Trane Sales Webinar Central Geothermal Systems A System Overview…
Trane Sales Webinar Lee Cline P.E. Senior Principal Systems Engineer
Trane
La Crosse, WI
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Agenda
Overview
Multiple Chiller/ Heater Bi-directional Cascade
Single Chiller/Heater Configurations
Water-to-Water Heat Pump Configurations
A Few Lessons
Additional Resources
Q&A
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5
Distributed Geothermal System
heat pumps
water pumps vertical-loop ground heat exchanger (borefield)
WSHPs
Dedicated outdoor air units
Optional fluid cooler
Water pumps
Geo heat exchanger
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Central Geothermal System
• Chillers provide heating and cooling
• Ground couple for an efficiency boost
• Central air handlers
• VAV terminals
• Water pumps
• Auxiliary boilers
• Fluid or dry cooler
Air handlers
chiller/heaters
Geothermal loop (borefield)
VAV boxes
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Central Geothermal Customer Benefits Compared to Distributed
• Premium efficiency (LEED EA Credit #1) – Efficient central equipment
– Bi-directional cascading
– VAV
– Air economizing
– Better heat recovery management
• Easy to maintain
– Central equipment, few cooling units
– Uses equipment rooms, no access to occupied space required
– Simpler coil condensate collection
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Central Geothermal Customer Benefits Compared to Distributed
• Low space noise (ASA 12.60)
– Fans and compressors away from occupied space
– Noise paths can be more easily attenuated
• Good IAQ
– Many filtration options available (LEED EQ 5 – MERV 13)
– Easier to deliver 30% more outdoor air (LEED EQ 2)
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Vertical Markets
• Education
– Primary and secondary
– Colleges and universities
• Government
– Federal sector
– State and county level
• Long-term owners
– Accept extended payback periods
– Interested in embracing green technologies
– Usually have space for a borefield
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Incentives
• Utility
• Reimbursement
• Tax (if private)
www.dsireusa.org
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Central Geothermal System Types
System Type Capacity Range Target Market
Single chiller/heater
systems
(based on typical industry units)
K / 12 Schools
Simpler / Smaller
Premium Efficiency
cascading
multi-chiller/heater
systems
(based on typical industry units)
High School / Secondary Ed
> 36,000 sq. ft
Super Premium Efficiency
Water-to-water
heat pump system
(based on typical industry units)
Small Building – Large Volume
80% of Buildings < 25,000 sq ft
Premium Efficiency
150-1500 tons
70-250 tons
5-200 tons
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Agenda
• Single Chiller-Heater Central Geothermal Systems
– Four-pipe distribution system configuration
– Two-pipe distribution system configuration
• Multiple Unit Cascading Systems
• Water-to-Water Heat Pump Based Systems
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Central Geothermal Systems
Single Chiller-Heater
• Allow screw compressor chiller-heater based CGS
systems down to 70-75 tons
• Simple configurations
• Simpler operation
• Two basic distribution configurations:
– 4-pipe – simultaneous heating/cooling
– 2-pipe – changeover heating/cooling
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P-GS
4-pipe distribution / Constant flow (3-way control valves)
aux heat
cond
evap
CHR-1
Chiller/Heater
P-CH
P-HT
heating loads
cooling loads
Single Chiller-Heater CGS
to
ground
source
from
ground
source VAL-1 / VGS
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P-GS
aux heat
cond
evap
CHR-1
Chiller/Heater
VAL-1 / VGS
P-CH
P-HT
heating loads
cooling loads Standard chilled water
system maybe constant
flow, primary/secondary or
variable primary flow
Single Chiller-Heater CGS 4-pipe distribution / Constant flow (3-way control valves)
