Liquefied Natural Gas Regasification Process Research Articles

A novel designation of LNG solid oxide fuel cells combined system for marine application

This paper presents a pioneering multigeneration system for marine vessel applications, involving the integration of solid oxide fuel cells (SOFCs) fueled by liquefied natural gas (LNG), coupled with LNG cold energy utilization cycles and exhaust gas heat recovery systems. The system comprises a tandem arrangement of organic Rankine cycle (ORC) and trans-critical carbon dioxide cycle (TCO2), specifically engineered to harness the cold energy released during LNG regasification process. The elevated temperature exhaust gases emanating from the SOFC are efficiently recuperated through a series of components including a gas turbine (GT), regenerative, steam Rankine cycle (SRC), and waste heat boiler (WHB). The proton exchange membrane fuel cells (PEMFC) is designed to enhance the overall operational flexibility and responsiveness of the multigeneration system. The Aspen Hysys V12.1 is used to simulate the propose system and numerical method is employed to parameter optimize of system. The first and second laws of thermodynamics are applied to establish the thermodynamics equations and calculated the system performances. The described system is estimated to obtain energy efficiency of 69.32 % and exergy efficiency of 33.85 %. The high-temperature exhaust gas harvesting integrated systems are sufficiently generated 2091.24 kW which accounted 35.49 % of entire power generate. Furthermore, the parametric researches are implemented to examine the influence of current density, β values to the performance indicators of systems. The WHB is designed to generate 1081 kg/h of superheated vapor at 170 °C and 405 kPa for various purposes of seafarers and equipment's onboard ship. The economic feasibility is performed to view the possibility of investment, maintenance cost and payback period for the described system.

Thermo-economic-environmental evaluation of an innovative solar-powered system integrated with LNG regasification process for large-scale hydrogen production and liquefaction

In order to achieve a sustainable energy future, it is of utmost importance to harness solar energy for the production of liquid hydrogen. This undertaking is justified by the significant role that liquid hydrogen plays as a clean and highly efficient fuel source, effectively addressing the pressing concerns regarding greenhouse gas emissions and reducing reliance on conventional fossil fuels. An additional advantage lies in the easy storage and transportation capabilities of liquid hydrogen, making it a viable solution for energy storage across diverse sectors. In this regard, the current research presents a novel solar-powered setup consisting of parabolic trough solar collectors (PTSCs), a sequential organic Rankine cycle (ORC), a liquefied natural gas (LNG) regasification unit, and a module dedicated to the production and subsequent liquefaction of hydrogen. A meticulously crafted MATLAB code is utilized to replicate the operations of the proposed system, facilitating a thorough examination of its energy, exergy, environmental, and economic performance. The proposed system exhibits a net output power of 1.13 MW and possesses the capacity to produce hydrogen at a rate of 34.92 kg/h, featuring a levelized cost of hydrogen (LCOH) of 3.59 $/kg. Additionally, the system encompasses a cooling capability of 192 kW. From an environmental perspective, this configuration contributes to a decrease in carbon dioxide emissions by 255.96 kg/h. After conducting a dynamic analysis with meteorological data, it was determined that the system has the potential to generate an annual hydrogen output of 536.84 tons in San Francisco.

Techno-economic-environmental study and artificial intelligence-assisted optimization of a multigeneration power plant based on a gas turbine cycle along with a hydrogen liquefaction unit

According to the literature, there is a research gap concerning the practical heat recovery in solar-driven systems that have the capability to produce liquid hydrogen. In this study, an innovative combination of dual-loop solar-driven organic Rankine cycle and liquefied natural gas (LNG) heat recovery is designed to produce and liquefy hydrogen. The proposed system includes parabolic trough solar collectors (PTSCs), a Rankine cycle, a dual-loop organic Rankine cycle, LNG regasification process, proton exchange membrane (PEM) electrolyzer, and Claude hydrogen liquefaction cycle. A data-driven method is developed to analyze the system from techno-economic and environmental perspectives. The results show that LNG energy recovery improves the liquefaction work by as much as 7.96 kWh/kgH2. It is also concluded that the optimum compaction pressure range for the liquefaction cycle is 4.67 MPa, which is associated with better results. In these conditions, liquefaction work, liquefaction Coefficient of Performance (COP), and liquefaction exergy efficiency are 164.6 kJ/kg, 0.157 and 17.05%, respectively. To find optimum operating conditions, a supervised learning approach is applied to the developed code and the trained network is optimized using the genetic algorithm (GA). The optimization results reveal that a 10.98 $/h increase in total cost rate causes an 18% improvement in hydrogen production rate.

