Geothermal
The Basic Details – How it Works
The “geo” part of the geothermal system is the ground loop. The system uses the constant temperatures found under the earth's surface to provide basic heating and cooling. The loop consists of tubing (polyethylene or copper) which is usually filled with water or a mixture of water and anti-freeze.
A scientific fact that heat energy readily flows to cooler areas is the basis for all geothermal systems. The heat from the sun warms the earth in the winter and that stored energy is then used to heat the home. In summer, the earth becomes a “sink” where the the inside air's heat is discharged.
The only energy required for this part of the system after the loop's installation is the power the circulating pump uses to continuously move the fluid through the loop. As that fluid circulates underground, it absorbs heat and returns it to pass through the heat pump. The heat pump uses electricity to extract the heat from the fluid and then the re-chilled fluid is sent back through the ground to begin the process again. By switching the direction of the heat flow, that same system can circulate cooled water through a home.
If you think of the loop as the veins of the system, then the heat exchanger/heat pump is its heart. This is where the “thermal” part takes place. The earth has an ambient temperature of about 55 degrees, depending on where the system is installed. The geothermal heat pump is where the fluid that transfers heat to and from the earth is processed. A compressor in the unit increases the temperature to a level suitable for all but the coldest of days. On those days a secondary source of energy boosts the temperature of the heated air or water before it circulates in the home.
During the winter, the loop fluid (which is cooler as it exits the exchanger) absorbs heat from the earth surrounding it. This heated fluid is pumped back to the heat exchanger where a “pipe-within-a-pipe” coil uses the absorbed energy to heat the fluid contained within the heat exchange unit. This heated fluid becomes a gas at much lower temperatures than water and is used to heat the air (or water if using a radiant system) that circulates to the home from the exchanger.
During the summer, the temperature below the surface of the earth is less than the air temperature. So, the warm air in the home is cycled through the exchanger where the heat is extracted by reversing the heating process. The fluid in the loop – now warmed – is pumped back through the ground loop where the absorbed heat is released into the cooler earth and the cool fluid is recycled back to the home to repeat the process.
A geothermal system can provide heating and cooling through the forced-air system ductwork you're likely familiar with. It can also be used to heat water for in-floor radiant systems and use surplus heat to provide supplemental residential hot water. Geothermal can be installed as a replacement system to a current fossil fuel system that uses forced air to heat and cool. It is an obvious choice for consideration in new construction where the system cost is amortized over the term of the mortgage.
Some of the factors that will influence a decision to invest in a geothermal system are energy savings from changing systems, rebates and subsidies from local, State and Federal government programs, projected system life cycles and your ability to negotiate the purchase. The recovery of investment can occur in as few as 6 or 7 years or as many as 12 years. A reputable dealer will be able to construct a computer model to help you analyze your personal recovery term.
Vertical Closed Loop System
In a vertical closed loop system, a configuration of several vertical holes are drilled to a depth of 100' to 250' [and sometimes more]. The number of holes required is usually related to the size of the system [tonage/BTU] being installed and the depth of hole that can be effectively dug. The depth of the hole is generally related to the composition and rockiness of the soils on the site.
The tubing is inserted into each hole in a U-shape and is then connected to a manifold which connects all of the "U"s and is then connected to the geothermal heat pump. Each hole is filled with a grout which is designed to enhance heat transfer and to protect the system and the environment. The entire installation is then filled with dirt, graded and finished. This type of system is generally used where there is a limited amount of land available. Installation costs are usually higher than the horizontal closed loop system but are said to be much more efficient because the piping is buried deeper in the ground. Graphic from Department of Energy [www.engerysavers.gov].
Horizontal Closed Loop System
In a horizontal closed loop system, trenches or an open pit are opened to a depth of 6 feet and the tubing is laid horizontally as opposed to vertically. In some cases, the tubing is layered in the trench at one foot intervals. This configuration does not require drilling but does require more land to execute due to the size of the pits or trenches required to execute it.
The horizontal loop many also be installed using horizontal directional drilling [HDD] systems to insert the tubing underneath driveways, landscaping and structures without disturbing them. This form of drilling increases the cost of instally a horizontal system but still is not normally as expensive as vertical drilling.