to
ground
source
from
ground
source
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P-GS
aux heat
cond
evap
CHR-1
Chiller/Heater
VAL-1 / VGS
P-CH
P-HT
heating loads
cooling loads Heating water system will
likely be constant flow or
primary/secondary
4-pipe distribution / Constant Flow (3-way control valves)
Single Chiller-Heater CGS
to
ground
source
from
ground
source
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aux heat
heating water by-pass
chilled water by-pass
VAL-1 / VGS
P-CH
P-CD
heating loads
cooling loads
cond
evap
CHR-1
Chiller/Heater
VAL-1 / VGS
P-HT
Primary/secondary
heating water system
- for expanded
distribution delta T
and variable flow
4-pipe distribution / Decoupled pumping
Single Chiller-Heater CGS
to
ground
source
from
ground
source P-GS
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aux heat
cond
evap
CHR-1
Chiller/Heater
VAL-1 / VGS
P-CH
P-HT
heating loads
cooling loads
Ground-source loop should be variable flow
for controllability and pumping efficiency
4-pipe distribution / 3-way control valves
Single Chiller-Heater CGS
to
ground
source
from
ground
source P-GS
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Central Geothermal System Options
• Auxiliary heating
– NOT OPTIONAL for single unit systems
• Auxiliary heat rejection
• Auxiliary cooling
• Contingency cooling connections
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P-GS
Contingency Cooling
Connections
aux ht reject
Central Geothermal System Options
aux heat
cooling loads
cond
evap
aux cooling
heating loads
Chiller/Heater
P-CH
P-HT
to
ground
source
from
ground
source VAL-1 / VGS
Single Chiller/Heater
Central Geothermal Systems
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2-pipe distribution / Constant Flow (3-way control valves)
Single Chiller-Heater CGS
V1
cond
evap
Chiller/
Heater
V2
auxiliary heat
V3
building loads
to
ground
source
from
ground
source
P-GS
P-DS
V4
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Single Chiller-Heater CGS 2-pipe distribution / Constant Flow (3-way control valves)
Cooling only mode
V1
cond
evap
Chiller/
Heater
V2
auxiliary heat
V3
building loads
to
ground
source
from
ground
source
P-GS
P-DS
V4
Chilled water distribution
will likely be constant flow
or primary/secondary
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Single Chiller-Heater CGS 2-pipe distribution / Constant Flow (3-way control valves)
Cooling only mode
V1
cond
evap
Chiller/
Heater
V2
auxiliary heat
V3
building loads
to
ground
source
from
ground
source
P-GS
P-DS
V4
Ground-source loop
providing cool water to the
chiller/heater condenser
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2-pipe distribution / Constant Flow (3-way control valves)
Single Chiller-Heater CGS
Heating only mode
V1
cond
evap
Chiller/
Heater
V2
auxiliary heat
V3
building loads
to
ground
source
from
ground
source
P-GS
P-DS
V4
Heating water distribution
will likely be constant flow
or primary/secondary
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Single Chiller-Heater CGS 2-pipe distribution / Constant Flow (3-way control valves)
Heating only mode
V1
cond
evap
Chiller/
Heater
V2
auxiliary heat
V3
building loads
to
ground
source
from
ground
source
P-GS
P-DS
V4
Ground-source loop
providing warm water to the
chiller/heater evaporator
Multi-Chiller/Heater Cascading
Central Geothermal Systems
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cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Central Geothermal Systems
Multi-Chiller/Heater Cascading
VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
PB
to
ground
source
from
ground
source
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Multi-Chiller/Heater Cascading Review
• Number of Chiller-Heaters
– 2-6 Units
Nominal 80-250 ton unit capacity
Actual 150-1500 ton plant size
• Operating conditions
– 38 leaving chilled water
– 140 leaving condenser water (lower is better)
– Not at the same time!
