Overview of Geothermal Technologies

Transcription

1 Overview of Geothermal Technologies Richard Desrosiers, LEP, P.G. GZA GeoEnvironmental, Inc.

2 Introduction to Geothermal Presented to: Environmental Business Council Presented by: of New England Richard J. Desrosiers, PG, LEP GZA GeoEnvironmental, Inc. Date: April 11,

3 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 3

4 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 4

5 Geothermal Hot Rocks 5

6 Earth s Heat Source 6

7 Geothermal Power Plant Geothermal Power Plant 7

8 Geothermal System 8

9 Favorable Geothermal Zone 9

10 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 10

11 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) 11

12 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 12

13 Typical Geothermal Layout 13

14 How Does It Work? Source: GeoExchange Website ( 14

15 Elements of a Geo-exchange System Taken from J. Lund, Geothermal (Ground-source) Heat Pumps, Presented at IIE, Cuernavaca, México,

16 Elements of a Heat Pump System Heating Cycle Cooling Cycle Taken from J. Lund, Geothermal (Ground-source) Heat Pumps, Presented at IIE, Cuernavaca, México,

17 Geothermal SUMMER GEOEXCHANGE SYSTEM CONCENTRATES/ CIRCULATES HEAT (BTUs) Heat is Exchanged from liquid To Soil/Rock Earth = HEAT SINK 17

18 Geothermal WINTER GEOEXCHANGE SYSTEM CONCENTRATES/ CIRCULATES HEAT (BTUs) Heat is Exchanged to liquid from Soil /Rock Earth = HEAT SOURCE 18

19 Type: Closed Loop System Depths typically 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 feet per ton A "vertical" loop of a ground-based, or an open-loop ground-source heat pump. (Credit: WaterFurnace International) 19

20 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 permittingregulations More maintenance-pumps potential for fouling/scaling More efficient than closedloop (less wells) A "vertical" loop of a ground-based, or an open-loop ground-source heat pump. (Credit: WaterFurnace International) Rules of Thumb feet per ton gpm per ton 20

21 Type: Standing Column Well 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 O Neill 21

22 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) 22

23 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 23

24 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 24

25 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 Legal Team Geo-Science/ Geo-Designer Architects/ Engineers Client - (Owner) commissioning agent No hidden agendas not tied to any one method or technology construction manager 25

26 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 26

27 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 27

28 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) 28

29 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 29

30 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) 30

31 Test Well Installation Closed-Loop 31

32 Test Well Installation Installation of Geo-loop Test Well Preparing the well for grouting 32

33 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- o F); Thermal diffusivity (measures of how quickly temperature recovers in ft 2 /day); and Formation temperature o F. 33

34 Thermal Conductivity Test 34

35 Typical Test Well Result 35

36 Thermal Conductivity Values Formation Type Thermal Conductivity (Btu/hr ft F) Clays Sand Sand & Gravel Granite Limestone Sandstone Shale Oklahoma State Test Results Rock Type: Thermal Conductivity: Thermal Diffusivity: Formation Temperature: Schist/gneiss 1.81 Btu/hr-ft-F 1.16 sq-ft/day 53.5-F 36

37 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 37

38 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 38

39 Construction Photo Manifold 3,200 Ton System 39

40 Construction Photo 40

41 Why Consider Geothermal Cost to Deliver 1 MBtu 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 $ Natural Gas $1.50/therm $ % $4.07 Air Source Heat Pump $0.15/kWh $ % $10.26 Propane $2.75/gal $ % $21.49 Fuel Oil $4.00/gal $ % $23.99 Electrical $0.15/kWh $ % $32.24 $50.00 $45.00 $40.00 $35.00 $30.00 $25.00 $20.00 $15.00 $10.00 $5.00 $0.00 Ground Source Heat Pump Natural Gas Air Source Heat Pump Propane Fuel Oil Electrical Ref: Heat Spring Magazine

42 Oil and Propane Cost in Dollars per Gallon Electrical Costs in Cents per kwh Changes in Utility Costs 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 Oil Propane Gas Electric Electrical costs CT Department of Public Utility Control Oil and Propane costs Policy Development and Planning Division CT Energy Management 42

43 Cash Flow (Dollars $) Conventional Roof Top HVAC Units vs Ground Source Heat Pump 9,000,000 8,000,000 7,000,000 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000, Year Life Cycle Conventional Roof Top Ground Source Heat Pump 43

44 Cash Cumulative Flow (Dollars Cost in $) Dollars Conventional Roof Top vs Ground Source Heat Pump 25,000,000 25,000,000 20,000,000 Conventional Roof Top Unit Top vs Ground Ground Source Heat Source Pump Heat Pump 20,000,000 15,000,000 15,000,000 10,000,000 10,000,000 5,000,000 5,000, Year 7 8Life 9Cycle Year Life Cycle 44

45 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 45

46 Geothermal Case Study Campus Setting 46

47 Campus Study 47

48 Energy Usages No. Bldgs Structure Type Area (sq. ft.) Heating & Cooling Energy Sources Energy Source (%) Central Independent 1 Plant 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% 53 Undergraduate & Graduate 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. 48

49 Geothermal Boreholes and Distribution Network 49

50 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 50

51 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 ( (NC State) 51

52 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. 52

53 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; 53

54 GZA Contact Information Old Faithful Geyser Richard Desrosiers