In this paper, the attractions of hydrogen as a transmission and storage medium were discussed. It could be observed that while these attractions are still true in principle, many extraneous events have conspired to delay the widespread introduction of hydrogen- based energy systems, irrespective of whether the hydrogen is to be produced from fossil fuels or from renewables.
Chief among these events have been the demise of nuclear energy programs, and the discovery of far more petroleum and natural gas than was foreseen in the s [ 86 ] [ 87 ] [ 88 ] [ 89 ] [ 90 ]. There are several reasons for this, namely:. A gas turbine of the type typically used in a CCGT station is shown in a dismantled state in Figure 3. The maintenance workers provide a clear indication of the size of the turbine. Other factors that bear indirectly on the situation are the widespread privatization of electricity utilities and the general imperative of short-term profitability that now pervades industry.
In fact, from the viewpoint of the original concept of promoting efficiency and lowering the price of electricity, the de-regulation of electricity markets has certainly been a success. In the long term, however, problems loom large and arise from the fact that private companies tend to focus on short-term return and have little interest in making investments that will not show a profit for many years nor does the national interest enter much into this calculation.
Quite simply, there is as yet no economic case for hydrogen energy and the time-scale on which it may become affordable is uncertain. Despite all these difficulties, however, interest in hydrogen energy and, of course, its production, distribution, storage, etc.
Many industrial companies, as well as government and academia, are becoming involved in these matters. Figure 3. Dismantled gas turbine from CCGT power station. Scholarly Community. Submitted successfully! Thank you for your contribution!
Check Note. Read Edit History Comment Lists. Table of Contents. Topic review. Subjects: Others. View times: Introduction In a previous paper [ 1 ] , it has been shown that hydrogen is the ideal fuel from ecological viewpoint. The attractions of hydrogen as a storage medium are: it is universally available in the form of water, from which it may be extracted conveniently by electrolysis; it may be transmitted over long distances in buried pipelines, which are cheaper to construct and operate than electricity grids, and have no visual impact; the gas in the pipeline provides a storage component within the electricity supply system; hydrogen is the ideal fuel for use in fuel cells to generate electricity; hydrogen is oxidized cleanly to water, therefore the cycle is closed and no significant pollutants are Hydrogen can be transported in pipelines similar to natural gas.
The minimum power P required to pump a gas trough a pipe is given by 1 where is the length of the pipe, the velocity and the dynamic viscosity of the gas. Gaseous Hydrogen In principle, hydrogen is an ideal vector for the transmission and storage of energy [ 6 ] [ 7 ] [ 8 ]. Metal Hydrides An alternative storage procedure, which is much better matched to the likely scale of solar energy installations or hydrogen-fuelled road vehicles, is to store hydrogen in the solid state as a metal hydride [ 36 ] [ 37 ] [ 38 ] [ 39 ] [ 40 ].
Dissociation pressure of various metal hydrides A great many alloys have been screened for hydrogen storage with respect to the allowing criteria: i reversible hydrogen capacity; ii ease of initial activation of the alloy; operating pressure-temperature range van't Hoff plots ; iv reaction kinetics; v stability on repeated cycling of hydrogen; and vi One of the first metal hydrides to be studied was LaNi5, which takes up hydrogen reversibly from LaNi5H6.
Chemical and Related Storage Organic liquids such as cyclohexane, can serve as chemical carriers of hydrogen. Schematic representation of a carbon nanofibres; b single- and multi-walled carbon nanotubes; and c electron micrograph of bundles of carbon nanotubes 6. Hydrogen Storage on Road Vehicles As seen above, the four main options for hydrogen storage in transportation applications are: compressed gas, liquid hydrogen, metal hydride, chemical carrier at present, it is considered unlikely that nanostructured materials can accommodate the required amount of hydrogen.
Conclusion In this paper, the attractions of hydrogen as a transmission and storage medium were discussed.
There are several reasons for this, namely: the discovery and exploitation of major new gas fields; the cleanliness of natural gas as a fuel; the development of high-efficiency combined-cycle gas turbines CCGTs ; the construction of pipelines and liquefied natural gas carriers to convey the gas to market [ 90 ] [ 91 ].
References Sequeira, C. Hydrogen, the ultimate clean fuel. Sequeira, C. Mitigation and Adaptation Strategies for Global Change , 12 3 , Najibi, H. Damen, K. Hydrogen Energy , 32 18 , Omura, T.
