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Electricity Storage

Unlike other forms of energy (fuels like natural gas, oil, coal and uranium), electricity cannot be stored in the conventional sense. Rather, it must be consumed at almost the same instant it is produced.

Electricity storage can therefore be thought of as shifting the availability of energy over time.

It has been referred to as the 'holy grail' of bulk power systems because it has such a broad array of potential applications.

For example, it can be used to smooth out fluctuations of wind and solar resources, which can be impacted by unexpected changes in weather. This brings added stability to system.

It could also trap surplus energy that is sometimes produced at night and on weekends and allow it to be dispatched to the grid at higher-demand times.

Storage can also be used to:

  • Ease points of congestion in transmission and distribution networks by temporarily absorbing surges (this would also allow transmission companies to delay expensive upgrades)
  • Regulate voltage levels on the grid to maintain power quality
  • Function as backup power for electricity users in case of a blackout

One storage solution has been in place for decades. Ontario has had a large Pump Generating storage facility, OPG's Sir Adam Beck Pump Generating Station, in operation since 1957.

That facility takes advantage of less expensive night time electricity prices to pump water into a reservoir. It then uses that water to generate electricity during high demand periods.

Other storage technologies have been elusive, held back primarily because of its high cost, but also due to technological and regulatory factors.

That is changing, however.

 

Some different types of storage solutions for the bulk power system:

Batteries

Lithium-ion batteries can both store excess electricity from the grid and release that supply into the grid. Capable of changing their output in less than one second, batteries are now being used by some grid operators to quickly balance variations in load to regulate frequency. That way, they are an alternative to adjusting the output of fossil-fuel generators.

Flywheels

Like batteries, flywheels can both store and quickly release energy as needed. Flywheels use quickly rotating rotor in a vacuum to store kinetic energy, which can then be discharged by driving a generator.

Compressed Air

Compressed air uses off-peak power to pump air into an underground containment area, where it is held until needed. It is then released through a combustion turbine with natural gas fuel, which increases the efficiency of the generator to provide more efficient energy during peak hours.

Electric Vehicles

Increasingly, electric vehicles are being considered both as load, during periods of lower demand, and a source of supply during times of higher demand.

Pumped Storage

Pumped storage is essentially hydroelectric power that takes advantage of off-peak rates to pump water into a reservoir, then uses that same water to create energy during higher-peak times. Ontario has benefitted from a pumped storage facility since 1957 � its only grid-scale storage solution in place to date.

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In Ontario, some storage solutions are moving on from the purely hypothetical.

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Regulation is a service that maintains second-by-second balance in electricity systems. It can be provided by generators or fast-responding storage resources.

Regulation is a service that maintains second by second balance in electricity systems. It can be provided by generators or fast-responding storage resources.

By helping to correct small, sudden changes in power system frequency, it 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.

The IESO is working with several firms to bring storage and flywheel technology (which stores energy in a fast-moving rotor) onto the grid.

This is part of an effort to seek new regulation services, which correct small, sudden changes in power system frequency. That grid-balancing role has traditionally been performed by generators.

Ontario's Smart Grid is another factor that opens the door to new technologies that are expected to shift traditional patterns of production and consumption, including storage. One question that looms over the great potential offered by storage is: how will investors in this new technology be compensated for the array of benefits provided to the electricity system - and society at large.

Regulation is a service that maintains second by second balance in electricity systems. It can be provided by generators or fast-responding storage resources.

By helping to correct small, sudden changes in power system frequency, it 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.