Ammonia-water Power Cycle Research Articles

Energy, exergy and economic analysis of ammonia-water power cycle coupled with trans-critical carbon di-oxide cycle

Energy, exergy and economic analysis of ammonia-water power cycle coupled with trans-critical carbon di-oxide cycle

A novel zero-emission process for the co-production of power, natural gas liquid, and carbon dioxide based on shale gas

This paper presents an integrated process with three products, namely carbon dioxide, power, and natural gas liquid, from the pollutant shale gas. The proposed system utilizes all shale gas for product generation, contributing to the zero CO2 footprint. The hydrocarbon recovery is performed through cold energy integration. An Aspen HYSYS code simulates the system to assess the 4E analysis. Results showed that the proposed structure's first and second laws efficiencies are 51.29% and 80.54%, respectively. This process includes natural gas liquids recovery unit, Allam power cycle, steam power cycle, NH3 power cycle, and ammonia-water power cycle. Exergy analysis illustrated that the largest exergy destruction, valued at 392.15 MW (a 52.81% contribution), happens in the absorption power cycle. Among all equipment, the combustion chamber has the highest exergy destruction. The environmental analysis revealed that the proposed process has zero carbon emission and 4866 tons of CO2 is produced. In the natural gas liquid recovery unit, due to the employing separation with a turboexpander, good refrigeration is provided for the shale gas, which results in the maximum hydrocarbon recovery of 4163 barrels/day. Moreover, besides providing all the power requirements of pumps and compressors, the proposed process generates 460.60 MW of power with a production cost of 8.36 $/MWh.

Development of an efficient ammonia-water power cycle through heat exchanger network analysis and artificial neural network

• The heat integration of the reference Kalina cycle is studied. • Increasing the internal heat recovery can improve the thermal performance. • The improvement in COP can be as high as 8.5%. • A thermal relation embedded artificial neural network is proposed. • The generation performance can be increased by at least 25% at small training sets. This paper presents an efficient ammonia-water power cycle based on the basic Kalina cycle. The heat exchanger network analysis (HEN) is applied to identify all the possible heat-saving configurations. There are 13 different cycles proposed, and each is analyzed and optimized under the same working condition. The results show that there exists a saturation region between the cycle complexity and thermal performance. The thermal efficiency of the optimum cycle has been increased by 8.5% compared to that of the reference Kalina cycle under the heat source temperature of 550℃ and cooling temperature of 24.5℃. The artificial neural network (ANN) surrogate model is also provided to alternatively determine the maximum thermal efficiency under the condition that there is sufficient training data available. The results are compared with those obtained from the thermal model within 0.06% to 1.2% differences. The common practices of ANN in the thermal systems are treated as black-box. Ignorance of thermal principles can lead to a misleading result when using the black-box model, especially for the small size of the training set. In this paper, a thermally constrained ANN architecture is proposed by considering the first law of thermodynamics. The results indicate that, as compared to the black-box model, the generalization performance can be increased at least by 25% with the optimum network configuration of 15-6-3-3 for 50 instances in the training set.

Experimental study on medium and low temperature geothermal ammonia power generation system based on vertical tube falling film

China’s geothermal energy resources are mainly low and medium temperature, the process of ammonia solution generation and absorption is introduced to simplify the condensation heat transfer of Karina cycle, and the vertical tube falling film structure is adopted for the generator and absorber in the system, which makes the system more suitable for medium and low temperature geothermal resources. A 5 kW ammonia water power cycle power generation experimental platform based on vertical tube falling film was built. The experimental results show that under typical working conditions, the maximum heat transfer coefficient of generator and absorber can reach 1034 w/(m2 K) and 563 w/(m2 K), respectively, and the maximum output power of the system is 3 kW.

