PROJECT
46
A piping diagram showing
a section of the UFH
layout in one of the villas
of the Kubili project site.
The true beauty
of the system
installed at Kubili
is the integration of
the various services
into a cohesive,
sophisticated plant
that runs efficiently
and meets all the
client’s needs.
GOING GEOTHERMAL
Aqua Earth in Randburg tackled the drilling for the
geothermal system. A total of 30 boreholes were drilled
to a depth of 100m each — meaning that a total of 3km
was drilled into this site. The pipe and fitting are joined without using any other
form of material or equipment that can leak due to
deteriorating material. For example, compression
fittings contain rubber seals that deteriorate over time
and start to leak.
Once the hole was drilled, a vertical ground heat
exchanger, in the form of a single U-Tube configuration,
was placed in the 100m borehole. This successfully
transfers between 4.4kW and 6.2kW of thermal energy
in each hole as calculated from the site readings. All the loops were pressure-tested to four bar pressure
before and after installation, to ensure the integrity of all
the pipes and joints.
When it comes to pipe sizes, the loops consist of
200m × 32mm HDPE Class 16 pipe. As there are
30 loops in total, this meant that 6km of piping was
installed in the system. Together with the header’s
200m, this adds up to a total of 6 200m of piping for
the geothermal installation.
The fusion welding technique was used to connect HDPE
pipes and HDPE pipe fittings to each other. A fusion welder
is used to heat the inside of the pipe fitting and the outside
of the pipe. Once the pipe and fitting reach the required
temperature, the pipe is inserted into the fitting. The
heated pipe and fitting fuse together before cooling down.
July 2018 Volume 24 I Number 5
Only HDPE class 16 pipes are used for fusion welding
due to the wall thickness that ensures a proper weld
with the fitting. Thinner pipes deform when heated and
inserted into the fittings.
CHALLENGES
The biggest challenge for this project was the distance to
get to site — Kubili is about five and a half hours’ drive
from Johannesburg.
In terms of setting up the geothermal field, the main
challenge was timing. Also, because the teams were only
allowed on site between 08:00 and 17:00 and not over
weekends, this extended the drilling time somewhat. Still,
the team managed to drill and equip at least one hole a day.
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