overview of geothermal technologies - cloud object...

Richard Desrosiers, LEP, P.G.

GZA GeoEnvironmental, Inc.

Overview of Geothermal Technologies

2

Introduction to Geothermal

Presented to:

Environmental Business Council

of New England

Presented by:

Richard J. Desrosiers, PG, LEP

GZA GeoEnvironmental, Inc.

Date: April 11, 2012

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

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”

5

Geothermal Hot Rocks

http://www.bing.com/images/search?q=deep+geothermal+sources+&FORM=IGRE&qpvt=deep+geothermal+sources+#

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Earth’s Heat Source


7

Geothermal Power Plant


Geothermal Power Plant

8

Geothermal System


9

Favorable Geothermal Zone


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

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)

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

13

Typical Geothermal Layout

14

How Does It Work?

Source: GeoExchange Website (www.geoexchange.org)

15

Taken from J. Lund, “Geothermal (Ground-source) Heat Pumps”,

Presented at IIE, Cuernavaca, México, 2007

Elements of a Geo-exchange System

16

Taken from J. Lund, “Geothermal (Ground-source) Heat Pumps”,

Presented at IIE, Cuernavaca, México, 2007

Elements of a Heat Pump System

Heating Cycle Cooling Cycle

17

Geothermal – SUMMER

Heat is

Exchanged

from liquid

To

Soil/Rock

Earth = HEAT SINK

GEOEXCHANGE SYSTEM

CONCENTRATES/ CIRCULATES HEAT

(BTUs)

18

Geothermal – WINTER

Heat is

Exchanged

to liquid

from

Soil /Rock

GEOEXCHANGE SYSTEM

CONCENTRATES/ CIRCULATES HEAT

(BTUs)

Earth = HEAT SOURCE

19

Type: Closed Loop System

A "vertical" loop of a ground-based, or an open-loop ground-source heat pump.

(Credit: WaterFurnace International)

Depths typically

300 - 500 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”

•150 - 200 feet per ton

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 permitting-

regulations

More maintenance-pumps

potential for fouling/scaling

More efficient than closed-

loop (less wells)


•30 – 100 feet per ton

•2.5 – 3 gpm per ton

A "vertical" loop of a ground-based, or an open-loop ground-source heat pump.

(Credit: WaterFurnace International)

21

Type: “Standing Column Well”

O’Neill

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


• 37.5 to 50 ft/ton with bleed

• 50 to 75 ft/ton w/o bleed

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)

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”

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

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

No hidden agendas – not tied to any one method or

technology

Client -

(Owner)

Architects/

Engineers

construction manager

commissioning

agent

Geo-Science/

Geo-Designer

Legal

Team

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

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

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)

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

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)

31

Test Well Installation Closed-Loop

32

Test Well Installation

Preparing the well for

grouting

Installation

of Geo-loop

Test Well

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- oF);

Thermal diffusivity (measures of how quickly

temperature recovers in ft2/day); and

Formation temperature oF.

34

Thermal Conductivity Test

35

Typical Test Well Result

36

Thermal Conductivity Values

Formation Type Thermal Conductivity (Btu/hr ft F)

Clays 0.3 – 1.1

Sand 0.5 – 1.2

Sand & Gravel 1.2 – 2.2

Granite 1.3 – 2.1

Limestone 1.4 – 2.2

Sandstone 1.2 – 2.0

Shale 0.6 – 1.4 Oklahoma State

Test Results

Rock Type: Schist/gneiss

Thermal Conductivity: 1.81 Btu/hr-ft-F

Thermal Diffusivity: 1.16 sq-ft/day

Formation Temperature: 53.5-F

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

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

39

Construction Photo

3,200 Ton System

Manifold

40

Construction Photo

41

Why Consider Geothermal Cost to Deliver 1 MBtu

Ref: Heat Spring Magazine 2012

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 $11.72 - - -

Natural Gas $1.50/therm $15.79 1.3 26% $4.07

Air Source Heat Pump $0.15/kWh $21.98 1.9 47% $10.26

Propane $2.75/gal $33.21 2.8 65% $21.49

Fuel Oil $4.00/gal $35.71 3 67% $23.99

Electrical $0.15/kWh $43.96 3.8 73% $32.24

$0.00

$5.00

$10.00

$15.00

$20.00

$25.00

$30.00

$35.00

$40.00

$45.00

$50.00

Ground SourceHeat Pump

Natural Gas Air Source HeatPump

Propane Fuel Oil Electrical

42

Changes in Utility Costs

0

5

10

15

20

25

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

9-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

Ele

ctr

ica

l C

os

ts i

n C

en

ts p

er

kW

h

Oil

a

nd

Pro

pa

ne

Co

st

in D

oll

ars

pe

r G

all

on

Oil Propane Gas Electric

Electrical costs – CT Department of Public Utility Control

Oil and Propane costs – Policy Development and Planning Division – CT Energy Management

43

Conventional Roof Top HVAC Units vs Ground Source Heat Pump

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

9,000,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Ca

sh

Flo

w (

Do

lla

rs $

)

20 -Year Life Cycle

Conventional Roof Top Ground Source Heat Pump

44

Conventional Roof Top vs Ground Source Heat Pump

0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Ca

sh

Flo

w (

Do

lla

rs $

)

20 Year Life Cycle

Conventional Roof Top vs Ground Source Heat Pump

0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Cu

mu

lati

ve

Co

st

in D

oll

ars

20-Year Life Cycle

Conventional Roof Top Unit Ground Source Heat Pump

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

46

Geothermal Case Study Campus Setting

47

Campus Study

48

Energy Usages

No.

Bldgs Structure Type

Area

(sq. ft.)

Heating & Cooling

Energy Sources

Energy Source (%)

Central

Plant Independent1

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.

49

Geothermal Boreholes and Distribution Network

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

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 (www.dsireusa.org) (NC State)

http://www.dsireusa.org/

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.

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;

54

GZA Contact Information

Richard Desrosiers

860-858-3130

[email protected]

Old Faithful Geyser

mailto:[email protected]

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