by 14742 KW, 3974 KW and 3374 KW with the exergy destruction percentage of 54%, 15%, and 12%, respectively. In the economic aspect of the proposed system, the highest cost is for the evaporator of the absorption refrigerator system with 69.71 dollars per hour and the second and third highest cost are for HRSG and the turbine with 32.4 and 30.33 dollars per hour which have 41%, 19% and 18% of the total cost of the proposed system, respectively. Also, the results show that the most costs of waste are for the generator, turbine, and SHX heat exchanger which waste 6.639, 5.586 and 4.22 dollars per hour with 34%, 29%, and 22% of the total cost of waste, respectively. Moreover, it can be seen that by increasing the temperature of the solar collector from 200° to 500°, the first-law efficiency decreases from 37.6% to 28.6%, the second-law efficiency decreases from 40.15% to 17.29% and the total cost decreases from 4.78 to 4.77 dollars per Gigajoule.

Thermodynamic and exergoeconomic analyses and optimization of an auxiliary tri-generation system for a ship utilizing exhaust gases from its engine

Utilizing exhaust gases from engines with the goal of heat recovery is recognized as an essential solution to overcome the economic and environmental problems in the energy industry. Hence, the motivation of this study is to design an auxiliary tri-generation system for a ship based on exhaust gases from its engine and implement the smart use technique of the waste heat. Thermodynamic and exergoeconomic analyses are conducted to evaluate the proposed system considering acceptable thermodynamic assumptions. The system consists of a Kalina cycle, an ejector-booster refrigeration cycle, and a humidification dehumidification desalination unit for power, cooling, and freshwater production. A parametric analysis is conducted to illustrate the effect of some design variables on the sum unit cost of products. Also, to achieve the best design of the system, different optimized cases are evaluated based on a genetic algorithm. According to the attained results, employing exhaust gases from a ship’s engine through the proposed tri-generation system enhanced the thermodynamic and cost outcomes. So, this is a cost-effective and clean production solution to improve the design of a ship. Considering the multi-objective optimization, energy and exergy efficiencies and the sum unit cost of products were 81%, 49%, and 78.6 $/GJ, correspondingly.

A complete energetic and exergetic analysis of a solar powered trigeneration system with two novel organic Rankine cycle (ORC) configurations

Present study aims to compare two solar powered trigeneration systems from energetic and exergetic viewpoints. Said systems are consists of three different sub-systems including solar energy (as a prime mover), Organic Rankine Cycle (ORC), and double-effect absorption chiller. In one of the proposed trigeneration systems Internal Heat Exchanger (IHE) has been used in the configuration of ORC (ORC-IHE). However, in the other system the mixture heater has been included in the configuration of ORC to make Regeneration Organic Rankine Cycle (RORC). Difference between these two systems is related to ORC unit so that one of the cycles is associated with an Internal Heat Exchanger (ORC-IHE) and the other is equipped with mixture heater to make Regeneration Organic Rankine Cycle (RORC). Understanding the changes in the behavior of each component or cycle simultaneously can open new horizons which can be taken as the added-value of this research. The thermodynamic simulation of the proposed models was done by EES software. The prime mover of both ORCs is the solar power plant with parabolic through collectors (PTC). Forasmuch including/excluding any component to/from one of sub-systems affects the overall performance of system it is essential to have an elaborate comparison between these two systems with such unique configurations. To this end, the effect of several decisive parameters including turbine inlet pressure (outlet form evaporator) Pave and condenser pressure on the energetic and exergetic efficiency of net power, heating and cooling production of system was explored. Interestingly, it was turned out that the energy and exergy efficiency of ORC-IHE configuration in the proposed trigeneration system outweighs RORC configuration. Results revealed that the overall energy efficiency of the ORC-IHE-based system and RORC-based system are 93.35% and 86.66% respectively. Accordingly, the overall exergy efficiency for ORC-IHE-based system and RORC-based system are 12.69% and 6.641% respectively.

