D avid G. Lamothe, P.E. Senior Project Manager GZA - - PowerPoint PPT Presentation
Geotherm al Heating/ Cooling System s Presented to : NH Joint Engineering Societies 6 th Annual Conference Presented by : D avid G. Lamothe, P.E. Senior Project Manager GZA GeoEnvironmental, Inc. Manchester, New Hampshire Date: October 4,
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Geotherm al Heating/ Cooling System s
Presented to: NH Joint Engineering Societies 6th Annual Conference Presented by: David G. Lamothe, P.E.
Senior Project Manager GZA GeoEnvironmental, Inc. Manchester, New Hampshire Date: October 4, 2012
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Presentation Outline
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W hat is “Geotherm al”?
NOT HOT ROCKS!!!! NOT POWER PRODUCTION
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W hat is “Geotherm al”?
Ground Source Heat Pumps (GSHPs) Low temperature thermal exchange
(~40-90°F)
Uses renewable energy stored in the earth to heat and cool
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How Does I t W ork?
Furnace and AC replaced by GSHP
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W hy Geotherm al?
Green Technology LEED Zero Net Energy Lower Maintenance Energy Efficiency Carbon Reduction
Save $$$
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W hy Geotherm al?
To do your own comparison based on current fuel prices, your system’s efficiency, etc., go to: www.nhclimateaudit.org/calculators.php Fuel Type Fuel Unit Cost Fuel Unit of Measure Efficiency of Heating Unit Price per Million Btu Coal 330 Ton 75% 16.98
3.661 Gallon 78% 33.84 Natural Gas 1.0556 Therm 78% 13.53 Propane 3.178 Gallon 78% 44.61 Wood 210 Cord 60% 17.50 Electricity 0.13706 kWh 99% 40.56 Wood Pellets 243.86 Ton 80% 18.47 Kerosene 3.968 Gallon 80% 36.74 Geothermal 0.13706 kWh 330% 12.17
Heating Cost Comparison
Note: Fuel Unit Costs are based on average prices in the State of New Hampshire as of September 3, 2012.
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W hy Geotherm al?
~55°F
Mean earth temperature
CONSISTENTLY
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W hy Geotherm al?
10 20 30 40 50 60 70 80 90 100
Room Temperature Δ=15°F Δ=-50°F Δ=20°F Mean Earth Temperature Winter Low Air Temperature Summer High Air Temperature
Temperature, °F
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Energy Efficiency
Earth Coupling (3 to 5 kW)
Heating and Cooling (4 to 6 kW)
Grid (1 kW)
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Geotherm al Operation – SUMMER
Heat is Absorbed by Soil/Rock from Fluid GEOEXCHANGE SYSTEM (REJECTS HEAT BTUs) Earth = HEAT SINK
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Geotherm al Operation – W I NTER
Heat is Absorbed by Fluid from Soil /Rock GEOEXCHANGE SYSTEM (EXTRACTS BTUs) Earth = HEAT SOURCE
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Single Building
District system graphic
Wells drilled and connected in circuits Vault/manifold Supply and Return Headers
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District System
Serves multiple buildings
District system graphic
Central Well Field Vault/manifold
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Hybrid System
performance and limit capital costs
with:
– Chillers or cooling towers to boost cooling – Solar thermal collectors to boost heating – Supplemental fossil fuel for heating
To serve peak demand that occurs only a portion of total operating time
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Hybrid System
200 400 600 800 1000 1200 1400 1600 1800 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Load (MBh)
Load Profile
Max Heating (MBh) Max Cooling (MBh)
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Distribution System s ( Building Side) Geothermal Heat Pump
to water or air distributed to the building Media:
– Water-to-water (hydronic systems) – Water-to-air
Distribution System
ducted cooling
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Ground Heat Exchanger ( Ground Loop)
Exchanges heat with the ground
– Open to Diffusion Wells (ODW) – Standing Column Wells (SCW) – Closed Loops (CL)
Also - Pond Loops
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Open Loop System
transmissive aquifers (Cape Cod, Long Island)
important (flow/temp/chemistry)
reinject water
closed loops (water quality can cause fouling)
Extraction Well Injection Well
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Available drawdown for extraction
Available depth to water for injection
Ratio of injection wells to extraction wells may be 2:1 to 4:1
Open Loop System
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Standing Colum n W ell
(Credit: Water Energy)
injection well
advective heat transfer
dependent upon quality
ability to bleed
uncased
20’ (min.) into rock
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W hat is “Bleed?”
90 gpm 100 gpm 10 gpm Drywell, water body
Induces Flow to Well
Issues: Responsibly discharged to same aquifer Subject to permitting requirements Environmental Concerns? Foundation Settlement?
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Deviation
Most projects require 0.01 ft/ft = 15 ft Then there’s reality……
210 feet away from point of entry!
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Deviation
210 feet from point
Stabilizers and low down pressure used to limit deviation.
