The fuel cell

The fuel cell

A fuel cell is an energy conversion device and does not store energy. Energy-carrying fuel and oxidant are continuously input into the fuel cell, converted into electrical energy through electrochemical reaction, and continuously discharged products. In this process, the electrode of the fuel cell does not change, and the battery only provides a place for electrochemical reaction. Therefore, the characteristic of the fuel cell is that as long as the fuel and oxidant can be continuously supplied, the fuel cell can continuously generate electricity, and the electrode will not be consumed.

The fuel cell directly converts the chemical energy of the chemical reaction into electrical energy, without going through the heat engine process, and not subject to the restriction of the Carnot cycle. Therefore, the energy conversion efficiency is high (conversion rate 40%~60%), and almost no nitrogen oxides and sulfur oxides are emitted, and CO2 emissions are also reduced by more than 40% compared with conventional power plants. It is precisely because of these outstanding advantages that the research and development of fuel cell technology is valued by governments and large companies in various countries. In some cities in North America and Europe, fuel cell-powered buses are in operation, and major automakers continue to showcase their fuel cell vehicles. Many hospitals, schools, office buildings, water treatment plants, etc. have also installed fuel cells. As a kind of power generation device, compared with the widely used heat engines (steam engines and internal combustion engines) and other power generation methods, fuel cells have the advantages of high efficiency, low pollution, low noise, wide application range, and flexibility.

There are different types of fuel cells, which can be divided into different categories according to different classification methods.

According to the different electrolytes used, it can be divided into: ① Alkaline fuel cell (AFC), generally using potassium hydroxide (KOH) as the electrolyte; ② Phosphoric acid fuel cell (PAFC), using concentrated phosphoric acid (H3PO4) as the electrolyte; ③ Proton exchange membrane fuel cell (PEMFC) uses sulfonic acid type proton exchange membrane as electrolyte; ④Molten carbonate fuel cell (MCFC), using molten lithium-potassium carbonate (Li2Co3·KCO3) or lithium-sodium carbonate (Li2Co3·NaCO3) as electrolyte; ⑤Solid oxide fuel cell (SOFC) uses solid oxide as the oxygen ion conductor, such as yttria-stabilized zirconia (ZrO3) as the electrolyte.

According to the working temperature, it can be divided into two types: high temperature and low temperature. Low-temperature fuel cells include AFC (working temperature at 100℃), PAFC (working temperature at 200℃), PEMFC (working temperature within 100℃) and so on. High-temperature fuel cells include MCFC (working temperature at 650℃), SOFC (working temperature at 1000℃), etc. Among them, high-temperature fuel cells are also known as fuel cells that can be jointly developed for high-quality exhaust.

The fuel cell
The fuel cell

Although fuel cells are limited by problems such as cost and volume, their applications in portable, stationary, and transportation fields have continued to expand due to their high conversion efficiency, environmental protection, and continuous operation. It is expected that with the improvement of technology and the decrease of cost, its application will show rapid development.

From a global perspective, data from the US Department of Energy show that in 2014, global fuel cell shipments exceeded 50,000 units, a year-on-year increase of 37%, and sales reached US$2.2 billion, a year-on-year increase of 69.2%. Among them, the market shares of portable, fixed, and transportation are 31.1%, 64.9%, and 4% respectively, and the fixed power supply market share is still the highest. The domestic fuel cell application market focuses on the transportation field, accounting for 74%, followed by the portable field with 16%, and the fixed field with 10%.

Fuel cells are developing towards high power, and transportation applications are expected to become the main thrust of the fuel cell explosion. Although fuel cell forklifts are growing rapidly in North America, there are fewer than 1,000 fuel cell electric vehicles in the world. The governments of Europe, the United States, Japan and other countries are vigorously supporting the production and research of fuel cell vehicles. Japan and South Korea are ahead of other countries in the production and research of fuel cell vehicles. Japan’s new energy strategy focuses on fuel cell vehicles, with the goal of reaching 5 million fuel cell vehicles by 2020 and the full popularity of fuel cell vehicles by 2030. Toyota, Honda, Hyundai and other automakers have all launched relevant models and proposed commercialization goals for fuel cell vehicles. It is expected that the global new fuel cell models will be intensively put on the market in the next two years, and the commercialization of fuel cell vehicles has begun to gradually promote.

From the perspective of China, the current supporting technologies are not yet mature enough. According to data released by the Ministry of Industry and Information Technology, the national output of fuel cell vehicles was only 10 in 2015. During the “Twelfth Five-Year Plan” period, the state mainly supported and promoted electric vehicles with lithium batteries as the core. The current development of fuel cells lags behind Japan and South Korea and other countries. At the beginning of the “13th Five-Year Plan”, the subsidy for fuel cells was increased from 180,000 yuan to 200,000 to 500,000 yuan, and the subsidy will not be retreated until 2020. Compared with the 20% decline faced by lithium battery electric vehicles, it shows the determination to develop fuel cell vehicles.

In the “Made in China 2025” planning outline, it is clearly defined to support the development of fuel cell vehicles and promote the development strategy of independent brand energy-saving and new energy vehicles in line with the international advanced level. Three development stages are proposed: The first is to gradually realize the localization of key materials and parts; the second is to gradually improve the performance of fuel cells and vehicles; the third is to expand the operation scale of fuel cell vehicles to 1,000 in 2020, and the supporting infrastructure for hydrogen production and refueling will be basically complete by 2025. In 2016, fuel cell vehicles received further national support. The ninth item in the “Energy Technology Revolution and Innovation Action Plan (2016-2030)” issued by the National Development and Reform Commission and the Energy Administration mentioned the innovation of hydrogen energy and fuel cells. Fuel cells have obtained a clear development direction, and it is planned to realize the large-scale promotion and application of fuel cells and hydrogen energy in 2030.