Introduction to
Geothermal
Comfort Systems
Defining “Geothermal” Energy
• Dictionary definition
– Relating to the internal heat of the earth
• The Earth acts as a giant solar collector, absorbing
approximately 50% of the energy emitted by the Sun.
• Air temperatures may fluctuate as much as 50F above
and below the annual average. However, only a few feet
below the surface, the changes in earth temperatures
are much less severe.
Heat Pumps
• Heat pumps “move” energy from one location to
another, instead of creating heat by burning fossil fuels,
such as a gas furnace does. -- (like your refrigerator).
• Geothermal Heat Pumps use the earth or well water to
provide heating, cooling and hot water for your home.
• A geothermal heat pump “moves” energy to/from the
ground, eliminating the outdoor equipment associated
with ordinary heat pumps or air conditioners.
The Basic Ground Source Heat Pump
System
• The earth loop is placed in the ground either horizontally
or vertically, or it can be placed in a pond.
• Water and anti-freeze is circulated through the pipe,
transporting heat to the heat pump during the heating
mode and away from the heat pump during the cooling
mode.
• The heat transfer takes place inside the heat pump in a
water-to-refrigerant heat exchanger.
Energy Source
• During the heating season, the earth serves as a heat
source. (HE - Heat of extraction)
• During the cooling season, the earth serves as a heat
sink. (HR - Heat of rejection)
Heat Pump Operation
• Geothermal heat pumps consist of four circuits:
– Distribution circuit
• The system that distributes the conditioned air or
water solution throughout the home or building and
returns it to the unit.
– Refrigerant circuit
• A sealed and pressurized circuit of refrigerant
including compressor, expansion valve, water-torefrigerant heat exchanger(s), air coil, reversing
valve. The refrigerant is either R-22 or R-410A.
Heat Pump Operation
• Geothermal heat pumps consist of four
circuits:
– Ground loop circuit
• The piping system buried in the ground has fluid
that is circulated by pumps to and from the
geothermal unit.
– Hot water circuit
• Domestic water can be heated in a geothermal unit
with a device called a desuperheater. A piping
connection is made from the geothermal unit to the
water heater.
Heat Pump Operation
• Each of these circuits is closed and sealed from the
others—there is no direct mixing.
• However, heat energy does transfer from the
refrigeration circuit to the other three circuits.
• The refrigerant flow will change direction when the unit
changes modes (heating or cooling).
Heat Pump Operation
• The Four Circuits in a Geothermal Heat Pump
= Flow of Energy
(Heat)
Distribution Circuit
Refrigeration Circuit
Earth Loop Circuit
Hot Water Circuit
Heating Mode Operation
Cooling Mode Operation
The Basic Refrigeration Cycle
Compressor
Low Pressure
Vapor State
High Pressure
Vapor State
Evaporator
Condenser
Low Pressure
Liquid State
High Pressure
Liquid State
TXV
The Refrigeration Cycle
• Heating Mode Operation
The Refrigeration Cycle
• Cooling Mode Operation
Free Energy
• Geothermal Heat Pumps use only a small amount of
energy to capture a large amount of FREE energy from
the earth.
Equipment Performance Ratings
• ARI has designated the efficiency ratings for water-to-air
heat pumps as:
– Energy Efficiency Ratio (EER)
• EER = BTU output divided by power watt input
• For cooling operation under steady state test
conditions
– Coefficient of Performance (COP)
• COP = BTU output divided by BTU input
• For heating operation under steady state test
conditions
Geothermal Performance Comparison
Cooling Efficiency (EER)
30
25
New Geothermal Unit
20
Previous Geothermal Unit
15
High Efficiency AC or Heat
Pump
Ordinary
Air Conditioner or Heat
10
Pump
5
0
Geothermal Performance Comparison
Heating Efficiency (COP)
5.0
4.5
4.0
New Geothermal Unit
3.5
Previous Geothermal Unit
3.0
2.5
Heat Pump
2.0
High Efficiency Gas/Propane
Furnace
1.5
Ordinary Gas/Propane Furnace
1.0
0.5
0.0
Operating Cost Comparison

Annual Heating, Cooling & Hot Water costs
for typical 2,500 sq. ft. home, local weather,
local fuel rates (computer analysis results)




Geothermal
High Efficiency Nat. Gas & A.C.
Air Source Heat Pump
High Efficiency Propane & A.C
$ 780
$ 1,497
$ 1,608
$ 2,305
Return on Investment
(Due to Energy Savings)
• New Homes: Typically positive cash flow from “day
one”.
– Added cost in mortgage is offset by reduced
monthly operating cost.
• Existing Homes: Additional cost of geothermal
system is usually recovered in about 5 years.
Loop Types
• Closed Loop
– Horizontal
– Vertical
– Pond
• Open Loop
– Well Water
(w/ antifreeze)
Positive & Negatives
• Open well systems
+ can be cheaper initial install cost
+ constant supply of consistent btuh’s
- requires substantial water over life of system
- if well fails no heating or cooling
- not allowed in some local areas
Well Water
(Open Loop)
Uses
existing well
Requires 1.5 gpm/ton
Open Loop Systems
• Key Considerations
– Adequate water supply (5-9 gpm in addition to
household requirements)
– Good quality water (low mineral content)
– Adequate discharge location (drainage ditch, field tile,
pond, etc.)
