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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 Distribution Circuit Flow of Energy (Heat) Refrigeration Circuit Earth Loop Circuit Hot Water Circuit
Heating Mode Operation
Cooling Mode Operation
The Basic Refrigeration Cycle Compress or 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 3.0 2.5 Previous Geothermal Unit 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 780 High Efficiency Nat. Gas & A.C. 1,497 Air Source Heat Pump 1,608 High Efficiency Propane & A.C 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
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
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
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
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
Geothermal Heating & Cooling “Smarter from the Ground Up”