Another type of horizontal loop system is called a "slinky" loop. In this configuration the tubing is coiled overtop of itself like a slinky to increase the heat exchange. This method is not a highly recommended method to install tubing. [Editors Note: My guess is because the proximity of other tubes in the loop impact the absorption and discharge of heat between the tubing and the earth]. This system is used where they is not enough room to deploy a true horizontal loop field [the loops are usually 1/3 to 2/3 shorter than conventional horizontal loops] but where ease of installation and budget are important. Graphic from Department of Energy [www.energysavers.gov].
Diagonal Closed Loop
A diagonal closed loop is very similar to the vertical loop, except instead of drilling the holes down vertically, they are arrayed out to form a cone shape in the ground. This option achieves the efficiency of the vertical loop system while reducing the costs involved in a traditionally-arrayed vertical system.
In this installation a central point - appromimately 6' x 6' - is excavated and all the bore holes radiate from this section on a diagonal axis [30 degrees +/-]. This allows the maximum number of bore holes with the least amount of surface disruption. The manifold is then used to connect all of the tubes and is them connected to the heat pump. It is a great choice for a retrofit installation because a smaller surface area is affected with this method.
Closed Loop Pond System
A closed loop pond system is installed just as it says – in a closed loop configuration along the bottom of a pond. This system requires a pond of sufficient depth to achieve the heat exchange and functions similarly to a ground loop system. The tubing is laid in a "slinky" configuration on the bottom of the pond, just as it would be in a horizontal loop installation. As you may know, even if the surface of a pond freezes in winter, the water even 5' or 6' below the surface is warm enough to allow fish to live. Conversely, in summer, the water lower in the pond is cooler than water near the surface. The closed loop pond system is sometimes used where poor water quality precludes the use of an open pond system. Because this system is closed, nothing is transferred into the water so pollution is not a consideration. Graphic from Department of Energy [www.energysavers.gov]
Open Loop System
An additional system is the open loop system which uses a well to exchange and discharge the water in the system. This last type is not as widely used as other loop systems because not 
that many people have wells these days. Among various concerns is the quality of the water in the well. Mineral deposits in the water can have a deleterious effect on the inner workings of the exchanger. Great care must be exercised in testing the well water to see if this option is available. The up-side of this method is that almost no drilling or excavation is required and less tubing is used than in the closed systems.
Open Loop Well System - use ground water from wells or ponds to provide the exchanged medium for the heat pump. The heat exchanger inside the heat pump adds or extracts heat to or from the water which is then discharged back into a suitable cistern or other body of water.
In a single well application, the divergent heights of the intake [lowest] and exhaust [highest] tubes prevent the dilution - heating or cooling - of the source water by the discharge. In a dual well installation [shown in photo], one well is the intake and the other the exhaust, thereby eliminating the possibility of dilution of the source well. In both cases, the cost of drilling and encasing the well may cause this method to be cost-prohibitive.
Open Loop Pond System - may be a better solution and, in fact, may well provide the answer to the cost of an open loop well system. The same mechanics apply, keeping the intake and exhast ends of the tubes far apart.
In every open loop system, a primary concern will be the quality of the water available. Limescale and corrosion cuased by minerals, salts and iron in the water may cause a reduction in the efficiency of the system and will require an acid-cleaning maintenance regimen to protect the system. If this condition is pervasive, a closed loop system may be the best selection. Graphic from Department of Energy [www.energysavers.gov]
More Than You May Want To Know
In order to understand the systems we're evaluating, these are some of the terms you'll want to be familiar with. These are commonly used performance and efficiency terminology used in connection with cooling and heating systems. Become familiar with them so you can have significant conversations with the folks designing your new home and/or bidding on your HVAC system. The information below is a brief introduction to these terms.
