CMX 2004 - Plumbing & HVAC

Cover Story
Ground source
heating/cooling
Passion for energy efficiency sparks
Canada’s largest geothermal project
By Simon Blake
Making the argument for energyefficient
buildings is becoming
easier in a time of ever-increasing
energy costs. But selling it to an
owner can still be difficult, particularly
where a tenant will pick up the operating
costs.
There were no such problems at the
new University of Ontario Institute of
Technology north of Oshawa, Ont.
“(University officials) have a passion
for high energy efficiency systems,”
reported Bruce Bunker, P.Eng., director
of special projects. That may be an
understatement.
The energy efficiency goal for this
80,000 sq. metre (860,000 sq. ft.) eightbuilding
facility is 30 per cent below
that required under the ASHRAE 90.1
standard. Officials are also stiving for
Leadership in Energy & Environmental
Design (LEED) Gold certification for
this facility.
That passion has resulted in the
largest geothermal heating/cooling system
in Canada and the second largest in
North America. Drilling was completed
in November.
The first university building opened
in September. Three more buildings are
scheduled to greet students next
September.
The well field
The central plant provides heating and
cooling for the facility largely through
the geothermal Borehole Thermal
Energy System. (BTES).
Bruce Bunker: “We have a passion for high energy efficiency systems.”
Construction takes place down below.
Ken Bright displays one of the chiller plants with its seven compact 90-ton centrifugal
compressors. (These Turbocor units will be on display at CMX in Toronto.)
The 128 by 64 metre geothermal well
field consists of 362 wells – 12 or 14 per
manifold – drilled to a depth of 700 feet
(213 metres). Wells are laid out on a
nine-metre grid with 12 or 14 per
manifold.
The heat transfer fluid, a 15 per
cent glycol/water mix, circulates
through over 150 kilometres of fourinch
polypropylene piping which was
pressure tested to 300 psi. The piping
can route as much as 7,000 kW of
condensing water through the geothermal
field.
Heat is absorbed from the geothermal
loop into the ground during the
summer. In the winter, the heat pumps
are reversed and heat is drawn from the
ground to provide low temperature
52°C (126°F) hydronic heating to most
of the campus.
The university may replace the glycol/water
mix with Enviro-Kool, a high
performance heat transfer fluid from
Clearwater Inc., Houston, Tex., that will
effectively increase the capacity of the
system by 20-plus per cent and is environmentally
safe, reported Ken Bright,
CET, manager special projects, for
UOIT.
Supplemental (trim) heating will
be provided by six 95 per cent-plus
efficient Viessmann Vertomat 3.5 million
Btuh condensing boilers.
Wesmech extraction fans are mounted
on top of the flues to assist in governing
exhaust stack back pressure, further
enhancing efficiency. The Vertomats
supply 82°C (180°F) heated
water for vestibules, radiant panels
and backup heat if required.
High efficiency cooling
There are two primary mechanical
rooms in the central plant, the first
houses the boiler system and geothermal
pumps, the second is home to the
chillers.
Initial cooling estimates came in at
4,400 tons, noted Bright. However,
energy efficient building design combined
with first-class equipment allowed
engineers to reduce the cooling
capacity by over 50 per cent to 2,000
tons. That can be modulated down as
low as five to nine tons, he added.
Chilled water is supplied from two
Multistack chillers, each having seven
90-ton modules. There are two sets of
geothermal heat pumps (also by Multistack)
with seven 50-ton modules each.
The chillers utilize Turbocor compressors,
the first use of these super
high efficiency units in Canada. Made
in Montreal, these extremely compact
centrifugal compressors use magnetic
bearings and spin to over 40,000 rpm.
(A detailed article appeared in the
October/November, 2002 issue of
P&HVAC and can be found in the
Contractors Resource Centre at
www.plumbingandhvac.com.)
A series of plate-type heat exchangers
with a 30 per cent glycol mixture protects
the secondary side and, thus, the
coils from freezing in winter. “This is
the approach we take with all new
buildings,” noted Bright. “Mechanical
cooling is run year round in the new
buildings,” he added.
Perhaps surprisingly – this is
Canada after all – the cooling load
actually exceeds the heating load,
noted Bunker.
Heating and cooling is controlled
based on scheduled demand and ambient
outdoor reset.
An underground service corridor
rings the geothermal field and connects
the central plant to individual mechanical
rooms in each building.
Central air handlers
The general mechanical concept for the
project consists of using central air handling
units with outside air and a return
air mixing plenum, reported Keen
Engineering’s Mike Godawa, P. Eng.
Piping and electrical conduit runs in
mechanical corridors.
Classroom buildings are equipped
with an energy recovery wheel located
just below the rooftop to preheat the
outside air with heat recovered from
exhaust air. In the case of laboratory
buildings, where air contamination is a
major concern, a run-around loop system
is used to reclaim waste heat.
14 Plumbing & HVAC Product News – March/April 2004 www.plumbingandhvac.ca