SEPTEMBER 2014
ASHRAE JOURNAL THE MAGAZINE OF HVAC&R TECHNOLOGY AND APPLICATIONS
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Energy Performance for
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2014 ASHRAE TECHNOLOGY AWARD CASE STUDIES
FPO
The University of Calgary’s Energy Environment Experiential Learning Project is a LEED Platinum facility that generates chilled water at night to use the next day, uses cascaded heating and cooling loops to save pumping energy, and uses earth tubes to precondition air.
SECOND PLACE COMMERCIAL BUILDINGS: EDUCATIONAL FACILITIES, NEW
Learning
By Experiencing BY TIM MCGINN, P.ENG., HBDP, MEMBER ASHRAE
BUILDING AT A GLANCE
Energy Environment Experiential Learning University of Calgary Location: Calgary, Alberta, Canada Owner: University of Calgary Principal Use: Post-secondary classroom and laboratory building Includes: Classrooms, offices, teaching and research labs for biology, chemistry, earth sciences, chemical, civil, and mechanical engineering students. Employees/Occupants: 300 staff and researchers/1,200 students Gross Square Footage: 263,700 Substantial Completion/Occupancy: Sept. 2011 Occupancy: 95% National Distinctions/Awards: Architectural Institute of British Columbia 2013 Architectural Awards - Special Jury Award for Outstanding Achievement; Honor Award, Society of College and University Planning; AIA-Committee on Architecture in Education Excellence in Architecture for a New Building.
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The Energy Environment Experiential Learning (EEEL) project in Calgary, Alberta, Canada, responds to the necessity for modern, high caliber undergraduate learning environments. The facility, which opened September 2011, is studentcentric, providing opportunities for hands-on and experiential learning in both individual and collaborative settings. The 263,700 ft2 (24 500 m2), five-story building provides instructional space for expanded programs in energy and environments, new laboratories for biology and chemistry, as well as space for the ISEEE (Institute for Sustainable Energy, Environment and Economy) Administrative Center. Tim McGinn, P. Eng., is a principal at DIALOG in Calgary, Alberta, Canada.
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ABOVE Earth tube installation. LEFT Central atrium with social stair and day-
light scoop at top.
The design team’s overarching effort was to minimize EEEL’s use of energy, water and material resources wherever feasible and maximize indoor environmental quality. A secondary goal of the project was to provide every regularly occupied space within the building access to daylight.
Energy Use The modeled reduction in energy relative to an ASHRAE Standard 90.1–1999 reference building without inclusion of the university’s district energy system (DES) was 58% savings, when including the campus DES, savings were 68%. Chilled water use, hot water use, total electrical consumption and lighting electricity use data is continuously monitored (Figure 1). The actual energy use (reporting period between July 2012 and June 2013) measured 6% higher than the predicted energy results with a measured annual energy use intensity of 83.6 kBtu/ft2 versus 78.6 kBtu/ft2 (949 400 kJ/m2 versus 892 600 kJ/m2) predicted. A heating and cooling degree day analysis was completed for the data set, revealing that there were 38% more cooling degree days and 1% fewer heating degree days during the reporting period compared to the simulated weather file. The energy model does not reflect the final development of the fifth floor shelled space (originally modeled as office space) into intensive research laboratory development. It would follow that the 6% gap between actual energy use and predicted is less, and if the energy model were modified to reflect fifth floor end use, the gap would disappear with the building performing better than predicted.
Water Conservation Water use strategies are intended to allow EEEL to not only reduce its overall consumption of water resources, but most especially, minimize the use of potable water
resources wherever possible. Roof drainage is routed through cyclone trash filters and directed to an underground 28,700 gallon (108 641 L) storm water cistern. Water is delivered through a variable speed pumping system and piping network for reuse in flushing toilets and urinals. When captured rainwater volumes are insufficient to meet demand, cistern water is augmented with campus post processed river water. The university uses river water for condenser water in the central chiller plant; by regulation, the water cannot be directly returned to the river so is used a second time to augment the storm water cistern and irrigation. The use of water-efficient plumbing fixtures such as infrared controlled dual flush toilets and pint flush urinals stretches the amount of storm water available for flushing purposes. EEEL is able to reduce its potable water consumption by 64%.
