CONTRIBUTORS
INCORPORATING COLD CHAIN
hence potential ROI. One would need to
consider how much the investment will
reduce your annual:
a. energy usage/consumption bill
b. maximum demand bill
c. (diesel) generator (DG) fuel and
maintenance costs
d. other losses directly linked to load
shedding/grid failures such as
production loss, scrap, rework, etc.
It is important to understand your business
and what the split between critical and
non-critical loads are and what the power
(kVA/kW peak and average) and energy
(kWh) requirements are for the critical loads.
The power requirement will determine
your inverter size and the energy BESS
capacity. The BESS is usually the most
expensive sub-system and could be tradedoff
against you existing back-up generator
OPEX cost and/or CAPX and OPEX for
installing a new or additional DG(s).
INCORPORATING SOLAR WITH
CONVENTIONAL ELECTRICITY
SUPPLY
Solar systems can be incorporated with
existing electricity supply system with minor
changes to the existing AC distribution
board(s), connections and reticulation
– depending on the current set-up and
intended installation, and of course in
accordance with national and local
regulations.
SOLAR POWER COMPARED TO
CONVENTIONAL AND OTHER
ALTERNATE SOLUTIONS
Even with the expected electricity tariff
increases, solar electricity at this point in
time remains a high CAPEX investment
and careful consideration of expected
break-even period and potential ROI
remains important.
The initial CAPEX cost of a PV system is
much larger than that of a DG or gas
generator, but there is definitively a
break-even point where after the PV will
pay for itself. A PV system has very little
OPEX whereas a DG/gas generator has
large OPEX in terms of fuel consumption,
maintenance as well as major overhauls
or repairs.
Depending on the type of cold
storage technology, a refrigerated
coolant reservoir can also act as energy
storage system.
Wind generation is an attractive
addition and could potentially generate
power 24/7 and not only when the suns
shines, but most regions in South Africa
do not have adequate constant wind
conditions for wind generators, while
the local climate is said to be a perfect
setting for solar power with long days
and lots of sunshine for generation.
KEY ELEMENTS SYSTEM DESIGNERS
SHOULD KEEP IN MIND
In addition to those already mentioned,
roof space, roof weight loading
capacity, roof
orientation and/
or carports or land
area for erecting
the PV arrays and
potential shading
are all important
considerations.
Many factors
influence the
expected yield
from a rooftop
solar system, but
for an example for
estimation purposes
a north-facing 30
degree rooftop with
100m² under solar
panels in an area with good annual
sunshine – the result could provide an
average year-round generation of about
75kWh per day.
It is also very important to decide
if your design is based on a once-off
installation or a phased implementation
approach – expanding capacity later.
This will determine the inverter selection
and system design as well as initial AC
connection and AC DB/reticulation
changes to ensure you can expand later
and avoid unnecessary duplicate costs.
There are also tax benefits and
potential carbon tax reductions to add
into the cost/benefit analysis when
considering solar power as a green
alternative.
SOLAR AND CARBON FOOTPRINT
In terms of total carbon footprint, solar
energy has of course a zero carbon
footprint in generation. However, keep
in mind that all the equipment and
material required for the system are
mined, processed, manufactured,
and transported – so, a complete solar
Above: Graph showing installed PV capacity trend for
SA 2019.
Right: International PV Levelised Cost of Energy
(LCOE) cost trends where the same trend applies to
South Africa.
IRENA
system doesn’t have a zero carbon
footprint.
It is estimated that nett-zero emissions
can be achieved within 4 years of the
plant or system installation.
TECHNOLOGY DEVELOPMENTS IN
RECENT YEARS
In addition to the continued
development in the electronics industry,
both inverters and solar panels have
moved towards higher DC voltages
of 1 000V to 1 500Vdc per PV string to
reduce system losses, improve efficiency
and reduce balance of plant cost.
Even hybrid inverters are moving to
high voltage battery DC bus voltages to
match the PV DC input side to reduce
inverter cost and battery cable costs.
Solar cell material and efficiencies,
as well as module (panel) construction
are also steadily improving with
mono-crystalline panels topping a
20% efficient under standard test
conditions (STC). Bi-facial panels are
also becoming popular for solar plant/
carport installations.
CLA
IRENA
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www.coldlinkafrica.co.za COLD LINK AFRICA • October 2020