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Energy Storage

What is energy storage?

Salem Smart Power Center-sm.jpgOne of the central principles of the electric grid is that generation must match demand. In other

words, we must provide enough electricity – at the right frequency and voltage – to meet our electric load at all times.

Because our electricity needs are not controlled and varies with the flick of a light switch, utilities use many tools to ensure we have enough power. Grid operators use sensors and many levels of management to make sure that power is delivered where it is needed. One of the challenges of bringing new renewable energy online is managing the variability of its generation to the variability of load – called integration.

Storing energy has the potential to change the fundamental equation and make the grid more flexible. Energy storage can offer buffers between generation and load, which reduces operational complexity, smoothes variable generation, builds resiliency in our distribution systems and backs up power for emergency services.

Typically, energy storage provides one of three services:

  1. Power quality – stabilizing power to ensure continuous quality (services available in seconds or fractions of a second)
  2. Managing variability and shifts – operational buffers (available in seconds to minutes)
  3. Grid-level services – system balancing over daily cycles (available over hours; significant amounts of energy delivery)

Sandia National Laboratories maintains a clearinghouse of state and federal policies as well as a list of projects, called the Energy Storage Exchange.

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Types of electricity energy storage

There are many forms of electricity-related energy storage. Most existing technologies fall into one of these categories: pumped hydropower, batteries, flywheels and compressed air.

One in-depth resource on electricity energy storage is the 2013 Electricity Storage Handbook. Page 29 of the main document contains a table with a general overview of the technologies, rate of electric dispatch and size of energy systems.

Below are brief descriptions of these types of energy storage.

Pumped hydropower

Kinzua Dam on the Allegheny River and FirstEnergy’s Seneca pumped storage reservoir in Pennsylvania. (U.S. Army Corps of Engineers Digital Visual Library)

A pumped storage system consists of two reservoirs, one at an elevation higher than the other. When electricity demands (and prices) are high, water moves down to the lower reservoir – similar to how power is generated through a hydroelectric dam. When price and electricity demand is low, usually at night, the water is pumped back up to the higher reservoir.  These plants can technically operate at any size, but most proposals are very large for grid-level services – 500 to 1,000 megawatts. These are similar in output to many natural gas plants and some of the larger wind farms in Oregon.

For more on this topic, see: Federal Energy Regulatory Commission on Pumped Storage Projects


Batteries – which convert chemical energy into electrical energy – are among the most commercially ready energy storage technology. Today, there are traditional and advanced batteries.


Flywheels use energy to cause an object to spin. The energy is stored as kinetic energy in a rotor. When the electricity is needed, the rotor is used to drive a generator and create electricity.

Compressed air energy storage

Compressed air energy storage systems use energy to compress air and store it in a reservoir. When electricity is needed, the air is expanded to generate electricity. The storage reservoir can be underground (an air-tight salt cavern) or above ground (tanks). These systems can be large (greater than 100 megawatts) and provide grid-level services.

There are two underground compressed air energy storage systems in operation today, in Alabama and Germany.

The Pacific Northwest National Laboratory recently worked with the Bonneville Power Administration to study the potential for CAES in Washington and Oregon. According to PNNL, “[e]astern Washington and Oregon are rich with potentially suitable sites for CAES.”

GRAPHIC: Pacific Northwest National Laboratory


Supercapacitors are an advanced capacitor that can offer tremendous power quickly, but only over a very short duration. Supercapacitors are focused on wind integration and responding to dramatic shifts in load. Supercapacitors are still in the testing phase, with a study recently completed at Wallace Energy Systems and Renewables Facility at Oregon State University.

Thermal energy storage

There is also an opportunity to use heating and cooling as a form of energy storage. Using heat (thermal) equipment, we can use ice, freezers, water heaters, and other thermal “banks” to manage energy systems.

Opportunity in Oregon

The Governor’s 10-Year Energy Action Plan (2012) states the following:

“Storage: Numerous storage options – including battery-based or pumped energy storage – can also increase the ability to balance out intermittent resources, such as wind or solar, and provide an alternative to building new infrastructure, such as transmission line expansion. As battery technology continues to become more efficient and the need to integrate more diverse generation resources increases, battery-based energy storage has the potential to offer a cost-competitive option.”

Currently, there are no pumped storage facilities in Oregon. But as of October 2013, Swan Lake near Klamath Falls is the most advanced plan in the Northwest. The project’s location can take advantage of the Northwest and California markets. Swan Lake would be a closed-loop facility with a capacity of up to 1,000 megawatts.

Portland General Electric’s Salem Smart Power Center includes a five-megawatt bank of lithium-ion batteries. The batteries can be used for renewable integration: for small-scale ancillary services in firming and shaping intermittent resources. The system can also be used to run the Center’s micro-grid for up to 30 minutes. In addition, the Center takes advantage of the traditional form of storage: back-up generators within its operational territory, including a solar array at Kettle Foods.
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Other efforts in the United States


The California Public Utility Commission recently adopted an energy storage procurement target for each utility by 2015, and a second target to be achieved by 2020. California has preliminarily set a utility procurement target of 580 megawatts each for Southern California Edison and Pacific Gas and Electric by 2020, with sub-targets by year and by storage class (transmission, distribution, customer). MORE >>

New York

The state of New York has provided $25 million to fund the New York Battery and Energy Storage Technology Consortium to advance the storage industry in that state. In addition, the state provides innovation grants to developers. In April 2013, the New York State Energy Research and Development Authority announced $1.4 million in awards to six energy storage companies, including one electric vehicle application. MORE >>

New Mexico

The New Mexico legislature in 2013 issued a joint memorial that directs its state energy office to establish an energy storage task force and to deliver a report to the legislature. The task force has met twice and was to submit a report to the legislature by the end of 2013. The report will be a high-level look at barriers and opportunities. MORE >> 

New Jersey

New Jersey has convened an energy storage working group aimed at critical infrastructure. The state has dedicated $250,000 in grant funds for the first year of a four-year program. If successful, there may be more funding available in successive years. MORE >>
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For more information...

For more information on these topics, please contact the Oregon Department of Energy’s Rebecca O’Neil at 503-373-2295.
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