EA - Pre-Conditioned Air

Innovation
Preconditioned Air (PCA) Systems:
Preconditioned Air (PCA) systems provide for cooling of the aircraft cabin while parked at the
gate, and can offer PBB cooling. Alternatives for providing PCA include mobile ground based
units, Central Plant systems (with or without thermal storage), and Point of Use (POU) Systems.
Central plant systems typically are the most efficient over the facility life cycle, and providing
thermal storage can significantly reduce chiller size and energy consumption, although they have
a higher capital cost and greater interior space requirements. Central plant systems distribute a
glycol water solution to air handling units mounted directly on each PBB. POU systems utilize
self-contained direct expansion (DX) refrigeration package units that also mount directly to the
PBB. POU systems typically have the lowest initial capital costs, but highest long term
operation and maintenance costs. Mobile PCA units are typically only used at remote parking
positions, or on a temporary basis in the event of an equipment failure at gate.

The Central PCA design provides an opportunity to significantly lower energy use and operating
costs. Since PCA is considered “process equipment” and not part of the comfort cooling HVAC
for the building, it is exempt from the Energy Compliance defined in the Florida Energy Code and
ASHRAE 90.1-2010. We highly recommend that the base building design team consider
submitting exceptional calculations for the energy savings between a Central PCA system and a
Point-of-Use (POU) system under the LEED V4, Energy and Atmosphere or Innovation credits.
This should be explored because the PCA will be coupled with the CEP, and if it is not pursued
as an Energy Conservation Measure (ECM), it would otherwise dilute the total building energy
savings. The expected energy use is half of the POU annually, which will comprise a healthy
portion of the total building energy consumption.
This system arrangement has (2) key ECM’s;
1. Using 42⁰F CHWS for 1st stage of cooling. This lowers the EWT into the PCA chillers
from 60⁰F to 44⁰F.
2. Using 56⁰F CWR for the PCA Chiller Condenser Water Source.
System Descriptions for Exceptional Calculations;
1.4.2 - ASHRAE 90.1 Section 6: HVAC (Air-Side)
Include units for all relevant inputs
Model Input Parameter / Energy Efficiency Measure Baseline Case Proposed Case
Primary HVAC Type1 PC Air Unit PC Air Unit
Unitary Cooling Capacity Ranges3 25-90 Tons 25-90 Tons
Unitary Cooling Efficiency4 2.5 KW/Ton 0.75 KW/Ton
Unitary Heating Capacity Ranges5 same as proposed TBD
Fan System Operation VFD VFD
Outdoor Air Design Min Ventilation7 100% OA 100% OA
HVAC Air-side Economizer Cycle Y Y
Economizer High-Limit Shutoff 40 DEG F 40 DEG F
3 | P a g e
1.4.3 - ASHRAE 90.1 Appendix G: HVAC (Water-side)
Include units for all relevant inputs
Model Input Parameter / Energy Efficiency Measure Baseline Case Proposed Case
The Project Has District Heating (Y/N) N N
The Project Has District Cooling (Y/N) N Y
District Cooling Plant Efficiency
-
CHILLER KW/TON +
PUMPS KW/TON +
COOLING TOWER
KW/TON
ESTIMATED = 0.9
KW/TON
District Cooling Plant PCA Capacity - 600 TONS
PCA Plant - Number of Chillers - 3
PCA Chiller Part-Load Controls1 - VFD
PCA Chiller Capacity (Per Chiller) - 300 TONS
PCA Chiller Efficiency2 - 0.58 KW/TON
PCA Glycol Water Loop Supply Temperature - 20 DEG F
PCA Glycol Water (CHW) Loop Delta-T - 40 DEG F
PCA GS Loop Temp Reset Parameters
TBD. EXAMPLE:
OAT<40 DEG F, GST
= 28 DEG F.
PCA Glycol Loop Configuration3
VARIABLE PRIMARY
Number of Primary CHW Pumps 3
Primary CHW Pump Power 75 HP
Primary CHW Pump Flow 324 GPM
Primary CHW Pump Speed Control VFD
Condenser Water Leaving Temperature 66 DEG F
Condenser Water (CW) Loop Delta-T 10
CW Loop Temp Reset Parameters -
Number of CW Pumps 3
CW Pump Power 25 HP
CW Pump Flow 922
CW Pump Speed Control CV
PEAK DESIGN DAY LOAD PROFILE