HYDROGEN PRODUCTION TECHNOLOGY
Electrolysis: The process of electrolysis consists of the decomposition of water using electricity. It is a process that is commercially available with proven technology. It is an industrial process known for a long time and therefore perfectly understood; it has the advantage that it is modular and can easily be adapted for small or large quantities of gas; The hydrogen obtained by this process has a high purity. Another advantage of electrolysis is its possible combination with renewable energies to produce H2 from renewable sources, compensating for the intermittent nature of some of these sources. It poses a direct competition with the direct use of renewable electricity: the energy generated is poured into the grid or used in electrolysis.
Reforming (stationary applications and vehicles): Consists of the reaction of hydrocarbons with heat and water vapor. It is also a generalized process on a large scale and allows to obtain a low cost hydrogen from natural gas. It raises opportunities to combine with large-scale CO2 fixation («carbon storage»). On the other hand, small-scale units are not commercial and hydrogen contains some impurities (in some applications it may be necessary to clean the gas or secondary reactions for the elimination of CO). CO2 emissions together with the CO2 fixation process, which generates additional costs, are the disadvantages that can be found in this process.
Gasification: Starting from heavy hydrocarbons and biomass, hydrogen and gases are formed for reforming through the reaction with water vapor and oxygen. Perfectly suited for large-scale heavy hydrocarbons, it can be used for solid fuels, such as coal, and liquids. It has some similarities with synthetic fuels derived from biomass – the biomass gasification in the demonstration phase. Small units are very scarce, since hydrogen usually requires substantial cleaning before use. The biomass gasification is still under investigation and has implications due to the use of large tracts of land. The hydrogen that would be obtained through this process comes into competition with synthetic fuels derived from biomass.
Thermochemical cycles that use inexpensive high temperature heat from concentrated nuclear or solar energy. This process would be potentially attractive for its large-scale application, with low cost, and without greenhouse gas emissions, for heavy industry or transportation. For this, there are different international collaboration projects (United States, Europe and Japan) on research, development and start-up of plants that operate with this process. Currently there is a need for more research and non-commercial developments on the process that can be extended over the next ten years: the topics being studied are materials, chemical technology, and the implementation of the high-temperature nuclear reactor (HTR).
Biological production: Algae and bacteria directly produce hydrogen under certain conditions. During the last years, this potential large-scale resource has been studied, although with a rather slow rate of hydrogen production. Large areas are needed and most of the appropriate organisms have not yet been found. Nowadays it is being studied in different research centers.
HYDROGEN STORAGE METHODS
Compressed gas cylinders: It is the most used technique to supply hydrogen up to pressures of 200 bar. It is a technique of general availability and can be considered low cost. Only relatively small amounts of H2 are stored at 200 bars; energy densities of fuel and storage at high pressure (700 bar) are comparable to liquid hydrogen, but are still below those of gasoline and diesel; High-pressure storage is still in the development phase.
Liquid tanks: It is also a well-used and well-known technology. A good storage density is achieved. Very low temperatures are required and therefore a greater than normal insulation, so its cost can be high. Some hydrogen is lost through evaporation and the stored energy is still not comparable to liquid fossil fuels.
Metallic hydrides: Some technology of storage of hydrogen on metallic solids is beginning to be available. It is a very safe system since hydrogen is stored on the solid. The shape of the storage tanks can be adapted to the needs of each application. The refilling requires cooling circuit due to the heat of the reaction, although there is the possibility of reusing the thermal effects in subsystems. When metals are used to fix the gas, the weights rise considerably and can degrade over time. Currently it is a quite expensive technology.
Chemical hydrides: Reversible hydride formation reactions are well known, p. eg, NaBH4. They are compact systems with small size but pose problems with the handling of waste and in what refers to the necessary infrastructures.
Carbon Structures: Different carbon-based structures are being studied, among which are the nanotubes, which allow a high density of hydrogen storage, being, in addition, very light. They can be cheap depending on their production, being currently in the research and development phase.
NECESSARY INFRASTRUCTURES FOR THE IMPLEMENTATION OF HYDROGEN TECHNOLOGY
Hydrogen transport: Depending on the specific circumstances, hydrogen can be produced locally or distributed from a large-scale central production plant. Currently, the costs and benefits of these various «driving» possibilities are being studied. In Europe there is already a restricted hydrogen transmission system associated with the petrochemical sector, but substantial investments in infrastructure will be necessary to facilitate the widespread distribution of hydrogen. In the case of transport, it will also be necessary to have special refueling facilities. As with all fuels, safety is the primary concern. For this reason, it will be necessary to elaborate norms, codes and regulations of generalized acceptance for the equipment, to have perfectly trained maintenance personnel and to have operational guidelines, as well as to carry out an extensive information and training program aimed at the general public.