HVAC Rather than a regionally typical forced-air ventilation/cooling system with perimeter baseboard heating, innovative European based low energy approaches were adopted. Ventilation and sensible cooling duties were decoupled to save cooling transport energy and allow the use of high-temperature cooling strategies. Exhaust air heat/cool recovery, displacement ventilation and radiant
Electricity (MWh)
Problems to be Solved
1,000 800 600 400 200 0
JUL AUG. SEP. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUN.
Reporting Period Measured Consumption
Simulation “Normal” Consumption
FIGURE 1: Measured versus predicted energy use.
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heating/cooling distributes fresh air and highly effective heating and cooling throughout. The base building system is designed to service classrooms, offices and laboratories from a common infrastructure, allowing the migration of building spaces over time to different uses without significant renovation costs. All spaces except a large lecture theater are served by three 40,000 cfm (18 900 L/s) dedicated outdoor air systems (DOAS) in the basement; each have an array of variable speed direct drive fans in integral acoustic enclosures and provide energy savings, redundancy, and increased space efficiency. Coils with low leakage bypasses open to reduce fan energy when the coils are inactive, and there is space for an additional 20,000 cfm (9 450 L/s) “piggyback” unit on top of each unit for the flexibility to convert more spaces to labs. Shortly after occupancy and development of a fifth floor shell space into intensive research labs, one piggyback unit was added. All air is delivered to the building at 65°F (18.3°C) through displacement ventilation techniques. The main duct network is shared and looped on each floor enhancing reliability, expandability and energy savings. The supply and exhaust duct mains are sized for eventual build out to 180,000 cfm (85 050 L/s), so the existing peak of 140,000 cfm (66 150 L/s) results in significant system pressure drop savings. The main outdoor air intake at grade feeds a 14 ft (4 m) deep ground coupled intake plenum system that acts as a preconditioner for the main units. Building exhaust is routed through filters, a glycol runaround heat recovery coil and 4 × 40,000 cfm ( 2 × 18 900 L/s) high plume, dilution exhaust units on the roof. Toilet and wet exhaust is routed up separate risers and join the main exhaust on the roof upstream of the heat recovery module. The high plume exhaust units throttle down in non-bypass mode during nighttime hours to save energy and reduce ambient noise to nearby residential areas. A fourth air handler serving a 180 seat lecture theater is supplied outdoor air from a ground coupled earth tube system. Buried 14 ft (4 m) below grade, two-150 ft (46 m) long, 48 in. (1.2 m) diameter concrete tubes precool ventilation air in summer, and preheat the air in winter. Heat recovery and heating/cooling coils supplement the earth tube system. Air is distributed to a pressurized plenum below the raked seating with low velocity air outlets in the seat risers, overhead radiant 76
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Heat Recovery to DOAS Units High Plume Roof Exhaust 5th Floor 4th Floor 3rd Floor 2nd Floor Above Grade Air Intakes
Main Floor Ground Coupled Intake Plenum
Earth Tube Geothermal Preconditioner
DOAS Unit 65°F (Typical of 3)
Basement
Theater AHU 65°F
Main Floor Theater
Heat Pipe
80°F Electrical Room
Exhaust
FIGURE 2: Ventilation systems concept.
