Double-effect Absorption System Research Articles

Advancing energy transition with novel biomass-solar based multigeneration energy system using hydrogen and storage options for sustainable cities

An integrated energy system is designed to produce various useful products, such as hydrogen, electricity, heat and cooling. This integrated plant utilizes various subsystems; solar power system, biomass energy system, steam Rankine cycle (SRC), Brayton cycle (BC), organic Rankine cycle (ORC), double-effect absorption system (DEAS), reverse osmosis system, and sonohydrogen production unit. The specific energetic, exergetic, economic and environmental impact assessment studies are carried out to evaluate the system's performance and sustainability. The engineering equation solver (EES) is used for these studies. The energy efficiencies for the BC, ORC and SRC are recorded as 29.69 %, 10.49 %, and 30 %, respectively. In regard to exergy efficiency, the BC, ORC and SRC achieve the following: 46.74 %, 62.73 %, and 53.43 %, respectively. Furthermore, the DEAS attains energetic and exergetic COPs of 1.67 and 0.65, respectively. Additionally, the overall system's energy and exergy efficiencies are found to be 37.68 % and 71.25 %, respectively. The results from the thermal energy storage system indicate that the heat production begins at 7:00 a.m., and the charging of the storage unit commences two hours after and continues until 5:00 p.m., in coinciding with the availability of sunlight. The economic analysis demonstrates that with an initial investment of $53.80 million, the integrated multigeneration system achieves a net present value ranging from $6.87 million to $173.4 million across different hydrogen selling prices, from $7000 to $13,000 per ton up to 2054.

A novel thermally integrated high-temperature PEM fuel cell and absorption system for sustainable heating/cooling application

A new configuration of a high-temperature PEM (Proton exchange membrane) fuel cell coupled with a double-effect absorption system is proposed and investigated in detail. The present paper proposes a high-temperature PEM fuel cell energy system operating in dual modes, i.e., (i) as an absorption refrigerator and (ii) as an absorption heat pump. Thermodynamic coupling is carried out to meet the cooling and heating requirements during the summer and winter seasons, respectively. Energy and exergy-based investigations are performed for the proposed integrated system. The thermodynamic results show that the efficiency of the combined system in the chiller mode can be increased to 68.6% for the fuel cell work output of 162 kW. On the other hand, for the heat pump mode, the energy efficiency of 83.46% can be obtained at current density and operating temperature of 0.8 A/cm2 and 150 °C, respectively. The cooling and heating output obtained during the summer and winter seasons are 205.6 kW and 285.5 kW, respectively. A parametric study of the system is carried out for the dual-mode operation from an energy and exergy point of view. For summer and winter seasons, the influence of key operating parameters such as current density, evaporator, and fuel cell temperature on the system performance is presented. It was reported that the evaporator temperature positively affects the system's energy efficiency.

Performance and environmental impact evaluations of a novel multigeneration system with sonic hydrogen production and energy storage options

This article designs and develops a unique system integrated with hydrogen production and energy storage effectively to meet the variable energy demands of residential communities by harnessing both solar and geothermal energies. The system features a synergy of technologies, including a steam Rankine cycle, an ammonia-water-based double-effect absorption system, two organic Rankine cycles, a thermal energy storage, battery and hydrogen storage options, and a sonohydrogen production device. In order to develop a new system for producing cooling, electricity, heat and hydrogen, the present study dives deep into an analysis based on energy and exergy approaches using balance equations. The present system has the ability to generate 0.0016 kg/s of hydrogen, creates a net output of 2177 kW, supplies 4337 kW for heating purposes, and offers 903.8 kW of cooling capacity. In addition, the system's performance was rigorously evaluated, revealing an energy efficiency of 83.28 % and an exergy efficiency of 58.71 %, with energetic and exergetic coefficients of performance (COP) of 1.646 and 0.6215, respectively. Additionally, an environmental impact assessment was conducted, focusing on CO2 emissions to gauge the system's sustainability. This assessment further indicates that the system could potentially avoid the release of 3.351 kg of carbon dioxide per kilowatt-hour into the atmosphere which might have come from conventional systems.

