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CONSTRUCTION WORLD
SEPTEMBER
2016
ALTERNATIVE POWER SOLUTIONS
“We are currently testing an even
higher cement replacement formu-
lation and hope to achieve the
desired strength test results soon,”
explained Kevin Foster, project manager for
Khobab Wind Farm. Situated in the Hantam
Municipality, 60 km north of Loeriesfontein
in the Northern Cape, Khobab Wind Farm is
currently employing over 100 local workers on
site. All 61 foundations are due for comple-
tion by mid December 2016.
Khobab Wind Farm is utilising extremely
low quantities of Portland cement in the
concrete formulation of its wind turbine
foundations. “This revolutionary formula has
been tested in the adjacent wind farm and we
are confident to continue to use it in our foun-
dations. The insights gained have allowed us
to continue to test lower levels of Portland
cement,” says Foster.
Environmentally friendly bases
The bases use a unique design comprising
35 kg of high grade Portland cement per
cubic metre, almost 90% less than a standard
concrete mix. This composition means that
the wind farm’s carbon footprint is reduced to
approximately 90,7 kg of carbon dioxide per
cubic metre. Ground Granulated Corex Slag
(GGCS), a by-product from the iron industry, is
used to replace 89% of the cement.
“Cement manufacturing is typically a high
energy intensive process; so by substituting
the cement with a by-product the carbon
footprint has been considerably lowered,”
continued Foster.
A 28 day compressive strength test was
completed when the formulation was originally
tested; it indicated that the 89% replacement
ratio achieved an impressive strength of
55 MPa (megapascals), and an expected
ultimate strength of 100 MPa, within a 56 day
period. “The strength of concrete is measured
in megapascals; theoretically a cubic metre of
concrete that is rated 30 MPa, is able to with-
stand the weight of six bull elephants, whereas
these foundations are able to withstand
the approximate mass of 20 bull elephants
standing on a square centimetre of concrete – a
phenomenal feat,” demonstrates Cyril Attwell,
Murray & Roberts Construction, group concrete
& research manager.
A carbon footprint is defined as the total
amount of greenhouse gases produced to
directly and indirectly support human activ-
ities, expressed in equivalent tons of carbon
dioxide (CO
2
). “The achieved reduction in our
carbon footprint is phenomenal, especially
considering that a standard 30 MPa concrete as
supplied by the ready-mix industry equates to
a carbon footprint of approximately 300 kgs to
350 kgs of CO
2
per cubic metre,” added Foster.
Traditionally, 30 MPa concrete requires
between 300 kg and 350 kg of ordinary
KHOBABWIND FARM
strives for
INDUSTRY FIRST
Khobab Wind Farm has announced the completion of its first
foundation pour on 30 June 2016. The foundations are designed
using an 89% replacement of cement, one of the world’s lowest
carbon wind farm foundation footprints, making use of the
same formulation that its sister farm, Loeriesfontein Wind Farm,
successfully used in the completion of its foundations.
>
cement per cubic metre. But now scientists
working for Murray & Roberts have developed
a technology that meets the 30 MPa standard
using just 25 kg of cement or even less. Not
only does it meet the standard, it far exceeds
it. To date strengths of up to 52 MPa have
been achieved on other sites using Murray &
Roberts’ patented ARC (Advanced Recrys-
tallisation) technology and 0 kg of Portland
cement per cubic metre.
The wind farm capability
Khobab Wind Farm will comprise 61
wind turbines each with an output of
140 MW and will generate approximately
563 500 MWh/year of clean, renewable energy
to the national grid. The wind farm will avoid
approximately 550 000 tonnes of carbon emis-
sions each year when compared to traditional
fossil fuel power plants and generate enough
to power around 120 000 average South
African households.
The site, which spans a total of 3 200
hectares, was chosen for its excellent wind
resource, favourable construction conditions
and straightforward electrical connection
into Eskom’s Helios substation. The wind
turbines will be supplied by world-leading
manufacturer Siemens Wind Power, with the
blades, hubs and nacelles that compose them
arriving from overseas at a nearby port and
being transported by road to Loeriesfontein.
The majority of the 99 m turbine towers are
to be manufactured by GRI, in Atlantis, in the
Western Cape. Civil and electrical works are to
be completed by a consortium comprised of
Murray and Roberts Construction and Consol-
idated Power Projects.
The Khobab Wind Farm is part of the South
African Government’s Round 3 Renewable
Energy Independent Power Producer Procure-
ment Programme (REIPPP) is expected to be
operational by December 2017.
Khobab Wind Farm is owned by a consortium dedicated to providing clean,
renewable energy to the people of South Africa:
• Lekela Power: Lekela Power is a pan-African renewable energy platform,
which has in excess of 1 300 MW of wind and solar power projects in
its portfolio. It is a 60:40 joint venture between Actis, the global pan-
emerging market private equity firm, and Mainstream Renewable Power,
the global wind and solar company.
• Khobab Community Trust: Established by the project company with the
objective of carrying out public benefit activities to benefit the local
community in the areas of enterprise development, education and health.
• Thebe Investment Corporation; one of South Africa’s most established
broad based BEE Investment management companies and leading
investor in the Energy & Resources sector (advised by Bridge Capital).
• The IDEAS Managed Fund, is managed by Old Mutual Alternative
Investments, a subsidiary of Old Mutual Investment Group one of Africa’s
largest independent investment managers.
• Futuregrowth Asset Management, a pathfinder in fixed interest and
developmental investing.
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