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Energy Storage

Unlike other forms of energy, electricity could not be easily stored in large quantities. As a result, the electricity system has historically operated on a "just-in-time" basis with decisions about electricity production based on real-time demand and the availability of transmission to deliver it.

This paradigm is now changing with the emergence of new more cost-effective energy storage technologies, which allow electricity to be captured and dispatched to the grid whenever required. Storage can also benefit the system in the following ways:

  • Smoothing out fluctuations of solar and wind resources, bringing added stability to the electricity system

  • Easing points of congestion in transmission and distribution networks by temporarily absorbing surges and excess power flow, allowing utilities to defer, or even avoid,​​ expensive system upgrades

  • Absorbing surplus baseload generation when the output is higher than minimum demands

  • Providing critical reliability services that support voltage and frequency on the system

Energy Storage Procurement​​​​

The IESO’s technical report on energy storage focuses on the reliability needs of the Ontario power system and the potential for energy storage technologies to address those needs.

In the first of a two-phase competitive procurement process, the IESO selected storage technologies from five companies that will offer ancillary services to support increased reliability and efficiency of the grid. The IESO will take the lessons from these projects, totalling approximately 34 megawatts (MW), to understand how to better manage the day-to-day operation of the power grid using electricity storage. Read the backgrounder for more information on these projects and the technologies selected.

In the second phase of the procurement process, the IESO offered 10-year contracts to five companies for nine separate energy storage projects totalling 16.75 MW. Phase II sought energy storage technologies with a range of performance characteristics that can store energy when prices are lower and re-inject it at other times of the day when prices are higher and the energy has greater value. Read the news release and backgrounder for more information on these projects and the technologies selected.

These procurements support the province's efforts to better understand the integration of energy storage into Ontario's electricity system and market. In 2014, the IESO and Ontario Power Authority's joint submission of a procurement framework was endorsed by the Minister of Energy.

Read more about IESO's energy storage procurement.

Alternative Technologies for Regulation

The IESO is already using storage technologies as a source of "regulation" − a specialized service that maintains second-by-second balance on the grid. It can be provided by generators, fast-responding loads, or fast-responding storage resources.

By helping to correct small, sudden changes in power system frequency, regulation balances power flows and maintains the reliability of the power system. This quick response is becoming increasingly important to facilitate more renewable resources like wind and solar, whose output is variable in nature.

NRStor Inc., in partnership with Temporal Power is providing two megawatts of regulation using flywheel technologies. Renewable Energy Systems Canada Inc. delivers Ontario's first battery regulation service with four megawatts of capability. 

Energy Storage Technologies​

Energy storage systems come in many different sizes, and types of capabilities. Different kinds of storage technologies perform a variety of roles and are used to support various needs at customer sites, the distribution system, and the bulk electricity system. The examples below illustrate various energy storage concepts and may not necessarily meet the definition of energy storage used in IESO procurements and various regulatory instruments.

Batteries ​

Lithium-ion batteries and liquid electrolyte "Flow Batteries" are able to store excess electricity from the grid and release that supply back into the grid. Capable of changing their output in less than one second, some types of batteries are now being used by grid operators to quickly balance variations in load to regulate frequency. Battery systems are also often found at the distribution system level and at individual customer sites. Other forms of battery technology are at various stages of technological development and show promising future potential as well.

Ontario's first flywheel and battery storage facilities were connected to the power grid in 2014. Read more about NRStor's flywheel and RES Canada's battery.

Flywheelsman working on flywheel

Like batteries, flywheels can both store and quickly release energy as needed. Flywheels use a rotor placed within in a vacuum to store and then discharge kinetic energy.

Compressed Air and Vacuumed Air

Compressed air uses off-peak energy to pump air into a containment area such as an underground mine​, where it is held until needed. It is then released through an expansion turbine.  In some cases, this may be done in conjunction with natural gas fuel, which increases the efficiency of the generator to provide more efficient energy during peak hours. Conversely, vacuum air storage systems are the mirror image of compressed air arrangements, where off-peak energy is used to create a vacuum, which is later repressurized, creating an airflow when power generation is needed. 

Electric Vehicles  ​

Electric vehicles - and their batteries - can be considered as both controllable load during periods of lower demand and, with the appropriate technologies, a source of supply during times of higher demand. Using smart electric vehicle charging stations, customers would supply the grid or use the electricity to meet their own energy needs.

Read Powerstream's backgrounder on Car-to-Grid technology.

Thermal Energy 

Not all stored energy necessarily comes directly back to the power grid as electricity. Off-peak energy can be stored as thermal energy, which can then be used to supply heating and/or hot water needs, reducing electricity consumption during on-peak periods.  Increasingly, solar thermal systems are being used around the world to supplement or replace the electrical energy drawn from the grid for such uses.  Ice storage systems do just the opposite where off-peak energy is used to make large blocks of ice to help cool buildings during peak hours. Other more sophisticated, high-temperature thermal storage systems can also be used to generate steam for electricity production to supply back to the grid.   

Fuel production

Electricity can be used as an input in the production of other types of fuels such as hydrogen and biofuels, which can also act as an energy storage medium.  These fuels can then be used to generate electricity to send back into the grid at optimum times or for other non-electrical energy needs. Off-peak electricity can also be used for compressing natural gas an emerging need in the transportation sector. 

Magnetic fields

Magnetic fields are capable of storing electrical energy, and when coupled with superconductors, the storage potential can be significant. Some pilot projects involving superconducting magnetic energy storage are currently under development at various laboratories and utility equipment providers around the world. However, the future success of these new forms of energy storage devices is highly dependent on the cost of the  superconductors themselves. 

Pumped Storage

Pumped storage is essentially hydroelectric power that takes advantage of lower-priced periods to pump water into a reservoir, and then releases the water when needed. Presently, it is the most established and widely used form of energy storage in the world. Ontario has one large-scale pump generation project: Ontario Power Generation's pump-generation facility in Niagara, which has been operating since 1957. This 174 megawatt facility has helped meet peak supply, manage surplus conditions, provide regulation services, and operating reserve.