Conceptual design of floating storage and regasification unit (FSRU) for Eastern Part Indonesia

Liquefied Natural Gas (LNG) can be used as an alternative fuel with environmentally friendly solutions. In general, the domestic distribution of natural gas in LNG is more cost-effective than transporting gas through underwater pipelines considering Indonesia as archipelagic country. According to Indonesia’s Minister of Energy and Mineral Resources Regulation Number 13 of 2020, the government supports converting 52 power plants to LNG. However, the current challenge in the LNG industry is the lack of supporting facilities. Storage and regasification facilities are among the infrastructure that requires optimization. Floating Storage and Regasification Unit (FSRU) are viable options for energy distribution that offer opportunities and competitiveness compared to onshore terminals. Small and medium-scale FSRU can serve as an alternative solution due to their relatively fast, flexible, and affordable development process. Therefore, this research will develop a small-medium FSRU design with a capacity of 60 MW − 70 MW in Eastern Indonesia. FSRU design should consist of four segments including location considerations and environmental conditions, powerplants gas requirements, LNG storage tank sizing and LNG regasification process. Calculations for various supporting FSRU components, seakeeping analysis, loading-offloading processes, 3D modelling and the integration of solar panels were discussed. The results obtained include the principal dimension, technical aspects of FSRU design, and the technology for LNG regasification processes used.

Gas turbine-based system taking advantage of LNG regasification process for multigeneration purposes; Techno-economic-environmental analysis and machine learning optimization

It is viable for engineers to determine how thermodynamic systems can benefit from heat recovery in order to improve efficiency, reduce costs, and lower carbon dioxide emissions. The authors of the study propose a new energy system that incorporates various cycles and units, including gas turbines, Rankine and two organic Rankine cycles, an absorption refrigeration unit, a proton exchange membrane (PEM) electrolyzer, and a liquefied natural gas (LNG) unit. The hydrogen produced is stored and transferred for use as fuel. The system was modeled and optimized using MATLAB programming software, with a parametric study and sensitivity analysis conducted before employing a genetic algorithm optimization to find the most suitable performance conditions. Modifying the compressor's pressure ratio within the range of 6–18 caused a shift in the cooling load, ranging from 45 to 36 MW. Nonetheless, these adjustments in pressure ratio yielded a reduction of 0.4 Cent/kWh in levelized cost of electricity (LCOE) and 0.15 $/kg in levelized cost of hydrogen (LCOH). In the base design mode, the total cost rate is 5715.3 $/h, the exergy efficiency is 39.03%, and the normalized CO2 emissions are 335.89 kg/GJ. However, the optimization results showed a reduced total cost rate of 1884.50 $/h, along with an improved exergy efficiency from 39.03% to 40.32% and a decrease in annual CO2 emissions from 211,000 metric tons to 175,000 metric tons. The implementation of artificial neural networks (ANN) has significantly decreased the time required for optimization from 47 h to just 16 min.

Environmentally friendly utilization of LNG regasification process and geothermal-based dual-loop power cycle for desalinated water and hydrogen production

The global scarcity of fresh water has prompted the development of innovative strategies for establishing affordable and efficient desalination systems that utilize waste heat from industrial processes. This study presents a novel combination of a geothermal-driven dual-loop organic Rankine cycle and liquefied natural gas (LNG) regasification process intended for electricity, desalinated water, and hydrogen production. The integration of diverse energy sources holds the capability to reduce dependence on traditional fossil fuels and promote a more sustainable and diversified energy portfolio, conducive to ecological well-being. In the suggested approach, a thermoelectric generator (TEG) is employed to harness the thermal contrast present between the residual heat of the geothermal process and the cold LNG stream, which reduces irreversibility and increases the system's power output. After examining the effect of key parameters on the system's performance, a data-driven approach is adopted in which the system's performance is predicted based on artificial neural networks (ANNs). According to the results, the primary generated power, desalinated water production rate, total cost rate, and cooling load are 5.15 MW, 127.31 m3/h, 188.22 $/h, and 2.92 MW, respectively. Also, the findings of the financial investigation demonstrate that the electrolysis unit, with an hourly cost rate of 85.2 $, constitutes more than 45 % of the total cost rate. In addition, the optimization of the system is performed in three distinct cases, wherein each case pertains to a different objective. In optimal conditions, the amount of produced desalinated water and the total cost rate are 153.89 m3/h and 153.58 $/h, respectively.

