Article content continued

The technology is well-suited to island nations that lack space onshore, big cities on the coast and renewable power projects.

Hydrostor has already signed a contract to build a plant in Aruba: it will construct a 10-MWt facility on the small Caribbean island to accompany a 30-megawatt wind farm.

Storing surplus electrical energy in a cheap, environmentally neutral way has been the Holy Grail of engineers in the power industry. From next-generation batteries to fly wheels and thermal storage, many new technologies have emerged, but none has been chosen to supplant the traditional method known as “pumped hydro.”

The mechanics of a pumped hydro station are simple. Water is pumped uphill into a reservoir and held there, storing its potential energy. When more electricity is required, the water is released and funnelled downhill to power a turbine.

Hydrostor founder Cameron Lewis was trying to design a small-scale pumped hydro station until he realized the project was not cost-effective.

While investigating alternatives, Mr. Lewis had a breakthrough. “He said, ‘Well, if I’m just lifting water in the air’,” Mr. VanWalleghem said, “’why can’t I just put an air jack under the lake and basically pump it up?’”

This concept is the basis of Hydrostor’s system. Instead of pumping water uphill, the company pumps compressed air underwater.

Hydrostor can store the energy that wind turbines or solar panels produce on sunny or windy days to offset the lack of energy they produce on cloudy, windless days. The technology can offset the risk of blackouts on hot summer afternoons when the power grid is being stretched to its limit by air conditioners.