Hydrogen Liquefaction Plant Research Articles

Dimensionless performance mapping of cryogenic plate-fin heat exchangers with ortho-para hydrogen continuous conversion for hydrogen liquefaction

Continuous conversion heat exchangers are recognized as the next-generation technology for large-scale and energy-efficient hydrogen liquefaction plants. However, their structural design and operational optimization are impeded by the absence of generalised evaluation methodology, as well as unclear coupling mechanisms of convection and conversion. This study develops a novel dimensionless model incorporating the number of heat transfer units and the Damköhler number, to describe the convective transport and catalytic conversion process for continuous conversion heat exchangers. Their comprehensive performance is evaluated by defining the cooling, conversion, and total effectiveness, based on which performance maps are subsequently proposed for three typical temperature zones. The scaling results demonstrate that the conversion-convection characteristics along the heat exchanger train exhibit multiple complex stages, heavily contingent upon the space velocity and the ratio of heat capacity rates between hot and cold fluids. To achieve the effectiveness of over 0.90, these two operational parameters should be below about 1000 h−1 and 0.50, respectively. The characteristic variables are recommended to meet Da0 ≥ 8 and NTU0 ≥ 16 as a minimum requirement for various heat exchangers. These findings offer a theoretical foundation for high-efficient design and operation of continuous conversion heat exchangers in future hydrogen liquefaction plants.

Pre-cooling systems in modern hydrogen liquefaction

The research work presents recommendations for choosing a circuit design for low-capacity hydrogen liquefaction plants with a production rate up to 20 kg/h or 0,48 tpd (ton per day). Main design criteria considered are specific energy cost, as well as capital costs and overall characteristics of the system. A review of theoretical and real hydrogen liquefaction cycles is presented. Mathematical models of different circuits are built up considering real parameters of the typical equipment. The advantages and disadvantages of certain solutions are identified, efficiency trends in terms of hydrogen liquefaction plants are analysed. According to the obtained results of the research main of the circuits for low-capacity hydrogen liquefaction plants are selected.

Revisiting the cost analysis of importing liquefied green hydrogen

Hydrogen emerges as a promising energy carrier in achieving carbon neutrality, especially in countries such as South Korea and Japan, where renewable energy resources are scarce. Consequently, economically importing hydrogen from overseas is paramount to a stable supply. However, previous studies have often oversimplified the estimation of hydrogen import costs with optimistic assumptions, raising doubts about their reliability. This study comprehensively assesses costs incurred from green hydrogen production to liquefaction and transportation. The cost analysis includes detailed design considerations for hydrogen liquefaction and re-conditioning plants, alongside thermodynamic simulations to estimate the boil-off gas rate of liquid hydrogen during transport. Focusing on a case study of importing liquefied green hydrogen from Australia to South Korea, our findings reveal that the levelized cost of hydrogen is approximately 30.2 USD/kgH2 as of 2023. Projections suggest a decrease to around 18.3 USD/kgH2 by 2050, assuming technological advancements, significantly exceeding values reported in the existing literature. Sensitivity analysis highlights the renewable electricity price in Australia and the boil-off rate during shipping as key factors that significantly influence the levelized cost of hydrogen.

Comparative energy and exergy analysis of ortho-para hydrogen and non-ortho-para hydrogen conversion in hydrogen liquefaction

This study reports the comparative energy and exergy analysis of ortho-para hydrogen and non-ortho-para hydrogen conversion in hydrogen liquefaction process. Two cases were simulated, case A – hydrogen liquefaction with ortho-parahydrogen conversion and case B – hydrogen liquefaction without ortho-parahydrogen conversion. This is the first study that presents a comparative energy and exergy analysis between such two cases. In this research, a hydrogen liquefaction process was designed adopting cascaded five-stage Brayton refrigeration cycle. The process was simulated in Aspen PLUS. The process used a mixed refrigerant (of liquefied natural gas) refrigeration cycle to precool the gaseous hydrogen feed from 26 °C temperature to −192 °C temperature, and mixed refrigerant (of nelium) was subsequently used to further deep-cool the the hydrogen stream from −192 °C temperature to −245.99 °C temperature in the cryogenic section of the process. Liquefaction was achieved by expanding the hydrogen through Joule-Thomson valve at −248.37 °C and 1 bar. The simulated results of the two cases showed the specific energy consumption of case A to be 8.45 kWhr/kgLH, and that of case B to be 15.65 kWhr/kgLH respectively. The results also indicated a total exergy efficiency of 92.42% in case A and 87.18% in case B. The research results showed that the hydrogen liquefaction designed with configuration of ortho-parahydrogen conversion has better performance indicators than the liquefaction without ortho-parahydrogen conversion. Therefore, hydrogen liquefaction with ortho-parahydrogen conversion can be considered in the design and development of new hydrogen liquefaction plants. Process optimization is recommended to further enhance the specific energy consumption and exergy efficiency of both processes.