panels provide auxiliary heating/cooling. Outdoor air quantity is demand controlled with CO2 sensors. Exhaust is passed through a heat pipe energy recovery unit and then used to cool the main electrical room (Figure 2). A central solar chimney at the top of the atrium provides passive smoke venting and natural venting of non-lab exhaust during mild weather. When the outdoor air temperature is mild, the vents open, exhaust air bypasses the central exhaust and relieves out of the atrium by stack effect. This allows the central exhaust to throttle down, saving energy. The stack pressure also improves positive airflow through operable windows in classrooms and offices. Lab windows are fixed closed to preserve lab pressure relationships. The owner’s district energy system (recovered heat from cogeneration) provides high-pressure hot water for generating hot water and 70 psi (483 kPa) steam for lab use. Distribution and utility piping has been sized for future build-out to a full lab building and currently sees reduced velocities and pressure drops. Heating consists of radiant slabs, unit heaters, and overhead radiant panel/light shelves in perimeter rooms. The higher heating temperatures for radiant panels and heaters versus the lower temperature for heating coil glycol and radiant slabs are served by a cascaded heating system; return water for each load is used as the supply water feed for the next load (Figure 3).
2014 ASHRAE TECHNOLOGY AWARD CASE STUDIES
Domestic and Process Hot Water Radiant Panels and Heaters
170°F
Glycol to AHU Coils
Campus High Temperature 400°F Hot Water From Campus Cogeneration System
140°F
Radiant Heat/Cool Slabs
190°F
Energy Reduction Strategies • Cascaded mechanical heating and cooling with high system DTs. • New campus fume hood sash height standard. • Variable speed fans and pumps. • High performance envelope with; R11 spandrel, U=0.3 triple glazing, R40 roof, R20 basement walls. • Low hot water use plumbing fixtures. • Extensive daylighting and solar control; fixed external sun shades on building elevations, atrium roof light scoop. • DOAS ventilation and decoupled sensible cooling with radiant slab and panels.
120°F
• Demand controlled ventilation.
FIGURE 3: Nested heating plant design reduces pumping power by increasing system DT.
• Low pressure drop air handling components, piping and ducting networks. • Reuse of once-used air to condition service spaces. • Earth coupled air preconditioning systems. • Heat recovery on 100% of exhaust volume. • Low energy cooling plant generates cooling water at night with cooling towers and stores for next day. Only uses campus chilled water as backup. • Natural venting of general exhaust during mild weather to reduce fan power.
Typical Lab showing interior overhead cooling/heating/acoustic/light bounce panels and perimeter heating panel/light shelf.
Calgary has an average mean daily ambient temperature range of 19°F (10°C). Cool nights are capitalized on for the design of the cooling system. Located near the end of the campus chilled water distribution system, capacity is limited and precious so a simple system was designed to generate high temperature chilled water at the building. A thermally active building system (TABS) was incorporated into the design of the facility. Cool water for the facility’s air-handling system and radiant cooling units is produced at night (when ambient temperatures are lower) by evaporative closed circuit cooling towers, freeing much needed capacity for the campus plant to service other loads. High temperature cooling water is circulated through radiant tubing embedded in the cast 78
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in place concrete structure. Most slabs are cooling-only, but in the main foyer and double height lounge spaces the slabs automatically migrate to heating as outdoor conditions get colder. Cool water produced in the cool evenings and at night is used to pre-charge the thermal mass of the building and is also stored for the next day’s use in an on-site stratified chilled water storage system. Two indirect cooling towers generate water to first pre-charge the radiant slabs with cool energy during the early evening, then charge a 160,000 gallon (606 000 L) underground stratified thermal storage tank overnight. The system generates 50°F (10°C) water from 72°F (22°C) return water temperatures. The towers are off during daytime hours. Variable speed pumps circulate chilled water to the air handling unit coils, supplemented by the campus cooling system heat exchanger only if the storage temperature is insufficient to meet supply air temperature
2014 ASHRAE TECHNOLOGY AWARD CASE STUDIES