Presenting a power and cascade cooling cycle driven using solar energy and natural gas

A configuration is presented where solar energy is parallel with fossil fuel to steadily supply a combined power and cascade cooling system. The cascade cooling system produces a steady cooling load at shallow temperatures. The variations of solar radiation during a year are considered. The system combines an improved ammonia-water power cycle with an absorption-compression cascade refrigeration system. The exhaust from the power cycle drives the absorption chiller. Working fluids are ammonia-water for absorption and power cycles and R134a for compression chiller. The effects of turbine inlet temperature, the ammonia concentration in the power cycle, boiler pressure, and generator temperature are investigated. Considering the cooling section's exergy efficiency, the generator temperature is optimized at 110.5 °C. The power cycle's boiler pressure and ammonia concentration are optimized using a genetic algorithm for various cooling loads at various turbine inlet temperature values to find the maximum annual exergy efficiency. The results show that, in all investigated cooling loads, the maximum annual exergy efficiency with a mean value of 65.66% happens at the turbine inlet temperature of 210 °C, an average boiler pressure of 58.56 bar, and an average ammonia concentration of 81.16%.

Analysis and optimization on a modified ammonia-water power cycle for more efficient power generation

This paper presented a modified ammonia-water power cycle that is operated at two pressure levels and equipped with two separators and one heater. The internal irreversibilities due to heat transfer can be greatly reduced by well-matched temperature during the heat addition process. In the feasibility study, the suitable selection range of design parameters is firstly decoupled to ensure reasonable results, guarantee convergent results, and consume less calculation time. In the optimization study, the optimization efforts are aimed at maximizing net power. Two reference Kalina cycles are then chosen for comparisons under two scenarios: medium (346 °C) and low (122 °C) heat source temperatures. The results show that the proposed cycle can produce 12% and 8% more power than the reference Kalina cycles due to more vapor flow and increased average temperature entering the turbine. The proposed cycle can be further simplified by eliminating certain internal heat exchangers, which eventually decreases the system complexity. The proposed cycle has a better capability of adaptation to a wider temperature range of heat source conditions while maintaining a better performance.

Simulation and parametric study on a novel modified Kalina cycle

To improve the utilization rate of hot dry rock resources, it is necessary to recover the energy of geothermal tailwater and improve the net output work. An improved ammonia-water power cycle is proposed based on the Kalina cycle. Taking the geothermal parameters of the Husavik Power Plant in Iceland as the prototype (the water temperature of the geothermal well is 122 °C, and the tailwater temperature is 80 °C), the numerical simulation of the modified Kalina cycle is carried out by using Engineering Equation Solver software. The result shows that the net power output of the modified Kalina cycle increases by 10.5% compared to that of the Kalina cycle. In addition, the parametric study shows that the optimal ammonia concentration of the basic solution in the general area is 0.9. The lower the cooling water temperature is, the lower the turbine exhaust pressure and the higher the net power output. When the ammonia concentrations of the basic solution are 0.6, 0.7, 0.8 and 0.9, the optimum pressures are 29 bar, 36 bar, 41 bar and 45 bar, respectively. The results of this study will contribute to the utilization of geothermal energy in hot dry rock.

Comparative exergy, multi-objective optimization, and extended environmental assessment of geothermal combined power and refrigeration systems

In the present work a comparative exergy analysis, multi-objective optimization, as well as extended environmental analysis of a geothermal-based power and refrigeration system, is carried out. Different arrangements with the ammonia-water refrigeration cycle, organic Rankine cycle (ORC), and thermoelectric generator (TEG) are investigated. The current work novelties are the presentation of a novel power-refrigeration system driven by a geothermal source and the employment of TEG units to recover geothermal energy, besides extended environmental assessment. The results of sensitivity analysis indicate that the highest net output work capacity is for the suggested system (configuration 3). Exergy analysis exhibits that in all cases, the absorber has the highest exergy destruction rate and one of the lowest exergy efficiency because it is the first component, which gains the heat from the geothermal source. The suggested system produces 495.2 kW net output power and the highest energy efficiency of 19.42%, which are 131.7 kW, and 3.84% higher than configuration 1(base system). Optimization results represent that in the optimum point, Ẇnet shows about 33.3% improvement compared with the un-optimized condition. It is found that configuration 3 which consists of cogeneration with two loops of ammonia-water power cycle with refrigeration system along with an additional thermoelectric generator for enhanced waste heat recovery has the highest environmental footprints because of multiple components installed that would occupy more space, electricity, materials, and other resources for its construction, operation, maintenance, and end-of-life.