Small-scale industrial hydrogen liquefaction and refrigeration

As the hydrogen economy expands, the need for point of use production with smaller liquid hydrogen (LH2) production capacities will increase. Examples of this are transportation hubs in remote locations and numerous other applications where the required LH2 production is less than 5 MT/day. In response to this need, a small-scale industrial 1,000 kg/day hydrogen liquefaction plant is being developed and is planned for operation in 2024. The plant will achieve localized, efficient production, on-demand, in remote locations or any location advantageous for use in transportation, where complicated logistics, with associated transportation costs and tanker evaporative losses are eliminated or minimized. The chief advantages of the design are small size/footprint, safety, reliability, low cost, lack of restrictions on site location, and ability to make practical use of renewable energy. The liquefaction plant utilizes a closed-loop helium reverse-Brayton cycle refrigerator where refrigerant temperatures significantly less than the hydrogen liquefaction temperature cause the hydrogen gas stream to be liquefied. The liquefied hydrogen is maintained in the liquid state via a helium side stream taken from the refrigeration loop routed through the LH2 storage tank. This optional system can maintain LH2 temperatures in the storage tank lower than 18 K to eliminate boiloff and facilitate zero loss transload from tanker trucks and eliminate losses in transfer/dispensing. The hydrogen liquefaction plant does not require liquid nitrogen (LN2) pre-cooling and so can be located in remote areas wherever there is 480 V electricity and hydrogen production capacity available. A slightly modified reverse-Brayton cycle is also used in the refrigeration/storage plants. These plants can facilitate zero loss tanker transload and zero boiloff for LH2 storage plants of virtually any capacity. The smallest of these reverse-Brayton cycle refrigerators, currently in detailed design, refrigeration system RS1500 (1000 W heat lift @ 20K) will be capable of eliminating boiloff losses of the largest storage tanks currently in operation with very low electrical energy consumption.

Technical and cost analysis of zero-emission high-speed ferries: Retrofitting from diesel to green hydrogen

This paper proposes a technical and cost analysis model to assess the change in costs of a zero-emission high-speed ferry when retrofitting from diesel to green hydrogen. Both compressed gas and liquid hydrogen are examined. Different scenarios explore energy demand, energy losses, fuel consumption, and cost-effectiveness. The methodology explores how variation in the ferry's total weight and equipment efficiency across scenarios impact results. Applied to an existing diesel high-speed ferry on one of Norway's longest routes, the study, under certain assumptions, identifies compressed hydrogen gas as the current most economical option, despite its higher energy consumption. Although the energy consumption of the compressed hydrogen ferry is slightly more than the liquid hydrogen counterpart, its operating expenses are considerably lower and comparable to the existing diesel ferry on the route. However, constructing large hydrogen liquefaction plants could reduce liquid hydrogen's cost and make it competitive with both diesel and compressed hydrogen gas. Moreover, liquid hydrogen allows the use of a superconducting motor to enhance efficiency. Operating the ferry with liquid hydrogen and a superconducting motor, besides its technical advantages, offers promising economic viability in the future, comparable to diesel and compressed hydrogen gas options. Reducing the ferry's speed and optimizing equipment improves fuel efficiency and economic viability. This research provides valuable insights into sustainable, zero-emission high-speed ferries powered by green hydrogen.

