Page 164 - Hybrid-Renewable Energy Systems in Microgrids

148 Hybrid-Renewable Energy Systems in Microgrids

2 Energy storage systems

ESS are the most needed support system for integration of renewable power sources
into the grid. Flexibility can be achieved in power systems only when the generation
and the demand side become flexible with storage systems acting as the mediators
managing their interconnection. Renewable systems can be utilized most efficiently
only if tapped when available; else, they lose their potential. Also, they do not have
any provisions like governor controls for managing frequency and power changes.
ESS help in rendering this inertia to the renewable systems from grid frequency varia-
tions which enable the power system faster recovery from unplanned deviations of
demand and supply [5,6].
Wind and solar are the widely advocated ones of the renewable sources and both
suffer from intermittencies and unpredictability issues as mentioned earlier. When
renewable systems spread across a large area are interconnected, they can effectively
manage the invariabilities of their energy sources. Also, advanced power electronics
can be utilized to provide synchronization with the grid and mimic conventional gen-
erators as per the US National Renewable Energy Laboratory [7]. In such cases, ESS
enable flexible operation and smooth integration of the distributed generators with
the utility grid. Such systems improve the dispatch ability of the wind or solar power
generated at the production site and can be utilized at peak times.
Conceptualization of modern power grids like microgrids, smart grids, and
nanogrids cannot be achieved without support from ESS which will act as crucial
backup reserves and ancillary support for the participating power sources. Need
for ESS arises in every stage of power planning like generation support, ancillary
support, power backups, demand side management, and seasonal storage. Like-
wise, there are many types of storage systems available, which are characterized
by distinct features suitable for varied applications in the modern power systems.
However, the importance of ESS in the future grids is yet to be recognized and
appreciated.

3 Need for ESS

The electricity market has an immense impact on the storage systems operating un-
der it. Electricity networks vary in infrastructure and operations depending on the
economic and living habits of the customers. They are also influenced by the grid
specifications and configurations prevalent under conditions [5].
1. Spinning reserve and short-term backup: Coal and fuel-based power plants provide for
the spinning reserves in a conventional power system. ESS can act as spinning reserves in
HRES DG’s to aid in ramping up of power when needed. They can respond in a short span
of time ranging from minutes to seconds whereas fuel-based systems need considerable
amount of startup and ramp up times.
2. Load leveling and peak shaving: In case of renewable systems, energy is produced only
at the time of availability of the natural source, which may not necessarily be the time of