1
Geothermal Heat Pumps (GHPs)
SURE Workshop March 3, 2006
Hugh I. Henderson, Jr., P.E.CDH Energy CorpCazenovia, NYwww.cdhenergy.com
John D. Manning, P.E.Earth Sensitive Solutions, LLCAuburn, NY
2
Outline
• Basics of GHPs• How Does a GHP System Work?• GHP Equipment• Examples of Good and Bad Building
Applications• Design Considerations for GHP System• Case Studies• Economics of Geothermal Heat Pumps
4
What is it?
• Couples the building to the earth, a lake, or river– Uses “constant temperature” heat source/sink
• It’s a heat pump system that:– Rejects heat to the ground for cooling– Extracts heat from the ground for heating– Moves heat within the building
• Energy efficiency is its first attraction• Simplicity in operation and maintenance
5
It’s at Heat Pump• A Machine that transfers heat from a
lower temperature to higher temperature
• A refrigerator or air conditioner that runs “backwards”
• COP = Heat OutPower In
• Heating COPs: ~2-5
• Seasonal Avg COP: ~3
From GroundLoop (e.g. 40 F)
To Ground Loop(e.g. 35 F)
Room Air(e.g. 70 F) Supply Air
(e.g. 110 F)
Compressor movesrefrigerant from cold
zone to hot zone
Cold Side
Hot Side
Flow restrictionmaintains pressure
difference between thehot and cold zones
HotRefrigerant Gas
(e.g. 130 F)
WarmRefrigerant Liquid
(e.g. 110 F)
ColdRefrigerant Vapor
(e.g. 30 F)
6
And a Ground Heat Exchanger Vertical Bores (holes in the ground)
Bentonite fill
138 ft
15 ft spacing
6 inch dia.
Bore Field Circuiting
9
Other Types of Heat Pumps
Air-Source Heat Pump
Heat Pump Water Heater
All Heat Pumps extract low grade from a low temperature source
10
Is it Renewable?• Pulls heat from the earth (or body of water)
– Uses “seasonally” stored solar energy– 70% of energy for space heating comes from ground
• Uses “constant” ground temperature to achieve high efficiency
• Is that the right question?• Real questions:
– NET amount of energy savings– What local and power plant emission reductions result
from energy savings– What is its embodied energy content and system life
My Thesis: kWhsaved = kWhfrom renewable source
12
CO2 Emissions – lbs per Year
77
23,910
14,875
-
50,00
0 10
0,000
15
0,000
20
0,000
25
0,000
30
0,000
35
0,000
40
0,000
Light bulb
SUV
Grandma
Office Bldg 341,553
13
Source Energy & Emissions
• Source or primary energy is consumed at the power plant or in boiler
• kWh 11,000 Btu – (31% plant & transmission)
• Therm 105,000 Btu– (5% transport losses)
• Source energy good proxy for greenhouse gas emissions
15
It’s a SystemIncludes ground loop, piping, pumps, HPs, building loads
HP HP
Bores
50 hpLoop pumps,
variablespeed
Pilings
410 tonHPs
3,200 galH.W.
storage
Hot Water Recirc.