Thermoeconomic, environmental and uncertainty assessments and optimization of a novel large-scale/low carbon hydrogen liquefaction plant integrated with liquefied natural gas cold energy

Abstract Presently, the liquefaction of hydrogen represents a promising solution to alleviate challenges associated with its storage and transportation. It is crucial to formulate methodological frameworks for scrutinizing hydrogen liquefaction routes to enhance energy efficiency. This paper endeavors to establish, assess feasibility, and refine a novel approach for a high-capacity hydrogen liquefaction facility, leveraging the cold energy from liquefied natural gas (LNG). This new route utilizes four hybrid refrigeration systems, each designed to handle 50 × 103 kg daily. Significant energy savings are achievable through the primary utilization of LNG’s energy in the precooling stage and the generation of electrical power during the vaporization phase. The architecture of this novel route is crafted around the principles of energy conservation, incorporating thermodynamic assessments alongside economic and environmental viability studies. Furthermore, the performance of this innovative hydrogen liquefaction method is thoroughly evaluated across both non-optimized and optimized scenarios. Advanced techniques such as composite curve and uncertainty analyses are employed to provide a detailed examination of heat cascades and cost differentials. The findings indicate that managing LNG’s cold energy is crucial for refining the hydrogen liquefaction route, potentially reducing the specific power requirement of the optimum route by 27.4% compared to its non-optimum counterpart. Moreover, in the optimized scenario, there is a decrease of ~4.72% in unit production expenses, 26.26% in CO2 emissions, and 21.85% in specific power usage for avoided CO2 emissions.

A novel hydrogen liquefaction process using dual mixed cryogenic refrigeration system: Energy, exergy, and economic analysis

In conventional hydrogen liquefaction plants, the liquefaction process consumes high portion of about 30 % of the liquid hydrogen (LH2) energy content. In addition, existing LH2 technology uses pure or single mixed refrigerants, which are susceptible to freezing problems. To address these challenges, this study introduces an innovative hydrogen liquefaction process utilizing dual mixed refrigeration (DMR) system. This process incorporates two interactive mixed refrigerants in two integrated refrigeration loops, offering flexible capability to handle large-scale capacities with minimal energy consumption and free of freezing problems. The proposed process achieved extremely low specific energy consumption (SEC) of 3.732 kWh/kgLH2, 48 % lower than the average SEC of the large-scale single mixed refrigerant (SMR) systems (7.128 kWh/kgLH2). Also, its exergy efficiency (59.65 %) is 33 % higher than the average exergy efficiency of the SMR-based systems (44.89 %). Furthermore, the proposed DMR-based process reduces the levelized cost of liquid hydrogen production to 1.89 $/kgLH2, which is 70 % lower than the small-scale processes and 21 % lower than the average cost of the large-scale SMR-based systems. This study of the dual mixed cryogenic refrigeration approach provides new methodology and guidelines for future research to significantly improve the technical and economic feasibility of LH2 production, making it competitive with other energy storage and transportation options.

Ammonia Airship Cooling: An Option for Renewable Cooling in the Tropics

The world is warming, and the demand for cooling is increasing. Developing a future green hydrogen economy will also increase the demand for cooling for hydrogen liquefaction. This increase in cooling demand will happen mainly in tropical and developing countries due to their increase in population, improvements in quality of life, and the export of their renewable potential with liquid hydrogen. To solve this increase in demand for cooling, this paper proposes the use of ammonia airship cooling (AAC). AAC extracts cold from the tropopause (−80 °C) with airships and ammonia refrigeration cycles. The liquid ammonia is then transported back to the surface to provide low temperature cooling services (−33 °C). This cooling service is particularly interesting for lowering the electricity consumption in hydrogen liquefaction plants. If all the technological challenges mentioned in the paper are addressed, it is estimated that the cost of cooling with the technology is 8.25 USD/MWht and that AAC could reduce the electricity demand for hydrogen liquefaction by 30%. AAC is an innovative renewable cooling technology that has the potential to complement other renewable energy sources in a sustainable future.

