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GI Endurant, LLC
One East Oak Hill Drive, Suite 304 Westmont, IL 60559
Tel: 312-405-9489
Rob Olden
Director of Engineering
www.ginorthamerica.com
GEOTHERMAL
INTERNATIONAL
Agenda
1. Introduction
2.Overcoming oversizing
– Why detailed analysis?
3.Design case studies
– Integrating innovative HVAC and geothermal
– Optimizing importance
– Importance of commissioning
4.Construction economics
– Considerations for geothermal
Problem Statement
“ Note: Geothermal field sized in excess of connected load to accommodate for diffusion, maintaining thermal performance for unbalanced load.”
- General note on actual geothermal bid drawing • Added vertical costs • Added horizontal costs • Added coordination (including code setback review) costs • Added spoils management • Added chamber costs • Added pumping costs • Added pipe material costs • Added labor
Why do fields get oversized?
Geothermal heat exchangers behave……
…..differently from cooling towers.
Overcoming Oversizing
Cooling tower selection criteria
• Ground Conductivity • Thermal Diffusivity • BHE depth • BHE spacing • Equipment type • Equipment efficiency • Equipment arrangement • Sequence of operations • Occupancy schedule • Hydronic design • Pump selection • Outside air • Infiltration • Load diversity • Hourly loads • Annual drift
Time (1 Year)
Hour 1 Hour 8760
Geo
ther
mal
Tem
ps
• Ground Conductivity • Thermal Diffusivity • BHE depth • BHE spacing • Equipment type • Equipment efficiency • Equipment arrangement • Sequence of operations • Occupancy schedule • Hydronic design • Pump selection • Outside air • Infiltration • Load diversity • Hourly loads • Annual drift
Engineering uncertainty leads to oversizing
Overcoming Oversizing
Why Detailed Analysis?
• Projects installed to date
– 1150 Boreholes totaling 470,750 linear feet
– 2,799,481 million square feet served
– 6742 tons ( 23.7MWatts) of cooling capacity
Achieved overall average of 18%
reduction in geothermal field size
when performance spec was used
Average project “linear feet per
ton” is 70’ vs 150’-200’
0 0
1227
3053
1403
177 122 163
818
1426
319 32 21 0 0
0
500
1000
1500
2000
2500
3000
3500
Ho
urs
per
Yea
r
Supply Temperature Range
Hydronic Supply Temperature
0 0 1
2920 2737
229 103 226
1009 1081
400
48 7 0 0 0
500
1000
1500
2000
2500
3000
3500
Ho
urs
per
Yea
r
Supply Temperature Range
Hydronic Supply Temperature
$450,000 Saved
145 boreholes at 450 feet deep 115 boreholes at 450 feet deep
Why Detailed Analysis?
Why Detailed Analysis?
• To improve the economics of geothermal
• A scientific alternative to rule of thumb design that enables the following:
1. Integrating innovative HVAC systems
Generating equipment SOO
2. Optimizing performance
3. Optimizing commissioning
1. Integrating Innovative HVAC Systems
• Raising the bar to allow study of geothermal system design innovations
– Central Plant Systems
– Hybrid Cooling (cooling towers, chillers, etc)
– Hybrid Heating (boilers, solar thermal, etc)
– Industrial and process loads
– Differing geothermal sources
Cascading central-plant chiller system simulation with hybrid cooling and heating
One New Change, London
Reinforcing
Vertical
Loop
Structural Integration
Mansfield Hospital
Largest Lake Loop System in
Europe
• 1,400 tons Heating
• 1,600 tons Cooling
• 140 steel heat exchangers
• 650,000 SQFT Lake
• Completed: 2009
• Annual C02 savings: 2,029
tons
2. Optimizing Performance
• Identify the most efficient control sequences
– Minimize energy consumption
– Maintain long-term system stability
• Hypothesizing vs. guessing
• Allows future calibration and optimization based on real building data
Metered energy use tracks with simulated energy use after calibration
0.9
Walgreens Case Study
12,000 sq. ft. • Completed 2010 • Oak Park IL
Total GHVAC Cost: $370,000 ($180,000 geo premium)
ARRA Incentives: $161,245 (ITC & Depr)
4.6 year payback • 1st 20 years energy savings: $155,800
Conventional Utility Costs: $17,570 • $1.37 psf
Geothermal Utility Costs: $11,772 • $0.92 psf
Savings from Geothermal: $5,798 • $0.45 psf
Walgreens Case Study
Oak Park prototype system includes • Four geothermal boreholes • Geothermal heat pumps • Water-cooled refrigeration • Supplemental (hybrid) boilers • Supplemental (hybrid) cooling tower • Geothermal M&V
Total KJ comparison: 27,059,065 to 26,933,983 = 0.46% error
Simulation Analysis Accuracy
-
10,000
20,000
30,000
40,000
50,000
60,000
70,000
Tota
l En
ergy
(kJ
)
Date/Time
SYSTEM MEASURED SYSTEM SIMULATION
Model Calibration
Initial Simulation Calibrated Simulation
Energy Savings 52% 53%
Cost Savings 33% 31%
Real Data from Monitoring
System
Plugged into Simulation Model matches recorded
data
Supported Initial Performance Estimates
Model Calibration
Commissioning Reports
Eliminated power spike
during morning warm-up period by 50%
Reduced night-time energy use by 30%
Early detection prevented future failures and maintenance emergencies.
