Hydrogen Liquefaction Research Articles

Reducing the exergy destruction in the cryogenic heat exchangers of hydrogen liquefaction processes

A present key barrier for implementing large-scale hydrogen liquefaction plants is their high power consumption. The cryogenic heat exchangers are responsible for a significant part of the exergy destruction in these plants and we evaluate in this work strategies to increase their efficiency. A detailed model of a plate-fin heat exchanger is presented that incorporates the geometry of the heat exchanger, nonequilibrium ortho-para conversion and correlations to account for the pressure drop and heat transfer coefficients due to possible boiling/condensation of the refrigerant at the lowest temperatures. Based on available experimental data, a correlation for the ortho-para conversion kinetics is developed, which reproduces available experimental data with an average deviation of 2.2%. In a plate-fin heat exchanger that is used to cool the hydrogen from 47.8 K to 29.3 K with hydrogen as refrigerant, we find that the two main sources of exergy destruction are thermal gradients and ortho-para hydrogen conversion, being responsible for 69% and 29% of the exergy destruction respectively. A route to reduce the exergy destruction from the ortho-para hydrogen conversion is to use a more efficient catalyst, where we find that a doubling of the catalytic activity in comparison to ferric-oxide, as demonstrated by nickel oxide-silica catalyst, reduces the exergy destruction by 9%. A possible route to reduce the exergy destruction from thermal gradients is to employ an evaporating mixture of helium and neon at the cold-side of the heat exchanger, which reduces the exergy destruction by 7%. We find that a combination of hydrogen and helium-neon as refrigerants at high and low temperatures respectively, enables a reduction of the exergy destruction by 35%. A combination of both improved catalyst and the use of hydrogen and helium-neon as refrigerants gives the possibility to reduce the exergy destruction in the cryogenic heat exchangers by 43%. The limited efficiency of the ortho-para catalyst represents a barrier for further improvement of the efficiency.

Analysis and assessment of an advanced hydrogen liquefaction system

In the present work, an advanced hydrogen liquefaction system with catalyst infused heat exchangers is proposed, analyzed and assessed energetically and exergetically. The analysis starts with exergetic considerations on hydrogen liquefaction using different alternatives of pre-cooling including the conversion from normal to parahydrogen. It further explains the fundamentals of a proposed liquefaction process. The goal is then to assess the proposed system, make modifications and improve the system. The present system covers all of these portions of a hydrogen liquefaction system with an ultimate goal of achieving a sustainable and environmentally harmless system. The proposed hydrogen liquefaction system is simulated in the Aspen Plus and the performance of the system is measured through energy and exergy efficiencies. The resulting energy efficiency of the system is calculated to be 15.4%, and the exergy efficiency of the system is found to be 11.5%.

Carbon nanostructures/Mg hybrid materials for hydrogen storage

For achieving an economy based on renewable energy sources, effective solutions toward energy storage remain the main challenge. To date, there is no efficient systems to store electricity in large amounts. A promising solution is to accumulate energy in the form of hydrogen, which can then be conveniently stored and transported. However, compared to the volumetric energy density of fossil fuels, current technologies relying on hydrogen compression or liquefaction have major disadvantages, including low energy density and safety issues. The use of light materials forming hydrides could provide an alternative way to stock hydrogen with high volumetric energy densities. Herein, we present recent developments in the research for magnesium/graphene hybrid materials and their hydrogen-storage properties.

Thermal analysis of a multistage active magnetic regenerator cycle for hydrogen liquefaction

The present paper deals with thermal analysis of cascade Active Magnetic Regenerator (AMR) cycle for the liquefaction of hydrogen starting from room temperature. For this purpose, the energy equations for fluid and solid within the regenerator bed of the AMR cycle have been considered. To solve the resulting mathematical model implicit finite difference method has been used. Thermal energy and mass balances are performed for several liquefaction systems composed of different number of cascade cycles. A simulation method using Hysys simulation commercial code has been presented. The multistage system operates with an ideal magnetic material as refrigerant and hydrogen gaseous as carrier fluid. First, the coefficient of performance (COP) of the AMR cycle and the required volume of magnetic material as functions of the number of cascades have been investigated. Then, the required volume is optimized by using the relationship between the COP and the volume. It has been found that a number of 6 AMR cycles operating in series is the optimal number of cascades required to liquefy 1 kg/h of hydrogen supplied at 25 °C. The system can operate between two volumes of magnetic material; namely, the minimum required volume (2.96 L) and the most efficient volume (7.44 L), corresponding to COP values of 1.23 and 4.7 respectively.