ColdWaterInlet
Water HeatingSpace ConditioningGround HX
• Can be applied to meet space heating loads, cooling loads, and water heating loads
• The normal HVAC design details matter
16
A Close CousinThe Water Loop Heat Pump System
• Many of the same “inside the building” issues
• Commonly used HVAC system
SprayPump
2-SpeedFan
InletDamper
OutletDamper
Boiler#1
Boiler#2
FluidCooler(Cooling Tower)
HP
HP
HP
HP
OutdoorAir
LoopPumps
HeatPumps
BoilerPump
BoilerPump
Boilers
Loop SupplyTemperature
17
Loop Temperatures Efficiency– Heating COPS: 3-5 – Cooling EERs: 10-20
Performance
01234567
20 30 40 50 60 70 80 90 100 110Loop Temperature
CO
P
0
5
10
15
20
25
30
EE
R
COP
EER
21
Ground Loop Loads
-400
-200
0
200
400
600
800
1,000
May-97
Jul-9
7
Sep-97
Nov-97
Jan-9
8
Mar-98
May-98
Jul-9
8
Sep-98
Nov-98
Jan-9
9
Mar-99
Gro
und
Loop
Loa
ding
(mill
ion
BTU
)
Heat RejectionHeat Absorption
23
Daily Average Temperature
J J A S O N D J F M A M J J A S O N D J F M A M1997 1998 1999
0
20
40
60
80
100Te
mpe
ratu
re (F
)
Outdoor Air
Ground Loop Supply
Ground Loop Return
02
4
6
810
Loop
Flo
w (1
e5 g
allo
ns)
26
Closed Loop Options
Point of heat exchange with heat pump
Horizontal Slinky Loop
Pond LoopHorizontal Loop
Vertical BoresLoop Piping
30
Different Types of EquipmentWater-to-Air Heat Pumps• Water Source Heat Pumps (WSHPs)
– Loop temperatures 50 to 90F • Extended Range WSHPs (geothermal)
– Loop temperatures: 25-100FWater-to-Water Heat Pumps• Water Source Heat Pumps (WWHPs)
– Loop temperatures: 25-100F– Hot Side temperatures: 100-140F
DX-to-Air Heat Pumps• “Direct Exchange” Heat Pumps (GXHPs)
31
ARI Rating Standards
• ARI 320 – Water-Source Heat Pumps – Traditional water loop HPs (ISO 13256)
• ARI 325 - Ground Water-Source Heat Pumps – Open loop systems
• ARI 330 - Ground Source Closed-Loop Heat Pumps– Closed loop systems; adds in pump power
• ARI 870 - Direct Geoexchange Heat Pumps– Currently only one manufacturer– Copper in ground eliminates one heat exchange step
33
Loop Temperatures EfficiencyHeating COPS: 3-5 Cooling EERs: 10-20
Performance
01234567
20 30 40 50 60 70 80 90 100 110Loop Temperature
CO
P
0
5
10
15
20
25
30
EE
R
COP
EER
35
What is a Good Building Application?• Should have “balanced” Heating and
Cooling Loads– Though cooling loads have more impact that
cooling loads:Qrejection = Cooling Load + HP PowerQextraction = Heating Load - HP Power in
• Modest seasonal cooling loads (200-600 full load hours)
• More energy savings from Heating than Cooling
• Buildings with “diverse” or “highly-zoned”loads
37
Ramada InnGeneva , New York
149 rooms 100,000 sq. ft.
• All-Electric GX – 294 tons space– 40 tons water
• Rooms• Restaurant• Laundry
– Variable speed loop pumping• Ground HX length of 34,000 ft in pilings and bore field
(105 bore ft / ton)
38
“Good” and “Bad” Applications
• Successful Applications (small loops)– Schools, hotels, office buildings– Diverse loads (i.e., lots of zones)– Cooling “full load hours” are modest
• Less Successful Applications (big loops)– Fast food restaurants, box box retail, heat
rejection loads, etc.– High cooling loads more seasonal heat
rejection
39
Ground Loop Loads
-400
-200
0
200
400
600
800
1,000
May-97
Jul-9
7
Sep-97
Nov-97
Jan-9
8
Mar-98
May-98
Jul-9
8
Sep-98
Nov-98
Jan-9
9
Mar-99
Gro
und
Loop
Loa
ding
(mill
ion
BTU
)
Heat RejectionHeat Absorption
40
Comparing Building Loads
Monthly Heat Rejection
-
1,000
2,000
3,000
4,000
5,000
6,000
7,000
Jan
Feb Mar AprMay Ju
n Jul
Aug Sep Oct Nov Dec
Btu
per
Squ
are
Foot
Sun Prairie OfficeMiddleton OfficeGeneva HotelJohnson City High School
Schools have Schools have a Modest a Modest Summer LoadSummer Load
43
Ground Loop Sizing Software
Name Organization and Web Site Description Platform ECA Elite Software, Bryan, TX