AFTER FIX BEFORE FIX
3. Importance of Commissioning
0.9
Central Plant Office Case Study
93,116 sq. ft. • Completed 2011 • Mundelein IL
Total GHVAC Cost: $2,620,000 ($970,000 geo premium)
ARRA Incentives: $880,828 (ITC & Depr.)
1.5 year payback • 1st 20 years energy savings: $1,600,000
Conventional Utility Costs: $114,533 • $1.23 psf
Geothermal Utility Costs: $54,976 • $0.59 psf
Savings from Geothermal: $59,557 • $0.64 psf
2xParallel DHR Chiller/Heaters serving hydronic VAV. Boiler for back up 100% Geothermal
Heating Load
TC ° F TH ° F
Cooling Load
Evapo
rator C
on
den
ser
GHEX
Cooling Tower
Chiller Plant
Geo field maintains (warms) the
evaporator to support the load on the condenser side
Geo field maintains (cools) the
condenser to support the load on the evaporator side
Central Chilled Water Plant
Heating Load
TC ° F TH ° F
Cooling Load
Evapo
rator C
on
den
ser
GHEX
Chiller Plant
M&V
Central Chilled Water Plant
0.9
1200 Ton Office Case Study
423,158 sq. ft. • Completed 2012 • Glenview IL
Total GHVAC Cost: $12,050,000 ($1,971,000 geo premium)
ARRA Incentives: $1,205,000 (Only ITC)
4.25 year payback • 1st 20 years energy savings: $4,620,500
Conventional Utility Costs: $470,394 • $1.11 psf
Geothermal Utility Costs: $298,438 • $0.70 psf
Savings from Geothermal: $171,956 • $0.41 psf
50% Geothermal HVAC Hybrid
2x Conventional RTU in parallel with 2xGeothermal Heat pump RTU Serving VAV electric reheat system. Geothermal only heats at night.
Snow melt and data centers are connected to geothermal source loop.
Campus Retrofit Case Study
166,000 sq. ft. • Countryside, IL • Completed 2011 Distributed rooftop heat pumps • Radiant heat • Central chiller/heater • Central staging pumping station • Advanced air filtration • Snowmelt • Hydronic VAV
Central Plant: “6 Pipe”
• Control to Leaving Water Set Points in Heating and in Cooling Simultaneously.
– Chilled Water Temps to 38 F
– Hot Water Temps to 140 F
– Resultant source flows are mixed and sent to the field.
Design Conclusion
1.We need to change our paradigm with geothermal design
2.Performance Specs enable innovation and increased value
3.Analysis should remain alive for comparison after commission
4.Upfront commissioning is vital
Construction Economics
1.Advanced analysis of hybrid geo enables:
DESIGNING TO THE BUDGET
OPTIMIZE PAYBACK
SENSITIVITY STUDIES
2.Understanding the costs:
– Why deeper boreholes?
– Spoils management
– Manifold chambers
– Setbacks
– Conductivity testing
Why deeper boreholes
1.Deeper boreholes are not always better
– Shallow bedrock (>150’)
– Land area is tight
– Pumping design
– Pressure testing
2.Benefits:
– Reduces horizontal costs (25% of total job)
– Less site coordination
– Better conductivity
• Schedule • Spacial constraints • Trade coordinat • Winter operation
Drill Rig Considerations
• Spoils containment • Landfill testing • Liquid spoil management
Drill Rig Considerations
• Formations may favor mud rotary
• Temporary vs permanent casing
• Test well data should be included in bid documents
Drill Rig Considerations
Spoils management
1.Site logistics
– Managing fluids on the ground
– Custom dumpsters or confined pits on site
– Other trades in close proximity
2.Testing
– MWRD
– Landfill (CCDD vs. subtitle D)
3.Questions to ask
– Can spoils be recycled on site
– Drilling experience given the logistical constraints
Manifold Chambers
Plastic Chambers
Grade Accessible
Factory assembled
No structural impacts
3.5’ below grade
No penetrations
$22,000
22 BHE’s/Chamber
Concrete Chambers
Ladder required
Assembly required on site
Concrete structure
5’-8’ below grade
Multiple penetrations
$85,000
No max limit
CAD Details
Code Requirements
• Civil site utilities can dramatically worsen geothermal payback
– Ductile iron for all storm sewer
– Backflow preventers on permeable paver systems
– Drilling under slabs
• Code is antiquated and needs to be revised to enable closed loop geothermal construction
Conductivity Testing
• Important to enact, but be careful: – Location may be non-compliant with code setbacks
– Conductivity is fairly consistent in this area • Lake Forest 52.4-52.8/1.89/1.26
• North Chicago 55/1.65/1
• Downtown Chicago 54.6-55.9/1.94/1.35
• South Chicago 54.5/1.50/1.01
• Hyde Park 55.1-56.2/1.94/1.36
– Geothermal analysis must model all of the energy flows accurately
– Why not operate with sensitivity study and require test on first production borehole to confirm
Conclusion
• Higher resolution analysis + Hybrid geothermal = smaller fields and safer operation
• Analysis + monitoring = smarter ongoing operation
• Performance specifications will reduce the variance in geothermal bids and open the market to innovation