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Overview of Geothermal Technologies - Cloud Object...
Transcript of Overview of Geothermal Technologies - Cloud Object...
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Introduction to Geothermal
Presented to:
Environmental Business Council
of New England
Presented by:
Richard J. Desrosiers, PG, LEP
GZA GeoEnvironmental, Inc.
Date: April 11, 2012
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Presentation Format
Geothermal Basics
Type of Ground Loops
Permitting Consideration
Life Cycle Analysis
Typical Design/Build
Feasibility Study
Test Well and Thermal Conductivity Test
Design/Construction
Permitting Issues
Financial and Incentives
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Geothermal
Geothermal – from the Greek words
“geo” = earth and “thermos” = heat
Geothermal – from deep bedrock heat
geothermal - uses geologic resources (soil, bedrock,
groundwater) to store energy in the earth (heat source or
heat sink).
– Uses a “heat pump/heat exchanging system” also
referred to as “geoexchange” and ground source
heat pumps”
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Geothermal Hot Rocks
http://www.bing.com/images/search?q=deep+geothermal+sources+&FORM=IGRE&qpvt=deep+geothermal+sources+#
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Earth’s Heat Source
http://www.bing.com/images/search?q=deep+geothermal+sources+&FORM=IGRE&qpvt=deep+geothermal+sources+#
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Geothermal Power Plant
http://www.bing.com/images/search?q=deep+geothermal+sources+&FORM=IGRE&qpvt=deep+geothermal+sources+#
Geothermal Power Plant
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Geothermal System
http://www.bing.com/images/search?q=deep+geothermal+sources+&FORM=IGRE&qpvt=deep+geothermal+sources+#
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Favorable Geothermal Zone
http://www.bing.com/images/search?q=deep+geothermal+sources+&FORM=IGRE&qpvt=deep+geothermal+sources+#
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geothermal Ground Source Heat Exchange
• Geothermal System Types
– Closed-Looped System
– Open-Looped System
– Standing Column System
• Heat Exchange
– Heat pump
• Distribution
– Water-to-water
– Water-to-air
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Geothermal - What’s that?
A proven heat exchange system that used stored
energy in the earth (soil, bedrock, groundwater)
A “heat-sink” in the summer and a “heat source”
in the winter. Exchanges BTUs
Typical geothermal depths 400 to 1,500 feet.
Annual New England ground temperature = 55ºF.
Reduces overall energy consumption.
Also referred to as “geo-exchange” or Ground
Source Heat Pump (GSHP)
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Geothermal Benefits
Decrease reliance on fossil fuels
Reduction in Carbon Footprint
American College & University President’s Climate
Commitment (2050)
Applicable in “Net Zero” (energy consumption &
carbon emissions)
Increase energy efficiency
Less maintenance than fossil fuel systems =
Lower life cycle costs; increasing your rate of
return on investment
LEED credits
Tax and utility incentives
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Taken from J. Lund, “Geothermal (Ground-source) Heat Pumps”,
Presented at IIE, Cuernavaca, México, 2007
Elements of a Geo-exchange System
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Taken from J. Lund, “Geothermal (Ground-source) Heat Pumps”,
Presented at IIE, Cuernavaca, México, 2007
Elements of a Heat Pump System
Heating Cycle Cooling Cycle
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Geothermal – SUMMER
Heat is
Exchanged
from liquid
To
Soil/Rock
Earth = HEAT SINK
GEOEXCHANGE SYSTEM
CONCENTRATES/ CIRCULATES HEAT
(BTUs)
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Geothermal – WINTER
Heat is
Exchanged
to liquid
from
Soil /Rock
GEOEXCHANGE SYSTEM
CONCENTRATES/ CIRCULATES HEAT
(BTUs)
Earth = HEAT SOURCE
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Type: Closed Loop System
A "vertical" loop of a ground-based, or an open-loop ground-source heat pump.
(Credit: WaterFurnace International)
Depths typically
300 - 500 feet
Convection Heat
Exchange
Aquifer characteristics
less important (flow
and quality)
Ground temperature,
thermal conductivity
and diffusivity are
important
Less maintenance –
no well field pumps
“Rules of Thumb”
•150 - 200 feet per ton
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Type: Open Loop System
Groundwater extraction up
to 1,500 feet
Advection Heat Exchange
Aquifer characteristics are
important (yield, quality,
temperature)
Ability to inject water into
soil/bedrock formations
Increased permitting-
regulations
More maintenance-pumps
potential for fouling/scaling
More efficient than closed-
loop (less wells)
“Rules of Thumb”
•30 – 100 feet per ton
•2.5 – 3 gpm per ton
A "vertical" loop of a ground-based, or an open-loop ground-source heat pump.
