Ground Source Heat Pumps: Systems and Applications 10 February 2011(c) Gary Phetteplace, GWA Research, LLCSlide 1 Gary Phetteplace, PhD, PE GWA Research

Ground Source Heat Pumps: Systems and Applications

Ground Source Heat Pumps: Systems and Applications

10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 1

Gary Phetteplace, PhD, PEGWA Research LLC

Lyme, [email protected]

Efficiency Vermont is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Learning ObjectivesLearning ObjectivesAt the end of this program, participants will be able to:

Understand the Northeast's Best Practices for Geothermal Heat Pumps

Be proficient in Design, Installation & Operational best practices

(Loads, sizing, ventilation, controls, energy consumption, routine

maintenance)

Understand the importance of pumping in the design of an efficient

Geothermal heat pump system.

Understand the lessons learned from practical experience

Course EvaluationsIn order to maintain high-quality learning experiences, please access the

evaluation for this course by logging into CES Discovery and clicking on the Course Evaluation link on the left side of the page.

Now for my“Expectation Management”

Slide

Now for my“Expectation Management”

Slide• Introduction to: the most common types of Introduction to: the most common types of

ground-source heat pump systems and a few of ground-source heat pump systems and a few of their design details/issues. their design details/issues.

• Level of detail is NOT SUFFICIENT for system Level of detail is NOT SUFFICIENT for system design, nor is coverage close to complete. design, nor is coverage close to complete.

• Intent is that participant will start to become a Intent is that participant will start to become a more intelligent consumer of the technology. more intelligent consumer of the technology.


Commercial Vs. Residential Commercial Vs. Residential

• Much of what I will say today is applicable to both Much of what I will say today is applicable to both commercial scale and residential scale systems commercial scale and residential scale systems however this is a bit more focus on commercial however this is a bit more focus on commercial scale systemsscale systems

• Commercial scale geothermal heat pump systems Commercial scale geothermal heat pump systems offer some challenges that residential systems do offer some challenges that residential systems do notnot

• Commercial scale systems also offer many more Commercial scale systems also offer many more opportunities and in general better economics opportunities and in general better economics


Geothermal Heat Pumps and Geothermal Energy

Geothermal Heat Pumps and Geothermal Energy

• Geothermal heat pumps should not be confused Geothermal heat pumps should not be confused with “true Geothermal Energy”.with “true Geothermal Energy”.

• True geothermal energy is normally in the form of True geothermal energy is normally in the form of hot water or steam geysers or hot springs that hot water or steam geysers or hot springs that may be used directly for space heating, may be used directly for space heating, agriculture/aquiculture, and even in some cases agriculture/aquiculture, and even in some cases electric power generation.electric power generation.

• To a varying degrees geothermal heat pumps To a varying degrees geothermal heat pumps make limited use of energy from the earth, make limited use of energy from the earth, however largely they use the earth as an energy however largely they use the earth as an energy storage device.storage device.


Heat Pumpsand how they work

Heat Pumpsand how they work


Fundamentals Fundamentals

• Heat normally flows from regions/bodies at Heat normally flows from regions/bodies at warmer temperatures to colder ones, analogous warmer temperatures to colder ones, analogous to water flowing down hill. to water flowing down hill.

• If we want to make heat move in the opposite If we want to make heat move in the opposite direction on the temperature scale, energy must direction on the temperature scale, energy must be input, just as we must input energy to move be input, just as we must input energy to move water to a higher elevation.water to a higher elevation.

• Moving heat up the temperature scale is the Moving heat up the temperature scale is the purpose of a heat pump, air-conditioner, or purpose of a heat pump, air-conditioner, or refrigerator. refrigerator.

• In terms of the basic physics involved they are all In terms of the basic physics involved they are all the same, the nomenclature is strictly a function the same, the nomenclature is strictly a function of the application. of the application.


Heat pumps, Air-Conditioners, and Refrigerators: what’s the difference?

Heat pumps, Air-Conditioners, and Refrigerators: what’s the difference?

PurposeHeat Source (Tc)

Heat Sink (Th)

RefrigeratorCool interior of refrigerator

Interior of refrigerator

Room Air

Air-Conditioner

Space Cooling

Room airOutdoor air or other

Heat PumpSpace Heating

Outdoor air or other

Room Air

10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 10

So how does a heat pump or refrigerator work?So how does a heat pump or refrigerator work?

• It’s some thermodynamic trickery that is called a It’s some thermodynamic trickery that is called a “vapor compression cycle”.“vapor compression cycle”.

