Great Expectations: Energy Projects Revisited

Every energy related project-be it new or retrofit-starts out with specific expectations. Proper planning dictates that those expectations be quantified and that they appear to be reasonably achievable. But as with any renovation or retrofit, the best plans and projections don't always stand up to the harsh light of reality. Put another way, when you tear down a wall or expose previously hidden ductwork, you never know what you'll find. Ventilation systems assumed to be operating at design parameters may be found not to be performing at peak efficiencies.

 Altering one aspect of s system may have an unanticipated effect elsewhere in the system. Likewise for new installations; theoretical designs that should perform adequately don't always. These are the kinds of things that make energy management challenging. With this in mind, EUN editors returned to some of the case studies that have been detailed in recent issues to see if they've met-or exceeded-expectations, what problems were encountered, and what lessons were learned. What we discovered follows.

Heat Recovery and Sustainability
at University of Ottawa
Low-maintenance, high-efficiency systems employed in new and renovated facilities

By C. C. SULLIVAN
OTTAWA-Judging by his title, Energy and Environment Engineer Pierre de Gagti6 of the University of Ottawa in Ontario, Canada, might be expected to care about efficiency and operational costs. Yet, in speaking with the leading school facility planner, it becomes clear that he has an even loftier goal: sustainability.
     As a champion of the school's recent use of heat recovery systems, he has watched this ambitious concept taken into practice. "I think this technology is a good example of sustainable development," de Gagne explains. "In addition to being highly efficient, it is simple and economic to use, and can last for generations."
RECOVERING HEAT
     The first installation of a heat-recovery loop--a 1994 retrofit to an auditorium (EUN April 1998)-cut total energy use by some 2 million kWh, slashed annual costs by $62,000, and earned the 150-year-old school a regional first- award from the American Society of Hearing, Refrigerating and Air-Conditioning Engineers (ASHRAE) for a public assembly building. Six more units have been installed over the last


At least seven facilities at the university can boast higher effeciencies and better HVAC control, thanks to the retrofits.

three years, and more are coming on line, says de Gagn6.
     “There’s another one under construction for the major renovation of Vanier Hall, which is now underway,” the energy engineer explains. “We keep putting them in  because they’re reliable, simple devices that don’t need a lot of  attention. For long-term customers, they make good economic sense.”
     One of the major benefits of the systems, says de Gagn6, is favorable life cycle costing. "If you let the architects do their usual thing, cost cutting would almost always rule out this type of system. But we're more technically savvy than most owners, and we're more attuned to recurring costs."
     Because the heat-recovery devices can be installed without adding major infrastructure, such as new piping, the first cost is reasonable. Once installed, the system maximizes a facility’s benefit from the free-cooling mode during cool weather.
     Also contributing to the fife-cycle advantage is a limited maintenance regime. The heat-recovery device specified for the university-a plate-type, air-to-air heat-recovery system by Burlington, Ontario-based Regent Eco--has no filters, motors, belts, or piping. Only one highly reliable pneumatic actuator is needed, and compression seals for the dampers experience less wear than sliding seals.
     The manufacturer recommends that the heat-recovery system be cleaned every five years, adds de Gagne.


A mechanism for modulating unit capacity is critical to the effective use of heat recovery. This partial schematic shows a basic heat-recovery installation at the university.

"We were skeptical of the low-maintenance claims, but the installations have proven themselves out very nicely. The aluminum plates have discolored a bit, but there's no real dirt developing," he says, referring to the plate-and frame package, which removes heat from exhaust air (see figure below.) 'The system is as reliable as a boiler."
ENERGY MANAGER ADVICE
     The heat-recovery scheme employed throughout the University of Ottawa can be emulated in many other facilities, and in fact, a nearby school board is specifying the system. However, energy managers should consider a few key issues:
- Climate. While heat recovery is applicable to summer operation, installations offer more "bang for the buck" in colder climates, notes Patrick Threan, vice president of Regent Eco.
- Control. "You have to allow for a mechanism to modulate the capacity of the unit," says de Gagn`e. "They're so efficient they can easily overheat a space." End-users recommend face-and-bypass dampers or just mixing with existing fresh-air capacity to modulate use.
- Payback. Depending upon hours of operation, fuel costs, and application type, an average payback period of as low as three years can be expected, says Turcan.
     Overall, de Gagrf5 sees more use of the systems at the University and at other facilities everywhere. "Often, efficiency comes with the costs of complexity. This heat recovery scheme, on the other hand, is economic to put in now, and it lasts for generations.

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