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

3

Basics of Geothermal Systems

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

7

..or a Pond Loop Heat Exchanger

8

..or an Open Loop System

ReturnSupply

Well

Casing

Outflow

Inflow

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

11

Global Warming & CO2 EmissionsForecasted Impacts

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

14

How Does a GHP System Work?

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

18

Heating Mode (winter)

19

Cooling mode (summer)Cooling mode (summer)

20

Its Heat ExchangeBetween Building and Ground

50 F

38 F

50 F

44 F

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

22

“Ground Temperature is Constant Year-round”…until you reject and extract heat into it

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)

24

GHPs Reduce Electric Demand

25

Ground Loop Heat Exchangers

26

Closed Loop Options

Point of heat exchange with heat pump

Horizontal Slinky Loop

Pond LoopHorizontal Loop

Vertical BoresLoop Piping

27

VERTICALCLOSEDGROUNDLOOP

28

Open Loop Options

ReturnSupply

Well

Casing

Outflow

Inflow

Standing-Column Well

Open Loop Well

29

GHP Equipment

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

32

Different Rating Conditions for the Same Units

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

34

Examples of Good and Bad Building Applications

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

36

Schools!Fond du Lac, Wisconsin

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

41

Break

42

Design Considerations for GHP Systems

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

44

45

46

GCHPCalc

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

48

What’s wrong with this picture?

49

KISS - Keep it Simple

50

Polyethylene PipeU-Bend

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

57

Hotel - Pumping Power Variation

Minimum pumping power observed was 5% of full speed operation

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

64

Use Energy Recovery to Mitigate Heating LoadsHeat fresh air with exhaust air

65

GHP Case Study Examples

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 *

67

Mechanical Room at Willink

Installation at LeMoyne College

69

Drilling Test Hole atCayuga Community College

70

Memorial City HallAuburn, NY

A View fromthe Bell Tower

71

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

96

School - Locked-out Heat Pumps

Location of locked-out heat pumps shown in red

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

100

Load Diversity – Status Data

101

Fond du Lac, Wisconsin

102

Pond Loop Heat Exchanger

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

105

Residential Applications(circa 1995)

Ground Heat Exchangers• Two slinky varieties• Short trenches 100 ft

Ground Heat Exchangers

• One flat• Two standard 6-pipe• One 2-pipe

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)

111

GHP Economics and Environmental Impacts

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

115

Fond du Lac High School

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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

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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%

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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

121

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

122

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

123

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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Questions