Service stations: Hydrogenerators can obtain hydrogen by electrolysis of water with surplus renewable electric power from wind farms or solar panels installed as a cover for a public car park. The manufacture of hydrogen by electrolysis is the least efficient (yields of 15% to 25%), but once compressed and stored on the edge of the vehicle this hydrogen exceeds 75%. In contrast, when hydrogen is extracted from methane, the performance of this process is greater (up to 75%), but the overall yield assessing the entire process is around 48% or 60%. Therefore, hydrogen engines give a 55% performance compared to 30% achieved by internal combustion engines. In mid-2003, there is only the technology to manufacture hydrogen for small installations and it is exaggeratedly expensive. For example, an installation of about 10 kW can cost about 200,000 euros, instead a 250 kW cost is 750,000 euros.
The International Organization for Standardization (ISO) is the entity that elaborates most of the technical standards, with a network of national centers distributed throughout 146 countries. The ISO / TC 197 Technical Committee for hydrogen technologies was created in 1990. It involves 15 participating countries, 15 observers, and collaborates with 15 other ISO / IEC committees. Below are some of the rules published to date or currently under study. The committee works in conjunction with the United Nations Global Forum for the Standardization of Vehicle Regulations. The International Electrotechnical Commission (IEC) is the organization that prepares and publishes international regulations for all topics related to electricity, electronics and related technologies. His work serves as a basis for national standardization in different countries and as a reference in international relations.
ISO 13984:1999. Liquid hydrogen — Land vehicle fuelling system interface
ISO 13985:2006. Liquid hydrogen — Land vehicle fuel tanks
ISO 14687:1999. (ISO 14687:1999/Cor 1:2001, ISO 14687:1999/CD Cor 2). Hydrogen fuel — Product specification
ISO/PRF TS 14687-2. Hydrogen fuel — Product specification — Part 2: Proton exchange membrane (PEM) fuel cell applications for road vehicles
ISO/PAS 15594:2004. Airport hydrogen fuelling facility operations
ISO/DIS 15869.2. Gaseous hydrogen and hydrogen blends — Land vehicle fuel tanks
ISO/TR 15916:2004. Basic considerations for the safety of hydrogen systems
ISO 16110-1:2007. Hydrogen generators using fuel processing technologies — Part 1: Safety
ISO/CD 16110-2. Hydrogen generators using fuel processing technologies — Part 2: Procedures to determine efficiency
ISO/DIS 16111. Transportable gas storage devices — Hydrogen absorbed in reversible metal hydride
ISO/TS 16111:2006. Transportable gas storage devices — Hydrogen absorbed in reversible metal hydride
ISO 17268:2006. Compressed hydrogen surface vehicle refuelling connection devices
ISO/CD TS 20012. Gaseous hydrogen — Service stations
ISO/DIS 22734-1. Hydrogen generators using water electrolysis process — Part 1: Industrial and commercial applications
ISO/CD 22734-2. Hydrogen generators using water electrolysis process — Part 2: Residential applications
ISO/CD 26142. Hydrogen detector
The European legislation requires that European regulations be transferred to each of the member countries, for this reason, the standards developed by the European Committee for Standardization (CEN), by the European Committee for Electrotechnical Standardization (CENELEC) or by the European Institute of Telecommunication Standards (ETSI) are systematically incorporated into the AENOR catalog, reaching the category of national standards.
In Spain, the AEN / CTN 181 Standardization Technical Committee on Hydrogen Technologies of AENOR AENOR regulates the current regulations, adapting the standards approved at European level and collaborating with the international hydrogen standardization committee IEC / TC 197. Its field of activity encompasses the standardization of issues related to systems and devices for the production, storage, transportation and distribution, measurement and utilization of hydrogen, including hydrogen specifications; Hydrogen production facilities and their associated devices; Hydrogen storage facilities and their associated devices; Hydrogen transport facilities and their associated devices; Installations and apparatus using hydrogen; Hydrogen supply installations; Qualification of personnel involved in the construction, operation, maintenance and inspection of the production, storage, transportation, supply and use of hydrogen as fuel; Measurement of hydrogen. Some rules related to hydrogen are listed below.
UNE 26505:2004. Road vehicles. Liquid hydrogen Interface for power systems in land vehicles.
UNE-EN ISO 11114-4:2006. Bottles for transporting gas. Compatibility of the materials of the valve and the bottle with the contained gas. Part 4: Test methods for the selection of metallic materials resistant to embrittlement by hydrogen. (ISO 11114-4: 2005)
UNE-EN ISO 6974-3:2003. Natural gas. Determination of the composition with an uncertainty defined by gas chromatography. Part 3: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons up to C8 using two filler columns. (ISO 6974-3: 2000)
UNE-EN ISO 6974-6:2006. Natural gas. Determination of the composition with an uncertainty defined by gas chromatography. Part 6: Determination of the content of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons C1 to C 8 using three capillary columns. (ISO 6974-6: 2002).
UNE-ISO 14687:2006. Hydrogen as fuel. Product specifications. (ISO 14687: 1999 + ISO 14687: 1999 / Cor.1: 2001)
UNE-ISO/TR 15916:2007 IN. Basic safety considerations for hydrogen systems. (ISO / TR 15916: 2004)