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depend too much on subsidies alone. Hence both costs and regulations also need to be
changed to attract future investments on ESS.

6.3 Remote power systems
Microgrids and nanogrids represent the denominations of modern power grids. These
systems differ only based on their sizes with nanogrids with power capacity of 100 kW
and less. These systems are built on a bottom-up paradigm representing a network of
nanogrids interconnected to deliver power. They may be grid-tied or operating isolated
as remote systems. Most remote systems depend on diesel generators to act as backup
power, which contribute further to pollutions and fossil fuel dependence. ESS can help
replace them and reduce the cost of electricity but they will have to be equipped with
sophisticated control systems. The business case of ESS for remote operation will be
based on its ability to optimize renewable power generated from the participating gen-
erators. ESS in remote systems are very similar to those in Utility sector with the dif-
ference that, the ESS in remote systems will be of a more critical nature.
Difficulties: Many issues exist which may vary from local taxes, insurance to theft,
and other weather conditions. Diesel and natural gases generators still deliver required
energy and power at relatively low costs. Hence to make the ESS more competitive,
the developers need to plan their ESS to implement multiple services and tap diverse
revenue streams. Remote systems will broadly include rural electrifications also, and
the main hindrance in this is the persisting inability of village people to afford the
expenses for these systems. Strong dependence on government subsidies obstructs the
growth of private competitors.
Table 8.2 gives an overview of various ESS and their applications supported with
observations. Following this, certain selected case studies of storage systems operated in
the field for the various applications are presented as discussed in the previous section.
It is pertinent at this point to imply that different applications can be suited for dif-
ferent storage technologies and as such one application may sometimes require usage
of two or more storage devices implemented in a hybrid form. Such Hybrid ESS have
seen vast studies carried out in recent years, a review of which is presented in [15].
They can be implemented in different topologies as shown in Fig. 8.3, where
(A) shows two ESS connected in passive parallel mode,
(B) shows two ESS connected in cascade mode, and
(C) shows two ESS connected in active parallel mode [16].

7 Case studies

Many energy storage projects have been operational with renewable systems glob-
ally and the Department of Energy (DOE) maintains the updated database on global
energy storages [17]. Some case studies are presented below:
1. Off-grid frequency response in Alaska: Younicos delivered 3MW/750 kWh lead acid stor-
age battery system for integrating wind power in an off-grid isolated site in Alaska [18]. The