• This cycle basically exploits the fact that at lower This cycle basically exploits the fact that at lower pressures liquids boil at lower temperatures.pressures liquids boil at lower temperatures.

• Just as water boils at a lower temperature at 10,000 Just as water boils at a lower temperature at 10,000 feet where the atmospheric pressure is lower, a feet where the atmospheric pressure is lower, a refrigerant behaves the same way.refrigerant behaves the same way.

• Forcing the refrigerant around a cycle between two Forcing the refrigerant around a cycle between two temperatures by changing it’s pressure allows heat to temperatures by changing it’s pressure allows heat to be transferred up the temperature scale.be transferred up the temperature scale.


Diagram of how a Heat Pump worksDiagram of how a Heat Pump works


So what does a Heat Pump look like?So what does a Heat Pump look like?


A diagrammatic representation of a Water-to-Air Heat Pump

A diagrammatic representation of a Water-to-Air Heat Pump


Courtesy of Steve Kavanaugh

Geothermal Heat Pump BasicsGeothermal Heat Pump Basics


Courtesy of Steve Kavanaugh

Why is a heat pump advantageous?Why is a heat pump advantageous?

• It turns out that if you don’t need to move the heat very far up the It turns out that if you don’t need to move the heat very far up the temperature scale, it takes a lot less energy to do so than to create temperature scale, it takes a lot less energy to do so than to create the heat by another means (i.e. burn fuel).the heat by another means (i.e. burn fuel).

• A “lot less” is the order of one third or one forth. A “lot less” is the order of one third or one forth. • It’s also a simple matter to change the direction of the refrigerant It’s also a simple matter to change the direction of the refrigerant

flow such that a heat pump can provide both heating and cooling; flow such that a heat pump can provide both heating and cooling; i.e. air-conditioning becomes part of the system at negligible extra i.e. air-conditioning becomes part of the system at negligible extra cost. cost.

• In larger buildings like schools, multiple heat pumps are often In larger buildings like schools, multiple heat pumps are often connected to a single circulating loop of water and not only is it connected to a single circulating loop of water and not only is it possible for one unit to be heating while another cooling, it’s possible for one unit to be heating while another cooling, it’s advantageous. advantageous.

• Efficiency is increased because it’s possible to move much of the Efficiency is increased because it’s possible to move much of the heat around with water instead of air. heat around with water instead of air.


Measure of heat pump performance: COP (coefficient of performance)

Measure of heat pump performance: COP (coefficient of performance)


Useful Heat Effect

Energy InputCOP

Useful heat effect may be heating, cooling, or hot water heating for example. Energy input is normally in the form of electricity.

Heat Pump PerformanceHeat Pump Performance


3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

20 30 40 50 60 70 80 90 100

COP

Entering Liquid Temperature (F)

Premium unit, Cooling

Premium unit, Heating

Standard unit, Cooling

Standard unit, Heating

COP Vs EERCOP Vs EER

• The EER is a parameter with an inconsistent set of units The EER is a parameter with an inconsistent set of units which the air-conditioning industry prefers because it which the air-conditioning industry prefers because it makes cooling performance look better.makes cooling performance look better.

• The COP can be found by dividing the EER (expressed The COP can be found by dividing the EER (expressed in Btu/hr of output per Watt of input) by 3.412. in Btu/hr of output per Watt of input) by 3.412.

• The COP is dimensionless.The COP is dimensionless.• The COP is used in Europe.The COP is used in Europe.• If you get the idea that I think using the EER is stupid, If you get the idea that I think using the EER is stupid,

you are right. you are right.


Cooling Equipment CapacityCooling Equipment Capacity

• Cooling equipment capacity is normally expressed in Cooling equipment capacity is normally expressed in “Tons”“Tons”

• A “Ton” of cooling is equivalent to 12,000 Btu/hrA “Ton” of cooling is equivalent to 12,000 Btu/hr• The “Ton” is carried over from the earliest days of ice The “Ton” is carried over from the earliest days of ice

based refrigeration and is equivalent to the amount of based refrigeration and is equivalent to the amount of refrigeration effect that is derived from thawing 2000 refrigeration effect that is derived from thawing 2000 lbm of ice in one daylbm of ice in one day

• Cooling capacity outside of the North America is Cooling capacity outside of the North America is expressed in kW, which is more rationalexpressed in kW, which is more rational


The ground as a heat source

The ground as a heat source


Example calculated soil temperaturesExample calculated soil temperatures


14

24

34

44

54

64

-10.0

-5.0

0.0

5.0

10.0

15.0

20.0

0 30 60 90 120 150 180 210 240 270 300 330 360

Tem

per

atu

re (

F)

Tem

per

atu

re (

C)

Julian Day

Annual soil temperature variation with depthfor a turf surface in North Eastern VT

0.5 ft

1 ft

3 ft

6 ft

9 ft

15 ft

24 ft

Note: This is not a generalized result, it is based on a number of assumptions – DON’T USE THIS FOR YOUR APPLICATION.