Integrated hydrogen liquefaction process with a dual-pressure organic Rankine cycle-assisted LNG regasification system: Design, comparison, and analysis

Improving the efficiency and reducing the cost of hydrogen liquefaction systems have become a subject of importance nowadays. Through the comparison and analysis of existing processes, a hydrogen liquefaction system that can enhance the utilization efficiency of liquefied natural gas (LNG) cold energy is developed. The system includes a dual-pressure organic Rankine cycle (DORC)-assisted LNG regasification process and improved cascade Joule-Brayton refrigeration cycles. To assess the performance of the proposed process, two forms of ORC and three Brayton refrigeration cycles are compared, respectively. The genetic algorithm is applied to optimize the proposed process. The coefficient of performance, exergy efficiency, and specific energy consumption of the proposed process is 0.20, 46.9%, and 6.61 kWh/kgLH2, respectively. Owing to the efficient utilization of LNG cold energy, the power output of the DORC is 16.2% higher than that of a regular ORC. Furthermore, the improved cryo-cooling process exhibits a significant performance enhancement. Compared to two existing processes, the UA value of the heat exchangers in the proposed cryo-cooling process is reduced by 47.6% and 8.3%, respectively, and the required mass flow rate of helium is reduced by 45.3% and 8.6%, respectively. Moreover, the exergy analysis performed on the system indicates that the exergy utilization rate of the hydrogen pre-cooling process is 80.2%, while that of the cryo-cooling process is only 48.7%.

Reviewing the impact of LNG technology advancements on global energy markets

Rapid technological advancements in Liquefied Natural Gas (LNG) have catalyzed a transformative shift in global energy markets. This review delves into the profound impact of LNG technology advancements, exploring their multifaceted consequences on the dynamics of the energy landscape. The evolution of LNG technologies, spanning liquefaction, transportation, and regasification processes, has ushered in a new era of energy accessibility, sustainability, and market competitiveness. The burgeoning role of LNG as a cleaner and more versatile fuel source is examined against the backdrop of global efforts to address climate change. Environmental considerations, carbon reduction goals, and the burgeoning demand for cleaner energy sources are driving the increasing adoption of LNG in the global energy transition. Government initiatives supporting LNG adoption and renewable energy policies influencing its utilization are dissected to comprehend the intricate policy factors shaping global LNG consumption. Economic drivers, including cost competitiveness and market dynamics, play a pivotal role in shaping the global LNG landscape. The review assesses the economic growth and industrial demand for LNG, providing insights into the intricate relationship between economic factors and the surge in LNG consumption. Additionally, the expansion of global LNG production capacity, exploration of unconventional gas resources, and geopolitical influences on LNG supply patterns are thoroughly scrutinized to provide a comprehensive understanding of the forces steering LNG trade dynamics. The regional dynamics in LNG trade are elucidated with a focus on major economies such as Asia-Pacific, Europe, and North America. The rising demand from these regions, coupled with infrastructure developments and regulatory frameworks, underscores the intricate interplay of factors shaping LNG trade dynamics on a regional scale. Furthermore, the review delves into the geopolitical implications of recent events on LNG markets, scrutinizing trade agreements and geopolitical risks to provide a holistic view of the broader geopolitical landscape impacting LNG stakeholders. In summation, this review provides a comprehensive analysis of LNG technology advancements and their far-reaching impact on global energy markets. As technological innovations continue to reshape the LNG landscape, this review serves as a roadmap for understanding the intricate interplay of environmental, economic, regional, and geopolitical factors that collectively define the contemporary dynamics of the LNG industry.

