ASHRAE TECHNOLOGY AWARD CASE STUDIES 2020

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Deep Energy Retrofit Saves Energy, Lowers Emissions for University

The project began with a complete energy optimization of the demand across most campus buildings. Then, a complete reengineering of the network was performed.

BY OLIVIER MATTE, ENG., MEMBER ASHRAE

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The Université du Québec à Trois-Rivières (UQTR) has long been committed to energy efficiency. Its energy management team recognized that one of the main hurdles to additional energy savings was intrinsic to their district-heating network. These savings could only be achieved with a deep energy retrofit of the main campus. Today, following a high-performance retrofit, students and staff are proud that their university is more energy efficient and sustainable and has lowered its greenhouse gas (GHG) emissions by 53%. Located in Trois-Rivières, campus activities. Converting the Quebec, Canada, the extensive existing high-pressure, hot-water campus (1,372,367 ft2/1,380,827 ft2 heating network to a low-pressure [127 543 m2/128 330 m2] gross sur- network eliminated major heat face) welcomes 14,000 students each losses. It also presented the oppor- term. The campus originally had tunity for efficient heat recovery a loop with high- using a centralized , tak- pressure, high-temperature water. ing full advantage of Quebec’s low This central loop passed its heat hydroelectricity rates. off to local building loops through heat exchangers. These building Innovation loops were at lower pressures and With 15 complexes across the temperatures. campus, recovering and transfer- From 2010 to 2014, the university ring heat between buildings was undertook a deep retrofit, partner- both a challenge and the key to ing with an integrated design and unlocking significant energy sav- construction firm. The project was ings. Using a heat recovery heat implemented through an inno- pump was an effective strategy. vative energy performance con- However, the existing heating tract that guaranteed key project outcomes. The project began with a com- Building at a Glance plete energy optimization of the demand across most campus build- Université du Québec ings. Then, a complete reengineer- à Trois-Rivières ing of the district-heating network (UQTR) was performed. Existing satellite networks were connected Location: Trois-Rivières, Quebec, Canada to the main cooling loop, maxi- Owner: UQTR mizing heat recovery potential. Principal Use: Academic classrooms, laboratories, sports These changes took place while the complex, library and food service campus was operating normally, Gross Square Feet: 1,380,827 ft2 without significant disruption to Conditioned Square Feet: 1,372,367 ft2

Olivier Matte, Eng., is director of technical communications Substantial Completion/Occupancy: July 2014 for Ecosystem, Quebec City, QC, Canada.

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FIGURE 1 District network before the project.

High Temperature Network 265°F Low Temperature Network Network 185°F Glycol Water Network Plant Natural Gas Heat Steam Heat Steam Exchanger Generator Exchanger Generator Ventilation

Ventilation Building Building

Ventilation Cast-Iron Lab Tank Baseboard Pool Ventilation Pool Building Building

Chiller Plant Local Chiller (R-22) Gymnasium Ventilation Building Local Chiller (R-22)

network was not compatible with this TABLE 1 Energy consumption before and after the project. solution. It was a high-pressure, high- ADJUSTED REFERENCE YEAR (ACCORDING 07/15 – 06/16 PERCENT temperature hot-water network, with sup- TO COOLING/HEATING DEGREE-DAYS) PERFORMANCE YEAR REDUCTION ply at 265°F (130°C) and return at 185°F Electricity 31,663,135 kWh 26,248,178 kWh 5,414,957 kWh (85°C). To enable the use of heat pumps, Consumption (17%) 3 3 3 410 120 m engineers converted the network to a low- Natural Gas 674 087 m 263 967 m (144,918 therms) temperature system, with a supply of 180°F (238,193 therms) (93,275 therms) (61%) 2 (82°C) and return at 120°F (49°C) (s 1 and 2 2 0.31 GJ/m Site Energy 1.23 GJ/m 0.92 GJ/m 2 2 2 (27.31 kBtu/ft ) 2). This complex conversion affected the Use Intensity (108.35 kBtu/ft ) (81.04 kBtu/ft ) (25%) entire , so precise planning and construction management were paramount. Some • Ensuring the lowest possible return-water tem- of the challenges and solutions for this conversion perature to maximize usage of a new 200 ton heat included the following: recovery heat pump. To achieve this temperature, en- • Reducing the pressure and temperature of the gineers recond the network and set up as many heating heating network, while supplying enough heat to loads in series (as opposed to parallel) as possible. The match demand. High-temperature loads were elimi- reconfiguration enabled a return temperature as low as nated with the removal of steam generators (which 113°F. Four new 4 MBtu hot water (one of which were used for humidification). In their place, indepen- is a ) were installed. Along with the dent gas-fired and adiabatic humidification units were replacement of the old boilers, old chimney stacks were installed. Equalizing the pressure between the cam- also replaced, as they could not handle gas conden- pus-wide network and each building network allowed sation. for the removal of heat exchangers, which further • Maximizing heat recovery. Engineers extended reduced the supply-temperature and pump-capacity the cooling loop to maximize heat recovery potential. requirements. Satellite networks were connected to the main loop, and

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FIGURE 2 District network after the project.