Evaluation and Optimization of the Annual Performance of a Novel Tri-Generation System Driven by Geothermal Brine in Off-Design Conditions

The difference in heating or cooling to power ratio between required demands for district networks and the proposed tri-generation system is the most challenging issue of the system configuration and design. In this work, an adjustable, novel tri-generation system driven by geothermal resources is proposed to supply the thermal energies of a specific district network depending on ambient temperature in Germany. The tri-generation system is a combination of a modified absorption refrigeration cycle and a Kalina cycle using NH3-H2O mixture as a working fluid for the whole tri-generation system. A sensitive analysis of off-design conditions is carried out to study the effect of operational parameters on the system performances prior to optimizing its performance. The simulation show that the system is able to cover required heating and cooling demands. The optimization is applied considering the maximum exergy efficiency (scenario 1) and minimum total exergy destruction rate (scenario 2). The optimization results show that the maximum mean exergy efficiency in scenario 1 is achieved as 44.67% at the expense of 14.52% increase in the total exergy destruction rate in scenario 2. The minimum mean total exergy destruction rate in scenario 2 is calculated as 2980 kW at the expense of 8.32% decrease in the exergy efficiency in scenario 1.

Exergoeconomic analysis of a novel trigeneration system containing supercritical CO2 Brayton cycle, organic Rankine cycle and absorption refrigeration cycle for gas turbine waste heat recovery

Poly-generation system is gaining more attentions recently due to its advantages of the effective promotion on energy utilization efficiency and deceleration of environmental pollution, as well as the security and reliable improvement on power supply. In this study, a novel trigeneration system composed of a gas turbine cycle (GTC), a regenerative supercritical carbon dioxide (sCO2) Brayton cycle, an organic Rankine cycle (ORC), and an absorption refrigeration cycle (ARC), is proposed. The waste heat exhausted from the GTC is firstly absorbed by sCO2 cycle and then utilized by ORC to generate power. The bottoming ARC is driven by the remaining heat to provide cooling capacity, while the hot water is provided by an intercooler in the GTC. The thermodynamic and exergoeconomic analyses are conducted to investigate the trigeneration system performance. Comparative study is carried out to evaluate the effects of ORC with different working fluids on the whole system performance. Besides, the performances of the proposed system are optimized and compared from the first law, second law of thermodynamics, and exergoeconomic viewpoints. Results show that the trigeneration system can generate 40.65 MW net power, 6.02 MW cooling capacity, and the 9.93 MW heating loads, with 20.17% overall exergoeconomic factor after the optimization on exergoeconomic aspect. Component combustion chamber presents the highest exergy destruction rate, while the subsystem GTC has the largest total exergy destruction and the highest total capital cost, successively followed by sCO2 cycle, ORC, and ARC. Compared with system using n-butane case, the total product unit costs increase by 0.27%, 1.09%, and 0.20% for fluids i-butane, n-pentane, and i-pentane cases, respectively, and the exergy efficiencies elevate correspondingly. However, the thermal efficiencies of above three cases decrease by 0.48%, 0.71%, and 1.06%, respectively. Moreover, combustion chamber is always the most important component for cost in the proposed trigeneration system optimized on the thermodynamic and exergoeconomic aspects, as well as the absorber being foremost in the bottoming ARC.

Hydrogen extraction from a new integrated trigeneration system working with zeotropic mixture, using waste heat of a marine diesel engine

Hydrogen can be used for various applications in ships, but two distinctive places are the combustion processes of the marine diesel engine (MDE) or aircrafts fuelled by aircraft carriers (especially, for long-range transportations applications). For this aim, an integrated trigeneration system working with waste heat of the MDE for mainly hydrogen extraction is proposed here. In addition to hydrogen, the devised trigeneration system can produce surplus electricity and cooling at two different temperature levels. Different zeotropic mixtures are used as working fluid and their performance metrics were compared with each other. It is worthy to say that the simulated basic cooling/electricity system is new and is accounted for as another novelty of the present work. A comprehensive modeling of the proposed trigeneration system is achieved from thermodynamics laws viewpoint and results are elaborated in detail. Based upon the results, the maximum refrigeration load and trigeneration energy efficiency are calculated 166.36 kW and 42.46%, respectively, when R142b/Pentane (0.51/0.49) was used. However, to achieve lower overall exergy destruction, Butene/Isopentane (0.35/0.65) was recommended. Also, the highest trigeneration exergy efficiency is associated with Butene/Isopentane (0.35/0.65) by 18.71%, followed by Isobutene/Isopentane (0.34/0.66) by 18.53%. It is found that the auxiliary vapor generator has the highest exergy destruction by 61.5 kW, followed by ejector by 19.5 kW. At last, an intensive parametric study is also presented to propose some solution for performance enhancement of the system based on the thermodynamics parameters.

