IEEE Electrification - December 2021 - 48

installed in home appliances. Each type and size of ESS has
specific uses, operation requirements, and challenges. In
this article, we discuss the utility-scale shared energy storage
(USES) battery systems that are operated by a distribution
utility and available for use by customers under
various business models-not to be confused with community
energy storage systems (CESs). USES systems provide
fractional storage to customers under various
metering, pricing, and billing approaches. Generally, there
are three levels of battery-type ESSs that have been used at
the distribution-system level: at-home, CES, and USES.
ESSs at home can be either directly behind the meter
(BTM) or at the point of connection for home appliances.
CESs are usually installed at the secondary side of distribution
transformers and used by groups of customers (e.g.,
homes on a residential feeder and commercial buildings).
USES systems are much larger than CESs and installed at
the substation. They are usually owned by utilities or investors.
Figure 1 shows the applications of battery ESSs at different
levels of an example distribution system.
USES systems provide many advantages over CES and
BTM storage systems: USES systems are more flexible and
less expensive than other types of ESSs for comparable
sizes, can offer grid service at scale, improve grid reliability
and resilience at scale, and reduce fire and other hazards in
homes. Photovoltaic (PV) owners and other community
members can purchase a fractional portion of a USES system
to help manage their premise load and electricity
bill. This fractional portion operates as a virtual storage
block allocated for customer use. However, there are many
challenges in the development of USES systems. These
challenges include developing
technology and business
processes that effectively manage energy flows for both customer
use and grid services use cases. The principle among
the challenges is to determine the optimal charging/discharging
schedules for the virtual storage blocks and the battery
as a whole while considering both the customer rate structure
and the economic value derived from grid services.
History
As mentioned previously, a variety of ESSs have been used
at different levels. The choice of a given energy storage
device depends on the needed application, although here
we are mostly interested in the grid applications that provide
grid services, and at the customer side, for demand
flexibility. Large storage systems, including pumped
hydrostorage and compressed-air energy storage, have
been developed and deployed for decades. However, until
EMS
Commercial
Residential
CES
USES
EMS
EMS
EMS
Load
PV
Figure 1. The applications of (battery) ESSs at different levels: USES, CES, and local residential and commercial ESSs.
48
IEEE Electrification Magazine / DECEMBER 2021
Substation

IEEE Electrification - December 2021

Table of Contents for the Digital Edition of IEEE Electrification - December 2021