Geothermal Heating / Cooling Systems – Overview of Application in ...

Geothermal Heating / Cooling Systems – Overview of Application in New Hampshire David G. Lamothe Senior Project Manager GZA GeoEnvironmental, Inc.

Geothermal Heating/Cooling Systems – Overview of Application in New Hampshire

Presented To: EBC New Hampshire Chapter Program Renewable Thermal Energy in New Hampshire

January 8, 2013 David Lamothe, P.E., IGSHPA AI Senior Project Manager GZA GeoEnvironmental, Inc. Manchester, New Hampshire 603-232-8716 [email protected] 2

What is “Geothermal”?

Ground Source Heat Pumps (GSHPs) (not power generation) Low temperature thermal exchange (~40-90°F)

Uses renewable energy stored in the earth to heat and cool 3

Why Geothermal?

Mean earth temperature

CONSISTENTLY ~55°F 4

How Does It Work?

Furnace and AC replaced by GSHP

5

Energy Efficiency

Earth Coupling (3 to 5 kW)

Heating and Cooling (4 to 6 kW)

Grid (1 kW)

6

Geothermal Operation – SUMMER

GEOEXCHANGE SYSTEM (REJECTS HEAT BTUs) Heat is Absorbed by Soil/Rock from Fluid

Earth = HEAT SINK

7

Geothermal Operation – WINTER

GEOEXCHANGE SYSTEM (EXTRACTS BTUs) Heat is Absorbed by Fluid from Soil /Rock

Earth = HEAT SOURCE

8

Single Building

District system graphic Supply and Return Headers Vault/manifold

Wells drilled and connected in circuits 9

District System Serves multiple buildings

District system graphic Vault/manifold Central Well Field

10

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

11

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 12

Ground Heat Exchanger (Ground Loop)

Exchanges heat with the ground – Open to Diffusion Wells (ODW) – Standing Column Wells (SCW) SCW and CL – Closed Loops (CL) Vertical Wells • Vertical • Horizontal

Dominant Ground Loops in NH

Also - Pond Loops • Direct • Indirect 13

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 and quantity of water encountered and ability to bleed

(Credit: Water Energy)

Typ. 6.5 in. diam. in rock, uncased 14

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? 15

Closed Loop Vertical Wells •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

16

Closed Loop Vertical Wells 1.25-inch HDPE pipe

Soil / Rock

Thermally enhanced grout

Factory fused U-bend

17

Additional Loop Options

Open to Diffusion Wells (ODW) (extraction/reinjection wells)

Advantages Lower Horizontal Slinky Closed Loops Installation Cost Vertical Slinky Closed Loops

Surface Water: Closed or Open Systems Disadvantages • Lower Thermal Capacity • Significant Site Disruption 18

Selection of Ground Loop

Logistics

Permitting

Recommended Ground Loop Risk Tolerance (O&M, Cost)

19

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? 20

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)

21

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

22

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 23

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

24

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 / Rate Reductions  Renewable Energy Credits (RECs)  Where to Start?  Database of State Incentives for Renewables & Efficiency (“DSIRE”, www.dsireusa.org)  http://energy.gov/savings 25

Geothermal Payback Period

 Depends on the situation  New construction?  Replacing an old system?

 Condition of existing system?  7 to 15 years typical 