By using cold water from Lake
Ontario, Toronto’s Deep Lake
Water Cooling Project is capable
of cooling 20 million
square feet of office space (100 high
rise towers). The project, which began
operating late last year, is expected to
reduce annual carbon dioxide emissions
by 40,000 tons and energy use by
up to 75% less than conventional electric
chillers. (An article on this project
appeared in ES&E’s September 2003
issue. Visit www.esemag.com)
There is an additional benefit to this
project. Spent water from the cooling
phase is passed through a cold-energy
transfer loop back into one of the city’s
filtration plants to produce cooler
potable drinking water.
Initially, cold water is drawn through
three parallel, 600 mm HDPE intake
pipes from a depth of 85 metres, 5.6
kilometres south of the city, out in Lake
Ontario. These pipes are buried where
water depth does not exceed 10 metres,
in order to protect them from damage
from large wave and current loads, as
well as marine traffic and anchors.
Where water depth is greater than
10 metres, the pipe is laid on the lake
bottom. Screens are provided at the
intake to prevent fish and other organisms
from entering.
Water is passed through a heat
exchanger at a temperature of 4.7
degrees Celsius and exits at a temperature
of 12.5 degrees Celsius, traveling
through the city’s municipal water distribution
system. Return water enters
the exchanger at a temperature of 13.1
degrees Celsius and, by adding more
cold, fresh lake water, the temperature
is brought down to 5.0 degrees
Celsius. From here, it is pumped
through 1200 mm diameter pipes to an
underground facility in the downtown
core. From this underground chamber,
it will be further chilled to 3.3 degrees
Celsius and distributed to office and
residential towers for air-conditioning
circuits.
Corrosion protection tape products
must withstand such cold temperatures
and still be flexible enough to be
applied to metal pipes and fittings
while in operation. The tape must also
show all the attributes of petrolatum
tapes and provide long-term corrosion
protection and sealing. Products
selected for this massive and innovative
project were Denso LT tape, Paste
and Mastic.
The application involved assembling
1200 mm flanged joints, which
connected two steel pipe sections complete
with a valve assembly. The sections
were built on their ends, off site.
When assembled they stood about
eight feet tall. The application of
Denso Paste went around the nut and
bolt assemblies and the pipe sections
along with a large amount of Profiling
Mastic to fill the many voids. Irregular
configurations on this section highlighted
the tape’s conformability.
Once completed, the concrete lined
assemblies, now weighing several tons,
had to be moved by crane onto a truck
and then transported to the job site 60
km away. Once on site, the assemblies
were lowered about 80 ft below the
road surface down to a tunnel, which
had been bored using a huge vertical
drilling machine. The tunnel runs from
Lake Ontario, where the large diameter
water pipes were then connected with
the assemblies to the piping that runs
underneath the city. Once the large
diameter piping was protected and
connected, the small diameter feeder
pipes and valves that connect to various
office buildings were protected
with the Denso Petrolatum System.