www.elitesoft.com Geothermal loop sizing / heat pump design tool
Windows
GCHPCalc University of Alabama, Dept. of Mechanical Engineering, Birmingham, AL bama.ua.edu/~geocool/Software.htm
Geothermal loop sizing / heat pump design tool
DOS
GLHE-PRO Oklahoma State University, Stillwater, OK www.igshpa.okstate.edu
Geothermal loop sizing / heat pump design tool
Win
GL-Source DynCorp, Overland Park, KS www.geoexchange.org/dsgntool/grldes9.htm
Excel-based Geo loop sizing tool Excel
GS2000 Caneta Research Inc., Mississauga, Ontario, Canada greenbuilding.ca/gs2k-1.htm
Sizes geothermal heat pump systems
Win
Right-Loop Wrightsoft Corp., Lexington, MA www.wrightsoft.com
Geothermal loop sizing / heat pump design tool
Win
47
Do Not Pump Up!!!City Hall VSD Pump Control Flow Rate Setpoint
1.501.701.902.102.302.502.702.903.10
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Earth Loop EWT
City Hall VSD Pump Control Delta P Setpoint
5.0
10.0
15.0
20.0
25.0
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Earth Lo o p EWT
51
Pond Loops•Tools not readily available
•Formulated pond model based on energy balance (ASHRAE Design Guide)
•Lumped
•Ice formation
•Solar Gains
•Evaporation
•Convection
•Ground Conductance
52
Simple Pond ModelPond Heat Transfer Components (MMBTU)
MonthLoop
ExtractionLoop
RejectionGround
ConductionSolar
AbsorbtionAmbient
Convection Evaporation1 -931 3 266 494 -1,278 02 -826 0 240 662 -440 03 -362 53 266 1,058 -566 04 -146 199 257 1,335 -1,006 05 -21 537 167 19,517 2,658 -5,4996 -10 354 0 32,999 -5,343 -25,8307 0 292 0 34,667 -6,330 -26,9078 0 418 0 27,465 -8,123 -24,6289 -10 650 0 20,477 -9,409 -16,93610 -84 337 37 15,361 -7,688 -12,42811 -352 37 257 4,981 -6,921 -1,99512 -667 1 266 910 -2,853 -90
TOTAL -3,408 2,881 1,754 159,923 -47,300 -114,312
53
Pond Model Results
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec3040
50
60
7080
Tem
pera
ture
(F)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0.0
0.5
1.0
1.5
2.0
Ice
Thic
knes
s (ft
)
Lumped Pond Temperature
Ice Thickness
GX Impact
GX Impact
54
Variable Flow Pumping
• Efficient pumping is key to GHPs• In some buildings: kWhpump > kWhHPs• Variable speed pumps is more than VSD
– Proper & operating two-way valves – No extra stuff– Proper pressure set point
• Design conditions happen once (if ever)• Part load conditions are all the time
55
Variable Speed Pumping
• Savings up to 90% from variable speed pumping
Ramada Hotel - Geneva, NY
- 50 100 150 200 250 300 350 400
Best Practice/Improved Variable SpeedPumping
MEASURED Variable Speed Pumping
Constant Speed Pumping
Heat Pumps
Annual Energy Use (MWh)
12% of Constant Speed
56
Hotel - Pumping System
• Three 50 Hp pumps (one at a time) on VFD
• 0.15 Hp/ton nominal
• 810 gpm total flow (5% bypass)
• 12 psi differential pressurepump control
• Field installed two- way valves on most compressors
58
Hotel - Annual Flow Distribution
Maximum observed flow rate was less than 50% of design, due to high diversity
59
Restaurant - Pumping System
• Two 5 Hp pumps (one at a time) on VFD
• 0.15 Hp/ton nominal
• 99 gpm total flow (17% bypass)
• 18 psi differential pressure pump control
• Two-way valves on 5 of 6 compressors
60
Restaurant-Pumping Performance
High differential pressure set point caused higher pump power at low flow Minimum pump power was 30% of full power at 25% full flow
61
Annual Energy Savings
Current Practice/Configuration
16,140 kWh (54%)
191,740 kWh (36%)
309,000 kWh (88%)
190,090 kWh (56%)
Best Practice 23,560 kWh (79%)
371,740 kWh (70%)
Na 301,900 kWh (88%)
Annual Savings
0%10%20%30%40%50%60%70%80%90%
100%
MichiganRestaurant
Oklahoma Retail
New York Hotel Tennessee HighSchool
Best PracticeCurrent Practice
62
