Interview: Duke Energy storage head Zak Kuznar

It has been a busy summer of storage for Duke Energy.

Last month, the utility completed a 9MW lithium-ion battery system in Asheville in North Carolina (pictured), the state’s largest. It also committed to build three storage projects totalling 30MW in Florida, including an 18MW/36MWh system at its Lake Placid solar project.

In addition, Duke has helped the solar industry in North Carolina and South Carolina to unlock the process for developing ‘several hundred megawatts’ of solar projects in the states in 2021 and 2022. This is likely to support additional storage capacity.

That’s why Energy Storage Report thought it was time to catch up with Zak Kuznar, managing director of energy storage and microgrid development at Duke Energy. He talked to us about the company’s growth plans for storage in the six states it serves; the development of long-term storage systems; and the wider potential of the sector.

Kuznar has been with Duke since 2008 and started working in storage in 2012. That first involved developing small projects of a couple of hundred kilowatts each, and has since expanded to the likes of the 9MW Asheville and 18MW / 36MWh system at Lake Placid.

These are not comparable in size to some of the 100MW-plus systems in schemes in California and Texas – but there are two good reasons for this.

First, there is far less renewables capacity in the states where Duke operates than California or Texas. The utility serves 7.4million customers in the Carolinas, Florida, Indiana, Kentucky and Ohio. Less renewables means less capacity to balance – and therefore less need for storage systems to do the grid balancing.

Second, there is no integrated electricity market in the southeast US that enables the supply or trading of power across state lines unlike, for example, PJM in northeastern US.

That means smaller storage projects tend to be more appropriate for grid balancing: “We’re not in a market there, so a lot of our developments here are driven by Duke Energy building and deploying storage in a lot of different use cases,” he explains.

He says Duke’s priority so far has been developing the use cases for storage, so it can boost reliability of distribution by putting standalone systems at the right points in the grid; or manage fluctuating production at its solar schemes by pairing the two. It has also seen the average size of its storage systems get bigger in recent years.

But what about those larger systems in other states?

Kuznar says they will help further commercialise the industry and ultimately support more storage across the US: “Once you see more and more in the field, it’ll become more commonplace,” he says.

He adds storage will be “a very big part” of the utility’s drive to cut its emissions 50% by 2030 compared to its 2005 levels, and 100% by 2050.

Technology evolution

While the sizes of Duke’s storage projects have grown in the last few years, Kuznar says there are still areas for further evolution. This includes expanding from shorter-duration lithium-ion battery systems, which have been the bulk of its storage projects so far, to longer-duration systems.

This is a wider industry trend: “From the industry side, I think the driver is going to be more long-duration storage,” he says.

So far it has looked at zinc-based systems, such as the 30kW/120kWh it has tested with Eos Energy Storage since last summer, and potentially flow batteries too. Duke also has two pumped-storage hydro plants in its portfolio, but they can only be built in hilly areas so aren’t suitable everywhere.

He says is vital for the market to bring more long-duration electromechanical systems to commercial maturity.

And there’s another popular talking point in storage now: tax credits. The US federal government has confirmed it is looking to give investment tax credits for standalone energy storage schemes. Kuznar says these are an important mechanism because they can help to put utilities and other developers on a level playing field.

As Kuznar and company aim for $600m investment in 375MW of storage across its regulated businesses, there will be more busy summers.