The present invention generally relates to storing energy in a form that is carbon neutral, storable and transportable, so that it can be used on demand. The present invention provides a process and system for using energy as available to produce carbon from carbon oxide, and then oxidizing the carbon to generate useful energy on demand, while effectively recycling the carbon, oxidant, and carbon oxide used in the process or system. In one embodiment, the present invention effectively stores renewable energy as carbon, transports the carbon, oxidizes the carbon to generate useful energy on demand and recycles the carbon as carbon dioxide. This invention may increase the utilization of renewable energy, especially for electrical power generation, while producing no net carbon dioxide or other air pollutants.