Page 44 - Energize May 2021

TECHNICAL

Individual distributed solar/storage
This consists of individual solar systems
attached to each residence. The size
of the solar system may vary from
residence to residence. When surplus
energy is generated, energy may be
supplied to the solar microgrid’s (SMg’s)
energy storage system, where it may
be stored in a common battery, or
energy storage system (ESS). The SMg’s
energy management system (EMS)
can determine where energy may be
supplied, and at what price.
Figure 1: Individual solar systems on each unit
Under conditions of low solar, the ESS
may deliver power to the SMg. Under grid
failure conditions the ESS supplements the
PV production of each unit; and at night,
supplies the essential loads of each unit.
Requirements, i.e., load control to some
extent, would be the same as a home
EMS. The ESS could also be charged from
the grid depending on the state of charge
of the ESS and the cost of electricity.
A variation may include home storage
systems (HSS) as well as the communal
storage system, in which case the HSS
Figure 2: Communal solar ESS
may supply to the SMg.
Communal solar/ESS
The system is similar to free standing
dwellings but with a communal PV/
ESS, the equipment is not attached to
the dwellings. The same EMS controls
apply but there is communal ownership
of the system, which may also be
owned and operated by an onsite IPP.
Solar PV, storage and controller are
located together and connected to the
distribution system.
In sectional title units which consist of
blocks of duplex apartments or stacked
simplex units, the roof structure is owned
Figure 3: Distributed solar on communal property.
or controlled by the body corporate, and
this provides the opportunity to distribute
solar PV over the complex without using directly to the grid feeder. A variation places all loads on the AC bus, and non-essential loads
ground space. This is particularly useful are separated at the apartment through a load shedding switch. Advanced systems may have
where blocks are close together and several levels of load shedding.
interconnections are easy.
The close proximity of the building Ownership and management
rooftops allows a DC bus to be used Ownership and management of the system could take several forms.
between the PV systems and the ESS, • Community owned systems: In the most basic form, the system is owned and operated by
with a number of possibilities for the AC the residents through a corporate structure such as a body corporate. Under this system
system. In the first option, the DC bus is the cost of the system may be included in the purchase price of the unit or may form part
fed by the PV and the incoming mains, of a monthly levy. The SMg becomes part of the communal property of the scheme.
and the inverter supplies the essential load • Onsite supplier (IPP): In this scheme, the system is installed, owned and operated by an
feed. Non-essential loads are connected external company, which sells electricity to either the body corporate or to individual units.

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