Process development and exergy cost sensitivity analysis of a novel hydrogen liquefaction process

A novel hydrogen liquefaction process including a single mixed refrigerant cycle is proposed and investigated by energy, conventional and advanced exergy and exergoeconomic analyses methods. The proposed liquefaction process can produce 130 tons liquid hydrogen per day. Results of energy analysis reveals that 7.646kWh/kgLH2 power is consumed to liquefy the hydrogen from 21 bar to 25 °C. Exergy analysis indicates that exergy efficiency of the proposed hydrogen liquefaction process is almost 32%, which is higher than Ingolstadt operating hydrogen liquefaction plant with exergy efficiency of 21.28%. Also, the power consumption of proposed hydrogen liquefaction plant is less than its kind between other similar conceptual processes. Based on the advanced exergy analysis, most part of the exergy destruction rates of the compressors, heat exchangers and air cooler are endogenous, while the dominant part of irreversibilities of the turbo expanders is exogenous. Effect of mole fraction of the mixed refrigerant components on performance of the process is investigated. Also, sensitivity of exergy destruction cost rate and exergoeconomic factor to operating variables of the proposed hydrogen liquefaction process is investigated and discussed. Results of the analyses show that maximum exergy destruction cost rate of the process components is 2265.26 $/h, which most of it is endogenous and unavoidable.

Thermodynamic studies of a novel heat pipe evacuated tube solar collectors based integrated process for hydrogen production

In this study, the detailed thermodynamic assessment of an integrated process based on heat pipe evacuated tube solar collectors for hydrogen production is provided for more efficiently process designs. An integrated process consists of the solar heat pipe collector, photovoltaic panels, PEM electrolyzer and Linde-Hampson hydrogen liquefaction process are considered and analyzed thermodynamically for hydrogen production and liquefaction aims. The energetic and exergetic efficiencies of this integrated process are calculated as 0.2297 and 0.1955, respectively. Based on the parametric study, the effectiveness of the solar energy based integrated process is also highly dependent on the solar flux and ambient conditions.

Giant reversible magnetocaloric effect in a multiferroic GdFeO3 single crystal

The magnetocaloric properties of single crystalline ${\mathrm{GdFeO}}_{3}$ have been investigated in the temperature range 2--36 K by magnetization and heat-capacity measurements. Remarkably large and reversible magnetic entropy change, $\mathrm{\ensuremath{\Delta}}{S}_{\mathrm{m}}=\ensuremath{-}52.5$ J/kg K, has been observed for a field change of 0--9 T. The adiabatic temperature change, $\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{ad}}$, is also found to be very large, 22 K, slightly above the antiferromagnetic ordering temperature (${T}_{N}^{\text{Gd}}=2.5$ K) of the ${\mathrm{Gd}}^{3+}$ moment, for a field change of 0--8 T. These magnetocaloric parameters remain large down to the lowest temperature measured and are significantly larger than that reported for the other members of rare-earth ($R$) orthoferrites ($R{\mathrm{FeO}}_{3}$) and several potential magnetic refrigerants in the same temperature range. Both $\mathrm{\ensuremath{\Delta}}{S}_{\mathrm{m}}$ and $\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{ad}}$ are also quite large for a small field change. The large values of magnetocaloric parameters suggest that ${\mathrm{GdFeO}}_{3}$ could be considered as a potential refrigerant in low-temperature magnetic refrigeration technology, such as liquefaction of hydrogen in the fuel industry. Moreover, ${\mathrm{GdFeO}}_{3}$ has very low electrical conductivity and exhibits no thermal and field hysteresis in magnetization, fulfilling the necessary conditions for a good magnetic refrigerant.