Optimization of an improved power cycle for geothermal applications in Iran

Geothermal heat sources are promising renewable resources of energy. In this paper, a novel ammonia-water power cycle was designed considering the geothermal resources in Iran. This cycle was analyzed and the effects of ammonia fraction and boiler pressure on its performance were investigated. At the first, Sabalan geothermal field with temperature of 456K was studied. For this geothermal source, the effects of various ammonia fractions were perused in the boiler pressure of 25 bar. The results showed that the ammonia concentration of 0.855 led to the best performance. Also, investigating the boiler pressure at the constant concentration (0.855) indicated that the maximum efficiency happened at 35 bar. Based on genetic algorithm, the simultaneous effects of various concentrations and pressures on the performance of the ammonia-water cycle were surveyed and the optimum values were found for Sabalan source. So that, at the source temperature of 456K, the optimum concentration and pressure were obtained 0.85 and 36 bar, respectively. Finally, the optimum conditions for several geothermal source temperatures were presented within a table. Moreover, at the same sources, the presented optimized cycle was compared with other cycles in the literatures. The results indicated that the presented cycle at optimum conditions had higher efficiency.

Thermodynamic analysis of a new ammonia-water power cycle

A new ammonia-water power cycle (AWPC) basing on Kalina cycle is presented in this paper, which supply an effective way for low-moderate temperature geothermal power in China. The​ thermodynamic models of AWPC are established considering of the ratio of power generation as the optimization objective, and the binary cycle systems are analyzed. The theoretical results of AWPC show that there exists the optimum circulation ratio of 4, along with concentration difference of the ammonia-water solution of 12%–13%. And higher concentration of the ammonia-water solution will improve the performance of AWPC, while adding terminal temperature difference of the solution heat exchanger will improve the ratio of power generation.

Parameter analysis of an ammonia-water power cycle with a gravity assisted thermal driven “pump” for low-grade heat recovery

The diaphragm pump is commonly utilized in the small-scale ammonia-water power cycle for pumping the liquid from absorber to evaporator. The electricity consumption and possible leakage of such a pump influence the system efficiency and reliability significantly. In order to find an alternative “pump” with high reliability and low cost, a gravity assisted thermal driven “pump” (GTP), which is consisted of three top-down organized units connecting absorber and evaporator separately, is designed. With the charging and discharging phases, the pressure in each unit fluctuates, and the level of the liquid increases and decreases alternately by the function of gravity. The results of the system show that the net work and thermal efficiency are 10.68 kW and 9.9%, respectively, when the evaporator and absorber are at 140 °C/4000 kPa and 25 °C/800 kPa separately. The optimal net work, thermal efficiency and exergy efficiency are improved by 4.87%, 3.62% and 10.06% respectively compared with the conventional cycle. An application of the GTP power cycle with the capacity of 10 kW driven by the biomass boiler is analyzed, and the results show that the electricity produced by 645 kg biomass pellets can support more than 12 households per day.

Evaluation of the integration of an ammonia-water power cycle in an absorption refrigeration system of an industrial plant

Combination of binary components used for absorption refrigeration systems as ammonia-water can also be applied as working mixture for power generation in a Kalina Cycle, providing an interesting option in the use of energy sources at low temperatures. Using this possibility in a power-cooling cogeneration system, Kalina Cycle (KC) was proposed to be integrated in an ammonia-water absorption refrigeration system (AARS) of 1269 kW of cooling at 219 K, in order to take better advantage of the available energy from a steam generator in an industrial plant, used as a case study. The AARS uses water steam as hot utility, after the expansion in a pressure reducing valve from higher pressure. Applying exergy analysis, it was verified that the combined KC-AARS, besides the power generation, can decrease the exergy destruction in the AARS. For that, due to the very low working temperatures, the AARS involving double absorbers and evaporators, condenser and expansion valves in a complex system and its peculiarities were practically preserved at lower pressure levels, integrating the KC basically in the higher pressure levels, which is a very interesting proposal for existent systems. The results showed the possibility to reduce the exergy destruction in 43.3%, from 1614 to 915.8 kW, and to produce 493 kW of power generation. In addition, increases in the coefficient of performance from 0.256 to 0.376, energy efficiency of refrigeration from 0.297 to 0.360 and exergy efficiency from 0.185 to 0.468 were reached at 4.7 MPa of working pressure.

