The development trend of hydrogen energy

1. Fuel cells

1.1 Fuel cell technology

Fuel cell is an important way to utilize hydrogen energy efficiently. The principle of hydrogen fuel cell is to convert chemical energy into electricity and heat energy when hydrogen and oxygen are combined to generate water. The process is not limited by the Carnot cycle effect, and the theoretical efficiency can reach more than 90%, which has a high economy. There is a tough diaphragm between the anode and cathode of the fuel cell to isolate hydrogen and oxygen, which effectively avoids the danger of combustion and explosion caused by direct contact between hydrogen and oxygen. Hydrogen enters the anode of the fuel cell and is broken down into hydrogen ions and electrons by the action of a catalyst. Then, hydrogen ions pass through the diaphragm to the cathode, where they combine with oxygen to form water under the action of a catalyst, and electrons move through an external circuit to the cathode to form an electric current.

At present, fuel cell technology mainly includes alkaline fuel cell, phosphate fuel cell, solid oxide fuel cell, molten carbonate fuel cell and proton exchange membrane fuel cell. From the commercial application point of view, molten carbonate fuel cells, proton exchange membrane fuel cells and solid oxide fuel cells are the most important three technical routes. Among them, proton exchange membrane fuel cell due to its low operating temperature, fast start-up, high specific power advantages, very suitable for application in the field of transportation and fixed power supply, and gradually become the mainstream application technology at home and abroad at present. Solid oxide fuel cell has the advantages of wide fuel adaptability, high energy conversion efficiency, all-solid state, modular assembly, zero pollution, etc., and is commonly used as a fixed power station in the field of large-scale centralized power supply, medium-sized power distribution and small household cogeneration. China mainly focuses on research and development and industrialization in the field of proton exchange membrane fuel cells and solid oxide fuel cells.

Since the launch of the "Tenth Five-Year Plan" major science and technology special project for new energy vehicles, with the support of a series of major national projects, fuel cell technology has made certain progress, and has initially mastered core technologies such as fuel cell stacks and key materials, power systems and core components, and vehicle integration; The level of some key technology laboratories is close to the international advanced level, but the level of engineering and industrialization lags behind, and the overall technical level lags behind Japan, South Korea and other countries. Specifically, with the gradual promotion of terminal applications of proton exchange membrane fuel cells, membrane electrodes, bipolar plates, proton exchange membranes, etc., have the ability to be localized, but the production scale is small; The development of the reactor industry is good, but the development of the key components industry of the auxiliary system is relatively backward; The system and vehicle industry has developed well, with more supporting manufacturers and larger production scale, but most of them use imported parts from abroad, and the degree of external dependence is high.

1.2 Fuel cell applications

With the continuous maturity of fuel cell technology, related products have gradually entered the stage of commercial application, and are gradually applied to automobiles, ships, rail transit, etc., in the field of transportation, which can reduce the dependence on foreign energy and the emission of fossil energy pollutants and carbon. Fuel cell commercial vehicles take the lead in commercial application, the future lithium battery and fuel cell will become complementary relationship, Academician Ouyang Ming Gao has proposed that "lithium ion battery is more suitable for replacing gasoline engine, hydrogen fuel cell system is more suitable for replacing diesel engine". Compared with pure electric vehicles and gasoline vehicles, hydrogen fuel cell vehicles are not dominant in acquisition costs and use costs, and the future with the increase in application, vehicle costs and hydrogen costs are expected to decrease significantly, and domestic technology still has a lot of room for improvement.

Five. Future development trend

Low-carbon and clean hydrogen has become an important starting point for achieving carbon neutrality.

The national hydrogen production technology route focuses on project demonstration and industrial layout around renewable energy electrolytic water hydrogen production technology and fossil energy hydrogen production +CCUS (carbon capture, utilization and storage) technology. In addition, for fuel cell vehicle terminal application scenarios, hydrogen purification and hydrogen quality research work are carried out to ensure high-quality hydrogen supply. There is a large gap between China's CCUS technology integration, submarine storage and industrial application and the international advanced level, and the number and overall scale of CCUS large-scale demonstration projects are far lower than that of developed countries.

In terms of hydrogen purification technology, the United States and Japan, based on their national energy structure and technological advantages, respectively focused on small natural gas reforming hydrogen production scenario, ammonia decomposition reforming hydrogen production scenario, organic liquid hydrogen analysis scenario, and carried out research on hydrogen purification technology for fuel cell vehicles, including high-efficiency small pressure swing adsorption technology, organic membrane separation, inorganic membrane separation and all-palladium membrane separation technology. China has a wide range of hydrogen sources, especially the by-product gas impurity types and wide content distribution, a single purification technology route is difficult to meet the actual needs. Especially in the field of hydrogen purification for fuel cell vehicles, China started late and lacks systematic research.

In terms of hydrogen storage technology, at present, China's research on hydrogen storage materials is relatively active, and the research content involves the main aspects of current international hydrogen storage technology research and development, such as high-pressure hydrogen storage, carbon nanotube hydrogen storage, new alloy hydrogen storage, organic compound hydrogen storage, carbon gel hydrogen storage, glass microsphere hydrogen storage, hydrogen slurry hydrogen storage, and layered compound hydrogen storage. It has advantages in hydrogen storage of metal hydrides, carbon nanotubes and complex compounds.

Strengthen research and development of hydrogen fuel cell technology and hydrogen fuel cell vehicles and related infrastructure. An important aspect of developing hydrogen economy is the development of hydrogen energy transportation system and hydrogen energy infrastructure construction. In terms of hydrogen fuel cells, China can focus on the development of: high-power proton exchange membrane fuel cell technology, medium and low temperature solid oxide fuel cell technology, fuel cell-based system integration technology, proton exchange membrane technology, electrocatalyst technology, advanced membrane electrode module technology, platinum-free catalyst technology.

2. Major national needs and key technologies

In the national key research and development plan "Hydrogen Technology" key special Project 2021 Annual Declaration Guide ", adhere to the principles of problem-oriented, step-by-step implementation and prominent focus, focusing on four technical directions such as hydrogen green production and scale transfer storage system, hydrogen energy safe storage and rapid transmission and distribution system, hydrogen energy convenient transformation and efficient power system, and "hydrogen into 10,000" comprehensive demonstration. In accordance with basic frontier technologies, common key technologies and demonstration applications, 18 projects will be launched, and 795 million yuan will be allocated by the state. Among them, a young scientist project is planned to be deployed around the technical direction of hydrogen energy safe storage and rapid transmission and distribution system.

Hydrogen energy is an important part of China's modern energy system, and it is very important to build a low-carbon and clean hydrogen energy supply system. China Hydrogen Energy Alliance in the "China Hydrogen energy and Fuel cell Industry White Paper 2020" suggested: improve the low carbon clean hydrogen policy support system, hydrogenation low carbon clean hydrogen market construction, improve the level of low carbon clean hydrogen preparation technology independence, encourage electrolytic cell and CCUS (carbon capture, utilization and storage) and other low carbon clean hydrogen production technology application.