Positive & Negatives
• Closed loop systems
+ low maintenance
+ typical one time install, long warranty on pipe
- higher up front installation cost
- variable supply of btuh’s so sizing is critical
- requires dedicated space for wells or trenches
Horizontal Loop
2- Pipe Horizontal
3 feet
5- 6 feet
2 feet
10 ft.
2 feet
Typically 3-4 trenches, 250 feet long each
4- Pipe Horizontal
3 feet
5- 6 feet
2 feet
10 ft.
2 feet
Typically 2 trenches, 180 feet long each
6- Pipe Horizontal
3 feet
5- 6 feet
2 feet
10 ft.
2-3 feet
1 foot
Typically 1 or 2 trenches, 120 feet long each
Horizontal 4 & 6 Pipe Loops
Slinky
5- 6 feet
10 ft.
2-3 feet
Typically 3 or 4 trenches, 100-150 feet long each
Horizontal Slinky Loops
Horizontal Bore Loops
Typically 3-4 bores, 200 feet long each
Vertical Loop
Side View
Vertical Loop
Typically 3 to 5 bore
holes, 130 feet deep
each
5- 6 feet
120 – 150 feet
10 – 15 feet
Vertical bore without backfill
Vertical Loop/Grouted
Geothermal pipe
Bentonite
Grout backfill
U-Bend
used for
Vertical
Loops
Vertical Loop
Drilling
Use drilling rig
like ones used
for water well
drilling.
Pond Loop
Minimum ½ acre,
8 ft. deep
Spacers allow
for more
circulation
around pipes
Top View
Side View
Typically 3 to 5 coils,
300 feet long each
Horizontal Pond/Lake Loops
Slim Jim Lake Plate Heat Exchanger
Racked Loops
Position, Fill & Submerge
Applications
Forced air heating and cooling
Supplemental water heating
Forced Air Zoned Systems
Dedicated water heating (radiant floor, snow melt,
domestic purposes, pools)
• Add-on splits to fossil fuel furnaces
•
•
•
•
Limitations
• Water-to-Air units:
•
Return Air temperatures
•
Adequate Ductwork
• Water-to-Water units:
Load-Side Flow
•
Load-Side Temperature
Limitations
• All units:
• Loop Considerations
•
Available Space
•
Installation Costs
Typical
Closed Loop
Equipment
and
Accessories
Typical
Installation
Water-to-Water Systems
• Homes with large hot water
demands, radiant floor heat,
snow melt and indoor pools
can be ideal for water-water
systems.
RFH with a Fan Coil Cooling System
W2W
Unit
Cornerstone Christian Academy
Bloomington, IL
51,000 Sq. Ft.
Annual Cost for Heating, Air
Conditioning, and Hot Water
Conventional System Geothermal System
$32,618
$8,519
Amber Ridge Assisted Living
Moline, IL
Conventional System
System
$15,199 / year
Geothermal
$6,592. / year
First Assisted Living Facility in US to
receive Energy Star rating
Martin-Kroenke Implement
Quincy, IL
29,225 Sq. Ft.
Annual Cost for Heating, Air
Conditioning, and Hot Water
Conventional System Geothermal System
$13,986
$3,581
Lincoln Towers Apartments
Bloomington, IL
60,000 Sq. Ft.
Annual Cost for Heating, Air
Conditioning, and Hot Water
Conventional System Geothermal System
$38,380
$12,737
Trinity Lutheran Church
Golden, IL
16,000 Sq. Ft.
Annual Cost for Heating, Air
Conditioning, and Hot Water
Conventional System Geothermal System
$12,926
$3,984
Marine Safety Station
Chicago, IL
Conventional System
$9,650. / yr
Geothermal System
$3,827. / yr
Wheaton Christian Grammar School
Wheaton, IL
86,320 Sq. Ft.
Annual Cost for Heating, Air
Conditioning, and Hot Water
Conventional System Geothermal System
$67,020
$33,340
Geothermal
• Dubuque Co.
Courthouse
• Historics
30% Tax Credit
• The Energy Credit
• In October 2008, geothermal heat pumps were added to
section 25D of the Internal Revenue Code. This created
• a 30% tax credit for costs associated with qualified
geothermal equipment.
- 30% of total system cost
- No limit to credit amount for 2009 and beyond
- Can be used in more than one year
- Can be combined with solar and wind tax
credits
- Can be combined with energy efficiency
upgrade credits
What’s Eligible
• Geothermal equipment that uses the stored solar energy
from the ground for heating and cooling, and that meets
Energy Star requirements at the time of installation is
eligible for the tax credit.
• Covered expenditures include labor for onsite
preparation, assembly, or original system installation and
for piping or wiring to connect a system to the home.
• The structure must be located in the United States and
used as a residence by the taxpayer, although primary
residency isn’t required. In fact, if geothermal is installed in
more than one home, there’s no limitation on the number
of times the credit can be claimed
Questions?
Geothermal Heating & Cooling…
“Smarter from the Ground Up”