Balancing the electricity load is a difficult job. The hard part is maintaining that portion of the system that often sits idle but which is necessary to meet high energy times.
Enter energy storage, where the electricity can be housed during periods of less demand and then subsequently set free when it is needed most. That, in essence, contributes to a more efficient production and delivery process while also adding to the potential for alternative sources. Stated differently, users can power-up with a “battery” or other device instead of directly from a congested grid or maxed-out power plants.
Energy storage gives utilities, power marketers and large commercial or industrial customers the flexibility to respond to power shortages, price spikes or brownouts. Utilities, for instance, must precisely measure their load generation with the demands of their end users — a difficult task given that energy usage fluctuates, particularly at industrial sites that routinely implement new processes. Without adequate capacity, all wholesale buyers of electricity would be subject to the whims of the market.
“Adequate deployment of storage technologies can materially reduce power fluctuations, enhance system flexibility, and enable greater integration of variable generation renewable energy resources such as wind and solar power,” says Steven Koonin, under secretary for science at the U.S. Department of Energy, in congressional testimony. “Energy storage can also help stabilize the price spikes that occur during times of peak demand, and can delay or potentially avoid the need to construct capital intensive facilities and infrastructure that use conventional fuels and produce greenhouse gases.”
Koonin explained recently to the Senate Committee on Energy and Natural Resources that despite a large number of existing energy storage technologies, there are only a few practical applications. One such example is gravity storage that pumps water and is best for larger projects. That method, however, is time consuming because it takes large amounts of water to work, thus limiting its ability to function all the time.
In the case of pumped hydro projects, turbines push water into reservoirs at night and then release it during the day when demand is highest. Missouri is supposed to have a 440 megawatt pumped hydro project built next year.
A second technique is mechanical kinetic energy storage, which works using flywheels. Unlike pumped water, it is practical for certain short term requirements, adds Koonin. Such applications involve flywheel systems that can achieve very high energy densities, he notes, although the physical constraints on those storage devices curtail extended activities such as peak shifting. Currently, six 1-megawatt flywheel projects are being tested in the United States and mostly in New York State and California. Beacon Power recently broke ground in New York on the nation’s first full-scale 20-megawatt flywheel frequency regulation plant.
“In some applications, storage devices must be able to sustain full charging or discharging of power levels for two to six hours,” says Ralph Masiello, senior vice president of energy systems for consulting firm KEMA, at the hearing.
Expensive Issues
Altogether, the federal stimulus plan is providing $185 million to 16 energy storage demonstration projects. Meantime, the Energy Department’s Office of Science is also working to advance battery technologies.
As a practical matter, utilities may find energy storage to be a more cost effective solution than system upgrades. Targeted applications such as those at individual substations may be among the first uses for the technology. In 2006, for example, American Electric Power and the Energy Department teamed up to do just that at a substation in West Virginia: Energy is stored at night and released over a six-hour time period during peak demand times.
And while the overall objective of storage is to optimize the electrical system, focus is now on using it to grow renewable energies that can be variable in nature. Indeed, the National Energy Policy Recommendations published by electrical engineers have said that if wind and solar are to reach their potential then large-scale storage devices must be developed and deployed.
“The current electricity system can absorb much greater quantities of renewable generation than are currently deployed without significant increases in the deployment of storage technologies,” says Robert McGrath, deputy laboratory director for the National Renewable Energy Lab. “Currently, storage technologies do not exist that can be cost-effectively deployed in the diversity of applications that are anticipated. We must increase our research and development efforts in the near term.”
To be sure, the technologies to allow for energy storage are in their infancies. And, even if they can be shown to work, there are still downsides to using them. At this point, it is difficult to gauge just how efficient such devices are as well as their potential environmental affects.
It’s a technology, for example, that gets its energy supply from a generation source and must therefore be used in combination with either central or distributed generation. At the same time, batteries are now relatively expensive and have a limited life expectancy.
Industry, though, insists that it is eager to advance the cause — to go from smaller demonstration projects to those that are more substantial. Through the public-private partnerships established under the stimulus act, energy storage enthusiasts are upbeat. If pending projects perform then that would have far-reaching implications: Utilities would not just have more efficient assets. They would also avoid some capital intensive upgrades while integrating more green energy into their grids.
The country, then, would be one step closer to being energy independent and more climate-friendly.
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