Performance and environmental impact assessments of a newly developed multigeneration system for sustainable communities

Substituting the use of fossil fuels with renewable energy is crucial for sustainable development, and developing these renewable energy-based solutions for multigenerational proposes to cover the communal needs is even more crucial. This particular article proposes a new renewable based multigeneration system that incorporates several subsystems, such as a solar system, a steam Rankine cycle, a Rankine cycle with reheat, a double effect absorption system, and an electrolyzer. The primary goal of this system is to efficiently and sustainably generate electricity, heating and cooling loads as well as hydrogen. This study further focuses on conducting an environmental impact assessment, although it also includes analyses of energy, exergy, and their effects on the system’s performance. The overall energy and exergy efficiencies of the system are determined to be 53.32 % and 48.28 %, respectively. In addition, the environmental assessment shows that the system can prevent the emission of 332.7 kg CO2/ MWh of electricity. These findings strongly indicate that the proposed multigeneration system is not only highly efficient but also environmentally friendly. Moreover, the results presented in this article emphasize on the importance of implementing a sustainable energy system in order to alleviate the impacts of climate change.

Modeling of an Organic Rankine Cycle Integrated into a Double-Effect Absorption System for the Simultaneous Production of Power and Cooling

Climate change is one of the main problems that humanity is currently facing due to carbon dioxide emissions caused by fossil fuel consumption. Organic Rankine cycles may play an important role in reducing these emissions since they can use industrial waste heat or renewable energies. This study presents the proposal and modeling of an organic Rankine cycle integrated into a double-effect absorption cooling system for the simultaneous production of power and cooling. The working fluids utilized were the ammonia–lithium nitrate mixture for the absorption system and benzene, cyclohexane, methanol, and toluene for the organic Rankine cycle. The influence of the primary operating parameters on the system performance was analyzed and discussed in terms of cooling load, turbine power, energy utilization factor, and exergy efficiency for a wide range of operating conditions. It was found that, for all cases, the cooling load was dominant over the turbine power since the minimum cooling load obtained was above 50 kW, while the maximum turbine power was under 12.8 kW. For all the operative conditions analyzed, the highest performance parameters were obtained for benzene, achieving an energy utilization factor of 0.854 and an exergy efficiency as high as 0.3982.

Experimental investigation on heat transfer and pressure drop of brazed plate heat exchanger using LiBr solution

To improve the performance and miniaturization of the absorption system, it is required to use a plate heat exchanger as a solution heat exchanger and to predict its performance accurately. In this study, the thermal performance of solution heat exchangers was investigated under operating conditions of the solution heat exchanger in the double-effect absorption system and new correlations of Nu and Fanning friction factor were developed and compared. As a result, the hot-side Nu of the high-temperature solution heat exchanger was 6.3–23.1, which was higher than that of the low-temperature solution heat exchanger (4.8–20.1). The thermal properties of the LiBr solution depending on the temperature were significantly sensitive. The developed Nu correlation (Nu = 0.273Re0.693Pr1/3) had a high accuracy with experimental results. In addition, the Fanning friction factor correlation was proposed as f = 1.601/Re0.123. The developed Fanning friction factor was lower than in other literature because the Fanning friction factor was affected by geometry parameters (chevron angle, pitch, height, and size).

Numerical investigation and optimization of a proposed heat-driven compression/absorption hybrid refrigeration system combined with a power cycle

On the basis of the energy distribution characteristic of flue gas, a heat-driven compression/absorption hybrid refrigeration (CAHR) system combined with a power cycle is proposed and designed. In the proposed system, a power cycle with NH3/H2O as working fluid is driven by the heat of flue gas to produce mechanical work for the hybrid system. On the basis of the models of the turbine and compressor, the mathematical model of the proposed CAHR system is built up by considering the conservations of mass and energy of working fluids. Then, the validation and energy conservation of the mathematical model are conducted. The total heat conductance of each component is calculated under basic condition. The influences of NH3/H2O mass fraction, turbine outlet pressure, generation temperature, and compression ratio on the operating parameters of the CAHR system are simulated and analyzed in detail. Taking COP as the optimization objective, the above four parameters are optimized. The thermal performances of CAHR system are compared with those of the heat-driven double-effect absorption refrigeration. Comparison results show that the thermal performances of the proposed CAHR system are better than those of the heat-driven double-effect absorption system.