Novel process design for waste energy recovery of LNG power plants for CO2 capture and storage

In an liquefied natural gas (LNG) power plant, the amine scrubbing and CO2 liquefaction process are generally employed for CO2 capture and storage (CCS) because it is suitable for large-scale plants. However, a large amount of hot and cold energy is required for CO2 absorption, regeneration and liquefaction. As a solution, the waste LNG cold energy from the LNG regasification process and waste hot energy from natural gas combined cycle (NGCC), which are generally disposed into the seawater, can be recovered and utilized for the abovementioned purposes. Hence, this study suggested a novel process for waste hot and cold energy recovery of the LNG power plants for CCS. The suggested process model consists of the following four steps: LNG regasification, natural gas combined cycle, CO2 capture and regeneration and CO2 liquefaction. In the process model, the waste LNG cold energy is recovered at the lean amine cooler in the CO2 capture process and each heat exchanger in the CO2 liquefaction process. Furthermore, for CO2 regeneration, the waste hot energy from NGCC is recovered at the stripper reboiler. The exergy and economic analyses were addressed to evaluate the economic feasibility of energy conversion of the proposed process. As a result, compared to the base process, the net power generation and exergy efficiency of the proposed process increased by 16% and 8%, respectively. In addition, the net profit of the proposed process increased by 75%, indicating high economic feasibility. The overall energy efficiency and economic feasibility using waste cold and hot energy were observed to increase, which resulted in decreased fuel usage. Therefore, we believe that the proposed approach can contribute significantly to the economic improvements and environmental protection efforts.

Adaptive design methodology of segmented non-uniform fin arrangements for trans-critical natural gas in the printed circuit heat exchanger

As the core heat transfer equipment of a floating storage regasification unit (FSRU), the printed circuit plate heat exchanger (PCHE) has a significant impact on the gasification performance of liquefied natural gas (LNG). During LNG regasification process, natural gas undergoes a trans-critical process and its thermal properties such as density, viscosity and specific heat capacity vary considerably especially near the pseudo-critical point, which will probably lead to more volatile flow heat transfer mechanism. The traditional design scheme of uniform finned channel is difficult to give full play to the efficiency and compactness of PCHE because of lacking considering the local fluid thermodynamic variation. Therefore, this paper provides a novel design method for optimizing the flow channel profile of PCHE by applying adaptive segmented non-uniform finned micro-channels. Firstly, the entire flow channels are segmented by qualifying the gradient of density with temperature ∂ρ/∂t of trans-critical natural gas. Subsequently, within the constraints of heat exchange requirements, maximum allowable pressure drop, existing manufacturing techniques and structural strength, a mathematical optimization design model considering non-uniform fin arrangements and interlinked thermal states among these segmented channels is established. Then, to comprehensively improve entropy generation number and volume, Pareto solutions covering local flow channel parameters are obtained based on multi-objective genetic algorithm. Finally, the actual performance differences between two optimization methods respectively derived from the conventional uniform fin channels and the proposed non-uniform fin arrangements are compared based on distributed parameter model. The results show that the deviation of the entropy generation number between the optimized and validated values for the non-uniform design is very small at 6.5%, much less than that of 31.4% in the uniform design. Moreover, under the premise of the similar heat transfer efficiency, the volume for the PCHE by the non-uniform design can be reduced by 9.3%. These indicate that the proposed design methodology of segmented non-uniform fin arrangements indeed makes the PCHE more compact and enables the thermal-hydraulic performance better. The current work will serve as a framework for the design and optimization of PCHEs with drastic changes in fluid physical properties.

Conventional and Advanced Exergy Analyses of an Integrated LNG Regasification–Air Separation Process

Liquefied natural gas (LNG) is being imported in Pakistan to bridge the gap between the indigenous production and demand for natural gas. The calorific value of imported LNG must be lowered to meet the design requirements of the existing gas-fired power plants. This reduction in calorific value requires mixing with high-purity nitrogen, which can be obtained from the cryogenic distillation of air. Because imported LNG has a significant amount of cold energy and must be regasified/vaporized before injecting into the gas pipeline network, there is potential for recovering this cold energy by integrating the LNG regasification process with the cryogenic air separation process. To achieve these objectives, we developed an integrated LNG regasification–air separation process and compared it with the standalone air separation process. Conventional exergy analysis shows that the integrated process is better than the standalone air separation process both in terms of total power consumption and total exergy destruction ratio. The integrated process was further analyzed using advanced exergy analysis to identify the origin and nature of exergy destruction in the process. The results show that 44.3% of total exergy destruction in the process can be classified as avoidable. Moreover, 91.7% of the avoidable exergy destruction is of endogenous nature, showing that improving the efficiency of individual pieces of equipment should be the topmost priority for process improvement.

