Green Economy Journal Issue 58

Battery energy
storage powered
by renewable energy
is the future, and it
is feasible in South
Africa right now!
Sodium-sulphur batteries (NAS ® Batteries),
produced by NGK Insulators Ltd., and
distributed by BASF, with almost 5 GWh
of installed capacity worldwide, is the
perfect choice for large-capacity stationary
energy storage.
A key characteristic of NAS ® Batteries is the
long discharge duration (+6 hours), which
makes the technology ideal for daily cycling
to convert intermittent power from renewable
energy into stable on-demand electricity.
NAS ® Battery is a containerised solution,
with a design life of 7.300 equivalent cycles
or 20 years, backed with an operations and
maintenance contract, factory warranties, and
performance guarantees.
Superior safety, function and performance are
made possible by decades of data monitoring
from multiple operational installations across
the world. NAS ® Battery track record is
unmatched by any other manufacturer.
Provide for your energy needs from renewable
energy coupled with a NAS ® Battery.
PREPARING THE WAY
for a solar PV plant
Gqeberha in the Eastern Cape will see construction starting on an exciting new
solar energy plant later this year and SRK Consulting, South Africa is among
the technical partners working to make this project a reality.
BY SRK CONSULTING
According to Brent Cock, principal engineering geologist
at SRK’s Gqeberha office, the company has conducted a
geotechnical investigation of the site where the 50MW
photovoltaic plant will be located. The project is on a 100-hectare
site on the western outskirts of Gqeberha between Bridgemeade
and Greenbushes. An interpretive geotechnical report has been
prepared and submitted to the co-developers, RAW Renewables and
Natura Energy.
“In a project like this, it is important to test the subsurface
geotechnical and geological conditions, including the suitability
of on-site material for engineering layer works,” says Cock. “We
were also asked to investigate the excavatability of the site, as
well as groundwater and seepage conditions.” The study checked
for any problematic soils and looked at foundation conditions
to make appropriate recommendations for the project’s design
and construction.
“We excavated 24 test pits across the site with a 30-ton tracked
excavator, to depths ranging from 0.9 metres (m) to 3.9m below
current ground level – so that we could expose and analyse the ground
profile,” he says. “We also undertook dynamic probe super heavy
(DPSH) tests to assess the in-situ consistency, which showed refusal
occurring at depths of 1m to 2.4m.”
Wenner vertical electric sounding (VES) tests were conducted at
17 locations, with two perpendicular soundings at each of the
selected positions sharing the same centre position. “Samples of
disturbed soil were collected from representative soil horizons and
tested by an SRK-approved soil testing laboratory. This gives us insight
into aspects such as the particle size distribution, including clay content
where it occurs, as well as moisture content, thermal resistivity and
aggressiveness towards buried concrete and steel,” Cock explains.
The presence of ferruginisation in the terrace gravels – where the
gravel particles have either been stained/coated, zones within the
layer indurated (hardened) by iron oxide or a combination of both –
indicates that there are sections of the site where water perched on
the underlying bedrock in the past. A 2:1 paste of soil and distilled
ENERGY
Brent Cock, SRK
Consulting, South Africa.
water was tested according to the Basson Method to determine
whether the ground is aggressive towards buried concrete and
corrosive towards steel,” he says.
Attention was paid to the presence of reworked residual clayey
silt, residual shale and shale bedrock as these are not considered
suitable construction material. “Disturbing these horizons is not
recommended as recompacting the material is difficult, particularly
if wet,” Cock adds.
The site was deemed to be underlain by competent founding
material, typically medium-dense sand and gravel with occasional
very stiff clayey silt. “Both piled and concrete plinth foundations
will be suitable for the support of the PV panels.” He added that
where materials of variable consistency are present on a site, it is
often economical to pre-drill percussion holes to the required depth
– to provide both bearing and uplift – and then backfill the holes with
suitable soil, after which piles can be driven into them.
The Parsons Power Park project is aimed at the commercial and industrial
market and will produce competitively-priced electricity for sale to large
power users connected to the Nelson Mandela Bay municipal grid.
SRK excavated 24 test pits across the site to assess the ground profile.
Contact us right away for a complimentary
pre-feasibility modelling exercise to find
out how a NAS ® Battery solution can
address your energy challenges!
info@altum.energy
www.altum.energy
Altum Energy:
BASF NAS ® Battery Storage Business
Development Partner – Southern Africa
(Left) The depth to bedrock, albeit variable, is typically shallow across the site. (Right) The thickness of the gravel material is variable across the site with thicker
zones considered preferred borrow areas.
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