Energy Storage: Can It Replace Transmission?

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By Rick Fioravanti

Grid-scale storage offers potential benefits to transmission and distribution systems of utilities in regulated and market environments. These benefits derive from cost reductions due to the time and location shifting of energy for congestion relief, reliability via enhanced stability and outage response, and incremental voltage support—once the storage device and its power electronics are in place.

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Between the transmission and distribution systems, at the subtransmission or distribution substation, storage can defer capital expenditures for power transformer upgrades to meet peak load conditions. In remote areas served by radial subtransmission, storage can also be a vehicle for reliability improvement as a way to ride through un-cleared faults on the transmission line(s) that serve the substation.

The potential T&D CapEx deferral angle is an interesting area to explore. One example for a substation application is to support power transformer contingency operations during peak load periods that have grown in excess of the N-1 contingency capacity of the station.

This potential application, however, suffers from the same barriers today as the transmission congestion relief application:

·         The planning and operational methodologies are not established

·         The regulatory process for approval is nonexistent

·         It, again, crosses the boundary between transmission and distribution regulated functionality and merchant functionality, because it potentially shifts off-peak energy to on-peak delivery.

In addition, as this typical substation application is likely to be in the range of 1-10 MW, it may not require centralized storage systems, but rather distributed or utility-scale devices. As previously noted, these could be portable or semi-portable in nature.

One More Hurdle … For Now, At Least

An additional hurdle that needs to be mentioned is costs. One reason multiple roles are applied to a storage device is for a means to create additional revenue that can defer initial cost for the technologies. However, this hurdle needs to be evaluated in the context of an emerging technology and not “set” at current levels.

Advanced energy storage technologies are still in a rapid state of evolution and development.  Hence, when comparing options, solutions for areas such as CapEx deferral need to be weighed not only against today’s current options, but also with expected prices of future technologies. The intent isn’t to mask cost as a hurdle; rather, there are a number of different technologies nearing demonstration stages that have potential to alter the current cost of devices. This perceived “cost” hurdle may become a moot point in the near future.

Storage is not yet in widespread use to the point that it could serve as a consistent application to defer new transmission. As challenges of siting new transmission continue though, additional modeling of energy storage going forward can help to understand its benefits for a given capacity challenge better.

Note: This post includes excerpts from KEMA’s Utility of the Future leadership guidebook “The Promise of Energy Storage.”

Rick Fioravanti is Director of Storage Applications & Support at KEMA, which is a leading authority in energy consulting and testing and certification. Contributing authors: Ralph Masiello and Ali Nourai.

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