LNG Cold Energy Research Articles

Design and optimization of LNG cold energy utilization scheme for dual fuel main engine of 37000DWT asphalt ship

ABSTRACT In this paper, taking 37000DWT asphalt ship as the research object, three different comprehensive cold energy utilization schemes are proposed. Through simulation analysis and evaluation of three different schemes, genetic algorithm is used for optimization and comparative analysis. The results show that from the perspective of energy utilization, supply–demand matching and economic benefits, the scheme of using all the cold energy of LNG for power generation is the best among the three schemes. Its exergy efficiency reaches 56.32%, and the net annual interest rate is CNY557,000, and the investment equipment cost is about CNY5.246917 million. It takes about 9.4 years to recover the cost.

A thermoacoustic combined cooling, heating, and power (CCHP) system for waste heat and LNG cold energy recovery

Waste energy recovery is crucial for reducing greenhouse gas emissions and alleviating the increasing demand for central power grids. In the paper, theoretical analyses have been carried out on a novel thermoacoustic combined cooling, heating, and power system for simultaneously recovering waste heat and liquefied natural gas cold energy. The system is designed based on acoustic impedance matching between the thermoacoustic and alternator units for maximizing the overall exergy efficiency. The efficiency, cost savings, and emission reductions of the optimal system are investigated. With cold and waste heat temperatures of 130 K and 500 K, the system achieves an overall exergy efficiency of 24.1%, allowing 78.4 MWh of primary fuel energy reduction, and correspondingly, 30.6 tons of CO2 emissions reduction per year. Investigations are further performed on the system parametric sensitivities. A method for adjusting the alternator external electric impedance is proposed to allow for matching piston displacement within design parameters. Besides, comparisons are made with alternative thermoacoustic cogeneration models. The results show that the proposed system can operate effectively for various supply modes, which is promising for adaptation in different applications. Finally, comparisons are drawn with similar existing technologies and future developments are discussed.

The potential of cold energy extraction from a power plant regasification terminal for cold storage application

Cold storage is a chamber used for food preservation. The food is stored inside the cold storage at a specific temperature and relative humidity to slow down the deterioration process caused by pathogenic organisms. The type of food stored requires specific thermal conditions e.g 0-5 °C with RH of 80-90% for vegetables, 4-5 °C for milk processing, and -25 to -45 °C for quick freezing of fish. Cold energy from the LNG regasification process is a promising option for cold storage application. Normally, prior to supply to industrial users e.g power plants, the LNG is regasified by dissipating its cold energy to another working fluid of vapourizer e.g seawater in the Open Rack Vapourizer (ORV) or ambient air in the Ambient Air Vapourizer (AAV). Recovering this cold energy to cool the cold storage can significantly reduce the energy consumption in the cooling process. Simultaneously, it reduces greenhouse gas emissions. This study aims to investigate the potential of wasted LNG cold energy in a power plant’s regasification terminal, located in Aceh, as a source of energy to cool cold storage. The cooling load of cold storage under four different capacity namely 5, 10, 15, and 20 tons of fish is calculated and compared with the potential cold energy available. This study then concludes the cold storage capacity that meets the available LNG cold energy.

Thermodynamic analysis of a gas turbine inlet air cooling and recovering system in gas turbine and CO2 combined cycle using cold energy from LNG terminal

Research on the CO2 cycle has been conducted in various fields, such as nuclear power plants, centralized solar power plants, coal-fired power plants, waste heat recovery, combined cycle, and LNG cold energy recovery. In contrast to the steam Rankine cycle, the CO2 cycle is able to utilize the sub-zero temperature heat sink using LNG cold energy. Inthis study, a novel configuration is proposed that the gas turbine-carbon dioxide combined cycle power plant (GT-CO2 CCPP) with a gas turbine inlet air cooling (TIAC) and heat recovering (HR) system when using LNG cold energy. The TIAC and HR system cools the gas turbine inlet air using condensate CO2 to enhance the power output while air energy is simultaneously recovered to the CO2 bottoming cycle for additional power output and higher efficiency. To determine the capacity of this type of plant, the most commonly implemented LNG terminal is investigated, and the 62 MW medium-size gas turbine is selected for a simulation case study. The thermal performance potential of the proposed configuration is analyzed and compared to a conventional GT-steam CCPP, a GT- CO2 CCPP without the TIAC and HR system. The results show that the relative power output is enhanced by 14.9% and that the efficiency is improved by 2.1% (1.4%p) compared to the GT- CO2 CCPP without it. Meanwhile, this system enables higher power output and efficiency by 25.4% and 11.5% (6.8%p), respectively, compared to the conventional GT-steam CCPP, and the effect is increased according to the ambient temperature.

