The Canadian company Hydrostor has developed a way to store energy using pressurized air kept in underwater balloons and currently has a pilot project in Lake Ontario. The air is used at opportune times to turn turbines to generate electricity. CEO Curtis VanWalleghem generously answered some questions about the technology for CleanTechnica.
How did you come up with the idea to use underwater compressed air?
Cameron Lewis (Founder, Chief Technology Officer) was developing a wind site and analyzed adding a small pumped hydro facility that was deemed uneconomic after analysis. That got him thinking that instead of raising water in the air, why can’t I put the air under the water and accomplish the same thing.
How long can one of your underwater balloons last under normal operating conditions?
The supplier has offered a 10 year warranty, but is considering a 20 year warranty as there is very little wear-and-tear on the balloons since the air is stored at hydrostatic pressure (e.g. pressure same on outside and inside of balloon).
How many balloons are used in your current system?
Is the peak electricity output that can be created by the balloons 660 kW?
The peak output of the Toronto Island facility is currently 660kW due to the rating of the generator.
And what is the number of kilowatt-hours?
The underwater air cavity is designed for easy expansion and there are plans to expand the air cavity over the next couple years, so we are not publicly disclosing a storage capacity at this time.
How much space does the underwater balloon array occupy?
The entire structure has an areal footprint of approximately 10m by 40m.
What maintenance is required?
There are no moving parts underwater, so it is designed for little-to-no maintenance. We will be doing annual inspections of this facility to confirm this. The system is designed so it can be easily raised to the surface for inspection and replacement if required.
How much did it cost to build the balloon system and get it running?
We are not publicly disclosing project cost.
How does this cost compared to energy storage in the form of a lithium-battery system of comparable size?
Hydrostor’s Underwater-CAES system is less than half of the cost of the leading li-ion battery solutions with over twice the cycle life.
If the two-year pilot is successful, what will be the next steps?
Hydrostor is actively developing a number of projects around the world. We anticipate starting construction on another facility in late 2016/early 2017. Hydrostor is also in discussions with EPC firms regarding a strategic partnership for project construction.
How large a balloon system can you build, and where can the larger ones be located?
There is really no limit to the size of structure, as they represent a small fraction of the available space in oceans and lakes. The air cavity required drops roughly in half every time the water depth is doubled, so we initially will be targeting the deepest waters.
How much money can be saved by using your system by avoiding the cost of electricity when it is in demand?
This question is very site specific and related to the local electricity markets and rates.
How could your balloon system enhance fish habitat?
Yes, we include a significant amount of ballast that is designed to provide marine habitat.
Can underwater balloons be used in oceans, or are their currents and waves too volatile?
Yes, the system has been designed for oceans.
Image Credit: Hydrostor
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