The use of new and existing technologies to store electricity is an increasingly important and visible issue in the energy field. Energy storage has been referred to by many commentators as a “game changer,” as it will greatly improve the efficient use of electricity resources (generation, transmission, distribution). At the same time, an increased role for energy storage brings challenges for the electricity grid and the role of local distribution companies.
EnergyInsider plans to write regularly about issues and developments in the energy storage field. This first article on the topic aims to provide a brief “primer.”
Benefits of energy storage
From batteries to water towers, the extent we rely on energy storage technology may not be obvious. While past use of energy storage has been generally limited to small-scale use, today’s energy markets are beginning to use energy storage to face the challenge of providing reliability in supply for a large and constantly changing demand.
Until recently, the general approach to ensure reliability of supply at peak demand was to incorporate energy sources which can start or stop electricity generation on a very quick basis, known as “peaking plants.” While this method of meeting demand is functional, it lacks efficiency. Matching immediate generation to immediate demand creates situations where generators are forced to stop generation when they are not needed. Peaking plants have been important as intermittent renewable generation resources have been added to the grid. Energy storage has the potential to reduce the impact of extreme or sudden changes in energy demand and renewable generation availability, which would lessen the need and utilization of peaking plants and lower overall system costs.
Technological advancement has resulted in a push towards various forms of large-scale energy storage that can be used to store excess electricity during periods of low demand in order to assist balancing the grid during periods of high demand. Energy storage can greatly enhance the viability of renewable generation by allowing for the output from that generation to be captured at all times, even where there is no demand. Then, at later times when demand is higher, the stored energy can be contributed to the system. In effect, energy storage would replace peaking plants to contribute capacity during periods of high demand and lessen the operational impact of sudden changes in electricity demand on generators. A useful discussion of the benefits of energy storage, particularly in the context of renewable generation, has been published by the U.S. Department of Energy under the title Energy Storage: The Key to a Reliable, Clean Electricity Supply.
Energy storage can also increase efficiency by using by-product energy that would otherwise be wasted. For instance, the use of thermal storage to utilize waste heat, similar to the process used in combined heat and power plants.
Energy storage can also be used on a smaller scale in homes and businesses to provide back-up power or store excess generation from rooftop solar or even to take advantage of the price spread between peak and off-peak electricity pricing. The most publicized home energy storage product is the Tesla Powerwall, but there are other technology companies developing and starting to offer competing products.
Key forms of energy storage technologies
On a global scale, interest in energy storage technology is growing. A 2014 report by the International Energy Agency (IEA) detailed the potential of energy storage to be a major component of future energy systems, praising its ability to accommodate commonly perceived limitations of renewable energy sources. The report also highlighted notable developments of major players in the industry, including Canada, China, Germany, and the United States.
According to the IEA, as of the time of the report, there was approximately 141 GW of global stored energy capacity, over 99% of which is pumped hydroelectric storage. The remaining portion is comprised of technologies that, until recently, have not been put to use for large-scale storage.
The following is a brief description of the most common energy storage technologies. There is also a useful discussion about key forms of energy storage technologies on the Ontario Independent Electricity System Operator (IESO) website, under the heading Energy Storage.
Pumped Hydro-electric – The benefit of pumped hydro-electric energy storage is that it can store massive amounts of energy, so long as there is an elevated reservoir large enough to hold the pumped water. Where there is excess energy on the grid, energy is used to pump water into an elevated reservoir. When the energy needs to be reclaimed, the pumped water is discharged through turbines which generate electricity to be contributed to the grid.
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