Techno-economic analysis for design and management of international green hydrogen supply chain under uncertainty: An integrated temporal planning approach

The international green hydrogen supply chain (HSC) is anticipated to play a pivotal role in the ongoing energy transition. Our research endeavors to assess the implications of considering fast timescale volatility in renewable energy sources and uncertainties in demand on the design and evaluation of the international green hydrogen supply chain. To achieve this objective, we introduce a comprehensive bi-level optimization method for evaluating the economic viability of the HSC between nations. In the upper level of the optimization, capacity investments are determined using Bayesian optimization and Hyperband (BOHB) for multiple components, including turbines, PV panels, batteries, water electrolyzers, hydrogen liquefaction plants, hydrogen tanks, and liquid hydrogen (LH2) ships. The lower level focuses on the optimal scheduling of LH2 shipments and the operation of each facility, utilizing a mixed-integer linear programming (MILP) model that considers lead time and uncertainties in both supply and demand. We conduct case studies involving nine projects, encompassing three potential import and export countries, to demonstrate and analyze the effectiveness of the proposed framework. Furthermore, we delve into the impacts of various factors, such as economies of scale, lead time, and the minimum operating constraint of the electrolyzer, on the economic performance of the green HSC project. The study also explores the optimal balance between facility installation scales and their relationships with techno-economic parameters, providing valuable insights for future research, technological advancement and supply chain design.

Rotordynamic Analysis and Operating Test of an Externally Pressurized Gas Bearing Turbo Expander for Cryogenic Applications

This study designed an externally pressurized bearing and analyzed the rotordynamics of a turbo expander for a hydrogen liquefaction plant. The turbo expander, comprising a turbine and compressor wheel assembled to a shaft, lowered the temperature of the helium refrigerant. Its rated speed was 75,000 rpm, and an externally pressurized gas bearing was selected to support the rotor. Pressurized helium was used as the lubricant for the bearing operation. To design the rotor–bearing system, we conducted a bearing performance analysis and rotordynamic characteristic prediction using the developed numerical model. We calculated the bearing stiffness and flow rate of the bearing gas for various feed parameters and selected the appropriate orifice diameter for maximum stiffness. The predicted Campbell diagram showed that the system had a sufficient separation margin with the critical speed, and the predicted critical speed correlated well with the nonlinear orbit simulation. A successful operation was achieved with the manufactured turbo expander within the rated speed. The shaft vibration was monitored during the operation test, and the test results revealed two critical speeds below the rated speed, as predicted by the analytical model. In addition, the shaft vibration was maintained at <3 μm.

Raman spectroscopy for ortho-para hydrogen catalyst studies

For the design of efficient hydrogen liquefaction plants and for the production of accurate ortho-para hydrogen samples, precise knowledge about the kinetics of ortho-para catalysts and accurate ortho-para monitoring is mandatory. Raman spectroscopy as a direct measurement of the ortho-para ratio is independent of other gas parameters, such as temperature, pressure, and flow rate and also undisturbed by impurities, such as nitrogen and oxygen in the gas. Therefore, Raman spectroscopy is a superior technique for ortho-para monitoring, com-pared to methods based on thermodynamic properties like heat conductivity. Within this work, an experimental proof of concept of a Raman based system to study ortho-para catalyst kinetics is shown.

Optimisation de la traçabilité en endoscopie

For the design of efficient hydrogen liquefaction plants and for the production of accurate ortho-para hydrogen samples, precise knowledge about the kinetics of ortho-para catalysts and accurate ortho-para monitoring is mandatory. Raman spectroscopy as a direct measurement of the ortho-para ratio is independent of other gas parameters, such as temperature, pressure, and flow rate and also undisturbed by impurities, such as nitrogen and oxygen in the gas. Therefore, Raman spectroscopy is a superior technique for ortho-para monitoring, com-pared to methods based on thermodynamic properties like heat conductivity. Within this work, an experimental proof of concept of a Raman based system to study ortho-para catalyst kinetics is shown.

Novel dual-mixed refrigerant precooling process for high capacity hydrogen liquefaction plants with superior performance

