Tubular design for underwater compressed air energy storage

- Tubular Design for Underwater Compressed Air Energy Storage.
- This paper contains a design proposal for energy storage in form of compressed air kept in flexible underwater containers (flexible UWCAES). We believe it may be of interest for isolated communities living in islands.
- After carefully reviewing the set of requirements that a realistic large scale project should meet, we propose what we think is the optimal design, the tubular bag. It is simple to build, structurally stable, and its linear geometry naturally adapts to the level curves of equal depth.
- We perform a particular case study for a 1 GWh energy storage at 1000 m depth. The actual length depends basically on the tensile strength of the flexible fabric material. We select nylon and kevlar in order to model two extreme situations. The required length of the tubular bag lies in the interval between 1 km (Kevlar) and 15 km (nylon).
- No evidence of portfolio rebalancing into emerging economies.
- We finally pay attention to collateral details which are also important. Ballasting is calculated and seen to be problematic; some speculative alternative is briefly sketched. Scaling up the system is very natural in this design proposal. An installation protocol for settting in place is also proposed.

Underwater compressed air energy storage (UWCAES) in deep seas is a promising scenario for energy storage. When considered at large scales, specific difficulties arise beyond the ones present when dealing with individual energy bags. After reviewing the set of requirements that a realistic large size project should meet, we propose what we think is the optimal design, the tubular bag. A particular case study is computed numerically aiming at a 1 GWh storage at 1000 m depth. Depending on the material used, lengths lie in the range of 1-15 km. Whereas scaling up is very natural, ballasting poses a challenge and some alternative is proposed.