Some measured soil temperaturesSome measured soil temperatures


Ft. Polk, LA Testwell Temperatures

10.0

15.0

20.0

25.0

30.0

35.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 4 8 12 16 20 24 28 32 36 40 44 48 52 4 8 12 16 20 24 28 32 36 40 44 48 52 4 8 13 17 21 25 29 33 37 41 45 49

WEEK

TE

MP.

(C

)

1-FT

6-FT

31-FT

181-FT

Summary thoughts on the ground as heat source/sinkSummary thoughts on the ground as heat source/sink

• Stable temperatures even at moderate depths are very Stable temperatures even at moderate depths are very favorable for heat pumps.favorable for heat pumps.

• The ground has a relatively high capacity to accept/provide The ground has a relatively high capacity to accept/provide heat, heat, but an understanding of how to accomplish the heat but an understanding of how to accomplish the heat exchange is requiredexchange is required..

• When compared to ambient air as a heat source/sink, the When compared to ambient air as a heat source/sink, the ground is far superior due to stable temperatures.ground is far superior due to stable temperatures.– With outdoor air the demand for heating/cooling is With outdoor air the demand for heating/cooling is

exactly coincident with it’s ability to provide the exactly coincident with it’s ability to provide the opposite and it’s inability to provide what is needed.opposite and it’s inability to provide what is needed.

– Air-Source heat pumps are largely responsible for the Air-Source heat pumps are largely responsible for the bad rap that heat pumps have taken in years past.bad rap that heat pumps have taken in years past.


Basic System TypesBasic System Types


TerminologyGeothermal Heat Pump (GHP)

Ground Source Heat Pump (GSHP)GeoExchange

Earth Energy System

Open Loop SystemsGround Water Heat Pump (GWHP)

Closed Loop SystemsGround Coupled Heat Pump (GCHP)

Lake Loop SystemsSurface Water Heat Pump (SWHP)

Open LoopHorizontal Closed LoopVertical

U-tubeHybrid

Large Bore Spiral

Slinky2 pipe4 pipeothers

Direct Indirect

Small open loop

Standing column(Energy Well)

Slide courtesy of Kevin Rafferty

10 February 2011 Slide 26(c) Gary Phetteplace, GWA Research, LLC

CLOSED LOOP Vertical Ground Coupled

CLOSED LOOP Vertical Ground Coupled


• AdvantagesAdvantages– low land area requirement.low land area requirement.– stable deep soil temperature.stable deep soil temperature.– adaptable to many sites.adaptable to many sites.

• DisadvantagesDisadvantages– may have high cost.may have high cost.– does not work well in some does not work well in some

geological conditions.geological conditions.– needs experienced vertical needs experienced vertical

loop installer. That is often not loop installer. That is often not your conventional well driller. your conventional well driller.

CLOSED LOOPHorizontal Ground Coupled

CLOSED LOOPHorizontal Ground Coupled


• AdvantagesAdvantages– may have lower first cost.may have lower first cost.– less special skills.less special skills.– less uncertainty in site conditions, less uncertainty in site conditions,

but soil conditions can vary but soil conditions can vary seasonally.seasonally.

• DisadvantagesDisadvantages– high land area requirement.high land area requirement.– limited potential for HX limited potential for HX

w/groundwater.w/groundwater.– wider seasonal temperature swings, wider seasonal temperature swings,

lower efficiency. lower efficiency.

CLOSED LOOPSlinky Ground Coupled

CLOSED LOOPSlinky Ground Coupled


• AdvantagesAdvantages– those of horizontal ground-coupled.those of horizontal ground-coupled.– but less land area.but less land area.– adaptable to wide range of adaptable to wide range of

construction equipment.construction equipment.

• DisadvantagesDisadvantages– lots of pipe and pumping.lots of pipe and pumping.– widest seasonal temperaturewidest seasonal temperature

swings, lowest efficiency. swings, lowest efficiency.