Liquid hydrogen is a superior alternative for the current energy storage methods and energy carriers as it has higher energy density and cleanliness. However, hydrogen liquefaction is an energy-intensive process. In particular, the precooling process of hydrogen consumes a tremendous portion of about 30 % of the total compression power of the plant. Several previous studies introduced various pure-refrigerant and single mixed refrigerant (SMR) precooling processes, however, their specific energy consumption (SEC) still very high especially at large-scale capacities. Therefore, this study presents a novel, efficient, and large-scale dual-mixed refrigerant (DMR) process to precool the hydrogen from 25 °C to -192 °C at a pressure of 21 bar. New heavyweight-based mixed refrigerant MR1 and lightweight-based mixed refrigerant MR2 are developed for the DMR process using a new-proposed systematic approach. The proposed DMR process is capable of handling a wide range of hydrogen flow from 100 TPD to 1000 TPD with SEC of 0.862 kWh/kgH2Feed, which is 20.33 % lower than the most competitive SMR process available in the literature. Based on the sensitivity analysis, further optimization of the DMR operating parameters reduced the SEC to 0.833 kWh/kgH2Feed at an optimal capacity of 500 TPD. Furthermore, the COP of the new process is improved by 14.47 % and the total annualized cost is reduced by 12.24 %. Compared to five other technologies that use the pure-refrigerant and other SMR precooling processes, the DMR reduces the SEC by 39.0 % to 63.0 %. The novel precooling process presented herein has the potential to drive the development of large-scale hydrogen liquefaction processes.

Techno-economic modeling of zero-emission marine transport with hydrogen fuel and superconducting propulsion system: Case study of a passenger ferry

This paper proposes a techno-economic model for a high-speed hydrogen ferry. The model can describe the system properties i.e. energy demand, weight, and daily operating expenses of the ferry. A novel aspect is the consideration of superconductivity as a measure for cost saving in the setting where liquid hydrogen (LH2) can be both coolant and fuel. We survey different scenarios for a high-speed ferry that could carry 300 passengers. The results show that, despite higher energy demand, compressed hydrogen gas is more economical compared with LH2 for now; however, constructing large-scale hydrogen liquefaction plants make it competitive in the future. Moreover, compressed hydrogen gas is restricted to a shorter distance while LH2 makes longer distances possible, and whenever LH2 is accessible, using a superconducting propulsion system has a beneficial impact on both energy and cost savings. These effects strengthen if the operational time or the weight of the ferry increases.

A novel integrated system of hydrogen liquefaction process and liquid air energy storage (LAES): Energy, exergy, and economic analysis

With the global positive response to environmental issues, cleaner energy will attract widespread attention. To improve the flexible consumption capacity of renewable energy and consider the urgent need to optimize the energy consumption and cost of the hydrogen liquefaction process, a novel system integrating the hydrogen liquefaction process and liquid air energy storage (HLP–LAES) is proposed. The operating strategy of the system ensures that it can produce liquid hydrogen and has the function of energy storage and power generation. A 3E study (energy, exergy, and economics) is carried out to evaluate the techno-economic performance of the proposed energy-intensive process. After optimization of key parameters, when the daily output of liquid hydrogen is 50 tons, the maximum daily power generation can reach 131.3 MWh, accounting for 1.21% of the daily electricity consumption of urban and rural residents in Qinghai Province, China. The round-trip efficiency of the proposed process is 58.9%, the specific energy consumption of liquid hydrogen is 7.25 kWh/kgLH2, and the total exergy efficiency is 53.2%. The payback period will be reduced to 1.7 years when the liquid hydrogen is sold at 7.0 $/kgLH2. If the proposed process is retrofitted from a stand-alone hydrogen liquefaction plant, the shortest retrofitting payback period is 9.2 years. The charging and discharging processes of the LAES are innovatively redesigned to better match the hydrogen liquefaction process, while achieving deep coupling and good synergy between the systems. This work aims to provide a reference for the efficient consumption of renewable energy, grid load balancing, and commercialization of the combination of liquid air energy storage and hydrogen liquefaction plants.

Assessment of offshore liquid hydrogen production from wind power for ship refueling

Green hydrogen from electrolysis has become the most attractive energy carrier for making the transition from fossil fuels to carbon-free energy sources possible. Especially in the naval sector, hydrogen has the potential to address environmental targets due to the lack of low-carbon fuel options. This study aims at investigating an offshore liquefied green hydrogen production plant for ship refueling. The plant comprises a wind farm for renewable electricity generation, an electrolyzer stack for hydrogen production, a water treatment unit for demineralized water production, and a hydrogen liquefaction plant for hydrogen storage and distribution to ships. A pre-feasibility study is addressed to find the optimal capacities of the plant that minimize the payback time. The model results show that the electrolyzer capacity shall be set equal to a value between 80% and 90% of the wind farm capacity to achieve the minimum payback times. Additionally, the wind farm capacity shall be higher than about 150 MW to limit the payback time to values lower than 11 years for a fixed hydrogen price of 6 €/kg. The Levelized Cost of Hydrogen results to be below 4 €/kg for a wide range of plant capacities for a lifetime of the plant of 25 years. Thus, the model shows that this plant is economically feasible and can be reproduced similarly for different locations by rescaling the different selected technologies. In this way, the naval sector can be decarbonized thanks to a new infrastructure for the production and refueling of liquified green hydrogen directly provided on the sea.

