POWER May 2012 - 88

ENERGY STORAGE
The electricity grid is described as the
world's largest machine, or a just-in-time inventory
system, because electricity per se cannot
be stored, although it can be stored as energy
in other forms. It bears noting that 22,000 MW
of PHS already operates throughout the U.S.,
and one CAES facility has been operating for
almost 20 years. However, virtually all of these
facilities were built by vertically integrated utilities
before policies encouraging competition in
electricity supply were enacted.
In practice, the benefits and value streams associated
with balancing, or " shock absorption, "
vary greatly, depending on the location within
the transmission or distribution system (and the
differing voltage levels) where balancing is conducted.
Now that electricity supply and delivery
has been disaggregated, the value and benefits
accrue to different stakeholders. However, the
problem is similar to the inability of certain
transmission projects to move forward because
it was simply too difficult to apportion the value,
and recover the costs, to/from each class of
ratepayer that would benefit from having the
transmission line in place. Thus, through the
leadership and initiatives of several independent
system operators (ISOs), FERC instituted Order
1000, which allows approved " multi-value "
projects to recover costs through an adder on
transmission tariffs across the region. Methodologies
have been developed and approved that
quantify the value of these regional benefits.
Proposed Solutions and CAREBS'
Functional Approach
At the federal and state levels, myriad policy
solutions have been proposed, and some
instituted, to support the addition of energy
storage facilities, including:
■ Creating markets for grid ancillary services,
the most accepted thus far being frequency
regulation (for example, in PJM,
MISO, CAISO, and NE-ISO).
■ Creating new market products, such as
ramping or flexible ramping in the organized
markets to reflect the response value
and flexibility of storage (in CAISO,
MISO, and others).
■ Allowing an investment tax credit for storage
facilities (Storage Technology for Renewable
and Green Energy Act of 2011,
S.1845, pending before Congress).
■ Reducing the interval for bids into the
market to sub-hourly to accommodate socalled
" Limited Energy Storage Resources "
and creating a " real-time " regulation
market (New York).
■ Mandating or encouraging a minimum
level of storage capacity in the market, that
utilities procure a minimum level of storage,
and that methodologies be developed
to assign a " resource adequacy " value to
storage, as is common for generation and
transmission resources, and institute pay
for performance and forward procurement
of flexible capacity (California).
■ Defining electricity used to charge storage
devices as wholesale not retail (Texas).
■ Creating a " national interest value " tariff
that would support distributed storage
(National Alliance for Advanced Technology
Batteries proposal).
As a complement to these initiatives, The
Coalition to Advance Renewable Energy
through Bulk Storage (CAREBS) advocates
a functional policy solution that:
■ Simplifies the task of integrating renewable
energy into grid operations without further
distorting existing ratemaking or market
mechanisms, or sacrificing reliability.
■ Avoids picking winners and losers and protecting
existing or future asset classes by
focusing on the grid or market functional
need and not the technology or the asset.
Conventional generation technologies cannot produce all the ancillary, balancing, and other services required
by a modern grid. Source: CAREBS
Generation technology
Services
Traditional
ancillary
services
Regulation
Energy imbalance
Spinning/operating reserve
Black start
Reactive power
Reliability reserves
Supplementary reserves
Additional
" balancing "
services
Other
desirable
attributes
Notes:
a. Bulk storage is the only solution set capable of providing all the components of regional balancing for grid management.
b. Technologies not yet scalable and economical for large-scale regional balancing service, but appropriate for distribution-level balancing.
c. Fast-acting (or " flex " ) gas turbines respond faster than earlier models but are less efficient and have worse emissions profiles at part load.
d. Cycling older coal-fired plants can provide some ancillary services, but under aggravated emissions profiles and typically significant metallurgical damage to major components
and high operating costs.
e. Interrupting customer load through demand management programs can help balance the system, but typically for regional balancing, a substantial amount of load must participate
at the same time.
f. Synchronous condensers can absorb load from the grid but can't return it.
88
www.powermag.com
POWER | May 2012
Absorbing load, decremental reserves
Transmission line loading optimization
Shifting on-peak to off-peak
Avoiding transmission upgrades, investment
Weekly balancing
Seasonal load shifting
Bulk storage
(PHS, CAES)a
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Distributed
storageb
N
N
N
N
N
N
N
N
N
N
N
N
N
Gas turbines,
combined
cyclesc
Y
?
N
N
N
Y
Y
N
N
N
N
N
N
Cycling older
fossil plantsd Hydroelectric
Y
Y
Y
N
N
N
N
N
N
N
N
N
N
Y
Y
Y
N
?
Y
Y
N
N
N
N
N
N
Demand
managemente
N
N
N
N
N
Y
Y
N
N
N
N
N
N
Synchronous
condensersf
Y
N
N
N
Y
N
N
Y
N
N
N
N
N

http://www.powermag.com

POWER May 2012

Table of Contents for the Digital Edition of POWER May 2012