Dynamic Modelling of LNG Powered Combined Energy Systems in Port Areas

Liquefied Natural Gas (LNG) is a crucial resource to reduce the environmental impact of fossil-fueled vehicles, especially with regards to maritime transport, where LNG is increasingly used for ship bunkering. The present paper gives insights on how the installation of LNG tanks inside harbors can be capitalized to increase the energy efficiency of port cities and reduce GHG emissions. To this purpose, a novel integrated energy system is introduced. The Boil Off Gas (BOG) from LNG tanks is exploited in a combined plant, where heat and power are produced by a regenerated gas turbine cycle; at the same time, cold exergy from LNG regasification contributes to an increase in the efficiency of a vapor compression refrigeration cycle. In the paper, the integrated energy system is simulated by means of dynamic modeling under daily variable working conditions. Results confirm that the model is stable and able to determine the time behavior of the integrated plant. Energy saving is evaluated, and daily trends of key thermophysical parameters are reported and discussed. The analysis of thermal recovering from the flue gases shows that it is possible to recover a large energy share from the turbine exhausts. Hence, the system can generate electricity for port cold ironing and, through a secondary brine loop, cold exergy for a refrigeration plant. Overall, the proposed solution allows primary energy savings up to 22% when compared with equivalent standard technologies with the same final user needs. The exploitation of an LNG regasification process through smart integration of energy systems and implementation of efficient energy grids can contribute to greener energy management in harbors.

The Possible Coupling of LNG Regasification Process with the TSA Method of Oxygen Separation from Atmospheric Air.

Liquefied Natural Gas (LNG) must be vaporized before it is used in the combustion process. In most regasification terminals, energy that was previously expended to liquefy natural gas is dissipated in the environment. The paper proposes the use of the thermal effect of LNG regasification for the atmospheric air separation as a possible solution to the LNG exergy recovery problem. The presented idea is based on the coupling of the LNG regasification unit with an oxygen generator based on the Temperature Swing Adsorption (TSA) process. Theoretical analysis has revealed that it is thermodynamically justified to use the LNG enthalpy of vaporization for cooling of the TSA adsorption bed for increasing its adsorptive capacity. It has been shown that 1 kg of LNG carries enough exergy for separating up to approximately 100 g of oxygen using the TSA method. Although the paper suggests using the enthalpy of LNG vaporization for atmospheric air separation, similar processes for other gas mixture separations using the TSA method can be applied.

Techno-economic analysis of waste heat recovery by inverted Brayton cycle applied to an LNG-fuelled transport truck

Aiming for the better environmental and economic performance of traditional engines, waste heat recovery (WHR) technologies are actively studied to find their most beneficial applications. In this work, the inverted Brayton cycle (IBC) is investigated as a potential WHR solution for liquefied natural gas (LNG) fuelled transport truck. LNG being one of the less polluting fossil fuels is widely spreading nowadays in different industries due to the rapid development of the LNG supply chain in the world. LNG-fuelled cargo transportation follows this prevailing trend. Based on the overexpansion of flue gases to subatmospheric pressure, inverted Brayton cycle, in turn, is considered a prospective technology of WHR and techno-economic analysis of IBC in several configurations on-board of a heavy transport truck have been assessed. IBC is integrated into the engine cooling system in the basic layout, and additionally, it incorporates LNG regasification process in advanced configurations. Power balance based on Aspen Hysys model enables to perform system optimisation and gives preliminary design parameters of the system components. Cost function approach provides the basis for a preliminary economic assessment of the layouts. Although the system shows fuel economy of maximum about 2.1 %, analysis revealed the necessity to continue the search for better technical solutions in IBC-based systems to make them economically attractive due to high cost of installed equipment.

