Key technologies and development status of hydrogen energy utilization in the context of carbon neutrality

4. Ideas and cases of hydrogen energy utilization in Japan

Japan's power system is dominated by centralized generation, and the Fukushima nuclear accident has exposed the fragility of the current system. Due to the heavy dependence on overseas energy supplies and the stagnation of nuclear power development, Japan's energy self-sufficiency rate fell from 20% in 2010 to about 8% in 2016. The realization of a self-sufficient distributed energy system has become the direction of Japan's energy transition [38-39]. It has been considered an effective, economical and safe way to construct hydrogen energy supply system and use it near the place of consumption. Especially for Japan, which is prone to natural disasters, the multiple utilization ways of hydrogen energy are suitable for distributed energy development and large-scale centralized power generation, which greatly enriches the flexibility of the energy system. According to the goal of Japan's "hydrogen society" national strategy, hydrogen energy will eventually form a new secondary energy supply structure together with electric energy and heat energy, and be popularized and utilized in the whole society. Japan's "White Paper on hydrogen Energy" predicts that by 2030, Japan's hydrogen energy market will reach 1 trillion yen, and hydrogen fuel power generation will account for 5% of the country's total power generation.

Similar to Europe and the United States and other countries, Japan has officially carried out the demonstration and verification of PtG projects according to the planning of the "Hydrogen energy and fuel cell Strategic Roadmap". Among them, the "Fukushima Hydrogen Energy Research Area (FH2R)" project aims to build the world's largest "hydrogen society" demonstration base and smart community for hydrogen production, storage, transportation and use of renewable energy, and construct and operate a 10MW hydropower electrolysis plant in Namie, Fukushima Prefecture. In order to show the world the results of hydrogen energy development, the Japanese government also spent $350 million to build an underground pipeline for the Tokyo Olympic Games, and directly input the Fukushima hydrogen energy into the Olympic Village, so that at least 100 hydrogen fuel cell buses and training facilities, athletes dormitory and other more than 6,000 Olympic village buildings are all powered by hydrogen fuel.

Compared with the European Union and the United States, Japan has set the world's highest standard technical indicators and cost targets for PtG systems, including achieving investment costs of 50,000 yen /kW by 2020; Japan's renewable energy fixed price purchase system (FIT) will officially enter the power generation trading market by 2032.

In addition to the "Fukushima" project, Japan has also carried out the development and demonstration of hydrogen direct combustion power generation technology. In April 2018, Japanese companies Obayashi Group and Kawasaki Heavy Industries took the lead in the world to use 100% hydrogen as the fuel of 1MW gas turbine units. During the test period, 1.1MW of electricity and 2.8MW of heat were supplied to four adjacent facilities in PortLand, an artificial island in the central ward of Kobe City (Kobe City Medical Center General Hospital, Kobe Island Sports Center, Kobe International Exhibition Center, and Hong Kong Island Sewage Treatment Plant). With the support of a government grant, the company supplies the PortLand area's hotels, convention centers and other energy at market rates, and currently provides half of the area's annual electricity and heat demand, with Kansai Electric Company supplementing the shortfall.

In order to achieve large-scale hydrogen power generation, the experiment and demonstration of gas turbine co-firing power generation technology containing 20% hydrogen natural gas hybrid fuel has also been promoted in PortLand since 2018, and the detailed design experiment of 500MW class gas turbine has been carried out. With the breakthrough of technical problems such as reducing NOx value and improving power generation efficiency, large-scale hydrogen power generation will be possible. According to the goals of Japan's "hydrogen energy and fuel cell strategic roadmap", hydrogen power generation will be commercialized in 2030, the power generation cost is less than 17 yen/(kW×h), the hydrogen power consumption reaches 300,000 t per year, and the power generation capacity is equivalent to 1GW; The ultimate goal is to generate electricity at a cost of less than 12 yen/(kW×h), to remain competitive with LNG thermal power generation, taking into account environmental value, and to use 5 million to 10 million tons of hydrogen power per year, generating capacity equivalent to 15 to 30GW.

5. Hydrogen cost analysis

If hydrogen energy is to be widely accepted as an emerging energy source and occupy a place in the future energy structure, the cost factor will always play a decisive role. In the world, the hydrogen industry chain is not mature at this stage, especially the high price of hydrogen, and the cost still restricts the long-term development of hydrogen energy. Taking logistics vehicles, a typical scene of domestic hydrogen fuel cell vehicles, as an example, two popular hydrogen fuel cell logistics vehicles are selected to compare with traditional diesel logistics vehicles. The maximum load capacity of the two hydrogen fuel cell logistics vehicles is 3t, while the fuel consumption of 3t diesel logistics vehicles on the market is about 15L for 100 kilometers. The parameters of the two hydrogen fuel cell logistics vehicles are shown in Table 3. With reference to the current market price, assuming that No. 0 diesel is 6 yuan /L, the crossover point of the use cost of hydrogen and diesel is obtained. According to estimates, the crossover point of the use cost should be below 30 yuan /kg, that is, the price of hydrogen below this price in order to occupy the advantage in the market, and the current price of domestic hydrogen stations is 60 to 80 yuan /kg. Therefore, how to reduce the cost of hydrogen supply is an unavoidable problem for the current industrial development.