Thermodynamic, Economic, and Environmental Analyses of a Waste-Fired Trigeneration Plant

The global energy matrix is going to embrace more and more renewable-based combined energy systems. Therefore, multi-generation energy systems, like CHPs (combined heat and power) could be extremely beneficial for such integrated energy systems. Also, the trend is toward 100% sustainable production where both renewable and waste energy sources are of special value. Especially, in Europe, waste incineration has received special attention over the past decades, as not only it is a smart method of waste disposal, but also a measure of cheap and environmentally friendly energy production. This study proposes a municipal waste-driven tri-generation (cold, heat, and power) system and assesses how this solution helps for easier integration of energy sectors and having a more sustainable chain of energy supply. Then, the solution is comprehensively analyzed over thorough thermodynamic, thermoeconomic, and thermoenvironmental investigations. The results of the assessments show that the proposed trigeneration system may effectively operate in any energy systems with simultaneous cold, heat, and power demands. Thermal, exergetic, fuel-to-power, fuel-to-heat, and fuel-to-cold efficiencies are found to be 83.28, 25.69, 23.49, 47.41, and 12.38%, respectively, while the payback period of 6 years is obtained based on the net present method.

Analysis and Assessment of Tower Solar Collector Driven Trigeneration System

Abstract This paper describes the development and performance assessment of a tower solar collector driven integrated system operating in trigeneration mode to generate electricity, heating, and cooling, in a carbon-free manner. The proposed system applies a heliostat-based central receiver unit as a base of solar energy input to drive the steam Rankine cycle which is combined with the process heater and the lithium bromide-water operated absorption chiller. An analysis is performed to monitor the behavior of energy and exergy efficiency at various operating conditions of the proposed trigeneration system. The computed results are authenticated with the reported literature. A comparison is made between the present findings and reported results in the form of exergy efficiency, total exergy destroyed, and energy efficiency. Consideration of process heat and cold along with electricity provides a promising increase in energy efficiency from 15.8% to 64.1% while the exergy efficiency is enhanced from 16.9% to 24.4%. Variation in direct normal irradiations from 600 W/m2 to 1000 W/m2 results in the significant rise of energetic and exergetic outcomes of the proposed trigeneration system. Out of 100% solar exergy supplied to the proposed trigeneration, 24% is generated as the exergetic output, 1.6% is lost to ambient, and the remaining 74.4% is the exergy destroyed in the system components.

A New Integrated Ocean Thermal Energy Conversion-Based Trigeneration System for Sustainable Communities

Abstract One of the main solutions to climate change is to harness energy from renewable and clean resources. A novel ocean thermal energy conversion (OTEC) system is proposed for the production of methanol; cooling and power is developed and energetically analyzed. In this proposed trigeneration system, a two-stage Rankine cycle that operates on the inherent temperature difference along the depth of the ocean is used for power production, along with an electrolytic cation exchange membrane (ECEM) reactor for carbon dioxide and hydrogen production to feed the methanol production system. The carbon dioxide is sourced from the deep cold seawater, where the concentrations are found to be the highest. The proposed system performance is modeled and simulated on the Aspen Plus, where the performance of the proposed system is assessed under various operating conditions. The results of this study shows that the maximum net power output of the cycle is found to be 51.5 GW, with a fixed rate of district cooling of 69.0 GW. The maximum methanol production rate was found to be 1.36 kg/s at the power input of 51.5 GW. The system is tested under three different operation cases, to fully assess its viability. It should be noted that in all three cases district cooling is included as a product of the system. Case 1: ECEM reactor operates at its current efficiency with fuel production, Case 2: ECEM reactor operates at proton exchange membrane (PEM) efficiency, and Case 3: Only power was produced with no fuel. The maximum overall energy efficiency of the cycle was found to be 8.0, 8.6, and 7.3% for Cases 1, 2, and 3, respectively.

