Transmission and distribution (T&D) deferral is a key application for energy storage. A common example is deferring the upgrade of a substation by co-locating a battery at the site. This has been demonstrated at several sites, including by AEP in Ohio, Texas, and West Virginia, and by TEPCO in Japan. In these cases, NGK Insulator’s sodium sulfur (NAS) batteries were used to defer the upgrade of the substations. The value of such “virtual upgrades” for energy storage is direct and obvious enough to justify to public utility commissions or other stakeholders.
Other examples for energy storage include wind and solar integration. As new regulations encourage wind and solar project developers to firm up capacity of intermittent resources or developers seek to maximize their installed capacity, new opportunities for energy storage technologies will arise.
Suitable applications include wind ramping, solar firming, peak smoothing and others. The value of these applications for storage are less straightforward to pin down. Certainly smoothing instability from intermittent resources is a good thing for the grid; but is there an incentive (regulatory or monetary) to do so? In many cases there’s not, or it’s not obvious. Likewise, are intermittent resource developers obligated to maximize the capacity factor of installations in order to turn a profit? Again, the answer is rarely.
One application highlighted by speaker Jim Robb of Northeast Utilities at the Energy Storage Summit in Houston last week brought the two together: T&D deferral to connect remote, intermittent resources to load centers. From the perspective of T&D utilities, new transmission lines to remote resources such as wind farms are often hard to justify. In Robb’s example, the cost of a transmission line to bring wind-generated power from mountainous New Hampshire to load centers in Connecticut and the Boston area added $.06 per kilowatt hour to the cost of electricity from the wind installation.
In addition, because the new transmission line would not increase reliability or improve congestion, it would be classed as an “economic” project, which is more difficult to get funding for in the first place. Robb ran several scenarios, assuming nearby small pumped storage installations, and the results were fairly intuitive: by including storage a wind farm can be “oversized” relative to the available transmission line, the wind asset can take fuller advantage of the transmission line, and the overall transmission cost decreases. This is largely thanks to the increased capacity factor for the wind farm when wind is coupled with storage.
This type of T&D deferral is important for several reasons: It maximizes intermittent resources, opens up T&D deferral applications to materials-based energy storage (as opposed to electrochemical storage), addresses the infrastructure issues of intermittent renewables, and gives storage a clear business case for renewables integration.
Tags: Distributed Energy, Energy Storage, Renewable Energy, Transmission & Distribution, Utility Innovations
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