EER - Energy Efficient Ratio. EER is the measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level (usually 95°F). It is defined as the ratio of net cooling capacity (heat removed in Btu/h) to the total input rate of electric power applied in Watts. Room air conditioners in general range from 5,000 Btu per hour to 15,000 Btu per hour. Select room air conditioners with EER of at least 9.0 for mild climates. In a hot climates, select air conditioners with EER over 10. The higher the EER, the more efficient the system. (10,000 Btu/h divided by 120 watts = 8.33 EER)
SEER - Seasonal Energy Efficiency Ratio. SEER is a comparative measurement of cooling efficiency. Essentially, it is the rating of efficiency a unit delivers, by determining the amount of energy needed to produce overall btus of cooling capacity over the course of a cooling season. There are various ratios and formulas used to produce the rating. The critical thing you need to be aware of in regard to SEER Ratings, is that the higher the SEER Rating, the more efficient the unit, which results in lower energy costs for you.
Nugget - For purposes of comparison, the higher the SEER the more efficient the system. Although SEERs and EERs cannot be directly compared, the SEERs usually range from 0.5 to 1.0 higher than corresponding EERs.
kW/ton - this term is commonly used for larger commercial systems. It defines a ration between energy consumption and rate of heat removal at a specific condition. The lower the KW/ton, the more efficient the system.
COP - Coefficient of Performance. COP is the ratio of cooling or heating to energy consumption. A refrigerator with a COP of 2 moves 2 Watts of heat for every Watt of electricity consumed. An air conditioner with a COP of 4 moves 4 Watts of heat for every watt consumed. COP may also be used for domestic heating. An electric heater has a COP of 1. Each watt of power consumed produces 1 Watt of heat. Conventional heat pumps have COPs of 2 - 5, delivering 2 to 5 times the energy they consume.
Nugget – The higher the COP number, the greater the efficiency.
IPLV - Integrated Part-Load Value. The term IPLV is used to signify the cooling efficiency related to a typical (hypothetical) season rather than a single rated condition. The IPLV is calculated by determining the weighted average efficiency at part-load capacities specified by an accepted standard. It is also important to note that IPLVs are typically calculated using the same condensing temperature for each part-load condition and IPLVs do not include cycling or load/unload losses. The units of IPLV are not consistent in the literature; therefore, it is important to confirm which units are implied when the term IPLV is used. ASHRAE Standard 90.1 (using ARI reference standards) uses the term IPLV to report seasonal cooling efficiencies for both seasonal COPs (unitless) and seasonal EERs Btu/Wh, depending on the equipment capacity category; and most chillers manufacturers report seasonal efficiencies for large chillers as IPLV using units of kW/ton. Depending on how a cooling system loads and unloads (or cycles), the IPLV can be between 5 and 50% higher than the EER at the standard rated condition.
nc or Ec - Combustion Efficiency. For fuel-fired systems, this efficiency term is defined as the ratio of the fuel energy input minus the flue gas losses (dry flue gas, incomplete combustion and moisture formed by combustion of hydrogen) to the fuel energy input. In the U.S., fuel-fired efficiencies are reported based on the higher heating value of the fuel. Other countries report fuel-fired efficiencies based on the lower heating value of the fuel. The combustion efficiency is calculated by determining the fuel gas losses as a percent of fuel burned. [Ec = 1 - flue gas losses]
Thermal Efficiency (nt or Et). This efficiency term is generally defined as the ratio of the heat absorbed by the water (or the water and steam) to the heat value of the energy consumed. The combustion efficiency of a fuel-fired system will be higher than its thermal efficiency. See ASME Power Test Code 4.1 for more details on determining the thermal efficiency of boilers and other fuel-fired systems. In the U.S., fuel-fired efficiencies are typically reported based on the higher heating value of the fuel. Other countries typically report fuel-fired efficiencies based on the fuel′s lower heating value. The difference between a fuel′s higher heating value and its lower heating value is the latent energy contained in the water vapor (in the exhaust gas) which results when hydrogen (from the fuel) is burned. The efficiency of a system based on a fuel′s lower heating value can be 10 to 15% higher than its efficiency based on a fuel′s higher heating value.
HSPE - Heating Seasonal Performance Factor. The term HSPF is similar to the term SEER, except it is used to signify the seasonal heating efficiency of heat pumps. The HSPF is a weighted average efficiency over a range of outside air conditions following a specific standard test method. The term is generally applied to heat pump systems less than 60,000 Btu/h (rated cooling capacity.) The units of HSPF are Btu/w-h. It is important to note that this efficiency term typically includes the energy requirement of auxiliary systems such as the indoor and outdoor fans. For purposes of comparison, the higher the HSPF the more efficient the system.
|
Operating Mode |
Design Rated Conditions |
Seasonal Average Conditions |
|
Cooling |
COP |
COP |
|
Heating |
COP |
AFUE |
This information and Table were found in the http://www.engineeringtoolbox.com/cooling-heating-efficiency-d_410.html reference page.