A novel hydrogen liquefaction process configuration with combined mixed refrigerant systems

A novel large-scale plant for hydrogen liquefying is proposed and analyzed. The liquid hydrogen production rate of the proposed plant is 100 tons per day to provide the required LH2 for a large urban area with 100,000–200,000 hydrogen vehicles supply. In the pre-cooling section of the process, a new mixed refrigerant (MR) refrigeration cycle, combined with a Joule–Brayton refrigeration cycle, precool gaseous hydrogen feed from 25 °C to the temperature −198.2 °C. A new refrigeration system with six simple Linde–Hampson cascade cycles cools low-temperature gaseous hydrogen from −198.2 °C to temperature −252.2 °C. The process specific energy consumption (SEC) is 7.69kWh/kgLH2 which minimum value is 2.89kWh/kgLH2 in ideal conditions. The exergy efficiency of the system is 39.5%, which is considerably higher than the existing hydrogen liquefier plants around the world. However, assuming more efficiency values for the equipment can improve it. The energy analysis specifies that coefficient of performance (COP) of the process is 0.1710 which is a high quantity of its kind between other similar processes. Effect of various refrigerant components concentration, discharge pressure of the high pressure compressors of the pre-cooling section, and hydrogen feed pressure on the process COP, exergy efficiency, and SEC are investigated. After that, a new MR will be offered for the cryogenic section of the plant. The system improvements are considerable comparing to current hydrogen liquefying plants, therefore, the proposed conceptual system can be used for future hydrogen liquefaction plants design.

Magnetocaloric properties and Landau theory of Dy0.5(Sr1−xCax)0.5MnO3 (0 ≤ x ≤ 0.3) manganites at cryogenic temperatures

Magnetic entropy change of Dy0.5(Sr1−xCax)0.5MnO3 nanoparticles (0≤x≤0.3) was analyzed at low temperatures to investigate the magnetic refrigeration as a promising tool for hydrogen liquefaction. These samples depict interesting values of maximum magnetic entropy change and large relative cooling power, especially for x=0.3 sample (about 169J/Kg). It could be a promising candidate for magnetic refrigeration at cryogenic temperatures. Landau theory presents a discord between the experimental magnetic entropy change and the theoretical one. This disagreement is tending to be in accordance as Ca substitution is increasing and also with augmenting the applied magnetic field.

Process optimization for large-scale hydrogen liquefaction

The investment in the hydrogen infrastructure for hydrogen mobility has lately seen a significant acceleration. The demand for energy and cost efficient hydrogen liquefaction processes has also increased steadily. A significant scale-up in liquid hydrogen (LH2) production capacity from today's typical 5–10 metric tons per day (tpd) LH2 is predicted for the next decade. For hydrogen liquefaction, the future target for the specific energy consumption is set to 6 kWh per kg LH2 and requires a reduction of up to 40% compared to conventional 5 tpd LH2 liquefiers. Efficiency improvements, however, are limited by the required plant capital costs, technological risks and process complexity. The aim of this paper is the reduction of the specific costs for hydrogen liquefaction, including plant capital and operating expenses, through process optimization. The paper outlines a novel approach to process development for large-scale hydrogen liquefaction. The presented liquefier simulation and cost estimation model is coupled to a process optimizer with specific energy consumption and specific liquefaction costs as objective functions. A design optimization is undertaken for newly developed hydrogen liquefaction concepts, for plant capacities between 25 tpd and 100 tpd LH2 with different precooling configurations and a sensitivity in the electricity costs. Compared to a 5 tpd LH2 plant, the optimized specific liquefaction costs for a 25 tpd LH2 liquefier are reduced by about 50%. The high-pressure hydrogen cycle with a mixed-refrigerant precooling cycle is selected as preferred liquefaction process for a cost-optimized 100 tpd LH2 plant design. A specific energy consumption below 6 kWh per kg LH2 can be achieved while reducing the specific liquefaction costs by 67% compared to 5 tpd LH2 plants. The cost targets for hydrogen refuelling and mobility can be reached with a liquid hydrogen distribution and the herewith presented cost-optimized large-scale liquefaction plant concepts.

Analysis and assessment of a novel hydrogen liquefaction process

In the present study, a novel supercritical hydrogen liquefaction process based on helium cooled hydrogen liquefaction cycles to produce liquid hydrogen is thermodynamically analyzed and assessed. The exergy analysis approach is used to study the exergy destruction rates in each component and the process efficiency. The energy and exergy efficiencies of liquefaction process are found to be 70.12% and 57.13%, respectively. In addition, to investigate the process efficiency more comprehensively to see how it is affected by varying process parameters and operating conditions, some parametric studies are undertaken to examine the impacts of different design variables on the energy efficiency, exergy efficiency and exergy destruction rates of the hydrogen liquefaction process. The results show that the increases in the cycle pressure of hydrogen and helium result in increasing hydrogen liquefaction process exergy efficiency and providing a smaller pinch point temperature difference of catalyst beds related with the heat transfer surface area and more efficiently process.

