Gravity-based energy storage systems are comprised of pressurized water that lifts a piston within a mined shaft and heavy bricks that are lifted by a crane to store energy. In each case the stored energy is converted into kinetic energy that generates electricity using generators. The systems offer the potential for scalable energy outputs, for example doubling shaft depth increases stored energy content by a factor of four; whereas, for storage based on lifting heavy blocks, scaling with respect to energy is enabled by increasing the mass of each block. The different types of gravity ESSs considered are:
- Heavy bricks lifted by cranes
- Pressurized water that lifts a heavy piston within a mined shaft with power equipment below ground
- Pressurized water that lifts a heavy piston within a mined shaft with power equipment above ground.
The results presented below represent the consolidated cost and performance estimates of the above. For information on each of the gravity storage system types, see the 2022 report.