Presented by: David G. Lamothe, P.E.

Transcription

1 Geothermal Heating/Cooling Systems Presented to: NH Joint Engineering Societies 6 th Annual Conference Presented by: David G. Lamothe, P.E. Senior Project Manager GZA GeoEnvironmental, Inc. Manchester, New Hampshire Date: October 4,

2 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

3 What is Geothermal? NOT HOT ROCKS!!!! NOT POWER PRODUCTION 3

4 What is Geothermal? Ground Source Heat Pumps (GSHPs) Low temperature thermal exchange (~40-90 F) Uses renewable energy stored in the earth to heat and cool 4

5 How Does It Work? Furnace and AC replaced by GSHP 5

6 Why Geothermal? Green Technology Zero Net Energy Carbon Reduction Save $$$ Lower Maintenance LEED Energy Efficiency 6

7 Why Geothermal? Fuel Type Heating Cost Comparison Fuel Unit Cost Fuel Unit of Measure Efficiency of Heating Unit Price per Million Btu Coal 330 Ton 75% No. 2 Fuel Oil Gallon 78% Natural Gas Therm 78% Propane Gallon 78% Wood 210 Cord 60% Electricity kwh 99% Wood Pellets Ton 80% Kerosene Gallon 80% Geothermal kwh 330% Note: Fuel Unit Costs are based on average prices in the State of New Hampshire as of September 3, To do your own comparison based on current fuel prices, your system s efficiency, etc., go to: 7

8 Why Geothermal? Mean earth temperature CONSISTENTLY ~55 F 8

9 Why Geothermal? 100 Temperature, F Room Temperature Δ=15 F Mean Earth Temperature Δ=20 F Δ=-50 F Summer High Air Temperature Winter Low Air Temperature 0 9

10 Energy Efficiency Earth Coupling (3 to 5 kw) Heating and Cooling (4 to 6 kw) Grid (1 kw) 10

11 Geothermal Operation SUMMER GEOEXCHANGE SYSTEM (REJECTS HEAT BTUs) Heat is Absorbed by Soil/Rock from Fluid Earth = HEAT SINK 11

12 Geothermal Operation WINTER GEOEXCHANGE SYSTEM (EXTRACTS BTUs) Heat is Absorbed by Fluid from Soil /Rock Earth = HEAT SOURCE 12

13 Single Building District system graphic Supply and Return Headers Vault/manifold Wells drilled and connected in circuits 13

14 District System Serves multiple buildings District system graphic Central Well Field Vault/manifold 14

15 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

16 Hybrid System 1800 Load Profile Load (MBh) Max Heating (MBh) Max Cooling (MBh) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 16

17 Distribution Systems (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

18 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

19 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) Extraction Well Injection Well More stringent permitting to reinject water More maintenance than closed loops (water quality can cause fouling) 19

20 Open Loop System Available depth to water for injection Available drawdown for extraction Ratio of injection wells to extraction wells may be 2:1 to 4:1 20

21 Standing Column Well Combine extraction and injection well Typically 1,500 feet deep In-well pump 20 (min.) into rock Efficiency comes from advective heat transfer Performance is dependent upon quality of water encountered and ability to bleed (Credit: Water Energy) Typ. 6.5 in. diam. in rock, uncased 21

22 What 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

23 Deviation Most projects require 0.01 ft/ft = 15 ft Then there s reality 210 feet away from point of entry! 23

24 Deviation 210 feet from point of entry at 294 Stabilizers and low down pressure used to limit deviation. 24

25 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

26 Closed Loop Vertical Wells Closed pipe loop Indirect heat exchange with ground Typ feet deep Ground temperature, thermal conductivity and diffusivity important Lower maintenance than open systems 26

27 Closed Loop Vertical Wells 1.25-inch HDPE pipe Soil / Rock Thermally enhanced grout Factory fused U-bend 27

28 Closed Loop - Horizontal Slinky Advantages Lower Installation Cost Disadvantages Lower Thermal Capacity Significant Site Disruption 28

29 Closed Loop Vertical Slinky Advantages Less Site Disruption Lower Cost Disadvantages Suitable Soils Needed Thermally Inefficient Long Lengths Needed 29

30 Lake/Pond Loop Advantages High Efficiency Low Installation Cost Easy to Install/Repair Disadvantages Limited Application Primarily for cooling Regulatory Issues Environmental Impacts 30

31 Selection of Ground Loop Logistics Permitting Risk Tolerance (O&M, Cost) Recommended Ground Loop 31

32 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

33 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

34 Permit Considerations - NH NHDES State UIC registration (Underground Injection Control) 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