(Credit: WaterFurnace International)
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Type: “Standing Column Well”
O’Neill
Depths typically to 1,500 feet
Conductive, Advection &
Convection Heat Transfer
Similar issues as Open-Loop
Induced flow increases
temperature recovery,
increasing heat transfer
May require “Bleed” to
surface water or injection well
Increased permitting,
regulations
“Rules of Thumb”
• 37.5 to 50 ft/ton with bleed
• 50 to 75 ft/ton w/o bleed
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Definitions
Geothermal Heat Pump
Transfers heat from the ground to water or air distributed to the building
Water-to-water (hydronic systems)
Water-to-air
De-superheater
Uses heat from the ground loop to produce domestic hot water
Uses excess heat during cooling cycle
Distribution System
Ducted forces air
Radiant floor heating with ducted cooling
Hydronic (water as the heat-transfer medium)
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Integrated Geothermal Approach
= Hybrid Systems
Conventional HVAC plus geothermal system
Conventions system for peak (heating/cooling) demand
Geothermal for normal/average operating demands
Alternative to using 100% geothermal
Combine geothermal wells and heat pumps with:
Chillers or cooling towers to supplement cooling
Solar thermal collectors to supplement heating
Supplemental fossil fuel for heating
Outside Air Energy Recovery
Economic and/or design driven
Limits number/cost of geothermal boreholes
Limits geothermal to “average and not peak loads”
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Geothermal Design A Phased Approach
Define Geothermal Team
Initial Feasibility Study Site-Specific Investigation & Testing
Decision Point
System Design Geothermal Specifications Number of Boreholes Distribution system
Geothermal Well Field Construction
Borehole field inspections & QA/QC Verification that construction adheres with specifications
System Commissioning
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Geothermal Team
Geothermal Team
Professional Engineer
Professional Geologist
IGSHPA Certified GeoDesigner,
IGSHPA Accredited Installer
Design Team
Architect,
Mechanical/HVAC Engineers,
Commissioning agent
Construction Contractor
Independent consultant
No hidden agendas – not tied to any one method or
technology
Client -
(Owner)
Architects/
Engineers
construction manager
commissioning
agent
Geo-Science/
Geo-Designer
Legal
Team
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Selecting a Geothermal Consultant
Qualifications
Professional accreditations
• PE – Professional Engineer
• PG – Professional Geologist
• AI – IGSHPA Accredited Installer
• CGD – IGSHPA Certified GeoDesigner
Relevant Experience
Independent consultant
No hidden agendas – not tied to any one
method or technology
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Feasibility Study
Define building’s peak heating/cooling load Identify if applying for LEED credits
Hybrid or all geothermal
Review published/site-specific hydrogeologic &
geologic data
Define permitting and regulatory requirements
Evaluate land area and preliminary well field layout
Evaluation of potential geothermal system type
Preliminary economic analysis
Potential funding mechanisms
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Design Considerations – Close Loop
Aquifer characteristics less important
Thermal conductivity and ground temperature
Groundwater flow and quality less important
Geologic conditions may vary within well field
Wells are typically shallower (300 to 500 feet)
Potentially more wells requiring greater land area
No well field “moving” parts (potentially less
maintenance)
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Design Considerations – Open Loop & Standing Column Wells
Aquifer characteristics are important System Fouling, scaling
Groundwater flow, temperature and quality Open Loop typically requires 3 gpm per ton
Ability to re-inject pumped water Formation issues (Bleed requirements for SCW)
Surface Water discharge
Permitting or regulating issues
Wells are typically deeper (up to 1,500 feet) Potentially less wells
Potentially more maintenance (pumps and well screens
issues)
Plate-and-Frame Heat Exchanger
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Geothermal Test Well Study:
Drill full-depth test well Typical well is used as part of final system layout/design
Evaluate borehole geology and depth/quality of
groundwater
Open Loop Pumping/yield test
Water quality analyses
Adjacent uses
Closed Loop Install down-hole geo-loop and fused U-bend (pressure
test)
Grout (stabilize 5 days) borehole/geo-loop (thermally
enhanced)
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48-hour Thermal Conductivity Test
Conduct minimum of five (5) days after setting
the thermal grout;
Estimate thermal conductivity (ability of
geologic material borehole to transfer heat in
Btu/hr-ft- oF);
Thermal diffusivity (measures of how quickly
temperature recovers in ft2/day); and
Formation temperature oF.
