Current situation and future development trend of hydrogen technology

5. Hydrogen production from renewable energy sources

In the hydrogen production route, the gradual transition from fossil energy to renewable energy hydrogen production, large-scale low-cost hydrogen is the key, the use of renewable energy hydrogen production technology has attracted much attention in recent years, research results and demonstration projects are also emerging (Table 1). "Renewable energy + hydrolysis hydrogen production" has great potential, green environmental protection, high value oxygen by-product, and can effectively absorb wind power, photovoltaic power generation and other instability, to achieve surplus trough energy storage, the future "renewable energy + hydrolysis hydrogen production" is expected to become a large-scale hydrogen production trend.

Three. Midstream storage and transportation of hydrogen

1.Hydrogen storage technology

At present, the main hydrogen storage materials and technologies are high-pressure gas hydrogen storage, liquid hydrogen storage, solid hydrogen storage and so on.

High pressure gas hydrogen storage: with the advantages of fast hydrogen charging and discharging speed, simple container structure, etc., it is the main hydrogen storage method at this stage, which is divided into two categories: high pressure hydrogen bottle and high pressure container. Among them, steel hydrogen cylinder and steel pressure vessel technology is the most mature, and the cost is low. The development and application of carbon fiber wound high pressure hydrogen cylinder has realized the transformation of high pressure gas hydrogen storage from stationary application to vehicle hydrogen storage application. At present, the most commonly used gaseous hydrogen storage tank is steel tank, and the future research focus is to use high-pressure lightweight composite tank and glass microsphere to store hydrogen.

The research focus of hydrogen storage in composite tank is: (1) Using new technology to study the mechanical properties of brittle materials; (2) Enhance material performance and reduce material cost, especially carbon fiber; (3) The development of efficient, clean (oil-free) 1000 bar compression tanks (practical hydride compression tanks using solar energy or waste heat can be considered); (4) Technology for recovering compressed energy during vehicle operation.

The research and development of hydrogen storage in glass microspheres focuses on: (1) developing glass microspheres with stronger performance; (2) Develop special low-cost production technology; (3) Develop coating technology with optimal hydrogen permeability; (4) Develop penetration control technology through other heating methods (e.g. magnetic, electrical, microwave).

Liquid hydrogen storage: can be divided into low temperature liquid hydrogen storage and organic liquid hydrogen storage, with high hydrogen storage density advantage. Low temperature liquid hydrogen storage cooling hydrogen to -253℃, liquefied storage in low temperature adiabatic liquid hydrogen tank, hydrogen storage density up to 70.6kg/m3, but the liquid hydrogen device one-time investment is large, high energy consumption in the liquefaction process. Domestic liquid hydrogen has been successfully used in space engineering. Organic liquid hydrogen storage uses some unsaturated organic compounds (such as olefins, alkynes or aromatic hydrocarbons) to perform reversible hydrogenation and dehydrogenation reactions with hydrogen to achieve hydrogen storage. The organic hydrides formed after hydrogenation have stable properties and high safety, and the storage mode is similar to that of petroleum products. However, there are some problems such as high reaction temperature, low dehydrogenation efficiency, and the catalyst has been poisoned by intermediate products. At present, the most promising storage methods for liquid hydrogen are: ultra-low temperature liquid hydrogen, NaBH4 solution and organic liquid.

The main research and development priorities of ultra-low temperature liquid hydrogen are: (1) the development of more efficient liquefaction methods (hydride compressors, magnetic and sonic cooling, etc.); (2) Reduce costs and improve insulated containers; (3) Develop automatic capture gasification fuel reliquefaction system.

The research and development focus of NaBH4 solution is (1) to study how to achieve the ideal energy density (10.9wt.%) by optimizing the water required for the reaction, and to develop methods for obtaining water from fuel cells; (2) To develop feasible NaBO2 transfer, regeneration and replacement methods; (3) Develop a direct borohydride fuel cell.

The research and development of organic liquids focuses on: (1) the development of organic systems that can dehydrogenate at low temperatures and produce hydrogen at feasible pressures; (2) To develop the best metal dehydrogenation catalysts and on-board systems; (3) Research and development of rehydrogenation process.

Solid hydrogen storage: metal hydride, chemical hydride or nanomaterials are used as hydrogen storage carriers, and hydrogen storage is achieved by chemical adsorption and physical adsorption. Solid hydrogen storage has the advantages of high hydrogen storage density, low hydrogen storage pressure, good safety and high purity of hydrogen discharge, and its volume storage density is higher than that of liquid hydrogen. However, the hydrogen storage rate in the mainstream metal hydrogen storage materials is still lower than 3.8wt%, and the lightweight hydrogen storage materials with a weight hydrogen storage rate greater than 7wt% still need to solve the problems of high hydrogen absorption and discharge temperature and poor cycling performance. Foreign solid-state hydrogen storage has been commercially applied in fuel cell submarines, demonstrated in distributed power generation and wind power hydrogen storage scale, and domestic solid-state hydrogen storage has been demonstrated in distributed power generation.