Introducing and energy analysis of a novel cryogenic hydrogen liquefaction process configuration

A novel efficient hydrogen liquefaction process is introduced and analyzed. Two independent refrigeration cycles with different mixed refrigerants (MR) are used in the process which can produce 300 tons liquid hydrogen per day. The proposed process liquefies a feed of 3.450 kg s−1 normal hydrogen gaseous at 25 °C and 21 bar to equilibrium temperature (−195 °C) by the first refrigeration cycle with power consumption of 1.102 kWh/kgLH2. In the second refrigeration cycle, the hydrogen is cooled to −253 °C with power consumption of 3.258 kWh/kgLH2, enjoying the least total power consumption compared to the identical liquefaction plants. Thermal design of the heat exchangers and expanders at wide range of temperature and using innovative and appropriate mixed refrigerants according to the configuration are novel aspects of the proposed process. Also, composition of the first and second refrigeration cycles' refrigerants is another novelty of the proposed process. Energy and exergy analyses of the proposed process are investigated. The energy analysis reveals that coefficient of performance of the proposed process is 0.1797 which is considerably higher than the other identical processes. According to the results of the exergy analysis, exergy efficiency of the first refrigeration cycle, second refrigeration cycle and the whole liquefaction process are 67.53%, 52.24% and 55.47%, respectively.

Roadmap to economically viable hydrogen liquefaction

The distribution of hydrogen in liquid state has several advantages because of its higher volumetric density compared to compressed hydrogen gas. The demand for liquid hydrogen (LH2), particularly driven by clean fuel cell applications, is expected to rise in the near future. Large-scale hydrogen liquefaction plants will play a major role within the hydrogen supply chain. The barriers of built hydrogen liquefiers is the low exergy efficiency and the high specific liquefaction costs. Exergy efficiency improvements, however, are limited by economic viability. The focus of this paper is to present a roadmap for the scale-up of hydrogen liquefaction technology, from state-of-the-art plants to newly developed large-scale liquefaction processes. The work is aimed at reducing the specific liquefaction costs by finding an optimal trade-off between capital costs and operating costs. To this end, two developed hydrogen liquefaction processes were optimized for specific energy consumption and specific liquefaction costs, showing the potential to reduce the specific liquefaction costs by 67% for a 100 tpd LH2 plant compared to a conventional 5 tpd LH2 plant while achieving a specific energy consumption between 5.9 and 6.6 kWh per kg LH2 with technology that is or will be available within 5 years. The results make liquid hydrogen a viable distribution route for hydrogen for mobility.

Economically viable large-scale hydrogen liquefaction

The liquid hydrogen demand, particularly driven by clean energy applications, will rise in the near future. As industrial large scale liquefiers will play a major role within the hydrogen supply chain, production capacity will have to increase by a multiple of today’s typical sizes. The main goal is to reduce the total cost of ownership for these plants by increasing energy efficiency with innovative and simple process designs, optimized in capital expenditure. New concepts must ensure a manageable plant complexity and flexible operability. In the phase of process development and selection, a dimensioning of key equipment for large scale liquefiers, such as turbines and compressors as well as heat exchangers, must be performed iteratively to ensure technological feasibility and maturity. Further critical aspects related to hydrogen liquefaction, e.g. fluid properties, ortho-para hydrogen conversion, and coldbox configuration, must be analysed in detail. This paper provides an overview on the approach, challenges and preliminary results in the development of efficient as well as economically viable concepts for large-scale hydrogen liquefaction.

Helium refrigeration system for hydrogen liquefaction applications

Liquid hydrogen around 20 K is used as cold moderator for generating “cold neutron beam” in nuclear research reactors. A cryogenic helium refrigeration system is the core upon which such hydrogen liquefaction applications are built. A thermodynamic process based on reversed Brayton cycle with two stage expansion using high speed cryogenic turboexpanders (TEX) along with a pair of compact high effectiveness process heat exchangers (HX), is well suited for such applications. An existing helium refrigeration system, which had earlier demonstrated a refrigeration capacity of 470 W at around 20 K, is modified based on past operational experiences and newer application requirements. Modifications include addition of a new heat exchanger to simulate cryogenic process load and two other heat exchangers for controlling the temperatures of helium streams leading out to the application system. To incorporate these changes, cryogenic piping inside the cold box is suitably modified. This paper presents process simulation, sizing of new heat exchangers as well as fabrication aspects of the modified cryogenic process piping.