Thermodynamic analysis and multi-objective optimization of a novel power/cooling cogeneration system for low-grade heat sources

A novel power/cooling cogeneration system based on an ammonia-water power cycle is proposed and investigated. The cooling capacity of the conventional combined system is much improved since an absorption-ejector refrigeration cycle is introduced. Besides the novel combined system could get more high-grade work at the same time obtain amounts of refrigeration due to the unique coupling mode. A mathematical model of the novel system is developed for system simulations under steady-state conditions. The results show that the thermal efficiency and the exergy efficiency are 21.34% and 38.95%, respectively. Exergy analysis shows that the exergy destruction mainly occurs in the recovery heat exchanger, followed by boiler and rectifier, respectively. Parametric study shows that the absorber temperature, the cycle high pressure, the temperature at boiler outlet and the extracting ratio have significant effects on the system performance. In addition, a multi-objective optimization using NSGA-II method is carried out to obtain the final optimums of the proposed system. The optimization results show that the exergy efficiency and the overall capital cost rate are 37.24% and 0.69408 $/h, respectively, and the thermal efficiency versus the overall capital cost rate are found to be 20.99% and 0.73351 $/h.

A modified ammonia-water power cycle using a distillation stage for more efficient power generation

An ammonia-water power cycle with a distillation stage is proposed, two Kalina cycles and one Organic Rankine Cycle (ORC) are selected for comparisons under two scenarios: medium (346 °C) and low (146 °C) heat source temperatures. The optimization efforts are aimed at maximizing net power production for all concerning cycles, the results show that the proposed cycle can produce 9% and 8% more power than the reference Kalina cycles, while a better thermal performance is achieved for thermal efficiency and exergy efficiency. When the proposed cycle compares with ORC, the amount of net power can be produced is improved by 9% and 3%, respectively. On the other hand, the thermal performance of Kalina cycles and ORC are largely relied on the design of internal heat exchangers, requiring relatively larger size of internal heat exchangers. The proposed cycle, however, is much more compact because of less amount of internal heat transfer needed, leading to less irreversibilities. The proposed cycle can be further simplified by using a solution cooled absorber which eventually decreases the system complexity. A parametrical study shows that the proposed cycle has a better capability of adaptation to a wider temperature range of heat source conditions while maintaining a better performance.

Exergy Analysis of a Combined Power and Cooling Cycle

Ammonia-water power cycles are important for efficient utilization of low temperature heat sources such as geothermal, solar, waste heat sources, etc. For some special conditions ammonia-water power cycle is an important and economical option. This paper presents an exergetic analysis of a combined power and cooling cycle that uses ammonia-water mixture as working fluid. Such cycles, use solar or geothermal energy or waste heat energy from a conventional power cycle. Ammonia-water power cycle can be used as independent cycles to provide power output and cooling. For a range (25–55 Bar) of boiler pressure the performance of the combined power and cooling cycle is investigated. The exergy of the boiler is very low compared to its energy. There is a boiling process and a heat transfer process at low temperature, both of which destruct the energy given to the boiler, so that the energy efficiency is low; however the exergy efficiency is higher than the energy efficiency. Increasing the turbine inlet pressure decreases the energy and exergy efficiencies.

Thermal performance of a modified ammonia–water power cycle for reclaiming mid/low-grade waste heat

A modified Kalina cycle was simulated, which is a triple-pressure ammonia–water power cycle adding a preheater and a water-cooling solution cooler to the original loop. The cycle acquires higher power recovery efficiency by realizing proper internal recuperation and suitable temperature-difference in phase change processes to match both heat source and cooling water. The influences of some key parameters on the thermodynamic performance of the cycle were discussed, including the work and basic concentrations of solution, circulation multiple and the turbine inlet temperature. It is shown that the basic concentration should match the work concentration for higher efficiency. Although higher work concentration could be slightly beneficial to cycle efficiency, the work concentration is mainly determined by considering the suitable turbine inlet/back pressure. Besides, this cycle can be used as a cogeneration system of power and sanitary or heating hot water. The calculation example presented finally with the turbine inlet parameters of 300°C/6MPa and the cycle lowest temperature of 30°C shows that the power recovery efficiency reaches 15.87%, which is about 16.6% higher than that of the steam Rankine cycle. And it also provides 50.7°C sanitary water with about a quarter of the total heating load reclaimed.