Surface Water SystemsSurface Water Systems• AdvantagesAdvantages

– Low first costLow first cost– Direct cooling may be Direct cooling may be

possiblepossible

• DisadvantagesDisadvantages– FishermenFishermen– Wide seasonal temperature Wide seasonal temperature

swings, high imbalance in swings, high imbalance in heating/cooling heating/cooling performanceperformance

– Commercial-scale systems Commercial-scale systems require significant water require significant water bodies bodies


(Illustration from Kavanaugh and Rafferty, 1997)

OPEN LOOPGround WaterOPEN LOOP

Ground Water


Open loop ground water systemOpen loop ground water system

• AdvantagesAdvantages– May have lowest first cost, especially for large loadsMay have lowest first cost, especially for large loads– Stable source temperature, high efficiencyStable source temperature, high efficiency– Some direct cooling possibleSome direct cooling possible– Oldest, lots of experience (a lot of the early systems had Oldest, lots of experience (a lot of the early systems had

problems, most of which would have been solved by a problems, most of which would have been solved by a heat exchanger isolating the ground water)heat exchanger isolating the ground water)

• DisadvantagesDisadvantages– Environmental requirements may be tougherEnvironmental requirements may be tougher– Site specificSite specific– Poor water quality can cause difficulties, isolating Poor water quality can cause difficulties, isolating

ground water from heat pumps is often necessary ground water from heat pumps is often necessary


Standing Column WellStanding Column Well• This system is, in concept, a cross This system is, in concept, a cross

between a vertical ground-coupled between a vertical ground-coupled system and a open loop ground system and a open loop ground water system:water system:– @ 0% bleed it’s like a ground-@ 0% bleed it’s like a ground-

coupled system using the water coupled system using the water directly for the ground coupling, directly for the ground coupling, except it only engages the except it only engages the ground from the static water ground from the static water level down and there may be level down and there may be some losses in potential heat some losses in potential heat transfer due to transfer due to stratification/poor mixing.stratification/poor mixing.

– @100% bleed it’s an open loop @100% bleed it’s an open loop system with disposal at the system with disposal at the surface. surface.


Standing Column WellStanding Column Well• AdvantagesAdvantages

– An alternative in areas with high drilling costs An alternative in areas with high drilling costs and formations producing limited amounts of and formations producing limited amounts of waterwater

• DisadvantagesDisadvantages

– Limited ground-couplingLimited ground-coupling

– Site specific, may require multiple, deep wellsSite specific, may require multiple, deep wells

– Poor water quality can cause difficultiesPoor water quality can cause difficulties

– Bleed water disposal may be problematicBleed water disposal may be problematic

– Pumping costs will be high at high bleed ratesPumping costs will be high at high bleed rates

– Inadequate design criteria Inadequate design criteria


Brief Overview of Design Issues for

Ground-Coupled Systems

Brief Overview of Design Issues for

Ground-Coupled Systems


Design of the ground-couplingDesign of the ground-coupling

• Sizing of the ground-coupling for a heat pump is different than sizing Sizing of the ground-coupling for a heat pump is different than sizing conventional equipment.conventional equipment.– The capacity of the ground to absorb or provide heat is a transient The capacity of the ground to absorb or provide heat is a transient

heat transfer problem.heat transfer problem.– The thermal state of the ground is determined by prior heat The thermal state of the ground is determined by prior heat

addition/extractions rates and durations. addition/extractions rates and durations. – While significant imbalance of heat extraction/heat rejection can be While significant imbalance of heat extraction/heat rejection can be

tolerated, the long term impacts must be considered.tolerated, the long term impacts must be considered.– The ground can not be assumed infinite and the interaction of The ground can not be assumed infinite and the interaction of

adjacent borehole heat exchangers is very important for commercial adjacent borehole heat exchangers is very important for commercial scale systems. scale systems.

• Bottom line is that we need to know the load duration information as Bottom line is that we need to know the load duration information as well as peak load and we need a design tool that appropriately considers well as peak load and we need a design tool that appropriately considers all these factors as well as accurately models the heat transfer in the all these factors as well as accurately models the heat transfer in the ground.ground.


Information required for design of ground-coupled HVAC Vs conventional HVAC system

Information required for design of ground-coupled HVAC Vs conventional HVAC system

• Conventional fossil-fuel firedConventional fossil-fuel fired– Fuel availabilityFuel availability– Maximum (design) heat loadMaximum (design) heat load– Maximum cooling loadMaximum cooling load

• Ground-coupledGround-coupled– ““Block” loads, their timing and Block” loads, their timing and

duration, heating and cooling duration, heating and cooling combined, possibility domestic combined, possibility domestic hot water as wellhot water as well

– Thermal properties of the Thermal properties of the groundground

– Undisturbed ground temperatureUndisturbed ground temperature– Geology and it’s impact on Geology and it’s impact on

drillingdrilling– Heat pump performanceHeat pump performance– Tentative ground-coupling Tentative ground-coupling

layout consistent w/site layout consistent w/site – Planned borehole design Planned borehole design

including sizing, grouting, including sizing, grouting, backfill, etc.backfill, etc.