Exergetic design and optimisation of LNG cold energy utilisation system for dual-fuel main engine of a container ship

Exergetic design and optimisation of LNG cold energy utilisation system for dual-fuel main engine of a container ship

Exergetic design and optimisation of LNG cold energy utilisation system for dual-fuel main engine of a container ship

In this paper, a 9200 TEU container LNG fuel-powered ship is used as a prototype ship, and combined with the cooling load requirements of on-board cold storage, desalination and air conditioning, a...

A new scheme for large marine vessels LNG cold energy utilization from thermodynamic and thermoeconomic viewpoints

With the implementation of International Maritime Organization's new emission regulations in 2020, it has a huge impact on shipping industry. To meet the strict emission regulations and policies, liquefied natural gas, as a promising fuel, can replace the traditional heavy oil, and effectively and practically act as the main power source of marine engine. When liquefied natural gas is vaporized from −162 °C to room temperature, a large amount of cold energy is released to the outside world. To reuse the cold energy efficiently and economically, a new scheme integrated with organic Rankine cycle, seawater desalination, subzero storage and air-conditioning is proposed through comparison of six solutions. With a series of analysis and comparison, R290, NH3, R32 and R152a are determined as the best working fluids for organic Rankine cycle, subzero storage, seawater desalination and air-conditioning modules, respectively. After optimizing the parameters of the scheme by genetic algorithm, the exergy efficiency, net work and payback period reach 55.91%, 210.3 kW and 4.27 years, respectively, showing excellent thermoeconomic performance. Therefore, the proposed method provides a new idea for cold energy recovery of natural gas engine on ships.

Thermodynamic feasibility evaluation of an innovative salinity gradient solar ponds-based ORC using a zeotropic mixture as working fluid and LNG cold energy

Thermodynamic feasibility evaluation is investigated for a salinity gradient solar pond-based power generation system. A dual-pressure evaporation organic Rankine cycle using the zeotropic mixture as working fluid is employed for power generation. To increase power generation, liquefied natural gas cold energy is used as a heat sink. Furthermore, to reach reliable results, transient analysis is conducted on the overall system. Also, the solar pond walls shading effect as well as heat losses that could not be ignored (i.e., evaporation heat loss from pond surface) is considered in the simulation. The results show that for a system located in Urmia, Iran, the annual average solar pond energy efficiency for the first year is obtained 20%. Different zeotropic mixtures are examined to achieve the optimal thermal performance of the system. It is concluded that the system using R245ca/R236ea with a mass fraction of 0.6/0.4 has the optimal thermal performance among selected zeotropic mixtures. In this case, the values of the system generated power and exergy destruction are obtained 95.67 MJ year−1 m−2 and 133.7 MJ year−1 m−2, respectively, with an energy efficiency of 3.28%.

Energy, exergy, and economic (3E) analysis of an organic Rankine cycle using zeotropic mixtures based on marine engine waste heat and LNG cold energy

In this paper, thermo-economic performance comparisons between zeotropic mixtures and pure fluids are conducted via simulation for a parallel two-stage organic Rankine cycle (PTORC) driven by waste heat from LNG-fueled ship. The exhaust gas and jacket water of the marine engine work as heat sources, and the LNG fuel is considered as heat sink. R1150/R170 and R170/R1270 are employed as the working fluids in the first stage while R600a/R601a and R600/R601 are used in the second stage. The effects of working fluids and pinch point temperature difference (PPTD) on the PTORC performances are studied from the viewpoint of the first and the second law of thermodynamics. It concludes that the zeotropic mixtures do not always exhibit an advantage over the pure fluids. The highest net power of the PTORC is 146.9 kW obtained with R1150-R600a. The results of PPTD indicate that LNG regasification should occur in the first-stage condenser. The maximum energy efficiency and exergy efficiency of the PTORC are 22.09% and 23.28%, respectively. The best economic performances of the PTORC are achieved with R170/R1270 (0.9/0.1, mass fraction)-R600. The total cost, payback period, and levelized energy cost vary in the range of 5.98–8.08 × 105 $, 4.58–5.18 years, and 0.065–0.074 $/kWh, respectively.