Integration of reversible absorption heat pumps in cogeneration systems: Exergy and economic assessment

Polygeneration energy systems in building applications are widely recognized as an effective way to reduce primary energy consumption and greenhouse gas emissions, thanks to high energy efficiencies and optimal integration of different energy technologies and sources. In the present work, the integration of a reversible absorption heat pump and an internal combustion engine in a novel trigeneration system is proposed. The reversible absorption heat pump, which employs a water-ammonia mixture, is driven by the exhaust gas of the engine, and can produce heating and cooling, alternately. The proposed trigeneration system is presented, and the energy services provided under the heating and cooling operating modes are evaluated. A levelized cost of energy analysis is conducted to evaluate the economic viability of the proposed system. Next, a second-law analysis compares its overall exergy efficiency to those of conventional systems. Finally, the novel trigeneration system is implemented in a case study, namely a large office building located in Pisa, Italy. The integrated optimal sizing and operation are evaluated by using a genetic algorithm-based procedure. The findings show that the system integrating reversible absorption heat pump and cogeneration unit provides valuable economic and energy performance. The exergy efficiency of the system can reach 43%, and cost savings of around 5% and 10% are achieved compared to traditional cogeneration and separate-production system, respectively.

Development of a new trigenerational integrated system for dimethyl-ether, electricity and fresh water production

A novel trigeneration integrated system is proposed and analyzed in this paper. The present system utilizes gas turbine exhaust gas for heat recovery and capturing carbon dioxide after expanding in the turbine and generating electricity. Moreover, a Cu-Cl thermochemical cycle is incorporated in the system to produce hydrogen, and a multi-effect desalination is integrated to provide fresh water to the Cu-Cl cycle and for domestic use as well. The present integrated system is modeled and simulated using the Aspen Plus software package for chemical processes and Engineering Equation Solver for the remaining subsystems. Both energy and exergy analyses are performed to study and assess the proposed system through energy and exergy efficiencies. Therefore, the overall energy and exergy efficiencies of the proposed trigeneration system are found to be 39.72% and 55.2% respectively.

Aspects regarding the use of recovered energy for air conditioning

In the paper the authors analyze the possibility of using the energy recovered from combustion gases, for air cooling. The objective is to evaluate the thermal potential of combustion gases from a cogeneration plant with a 3 MW electric power, located in Buzau. The monitoring data for the cogeneration system shows that the average flue gas temperature at the exit to the atmosphere is 125° C and the mass flow rate of the combustion gases is 18351 kg/h. The thermal potential of combustion gases isused for the preparation of hot water at 85°C for the operation of a LiBr-H2O solution absorption plant. Finally, the authors present a comparative study between the classic cooling system using chiller with mechanical vapor compression (VCM) and the absorption plant supplied by recovered energy from the cogeneration system, high lighting the advantage of the proposed trigeneration system.

A novel trigeneration system using geothermal heat source and liquefied natural gas cold energy recovery: Energy, exergy and exergoeconomic analysis

This paper deals with the energy, exergy, and exergoeconomic analysis of a novel trigeneration system working with geothermal heat source and liquefied natural gas (LNG) cold energy recovery as thermal sink. The proposed trigeneration system is constructed based on the absorption refrigeration cycle (ARC). Due to the high ammonia concentration at condenser outlet of ARC, a heat pump system is employed for heating production, while LNG cold energy is used for recovering the latent heat of the basic solution from the condenser as heat source as well as for producing power output. A comprehensive thermodynamic modeling of the proposed system is presented and the performance of the system is investigated based on the following performance criteria: net power output, cooling output, heating output, thermal efficiency, exergy efficiency and sum unit cost of the product (SUCP) of the system. In this respect, the simulation revealed that the net power output, cooling output, heating capacity, thermal efficiency, exergy efficiency and total SUCP of the system can be calculated 405.1 kW, 1109 kW, 35.3 kW, 85.92%, 18.52%, and 68.76 $/GJ, respectively, under the proposed constrain variables. In addition, the irreversibility of each component and overall system are presented showing that condenser accounts for the highest exergy destruction among all components which constitutes around 55.51% of the overall exergy destruction rate of the system. Moreover, a comprehensive parametric study is conducted to investigate the effects of some key parameters on the main performance criteria. It is observed that one can obtain a higher thermal efficiency at high evaporator temperature or at low condenser temperature, heating unit temperature and absorber temperature; while a higher exergy efficiency can be obtained at high evaporator temperature or at low absorber and condenser temperatures. In addition, a lower total cost of product of the system can be obtained at high heating unit and evaporator temperatures or low absorber and condenser temperatures. Moreover, it is found that the overall performance of system can be optimized based on the generator hot pinch point temperature difference as well as geothermal inlet temperature.