Ipsakis, D. Hydrogen Energy , 34 16 , Dryer, F. Shinnar, R. Verykios, X. Hydrogen Energy , 28 10 , Bockris, J. Hydrogen Energy, 27 , Ogden, J. Evans, D. Krasae-In, S. Hydrogen Energy , 36 1 , Krasae-in, S. Hydrogen Energy , 35 10 , Wetzel, F. Hydrogen Energy , 23 5 , Schmidtchen, U. Peschka, W. Hydrogen Energy , 9 6 , Hydrogen Energy , 7 8 , Nour, U. Aceves, S. Hydrogen Energy , 35 3 , Paggiaro, R. I: Thermodynamic analysis of adsorption vessels and comparison with liquid and compressed gas hydrogen storage, Int.
Hydrogen Energy , 35 2 , Wang, H. Meisner, G. Ahluwalia, R. Hydrogen Energy , 33 17 , Hu, Q. C , 5 , Hydrogen Energy , 31 15 , Sarkar, A. Hydrogen Energy , 30 8 , Hydrogen Energy , 25 11 , Hydrogen Energy , 23 7 , Hydrogen Energy , 23 1 , Chen, Y. Hydrogen Energy , 27, Key Engineering Materials , , Song, X. Materials Research ,18, Chen, Y; Sequeira, C. Hydrogen Energy , 28, Alloys Comp. Chen, Y; Chen, C. Nonferrous Met.
China , 13, Santos, D. Defect Diffus. Forum , , Today , , Acta , 55, Metin, D. Mesoporous graphitic carbon nitride-supported binary MPt M;Co;Ni;Cu nanoalloys as electrocatalysts for borohydride oxidation and hydrogen evolution reaction.
Catalysis Today, , , Cardoso, C. Bateman, J. Barker, E. Abbey, D. Santos, Electroreduction ability of organoborohydride compounds. Electrochemical Society, , , M1-M7.
Martins, B. Metin, M. Erdem, T. Sener, D. Biobased carbon-supported palladium electrocatalysts for borohydride fuel cells. Hydrogen Energy, , 41, Santos, C. Analytical monitoring of sodium borohydride. Analytical Methods, , 5 4 , Manganese dioxide electrocatalysts for borohydride fuel cell cathodes.
Santos, T. Gomes, B. Sousa, C. Sequeira, F. Acta, , , Chen, D. Sequeira, Metal hydrides for hydrogen storage and distribution. Cardoso, B. Figueiredo, D. On the stability in alkaline conditions and electrochemical performance of A2BO4 — type cathodes for liquid fuel cells. Klontzas, E. Other applications use hydrogen as a reducing agent eg in glassworks to minimise oxidation potential which again, would not need to be of a high purity. Delivering high purity and very high purity hydrogen in cylinders has been commonplace for decades, and this is likely to remain a market for some time into the future.
This would avoid the costly and unnecessary removal of these species at low partial pressures from the bulk gas, and could bring closer the move toward a hydrogen-based economy. But what about fuel cell applications requiring a higher purity grade? It is very probable that pure hydrogen, introduced into pipes previously used for natural gas repurposing , will, at the required levels in the ppmv parts per million by volume range, pick up sufficient impurities to require pre-treatment before use in a fuel cell anyway.
Hence pipeline transportation of bulk hydrogen becomes a distinct possibility, even using existing infrastructure. Hydrogen is a compressible gas, but because of the small molecular mass, centrifugal designs are not ideal, as they need to operate at tip speeds three times faster than that of natural gas compressors to achieve the same compression ratio.
Hence positive displacement reciprocating compressors are often preferred, particularly where higher pressures are required. Positive displacement compressors can be reciprocating or rotary. Rotary compressors compress through the rotation of gears, lobes, screws, vanes, or rollers. Reciprocating or piston compressors use a motor, sometimes with a linear drive, to move a piston or a diaphragm back and forth.
This motion compresses the hydrogen by reducing the volume it occupies. These compressors can be large, heavy pieces of equipment. Figure 3 shows a mm stroke RPM compressor, taking hydrogen at 30 barg and delivering it at 50 barg. The motor power is 3. Ionic compressors are similar to reciprocating compressors but use ionic liquids in place of the piston.
These compressors do not require bearings and seals, two of the common sources of failure in reciprocating compressors. As a rule of thumb, hydrogen compression will require about 2. Higher compression without energy recovery will mean that even more energy will be lost during the compression step. The answer, where possible, is to compress the source chemicals upstream water in electrolysers, natural gas in autothermal reformers etc.
