Breakthroughs in battery technology aren’t the whole storage story

Kathleen Wolf Davis | Oct 21, 2013


Article written by David Mohler


There is a lot of buzz surrounding energy storage and a lot of progress has been made to make it a valuable resource for the electric grid. But our work to seamlessly integrate storage within a diverse grid ecosystem and unlock its full value is just beginning.

Duke Energy has been involved with energy storage projects that range from major renewable sites to community storage projects. We’ve worked with all sorts of battery manufacturers and have seen the hardware get better and cheaper.

But for the electric grid, that’s not the whole story. The best battery is only as valuable as the benefits it brings to the grid. And as appealing as these values are as a concept, real-world value is often more difficult to achieve.

To date, much of the work in the energy storage community has focused on the hardware side of the equation. There have been successes. Battery prices are declining ,performance is improving, and systems are getting easier to install on the grid.

But the other side of the equation--how to create value on the grid--is just beginning to be addressed. This is the realm of power system engineers and utility operators--the folks with experience in grid operations and those you are just beginning to see at energy storage conferences.

Utilities have been busy hosting a number of demonstrations and test projects with energy storage on the grid. The primary focus has been on the physical deployment and operation of hardware systems, coupled with a demonstration of basic functions that storage systems can provide to the grid.

While some utilities have started to venture beyond the basics, we need greater focus on finding better ways to quickly, inexpensively, reliably and repeatedly deploy energy storage into a utility ecosystem and to create technical and business value with it.

At Duke Energy, our focus now is not so much looking for the next great battery, but finding out how to create the best value for the grid and our customers. Better yet, how do we make energy storage tackle a number of tasks for the grid – instead of being a “one-trick pony” concentrating on a single area?

In Notrees, Texas, our 36-megawatt advanced lead acid battery is part of a pilot in the ERCOT region – shaping the ancillary service market for fast-responding resources. The installation is next to one of Duke Energy’s wind farms in the state, and combines both grid stability and grid services in a meaningful way.

In Gaston County, N.C., the Rankin Energy Storage System deployed a battery three miles away from a commercial solar site in a retail substation to test the viability of circuit-level intermittence smoothing. This enables the energy storage system to address minute-to-minute intermittence from potentially hundreds of distributed solar facilities without needing to locate storage next to them all. Maybe energy storage at distribution substations could be the norm going forward.

While the Rankin system has been using real-power capability to smooth intermittence on a 12kV circuit, the inverter’s reactive capability has stood idle – until now. Rankin is now being used to demonstrate an algorithm that uses real power for circuit power-swing mitigation while using the reactive power capability to improve the circuit’s power factor.

Energy arbitrage is a simple concept to understand and even execute with a grid-tied battery, but it rarely creates enough value to justify the storage investment and it can cause interruptions on the circuit to which it is interconnected.

At Duke Energy’s Marshall Energy Storage Project, we’re deploying a combined smoothing and shifting energy storage algorithm that will enable a single battery to shift energy for arbitrage and also limit the disruptive minute-to-minute output swings from a solar facility. This battery system will soon work in conjunction with a smart solar inverter to show how different technologies can work together to achieve even greater benefit.

At our McAlpine Energy Storage System in Charlotte, N.C., an islandable microgrid tied to a 24kV distribution circuit, will be deployed in late 2013 to demonstrate how a utility-owned distribution asset can support the grid and provide higher reliability to a critical customer – all using highly-utilized utility assets.

We are also exploring ways to use energy storage to complement a variety of new technologies. At Clay Terrace Shopping Mall in Carmel, Ind., we linked a solar array, battery storage unit and electric vehicle charging station to demonstrate a sustainable microgrid that can be used by a commercial customer to attract additional business.

These examples aren’t dependent on the latest and greatest battery technology. They’re based on how utilities can take the technology being developed and figure out how to incorporate it onto the grid to create value for utilities and customers.

Battery technology and the electric grid have come a long way in a short period of time. It’s up to utilities and our partners to keep the momentum going.

David Mohler is vice president, emerging technology with Duke Energy. 


Photo courtesy of Duke.


Mohler gave us an insider look at Duke in this article. Do you work at a utility? We'd love to have your insider view in our next article and e-newsletter. E-mail editor-in-chief Kathleen Wolf Davis with your ideas:

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