Chemical energy storage utilizes electrical energy to convert low-energy substances into high-energy substances for storage, thus achieving energy storage. Currently, widely used technologies in the field of chemical energy storage include hydrogen energy storage and synthetic fuel (such as methane and methanol) energy storage. These storage media can be used directly as energy sources. Therefore, in this respect, chemical energy storage differs fundamentally from traditional energy storage methods where both input and output are electrical energy. When end users can directly utilize substances like hydrogen or methane (e.g., in hydrogen fuel cell vehicles, combined heating and power systems, or the chemical industry), these stored energy forms do not need to be converted back into electrical energy in the power system, thereby improving the efficiency of the entire energy utilization system. This direct utilization method effectively transforms traditional "secondary energy" storage into a more efficient "tertiary energy" storage model. Therefore, chemical energy storage is often a crucial link in the energy conversion process, offering advantages such as high energy density, long storage time, and flexible scale, making it suitable for long-term, large-scale energy storage. Furthermore, chemical energy storage can utilize existing energy infrastructure, such as natural gas pipelines and liquefied fuel storage facilities, reducing deployment costs. Therefore, chemical energy storage has enormous potential for development in renewable energy grid connection, industrial heat demand, and transportation, especially in addressing the volatility of renewable energy.
Hydrogen energy storage
Hydrogen energy storage is a technology that converts electrical energy into hydrogen for storage. Its core involves producing hydrogen through water electrolysis or other chemical processes, and releasing energy when needed via fuel cells or direct combustion. Hydrogen, as a clean secondary energy source, features high energy density and zero carbon emissions, and is widely used in transportation, industry, and energy storage. The key challenges of hydrogen storage technology lie in the efficient production, storage, and transportation of hydrogen. Currently, the main hydrogen storage methods include high-pressure hydrogen storage, cryogenic liquid hydrogen storage, and solid-state hydrogen storage (such as metal hydride hydrogen storage). Although hydrogen storage systems are relatively expensive, with technological advancements, especially the development of green hydrogen production technologies, hydrogen energy storage is considered one of the important solutions for achieving deep decarbonization and driving energy transformation in the future, particularly suitable for large-scale, long-term energy storage and heavy-duty transportation applications.
Synthetic fuel energy storage
Synthetic fuel storage utilizes electricity to generate chemical fuels (such as synthetic natural gas and synthetic liquid fuels) for long-term energy storage. This technology typically involves electrolyzing water to produce hydrogen, which is then combined with carbon dioxide to synthesize hydrocarbons such as methane, methanol, or synthetic diesel. These synthetic fuels can be stored and transported, and when needed, converted into electrical or mechanical energy through combustion or in fuel cells. The advantage of synthetic fuel storage lies in its compatibility with existing energy infrastructure, such as existing natural gas pipelines, liquid fuel storage and distribution systems, making it suitable for long-term, large-scale energy storage. Furthermore, synthetic fuels can serve as a peak-shaving supplement to renewable energy generation, helping to balance the power grid. Although synthetic fuels have lower overall efficiency and higher costs, with the increasing availability of renewable energy and advancements in carbon capture and utilization technologies, synthetic fuel storage is expected to become an important component of future low-carbon energy systems.