Design of the ground-couplingDesign of the ground-coupling


(Courtesy of Steve Kavanaugh)

Vertical Ground-Loop DesignVertical Ground-Loop Design

• Design software essential for commercial- scale Design software essential for commercial- scale systems. Sources:systems. Sources:– GchpCalc Version 4.2, Energy Information GchpCalc Version 4.2, Energy Information

Services, www.geokiss.com, $300Services, www.geokiss.com, $300– GLHEPRO V.3.0, International Ground Source GLHEPRO V.3.0, International Ground Source

Heat Pump Association (IGSHPA), Heat Pump Association (IGSHPA), www.igshpa.okstate.edu, $500, $500


http://www.igshpa.okstate.edu/

Other Ground-Loop Considerations –PipingOther Ground-Loop Considerations –Piping

• High Density Polyethylene (HDPE) piping is only piping High Density Polyethylene (HDPE) piping is only piping acceptable for use, see ASHRAE manual for Specs. acceptable for use, see ASHRAE manual for Specs.

• All joints that are buried in the ground must be fused, All joints that are buried in the ground must be fused, mechanical types of joints like barbed fittings and clamps mechanical types of joints like barbed fittings and clamps should never be used. should never be used.

• Fusion joints are typically butt fused but sometimes socket Fusion joints are typically butt fused but sometimes socket fused joints are used on the smaller diameters.fused joints are used on the smaller diameters.

• Buried vaults are sometimes used to allow isolation and Buried vaults are sometimes used to allow isolation and testing remote from the building and supply and return testing remote from the building and supply and return piping from that point to the building. piping from that point to the building.

• A high capacity pump is used to flush each borehole heat A high capacity pump is used to flush each borehole heat exchanger (or a few if in series) before they are connected to exchanger (or a few if in series) before they are connected to the headers. the headers.


Sub-header manifolding school project near Reno, NV

Sub-header manifolding school project near Reno, NV


(Courtesy of Lisa Meline)

Other Ground-Loop Considerations –Thermal testsOther Ground-Loop Considerations –Thermal tests

• Through site characterization, including test boring is Through site characterization, including test boring is advisable, especially where little is known about the advisable, especially where little is known about the geological conditions geological conditions at the job siteat the job site. .

• For larger projects, 25 tons or more, in-situ thermal For larger projects, 25 tons or more, in-situ thermal properties tests will probably be justified. Much can properties tests will probably be justified. Much can be learned about drilling conditions from this as well be learned about drilling conditions from this as well and the test well can be integrated into final well field. and the test well can be integrated into final well field.

• Recommendations for thermal properties testing Recommendations for thermal properties testing requirements and methods can be Found in Chapter requirements and methods can be Found in Chapter 32 of the 2007 ASHRAE HVAC Applications Handbook32 of the 2007 ASHRAE HVAC Applications Handbook..


Other Ground-Loop Considerations –Thermal testsOther Ground-Loop Considerations –Thermal tests


(Illustration from Kavanaugh and Rafferty, 1997)

Page 44

Thermal properties test apparatusThermal properties test apparatus

10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

Pumping energy can destroy the efficiency of an otherwise efficient system

Pumping energy can destroy the efficiency of an otherwise efficient system


(from Kavanaugh and Rafferty, 1997).

Summary thoughts for closed loop ground-coupled systems

Summary thoughts for closed loop ground-coupled systems

• Do not undersize (or oversize) the loop fieldDo not undersize (or oversize) the loop field• Use Energy Star rated heat pumpsUse Energy Star rated heat pumps• Think system efficiency and try for an “A” grade Think system efficiency and try for an “A” grade

in pumpingin pumping• Conduct thermal conductivity tests for larger Conduct thermal conductivity tests for larger

commercial scale jobscommercial scale jobs• Use design software for larger commercial scale Use design software for larger commercial scale

jobsjobs• Don’t fall pray to what appears to be heat transfer Don’t fall pray to what appears to be heat transfer

magicmagic


Overview of Design Issues for Ground Water Systems

Overview of Design Issues for Ground Water Systems


Open Loop - Indirect

Prod. Well

Inj. Well

Circulating Pump

Heat Exchanger

Standing Column System

10% to waste

Open Loop - Direct

Prod. Well

Inj. Well

Pressure tanks

Open Loop system typesOpen Loop system types


(Illustration courtesy Kevin Rafferty)

0

200

400

600

800

1000

1200

Co

st in

$/to

n

0 100 200 300 400 500 System Load Tons

4 wells@600ft

2 wells@800ft

2wells@200ft

4wells@200ft

GC@200ft/ton@$5

Open Loop System Costs60 F Ground Water

Open loop system cost is a strong function of system size, ground coupled system cost is essentially flat

Open loop system cost is a strong function of system size, ground coupled system cost is essentially flat


(Illustration courtesy Kevin Rafferty)

When determining water flow rate there is a trade off between heat pump efficiency and pumping costs.