High purity hydrogen has been transported for a long time. Developing applications, like fuel cell vehicles have served to stimulate innovation to overcome perceived obstacles. The transition to a hydrogen-based economy will require bulk transport: this is not without its difficulties, but none of these seem insurmountable, and can draw significantly on the custom and practice of the natural gas industries.
This is the sixth article in a series discussing the challenges and opportunities of the hydrogen economy, developed in partnership with IChemE's Clean Energy Special Interest Group.
For more entries visit the series hub. European Industrial Gases Association doc. Catch up on the latest news, views and jobs from The Chemical Engineer.
Below are the four latest issues. First, a large surface area for the heat exchangers is required, and it will add weight and volume; if waste heat is not available at the needed temperature and rate, a significant fraction of the fuel energy will be wasted. This also means that the fuel cell must operate at a higher temperature than the desorption temperature for hydrogen.
This relationship suggests that important research is needed either to raise the fuel cell operation temperature or to lower the H 2 desorption temperature. New materials concepts have an important role to play in finding a solution for the hydrogen release problem. Heat management during uptake and release is a critical area requiring attention. Device designs that can load vehicles in an acceptable time with fail-safe safety controls and then release hydrogen at the rates demanded are vital to the success of this approach.
The committee views these areas, although still in their infancy, as very important. In summary, the committee questions the use of high-pressure tanks aboard mass-marketed private passenger vehicles from cost, safety, and convenience perspectives. The committee is also concerned about the complexity and capital intensity of the filling station equipment. The committee has a similar view of the use of liquid hydrogen. Exploratory budgets for the development of dense-phase materials as hydrogen carriers are being expanded, as mentioned above, but goals for this research need to be sharpened toward the objective of focusing on a few options that have real promise, and then on accelerated early-stage development.
Without such a commitment to show encouraging progress in this critical area, private sector enthusiasm toward the development of fuel-cell-powered light-duty vehicles could wane substantially. The preceding discussion is based on the assumption that the cost and safety problems associated with transportation, distribution, and on- and off-vehicle storage can be satisfactorily solved with molecular hydrogen at every stage of its scale of use, and that there is no better approach available.
Energy densities for compressed hydrogen are at pressures of 10, psi. Here again, narrowing the field as quickly as possible to focus on those few prospects with the most potential is a vital component of any research investment strategy.
All alternatives to molecular hydrogen relate to the manufacture of energetic metals or their hydrides, which, when reacted with water, emit hydrogen Thomas, These materials would be shipped from centralized manufacturing sites by conventional truck, rail, or ship and distributed to consumer fuel cell vehicle filling facilities. Vehicles would be equipped with devices for reacting the compounds with water in order to generate fuel-cell-quality hydrogen and for storing the waste reactants.
Waste would then need to be recycled or disposed of in an environmentally acceptable manner. The principal game-changing features of these materials are the elimination of most safety and cost issues that high-pressure or cryogenically liquefied molecular hydrogen has, and the possibility of a major safety and range enhancement for on-board storage of hydrogen.
Several small-vehicle demonstrations of the efficacy of this approach and its ability to provide acceptable driving range, hydrogen purity, and delivery rate and vehicle space efficiency have been successfully made Bak, The use of 20 to 30 percent by weight of alkali-stabilized aqueous solution of sodium borohydride as fuel, which is pumped over a catalyst to generate hydrogen instantaneously, was demonstrated recently by DaimlerChrysler in its Chrysler Town and Country Natrium fuel cell minivan vehicle.
The principal current shortcomings of these chemical methods for generating hydrogen are the high cost of manufacture of the chemicals and the not-yet-demonstrated technology for recycling or disposing of waste products effectively. Secondary issues include catalyst longevity over the vehicle life, fuel stability on board the vehicle, and the ability to meet automotive range and reliability requirements. However, all of these shortcomings, with the exception of the cost of recycling and initial manufacture, have had encouraging real-world demonstrations in full-sized passenger vehicles, as for example with the Natrium fuel cell vehicle.
The committee believes that this is an important area for further research and that it should be pursued vigorously to find the best chemicals for this use and to improve the economics of their manufacture and regeneration. The DOE should also continue to encourage other game-changing concepts because of the pivotal importance of this need to the future of fuel-cell-powered vehicles.
The committee differs with the DOE on near-term priorities. The committee believes that the requested increased funding in these areas should be prioritized to strongly favor solid or dense-phase storage of hydrogen, especially for on-board vehicle use, since on-board storage appears to be one of the primary obstacles to fuel cell vehicle practicality, along with the needed fuel cell cost reduction and reliability improvements.