Pumping - Common Themes• Variable speed pumping
– Makes up for design short comings and operating uncertainties (oversized pumps, etc)
– Typical energy reduction of 30%-50%– Best practice can achieve energy reductions approaching 90%
• Two-way valves - hard to get right– Properly commissioned valve are mandatory!– Most sites had problems with field wiring — factory installed
valves are preferred
– High school performed worst due to normally-open valves• Choice of pressure set point is crucial
– One heat pump can require an unnecessarily high set point in theentire system
– Use small booster pumps on problem HPs to allow lower system set point
63
Ventilation for a GHP a School
ZoneZoneZone
HPHP HP
OutdoorAir
HP
Ground HeatExchanger
Geothermal Heat Pump Schematic
Supply
Return
Exhaust
Heat pumps circulate hot or cold air as needed to a single zone
Ventilation air recovers heat from exhaust air, is preconditioned, and delivered to each HP
66
Local Examples• Willink Middle School
– 172,000 sq feet New Construction
• LeMoyne College Jesuit Residence– 30,000 sq feet Existing Facility
• Cayuga Community College– 60,000 sq feet Combination New/Renovation
• Auburn City Hall– 70 year old Historical Building in need of Air Conditioning
• Cambria DEP Regional Office– LEED 2.0 Gold Certified 33,000 Sq Ft Office Building *
72
• IGA in Hogansburg, NY
• All Refrigeration Equipment, Hot Water, Heating, A/C &
Snow Melting connected to Geothermal Loop Field
• (72) bores at 400’ depth located under parking lot
73
Home of James & Dolly Madison in Orange, Virginia
5 Year Renovation Project
Extremely Unobtrusive means to add Heating & AC
74
Other Examples Around US• Iowa Courthouse• Geneva, NY Hotel• Pennsylvania Office• Detroit, MI McDonalds• Tennessee & Iowa Schools• Wisconsin Schools
75
Dubuque County CourthouseDubuque, Iowa
• 38,000 sq. ft.• 100 years old • Register of
Historic Buildings• Challenge to
maintain character• Chose open well
system
76
System
• Variable speed well pump• Monoflow piping with booster
pumps
25 hp 15 hp
8 circuits
1/40 hp
BuildingCirculation
Pump
Plate FrameHeat
Exchanger
WellPump
OpenWell
StormDrain
HP
HP
HP
HP
HP
HP
BoosterPump
77
Heat Pumps• 100 console units (106 tons)• 3/4 to 4 tons• State of monoflow valves
required booster pumps• Main circulation pump and
boosters run continuously
78
Mechanical Room & Well• 94 ft well, 10 inch diameter• Cased to 76 feet• 23 ft static water level• 10 ft draw down at 400 gpm• Tower space now used for license
plate storage, boiler space for workshop
79
Monthly Electricity Cost
$-
$1,000
$2,000
$3,000
$4,000
$5,000
$6,000
$7,000N
ov-9
4D
ec-9
4Ja
n-95
Feb-
95M
ar-9
5Ap
r-95
May
-95
Jun-
95Ju
l-95
Aug-
95Se
p-95
Oct
-95
Nov
-95
Dec
-95
Jan-
96Fe
b-96
Mar
-96
Apr-
96M
ay-9
6Ju
n-96
Jul-9
6Au
g-96
Sep-
96O
ct-9
6N
ov-9
6D
ec-9
6Ja
n-97
Feb-
97M
ar-9
7Ap
r-97
May
-97
Jun-
97Ju
l-97
Aug-
97Se
p-97
Oct
-97
Nov
-97
Dec
-97
Jan-
98Fe
b-98
Mar
-98
Apr-
98M
ay-9
8Ju
n-98
Jul-9
8Au
g-98
Eliminated $4,800 gas cost
Annual Savings $10,000 (20%)
80
Dubuque County Courthouse Summary
• GSHP under constraints of historic site• Replaced boiler/tower and console heat pumps• Booster pumps• Variable speed well pump – setpoint adjustment• Increased space• Less time on maintenance• Loop temperature set point analysis• Total energy bill reduced 20% ($10,000)
81
Ramada InnGeneva , New York
149 rooms 100,000 sq. ft.
• All-Electric GX – 294 tons space– 40 tons water
• Rooms• Restaurant• Laundry
– Variable speed loop pumping• Ground HX length of 34,000 ft in pilings and bore field
(105 bore ft / ton)
82
• One enhanced grout circuit– 63.5% vs 20% solids
Ground Loop - Bore Field
Building
Lake
EnhancedGrout
Bentonite fill
138 ft
15 ft spacing
6 inch dia.
