Underwater Compressed Air Energy Storage

Energy system flexibility is becoming increasingly important as grid architectures change and the penetration of intermittent renewable generators continue to grow.  Storage has been identified as a critical component of such flexibility by helping to reconcile imbalances between supply and demand from both technical and market perspectives.  Benefits of energy storage (ES) can include improved conditions for renewables integration, a reduction of fossil fuel peaker plants, improved power quality and reliability, deferral of system upgrade costs, and improved power maneuverability.  To provide these benefits requires a very dynamic range of responses from storage technologies that can vary by power, duration, and ramping rate of supply.  No single technology has yet emerged with versatility to effectively cover the entire range.  Subsequently, the storage technologies landscape is broad, from those with very rapid response times and smaller storage capacities like flywheels to those with slower response times and much larger storage capacities like Pumped Hydro Storage (PHS) and Compressed Air Energy Storage (CAES) may be classified as bulk storage technologies. These bulk storage technologies have been identified as very important to the development of ES services in evolving grids given their proven and prospective abilities to provide system balancing, reserve power, and arbitrage services.


Underwater (UW) CAES is a special variant of CAES.  UWCAES utilizes the hydrostatic pressure surrounding a distensibly bounded vessel (like an energy bag) to maintain compressed air at pressure.  This has advantages over traditional CAES systems as the size of containment is modular and the discharge pressure profile is steady.  After 5 years of development, aided by researchers from the University of WIndsor, Hydrostor Inc. and Toronto Hydro brought the world's first grid connected underwater energy storage facility online in 2015.  This collaboration continues presently with the University of Windsor's Environmental Energy Institute and Turbulence and Energy Lab.  Current efforts are focused on next generation energy accumulator design as well as leading edge thermal management and turbomachinery development.

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