POWER May 2014 - 26

ENERGY STORAGE
Apples and Oranges
Energy storage facilities are unfortunately
not always described consistently
in media reports and press releases (or
even government data), being typically
rated in terms of power capacity (watts)
and only sometimes in storage capacity
(watt-hours). The approach in this
article is to report both figures where
available, because two " 2-MW " projects
may have very different performance
characteristics despite having the same
rated power.
The distinction is important because
some technologies (such as flywheels)
have high power but low energy, while
others (flow batteries) may be low power
but high energy, and still others (pumped
storage hydro and compressed air) have
power and energy capacities that are determined
by their associated power plants
and volume of available physical storage,
values that unlike other storage technologies
are generally not interdependent.
that the energy storage market was about to
" explode, " adding 6 GW in 2017 and 40 GW
by 2022, with about 40% of this growth occurring
in the U.S. While total capacities are
currently small, events suggest energy storage
is building momentum toward becoming
a key element of the grid.
Policy Developments
Perhaps the single most significant development
driving attention to energy storage,
according to Matt Roberts, executive director
of the Energy Storage Association, has
been the increased penetration of intermittent
renewable generation. " Adding storage
is a way to help with intermittency and peak
load aspects, " he told POWER in March. This
has meant increased demand for methods to
smooth output and respond to sudden drops
in production. Not surprisingly, most of the
policy activity has been in areas with substantial
recent additions to renewable capacity
(Figure 1).
California. In 2010, California passed
legislation instructing the California Public
Utilities Commission (CPUC) to consider requiring
the state's service providers to procure
certain levels of energy storage. Last year, the
CPUC issued a requirement for the state's
investor-owned utilities, Southern California
Edison, San Diego Gas & Electric, and Pacific
Gas & Electric (PG&E), to collectively obtain
1.3 GW of energy storage by 2020.
The targets are broken down into transmission,
distribution, and customer storage,
and will be phased in over two-year periods
starting this year. No more than 50% can be
owned by the utilities, and PSH is excluded
from the mandate. Certain existing projects
can count toward the total, and the program
is designed to encourage a range of ownership
models.
Roberts noted that the mandate incorporates
a lot of storage activity that was already
under way. Many of these projects, he said,
" were coming because they were valuable,
not because they were policy driven. " That
said, " the policy is there to encourage continued
growth after this year and help over
the long term. "
1. Looking to lead the way. After adding nearly 4 GW of renewable capacity in 2013,
California's need for energy storage is growing rapidly. This 4-MW/24-MWh sodium-sulfur battery
in San Jose, inaugurated last year, is a pilot project by the California Energy Commission
and Pacific Gas & Electric Co. Courtesy: PG&E
Coming up with a process for procurement
required some new thinking. The CPUC recognized
that the existing auction process under
the state's renewable portfolio standard
wouldn't work for energy storage, which
isn't simply a block of generation but rather
a range of roles and services that cut across
most grid functions. Instead, the utilities are
to issue " requests for offers " (RFOs) that will
meet defined needs.
Other electricity service providers have
their own marching orders. Entities other
than municipal utilities must procure storage
equal to 1% of their annual peak load
by 2020. Municipal utilities do not have
fixed targets but must instead conduct assessments,
come up with their own plans
for obtaining storage, and submit them for
approval by the California Energy Commission
by October 2014.
The targets, though ambitious, are somewhat
fluid. In the event the RFOs don't
produce bids that meet identified needs, the
utilities are allowed to defer up to 80% of
their targets to the next phase. The utilities
are also allowed to shift targets between categories
to some extent.
New York. This state has long suffered
from significant load congestion around New
York City, where the majority of its population
lives. Most of the city's power is generated
elsewhere and transmitted through a few
narrow corridors. This congestion naturally
causes frequent spikes in wholesale power
prices. Another key concern is the potential
closure of the Indian Point nuclear plant-
the Nuclear Regulatory Commission has yet
to rule on a license extension, and state politicians
have called for its retirement-which
supplies about 25% of the city's power.
In January, the state government announced
a program with Consolidated Edison
(ConEd) intended to reduce the load on
the area grid by 125 MW, in part through energy
storage. The proposed program includes
generous subsidies for storage projects: up to
$2,100/kW for battery storage and $2,600/
kW for thermal storage, with added incentives
for large-scale (greater than 500 kW)
facilities. The state is also investing in a battery
storage testing and commercialization
center in Rochester, a $23 million partnership
between the New York Battery and Energy
Storage Technology Consortium and DNV
KEMA (now DNV GL).
The New York Independent System Operator
(NYISO) has the distinction of having
the first large-scale flywheel-based frequency
regulation plant in the country, a 20-MW/5MWh
facility operated by Beacon Power.
Beacon Power struggled financially when
the plant was opened in 2011, but changes in
compensation for frequency regulation (see
26
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