Optimal design of organic Rankine cycle recovering LNG cold energy with finite heat exchanger size

An optimization study, under a size constraint, was carried out for an organic Rankine cycle (ORC) combined with an LNG regasification plant for recovering LNG cold energy. Typically, many researchers approached to an optimization problem by assuming pinch point or minimum approach temperature difference. As a different point of view, the size constraint was considered in that resources such as thermal energy and equipment size are limited in a real problem. Given this situation, adequate allocation of finite resources is an important issue for the system to maximize performance. Thus, the aim of this study is to understand how to properly utilize the resources when LNG cold energy and total conductance of heat exchangers are limited. Accordingly, the influences of heat duty allocation, UA allocation, and superheating a turbine’s intake on net power were mainly taken into account. Results indicate that, when total conductance for system design increases, the ORC should take more heat duty and total conductance should be weighted to an evaporator. In most cases, the size of heat exchangers should be weighted in the order of evaporator, condenser, and trim heater, provided that total conductance for system design is sufficiently available.

Cascade utilization of LNG cold energy by integrating cryogenic energy storage, organic Rankine cycle and direct cooling

Utilizing LNG cold energy in different temperature ranges with distinctive approaches is a promising option to achieve a high thermodynamic efficiency. This paper proposed a novel LNG cold energy cascade utilization (CES-ORC-DC-LNG) system by integrating cryogenic energy storage (CES), organic Rankine cycle (ORC), and direct cooling (DC) to recover LNG cold energy in the low, middle, and high temperature ranges, respectively. The optimal components and their respective fractions of the mixed working fluids in ORCs, and other key parameters were simultaneously determined by a simulation-based optimization approach which was developed in this study. Then, comprehensive energetic and exergetic analyses were conducted to compare the proposed system performance with the system in the literature to highlight the superior thermodynamic performance. The results indicated that the net power output of the CES-ORC-DC-LNG system was 103.30 kW, which was 22.48% higher than the base case. The optimal compositions of the mixed working fluids in ORC-1 (ethane: 23.73%, ethylene: 15.01%, R134a: 20.17%, and R152a: 41.09%) and ORC-2 (ethylene: 60.14%, R134a: 38.73%, R1270: 0.54%, and R134a: 0.59%) were distinctive with the net power output of 13.89 and 14.46 kW, respectively. The round trip efficiency of the proposed system was 141.88% with 19% increment compared with the base case. Furthermore, the exergetic efficiency of the CES-ORC-DC-LNG system was 73.92% which was 5.17% higher than the base case. Thus, the CES-ORC-DC-LNG system is an energy efficiency LNG cold energy cascade utilization system and can be a potential technology for large-scale cryogenic energy storage.

Feasibility analysis for intermediated fluid type LNG vaporizers using R32 and R410A considering fluid properties

Abstract LNG vaporizer is widely used all over the world to vaporize LNG by using seawater. An intermediated fluid type vaporizer (IFV) uses intermediated fluid between LNG and heat source to transfer heat, and is enable to utilize LNG cold energy for a cryogenic power generation, and so on. Conventionally propane has been used as an intermediated fluid; however, refrigerants other than propane are recently needed because of the diversified usage environments. In this study, R32 and R410A are selected and their feasibility is discussed in heat transfer aspect. By using a number of unit (NTU) method, prediction of boiling and condensation heat transfer rate in tube bundles was carried out. The prediction demonstrated that those selected refrigerants can increase the vaporization rate with IFV from the base line of propane. From those, feasibility of refrigerant use in IFV was shown.