Charging and discharging characteristics of absorption energy storage integrated with a solar driven double-effect absorption chiller for air conditioning applications

The operation of solar driven air conditioning systems is limited to the availability of solar radiation. Consequently, to achieve extended cooling period, energy storage is necessary. This study presents performance evaluation and charging and discharging characteristics of an absorption energy storage coupled with solar driven double-effect water-lithium bromide (H2O-LiBr) absorption system through thermodynamic modeling and simulation. The absorption energy storage stores the solar heat in the form of chemical energy during the day and discharges later for cooling application. The integrated system achieved effective cooling for about fourteen hours on daily basis. The results indicate an average coefficient of performance (COP) of 1.35 for the integrated absorption chiller-storage unit and exergy efficiency of 25%. Furthermore, the overall COP of the integrated solar cooling system is 0.99 and the overall exergy efficiency is 6.8%, while the energy storage density for typical climatic conditions of Dhahran, Saudi Arabia is found to be 444.3 MJ/m3. The energy storage density obtained from the integrated solar driven H2O-LiBr double-effect absorption system is found to be higher by 13–54% compared to other integrated systems based on single-effect configuration.

Ammonia/ionic liquid based double-effect vapor absorption refrigeration cycles driven by waste heat for cooling in fishing vessels

To use high-temperature waste heat generated by diesel engines for onboard refrigeration of fishing vessels, an ammonia-based double-effect vapor absorption refrigeration cycle is proposed. Non-volatile ionic liquids are applied as absorbents in the double-effect absorption system. In comparison to systems using ammonia/water fluid, the complexity of the system can be reduced by preventing the use of rectification sections. In this study, a multi-scale method is implemented to study the proposed system, including molecular simulations (the Monte Carlo method) for computing vapor-liquid equilibrium properties at high temperatures and pressures, thermodynamic modeling of the double-effect absorption cycles, and system evaluations by considering practical integration. The Monte Carlo simulations provide reasonable vapor-liquid equilibrium predictions. 1-butyl-3-methylimidazolium tetrafluoroborate is found to be the best performing candidate among the investigated commercialized ionic liquids. In the proposed cycle, the best working fluid achieves a coefficient of performance of 1.1 at a cooling temperature of −5 °C, which is slightly higher than that obtained with generator-absorber cycles. Integrated with the exhaust gas from diesel engines, the cooling capacity of the system is sufficient to operate two refrigeration seawater plants for most of the engine operating modes in high-latitude areas. Thereby, the carbon emission of onboard refrigeration of the considered fishing vessel could be reduced by 1633.5 tons per year compared to the current practice. Diagrams of vapor pressures and enthalpies of the studied working fluids are provided as appendices.

Sizing Curve for the Design of Thermal Stabilizer of a Diesel Engine Powered Trigeneration System

Abstract Integrating absorption chillers with diesel engine generators makes possible the use of its rejected energy for meeting cooling energy demand. The performance of such an absorption chiller is sensitive to the temperature at its desorber section. In hot water driven double effect absorption system, the temperature of hot water is to be maintained between 170 C and 165 C. A hot water storage tank is therefore proposed to be integrated so as to maintain the water temperature within allowable limits. Sizing of such a hot water storage referred to as a thermal stabilizer is therefore an important objective. One such technique proposed is a sizing curve method based on thermal stability time. A generalized methodology for generating a sizing curve for a cooling load is presented in this paper. The method offers a simplified approach for sizing of thermal stabilizer for a given diesel generator catering to combined power and thermal demands. This sizing methodology is illustrated for a 180kW diesel engine based trigeneration system catering to fluctuating cooling and power loads.

Prediction of energetic and exergetic performance of double-effect absorption system

The solar cooling technology is a promising alternative to the conventional electrical driven air conditioners, and one of the optimum systems is solar double-effect absorption system. The main objective of this research is to predict, analyze and optimize the performance of the double-effect absorption system. Also it is required to predict the coefficient of performance (COP) and exergetic efficiency (ηex) of the system, and to formulate them in equations as functions of the operating parameters of the cycle. A computer program has been developed by EES (Engineering Equation Solver) software to describe the mathematical model of the used absorption system to carry out the energy and exergy analyses, which were used to analyze the thermodynamic performance of the system. By studying the energetic and exergetic performance of the double-effect absorption cycle for evaporator temperature range of 2–10 °C, absorber and condenser temperature range of 28–45 °C, and HPG temperature range of 100–200 °C, two equations, which are functions of the operating temperatures, have been developed to predict the performance of the cycle.

