down in late afternoon just as demand is reaching its peak. Storing electricity at midday for use in the evening could limit the
need to power up peak-generation plants.
Not surprisingly, California, which has the nation’s highest
rooftop-solar penetration rate, is interested in exploring such a
time-shifting approach. In fact, the state’s three major investor-owned utilities face a mandate from the California Public Utility Commission to collectively purchase 1. 3 gigawatts (GW) of
energy-storage capacity by the end of 2020.
“In California, they have so much rooftop solar that, in the
afternoon, they’re actually turning down the solar. They’d like
to be able to store that electricity in the afternoon,” Crabtree
said. He cited the contract Advanced Energy Storage (AES)
won from Southern California Edison for one of the company’s
containerized Advancion Li-ion energy-storage systems with
a capacity of 100 megawatts (MW) as an example. “That could
be a harbinger of what’s to come.”
Eos Energy Storage is another manufacturer seeking to
crack the utility-scale market. However, its batteries feature
a different, zinc-and-water-based chemistry called “Znyth,”
which the company developed with time-shifting in mind. The
Aurora 1000|4000 [( 1,000 MW, 4,000 MW-hours (MWh)],
featuring the technology, launched in January, and Eos has
since received inquiries and qualified orders totaling 8 giga-
watt-hours (GWh), or approximately 2,000 Aurora units,
according to Philippe Bouchard, vice president for business
development. Commercial delivery won’t even begin until
2016, but the price point of $165 per kilowatt-hour (k Wh)—
almost $100 per kilowatt-hour cheaper than Tesla’s PowerPack
utility-scale product—has utilities from around the globe lining
up for a look.
“This is a chemistry and a technology that’s been designed
specifically for grid-connected applications,” Bouchard said.
The Aurora units can support a continuous four-hour discharge and, like AES’s Advancion system, are containerized to
enable easier shipment and installation anywhere a distribution
system requires “locational” capacity—for example, in areas
with high solar penetration, where the evening ramp-down in
electricity production might be particularly problematic.
Though their power requirements aren’t as demanding as a
utility’s, commercial building owners also represent a market
for energy storage. However, unlike residential utility customers, commercial customers generally face a “demand charge”
based on the 15-minute period in the month or year during
which their electricity demand is highest. So, instead of shifting electricity production, these users are seeking to even out
their demand peaks. This goal requires different functionality
from their battery systems.
Battery systems, straight from the ‘factory’