Through Heat Recovery
OTTAWA-After installation of a plate- air-to-air heat recovery system cut energy costs and maintenance time in an auditorium in 1994, the University of Ottawa here installed six more units over the last three years to reduce total energy use by about 2 million kilowatt hours (kwh) and provide annual savings of about $62,000.
The installations were made during upgrades and new construction projects at five different campus buildings, with the latest being completed in August of last year.
In the initial project, an 8,000 cubic feet per minute (cfm) heat recovery system from Regent Eco, Hamilton, Ontario, was installed in the university's 256-seat DeCelles Auditorium in February 1994. The auditorium's existing air handling system was four years old at the time, but was not very energy efficient, according to Pierre de Gagne, the school's energy and environment engineer.
The Regent system features a package of aluminum plates that take heat from outgoing exhaust air. The only moving part of the unit is a damper that periodically switches the airstreams to alternate aluminum packages. Air quality is maximized because the units are able to provide 100 percent fresh air.
Half of the $45,000 cost of this first project was subsidized by the Ontario Ministry of Environment and Energy, Toronto. Annual energy savings gained from the reduction in heating are estimated at $8,000, giving that project a payback of 2.8 years with the incentive.
Tests done by the university in the months following the installation found that the unit maintained a heat recovery rate of over 85 percent during cold temperatures. The rate
| Initial success with heat recovery at a campus auditorium inspired University of Ottawa energy managers to expand its use. |
was over 90
percent, peaking
at over 92 percent during moderate temperatures.
The
recovery rate was so high that it caused de Gagne to develop a way to
control the unit and make sure it did not provide too much warm air. The
solution involved cracking open the fresh air dampers to dilute the
heated air.
"We
essentially bypassed the cassettes so we don't preheat all of the fresh
air that's coming in," de Gagne said.
The
university has added more units each time it completed a new
construction or renovation of a building.
In the
fall of 1995, a 20,000 cfm rooftop unit was retrofitted with a Regent
Eco system to improve air quality in the 100 Thomas Moore building, a
four-story classroom and office building.
The
project cost a little over $65,000, which was paid for by the school. It
is expected to yield savings of $19,000 per year, providing a payback of
3.4 years.
The building had featured an air handling unit that was
not supplying the minimum 50 percent fresh air that was needed, and did
not have much capacity to heat fresh air. Instead of upgrading the unit,
the school opted for another heat exchanger.
Around the same time, two units of 10,000 cfm and 3,000 cfm were added to the school's Marion Building, which features the campus's largest auditorium at 400 seats. The units replaced an air handling system that was nearly three decades old. The installation, which is expected to save another $17,000, was part of the building's improvement project. Exact figures for the installation were not available, but based on de Gagne's prediction of a three- payback, the installation cost was about $50,000.
The most recent installation, compeleted in August 1997, was the addition of a 3,000 cfm unit to the McDonald Building, a 150-seat auditorium. Like the Marion Building, The unit replaced a system that was old and not performing well. Annual saving of about $5,000 are expected.
For more information please contact:
bkm Engineered Interiors
Energy & Environmental Group
1-860-528-9981