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Thermal Conductivity Values
Formation Type Thermal Conductivity (Btu/hr ft F)
Clays 0.3 – 1.1
Sand 0.5 – 1.2
Sand & Gravel 1.2 – 2.2
Granite 1.3 – 2.1
Limestone 1.4 – 2.2
Sandstone 1.2 – 2.0
Shale 0.6 – 1.4 Oklahoma State
Test Results
Rock Type: Schist/gneiss
Thermal Conductivity: 1.81 Btu/hr-ft-F
Thermal Diffusivity: 1.16 sq-ft/day
Formation Temperature: 53.5-F
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Design/Construction
Design:
Final well field layout in conjunction with
GeoDesigner;
Driller borehole specification & cutting/fluid
management
Supplier neutral specification and performance
criteria;
Permitting
Construction:
Quality Control during:
Well drilling;
Grouting (percent solids critical)
Geo-loop installation;
Local presence provides for unannounced Site visits
QA/QC audits
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Ground Loop Components
Vertical wells or horizontal/vertical pipe loops
Header and return piping - polyethylene
Antifreeze for closed loops – propylene glycol
Safe, non-toxic, good heat transfer capacity
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Why Consider Geothermal Cost to Deliver 1 MBtu
Ref: Heat Spring Magazine 2012
System Type Energy
Cost
Delivered
Cost
($/MBtu)
Cost
Relative to
GSHP
Savings Using
GSHP
(%)
Savings
Using GSHP
($/MBtu)
Ground Source Heat Pump $0.15/kWh $11.72 - - -
Natural Gas $1.50/therm $15.79 1.3 26% $4.07
Air Source Heat Pump $0.15/kWh $21.98 1.9 47% $10.26
Propane $2.75/gal $33.21 2.8 65% $21.49
Fuel Oil $4.00/gal $35.71 3 67% $23.99
Electrical $0.15/kWh $43.96 3.8 73% $32.24
$0.00
$5.00
$10.00
$15.00
$20.00
$25.00
$30.00
$35.00
$40.00
$45.00
$50.00
Ground SourceHeat Pump
Natural Gas Air Source HeatPump
Propane Fuel Oil Electrical
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Changes in Utility Costs
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5
10
15
20
25
0
0.5
1
1.5
2
2.5
3
3.5
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4.5
9-Jan-01 9-Jan-02 9-Jan-03 9-Jan-04 8-Jan-05 8-Jan-06 8-Jan-07 8-Jan-08 7-Jan-09 7-Jan-10 7-Jan-11
Ele
ctr
ica
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ts i
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kW
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Oil
a
nd
Pro
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Co
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oll
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pe
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Oil Propane Gas Electric
Electrical costs – CT Department of Public Utility Control
Oil and Propane costs – Policy Development and Planning Division – CT Energy Management
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Conventional Roof Top HVAC Units vs Ground Source Heat Pump
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1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
8,000,000
9,000,000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Ca
sh
Flo
w (
Do
lla
rs $
)
20 -Year Life Cycle
Conventional Roof Top Ground Source Heat Pump
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Conventional Roof Top vs Ground Source Heat Pump
0
5,000,000
10,000,000
15,000,000
20,000,000
25,000,000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Ca
sh
Flo
w (
Do
lla
rs $
)
20 Year Life Cycle
Conventional Roof Top vs Ground Source Heat Pump
0
5,000,000
10,000,000
15,000,000
20,000,000
25,000,000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Cu
mu
lati
ve
Co
st
in D
oll
ars
20-Year Life Cycle
Conventional Roof Top Unit Ground Source Heat Pump
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Summary of Findings
• First Costs
– Greater for the Ground Source Heat Pump
Systems
• Annual Operational Costs
– Less for the Ground Source Heat Pumps
Systems
• Final Assessment
– Ground Source Heat Pump System was the
more cost effective system
– 8.2-year payback period
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Energy Usages
No.
Bldgs Structure Type
Area
(sq. ft.)
Heating & Cooling
Energy Sources
Energy Source (%)
Central
Plant Independent1
1 Academic Building 3,263 Natural Gas 0% 100%
1 Administration Building 2,016 Natural Gas 0% 100%
1 Athletic Facility 237,000 CHP/Natural Gas 92% 8%
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Housing 97,859 Oil and Natural Gas 0% 100%
Area “A” - Totals 340,138 64%2 36%2
Note: 1) Independent Energy Source includes natural gas, fuel oil, propane or other energy sources not connected to the central heating plant. 2) The total energy source percentage is based on: (total structure square feet/total square feet of the total area) times the percentage of the energy source from either the central plant or independent sources.
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Green House Gas Reductions
Eliminates fossil fuel to 55 structures and
reduces steam load from a central plant
Additional air conditioning provided with
geothermal that is not currently in place
Reduction of 2,300 metric tons of greenhouse
gas emissions
Equivalent to 522 passenger vehicles
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Financial Incentives for Geothermal
Federal Tax Credits
State Tax Credits
Local Property Tax Abatements
Utility Rebates
Where to start?
Database of State Incentives for Renewables &
Efficiency (www.dsireusa.org) (NC State)
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Thermal Purchase Agreements
Advantages Provides for the installation of geothermal loop field at no
upfront costs
Zero Payback Period and geothermal maintenance costs
are 40 to 63% less than fossil fuels
Demonstrates Environmental Stewardship
Aid in the development of NetZero Energy Buildings
Hedge against rising fossil fuel costs
Payments Utility-like payments - fixed price per BTU/kWh
20-year long term contract
Predictability of net operational increase expenses
Treated as operational expense not impacting balance
sheet and is deductable.
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Which is Best?
No single method is “best”
Selection depends on: Hydrogeology, Groundwater flow characteristics
Groundwater quality, Permit considerations
Future maintenance/monitoring tolerance
Life Cycle Cost, Client’s risk tolerance
Typical Systems: Closed Loop (simplest, may require more wells)
Open Loop (more equipment, perhaps less wells)
Standing Column (more complex)
Water-to-water or Water-to-air (package systems)
Can be designed in conjunction with traditional systems or stand alone;
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GZA Contact Information
Richard Desrosiers
860-858-3130
Old Faithful Geyser