Before we go any further, we want to suggest one more step to take before requesting bids. You wouldn't buy a dress or suit without knowing your size – why would this be any different? You're going to invest $15,000 to $20,000 in this system. If it's not large enough for the space, it will work too hard too long and wear out ahead of its useful life. If the system is too large for the space, it won't reach the system's optimum working range, wasting potential performance and costing you more than you needed to spend.
The measurement is called a “Manual J Calc” and uses a formula that includes window and door size and type, insulation ratings, fireplaces, square footage of surfaces, cubic footage of the overall space and orientation of the walls, doors and windows to provide a required rating for heating and cooling systems. Doing this will help you to be certain that the system you buy will provide the comfort and savings you seek.
Manufacturers offer geothermal heat pump systems rated from ½ ton to 6 tons or more. Some companies will suggest two separate units or that output from a single larger unit be split. They might suggest dual systems with separate thermostats. You need to pay attention to the details of locating, sealing and insulating the duct work. While most of you will not be seeking LEED certification (which this detail is a part of), it will help increase the efficiency of the system. Above all else, ask questions – you've heard this before – the only dumb question is the one you don't ask.
Finally, the Department of Energy has established efficiency ratings for all manner of systems and products. Below you'll find the link to their paper on geothermal heat pumps. There is a descriptive portion as well as charts for current and future system requirements.
DOE Geothermal Heat Pump Specifications
GEOTHERMAL MANUFACTURERS
This list contains two distinct classes of companies – ones that manufacture only the heat pump component of the system and those that manufacture the complete system. You'll notice that in some cases the company specializes in systems that work best in a particular climate zone. We've tried to provide you with basic information about the company's location, history, any unique characteristics of their systems, whether they offer complete systems or not and general contact information. You can click on the name of the manufacturer to go directly to their website.
Addison - Commercial & industrial manufacturer and supplier. The company offers packaged rooftop systems and heat pumps for geothermal applications. 7050 Overland Road – Orlando, Florida
Bard Manufacturing Company - Bard began manufacturing their own patented heating and cooling equipment in the 1930’s in Ohio. Today they have additional manufacturing facilities in Madison, Georgia and Saltillo, Mexico. Four generations later, they have kept up with current trends and technologies including the manufacture of their own geothermal heat pumps while continuing to offer a complete traditional line of systems for both commercial and residential applications. Over 90 years after their first product, they are still operating as a family-owned business. It is not clear from their website where they actually manufacture their products. 914 Randolph Drive – Bryan, OH - 419-636-1194 –
This e-mail address is being protected from spambots. You need JavaScript enabled to view it.
Bryant – Since 1904 Bryant has been making heating and cooling systems in factories across the United States. They offer a range of systems compatible with almost any existing installation. Their systems use the most up-to-date materials available in this environmentally-conscious age. Like other geothermal heat pump manufacturers, they offer horizontal and vertical units with both one-stage and two-stage compressors. The company's corporate headquarters are located in Indianapolis, Indiana and they have seven manufacutring facilities located in Indiana, New York, Texas, Tennessee and Arkansas. 7310 West Morris Street – Indianapolis, IN - 800-428-4326
Carrier -- This well-known company offers systems in both vertical and horizontal orientations. They are available for open and closed loop applications. Like many of the other manufacturers, Carrier systems support both water-to-air and water-to-water (radiant heat) installations. The company is a subsidiary of United Technologies and the are headquartered in Farmington, Connecticut, USA, with approximately 45,000 employees in 172 countries. Their geothermal heat pumps are manufactured in Tyler, Texas. 1 Carrier Place, Farmington, Connecticut - 800-227-7437
Climate Master -- ClimateMaster is “the world’s largest and most progressive manufacturer” of geothermal heat pumps. They provide units that are designed for both new construction and retrofit applications. ClimateMaster is a wholly-owned subsidiary of LSB Industries. The company's corporate headaquarters are located in Oklahoma City, OK and their manufacturing and warehouse facilities in Oklahoma City allow them to service the entire country effectively. In 2009, the company began adding 78,000 square feet of floor space to its 280,000-square-foot geothermal heat pump manufacturing plant and 40,000 square feet to its 250,000-square-foot heat transfer coil manufacturing plant in Oklahoma City. In addition to heat pumps, they also offer water-to-water systems that can provide radiant heating and hot water. 7300 SW 44th Street – Oklahoma City, Oklahoma - 405-745-6000.
