Page 31 - Energize March 2021

TECHNICAL

Bulk storage of electrical energy in

“grid edge” applications

by Mike Rycroft, Now Media

With growing demand, higher reliability and resiliency requirements, higher penetration of distributed
renewable generation, as well as the development of a more intelligent grid, there is an increasing
requirement for energy storage at points within the last mile and at the grid edge.

he grid edge is generally seen as the area of the network beyond Requirements
the distribution transformer, and includes consumer premises Grid edge storage has requirements which limit the technologies
Twith associated energy management systems, distributed that can be used:
generation and microgrids. The grid edge is seen as important as most • Independence of location
of the network transformation i.e., electrification, decentralisation, and • Modularity
digitalisation are taking place there, and efforts to improve resilience • Mobility
and quality of supply to customers are focused largely in this area. • Flexibility
Commerce and industry (C&I) are facing the prospect of regular • Safety
load shedding or load reduction programmes, as utilities struggle to • Long duration output capability
meet demand with ageing plant and variable renewable generation,
coupled with increasing severe weather conditions. Battery energy storage systems (BESS)
Bulk energy storage (BES) at the grid edge is finding increasing There are numerous forms of bulk electricity storage systems
application as a reliable low emissions reserve of energy, that can (ESS), but battery storage (including flow batteries) is the most
keep essential plant running through these occurrences. In addition, suitable at present to meet the requirements of grid edge
BES allows control over the cost of energy consumed, by controlling storage. The prime advantage of BESS is the ability to locate
the time-based consumption of grid energy and optimising the use of anywhere in the network, either collocated at the generation
on-site generation sources. With the likely increase in the frequency source, at a node in the transmission and distribution networks or
and intensity of extreme weather events in the coming decades, the at the point of distribution or consumption. A further advantage is
resilience of supply will be one of the most vital factors for success. modularity, which allows BESS systems to be scaled up easily to
In addition, increasing amounts of behind-the meter-variable meet requirements. Battery energy storage is decreasing in price,
renewable energy, especially such as rooftop solar PV, have created and just as PV and wind have matured to be the least-cost new
a need for the storage of large amounts of electrical energy for short energy sources in most areas of the world, energy storage is on a
periods. A few years ago, storage was considered to be too expensive similar (but faster) path of cost reduction.
to use other than as a short-term bridging medium that allowed start-up The most common form of BESS is based on Li-ion and
of the primary standby plant. The approach meant that the capabilities other lithium-based products and consists of large numbers of
of storage had not been fully explored, and developments and the relatively small batteries connected in parallel. Other products
rapidly decreasing cost of battery storage systems (BESS) have made such as vanadium flow batteries and aqueous zinc air batteries
bulk electricity storage economically and technically viable for C&I are also finding application in this sector.
consumers and have enabled more network related applications than
simple energy storage. Smart storage
Breakthroughs in related digital technologies have led to the
Bulk electricity storage creation of innovative software platforms that advance the
The name implies large storage systems that can provide an energy technical capabilities and economic viability of battery storage.
output over a longish period, hours rather than minutes or seconds. The development of comprehensive charge control/energy
Bulk storage was traditionally associated with the generation and management systems has led to the concept of “smart storage”,
transmission grid, and pumped water storage, thermal storage and where monitoring and control functions are integrated with
compressed air are all used to supplement the output of generating the storage module, allowing a wide range of storage-based
plant during peak demand periods. Storage has moved slowly down the functions to be added to the network. In addition, power quality
hierarchy to distribution networks and finally to the grid edge, behind the management features have been added, giving a comprehensive
meter, or as part of microgrids and distributed generation networks. quality and security of supply solution.

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