In the waters of Lake Ontario, Canada, a hugely significant energy development is taking place. Hydrostor is a company specializing in underwater compressed energy storage.
Their idea addresses a significant issue facing renewables: the question of how to store energy to be used when the sun is not shining or winds aren't strong enough.
"The way the grid operates is (at) any moment the amount of demand – how much stuff is plugged in – has to equal how much is being produced, and if ever those get out of balance you start having brownouts and power quality issues, so that's what it means to… keep the grid 'in balance'," Curtis VanWalleghem, Hydrostor's CEO, told CNBC in a phone interview.
"As we add wind and solar… (it) makes it very difficult to do that because clouds come, gusts of wind surge," VanWalleghem added.
Hydrostor's system works in several steps. Electricity is run through a compressor and converted into compressed air. This compressed air is then sent underwater.
"There, we have a whole series of what are effectively balloons, that fill… like lungs under a lake," he added.
"They fill with air, and when they're full you stop charging the system and it can sit there indefinitely. When you want power back, again, a valve opens … air comes rushing out, we run through a low pressure turbine called a turbo expander, and that reproduces power back to the grid."
Energy storage is becoming increasingly important. In the United States, the Office of Electricity Delivery & Energy Reliability states that the development of technology to store electricity so it's available on whenever it's needed would be a "major breakthrough in electricity distribution."
In November Hydrostor announced that it had activated what it described as "the world's first underwater compressed air energy storage system."
Located at the bottom of Lake Ontario in Toronto, the system will be operated by Toronto Hydro and has been designed to store electricity during off peak hours and return it when demand is high or power outages occur. Hydrostor say their process produces zero emissions.
How much potential does the work being done by Hydrostor have? "All we need is water pressure, so what we look for is deep water: the deeper (the water) we have closer to shore, the better the system is."
Storage, VanWalleghem said, will be crucial if the world is to eventually transition from fossil fuels to renewables.
"Without storage you need lots of coal and gas plants, that's the bottom line," he said.
Because renewables are not on demand and intermittent by nature, a balancing act is needed.
"And if what you use to balance it is fossil fuels then you're kind of defeating the purpose of why we're going to renewables in the first place," he added.