Geothermal VRF for Ball Chatham
School District
Presented By: Matthew Slager PE, CGD, LEED® AP
2016 IL Renewable Energy Conference
7/21/16
Ball-Chatham C.U.S.D. #5
Schools
Glenwood High School (GHS)
Enrollment
1,426
Glenwood Middle School (GMS)
713
Glenwood Intermediate School (GIS)
737
Ball Elementary School (BES)
524
Chatham Elementary School (CES)
593
Glenwood Elementary School (GES)
668
K-12 Total
+ 626 full and part time staff
4,661
$35M Multiphase Project
• Growing Enrollment
• HVAC Systems in Need of Replacement
• Substandard Comfort (Two Pipe Systems)
• Substandard Indoor Air Quality (Unit Ventilators)
• Insufficient Outside Air Intake
• Poor Filtration
• Intakes Near Ground
• Grass, Pollen
• Insects, Rodents
Ball Elementary School
•
56,000 SF HVAC Reno
•
5,100 SF Addition
Phase I
Glenwood Intermediate School
•
10,500 SF Addition
•
Entry, Office, Commons
Phase I
Phase I Concept
• Air Source VRF
• Dedicated Outdoor Air Units
• Hybrid air source heat pump w/ gas heat
• Energy Recovery Wheel
How Air Source VRF Works
Refrigerant Pipe
Branch
Selector
Boxes
FCU’s
Cooling
Heat Pump/ Heat
Recovery Unit(s)
Cooling
Heating
Heating
Fan Coil Examples
Many types available to mix and
match to fit application
Glenwood Elementary School
•
Original building:
–
Built in 2011
–
74,000 SF
–
Unitary loop heat pumps
in classrooms
•
Additions:
–
20,000 SF total in 3 separate additions
–
14 Classrooms
–
Built in 2014
–
Geothermal Variable Refrigerant Flow (VRF) system
Phase I
Geothermal Heat Pump Basics
4 to 5 units of energy
to the building
Energy
How Geothermal VRF Works
Refrigerant Pipe
Branch
Selector
Boxes
FCU’s
Pump(s)
Heat Pump/ Heat
Recovery Unit(s)
Ground Heat Exchanger
Cooling
Cooling
Heating
Heating
Ground Loop Temperature vs.
Ambient Temperature
120
100
Temperature oF
80
60
40
20
0
-20
• Ambient Air
• Ground Loop Water
Geothermal VRF vs. Air Source VRF
• Compressor Maintenance is Indoors
• No Defrost Cycle
• Higher Heating Capacity
• Lower Refrigerant Volume
• Less refrigerant in condensing unit decreases total about 25%
• Easier to break into smaller systems where needed
• No Substantial Loss Of Capacity when OA Temp < Design
• Better Suited for Northern Climates
• Lower Energy Use
• Lower Electric Demand
Geothermal VRF vs. Unitary GSHP
• System Diversity Accounted For At Heat Pump, Not Just Ground
Heat Exchanger
• Fewer Installed Compressor Tons
• Potential For Less Peak Water Flow
• Lower Peak Load For Morning Warm Up
• Centralized Compressor Maintenance and Noise
• Less $ Premium for Individual Room Control
• Less $ Premium for Central DDC Controls
• Higher Seasonal Efficiency Means Less Bore Feet Needed to Meet
Cooling Load
Glenwood Intermediate School
•
31,000 SF HVAC Reno
•
Classroom Wing
•
Completed during
summer break
Phase II
Glenwood Middle School
•
18,975 SF HVAC Reno
•
Science Wing
•
Completed during
summer break
Phase II
Glenwood High School
•
25,700 SF Addition
•
18 Classrooms
•
Tier II Data Center (10 kW)
Phase III
Phase II / Phase III Concept
• Geothermal VRF
• Dedicated Outdoor Air Units
• Hybrid air source heat pump w/ gas heat
• Energy Recovery Wheel
What Does Geo VRF System Look Like?
