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, 2012 1
Presentation Outline • What is geothermal heating/cooling? • How does it work? • Why consider geothermal? • Types of Ground Loops • Permit Considerations • Financial Incentives • What is the “State of the Practice?” • Photos and Case Studies 2
W hat is “Geotherm al”? NOT HOT ROCKS!!!! NOT POWER PRODUCTION 3
W hat is “Geotherm al”? G round S ource H eat P umps (GSHPs) Low temperature thermal exchange (~40-90°F) Uses renewable energy stored in the earth to heat and cool 4
How Does I t W ork? Furnace and AC replaced by GSHP 5
W hy Geotherm al? Green Technology Zero Net Energy Carbon Reduction Save $$$ Lower LEED Maintenance Energy Efficiency 6
W hy Geotherm al? Heating Cost Comparison Fuel Unit of Efficiency of Price per Fuel Type Fuel Unit Cost Measure Heating Unit Million Btu Coal 330 Ton 75% 16.98 No. 2 Fuel Oil 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% 40.56 243.86 Wood Pellets Ton 80% 18.47 Kerosene 3.968 Gallon 80% 36.74 Geothermal 0.13706 kWh 330% 12.17 Note: Fuel Unit Costs are based on average prices in the State of New Hampshire as of September 3, 2012. To do your own comparison based on current fuel prices, your system’s efficiency, etc., go to: www.nhclimateaudit.org/calculators.php 7
W hy Geotherm al? Mean earth temperature CONSISTENTLY ~55°F 8
W hy Geotherm al? 100 90 Summer Δ =20°F 80 High Air Room Temperature Temperature Temperature, °F 70 Δ =15°F 60 50 Δ =-50°F 40 Mean Earth Temperature 30 20 Winter Low Air 10 Temperature 0 9
Energy Efficiency Earth Coupling Heating and Cooling (3 to 5 kW) (4 to 6 kW) Grid (1 kW) 10
Geotherm al Operation – SUMMER GEOEXCHANGE SYSTEM (REJECTS HEAT BTUs) Heat is Absorbed by Soil/Rock from Fluid 11 Earth = HEAT SINK
Geotherm al Operation – W I NTER GEOEXCHANGE SYSTEM (EXTRACTS BTUs) Heat is Absorbed by Fluid from Soil /Rock 12 Earth = HEAT SOURCE
Single Building District system graphic Supply and Return Headers Vault/manifold Wells drilled and connected in circuits 13
District System Serves multiple buildings District system graphic Vault/manifold Central Well Field 14
Hybrid System • Economic and/or design decision to optimize performance and limit capital costs • Combine geothermal wells and heat pumps 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 15
Hybrid System Load Profile 1800 1600 1400 1200 Load (MBh) 1000 Max Heating (MBh) Max Cooling 800 (MBh) 600 400 200 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 16
Distribution System s ( Building Side) Geothermal Heat Pump • Transfers heat from the ground loop to water or air distributed to the building Media: – Water-to-water (hydronic systems) – Water-to-air Distribution System • Ducted forced air system • Hydronic/Chilled Beams • Radiant floor (hydronic) heating with ducted cooling 17
Ground Heat Exchanger ( Ground Loop) Exchanges heat with the ground – Open to Diffusion Wells (ODW) – Standing Column Wells (SCW) – Closed Loops (CL) • Vertical • Horizontal Also - Pond Loops • Direct • Indirect 18
Open Loop System • Direct use of groundwater • Typ. <200 feet deep • Typ. used in highly transmissive aquifers (Cape Cod, Long Island) • More efficient • Aquifer characteristics important (flow/temp/chemistry) • More stringent permitting to Extraction Injection reinject water Well Well • More maintenance than closed loops (water quality can cause fouling) 19
Open Loop System Available depth to water for injection Ratio of injection wells Available drawdown to extraction for extraction wells may be 2:1 to 4:1 20
Standing Colum n W ell • Combine extraction and injection well • Typically 1,500 feet deep • In-well pump • Efficiency comes from 20’ (min.) into rock advective heat transfer • Performance is dependent upon quality of water encountered and ability to bleed Typ. 6.5 in. diam. in rock, uncased (Credit: Water Energy) 21