Bore Field Circuiting Bore Field Layout
83
Hotel Hotel -- Load Diversity (294 tons)Load Diversity (294 tons)
0 20 40 60 80 100 120 140 160Cooling & Heating Load (5 ton bins)
0
500
1000
1500
Hour
s
HeatingCooling
Measured from loop heat rejection and absorption – flow and temperature data
84
Hotel - GX System Overview
HP HP
Bores
50 hpLoop pumps,
variablespeed
Pilings
410 tonHPs
3,200 galH.W.
storage
Hot Water Recirc.
ColdWaterInlet
Water HeatingSpace ConditioningGround HX
• Water heating appears as four more heat pumps on system• Adjustable speed drives and two-way valves limited pump power to 11 kW
85
Water Heating• 3,200 gallons of storage
tanks (in parallel)• (4) 10 ton heat pumps
in parallel• 9% of total energy use
FourStorageTanks
3,200 gal.
Four10 tonHeat
Pumps
S1 S2 S3 W
Cold Water Inlet
Return From Building
Hot Waterto Building S4
TF
F
T
T
86-400
-300
-200
-100
0
100
200
300
400
500
600
MM
BTU
Jun Jul Au Sep Oct Nov Dec Jan Feb Mar Apr May
Hotel - Water Heating Loop Impact
w/ WH +2,000 & -1,430 MMBTU/yr
w/o WH +2,520 & -890 MMBTU/yr
Hea
t Tra
nsfe
r to
Gro
und
Water heating balanced loads and shortened loop length 20% = 20%cost reduction in loop. Water heating HPs were almost cost free!!!
87
Hotel - Summary
• Measured pump energy use; 41,000 kWh/yr (88% savings over constant speed)
• Pump energy equals only 17% of the heat pump energy consumption
• Pumping system oversized: three 50 hp pumps (design called for two 30 hp pumps)
• Variable speed control compensates for over-sized pumps and mitigates over-sizing penalty
• Integrated water heating led to 20% loop length reduction• Diversified load peaked at 35% of installed capacity
88
Water Tower SquareWilliamsport, Pennsylvania
140,000 sq ft Spec Office space
Effluent HX Invests in HP as space rents
89
Water Tower Square
Effluent/Building loop heat exchangers
1,200 ft from effluent line
Variable speed building and effluent pumps
15% lower energy cost and chiller / boiler
All data from EMS
90
McDonalds - Detroit, MI
• New Fast Food Restaurant w/ Playland, 2,711 ft2
• Geothermal HP System:– 33 tons space
conditioning– Variable speed
pumping– 12,544 ft ground loop– 190 bore ft/ton– 32 bores, 196 ft depth
91
Daily Ground Loop Heat Transfer
1998 1999 2000 2001 2002-4000
-2000
0
2000
4000
6000
8000
10000
Dai
ly H
eat T
rans
fer (
MB
tu/d
ay)
Heat Rejection to Ground Loop
Heat Extraction from Ground Loop
Mismatched Loop Loads
Cooling
Heating
92
McDonalds - Undersized LoopDaily Averages
1998 1999 2000 2001 2002-50
0
50
100
Dai
ly A
vera
ge T
empe
ratu
re (F
)
Fluid Temperature Returning from Ground HXFluid Temperature Entering Ground HXOutdoor Air TemperatureDaily Average Flow
0255075100
Dai
ly A
vera
ge F
low
(GP
M)
93
McDonalds - Summary• Significantly less turn down than at other sites, because
differential set point was kept unnecessarily high (18 psi)• Lack of diversity causes full flow to be frequently required• Variable speed pumping still saved 54% over constant
speed pumping• A more modest differential set point could have raised
savings to 79%
94
High School - Gray, TN• 161,600 ft2 Facility Renovated in 1995 • Geothermal Heat Pump System
– 48,000 ft ground loop, 120 bore ft/ton– 400 tons space conditioning HPs, 5 Tons water heating HPs– staged pumping system with two, 2-speed motors
95
School School –– Load Diversity (400 tons)Load Diversity (400 tons)
0 25 50 75 100 125 150 175 200 225 250Cooling & Heating Load (5 ton bins)
0
200
400
Hou
rs
Heating
Cooling
Load peak below 60% of capacity
97
• Several steps were taken to improve pumping performance:– Jan-June 98: Repaired valves– March 99: Flush loop, clean strainers,
add and replace valves and solenoids, install cartridge pumps TwoTwo--
way way valvevalve
RESULTS: • 175 gpm drop in loop flow
• Minimum flow rate still twice the intended 178 gpm bypass• Cartridge pumps installed on locked-out HPs allowed reduction
in differential pressure set point from 15 psi to 10 psi —allowing 1st stage pump operation!
