The rapid development of intermittent renewable energy has increased the demands for storage in power systems. In the meantime

the expeditious advances in shared economy would bring new business opportunities to the application of storage. Based on the sharing of storage devices

cloud energy storage(CES)would become one of the important features for future power system configuration. CES is a grid-based storage service that enables ubiquitous and on-demand access to a shared pool of grid-scale energy storage resources. It is capable of providing energy storage services at a substantially lower cost. This paper explains the concept of CES and elaborates the elements of the CES business model. The key issues on CES investment and planning

operation

and service pricing are analyzed. The current research progress

approach and methodology are reviewed. The key problems that should be addressed in the future are pointed out to improve the development and implementation of CES. The future research on CES are previewed and discussed.