A novel multi-objective spiral optimization algorithm for an innovative solar/biomass-based multi-generation energy system: 3E analyses, and optimization algorithms comparison

A novel multi-generation energy system is proposed consisting of a solar gas turbine system, multi-effect seawater desalination, LNG cold energy recovery unit, and a double effect absorption chiller. In addition, different working fluids of the ORC system are examined to select the suitable working fluid in terms of global warming potential and exergy efficiency of the system. Subsequently, energy, exergy, and economic (3E) analyses are performed to comprehensively evaluate the energy system. Besides, a parametric study is conducted to assess the effect of the most influential decision variables on the proposed system. Afterward, the novel multi-objective spiral optimization (MOSPO) algorithm is introduced to minimize total cost rate of the system while maximizing the exergy efficiency as the conflicting objective functions. The proposed algorithm is developed to optimize the decision variables effectively. To ascertain the final optimum solution point, three conventional methods i.e. TOPSIS, LINMAP and Shannon’s entropy are implemented. The results revealed that exergy efficiency and total cost rate of the system at the baseline are 60.05%, and 36.75 $/h, respectively. Furthermore, the net power output of the system would be 106.5 kW in addition to 0.7703 kW heating load, 56.01 kW cooling capacity, and 35.74 kg/h fresh water production capacity. The eco-environmental assessment revealed the fact that the proposed renewable-based energy system is capable of avoiding 485 tons CO2 emissions annually, and product cost rate reduction up to 6 $/hr in comparison to coal and natural gas-based energy systems. Besides, the proposed MOSPO algorithm is compared with common optimization methods; accordingly, the conventional algorithms are selected for the comparison including non-dominated sorting genetic algorithm II (NSGA-II), the multiple objective particle swarm optimization (MOPSO) algorithm, the Pareto envelope-based selection algorithm II (PESA-II), and the strength Pareto evolutionary algorithm II (SPEA-II). The comparison results show that the proposed MOSPO algorithm is preferable according to the Taylor Diagrams showing the performance of the algorithms.

Comparative Study and Optimization of CO2 Capture and Storage in LNG-fired Power Plant

In the trends of sustainable development and environmental protection, reducing greenhouse gas emissions and utilizing energy sources are feasible solutions. In this study, Aspen HYSYS-based performance simulations for LNG-fired power plants with CO2 capture and storage using cryogenic and amine technologies were conducted to compare and evaluate. LNG cold energy is employed in liquefied CO2 process. Waste heat from exhaust gas of a gas turbine was powered for steam cycle or stripper column. The results showed that the thermal power generation efficiency of the amine system is lower than that of the cryogenic system, however the excessive gasification of LNG in the MEA system is much lower than that of a cryogenic system. The CO2 mass fraction in recovered liquid of the amine system is also higher than the other one. Multi-objective optimization using genetic algorithm (GA) is then carried out providing a set of optimum solution for investors and operators in balance of the excessive gasification of LNG and CO2 recovery rate.

Performance assessment and optimization of an integrated solid oxide fuel cell-gas turbine cogeneration system

The combined solid oxide fuel cells and gas turbine (SOFC/GT) system is known to be a potential alternative for distributed power generation. In this paper, a novel SOFC/GT based cogeneration system, which integrated a transcritical carbon dioxide cycle (TRCC) with a LNG cold energy utilization system is proposed. A mathematical (zero-dimensional) model is developed to analyze the co-generation system performance from the perspective of thermodynamic (energy and exergy) and economic costs. The main parameters of the system are chosen to analyze their effects on thermodynamic performance. The results show that the current system can achieve 64.40% thermal efficiency and 62.13% exergy efficiency under given conditions, and can further improve efficiency through parameter optimization. Finally, the multi-objective optimization program using NSGA-II (Non-dominated Sorting Genetic Algorithm II) is used to obtain the optimal value of the system design parameters. In the multi-objective analysis, the thermodynamic efficiency and economic cost of the system are considered as objective functions. The optimization results show that the final optimized design selected from the Pareto front can achieve 63.08% thermal efficiency and 61.10% exergy efficiency, respectively.