Catalyst filled heat exchanger for hydrogen liquefaction

Cryogenic hydrogen liquefaction plants have a uniquely designed plate fin heat exchanger (PFHE) in which the fin channels are filled with an ortho-para hydrogen conversion catalyst (O-P catalyst). This PFHE can save liquefaction energy by reducing the heat of liquefaction. Despite the unique heat exchanger design, there are few studies on the thermohydraulic performance of the PFHE for the hydrogen liquefaction process. In this study, the thermohydraulic performance of a PHFE filled with an O-P catalyst is investigated in two steps. In the first step, pressure drop experiments are performed using a cylinder filled with commercial O-P catalyst. The pressure drop is approximately five times lower than that of the Ergun's equation. Therefore, we propose a new correlation for the porous channel filled with the O-P catalyst and apply it in the numerical research, which is the second step. According to the results, the difference in Nu/f1/3 between the new empirical correlation and the Ergun's equation is up to 1.6 times, and the exergy efficiency of the CPFHE is underestimated by Ergun's equation. Furthermore, we report the impact of the design parameters on the heat transfer and pressure drop on a PFHE filled with catalyst. This CPFHE is a counter-flow heat exchanger and includes a porous hot laminar stream and two cold laminar streams through the plain-fin channel. The design parameters are selected based on the fin height and fin spacing. Among the various fin channel designs, the most effective one involves a fin height of 4 mm and a fin spacing of 0.7 mm. Interestingly, at the same Re number, the variation in Nu/f1/3 is almost twice the variation in the fin spacing. Based on these results, we discuss the impact of the design parameters on the PFHE performance, using the performance evaluation plot. Therefore, this study is expected to provide insights and guidance for designing PFHEs in hydrogen liquefaction plants.

Process optimization and analysis of a novel hydrogen liquefaction cycle

The preliminary designed hydrogen liquefaction plant process based on liquid nitrogen precooling and helium gas turbine expansion refrigeration is firstly modified, simulated and analyzed by Aspen HYSYS. In addition, the multi-parameter optimization of the system is carried out by genetic algorithm (GA) by considering the specific energy consumption (SEC) of the system as the objective function. After optimization, it can be found that the SEC of the system is 7.1329 kWh kgLH2−1, which is 19.65% lower than that of base case and the coefficient of performance (COP) and figure of merit (FOM) are 0.1704 and 0.4941, which are higher than that prior to the process optimization. In addition, sensitivity analysis is conducted to present the effects of different operation conditions of the designed process on the features of the hydrogen liquefaction process. Compared with the other two systems of hydrogen liquefaction, the process in this paper shows the best performance.

Analysis of a clean hydrogen liquefaction plant integrated with a geothermal system

Abstract Hydrogen is attracting a lot of attention because of its high-energy content and lower weight and volume, making it a promising replacement of fossil fuels. Hydrogen liquefaction is an energy-intensive process that requires high electrical power. This paper presents a novel approach of a large-scale hydrogen liquefaction system combined with geothermal and isobutene power plant. The hydrogen liquefaction system uses a hydrogen Claude refrigeration system and a nitrogen precooling system to produce 335 ton/day of liquefied hydrogen. The mass flow rate of hydrogen in the refrigeration system and nitrogen precooling system were 14 kg/s and 52 kg/s, respectively, to produce specific energy consumption of 6.41 kWh/kg-LH2. The overall power consumption of the liquefaction system was 107 MW. This requires constructing three geothermal and isobutene power plants to produce 130 MW of electrical power. Some parametric studies were conducted to reduce the specific energy consumption (SEC). It is found that reducing the hydrogen mass flow rate to 9 kg/s and the high pressure to 20 bar results in the reduction of the SEC to 4.7 kWh/kg-LH2. However, increasing the steam and isobutene mass flow and high pressure in the system results in an increase in the electric power delivered to 225 MW from 130 MW.