The following findings and recommendations are based on the idea that some research and technology investments are at present more important than others in criticality and in time. This prioritization reflects the need to invest in overcoming the technology gaps that might be major stumbling blocks to immediate progress and to delay or reduce investment in those activities that, while very important, can wait for several years because they are not critical to near-term progress.
Finding It seems likely that in the relatively near term the next 10 to 30 years , distributed rather than centralized production of hydrogen will be a driver for the continued expansion of fuel-cell-powered private vehicles. Distributed manufacture of molecular hydrogen seems most likely to be best done with small-scale natural gas reformers or by electrolysis of water.
At present both technologies are capital-intensive and relatively energy-inefficient. Without such distributed manufacture, it seems likely that the very large centralized production and pipeline distribution investments will be difficult to justify and could slow conversion to hydrogen markedly. Additional information is available online at www.
Accessed December 4, Recommendation Increased research and development investment in support of breakthrough approaches should be made in small-scale reformer and electrolyzer development with the aim of increasing efficiency and reducing capital costs. A related goal should be to increase the safety and reduce the capital intensity of local hydrogen storage and delivery systems, perhaps by incorporating part or all of these capabilities in the hydrogen-generating technologies.
It is clear that the vast majority of current private and governmental investments in the manufacture of hydrogen for fuel cell vehicles are aimed at the direct use of molecular hydrogen. Because of the inherent difficulties in the transportation, distribution, and storage of molecular hydrogen, it is apparent that other approaches for hydrogen generation may have advantages for transportation and for on- and off-board storage. The latter include compounds that, on reaction with water or some other reactant, generate hydrogen, and solid-state carriers that contain high concentrations of adsorbed or absorbed hydrogen that liberate the stored hydrogen through the application of heat.
Many possibilities exist in these categories, but few have received significant research support. The committee strongly supports the requested Department of Energy budget increases in the vital area of hydrogen storage. The committee believes, however, that major shifts in emphasis should be made immediately in order to make sure that the many new ideas currently available are properly examined—because without relatively near-term confidence by industry and government leaders, interest in continuing the pursuit of fuel cell vehicle transportation uses is likely to wane over time.
The Department of Energy should halt efforts on high-pressure tanks and cryogenic liquid storage for use on board the vehicle. The DOE should apply most if not all of its budgets to the new areas described in Finding with the objective of identifying as quickly as possible a relatively few, promising technologies.
Where relevant, efficient waste-recycling studies for the chemically bound approaches should be part of these studies. Even during this winnowing process the DOE should continue to elicit new concepts and ideas, because success in overcoming the major stumbling block of on-board storage is critical for the future of transportation use of fuel cells.
The evolution of the transportation and delivery and storage systems for hydrogen will transition several times as hydrogen demand increases over many decades. This would of necessity mean continuous and overlapping shifts from small-scale delivery and storage, to distributed manufacture and storage, to centralized production with extensive pipeline, distribution, and storage networks.
Such a complex evolution would likely benefit from systems analysis to help guide the optimum research and technology investment strategies for any given stage of the evolution and thus enable the most effective progress toward the long-term end states. Systems modeling for the hydrogen supply evolution should be started immediately, with the objective of helping guide research investments and priorities for the transportation, distribution, and storage of molecular hydrogen.
In addition, parallel analysis of the many alternatives for other means of supplying hydrogen to fuel-cell-powered facilities and vehicles should be performed; such analysis is needed to prevent wasteful expenditures and to help focus attention on viable technology that would potentially compete with the direct supply and delivery of molecular hydrogen and that might be useful for all or portions of the future hydrogen economy.
Hydrogen is particularly difficult to ship from a manufacturing site to filling facilities for vehicle servicing. In fact, the cost to ship and store can easily equal the costs of production. Particular concerns relate to the energy losses during compression and liquefaction and to the tendency of hydrogen to embrittle some current pipeline materials. Research and technology development should be carried out in support of novel concepts that promise major improvements in the cost and efficiency of compressors for molecular hydrogen and reductions in the cost of pipeline materials, valves, and other leak-prone components of its distribution system.
Initial research should focus on those components that are directly related to distributed hydrogen production. In later years, research should shift to components for large, centralized production plants with extensive pipeline and storage facilities. The committee believes that current Department of Energy plans call for research that relates primarily to centralized molecular hydrogen manufacture—a need that is many decades in the future—and consequently may shortchange other, more immediate needs.
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