Some people hear the word “storage,” and all they think of is batteries. Most utility people aren’t that short sighted. They’ll remember mechanical forms of storage, like flywheels or the water trapped behind a dam. But – and I admit I’m a little partial here – I think the most efficient storage is process storage, or the storage inherent in the flexibility of controlled loads.
Given the choice between using peaking generators, battery storage or a process storage mechanism like the Enbala network, you can’t beat process storage for delivering great energy efficiency. A peaker plant located 300 miles away from the problem will experience line loss on top of the thermodynamic inefficiency of the plant itself, which can hover below 50 percent.
And, on the cost basis, process storage is far more affordable than grid-scale battery storage, and has different characteristics. The round-trip efficiency of the process storage is actually quite high. With batteries, you’re taking a device, taking energy off the grid to charge up that device, going through the necessary AC/DC conversions, then releasing that energy back into the grid at which point, again, you have energy conversions occurring.
The Case for Leveraging Process Storage
Process storage has high round-trip efficiency because there are no conversions involved. You’re just letting the system do work it was going to do anyway, whether it was chilling a building down, heating up a tank of water, pumping water from point A to point B, or supporting the grid because the grid operator called a device into action. Energy storage devices like batteries, they may be great as shock absorbers for the grid, but don’t forget about round trip efficiency.
What does process storage look like from an energy profile standpoint? A battery has a very good power profile. It can respond to a power signal or a disturbance from a power systems perspective very, very quickly. But in terms of its energy storage, well, that’s still quite low at this point. Even the bigger devices have only around five-hour longevity. With process storage, there are some resources that can be very fast, although they generally won’t be as fast as a battery. However, the energy capability is much longer than battery storage, so the power signatures are different.
Brave New Approaches for a Brave New World
I believe that in this world, this new grid world, the grid-edge world, it's going to be a combination of multiple approaches that will fix a lot of the decentralized grid problems we now have. I’m not against batteries; I just think process storage devices should be considered in that same category, because at bottom, it is a virtual storage resource when controlled by a network that can leverages its capabilities.
Add in smart solar inverters, and then you have a network can support system voltage quickly, too. At that point, you have a system for regulation service, flexibility, contingency, energy and capacity. It’s a comprehensive approach that can benefit utilities, grid operators and their customers alike.
by Malcolm Metcalfe
Enbala Founder and CTO