AN INNOVATIVE DEDICATED OUTDOOR AIR APPLICATION FOR A GOVERNMENT OFFICE TOWER MICHAEL HALLENBECK, PE, CEM Southland Industries
BRAC 133 OVERVIEW PROJECT OVERVIEW FAN POWERED INDUCTION UNIT CENTRAL UTILITY PLANT DEDICATED OUTDOOR AIR SYSTEM ENERGY RECOVERY DESIGN CONSIDERATIONS ENERGY MODEL 2
BRAC 133 OVERVIEW BRAC 133 office towers. 2005 Base Realignment and Closure (BRAC) Act recommendation #133. Consolidate multiple DOD groups into a one campus located in Alexandria, VA. 1,700,000 sq. ft. total GSF Two Towers (20 Floors) Multiple Outbuildings 3
BRAC 133 OVERVIEW Achieved LEED NCv2.2 Gold 43 Credits Total EA Credit 1.5-24.5% Savings over ASHRAE 90.1 EA Credit 3 Enhanced Commissioning EA Credit 4 - Enhanced Refrigerant Management EQ Credit 1 Outdoor Air Delivery EQ Credit 2 Increased Ventilation DE Credit 1.3 30% Water Use Reduction 4
BRAC 133 OVERVIEW PROJECT OVERVIEW FAN POWERED INDUCTION UNIT CENTRAL UTILITY PLANT DEDICATED OUTDOOR AIR SYSTEM ENERGY RECOVERY DESIGN CONSIDERATIONS ENERGY MODEL 5
FPIU OVERVIEW 6
FPIU OVERVIEW Excellent humidity, temperature, and ventilation control. Reduced architectural footprint. Integration with other DOAS technology Flexibility during tenant fit out. Typical FPIU Installations. 7
BRAC 133 OVERVIEW PROJECT OVERVIEW FAN POWERED INDUCTION UNIT CENTRAL UTILITY PLANT DEDICATED OUTDOOR AIR SYSTEM ENERGY RECOVERY DESIGN CONSIDERATIONS ENERGY MODEL 8
CENTRAL UTILITY PLANT 42 F Chilled Water Plant (2) 1,250 ton centrifugal VFD chillers BRAC 133 42 F Centrifugal chillers. 42 F CHWS /58 F CHWR 0.380 kw/ton NPLV Provides CHW to DOAS and high latent load zone FCU s. Provided with head pressure control. 9
CENTRAL UTILITY PLANT 55 F Chilled Water Plant (2) 1,250 tons VFD centrifugal chillers BRAC 133 55 F centrifugal chiller. 55 F CHWS/65 F CHWR 0.288 kw/ton NPLV. Provides CHW to FPIU s, data and electrical rooms Provided with head pressure control. 10
CENTRAL UTILITY PLANT Mission Critical Chilled Water Plant BRAC 133 air cooled scroll mission critical chillers. 4 Chillers Total 900 Tons total Provides emergency CHW to Data, IT and Electrical Rooms CRAH s provided with Dual Coils 11
CENTRAL UTILITY PLANT Heating Hot Water Boilers BRAC 133 heating hot water boilers. (6) 8,000 MBH Input 180 F HWS / 140 F HWR 85% efficient Dual Fuel (gas/ #2 Fuel oil) 12
CENTRAL UTILITY PLANT (8) Cooling Towers 4 F approach VFD control (5) CW pumps VFD (soft-start/stop) BRAC 133 cooling tower yard. (1) Free Cooling Heat Exchanger Plate and Frame 3 F design approach 13
CENTRAL UTILITY PLANT Water Side Economizer BRAC 133 free cooling plate and frame heat exchanger. Plate and Frame Series configuration to pre-cool chilled water return. CWS < 52F : total free cooling 52F < CWS < 65F: partial free cooling 14
CENTRAL UTILITY PLANT BRAC 133 chilled water system overall process flow diagram. 15
CENTRAL UTILITY PLANT 6,000 FULL COOLING WATER-SIDE ECONOMIZER AVAILABILITY 5,000 4,000 HOURS 3,000 2,000 1,000 42F SYSTEM 55F SYSTEM 0 16
BRAC 133 OVERVIEW PROJECT OVERVIEW FAN POWERED INDUCTION UNIT CENTRAL UTILITY PLANT DEDICATED OUTDOOR AIR SYSTEM ENERGY RECOVERY DESIGN CONSIDERATIONS ENERGY MODEL 17
DEDICATED OA SYSTEM OA is dehumidified, cooled, and heated through the DOAS. Total of four Dedicated Outdoor Air Units provided. Roof mounted DOAS unit serving the BRAC 133 West Tower. OA is distributed to terminal units through a medium pressure distribution system. 18
DEDICATED OA SYSTEM Supplied with 42 F chilled water and heating hot water plant. Indoor DOAS unit serving the BRAC 133 East Tower. Cooled and heated to 48 F leaving air temperature. Building maintained below 55 F dew point. 19
DEDICATED OA SYSTEM Below 48 F ambient, the 42 F chilled water plant can be de-energized. BRAC 133 DOAS OSA intake. High latent load zones served via the 42 F system are provided with additional OA. 20