Numerical modelling of high temperature latent heat thermal storage for solar application combining with double-effect H2O/LiBr absorption refrigeration system

Latent Heat Thermal Storage (LHTS) systems can be applied to minimize the discrepancy between energy supply and demand in solar applications. Combining this system with a double-effect H2O/LiBr absorption system could reduce the investment costs for cooling purposes. These systems require generation temperatures higher than 150°C. Phase Change Materials (PCMs) in the desired temperature range have previously not been thoroughly studied and the integration of an LHTS system into this absorption system has not previously been reported. In this paper a numerical investigation was carried out for a shell-and-tube LHTS system, combined with a solar driven H2O/LiBr double-effect absorption system. The numerical model of the LHTS system was coupled with a mathematical model of the absorption system, and the estimation of the cooling demand and the solar energy. The phase change process was numerically solved using the enthalpy method. Hydroquinone was identified as a suitable PCM. Results indicated that for this configuration of the LHTS system, natural convection cannot be neglected in the modelling of the solidification process. With a LHTS system of 12.55m3, it was possible to fulfil the considered 100kW peak cooling demand for the 2400m2 office building without external energy input. The presented work provides guidelines for the thermal performance and design optimization of a hydroquinone based LHTS system for a solar driven H2O/LiBr double-effect absorption system.

Design of a Solar Assisted Absorption Refrigeration System

This paper presents the design of a solar/gas driving double effect LiBr-H2O absorption system. In order to use solar energy more efficiently, a new kind of solar/gas driving double effect LiBr-H2O absorption system is designed. In this system, the high-pressure generator is driven by conventional energy, natural gas, and solar energy together with water vapor generated in the high-pressure generator, which supplies energy to the low-pressure generator for a double effect absorption system. Simulation results illustrate that this kind of system is feasible and economical. Economic evaluation of several systems is also given in this paper in order to get a clear knowledge of the energy consumption of the system.

Solar driven double-effect absorption cycles for sub-zero temperatures

This paper presents a theoretical study of a solar driven double-effect absorption system with ammonia–lithium nitrate for sub-zero evaporation temperatures. The performance of a double-effect parallel flow ammonia based absorption system with lithium nitrate as absorbent is investigated. This includes the determination of the effect of the strong solution distribution on performance. A ratio of 0.65 appears to be the most advantageous. The paper also presents the dynamic performance of a double-effect ammonia–lithium nitrate absorption system driven by solar energy under Mediterranean summer conditions. The solar energy is obtained by horizontal N–S parabolic trough solar collectors because they can deliver high temperatures that are required to drive the double-effect absorption system. Simulations of the solar absorption systems with a hot storage are performed in order to supply the cooling load of a pork slaughterhouse with maximum cooling load of 600 kW.

Simulation of a Double-Effect Absorber Cooling System Operating at Elevated Vapor Recompression Levels

Applications of aqueous lithium bromide (LiBr/water) single-effect absorption chillers are often limited by their inherently low COP. Multiple-effect absorption cycles, which take advantage of higher temperature heat sources to achieve a higher COP, are more expensive and are limited by corrosion effects, which accelerate significantly above 160°C (320°F). Double-effect chillers are not competitive with comparable electric chillers under current market conditions due to their inherent first-cost premium and oversized footprint. Consequently, research to further improve double-effect absorption chillers, resulting in a lower cost per unit of cooling output, is investigated in this study. Simulation studies of a low differential pressure, vapor recompression absorber (VRA), double- effect absorption cycle utilizing aqueous lithium bromide reported in the literature confirm approximately a 7% efficiency (i.e., COP) and a similar capacity improvement over a conventional double-effect cycle operating at comparable temperatures and pressures. The improvement has been attributed to resulting increased refrigerant mass flow rates and a higher solution temperature entering the high stage generator. The VRA cycle is an alternative to a triple-effect absorption cycle. Substituting a compressor for the fan in the VRA cycle results in further COP and capacity improvements, which makes such a cycle more attractive than both conventional double-effect and proposed triple-effect aqueous lithium bromide absorption chillers. In this paper, a reverse series flow, double-effect absorption system employing a VRA unit operating over a wide range of internal pressure differences is investigated. The performance is compared to a conventional double-effect cycle. Since the VRA requires an electric motor, the impact of gas and electric utility rates on the operating costs of double-effect with the VRA unit cycles and conventional double-effect absorption chillers also are compared.