• Cascading has the potential to increase plant efficiency
• The energy transfer loops increase plant controllability
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PB
VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Multi-Chiller/Heater Cascading Introduction
to
ground
source
from
ground
source
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VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
Cooling system
cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Multi-Chiller/Heater Cascading Introduction
Standard Chilled Water
System may be:
• constant flow
• primary/secondary or
• variable primary flow
to
ground
source
from
ground
source PB
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PB
VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
Heating system
cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Multi-Chiller/Heater Cascading Introduction
Heating Water System will
likely be constant flow or
primary/secondary
to
ground
source
from
ground
source
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VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Ground-source loop
Multi-Chiller/Heater Cascading Introduction
Ground-source loop
should be variable
flow for pumping
efficiency
to
ground
source
from
ground
source PB
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VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Condenser Energy Transfer Loop
Multi-Chiller/Heater Cascading Introduction
Condenser Energy Transfer
Loop brings cooling water to
condenser from ground-source
loop or heater evaporator
to
ground
source
from
ground
source PB
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PB
VAL-3
/ VCC cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Evaporator Energy Transfer Loop
Multi-Chiller/Heater Cascading Introduction
VAL-2
/ VEC
M
M
VAL-1 / VGSC
Evaporator Energy Transfer
Loop brings warm water to
evaporator from ground-source
loop or chiller condenser
to
ground
source
from
ground
source
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PB
VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Single Chiller-Heater Operation
Multiple chiller-heater systems
can and will provide simultaneous
cooling and heating with one unit.
Multi-Chiller/Heater Cascading Introduction
to
ground
source
from
ground
source
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Central Geothermal Systems
Water To Water Heat Pump
WWHP – Simple piping - dedicated pumps
PH
Cooling load
To wellfield
Heating load
PC
From wellfield
PW
P P P P
Water-to-Water
Heat Pumps
evap
cond
evap
cond
cond
evap
On
Cool On
Cool On
Heat Off
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Key Design Issues
• Geothermal vs Heat Recovery
• Optimizing life cycle costs
– Borefield sizing
Supplemental heating
Auxiliary heat rejection
– Load shedding economizer
Application Comparison
Geothermal vs Heat Recovery
Geothermal
• Separate heating and
cooling seasons
• Relatively balanced
• Real estate for ground –
source system
• Capital availability for
ground-source system
• Energy savings driven
Heat Recovery
• Significantly cooling
dominant
• Relatively low peak or
average heating load
• “Right-sized” heat
recovery unit
• Energy and ROI driven
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optimizing life cycle costs
Ground-Source Sizing
• Must consider
– Peak building demand
– Annualized building energy balance
• Optimization
– Reduce peak demand – cooling and heating
– Balance annual heating and cooling loads
– Consider a hybrid system design
Fluid cooler
Pond / lake system
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Heating Dominate Seasonal Load Profile
Building Load Profile
0
600000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Month
Energ
y
Cooling
Heating
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Cooling Dominate Seasonal Load Profile
Building Load Profile
0
500000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Month
Energ
y
Cooling
Heating
Total vs. monthly?
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Addressing Load Profile Imbalance
• A cooling dominate building
– Reduce solar loading and/or interior loads
– Auxiliary energy rejection (e.g. fluid cooler)
– Add heat load to system (e.g. domestic hot water)
• A heating dominate building
– Auxiliary heating system (e.g. condensing boiler)
– Thermal solar heating
• Optimize the building life cycle cost
– Reducing borefield size
– Increasing borefield utilization for energy efficiency
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cooling
load
On
Cool
PLc
PC PLe
M
M M
A
cond
evap
On
Heat
M
PH
B
cond
evap
heating
load
Multi-Chiller/Heater Cascading
VAL-2
/ VEC
VAL-3
/ VCC
M
M
VAL-1 / VGSC
PB to
ground
source
from
ground
source
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Packaged Central Geothermal Plants
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A Few Lessons…
• Do not oversize the plant!
– Do a computerized load analysis – not rule of thumb
– Size for “block loading” - not “sum of the coil peaks”
• Apply optimization principles
– Pump pressure optimization
– Load based setpoint resets
• Have auxiliary / backup heat in single unit systems
• Watch the condenser minimum flow in heating
• Fully and carefully document control
system sequence of operation
– Do not leave the “details” to the controls field technician
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Additional Resources
• Applications Engineering Manual - SYS-APM009-EN
includes single and multiple chiller/heater configurations.
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