Canadian startup stores off-peak energy in balloons under a lake Tuesday, 01 December 2015

Balloons of compressed air in Canada could revolutionise the way we store off-peak energy.

Hydrostor partnered with Toronto Hydro to launch the world’s first underwater compressed air energy storage system, located in Lake Ontario, three kilometres off the south shore of Toronto Island, underneath 55 m of water.

At the heart of the zero-emissions energy storage system is a number of number of balloon-like structures filled with compressed air. The facility stores energy from various sources during off-peak hours, when electricity is cheap due to low demand, then puts the energy back into the grid during peak times.

To store electricity, Hydrostor converts electrical energy into compressed air using an advanced compression system. It sends the compressed air through a three kilometre pipe, and stores it in the accumulators underwater. To ensure toughness, the accumulator balloons are made from the same material used to raise shipwrecks from their resting places underwater.

The system also uses heat exchangers to harvest the energy from the heat created by the air compressors.

To pump the energy back into the grid, the system leverages the natural pressure of the water to push the compressed air out of the accumulators, back up through the pipe, and into a turbine, which then runs to create the electricity.

Hydrostor says the system has a round trip AC/AC efficiency from 60% to 80% or higher, and unlike batteries, will not suffer efficiency loss over its lifetime of 30 years. Another benefit of the technology is the capital costs, which are said to be less than half that of competing lithium ion battery technology, while still delivering over twice the cycle life.

According to Hydrostor, while compressed air has been around for a long time, it has been an under-explored option for modern energy storage, due to the lack of room to store the compressed air.

By utilising the space underwater, as well as the hydrostatic water pressure, the company says the system could be used in a variety of environments.

The demonstration project has a capacity of 660 kW hours, which is enough to power 330 average homes. The technology is emissions-free and easily scalable, allowing for example larger systems to be built.

The technology also has an edge over the common battery-based energy storage and backup systems, by eliminating the use of toxic substances.

Hydrostor is now exploring further options for the commercialisation of the technology.

“We are thrilled to have the first underwater compressed air energy storage system in service,” the company’s CEO, Curtis VanWalleghem, said. “We’re now focused on commercializing this technology globally to bring our green energy storage solution to countries around the world.”

The company has already entered into a contract with a utility company in Aruba to build a larger facility.

Hydrostor is also looking for opportunities to deploy its systems in island nations who wish to transition to renewable energy, as well as coastal cities which need peaking power and grid-regulating storage.