Advanced exergy and exergoeconomic analyses of a hydrogen liquefaction plant equipped with mixed refrigerant system

Advanced exergy and exergoeconomic analyses are applied to a hydrogen liquefaction process. These analyses provide information about the origin of irreversibility and also determine the amount of avoidable irreversibility of the system. Results of the advanced exergy analysis show that in all components except turbo expanders, most of the irreversibility is due to the endogenous exergy destruction. It also indicates that most of the exergy destruction is unavoidable, but there is still a huge potential to improve the performance of the system. Results of advanced exergoeconomic analysis reveal that in terms of avoidable endogenous exergy destruction cost rate, HE-5 and HE-3 heat exchangers should be modified first, because their avoidable endogenous exergy destruction cost rate is higher than that of other components. Also, based on advanced exergoeconomic results, three different strategies are suggested to improve the performance of the components. Finally, a sensitivity analysis is performed on the key parameters of the system to show their effects on the exergoeconomic performance of the plant.

Japanese consortium plans largest hydrogen energy system so far

A joint proposal by Toshiba, Tohoku Electric Power, and Iwatani to develop hydrogen energy system technologies has been selected for funding by Japan's New Energy and Industrial Technology Development Organization (NEDO). The partners will investigate the configuration and specifications of a hydrogen energy system for what is expected to be the world's largest hydrogen production system, including all processes from hydrogen storage and liquefaction to transportation and utilisation.

Large magnetocaloric effect in sintered ferromagnetic EuS

We present magnetocaloric effect measurements of the ferromagnetic semiconductor EuS in the vicinity of its ordering temperature. Single phase EuS powder was synthesized by CS2 gas sulfurization of Eu2O3. A sintered compact with relative density over 95% was prepared by pulsed electric current sintering of the powder. Temperature and magnetic field dependence of the magnetization and specific heat were characteristic of a paramagnetic to ferromagnetic second order phase transition. The entropy change induced by an external magnetic field and the specific heat were both close to those of a single crystal. We obtained an entropy-temperature (S–T) diagram of the EuS sintered compact. Carnot cycle liquefaction of hydrogen using EuS was compared with several other materials, with results indicating that sintered EuS is an excellent magnetic refrigerant for hydrogen liquefaction.

Geothermal energy use in absorption precooling for Claude hydrogen liquefaction cycle

We propose an integrated system that consists of an ammonia-water absorption refrigeration cycle for the precooling of hydrogen, and the Claude cycle for the liquefaction of hydrogen. Geothermal energy supplies heat to the generator of the absorption system. A liquid geothermal source available at 200 °C at a rate of 100 kg/s is considered. The system is analyzed thermodynamically by the first and second laws using appropriate performance parameters. Under realistic operating conditions 39,080 kW heat can be supplied by geothermal water in the absorption refrigeration system. Hydrogen gas can be cooled to −26.9 °C at a rate of 29.53 kg/s in the absorption unit. The coefficient of performance (COP) of the ammonia-water refrigeration system is determined to be 0.556 with an exergy efficiency of 67.0%. The COP of the Claude liquefaction system is 0.0120 and its exergy efficiency is 67.3%. For the overall system, the COP and exergy efficiency are 0.162 and 67.9%, respectively. Also, precooling hydrogen gas in an absorption refrigeration cycle powered by geothermal heat decreases the work consumption in the liquefaction process by 25.4%.

Thermodynamic modeling of a nuclear energy based integrated system for hydrogen production and liquefaction

A nuclear based integrated system for hydrogen production and liquefaction with a newly developed four-step magnesium–chlorine cycle is proposed. The system uses nuclear energy to supply heat for the Rankine cycle and Mg–Cl cycle, where the power produced by the Rankine cycle is used to run the electrolysis steps of the Mg–Cl cycle and liquefaction cycle compressors. The four-step Mg–Cl cycle is specifically designed to decrease the electrical work consumption of the cycle by capturing HCl in dry form with an additional step to conventional three-step cycle. A performance assessment study is undertaken based on energy and exergy analysis of the subsystems, and total energy and exergy efficiencies of the plant are found to be 18.6%, and 31.35%. The comparisons of the subsystem efficiencies and total exergy destructions show that highest irreversibility ratio belongs to the Mg–Cl cycle by 41%, respectively.