Earth To Air Systems -- ETA offers systems that utilize copper tube for the loop portion of their systems. They are one of only two or three companies we are aware of in this industry employing that material in that application. Their units are certified for both American and Canadian installations. The company's corporate office is located iin Franklin, Tennessee but it is not clear from their website where their products are manufactured. 123 SE Parkway Court – Franklin, Tennessee.
EarthLinked Technologies -- Headquartered in Lakeland, FL, EarthLinked offers a complete system – from the ground-loop system comprised of copper tubes to the “direct exchange” unit and hot-water distribution systems. They are one of only a few companies that use copper tube for the loop construction. They also offer a diagonal field in addition to the horizontal and vertical loops that are standard with most other companies. The company's manufacturing facility is also located in Lakeland. The system applications included heating & cooling, hot water and swimming pool heating. 4151 S. Pipkin Road - Lakeland, FL – 863-701-7796.
ECONAR Energy Systems - Located in Minnesota, this company has focused on designing systems that perform well in colder climates for two decades. They offer a complete line of accessories including tubing that is specifically tailored for these types of climates. In addition to forced air systems, they also offer radiant systems for a variety of applications. They are a subsidiary of GeoSystems, LLC with coroporate offices located in Maple Grove, MN and their manufacturing facility is in Appleton, MN. 7550 Meridian Circle Suite 120 – Maple Grove, MN - 612-241-3110
ECR Industries Inc dba Advanced Geothermal Technology. This company manufactures The Great Aire Comfort System. This is a “direct exchange” system as opposed to systems that use water or other fluids in a “loop system” which is then processed through a scroll compressor. Advanced Geothermal claims that their system employs the least invasive installation procedure in the industry. There are several companies using “direct exchange” technologies. They are located in Reading, PA but their website does not state where they manufacture their systems. P.O. Box 6469 – Reading, PA - 610-736-0570
Florida Heat Pump – Florida Heat Pump is a subsidiary of Bosch Thermotechnology, Ltd. and was founded in 1970. They manufacture both geothermal and water source systems for both residential and commercial applications in their Fort Lauderdale, Florida facility. They are introducing new, high efficiency systems that actually target segments of their competitors' lines. 601 NW 65th Court – Ft. Lauderdale, FL – 954-776-547
GeoComfort -- This company, also known as Millbrook Industries – Hydronic Division, is a subsidiary of Enertech Manufacturing, LLC which also manufactures the Hydron Module and TETCO brands. The GeoComfort division is headquartered in Mitchell, South Dakota. Enertech is headquartered in Greenville, IL. They offer complete systems including ground loop components which are manufactured in Mitchell, SD. 2506 South Elm Street - Greenville, IL – 618-664-9010
GeoFurnace Manufacturing, Inc. - Michael Hunt is the founder of this company. He began in the GSHP industry in 1983. This company builds heat pumps designed for use primarily in colder climates as opposed to cooling dominant climates. They offer systems that range from 1 to 50 tons. 605 4th Street, SE – De Smet, SD – 605-854-9205
GeoMaster -- Manufactures private brand system as as well as GeoExcel in the United States. Their decision to manufacture units instead of installing someone else’s was driven by their vision to create a simple and reliable system. They offer vertical and horizontal units with 1 and 2 stage pump configurations. They are located in Fort Wayne, Indiana but do not state where the products are manufactured. 3512 Cavalier Drive – Fort Wayne, IN - 877-443-6411
Hydro Delta Corporation-- They manufacture the HydroHeat geothermal heat pumps, a brand of GeoSystems, LLC. Their HydroHeat Dual Fuel unit is patented, multipurpose heat exchanger designed by their engineers to transfer geothermal energy or fossil fuel energy to the conditioned space and allows the consumer to choose between geothermal energy or fossil fuel such as natural gas, propane, or fuel oil, as the primary or backup energy source.Their website is similar in content to ECONAR. They state that their headquarters are also located in Maple Grove, Minnesoto and that their manufacturing facility is in Appleton, Minnesota. 7550 Meridian Circle – Maple Grove, MN – 800-432-662