• Geothermal Field
near building
• Space heating /
cooling through
FCUs in the room
• DOAS units
provide ventilation
to each space
Space Components
• Centrally placed fan coil
• Individual room thermostat
• Supply and Exhaust Air
• No equipment in closets or
build-outs
• No above ceiling equipment
requiring maintenance
Typical Ductless Fan Coil Unit
Mechanical Room Components
• Heat Recovery Units
• Refrigerant Piping
• Geothermal Piping
• Geothermal Pumps
• Expansion Tank
• Controls Interface
Concentrated Footprint
7 Ton System
12 Ton System
Reduced Space Requirements
7 Ton Ductwork
28 Tons of Refrigerant Pipes
Directional Boring
• Avoid site disturbance and reduce
restoration expense
Lower Cost Headers: Curbstop Valves
Purging Connections
• Purging required for proper
field performance
• Access for any future
troubleshooting
Design for Low Maintenance
• Minimize Ferrous Materials
• Copper or Plastic Piping
• Brass or stainless steel pumps
• Plastic lined expansion tanks (made for radiant
floor systems) or domestic HW expansion tank
• Minimize air entrapment w/ microbubble
air/dirt separator
• Use “oversized” expansion tanks
• Pre-charge water side pressure higher than initial
airside pressure to allow for leakage/evaporation
• Can eliminate permanent glycol fill system
System Benefits vs. AS & GSHP
• All compressors located in mechanical rooms
• Reduced classroom noise
• ECM pumps in mechanical rooms
• Easily monitored and controlled
• All geothermal piping in mechanical
rooms for centralized maintenance
System Energy Efficiency
• Refrigerant vs. Water
• Heat Recovery Units
• Energy Recovery Wheel in DOAS
• Low Fan Power
• High Efficiency Pumps
Site Energy End Use
Code Compliant Primary School: Climate Zone 5A
Heating (gas)
39%
Cooling (elec)
7%
Fans (elec)
11%
Domestic Hot Water
(gas)
2%
Exterior Lighting (elec)
1%
Interior Lighting (elec)
19%
Interior Equipment
(elect)
19%
Interior Equipment (gas)
2%
Fan Power – Typical 2 Ton Unit
700
Code Limitation
600
Watts
500
400
300
Geo WSHP
200
100
Geo VRF
0
Note: The code limitation value was calculated using a formula listed in the ASHRAE Standard
90.1-2010: Energy Standard for Buildings Except Low-Rise Residential Buildings.
Pump Power Ratings
25
195
22.5
180
165
F-Bad
20
17.5
135
15
120
105
D-Poor
12.5
90
10
75
C-Mediocre
7.5
60
B-Good
40
45
30
34
37
22
5
A-Excellent
15
0
2.5
0
GES
GIS
GMS
GHS
Installed Pump Power
(hp/100 tons)
Power into Pump Motor
(W/ton)
150
Minimizing Pump Power
• Low Pressure Drop (<40 ft)
• Driven by field arrangement and
header sizing
• Reverse Return to eliminate
Balancing Valves
• 2.5 GPM/Ton
• ECM Wet Rotor Pumps
Normalized Energy Cost ($/SF/Yr)
$1.20
Natural Gas
Electric
$1.00
35%
32%
$0.80
$0.60
$0.40
$0.20
$0.00
Geo. VRF
Code Min.
Geo. VRF
Code Min
GIS Energy Model Takeaway
•
•
Geo VRF Electricity for Heating/Cooling
•
27% by DOAS ASHP
•
73% by Geo VRF
•
Despite DOAS being 40% of the installed tons
Air Source VRF Used More Energy Than Geothermal VRF
•
60% More for Space Heating/Cooling & Pumping
•
27% More HVAC Energy
•
14% More Total Building Energy
•
9% More Total Building Electric Demand
•
$0.08 /SF/Yr Total Utility Cost Difference
First Cost
•
Inherent Diversity Lowers nominal equipment tonnage
•
Smaller Ground Heat Exchanger
•
Smaller Pipe
•
Higher Seasonal Efficiency, Less Ground Heat Exchanger
to Meet Cooling Load
•
Higher Heating Capacity Means Less Equipment Tons than
Air Cooled VRF
•
Major Power Using Equipment Centralized to Mechanical
Room, Lowering Electrical Cost
•
Ductless FCU do not require Balancing
•
Cost vs. Air Cooled VRF is estimated at $2 /sf higher
HVAC Cost ($/SF)
$40.00
$35.00
$30.00
$25.00
$20.00
$15.00
$10.00
$5.00
$0.00
BES
Renovation
BES
Addition
Air Source
GIS
Addition
GES
Addition
GIS
Renovation
GMS
Renovation
Ground Source
GHS
Addition
Grants
• Identified grants and assisted district with
energy modeling and grant application
• $304k total
RECC/IMEA
AIEC/ICECF
ICECF
• GIS $62k
• GMS $50k
• GIS $90k
• GMS $12k
• GHS $90k
• Grants covered entire cost Δ of air source and geo VRF
Summary
• Geothermal vs. VRF
• Geothermal VRV is more affordable than most think
• Grants can offset first cost ∆ from air source
• Other Benefits:
• Maintenance is centralized in interior mechanical rooms
• More efficient cooling & heating
• Low fan power
• Low pump power
• Full capacity at extreme temperatures
• Lower refrigerant volumes
• Longer equipment lives
Matt Slager, PE, CGD, LEED AP
Chief Mechanical Engineer
[email protected]
(217) 747-9443