Offshore Renewable Energy Storage: CAES with a Buoyancy Engine

Abstract

This project is primarily focused on numerical analysis of an innovative technique that significantly improves the harvesting of energy from underwater compressed air energy storage (CAES) systems. The underwater CAES system stores compressed air at constant pressure in Energy Bags anchored at the bottom of the water body (1). This project presents the Buoyancy Engine, a renewable energy concept which generates short term electrical power sufficient to produce additional heat energy required for the expansion of the compressed air. The short term electrical energy is harvested and utilised to generate an electrical arc which is used to heat up charged molten salt to over 500°C (2), for a more efficient, controlled and extended electricity generation period. Molten salt energy storage systems have been known to produce electricity for 15 hours from only stored energy (3). This work shows the results of numerical investigations of the net buoyancy acting on ascending energy bags and the techniques for converting it to useful energy for the air expansion stage.