Abstract:The rapid growth of fluctuating power sources, mainly wind and solar energy, has led to severe power imbalances and urgent need for developing the energy storage technology. Pumped storage is the largest and most mature energy storage mode by now and has become the energy storage mainstay in the power grid. Gravity energy storage can also realize similar function, by replacing the storage material “water” in pumped storage with other solid heavy objects. There are relevant reports about gravity energy storage abroad, while still lacking in China so far. In this paper, the present situation of gravity energy storage was analyzed, and a conceptual scheme, which includes the gravity turbine and the up and down storehouses, was proposed by analogy with pumped storage. Meanwhile, the working processes, principles of energy storage and power generation of gravity energy storage were clarified, and the power output formula was derived theoretically. According to scientific conception and comparative analysis, it is preliminarily estimated that the net height of gravity energy storage is about 100 m and the corresponding maximum single unit capacity can reach 10 MW. In addition, distributed planning can be adopted to realize flexible large-scale energy storage. Based on the exploratory analysis, four technology conceptualizations and key problems of gravity energy storage are proposed as follows: 1) The gravity turbine for converting the potential energy of heavy objects into rotating mechanical energy. The gravity turbine is developed which works similarly to the hydraulic turbine, the maximum transport capacity is more than ten tons per second and the target efficiency is 80%. Since the gravity turbine is the critical core component of gravity energy storage, more needs to be studied in the mechanical engineering applications. 2) The suitable layout of up and down storehouses. Combined with the actual geographical conditions, flexibly arrange the up and down storehouses. Using the space between up and down storehouses to store heavy objects can reduce the land occupation. The up and down storehouses layout, gravity turbine and conveying system should be discussed and demonstrated as a whole system since the former can affect the development and research of the others. 3) High efficiency conveying system for heavy objects, including lifting heavy objects from the down storehouse to the up storehouse and transporting them in the same storehouse. Because the commercial value of gravity energy storage is directly related to the conveyance energy consumption and system efficiency, extensive research is needed to find a safe, efficient, and feasible conveying system. 4) Reasonable selection of heavy objects. Concrete as the main material of heavy objects is more appropriate. The construction waste and local material are used as much as possible to reduce the impact on the environment. In addition, heavy objects should be standardization with the same specification and durability for long recycling. All in all, gravity energy storage has the significant advantages of environmental friendliness, flexible layout, high safety, long life, no self-discharge, etc., with outstanding research and development value and broad application prospects. However, gravity energy storage technology is still in the exploration stage. Further investigations of gravity energy storage are needed to promote the pre-study, program planning and technology development, which would provide backup support for the long-term development of new energy.