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Circuit outdoor air reset 87 standard fixed

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Unformatted text preview: nsing boilers 82% • Good modern boiler design closely matched to demand 80% • Typical good existing boiler 70% • Typical existing oversized boiler (atmospheric cast-iron sectional) 45-70% Data from “Energy Efficient Heating” (CIBSE, 2009) For consideration: To the left of the dotted line is the energy used when the boiler load is at 50% capacity or higher. 550 500 To the right of the dotted line is the energy used when the boiler is operating at less than half of its capacity. 450 400 In this analysis, only about 8% of the annual load (and only 6% of annual fuel use) occurs to the left of the line. 350 300 250 200 150 100 50 0 1 501 1001 1501 2001 2501 3001 3501 4001 4501 5001 Typical Annual Outdoor Drybulb Temperature Variation for Toronto – CWEC HOURLY 35 Outdoor Air Drybulb Temperature (deg C) 30 OBC Cooling Design Temperature (Toronto) 25 20 15 10 5 0 -5 OBC Heating Design Temperature (Toronto) -10 -15 -20 -25 0 January 1st 1000 2000 3000 4000 5000 Hour of Year 6000 7000 8000 9000 December 31st (8760 hours per year) Annual Typical Outdoor Temperature Profile for Toronto (CWEC) 35 Outdoor Air Drybulb Temperature (deg C) 30 Cooling Design Temperature 25 20 15 10 5 0 -5 -10 Heating Design Temperature -15 -20 -25 0 1000 2000 3000 4000 5000 Hour Number 6000 7000 8000 9000 Application to Design Process? 500 flue 450 Boiler Plant 400 350 heat to loop (boiler load) heating loop demand fuel 300 Load (MBH) 250 200 150 100 50 0 1 1001 2001 3001 4001 Hour # 5001 6001 7001 8001 Pitfalls in Simulation? Misc Electrical $8,193 Space Heating $23,056 Lighting $8,287 Water Heating $12,092 HVAC Fans $7,083 Space Cooling $4,763 Use of simulation as an indicator of actual performance? Measured vs Simulated Site Energy-Use-Intensity (from a study of 70 LEED Certified Buildings) Measured Energy-UseIntensity (kbtu/ft2-yr) Simulated Energy-Use-Intensity (kbtu/ft2-yr) Consider… Building Energy Performance – Spring 2012 - Topic 19 “Integrated Design Process” • Building design is a multidisciplinary effort involving architects, engineers, and other spets. • Generally the goal of a project is to provide a building environment that is practical, pleasant, comfortable, convenient, and safe—and this must be accomplished at a reasonable cost. • Sometimes projects have additional goals (e.g. to create an impressive building; to create a “green building”). Roles of the various designers typically include the following aspects: Architect, Civil Engineer • Building shell and structure • Interior finishes/fixture selection (Arch.) • Site work, e.g. grading/drainage (Civ. Eng.) Mechanical Engineer • Heating, ventilating, air-conditioning (HVAC) • Plumbing and drainage systems • Fire suppression (e.g. sprinklers) Electrical Engineer • Lighting • Power distribution • Security and communication systems Other • Interior design; commercial kitchens; Specialties? commercial refrigeration; landscape; etc. • Although the design duties may be segregated amongst designers (i.e. architect, engineers, etc), the various building components will eventually operate as one “system”—and it is their combined performance that will determine energy use. For example… Consider space heating energy use: • Heat transmission through the building envelope (e.g. walls, windows, roofs, etc.) is largely determined by the Architect’s design. • The “efficiency” of the heating system is largely dependent on the HVAC Engineer’s design. • Their combined performance determines space heating energy use. Very simple space heating system: losses Heated Space fuel fuelfired heater = ( − ) = ( − ) = = = Design = Architect ( − ) = Design = HVAC Engineer combined impact Interactions of Design Impacts? Architect / Civil Engineer • Building Shell and Structure • Interior finishes Mechanical Engineer • HVAC Systems • DHW Equipment Electrical Engineer • Lighting Heat losses/gains thru walls, windows, roofs impact HVAC loads. Interior finishes impact light absorption and lighting power needed for adequate illumination Ventilation rates affect HVAC loads. Determines HVAC/DHW equipment efficiency. Lighting efficiency. Heat gains from lights impact HVAC loads. Decision Making During Design Consider… For a given design, energy use can (usually) be improved either by reducing the load or improving efficiency (or both). = If LOAD or EFFICIENCY then INPUT • Is there a difference between achieving energy savings by a load reduction vs efficiency improvement? Generally we have a fixed project budget, but we’d like maximize energy performance given the money available to work with. So, we need to find the most cost effective energy saving strategies… • Let’s consider a “baseline” design with: – Heater Efficiency = 80% – Walls insulated to R-10 (U = 0.55 W/m2-K) • The project team wants to assess the cost effectiveness of investing in upgrading either the wall insulation or boiler efficiency....
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