Enhancement of a double-effect absorption cooling system using a vapor recompression absorber

One of the limitations of aqueous lithium bromide (LiBr/Water) single-effect absorption chillers is their inherently low COP and their inability to take advantage of the availability of high temperature heat to achieve higher COPs. Recent efforts to develop triple or even quadruple-effect absorption chillers appear unlikely to find adequate support in the current deregulated utility marketplace because of their first-cost premiums, corrosion problems associated with high temperature operation, and an oversize footprint. Double-effect cycles, on the other hand, are beginning to capture a significant portion of the heat activated cooling marketplace. This study investigates the effect of adding a Vapor Recompression Absorber (VRA) to a double-effect machine. The VRA, which can be retrofitted into an existing or constructed as part of a new double-effect absorption chiller, is an adiabatic component and uses heat released by condensation to evaporate more refrigerant. This causes an increase in the refrigerant flow rate in the refrigerant circuit, increasing the cooling capacity of the system. Hence, a system utilizing a VRA can achieve higher COPs. This paper presents methods to mathematically characterize the VRA and numerical simulations of a double-effect absorption system employing the VRA unit. The performance enhancement is investigated and the benefits in terms of improving COP and capacity are documented. Also, the impact of design parameters is documented.

Thermo-economical analysis between new absorption–ejector hybrid refrigeration system and small double-effect absorption system

The comparisons of coefficient of performance and the cyclic characteristics between the three-pressure absorption–ejector hybrid refrigeration system (AEHRS) and small double-effect absorption refrigeration system are carried out. The thermo-economical analysis models of the two systems in two cases of high-temperature heat resources: waste heat resources and natural gas fuel are presented. The thermo-economical performances of the two systems in two modes of the running hours per year (600 and 1000 h) are calculated and discussed to show the commercial perspective of the AEHRS.

440 吸収冷凍サイクル高効率化に関する研究(省エネルギー(IV))(空気調和・冷凍技術)

It is necessary to use waste heat from thermal engines effectively for promotion of effective use of energy. Although hot water supply, space heating and so on are raised as heat directions, the amount of use is restricted in summer. However, absorption cycle driven by waste heat is useful for that purpose. The purposes of this study are to improve a coefficient of performance (COP) for water / lithium bromide absorption system, and to evaluate the feasibility for use of various waste heat sources. And, the some of results obtained by this study are as follows. (1) Energy analysis in the absorber and generator in which heat transfer and other unit operation exist was performed, and some findings were obtained. (2) In the double-effect absorption cycle, COP and exergy efficiency was calculated and the cycle evaluation was performed. (3) Some of improved cycles for double-effect absorption system were examined to clarify the advantages.

Cycle analysis of air-cooled absorption chiller using a new working solution

A cycle analysis was achieved to predict the characteristics by comprehensive modelling and simulation of an air-cooled, double-effect absorption system using the new H 2O/LiBr+HO(CH 2) 3OH solution. The simulation results showed that the new working fluid may provide the crystallisation limit 8% higher than the conventional H 2O/LiBr solution. With a crystallisation margin of 3 wt%, the optimal solution distribution ratio was found to be in the range of 37–39%. Variation of cooling air inlet temperature had a sensitive effect on the cooling coefficient of performance (COP) and corrosion problem. The simulation of heat exchangers with UA value revealed that the absorber and evaporator were relatively important for an air-cooled system compared with the condenser and the low temperature generator. The effects of cooling air flow rate, circulation weak solution flow rate and chilled water inlet temperature were also examined. The new working fluid may provide a COP approximately 3% higher than the conventional H 2O/LiBr solution in normal conditions of circulation weak solution.