Real Estate Investor Magazine South Africa September 2013 | Page 43

COMMERCIAL
South Africa include signif icant gas f inds
in Mozambique, the shale gas potential of
South Africa and the regional availability of
liquefied natural gas (LNG). In particular, the
regional availability of LNG offers exciting
opportunities for the creation of gas supply
nodes in all of the South African coastal
metros. An adequate supply of natural gas could
be made available to realise the CHP potential
of South Africa.
A positive driver for CHP development
in South Africa is the Absa Energy project
in central Johannesburg which is the only
commercial scale CHP project supporting
an office campus. The other CHP and trigen
projects in South Africa are small scale and
support only a relatively small part of the site
load. The Absa project provides an example of
the proper implementation of the technology,
lowering the risk for projects to follow.

The Absa energy project
The Absa Campus in central Johannesburg
comprises seven buildings, providing 140 000m2
of offices and data space, with a combined load
of 14MVA. The Campus is supported by an
Energy Centre which operates in parallel with
the incoming City Power utility supply. The
Absa Energy project commenced operation in
May 2010.
The Energy Centre is equipped with 4
Jenbacher gas engines each of 3MW nominal
rating. As added security the diesel powered
emergency generators in each of the Campus

www.reimag.co.za

buildings were retained and an additional 6MW
of emergency diesel generators were installed
to supplement the gas generators under power
failure conditions. This provides an exceptional
level of security of supply with the Campus
able to be supported by the utility supply, gaspowered generation or local diesel generation.
The Energy project required the Campus to
be ring-fenced outside the City Power network
with a new utility supply point and internal
distribution. An intake substation was built to
provide a new centralised intake point. New
internal MV distribution at basement level
links all buildings.
The sleeve network linking the basements
provides routes between buildings for MV
electrica l distribution, low temperat ure
hot water distribution and chilled water
distribution. Approximately 10 0 sleeves
ranging from 200mm to 700mm diameter
were drilled between the basements of all the
Campus buildings.
The gas engines operate from 06h00 to
20h00 weekdays and Saturdays under the
control of two operator shifts. The Campus
load as seen by the utility is controlled at the
night time load demand by varying the level
of own generation. This provides a f lat load
prof ile resulting in low maximum demand
charges. The load profile is regularly monitored
and optimised to minimise operating costs.
Diesel Electric Services are responsible for
the operation of the Energy Centre for Absa.

Monitoring and optimisation is undertaken by
Single Destination Engineering.
The Energy Centre is supplied with natural
gas from the Egoli Gas piped distribution
network in central Johannesburg. The gas
supply capacity is adequate for expansion up
to 15MW of generation. Egoli Gas supplies
Johannesburg from three intake points off the
Sasol Gas network. The Absa Energy project
necessitated linking the three networks and
upgrading the overall gas distribution network
in central Johannesburg.

Campus heating and cooling
Typically one third of the input energy to a gas
engine is converted into electrical power with
the remainder dissipated via the exhaust and
engine cooling system and radiated into the
plant room. The majority of this heat is easily
captured for heating and cooling applications.
This allows the exceptional energy efficiencies
achievable with CHP projects.
Waste heat from the gas engines is captured
and d ist r ibuted to the Campus as low
temperature hot water (LTHW). The LTHW
displaces electric building and domestic
hot water heating. This free energy displaces
electrical consumption reducing the building
and Campus load. The Absa Towers West
buildings use waste heat for building heating
and domestic hot water. During the last winter
season, the buildings achieved an impressive
maximum demand reduction of 30% and a
25% reduction in electricity consumption. The

September 2013 SA Real Estate Investor

41