modeled office building
Post on 23-Feb-2016
38 Views
Preview:
DESCRIPTION
TRANSCRIPT
VRF Applications in PNW
RTF RTUG MeetingOctober 26, 2011
Kevin CampbellReid Hart, PE Technical Research Group
Modeled Office Building
Basic Qualities Simulation Runs1. RTU, no economizer2. RTU, with Economizer and
fan control3. VRF, Heat Pump, no
Economizer4. VRF, Heat Recovery no
Economizer
2
Floors 2
Floor Area 25,000sq ft
Ventilation Rate 15cfm/person
Lighting Density 1.2watts/sq ft
Equipment Density 1.0watts/sq ft
3
System ParametersRTU VRF
System RTU VRFSEER/EER SEER 13Cooling COP 3.99 3.96Heat AFUE (gas) 80.6% - Heating COP (HP) - 4.06Supply Fan Eff. (total) 36% 60%Supply Fan total SP 2.00 1.00DOAC total SP - 2.25DOAC Fan Eff. (total) - 53%
4
Impact of VRF on HVAC Energy
• Fans have significant savings! (even more if no RTU fan control)• Heating savings in northern climates (switch gas to Electric)• Cooling savings except PNW where OSA economizer wins• Both cooling and heating benefit from variable compressor
5
Small Office ComparisonTwo Models in PNW
• Duct leakage: ES high; PECI none• Separate ventilation fan: PECI 2.5”’; ES ?• ES: refrigerant piping loss factor; PECI none
6
PNW Office Energy End Use Comparison
*PECI small office utilizes economizer and fan controls. Energy Solutions small office includes duct leakage.
Differences AreNot SuprisingA simple fan VSD measure had a wide range of savings when load variation was considered.
Differences indicate need for:• Regional standard buildings• Range of loads to capture variation• Expected value savings or other process to generate
population values
7
Modeled Medical Clinic
Basic Qualities Simulation Runs1. VAV (dX) Electric Reheat +
Economizer + SAT reset2. VRF Heat Pump 3. VRF Heat Recovery
Building • Patient rooms with variable
occupancy• More perimeter zones• Diagnostic equipment room
8
Floors 1
Floor Area 20,000sq ft
Ventilation Rate 20cfm/person
Lighting Density 1.2watts/sq ft
Equipment Density 1.0watts/sq ft
9
Impact of VRF on HVAC Energy
• Fans have significant savings! • Heating always savings since no reheat with VRF• Cooling savings due to improved part load efficiencies and
high cooling requirements of VAV reheat
10
Healthcare/Medium Office (VAV) Compare Two Models in PNW
11
PNW Office VRF Energy Use per SF
*PECI VAV with electric reheat and SAT reset. Energy Solutions VAV with electric reheat.
12
Other Heat Recovery Options:Domestic Hot Water
VRF Water Heater• Standard to 115°F • Booster to 160°FApplicable for buildings with both:• Heat rejection (server; equipment; kitchen; cooling)• Hot Water Load (Restaurants, Dorms, Hotel, Medical)Efficiency Improvement• VRF water heating percentage savings vs. gas
Water Heat Mode % Site Btu’s % MW/NE CostHeat Pump 80% 8%
Heat Recovery 93% 69%
13
Exhaust Air Heat RecoveryAdapt the old run- around or loop heat pump concept• In heat mode, cool
exhaust air• In cool mode, heat
exhaust air• Feed general loop or
pre conditioning at DOAC
• Need to verify airside pressure tradeoffs
• This strategy not in models
14
Conclusions• Modeling tools and load/system assumptions have
significant impact on predicted savings• VRF systems can provide significant HVAC savings
with lower fan energy and better part load efficiencies• Buildings with low heating loads in economizer friendly
climates have less significant savings• Exhaust and DHW heat recovery applicableNotes:• Proper control set-up & commissioning is important, as
simulations are based on perfect control operation• Simulations are not monitored results
15
Questions?
Contact:Kevin CampbellPECIkcampbell@peci.org503-575-4169
top related