Thus an optimum water flow rate exists

When determining water flow rate there is a trade off between heat pump efficiency and pumping costs.

Thus an optimum water flow rate exists


0

1000

2000

3000

4000

5000

6000

7000

8000

46000

47000

48000

49000

50000

51000

52000

53000

54000

55000

56000

1.30 1.50 1.70 1.90 2.10 2.30 2.50 2.70 2.90

Gro

un

d W

ater

Pu

mp

ing

Pow

er (

W)

Hea

t P

um

p a

nd

Tot

al P

ower

(W

)

Ground Water Flow (gpm/ton)

← Total Power

Ground Water Pumping Power →

← Heat pump and BuildingLoop Circulating Pump Power

The optimum flow rate will be lower fordeeper static levels within the well

The optimum flow rate will be lower fordeeper static levels within the well


y = -0.2028x2 + 1.0917x + 2.0354R² = 0.9995

2.80

2.90

3.00

3.10

3.20

3.30

3.40

3.50

1.30 1.50 1.70 1.90 2.10 2.30 2.50 2.70 2.90

Sy

stem

CO

P

in H

eati

ng

Ground Water Flow Rate (gpm/ton)

20

40

75

100

125

175

200

250

Optimums

Well Static Level (ft)

Open Loop Design Issues SummaryOpen Loop Design Issues Summary• Site Site

Regulatory issuesRegulatory issues

Drill and test earlyDrill and test early

• Building Building Design for block loadDesign for block load

Building loop pump – 7.5 hp or less per 100tonsBuilding loop pump – 7.5 hp or less per 100tons

Use small heat pump units (< 6tons)Use small heat pump units (< 6tons)

Use efficient heat pump units (Energy Star rated)Use efficient heat pump units (Energy Star rated)

• Groundwater Groundwater

Flow (usually 1-2 gpm/ton)Flow (usually 1-2 gpm/ton)

Chemistry – analysis, previous experience, sand removalChemistry – analysis, previous experience, sand removal

PressurizationPressurization

Isolation – heat exchanger (2 to 4F approach)Isolation – heat exchanger (2 to 4F approach)

• WellsWellsProduction well pump controlProduction well pump control

Production/injection separationProduction/injection separation

Geohydrologist consultant needed?Geohydrologist consultant needed?


(Slide courtesy of Kevin Rafferty)

Summary of Ground-Source vs. Conventional Systems

Summary of Ground-Source vs. Conventional Systems

• GSHP AdvantagesGSHP Advantages– Ideal zone controlIdeal zone control– Simple, highly reliable Simple, highly reliable

controls and controls and equipmentequipment

– Low operating costLow operating cost– Low maintenanceLow maintenance– Less floor area Less floor area

requirementsrequirements– No on site fuelNo on site fuel– GreenGreen technology technology– Heat recovery hot Heat recovery hot

water heating possiblewater heating possible

• GSHP DisadvantagesGSHP Disadvantages– Higher first costs Higher first costs

compared to some compared to some systemssystems

– Experienced designers Experienced designers and design guidance and design guidance limitedlimited

– Installation Installation infrastructure infrastructure regionally inadequateregionally inadequate


EconomicsEconomics


DoD GCHP installationsDoD GCHP installations


Climate ZonesClimate Zones


Payback by Climate ZonePayback by Climate Zone


How do the energy trends favor GSHP?Phetteplace’s Normalized Energy CostsHow do the energy trends favor GSHP?Phetteplace’s Normalized Energy Costs


Electric generation mix in the USElectric generation mix in the US


Relative Heating Costs for Phetteplace’s Energy CostsRelative Heating Costs for Phetteplace’s Energy Costs


Environmental BenefitsEnvironmental Benefits• Often overstated in terms of being renewableOften overstated in terms of being renewable• Remember the heat pump does not make or Remember the heat pump does not make or

convert energy, it just moves it around and that convert energy, it just moves it around and that uses energy that may not be renewableuses energy that may not be renewable

• Thus its carbon footprint will be derived from the Thus its carbon footprint will be derived from the driving energy input source (i.e. electricity).driving energy input source (i.e. electricity).