School - Impact of Changes
98
School - Summary• Modifications reduced pumping energy from 319,000 kWh/yr
to 151,000 kWh/yr • Variable speed reduces pumping energy to 40,100 kWh/yr
(many hours below 50% full load drives savings)• With current configuration, pump energy equals 53% of HP
energy. With best practice VFD pumping would equal 14% of HP energy.
99
Ankeny Elementary SchoolAnkeny, Iowa
• 420 students 33,000 sq. ft. 41 heat pumps• 130 tons 120 bores 175 ft deep
103
Pond Loop
W WHP 2
W WHP 1
HX 1150 hp
195W ater-to-AirHeat Pumps
35 F
85 F
Pond
W AHP 1
W AHP 2
14W ater-to-W ater
Heat Pumps
Loop water temperature to pondsLoop water temperature from pondsLoop water temperature from HXLoop water temperature to building
Number of heat pumps heatingNumber of heat pumps coolingStages of WW heat pumps operating
Utility ElectricityUtility Natural Gas
Loop pump speedSupplemental HX pump statusPond bypass valve status
104
System Energy Flows–December
WAHP
ERVWWHP
Pond
Zone
Outdoor Air
BoilerSupplemental
Misc. Loads
345230
115
MMBTU
0
700780
650*420
210
630
*Based on estimated loop flow and recorded temps
10820 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50Loop Fluid Temperature (F)
050100150200250300 Site 1 - Vertical
62 MMBTU 050
100150200250 Site 2 - Vertical
20 MMBTU
0100200300400500 Site 4 - Flat Slinky
61 MMBTU
0200400600800
Hour
s Site 5 - Hybrid Slinky23 MMBTU
0100200300400500600 Site 5b - 6-pipe
0100200300400500 Site 6 - Wide Flat
73 MMBTU
0200400600800
10001200 Site 7 - 6-pipe79 MMBTU
0200400600800 Site 9 - 2-pipe
68 MMBTU
Loop Performance Comparison
109
Seasonal Ground Heat Exchanger Performance
Site #4 Loop Temperature and Heat Pump Run Time Fraction
Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q31995 1996 1997
10
20
30
40
50
60
70
80
Dai
ly A
vera
ge T
empe
ratu
re F
6 ft Ground Temp.3 ft Ground Temp.Loop Temp.
Capacity -->> -50-30-101030507090110130150170190210230250270290310330350
Loop
Cap
acity
(kB
tu/h
r)
-20 0 20 40 60 80 100Outdoor Temp oF
0.00.2
0.40.6
0.81.0
Hea
t Pum
p D
aily
RTF
Energy Use - Heatingl Loop pump 10%l Blower 15%
-
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
1 2 4 5 6 7 9
Site
kWh
Auxiliary
Blow er
Compressor
Aux. Pumps
Loop Pump
l Compressor 75%l Auxiliary heat 0-5% (radio control)
112
What’s it Going to Cost Me?(Wisconsin Experiences)
• Ground loop investment– rules of thumb: $8/ft, 150 ft/ton, 400 sq ft/ton– $3/sq ft
• Lower HVAC equipment and building costs
• Net HVAC costs: $1-3/sq ft compared VAV
113
What’s it Going to Save Me?(Wisconsin Experiences)
• Utility cost savings on order of $0.10/sq ft in Wisconsin ($45/therm, & $0.07/kWh)– probably higher with NYS rates