Advanced exergy analysis of an integrated energy storage system based on transcritical CO2 energy storage and Organic Rankine Cycle

In this paper, an integrated energy storage system based on transcritical CO2 energy storage and Organic Rankine Cycle (ORC) is proposed. The working fluid of ORC cycle is R290 and the cold energy of LNG is utilized as the heat sink. The performance of the system is analyzed using conventional and advanced exergy analyses. The conventional exergy analysis quantifies the exergy destruction of each component independently and showed the exergy destruction of LRHE was the largest. The advanced exergy analysis considers the interconnections among the components of the system and the technical limitations of each component, which can reveal more valuable information. The results showed that the R290-Thermal oil heat exchanger had the greatest potential for improvement due to the largest avoidable exergy destruction rate of 171.679 kW. The unavoidable exergy destruction rate of the LNG-R290 heat exchanger was the largest, sharing 35.66% of total unavoidable exergy destruction. A comparison between the results of the two analysis methods showed the advanced exergy analysis gave more reasonable suggestions in terms of system optimization. Besides, the system exergy efficiency was 34.62% under real condition and the theoretical maximum for unavoidable condition was 43.48%, meaning great potential for the improvement of system performance.

Construction and Analysis of LNG Cold Energy Utilization System

The theme of this research is the intermediate fluid vaporizer (IFV) gasification system for an offshore liquefied natural gas floating storage regasification unit (LNG-FSRU). Based on reducing the loss of heat exchange and improve the cold energy utilization, an LNG cold energy utilization system combined with Rankine cycle power generation and desalination is proposed. On this basis, six different schemes of working medium combination are simulated and analyzed, and the optimal scheme of working medium combination is found. The results show that the net output power of the system is 5591 kw, and the system exergy efficiency is 30.38%. The annual economic benefit is CNY 39.4 million.

LNG 냉열과 재생 유기 랭킨 사이클을 이용한 복합 사이클의 성능 특성 해석

LNG 냉열과 재생 유기 랭킨 사이클을 이용한 복합 사이클의 성능 특성 해석

MEA/SG capture CO2 in thermal electrochemical co-drive system

The Thermal Electrochemical Co-drive System (TECS) has the advantages of high desorption rate and low energy consumption. However, the fluid flow and capture performance is still unknown in TECS. Thus, a comprehensive experiment and simulation work on TECS is performed to demonstrate the fluid flow and capture performance in a pilot-scale TECS. The reaction kinetics of the electrolyzed MEA-SG solution is discussed. A pilot-scale TECS is set up and gas-liquid two-phase flow model is developed for the TECS. According to the numerical computation and experiment, the gas-liquid two-phase flow field was analyzed under the thermal electrochemical co-drive conditions. The mechanism of CO2 capture was clearly understood. The synergy of thermal desorption and electrochemical desorption was quantified numerically. The results showed that the temperature of TECS was reduced below 333 K and the energy consumption amount was determined at 1.3 G J/t to 2.1 G J/t, which is much lower than the conventional process. LNG cold energy reduced the desorption energy consumption.

Introducing a hybrid renewable energy system for production of power and fresh water using parabolic trough solar collectors and LNG cold energy recovery

In order to solve the water and energy crisis problem, the thermal water desalination and parabolic trough solar collectors are used at the cogeneration plants. In this paper, an integrated structure for cogeneration of fresh water and power has been developed using a multi-stage thermal water desalination system and organic Rankine cycle. In order to supply the input heat, an integrated structure of parabolic trough solar collectors, and to supply the condenser cooling of organic Rankine cycle, the re-gasification operations have been used. This integrated structure is capable of fresh water generation of 3628 kgmol/h and electrical power of 459.9 MW. In this integrated structure, the efficiency of the organic Rankine cycle power plant and gain output ratio of the multi effect desalination system is 12.47% and 2.918, respectively. Exergy analysis has been used to examine the second law of thermodynamics and the quality of the integrated structure. The total exergy efficiency of the integrated structure is 87.11%, and also, the highest share of equipment exergy destruction is related to the heat exchangers and collectors by 50.23% and 38.18%, respectively. In order to simulate the dynamics of the integrated structure, according to the input climatic information of the studied location in Tehran, Iran. Furthermore, decisions are made upon the sensitivity analysis on economic important indicators within an integrated structure.