Page 43 - Energize May 2021

TECHNICAL

Microgrids at residential complexes

improve power security and

reduce costs

by Mike Rycroft, Now Media

The need for secure power and the desire to reduce electricity costs has led many people to install solar
PV/battery hybrid (PVH) systems at their residences. Individual hybrid solar systems can be expensive and
inefficient, and this has led to the development of community solar systems, where property owners jointly

own and operate PVH systems.

he arrival of Covid-19 and the or gated communities which could easily install microgrid-based community PVH with great
consequent lockdown programmes advantage.
Thave resulted in many people In effect, a community microgrid combines the advantages and resilience of the current
working from home, increasing the grid system with the flexibility and individual-centred nature of small-scale, distributed
requirement for security of supply and renewable generation – plus all the smart, digital communications technology which is
reduced cost of electricity. It is anticipated available today.
that a large percentage of these people
will continue working from home after Residential microgrids
lockdowns cease, and this, combined with The community solar concept has evolved to take advantage of developments in the field of
the local phenomenon of load shedding, microgrids, and residential microgrids are becoming popular, with a number of companies
makes security of supply a primary providing standardised solutions tailored to the community residential market. These allow the
concern the business community. use of microgrid facilities by residential community PV systems.
Because of the common load characteristics, the microgrid can be considered to be
Why microgrids similar to a smart home energy management system consisting of a combination of solar PV,
In a linked community, either storage, and essential and non-essential loads, and the load, generation, and energy storage
neighbourhood, residential complex or of the microgrid could be controlled in the same manner as a smart home.
block of apartments, individual hybrid In South Africa, many linked communities exist in the form of residential estates
systems are inefficient and costly. Each with freestanding houses, sectional title duplexes or simplexes and other arrangements.
off-grid home will need redundant solar Although individually metered, (or prepaid metered) all units are fed from a common grid
and battery capacity to make it possible connection point.
for them to meet their maximum demand. Residential complexes are characterised by a large number of relatively small similar
This capacity will by design sit idle for the loads, with similar demand patterns, and similar maximum demand levels. This simplifies the
majority of the time, making off-grid home microgrid energy management system and reduces the complexity of the system. Design of
energy systems larger and much more the solar PV system is simplified and can consist of many similar modular units.
expensive than grid-connected ones. Sharing the components allows the system to serve a community’s peak demand, which
Where a common grid connection point is likely to be lower than the sum of the individual peaks and spread over a wider time frame.
can be established, it makes economic In addition, the peak storage requirements will be lower, although the aggregate storage
sense to employ a community PVH requirement will be the same.
system, where the PV, storage, inverter and Furthermore, there is generally only one inverter or inverter cluster involved and a single
microgrid control system are community grid connection. The use of communal systems also allows a higher degree of control, in
owned and controlled. Technological the form of power or energy management systems, which one would not find on individual
developments have made community residential hybrid systems. Microgrids take several forms, depending on the siting of the solar
PVH systems more feasible, and there are panels, the metering system used and the type of buildings (apartment block or duplex or free
a large number of residential complexes standing, etc.).

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