Thermodynamic improvements of LNG cold exergy power generation system by using supercritical ORC with unconventional condenser

Organic Rankine cycle (ORC) is the most commonly used power generation cycle that is adopted in this paper to make full use of the cold exergy of liquefied natural gas (LNG). As the heat exchangers are mainly responsible for the exergy destruction of the system, two improvement techniques: supercritical system and unconventional condenser, are proposed to decrease the exergy destructions in steam generator and condenser. The performances of ten preselected working fluids are tested by optimizing five key parameters at three heat source temperatures. The results show that using the supercritical system can improve the system efficiency for fluids with low critical temperatures by reducing the exergy destructions in steam generators. Using the unconventional condenser can greatly improve the system efficiency by decreasing the exergy destruction during the LNG regasification process of most fluids, barring a few wet expansion fluids. The improvements offered by both techniques become more obvious as the heat source temperature increases. However, combining the two techniques only improves the performance for fluids with low critical temperatures, and does not work for most fluids. The highest efficiency is always achieved by the subcritical system with an unconventional condenser at each heat source temperature. When the heat source temperatures are 100 °C and 150 °C, R290 obtains the highest efficiency values of 17.89% and 21.26%, respectively. At 200 °C, R600a achieves the highest efficiency of 25.35%.

Integration of LNG Regasification Process in Natural Gas-Fired Power System with Oxy-Fuel Combustion

Oxy-fuel combustion power systems can utilize the cold energy released during the liquefied natural gas (LNG) regasification to reduce the power consumption of CO2 capture, but the specific LNG cold energy consumption of CO2 capture is still too large. To recover more CO2 with the limited LNG cold energy at a low energy cost, a novel natural gas-fired oxy-fuel power system with the cascade utilization of LNG cold energy is proposed in this work, where the LNG cold energy could be sequentially utilized in the air separation unit and the CO2 recovery process. The new system is evaluated with the Aspen Plus software. The results show that the net electrical efficiency and the specific primary energy consumption for CO2 avoided (SPECCA) of the new system are comparable to those of the chemical looping combustion cycle, and superior to those of the conventional O2/CO2 cycles. Moreover, the specific LNG needed for CO2 avoided (SLNCC) of the new system is more than 67.2% lower than the existing oxy-fuel power systems utilizing the LNG cold energy. Furthermore, it is found that the O2 purity of 97.0 mol.% and the CO2 capture ratio of 97.0% are optimal conditions, because the SPECCA, the specific exergy consumption for CO2 avoided (SECCA) and the SLNCC are at the minimum of 1.87 $${\rm{G}}{{\rm{J}}_{LHV}} \cdot {{\rm{t}}_{{\rm{C}}{{\rm{O}}_2}}}^{- 1},2.60\,\,{\rm{GJ}} \cdot {{\rm{t}}_{{\rm{C}}{{\rm{O}}_2}}}^{- 1}$$ and $$1.88\,\,{{\rm{t}}_{{\rm{LNG}}}} \cdot {{\rm{t}}_{{\rm{C}}{{\rm{O}}_2}}}^{- 1}$$ , respectively. Meanwhile, the net electrical efficiency and the exergy efficiency of the new system reach 51.51% and 49.23%, respectively.

Cold energy recovery performance study for liquefied natural gas (LNG) regasification process

The Earth's cleanest burning fossil fuel - natural gas (NG), is primarily methane (CH4) with smaller quantities of other hydrocarbons. As the grid is decarbonizing, the role of NG on the road to a decarbonized future is indisputable. NG is often compressed and converted into liquified natural gas (LNG) that occupies 600 times less space than its gaseous form, optimizing its storability and delivery efficiency. This logistical flexibility helps improve the security of NG supplies worldwide and is making LNG one of the fastest-growing energy markets. At the LNG terminals, LNG is converted back into its gaseous state by regasification, then, distributed across the network, from remote production areas to distant markets where NG supplies are needed. Regasification of LNG releases a significant amount of cold energy. This paper examines the effect of Open Rack Vaporizer (ORV) efficiency and the potential of recoverable cold energy in the LNG regasification process. All data were collected from the industry-leading LNG regasification terminal in Malaysia - The Pengerang LNG (Two) SDN. Bhd. (PLNG2). The results of this study showed that the monthly potential of recoverable cold energy is around 43 MW and the efficiency of ORV is ranged from 60 % to 95 %. In addition, it has been found that the flow rate of LNG and the flow rate of seawater are two significant parameters that affect the potential recoverable cold energy.

