One criticism of renewable energy systems is that they do not function on demand. You need the sun to shine, the wind to blow, or another natural system to kick into effect. This means that energy will be created when it isn’t needed.

The solution is to take that surplus energy and convert into a storage system that can be turned on when it is demanded. In Toronto, there is presently a pilot project by Hydrostor that is converting that stored energy into compressed air. The air stays compressed thanks to the giant lake that sits on top of the balloon holding the air.

“Most of the world is saying we have to get off fossil fuels,” he said. “To do that, you need lots of energy storage.”
In the same way an everyday battery banks energy using chemicals, Hydrostor relies on compressed, bottled air. And because it produces zero emissions, the system can help Toronto adjust to a healthier low-carbon diet.
It works by stockpiling surplus energy generated during off-peak periods and converting it into compressed air. This air is then sent underwater, stored in balloons and saved, literally in some cases, for a rainy day.

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