• That’s not all bad news as the next slide shows. That’s not all bad news as the next slide shows.


CO2 emissions for various means of Heating

CO2 emissions for various means of Heating


CO2 Emissions Approximate CO2 Emissions Reduction ReductionHeating Raw Energy Conversion Delivered Heating by use of by use ofMethod (lbs/MMBtu) Efficiency (lbs/MMBtu) GHP @ COPh=4 GHP @ COPh=3.5

Electricity Resistance 301.8 100% 301.8 75% 71%Natural Gas 117.1 90% 130.1 42% 34%

Distillate Fuel Oil (#1, 2 & 4) 161.4 90% 179.3 58% 52%Residual Fuel Oil (#5 & 6) 173.0 90% 192.2 61% 55%

Kerosene 159.5 90% 177.2 57% 51%Propane 139.2 90% 154.7 51% 44%

GHP @ Heating COP of 4 ------------ ------------ 75.4 0% -14%GHP @ Heating COP of 3.5 ------------ ------------ 86.2 13% 0%

Closing Remarks and References

Closing Remarks and References


Advice on Selecting DesignersAdvice on Selecting Designers• These systems are actually quite simple, but they are entirely These systems are actually quite simple, but they are entirely

foreign to many HVAC designers, especially in some regions of foreign to many HVAC designers, especially in some regions of the US the Northeast being one of them.the US the Northeast being one of them.

• The inexperienced designer usually attempts to treat these The inexperienced designer usually attempts to treat these systems like other HVAC systems; if that’s the case results may systems like other HVAC systems; if that’s the case results may suffer in terms of:suffer in terms of:– Low efficiencyLow efficiency

– Higher first costHigher first cost

– Both of the aboveBoth of the above

– Worse case not even work, or fail prematurelyWorse case not even work, or fail prematurely

• As a consumer, the most prudent thing you can do is get As a consumer, the most prudent thing you can do is get someone who has demonstrated they know these systems and someone who has demonstrated they know these systems and can design/install successful ones, for commercial systems can design/install successful ones, for commercial systems require a require a trainedtrained PE. PE.


Advice on Selecting Designers (Cont.)Advice on Selecting Designers (Cont.)• For residential systems the design will often be done by the For residential systems the design will often be done by the

installer, again look for someone who has demonstrated they installer, again look for someone who has demonstrated they know these systems and can design/install successful ones.know these systems and can design/install successful ones.

• Do not accept systems that are geothermal in name only, for Do not accept systems that are geothermal in name only, for example:example:– A ground loop has been connected to a chiller and a central air A ground loop has been connected to a chiller and a central air

handling systemhandling system

– There is too little ground coupling and backup systems are There is too little ground coupling and backup systems are responsible for satisfying much of the loadresponsible for satisfying much of the load

• Avoid systems with elaborate and expensive controls: distributed Avoid systems with elaborate and expensive controls: distributed heat pumps do not need more than thermostats for control.heat pumps do not need more than thermostats for control.

• Insist on minimum provisions such as pressure and temperature Insist on minimum provisions such as pressure and temperature ports (P&T ports or Pete’s Plugs) for trouble shooting. ports (P&T ports or Pete’s Plugs) for trouble shooting.


Advice on Selecting Designers(Cont.)Advice on Selecting Designers(Cont.)

• For both residential and commercial, be wary of “one trick For both residential and commercial, be wary of “one trick horses”. If they do not know of the major types of systems and horses”. If they do not know of the major types of systems and can not explain to you how they arrived at the one they are can not explain to you how they arrived at the one they are recommending for you, look for someone else who can. recommending for you, look for someone else who can.

• Consider bringing both design and installation expertise in from Consider bringing both design and installation expertise in from other areas if the infrastructure is lacking in your part of the other areas if the infrastructure is lacking in your part of the country, for larger systems it will usually be an investment well country, for larger systems it will usually be an investment well worthwhile both in terms of achieving a successful system and worthwhile both in terms of achieving a successful system and often in terms of reducing costs. often in terms of reducing costs.

• If you do not feel completely comfortable in judging If you do not feel completely comfortable in judging designer/installer qualifications, seek the advice of an expert.designer/installer qualifications, seek the advice of an expert.


