Tdworld 3548 Hydrostorage
Tdworld 3548 Hydrostorage
Tdworld 3548 Hydrostorage
Tdworld 3548 Hydrostorage
Tdworld 3548 Hydrostorage

Toronto Hydro to Launch World's First Underwater Energy Storage System

Dec. 10, 2015
Technology harnesses the power of Lake Ontario to help boost electricity to the city. See video below for how it was installed.

Located 3 km off Toronto Island and in 55 m of water, sits the first ever underwater compressed air energy storage system. Officially unveiled today, Hydrostor's system is connected to Toronto Hydro's electricity grid where it will remain until a two-year pilot study is complete. The project represents years of hard work designing and building the underwater storage unit and the onshore energy conversion center. The system is expected to improve power quality and resiliency for island residents and engineers will be monitoring its performance through a variety of tests.

Hydrostor is a unique energy storage system as it uses compressed air and the pressure of water to run its system, and produces zero emissions. The technology works by running electricity through a compressor and converting it into compressed air. The compressed air is sent underwater where it is stored in large balloon-like structures, made out of the same type of material used in marine lift bags to raise shipwrecks. When electricity is needed again, the weight of the water pushes the air to the surface through a large pipe and an expander converts the air back into electricity.

Energy storage systems are designed to store electricity during off-peak hours when demand is low and electricity is cheapest. Electricity can be released when the grid needs a boost, such as during times of high demand or during short-term power outages.

As Toronto Hydro is in the midst of a massive capital program to renew and upgrade its electricity system, the organization is actively exploring energy storage as a way to extend the life of some of its equipment. Hydrostor is the first energy storage project Toronto Hydro has been involved with that is located underwater.


  • At peak output the storage unit is capable of powering approximately 330 homes (660kW). Depending on how much power is drawn, the system can currently run for a little over an hour, although future expansion of the underwater air cavity will increase this duration.
  • The underwater compressed air energy storage system does not produce any carbon emissions and is expected to increase fish habitat.
  • Organizations involved in Hydrostor include:
    • Toronto Hydro
    • City of Toronto
    • ‎Ontario's Innovation Demonstration Fund
    • Sustainable Development Technology Canada
    • Ontario Centres of Excellence

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