Theoretical Investigation of a Power Cycle Using Ammonia-Water as Working Fluid

A novel ammonia-water power cycle is proposed, which uses low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heats. An ejector is introduced between the turbine and the absorber. The main emphasis is placed on the energy and exergy analysis to guide the thermodynamic improvement for the cycle; parametric analysis is conducted to investigate the effects of thermodynamic parameters on the cycle performances. The result shows that the thermal efficiency can reach to 5.31% and the exergitic efficiency varies between 13.3% and 24.4% under the given condition. In addition, the generator pressure, the deflation ratio variation and the turbine outlet depressurization made by ejector have significant effects on the performance of the power cycle.

Thermodynamic analysis of ammonia–water power/chilling cogeneration cycle with low-grade waste heat

An ammonia–water absorption cycle for power and chilling output cogeneration from mid/low-grade waste heat was analyzed and optimized, which is a modified Kalina cycle adding an evaporator and a subcooler to realize the chilling effect. The cycle achieves higher efficiency by generating chilling output from proper internal recuperation process without consumption of additional heat resource and by realizing heat transfer with suitable ammonia concentrations for variable phase change processes to match both heat source and cooling water. Analysis of the impact of key parameters for the system on the thermal and exergy efficiencies was carried out. The results show that there are matching basic and work concentration pairs for a higher efficiency. The smaller circulation multiple and greater chilling fraction are favorable to the efficiencies but restricted respectively by heat transfer constraint of recuperator and the demand. The calculation example with the turbine inlet parameters set at 195 °C/2.736 MPa and the cooling water inlet temperature set at 25 °C with chilling fraction of 0.5 shows that the thermal efficiency and exergy efficiency reach up to 16.4% and 48.3%, about 24.24% and 8.16% higher than those of an ammonia–water power cycle under identical condition.

Thermodynamic Performance of Ammonia Water Power Cycle (AWPC)

This paper introduces the ammonia water power cycle and presents the cycle performance criteria such as net power output, net power energy per ton of geothermal water, heat efficiency and heat exchanger area of per net power. The cycle influencing factors such as ammonia concentration, solution circulation ratio and hot water temperature are analyzed. Results show that there is an optimum range of ammonia concentration and solution circulation ratio. The power system exploits a new way for utilizing the mid-low temperature heat resource efficiently.

저온 열원 및 LNG 냉열을 이용하는 복합 발전 사이클의 성능 해석

Power generation cycle using ammonia-water mixture as working fluid has attracted much attention because of its ability to efficiently convert low-temperature heat source into useful work. If an ammonia-water power cycle is combined with a power cycle using liquefied natural gas (LNG), the conversion efficiency could be further improved owing to the cold energy of LNG at <TEX>$-162^{\circ}C$</TEX>. In this work parametric study is carried out on the thermodynamic performance of a power cycle consisted of an ammonia-water Rankine cycle as an upper cycle and a LNG cycle as a bottom cycle. As a driving energy the combined cycle utilizes a low-temperature heat source in the form of sensible heat. The effects on the system performance of the system parameters such as ammonia concentration (<TEX>$x_b$</TEX>), turbine 1 inlet pressure (<TEX>$P_{H_1}$</TEX>) and temperature (<TEX>$T_{H_1}$</TEX>), and condenser outlet temperature (<TEX>$T_{L_1}$</TEX>) are extensively investigated. Calculation results show that thermal efficiency increases with the increase of <TEX>$P_{H_1}$</TEX>, <TEX>$T_{H_1}$</TEX> and the decrease of <TEX>$T_{L_1}$</TEX>, while its dependence on <TEX>$x_b$</TEX> has a downward convex shape. The changes of net work generation with respect to <TEX>$P_{H_1}$</TEX>, <TEX>$T_{H_1}$</TEX>, <TEX>$T_{L_1}$</TEX>, and <TEX>$x_b$</TEX> are roughly linear.