Distributed fast-cycling energy storage is an excellent technology for grid regulation applications, while vast banks of deep-cycling batteries perform standby backup for critical loads throughout the grid. In the past, a different type of storage was needed for each case. But emerging lead technologies might now allow us to solve both problems simultaneously.
As the energy-storage market matures, a few technologies are emerging that can provide safe, large-scale energy storage optimized for both fast-cycling and deep-cycling. The technological shift suddenly allows innovative co-investment strategies between energy retailers, utilities and end-customers, all of who can benefit from large-scale storage infrastructure. With so much stand-by capability sitting on float around the world, it’s a tantalizing thought that it might be possible to utilize it 24 hours a day.
While many eyes are turning toward lithium-ion, new lead technologies have quietly emerged that add continuous high-rate cycling to lead’s existing stand-by capabilities. One leading example, the UltraBattery technology, incorporates a carbon-based ultracapacitor into the chemistry of its lead cell, producing a hybrid technology which outperforms both leads and ultracapacitors (as well as most other competitors). Such technologies extend the application suite for lead while maintaining the power, dependability, safety, recyclability and closed-loop manufacturing that characterizes world-class VRLA cells.
Utilities require a “standing army” of backup generators to provide large power injections on-demand during frequency-variation events. This power has traditionally come from fossil-fueled, gas-peaker plants, which can react within minutes to restore balance to the grid.
However fast-cycling battery banks are proving to be valuable providers of this power. The hybrid technology mentioned above, UltraBattery, has proved its capability for continuous grid regulation in the MW-scale. Batteries tend to edge-out fossil generators in this application because:
- batteries are easy to install at any point in the grid (as well as being very safe and environmentally sustainable in the case of lead cells);
- batteries react instantaneously so that request and response coincide, making frequency regulation more effective; and
- unlike generators, batteries are able to inject power into a sluggish grid when grid frequency falls and store energy to rein back an overpowered grid when frequency rises.
The grid’s requirements are so strikingly well-suited to battery technology that a 2008 report by Pacific Northwest National Laboratory (Assessing the Value of Regulation Resources Based on Their Time Response Characteristics) found that total frequency regulation requirements in the grid could fall by around 40% if fast-response storage was to replace gas peakers for this task.
While battery powered frequency regulation is a profitable business on its own, fast-cycling lead technology can do much more than handle frequency requests; in fact it has power and energy characteristics to allow it to simultaneously perform other revenue-generating storage tasks. Enter dual-purposing.
Right now in the U.S.A. around 20 GW of lead batteries are sitting beside data centers and critical loads waiting to spring to life if grid power is lost. That’s a lot of idle batteries providing comfort, but earning zero in revenues for their owners. Traditional lead can’t perform frequency regulation on top of their UPS functions because the cycling can prematurely degrade the cells.
Utilities pay well for every kilowatt-hour cycled for frequency regulation applications and the service can be located almost anywhere on the grid. The opportunity therefore exists to use this revenue to offset the unavoidable cost of backup systems. The benefits flow in all directions: Michael Kanellos, writing in 2013 in Forbes magazine predicted that the innovation of dual-purposing could make data centers “one of the best friends of the electric power industry”.
With suitable technology, backup functions are unaffected when the cells cycle for other purposes – if anything they are better guaranteed since active cycling batteries have their cells health-checked minute by minute, whereas a single bad cell in a traditional system may only be discovered when the UPS doesn’t switch on.
There’s an added upfront cost since slight oversizing may be required, but payback occurs quickly, after which the backup battery bank quietly shifts from cost center to profit center.
Frequency regulation is far from the only secondary revenue available.
Batteries can also perform other power-quality tasks like renewable smoothing and weak-grid support. As well they may contribute to energy-management tasks such as peak shaving to help a customer avoid capacity charges and controlled shut-downs, which can allow customers to partake in incentivized demand-side management.
Business pathways even exist for storage to be used simultaneously for frequency regulation, arbitrage and energy-price hedging, where energy-retailer and end-customer find a mutually beneficial ownership model for the storage assets.
Storage is changing the way grids will work and, for the first time, customers are gaining access to backup batteries with revenue streams and a path to system payback.
New economic models and new markets are opening for storage , and with technologies like UltraBattery now reaching full commercialization, lead looks likely to remain the world’s number-one choice for stationary storage.