setpoint. Dehumidification is seldom 72°F Max. Water Cooled Lab required in Calgary’s dry temperate cliEquipment and Evap. Heat Pumps mate. Cooling coil return water is cascaded Cooler to supply the radiant slab and panel loops, Overhead Radiant Evap. Cooling Panels Cooler augmented with additional flow from the Radiant Cooling Slabs storage tank when required to meet the load. The radiant panel loop also serves as a Campus Cooling Loop process condenser water network for water68°F Backup cooled lab equipment (Figure 4). Bypass to Charge Cooling 61°F Slabs Direct at Night Supply and exhaust air terminal units Stratified AHU Cooling Coils 64°F Max. Thermal serving each lab, office suite or classroom and Miscellaneous Storage Tank 50°F Min. Fan Coils are connected to the mains in the corridors. FIGURE 4: Cooling plant concept. Each lab may have fume hoods, source capture snorkels, heat capture hoods and general exhaust. During the early stages of the integrated design process, the team established a new campus fume hood standard with a lower working sash height, reducing lab peak exhaust rates by more than 20%. Hood sash alarms remind users to close sashes when not in use. Snorkels were used to replace hoods whenever feasible and lab air change rates are reduced to half when labs are unoccupied. Lab base cooling is provided by the chilled floor slab; dual circuit interior radiant panels, also designed as acoustic panels, modulate in either cooling or heating mode, Radiant tubing from manifolds ready for concrete topping. avoiding reheat coils or additional supplemental cooling airflow. The panels are also used as a light bounce surface for the indirect lighting fixtures. Base heating in perimeter the electrical energy devoted to lighting, and mechanical energy devoted to removing the heat produced from that rooms is provided by light shelf/radiant heating panels. lighting. Cooling loads in offices or classrooms are lower than The east-west orientation enhanced access to north labs, so the chilled slab and displacement ventilation is and south sun, but adjacent high buildings to the south sufficient to carry the load. The interior radiant panels of the site restricted lower floor access to daylight durfound in labs are replaced by acoustic/light bounce panels. Outdoor air rates exceed ASHRAE Standard 62.1-2010 ing winter months. The shape of the site restricted the length of the building such that the depth of the floor in all spaces by a minimum of 30% while still delivering plate was necessarily wider than is optimum for full floor exceptional energy efficiency. During occupied hours, occupancy sensors turn empty room lights off and reduce plate daylight penetration. Massing strategies provide large perimeter openings with external shading devices, air to 33% of full flow; at night, the ventilation is off. a central clerestory and light well through the center of Classroom and office exhaust is collected through the the building, and glazed corridors to the teaching spaces. atrium with some drawn through electrical rooms and A large light scoop at the top of the atrium drives light communication closets to provide secondary cooling. deep into the heart of the building (Figures 5a and b). Daylight and Solar Control The integrated design process supported by extensive Daylight harvesting in regularly occupied spaces energy and solar modeling yielded a distinctive envelope improved the quality of the indoor environment by design that minimizes peak solar loads within the buildmaking it more conducive to teaching and learning, as ing, resulting in reduced mechanical first cost by reducing well as reducing overall building energy use by lowering the cooling system capacity and complexity. In addition to 80
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A
B
FIGURE 5A (LEFT): The atrium volume allows daylight to penetrate deep into the building core. FIGURE 5B (RIGHT): Daylight penetrates through perimeter windows, atrium and double height lounges.
external shading devices on all elevations, automated interior blinds allow for the control of natural light in EEEL’s labs and classrooms. To not compromise EEEL’s daylighting strategy, the blinds are manually lowered by the instructor and designed to automatically rise at the end of each class to make sure that EEEL’s blinds are not perpetually closed and unnecessarily using artificial light.
Conclusion A high performance envelope, comprehensive solar shading/daylighting scheme and a decoupled ventilation
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and radiant cooling/heating scheme accomplished the owner’s goal of a highly sustainable building, delivering a 56 point LEED Platinum facility, four points over the 52 point threshold. The focus on improved indoor environmental quality through the use of displacement ventilation, radiant technologies, ample daylighting and acoustic controls have yielded highly productive learning, teaching and research spaces. Since its opening in 2011, EEEL has become a gathering space for campus students drawn to the central social stair in the atrium, providing a harmonious area for working, meeting friends or just hanging out.