Novel massive thermal energy storage system for liquefied natural gas cold energy recovery

The concept of heat integration with cryogenic energy storage (CES) is a possible option for the recovery of wasted cold energy from liquefied natural gas (LNG). For maximizing energy storage capacity, we propose a conceptual design for a massive cryogenic energy storage system integrated with the LNG regasification process (MCES). The novel aspect of this study is the transmission of LNG cold energy via two different methods at different times: (1) MCES stores cold energy in liquid propane during on-peak times, enabling increase in the energy storage capacity; and (2) MCES directly transfers cold energy with help of liquid propane during off-peak times to liquefy air using surplus electricity from the grid. Thus, the surplus energy is stored in liquefied air and released to generate electricity on demand. Based on the process simulation, exergy analysis and economic evaluations are conducted. MCES exhibits a round trip efficiency of 85.1%, whereas existing bulk power management systems exhibit a maximum efficiency of 75%. Moreover, using a three-million-ton-per-annum LNG regasification plant, MCES enables the supply of 138 MW of electrical power which is up to 96% more power than that achieved by other recently proposed process designs, and has potential for bulk power management.

Minimizing power consumption of boil off gas (BOG) recondensation process by power generation using cold energy in liquefied natural gas (LNG) regasification process

Abstract During the process of storage and transportation of liquefied natural gas (LNG), boil off gas (BOG) is generated. The presence of BOG causes the rise of pressure of the storage tank, and makes the LNG receiving terminal have a large safety hazard, which needs to be condensed and recovered. BOG recondensation process is a high power-consumption process, and meanwhile LNG regasification process releases a large amount of cold energy, which can be used to generate electricity. In order to reduce the power consumption of BOG recondensation process, this paper proposes the idea of power generation using cold energy in LNG regasification process to drive the compressors and LNG pumps in BOG recondensation process. Firstly, the cold energy recovery potentials of four different BOG recondensation processes are determined through parameter analysis and power consumption comparison. Based on this, four BOG recondensation and LNG cold energy power generation integrated systems are proposed, and the parameters and working fluids of the integrated system are optimized. Results show that the power consumptions of the integrated systems are significantly lower than those of the original BOG recondensation systems at different BOG contents. In most cases, the proposed system can meet the power requirement of the BOG recondensation process, and at the same time has the ability to output electrical energy. The power reduction rate of the integrated system decreases as the BOG content increases. When the BOG content is 0.03, the power reduction rate can be up to 250%. When the BOG content is 0.15, the power reduction rate can be up to 120%.

Flexible integration of liquid air energy storage with liquefied natural gas regasification for power generation enhancement

Liquid Air Energy Storage (LAES) is one of the most promising energy storage technologies for achieving low carbon emissions. Our research shows that the LAES produces a considerable amount of excess heat that cannot be cost-effectively utilised in a standalone LAES system. On the other hand, the regasification of liquefied natural gas (LNG) often leads to waste of a large amount of high-grade cold energy. Therefore, this paper proposes the integration of the LAES with the LNG regasification process via a Brayton cycle (denoted as LAES-Brayton-LNG), where pressurized propane is used as both the heat transfer fluid and storage material for the LNG cold energy. The excess heat from the LAES works as the heat source and the waste cold from the LNG regasification as the cold source for the Brayton cycle. Such an integrated LAES-Brayton-LNG system does not need to change the existing LAES system configuration, and the LNG regasification process is independent of the LAES system, thus allowing operation flexibilities. Our analyses show that the flexibly integrated LAES-Brayton-LNG system achieves a system exergy efficiency of 57% and could improve the system exergy efficiency of the standalone LAES system by 14.4%. What’s more, it has an electrical round trip efficiency of ∼70.6%, which is ∼56.5% higher than that of the standalone LAES system. Hence, the proposed LAES-Brayton-LNG system is comparable with other large scale energy storage technologies in terms of the electrical round trip efficiency.