Hydro-Temp Corporation - Manufactures and offers a complete line of geothermal heat pumps for residential and commercial applications from ½ to 50 tons. They also offer pool heaters, radiant heating systems and air quality systems. Hydro-Temp’s sister company, Air-Flo Company, is a licensed mechanical contractor in Arkansas, Missouri, Tennessee, Mississippi and Alabama. The company is based in Pocahontas, Arkansas but the website does not mention anything on the location of their manufacturing facility. P.O. Box 566 -3636 Hwy 67 South – Pocahontas, AR - 870-892-8343
Mammoth, Inc. - This company has manufactured residential and commercial HVAC systems since 1935. They offer vertical and horizontal systems sized from ½ to 2,000 tons. The company's corporate office is located in Eden Prairie, Minnesota and they have manufacturing facilities in Springfield, Missouri and Holland, Michigan. They are affiliated with CES Group. 3200 Pioneer Trail – Eden Prairie, MN – 952-358-6600
Marvair – This company focuses on geothermal for schools. The company is a leading manufacturer of wall mounted packaged air conditioners and heat pumps. These units are designed and built for a variety of applications including: schools, telecommunications, and modular buildings. The company's headquarters and manufacturing facilities are located in Cordele, Georgia. 156 Seedling Drive – Cordele, Georgia - 229-273-3636
McQuay International - offers commercial, industrial and institutional HVAC systems. Since 1872, as a pioneer in the manufacture of the steam engine, McQuay international has delivered engineered solutions for industry's HVAC needs. They are part of Daiken Industries and is the second largest air conditioning, heating, ventilating and refrigeration company in the world. The company states that it has more than six million square feet of manufacturing facilities and 5,000 dedicated employees in 75 countries on six continents. They do have manufacturing facilities in Minnesota, New York and Virginia but it is not clear where their geothermal systems are manufactured. 13600 Industrial Park Blvd. - Minneapolis, MN - 765-553-5330
Northern Heat Pump - is a Canadian corporation purchased by Electro Industries of Monticello, Minnesota in 2009 to manufacture and sell a new redesigned geothermal and Electro electric heating and boiler product line throughout Canada . They offer residential and light commercial systems rated from 1.5 to 12 tons in water-to-air, water-to-water and combination systems with single and two-stage fans. They have both American and Canadian sales offices. Northern Heat Pump and Electro Industries is a family owned business located in Minnesoto but their website does not make it clear where their products are manufactured. 2150 West River Street – Monticello, MN - 800-922-4138.
Sunteq and Enviroteq – Sunteq was founded in 1978 as an HVAC contractor by G. Daniel Woodring, a chemical and mechanical researcher who was issued patents for inventions. Sunteq and Enviroteq are intertwined. Enviroteq manufactures the GEO series of geothermal heat pumps and other air handler components. Sunteq is the exclusive distributor for Enviroteq as well as other manufacturers system accessories. Their website states that they have been building many of their own units since 1989 but really do no state where the units are manufactured. Their website suggests a personal relationship with their customers after one phone call. 104 Neff Road – Howard, PA - 814-234-2127
Trane - This company is a subsidiary of Ingersol-Rand. They are currently providing systems to commercial users. 608-787-2835
WaterFurnace International - WaterFurnace is a leading manufacturer of residential, commercial, industrial and institutional geothermal and water source heat pumps. They claim to sell more residential geothermal heat pump systems than any other company in this industry. With a wide selection of all-in-one, split and hydronic systems in production, they are a – if not the – player in the industry. The company's corporate headquarters and manufacturing facility are in Fort Wayne, Indiana. 9000 Conservation Way – Fort Wayne, IN