DEDICATED OA SYSTEM Q l =0.68 scfm/person w gr Q l =latent load/person (Btu/hr) w gr =humidity ratio difference (gr/lbm) where: Room design condition: 75F, 50% RH, W=64.9gr/lbm Q l = 200 Btu hr (per person) W for 55F SA DPT, 64.6 Gr/lbm Resulting scfm/person, 980 scfm W for 48F SA DPT, 49.69 Gr/lbm Resulting scfm/person, ~20 scfm, used for design 21
DEDICATED OA SYSTEM DOAS Analysis Results Tower People Occupancy: 17,000 (nondiversified) Building OA Requirement: 340,000 cfm (non-diversified) DOAS Size (4 total): 85,000/unit Average OA rate: 0.22 cfm/s.f. 22
DEDICATED OA SYSTEM What happens if they load the building unevenly with open plan cubicles? (1,284,000 sf)/ (64 sf person) 4 DOAS 20cfm/person 100,000 cfm per DOAS unit Total DOAS capability of 400,000 cfm to allow for the flexible loading of the office tower and podium. 23
DEDICATED OA SYSTEM Though the use of extensive DCV, the design team expects the DOAS to operate at diversified OA flow of 230,000 cfm when fully occupied. 55 F and 42 F chilled water systems optimally sized for the expected occupant load of 6,400 people in the tower plus the podium occupant load. 24
DEDICATED OA SYSTEM BRAC 133 DOAS airflow trend. 25
BRAC 133 OVERVIEW PROJECT OVERVIEW FAN POWERED INDUCTION UNIT CENTRAL UTILITY PLANT DEDICATED OUTDOOR AIR SYSTEM ENERGY RECOVERY DESIGN CONSIDERATIONS ENERGY MODEL 26
ENERGY RECOVERY Total Energy Recovery (Sensible + Latent) 12 ft. diameter ERU wheel 4A media Sized to match general exhaust system. Two ERU s - one 35,000 cfm unit per tower. Enthalpy Wheel 27
BRAC 133 OVERVIEW PROJECT OVERVIEW FAN POWERED INDUCTION UNIT CENTRAL UTILITY PLANT DEDICATED OUTDOOR AIR SYSTEM ENERGY RECOVERY DESIGN CONSIDERATIONS ENERGY MODEL CONCLUSION 28
DESIGN CONSIDERATIONS When providing 48 F OA to the building, the cool air reduces the 55 F chilled water system load. When DCV is implemented, the zone and building wide 55 F chilled water plant load may increase due to the reduction of OA. The zone level cooling coils and 55 F chilled water plant should be sized accordingly. 29
BRAC 133 OVERVIEW PROJECT OVERVIEW FAN POWERED INDUCTION UNIT CENTRAL UTILITY PLANT DEDICATED OUTDOOR AIR SYSTEM ENERGY RECOVERY DESIGN CONSIDERATIONS ENERGY MODEL 30
ENERGY MODEL ASHRAE 90.1-2004 Baseline Model Water Cooled Centrifugal - (2) equally sized chillers. Hydronic Heating - (2) equally sized boilers. Variable Air Volume with Re-heat Constant Volume Single Zone with DX cooling and gas heating 31
ENERGY MODEL Proposed Model Energy Conservation Measures Demand Control Ventilation Water Side Economizer Energy Recovery Unit High Efficiency Chillers High Efficiency Lighting 32
ENERGY MODEL BRAC 133 EPACT 2005 PROPOSED BASELINE ENERGY CONSUMPTION Heating - Gas 49.9% Savings 48.6% Process - Gas 2.8% Fans - Electricity 12.7% Cooling - Electricity 17.9% Heating - Electricity Heat Rejection 0.8% - Electricity Lighting 1.5% - Electricity Pumps 10.1% - Electricity 2.7% Process - Gas 2.8% Cooling - Electricity 6.0% Fans - Heating Electricity - Gas 13.5% 18.7% Lighting - Electricity Pumps - Electricity 6.7% 3.2% Heating - Electricity 0.3% Heat Rejection - Electricity 1.7% 33
ENERGY MODEL BRAC 133 LEED PROPOSED BASELINE ENERGY COST Annual Gas Cost 13.9% Annual Savings 24.7% Annual Gas Cost 5.7% Annual Electricity Cost 69.6% 86.1% 34
CONCLUSION Utilization of a Dedicated Outdoor Air system in conjunction with a multiple chilled water plants and a Fan Powered Induction Unit system can provide an energy efficient, flexible HVAC system for a modern office tower. The FPIU system should be considered along with other DOAS terminal unit technology when selecting a building HVAC system. 35
Thank You Question? Michael Hallenbeck, PE, CEM mhallenbeck@southlandind.com 36