Toronto Hydro to test cost-competitive underwater energy storage

Toronto Hydro to test cost-competitive underwater energy storage

Toronto Hydro to test cost-competitive underwater energy storage Energy Storage Journal

During 2013 a system for storing energy under water will be constructed in Lake Ontario in Canada for evaluation by Toronto Hydro, one of the country’s main utilities.

Hydrostor’s underwater compressed air electrical storage (UW-CAES) system is designed for grid-scale energy storage by utilities and private businesses and can be used in conjunction with solar or wind to provide cost-competitive base-load renewable power.

The Lake Ontario demonstrator will allow Toronto Hydro to effectively break in the system and carry out its own tests. It will also provide Hydrostor with the opportunity to evaluate the cost of construction which is expected to begin around July time. In preparation the system has been tested in lab pool tests and in the lake up to 30 m deep. The 1 MW/4 MWh demonstrator is 7 km off of the shore of Lake Ontario at a depth of 80 m.

The most prevalent and cost-effective form of energy storage today is pumped hydro, but, like underground CAES, it is only suitable for large-scale storage, typically hundreds of MW or GW capacities and is also limited by geographic location. At the other end, batteries are more decentralised. ‘Batteries are good in the small MWs range but they are expensive. Hydrostor can compete on pumped hydro costs but at the scale of battery storage applications,’ explains CEO Curt VanWalleghem.

In Hydrostor’s UW-CAES system surplus renewable electricity drives a compressor that pressurizes air to the pressure at the sea or lake floor. The heat that is produced during compression is extracted from the air and stored in an insulated thermal reservoir, while the air is stored in large accumulators anchored to the lake bed. These inflate below the water’s surface. The weight of the water keeps the air stored in these bags at a constant pressure until required. At times of peak electricity demand the whole process is reversed, achieving roughly 70% round trip efficiencies, supplying energy to the grid and completing the storage cycle.

In 2014 Hydrostor aims to have a second demonstration plant up and running in the Caribbean with a national utility there to store surplus wind energy at night time. The technology competes with the costs associated with diesel generation. ‘We have several potential customers interested and once both sites are up and running we’ll have Lake Ontario, with Toronto Hydro, as our city show piece proving the system for peak shaving back up and the Caribbean installation as our island show piece for renewables integration. We don’t only envisage utilities as customers but also casinos and marina resorts too as these can be big consumers of energy,’ says VanWalleghem.

Hydostor’s new investor MaRS Cleantech Fund is bullish about the technology, stating it will allow wind and solar developers to be able to bid on base-load energy contracts.
‘Our fund targets technologies that change the energy game, and low-cost storage is at the top of our list,’ said Tom Rand, co-managing director of MaRS Cleantech Fund, which specialises in early-stage cleantech investing.

Unlike other companies bringing to market similar UW-CAES technology, Hydrostor, which was set up in 2010, is able to keep costs down by sourcing all of the components needed to make the system.