35 Permit 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

36 Permit 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

37 Permit Considerations -MA MassDEP State UIC registration (Underground Injection Control) 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

38 Permit 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

39 Permit Considerations MA (Continued) Closed Loop Allowed antifreeze Propylene glycol Ethanol Pipe Materials HDPE Fiberglass Grout - Bentonite slurry or Bentonite and sand 39

40 Financial Incentives for Geothermal 20 to 40% heating/cooling energy savings Federal Tax Credits (sunset 2013 comm/2016 res) State Tax Credits in some states Utility Rebates Where to Start? Database of State Incentives for Renewables & Efficiency ( DSIRE,

41 Geothermal Payback Period Depends on the situation New construction? Replacing an old system? Condition of existing system? 7 to 15 years typical <7 years possible, particularly for older systems in need of replacement due to avoided costs Look at Life Cycle Costs (Capital, O&M) 41

42 Geothermal Team Geothermal Team Integration is Critical Professional Engineers/Geologists Certified Mechanical GeoDesigner Certified Driller/Installer Architect Mechanical/HVAC Engineers Construction Contractor Commissioning Agent Are LEED objectives being met? System operating instructions/debug No one should be tied to a certain method or technology 42

43 State of the Practice for Geothermal? Phase I - Feasibility Study Educate owners Due Diligence to evaluate anticipated conditions and recommend a ground loop type for the site GZA w/ Energy Modeler, System Designer input Recommend a ground loop type (SCW, CL, ODW) Test well Phase II - Design Plans and Specifications System Designer w/ GZA input Phase III - Well Field Construction Driller w/ GZA observation 43

44 State of the Practice for Geothermal? Phase I - Feasibility Study Educate owners Due Diligence to evaluate anticipated conditions and recommend a ground loop type for the site GZA w/ Energy Modeler, System Designer input Recommend a ground loop type (SCW, CL, ODW) Test well 44

45 Test Well Test well or first well of the geothermal well field for consideration in design of remaining well field Obtain site-specific geologic information (soil, depth to and type of rock, groundwater quantity and quality) Estimate thermal properties via thermal conductivity test (CL) Pump test and water quality testing (SCW or ODW) 45

46 Test Well Installation Standing Column Installation of Geo-loop Drill rig Auxiliary compressor/ support truck Booster compressor Two rolloff dumpsters Two open weir tanks and one frac tank Preparing the well for Mud rotary grouting with 12-inch stabilizer to 20 into rock, set 8 dia. casing 46

47 Test Well Installation Standing Column dia. mud rotary to 20 into rock 20 (min.) into rock 6.5 dia. air rotary to 1,500 ft. (Credit: Water Energy) Typ. 6.5 in. diam. in rock, uncased 47

48 Test Well Installation Closed Loop 6-inch mud rotary bit used to set temp./perm. casing into rock, then air rotary to bottom of hole Drilling 6-inch borehole 48

49 Test Well Installation Closed Loop Installation of Geo-loop Test Well Preparing the well for grouting 49

50 Thermal Conductivity Test Closed Loop 50

51 GZA and Geothermal 3-Phase Approach Phase I - Feasibility Study Due Diligence to evaluate anticipated conditions and recommend a ground loop type for the site GZA w/ Energy Modeler, System Designer input Recommend a ground loop type (SCW, CL, ODW) Test well Phase II - Design Plans and Specifications System Designer w/ GZA input Phase III - Well Field Construction Driller w/ GZA observation 51

52 Well Field Construction Observe: Well depth and construction Pressure Testing U-bends Circuits Supply and Return Well Field Circuit Piping Configuration 52

53 Well Field Construction 53

54 Well Field Construction 54

55 Well Field Construction Looping and grouting 55

56 Well Field Construction 56

57 Well Field Construction 57

58 Well Field Construction Vault construction and manifold 58

59 Well Field Construction Prefabricated Vault and Manifold Main supply and return stubs Circuit supply and return stubs 59

60 Well Field Construction Electrofusion Main supply and return lines 60

61 Case Studies and Cost Comparisons Total System Cost ($000) $3,000 Consider $2,500 $2,000 $1,500 Life-Cycle $1,000 $500 $- Costs! SCW Install CL Install Tons 235 Tons 113 Tons 140 Tons SCW (30 yr) CL (30 yr) year cost includes O&M, Monitoring and Reporting 61

62 New England Geothermal 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 To become part of NEGPA Information on NEGPA 62

63 Questions? David Lamothe, P.E., IGSHPA AI GZA Senior Project Manager