Advice on Selecting Designers: Commercial Systems

Advice on Selecting Designers: Commercial Systems

• For commercial design make sure your designer has taken a short-For commercial design make sure your designer has taken a short-course on design of these systemscourse on design of these systems

• Be sure the designer obtains a copy of one of the recommended Be sure the designer obtains a copy of one of the recommended design software programs design software programs and training on how to use itand training on how to use it. For . For commercial scale systems do not size ground-coupling based on commercial scale systems do not size ground-coupling based on rules-of-thumb, manufacturers recommendations, etc. rules-of-thumb, manufacturers recommendations, etc.

• Check to see that the designer has obtained copies of the accepted Check to see that the designer has obtained copies of the accepted design guides design guides and uses themand uses them, some are listed at the end of this , some are listed at the end of this presentation. If he/she has questions be sure they consult an presentation. If he/she has questions be sure they consult an experienced designer.experienced designer.

• Do not let the designer make the systems overly complicated by Do not let the designer make the systems overly complicated by adding unnecessary backup, redundancy, unnecessary controls, etc. adding unnecessary backup, redundancy, unnecessary controls, etc.


Advice on Selecting InstallersAdvice on Selecting Installers

• Again, as a consumer, the most prudent thing you can do is get Again, as a consumer, the most prudent thing you can do is get someone who has demonstrated they know these systems and someone who has demonstrated they know these systems and can install successful ones. Check references and ask not only can install successful ones. Check references and ask not only how well the system works but how much energy it is using.how well the system works but how much energy it is using.

• For commercial scale or large residential developments consider For commercial scale or large residential developments consider bringing installation expertise in from other areas .bringing installation expertise in from other areas .

• IGSHPA certification of the installer is a necessary but not IGSHPA certification of the installer is a necessary but not sufficient condition. sufficient condition.

• Attempt to find installers who will take responsibility for both the Attempt to find installers who will take responsibility for both the interior and exterior portions of the system, either within their interior and exterior portions of the system, either within their organization or with established partners. organization or with established partners.

• Monitor the installation. Monitor the installation.


ReferencesReferences

• Recommended design references:Recommended design references:– 2007 ASHRAE Handbook, HVAC Applications2007 ASHRAE Handbook, HVAC Applications. Chapter 32 – . Chapter 32 –

Geothermal Energy. American Society of Heating, Geothermal Energy. American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), Refrigerating, and Air-Conditioning Engineers (ASHRAE), Atlanta, GA.Atlanta, GA.

– Kavanaugh, Steven and Kevin Rafferty. (1997). Kavanaugh, Steven and Kevin Rafferty. (1997). Ground Ground source heat pumps—design of geothermal systems for source heat pumps—design of geothermal systems for commercial and institutional buildingscommercial and institutional buildings. American Society of . American Society of Heating, Refrigerating, and Air-Conditioning Engineers Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), Atlanta, GA.(ASHRAE), Atlanta, GA.

• Recommended survey article:Recommended survey article:– Phetteplace, G. (2007). Geothermal Heat Pump Technology, Phetteplace, G. (2007). Geothermal Heat Pump Technology,

Journal of Energy EngineeringJournal of Energy Engineering, Vol. 133, No. 1, pgs. 32-38, , Vol. 133, No. 1, pgs. 32-38, American Society of Civil Engineers.American Society of Civil Engineers.


CreditsCredits

• Kevin Rafferty, Engineering Consultant, Klamath Falls, OR. Kevin Rafferty, Engineering Consultant, Klamath Falls, OR. [email protected] (See heatspring.com for design course (See heatspring.com for design course offerings)offerings)

• Steve Kavanaugh, Energy Information Services, Steve Kavanaugh, Energy Information Services, www.geokiss.com, , [email protected] (See heatspring.com (See heatspring.com for design course offerings)for design course offerings)

• Kirk Mescher, CM Engineering, Columbia, MO. 573-874-Kirk Mescher, CM Engineering, Columbia, MO. 573-874-9455, 9455, [email protected], www.cmeng.com, www.cmeng.com

• Lisa Meline, meline engineering, Sacramento, CA. 916-366-Lisa Meline, meline engineering, Sacramento, CA. 916-366-3458, 3458, [email protected], , www.meline.com


mailto:[email protected]

http://www.geokiss.com/




http://www.meline.com/

Thank You!Thank You!


Contact Information:Dr. Gary Phetteplace, PEGWA Research LLC7 Masa Morey LaneLyme, NH [email protected]




Documents

Ground Source Heat Pumps: Systems and Applications 10 February 2011(c) Gary Phetteplace, GWA Research, LLCSlide 1 Gary Phetteplace, PhD, PE GWA Research