Research Article
Dalgaard JZ*
Abstract
One of the problems using most green energy sources is that there is not a constant supply. Therefore, there is a need for the development of energy storage and release systems. Many different technologies have been developed and employed for storage that among others includes: 1. Pumped hydro-power (potential energy), 2. Railway lines and carriages loaded with stones in hilly terrain (potential energy), 3. Thermal storage (thermo-dynamic energy), 4. Flywheels (kinetic energy), 5. Batteries (chemical energy), 6. Phase transition of salts (thermo-dynamics energy) and 7. Compressed air (thermo-dynamic energy) Here I propose the potential use of CO2 and its phase-transition from gas to liquid in large sub-terrain cavities, such as disused mines, for electric energy storage and ground-heat extraction.