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Deviation
NY State – oil and gas regulations require a deviation or verticality survey for all wells (incl. geothermal) > 500 feet deep unless MWD techniques used.
NH, MA – no requirement - yet…..
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Closed Loop Vertical W ells
with ground
thermal conductivity and diffusivity important
than open systems
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Closed Loop Vertical W ells
1.25-inch HDPE pipe
Thermally enhanced grout Factory fused U-bend Soil / Rock
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Closed Loop - Horizontal Slinky
Advantages
Disadvantages
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Closed Loop – Vertical Slinky
Advantages
Disadvantages
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Lake/ Pond Loop
Advantages
Disadvantages
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Selection of Ground Loop
Permitting Risk Tolerance (O&M, Cost) Logistics Recommended Ground Loop
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Selection of Ground Loop Logistics – Phasing/sequencing
Physical restrictions – available space for well field Closed loop closer spacing but more wells typ. required
Geology
Soil, bedrock, and groundwater conditions Depth to rock, water quantity and quality Unstable rock – CL recommended Environmental conditions
Soil or groundwater contamination in vicinity? AUR/AUL?
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Permitting requirements
Client’s risk tolerance
Permitting O&M / Cost (Estimated payback period) Water quality issues - Poor water quality (i.e. high Fe, Mn
scaling and fouling issues
(Risk tolerance is often primary factor in selection) Selection of Ground Loop
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Perm it Considerations - NH
Loop
report monthly use on a quarterly basis
large groundwater withdrawal permit
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Perm it Considerations – NH ( Continued) Open Loop
For Commercial/Industrial/Institutional Residential is Exempt
water
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Perm it Considerations – NH ( Continued) Closed Loop
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Perm it Considerations -MA
Loop
reporting/registration/permitting for > 100,000 gpd (=70 gpm), [determination of non-consumptive use]
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Perm it Considerations – MA ( Continued) Open Loop
water
If > 5% to different aquifer, requires justification
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Perm it Considerations – MA ( Continued) Closed Loop
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Financial I ncentives for Geotherm al
Database of State Incentives for Renewables & Efficiency (“DSIRE”, www.dsireusa.org) http://energy.gov/savings
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Geotherm al Payback Period
New construction? Replacing an old system? Condition of existing system?
need of replacement due to avoided costs
Look at Life Cycle Costs (Capital, O&M)
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Geotherm al Team
Professional Engineers/Geologists Certified Mechanical GeoDesigner Certified Driller/Installer Architect Mechanical/HVAC Engineers Construction Contractor Commissioning Agent
No one should be tied to a certain method or technology
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“State of the Practice” for Geotherm al?
recommend a ground loop type for the site
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“State of the Practice” for Geotherm al?
recommend a ground loop type for the site
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Test W ell
well field for consideration in design of remaining well field
(soil, depth to and type of rock, groundwater quantity and quality)
conductivity test (CL)
ODW)
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Test W ell I nstallation Standing Colum n
Preparing the well for grouting Installation
Mud rotary with 12-inch stabilizer to 20’ into rock, set 8” dia. casing
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Test W ell I nstallation Standing Colum n
(Credit: Water Energy)
uncased
20’ (min.) into rock
10-12” dia. mud rotary to 20’ into rock 6.5” dia. air rotary to 1,500 ft.
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Test W ell I nstallation Closed Loop
Drilling 6-inch borehole 6-inch mud rotary bit used to set temp./perm. casing into rock, then air rotary to bottom of hole
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Test W ell I nstallation Closed Loop
Preparing the well for grouting Installation
Test Well
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Therm al Conductivity Test Closed Loop
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GZA and Geotherm al – 3 -Phase Approach
recommend a ground loop type for the site
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W ell Field Construction
Observe:
– U-bends – Circuits – Supply and Return – Well Field
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W ell Field Construction
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W ell Field Construction
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W ell Field Construction
Looping and grouting
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W ell Field Construction
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W ell Field Construction
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W ell Field Construction
Vault construction and manifold
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W ell Field Construction
Prefabricated Vault and Manifold Circuit supply and return stubs Main supply and return stubs
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W ell Field Construction
Main supply and return lines Electrofusion
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$- $500 $1,000 $1,500 $2,000 $2,500 $3,000 SCW I nstall CL I nstall SCW ( 3 0 yr) CL ( 3 0 yr) Total System Cost ($000)
244 Tons 235 Tons 113 Tons 140 Tons
Case Studies and Cost Com parisons
30 year cost includes O&M, Monitoring and Reporting
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New England Geotherm al Professionals Association
Mission
To educate and advocate for the advancement of the Geothermal Heat Pump industry in New England to increase energy efficiency and reduce dependency on fossil fuels
www.negpa.org
Membership@negpa.org
Info@negpa.org
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Questions?
David Lamothe, P.E., IGSHPA AI
GZA Senior Project Manager 603-232-8716 david.lamothe@gza.com