• Recent ASHRAE studies suggest maintenance savings– $0.05/sq ft to $0.08 /sq ft
114
Results - CostWisconsin School Energy Cost Survey 1998
918 Schools, 69.8 million sq ft, $0.622/sq ft avg.
0
50
100
150
200
250
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
Energy Cost ($/sq ft)
Num
ber
of S
choo
ls
$0.54/sq ft District w/cooling
$0.48/sq ft GX $0.59/sq ft VAV
$0.45/therm, $0.029/kWh, $7.24/kW on peak, $0.020/kWh off-peak ~ $0.07/kWh average
116
Fond du Lac Results - Energy
Site Electricity
Site Natural Gas
Source Energy
(MMBTU) (MMBTU) (MMBtu)VAV 8,650 10,063 36,013GX 9,220 0 27,660
8,353 (-23%)
GX(MWh) (MWh) (Therm)
Lights & Equip. 1,801 1,801 Space Heating 418 139 100,633 Space Cooling 210 198 Pumps 37 143 Fans 235 392 Total 2,701 2,674 100,633
VAV
117
Fond du Lac Results -Environment
VAV SO2 NOx CO2lb/MWh 8.96 6.867 1,926MWh 2,534 2,534 2,534
lb 22,705 17,401 4,880,484lb/mmBTU 0.0006 0.1 120mmBTU 10,063 10,063 10,063
lb 6 1,006 1,207,560Total lb 22,711 18,407 6,088,044
GHP SO2 NOx CO2lb/MWh 8.96 6.867 1,926MWh 2,701 2,701 2,701
lb 24,201 18,548 5,202,126
Difference lb 1,490 140 -885,9187% 1% -15%
Natural Gas
Electricity
Electricity
Electricity Source
Coal 74%
Nuclear 20%
Gas 1.5%
Hydro 4.5%
118
Evansville HS Geothermal Impact
OptionElectricity
[kWh]Demand
[kW]Natural Gas
[therms]Standard Practice 1,222,714 673 82,580
Enhanced Design 1,362,959 479 9,700
Savings (140,245) 194 72,880
Energy cost reduction = 36%Source energy reduction = 28%.
Residential – Heating Loads
• 4 Ton units 100 - 120 MMBTU• 2 Ton unit 30 MMBTU• 2/3 of heat extracted from the
ground• Units ran continuously at
temperatures below 0 F (except site 2) Blower 5%
Loop Pump 5%
Compressor 30%
Ground 60%
Residential -Source Energy Perspective
100 MMBTU
100 MMBTU
Gen 33% T&D 90% GHP 300%
Furnace 90%111 MMBTU
112 MMBTU
Input Output
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Residential Costs Look Better…But will this electric/gas cost ratio last?
GHP Savings vs. Gas Costs
$-
$200
$400
$600
$800
$1,000
$1,200
$1,400
0.00 0.50 1.00 1.50 2.00 2.50
Cost of Gas ($/therm)
Ann
ual S
pace
Hea
ting
Savi
ngs
GHP Savings vs. Oil Costs
$-
$200
$400
$600
$800
$1,000
$1,200
$1,400
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50
Cost of Oil ($/gal)
Ann
ual S
pace
Hea
ting
Savi
ngs
Electric (kWh)
Gas Use (therms)
Oil Use (gallons)
Total Costs
Space Heating Savings
Geothermal HP (COP=3) 9,769 1,270$ Gas Furmace (90%) 600 1,111 1,967$ 697$ Oil Furnace (85%) 600 846 2,025$ 755$ Notes: $0.13/kWh, $1.70/therm, $2.30/gal, Heating Load = 100 MMBtu
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Summary
• Geothermal saves costs and energy in the right applications (e.g., schools, hotels)
• Energy Savings and Emissions Reductions...so its as good as renewable
• Traditional HVAC design details mater
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Resources
American Society of Heating, Refrigerating and Air-Conditioning Engineers
404.636.8400 www.ashrae.org
Geo-Heat Center 541.885.1750 www.oit.edu/~geoheat
GeoCool Lab www.bama.ua.edu/~geocool
Geothermal Heat Pump Consortium 888.255.4436 www.ghpc.org
International Energy Agency Heat Pump Centre
www.heatpumpcentre.org
International Ground-Source Heat Pump Association
800.626.4747 www.igshpa.okstate.edu
National Ground Water Association 800.551.7379 www.ngwa.org
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