W hat is “Bleed?” Drywell, water body 10 gpm 90 gpm 100 gpm Issues: Induces Flow to Well Responsibly discharged to same aquifer Subject to permitting requirements Environmental Concerns? Foundation Settlement? 22
Deviation Most projects require 0.01 ft/ft = 15 ft Then there’s reality…… 210 feet away from point of entry! 23
Deviation 210 feet from point of entry at 294° Stabilizers and low down pressure used to limit deviation. 24
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….. 25
Closed Loop Vertical W ells • Closed pipe loop • Indirect heat exchange with ground • Typ. 300 - 500 feet deep • Ground temperature, thermal conductivity and diffusivity important • Lower maintenance than open systems 26
Closed Loop Vertical W ells 1.25-inch HDPE pipe Soil / Rock Thermally enhanced grout Factory fused U-bend 27
Closed Loop - Horizontal Slinky Advantages • Lower Installation Cost Disadvantages • Lower Thermal Capacity • Significant Site Disruptio n 28
Closed Loop – Vertical Slinky Advantages • Less Site Disruption • Lower Cost Disadvantages • Suitable Soils Needed • Thermally Inefficient • Long Lengths Needed 29
Lake/ Pond Loop Advantages • High Efficiency • Low Installation Cost • Easy to Install/Repair Disadvantages • Limited Application • Primarily for cooling • Regulatory Issues • Environmental Impacts 30
Selection of Ground Loop Logistics Permitting Recommended Ground Loop Risk Tolerance (O&M, Cost) 31
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? 32
Selection of Ground Loop Permitting requirements More rigorous for open systems Client’s risk tolerance Permitting O&M / Cost (Estimated payback period) Water quality issues - Poor water quality (i.e. high Fe, Mn or hard water, low pH) – CL recommended to avoid scaling and fouling issues (Risk tolerance is often primary factor in selection) 33
Perm it Considerations - NH NHDES State UIC registration ( U nderground I njection C ontrol) More rigorous permitting for Open Loop vs. Closed Loop UIC registration for CL Open systems (Open, SCW): UIC registration Water Use Registration and Reporting for > 20,000 gpd (~14 gpm) – report monthly use on a quarterly basis Groundwater Withdrawal Program (>57,600 gpd = 40 gpm) needs large groundwater withdrawal permit 34
Perm it Considerations – NH ( Continued) Open Loop For Commercial/Industrial/Institutional Residential is Exempt Raw Water Quality Testing Required for VOCs Primary inorganics (As, nitrate/nitrite) Radiological (Gross Alpha/Beta, Radium, Uranium) Secondary inorganics (Na, Cl, Fe, Mn) pH, temperature, TDS Bacteria (total coliform [fecal and E. coli]) for discharge water If bleed used – must return to same aquifer 35
Perm it Considerations – NH ( Continued) Closed Loop Allowed antifreeze (DRAFT) Propylene glycol Ethanol Also Methanol, Potassium Acetate, Calcium Magnesium Acetate (CMA) Pipe Materials HDPE Fiberglass Grout: Bentonite slurry, Bentonite and sand, Cement & Sand 36
Perm it Considerations -MA MassDEP State UIC registration ( U nderground I njection C ontrol) More rigorous permitting for Open Loop vs. Closed Loop 1 page UIC registration for CL Open systems – UIC registration, water withdrawal reporting/registration/permitting for > 100,000 gpd (=70 gpm), [determination of non-consumptive use] 37
Perm it Considerations – MA ( Continued) Open Loop Raw Water Quality Testing Required Selected Organics Primary inorganics (As, nitrate/nitrite) Radiological (Gross Alpha/Beta, Radium, Uranium) Secondary inorganics (Na, Cl, Fe, Mn) pH Bacteria (total coliform [fecal and E. coli]) for discharge water Bleed – should return to same aquifer If > 5% to different aquifer, requires justification 38
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