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Transcript of Ground Source Heat Pumps: Systems and Applications 10 February 2011(c) Gary Phetteplace, GWA...
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 5
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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 6
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 7
Heat Pumpsand how they work
Heat Pumpsand how they work
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 8
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 9
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 11
Diagram of how a Heat Pump worksDiagram of how a Heat Pump works
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 12
So what does a Heat Pump look like?So what does a Heat Pump look like?
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 13
A diagrammatic representation of a Water-to-Air Heat Pump
A diagrammatic representation of a Water-to-Air Heat Pump
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 14
Courtesy of Steve Kavanaugh
Geothermal Heat Pump BasicsGeothermal Heat Pump Basics
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 15
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 16
Measure of heat pump performance: COP (coefficient of performance)
Measure of heat pump performance: COP (coefficient of performance)
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 17
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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 18
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 19
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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 20
The ground as a heat source
The ground as a heat source
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 21
Example calculated soil temperaturesExample calculated soil temperatures
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 22
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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 23
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 24
Basic System TypesBasic System Types
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 25
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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 27
• 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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 28
• 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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 29
• 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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 30
(Illustration from Kavanaugh and Rafferty, 1997)
OPEN LOOPGround WaterOPEN LOOP
Ground Water
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 31
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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 32
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 33
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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 34
Brief Overview of Design Issues for
Ground-Coupled Systems
Brief Overview of Design Issues for
Ground-Coupled Systems
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 35
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 36
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 37
Design of the ground-couplingDesign of the ground-coupling
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 38
(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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 39
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.
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 40
Sub-header manifolding school project near Reno, NV
Sub-header manifolding school project near Reno, NV
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 41
(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..
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 42
Other Ground-Loop Considerations –Thermal testsOther Ground-Loop Considerations –Thermal tests
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 43
(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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 45
(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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 46
Overview of Design Issues for Ground Water Systems
Overview of Design Issues for Ground Water Systems
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 47
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
10 February 2011 Slide 48(c) Gary Phetteplace, GWA Research, LLC
(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
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 49
(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
10 February 2011 Slide 50(c) Gary Phetteplace, GWA Research, LLC
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
10 February 2011 Slide 51(c) Gary Phetteplace, GWA Research, LLC
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?
10 February 2011 Slide 52(c) Gary Phetteplace, GWA Research, LLC
(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
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EconomicsEconomics
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DoD GCHP installationsDoD GCHP installations
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Climate ZonesClimate Zones
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Payback by Climate ZonePayback by Climate Zone
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How do the energy trends favor GSHP?Phetteplace’s Normalized Energy CostsHow do the energy trends favor GSHP?Phetteplace’s Normalized Energy Costs
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Electric generation mix in the USElectric generation mix in the US
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Relative Heating Costs for Phetteplace’s Energy CostsRelative Heating Costs for Phetteplace’s Energy Costs
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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.
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CO2 emissions for various means of Heating
CO2 emissions for various means of Heating
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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
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Thank You!Thank You!
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Contact Information:Dr. Gary Phetteplace, PEGWA Research LLC7 Masa Morey LaneLyme, NH [email protected]