Page 53 - Energize May 2022

TECHNICAL

Commercial & industrial microgrids

offer security of supply

Microgrids have long been used as both the primary power source for off-grid applications
and as a supplementary power source for grid-connected applications. Microgrids are now
finding application as secure power supplies for data centres, healthcare facilities, airports,

manufacturing and other high energy usage mission-critical applications.

BY MIKE RYCROFT, ENERGIZE

usinesses and large corporations are energy for own generation to the standby plant more attractive, and microgrid technology
becoming aware of the advantages can combine the various energy sources to great advantage.
Bof microgrids, both to increase Modern microgrids, used as power security supplies, not only supply power but interact
resilience against potential outages with building or facility energy management systems (EMS) to control loads during power
and to reduce their energy costs. This outages, interact with the grid to apply demand management controls when the grid is
segment, which has become known as the stressed, and provide auxiliary services to the grid.
commercial and industrial (C&I) microgrid
sector, has specific requirements that Unique features
distinguish it from other sectors. In general, a C&I microgrid would be far more complex than an ordinary microgrid, having
C&I microgrids are unlike other a specific mix of components to meet the total energy needs of the customer. For instance,
microgrids in that they are primarily the low-grade heat required by hospitals could be supplied as a by-product of the generation
aimed at serving the needs of businesses or co-generation process, i.e., by heating water from the heat produced by the generator, a
and corporations, rather than being feature which is not found in general microgrids. Critical C&I applications require more than
established for the benefit of the general just a continuous supply of power, the power must meet power quality targets too.
population or a specific section of the
community. Types of microgrids
3
The primary function of the C&I Microgrids can range in complexity from simple systems, consisting of solar PV with storage
microgrid is to improve the operation and controller with a grid connection, to complex systems which incorporate many different
of a specific facility, by reducing energy components and advanced controllers. With the wide variety of control systems and
expenditure and preventing losses in components available today, C&I customers can choose a microgrid system tailored to meet
revenue and/or productivity due to power their own specific requirements.
outages. A microgrid can also be used Further gains can be achieved by connecting the microgrid’s control system to a facility’s
to ‘hedge’ prices, by switching between building management system (BMS) and energy management system (EMS). Advances in
utility power and embedded generation digitisation and the prevalence of IoT make energy and building systems far more intelligent
depending on the price of electricity at the and interconnected. Integrating these systems with an advanced microgrid control system
time. 3 enables the ‘flexibility’ of distributed energy resources (DER), including non-critical
Power interruptions, either planned as controllable loads (such as electrical vehicle charging stations), to be fully exercised to
a result of inadequate generation capacity, optimise costs and reliability.
or unplanned due to plant failure or
natural disasters, are common occurrences Microgrid configurations
today. Customers whose operation is Depending on the configuration, a C&I microgrid could respond appropriately to various
wholly dependent on a reliable supply utility supply-side issues. With increasing levels of DER, a greater level of resilience is
of electricity have traditionally installed possible, and a number of different configurations are possible.
standby generators to supply all or
part of their load during such power No microgrid, backup power only
interruptions. These standby systems have If the facility has backup generators (gensets) and a UPS in place, power would not be
usually comprised internal combustion- interrupted during load shedding or other utility outage, since the UPS would supply critical
engine-driven generators, which are load power until the gensets are engaged to take over the supply of those critical circuits.
usually diesel powered. Declining costs However, should the gensets fail to start, or continue running, power to the entire facility
have made the addition of renewable would be lost as soon as the UPS battery was depleted.

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