Three Ways Energy Storage Solves Modern Grid Power Challenges
April 16, 2018 | Jan-Hendrik Ernst, Key Account Manager, EMEA
Have you heard of "the energy mix"?
The energy mix refers to the variety of primary energy resources available to us that we can convert into usable electricity. The "mix" includes traditional sources such as nuclear power, oil, natural gas and coal and renewable sources such as wind, solar, hydro and biofuel.
The energy mix presents complexities with fulfilling the demands of power consumers, from residential to industrial. An even trickier part of the puzzle is the entrance of renewable energy and its inherent intermittency. It is the responsibility of transmission and distribution operators to keep the whole energy system balanced, but how do they accomplish this when unstable energy sources are introduced into the mix?
There are a variety of strategies for keeping the grid network balanced, one of which is energy storage. Energy storage can address several grid applications—the three that we’ll look at here include ramping, frequency regulation and synthetic inertia.
Ramping/ramp rate control
Improving the efficiency of existing and new traditional fossil fuel energy generation plants is a critical step to reduce both emissions and costs. For the most part, conventional power plants have generating capacity ready to be turned on or in idling mode and ready to be ramped up when there is high energy demand on the grid. This portion of capacity increases plant capital and operating expense as it represents additional generators and additional fuel consumption.
Energy storage can be deployed to mitigate the need to add additional generators or maintain generators in idle mode, as storage can provide instantaneous power when the grid needs it. The decision to deploy a battery, ultracapacitor or hybrid battery-ultracapacitor energy storage system for this function would depend on how fast the ramp rate needs to be and how flexible this type of generation would need to be to jump into the market.
Energy storage supports utilities’ efforts to modernize the grid as fossil fuels move offline and renewable energy makes its way to the forefront.
Fast frequency regulation
The grid system has a frequency that must be maintained to ensure consumers are provided with consistent power. In Europe and most other parts of the
world the grid is on a
50 hertz frequency system. The U.S. has a
60 hertz system.
Heavy rotating machines have been the conventional method for generating energy, and these machines run on a 50 or
60 hertz basis. When demand on the grid is higher than what generation can provide to the market, the generators work harder and reduce their generation speed, which creates a frequency deviation. Most of the devices connected to the grid system are adjusted to this frequency, and when the frequency sags by as little as 49.95 hertz, it already starts causing issues on the network.
If this fluctuation continues, the more consumers and devices will drop out of the grid system, causing a chain reaction that could result in a blackout.
Meters detect this type of situation. When utilities have insight into when frequency deviation is occurring they are able to inject a huge amount of power into the grid for a short timeframe, giving the grid more time to ramp up other generating systems, which can take a number of seconds before these additional systems are able to take over the extra demand on the grid.
Ultracapacitors (supercapacitors) are a suitable technology to bridge the power gap for that critical interface of many seconds, providing fast-responding high-power output to regulate frequency and prevent disruptive sags. There are few competing technologies that are attractive for this application in terms of footprint, size, and cost for high power, short-term power provision. It doesn't matter if this is on the utility level or transmission level, distribution level or microgrid. Frequency needs to be maintained on all levels.
On a weak grid with weak infrastructure, frequency deviations happen spontaneously and are not foreseen. This is why fast-reacting energy storage is important for getting our grid up to speed with modern demand. In Australia, an entire power plant dropped off the grid, creating a situation where demand was higher than the generation provided. This is a frequency deviation problem that can be resolved with energy storage.
As mentioned before, conventional generation is accomplished by rotating machines that have heavy masses that aren’t able to stop instantly. These masses continue rotating despite fluctuations and contribute inertia to maintain grid frequency. However, renewable generating resources such as solar and wind—a growing portion of the energy mix—do not provide inertia. Therefore, we face a shortfall of inertia which must be provided by another source to keep the grid balanced. Energy storage provides "synthetic" inertia by feeding power into the grid that normally would be maintained by large rotating masses. The application of ultracapacitors for this function gives renewable energy sources the ability to provide what the conventional generators were originally providing and therefore facilitates additional renewable resources onto the grid.
Utilities have a good view of what daily/monthly/yearly consumption looks like. They know where they need to install energy storage to deliver the right amount of power at the right times. Energy storage combined with renewable energy achieves synthetic inertia by injecting large amounts of power into the grid during the critical moments of peak demand.
There are many other grid applications that energy storage is designed to support, which we’ll leave for later posts. Until then, here are some related articles that provide further insight into energy storage for the grid.
Key Account Manager, EMEA
About this author
Dipl.-Ing. Jan-Hendrik Ernst is
key account manager, EMEA at Maxwell Technologies. Ernst specializes in energy storage system design and consults EMEA clients employing ultracapacitors for a variety of grid energy storage applications, including wayside storage for rail, peak shaving for heavy industry, UPS bridging power, and battery preservation. Ernst consults clients from the design-in phase through the completion of the storage project, providing his expertise in deploying full ultracapacitor storage systems and in the hybridization of grid solutions with batteries. He is a member of the European Association of Storage of Energy (EASE) and is currently contributing research on the role ultracapacitors will play in the grid for the EASE European Energy Storage Technology Development Roadmap for 2030.
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