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Toronto Hydro is testing the world’s first underwater compressed air energy storage project in Lake Ontario, near Toronto Island.

About the Project

Toronto Hydro is working with Hydrostor Inc. to analyze the electrical grid benefits of underwater compressed air energy storage (UCAES). The world's first system has now been installed in Lake Ontario. The pilot project will focus on the unit’s ability to provide reserve power, shift load and smooth out transmission and distribution congestion.  

The system is designed to store excess electricity generated during low-demand off-peak hours by driving compressed air into a flexible wall air accumulator below the lake's surface. When the energy is required, the system is reversed.



How it works

Compressed air stored in a fixed wall air accumulator allows for the use of electricity on-demand. When electricity is required, the weight of the water pushes the stored air from the underwater accumulators through an air feeder pipe into an expander, which drives a generator, to supply electricity back to the grid.


+ Watch animated explanation to learn how the technology works
+ Learn more about Hydrostor

Environmentally friendly, locally based, clean energy storage

Energy Storage is a key part of a sustainable green energy solution for Toronto. All materials for the air cavity are fish and animal friendly. The system stores only air and produces no toxic by-products that can harm the environment or aquatic life.


This project is funded by:

  • Hydrostor Inc.
  • Sustainability Development Technology Canada
  • Innovation Demonstration Fund, provided by
    the Ontario Ministry of Economic Development

Other consortium members include:

  • Baird & Associates
  • LocalGrid Technologies
  • Virelec Inc.
  • University of Windsor