180°F Low Temperature Network Chilled Water Three New Cast-Iron Boilers 120°F 2 High Temperature Loads Condensing Boiler Adiabatic Removed from District Network Independent Steam Generator

Ventilation Buildings Requiring Lower Supply Boiler Plant 3 Temperature Connected in Series

Heat Pump Ventilation Building Building

Ventilation Cast-Iron Baseboard Lab Tank Pool 1 Building Optimization and Loads Connected in Series Building Building Pool Ventilation

Chiller Plant Separate Cooling Loops Unified Gymnasium Ventilation 4 To Main Network Building

their associated air-cooled were eliminated. TABLE 2 Project’s financing. Removing the chillers allowed the conversion of many Total Project Investment $6.3 million local cooling loops from glycol to water, which improved Guaranteed Incentives $1.2 million pump and efficiency and ultimately low- Guaranteed Annual Savings $419,925 ered cooling demand. Actual Annual Savings (2015 – 2016) $444,429 Payback Period 11.6 Years Energy Efficiency All figures are expressed in Canadian dollars. Energy audits were conducted according to ASHRAE’s Level 1 and 2 audit requirements. The design and con- savings, exceeding what was contractually guaranteed struction firm then designed the highest-performing by 8% (Table 2). energy conservation measures, implemented them, and optimized them to achieve the annual guaranteed finan- Environmental Impact cial savings (Table 1). By drastically reducing natural gas consumption and using a high-efficiency heat pump running off Quebec’s Cost-Effectiveness clean electricity, the project resulted in an impressive To achieve these results, UQTR chose an outcome- 53% GHG emissions reduction (829 metric tons/year). based contracting model, in which the design and The new heat pump contains R-134s, an HFC refriger- construction firm guaranteed the project cost, finan- ant compliant with the Montreal protocol. By connecting cial incentives, annual savings, and overall campus several satellite cooling loops to the main network, three operability. The guaranteed project cost meant that the older , which used R-22, could be removed. firm had to be creative to reuse as much of the existing In wintertime, the previously performed assets, such as piping, as possible when their condition . Now, by maximizing heat recovery, the allowed. In its second year of performance follow-up, cooling tower is less necessary, which reduces water the project has generated $444,429 (CAD) in annual consumption.

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Operation and Maintenance Alterations were made to one of the campus’s main Throughout construction, the design and construction double-deck ventilation systems, allowing more fresh firm’s optimization team supported UQTR’s O&M team, air to enter the cold deck than the warm deck. High- ensuring that appropriate control strategies would occupancy classrooms are concentrated in the central maintain campus setpoints despite the major changes zones, where heat builds up, while the peripheral zones being implemented. have office spaces. The new system maintains better

The high-pressure, high-temperature hot-water classroom CO2 levels, compared to the previous sys- network was converted into a much more efficient low- tem, which admitted fresh air evenly into both cold and pressure, low-temperature hot-water network. This warm decks. Now, for example, one of the pavilion’s enabled the removal of many old, labor-intensive com- double-deck systems has fresh air intake directly on the ponents, reducing maintenance needs. cold deck. All energy production and distribution systems were Any high- to low-temperature hot-water conversion analyzed and recommissioned to ensure that they project is complex. Implementing such a project in a live worked in harmony and were easy to maintain and environment adds to the complexity. Innovative solu- operate. Over 26 ventilation systems relied on the cen- tions (such as reusing the existing piping) were applied tral heating or cooling networks, each requiring very to overcome the logistical challenges that the project specific set points. Proper management of the networks presented. required optimizing control sequences. To reduce the impact of the project on daily campus A key benefit of increased heat recovery was the man- life: agement of the cooling network. Prior to the project, the • Shutdowns were planned with all project stakehold- 900 ton chiller was too big to provide the winter cooling ers to reduce the impact on activities in the buildings. loads, making it inefficient. Furthermore, the use of the Heating systems were replaced in summer, while cool- cooling towers had to be extended to the shoulder sea- ing systems were replaced in winter. sons to provide proper cooling for the labs. Now, with a • Bypasses were installed in order to replace elements properly sized 200 ton heat recovery chiller, the cooling of the system one at a time, while keeping the system, as tower can be shut down earlier in the fall and reopened a whole, operational. later in the spring, contributing to the project’s overall • The design and construction firm’s team in- energy savings. vestigated the original systems of each building to New energy meters were also installed for each build- determine which elements could be shut off without ing, enabling more accurate management and optimiza- affecting others, and to allow the new and old sys- tion of energy consumption. tems to operate harmoniously during the transition Throughout project construction, the campus’s operat- period. ing staff was involved in reviewing the concept and the The integrated engineering and construction approach drawings, as well as selecting the equipment. They also was key for minimizing disruption. For example, designs received training about the new system’s maintenance took constructability into account. Scheduling was fine- and operation. tuned to protect daily campus activities. Project design- ers were constantly involved and were often on site Quality of Life during the construction phase and modified the designs Some measures improved the quality of life for stu- when necessary. dents and staff. For example, when the main chilled- The integrated, outcome-based approach proved water network was extended to increase heat recovery to be a versatile way of implementing infrastructure capabilities, one of the campus gymnasiums was con- upgrades, while leveraging utility sav- nected to the loop and gained air-conditioning capabil- ings. The design team had space to ity, which it did not previously have. customize decisions and design at every greatly increased its ability to maintain an adequate set stage to ensure that the project best met https://bit.ly/309ZpBE point for physical activities year-round (about 68°F in UQTR’s needs and achieved the cam- Rate this Article winter and 72°F in summer). pus’s goals.

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