Association for Efficient Environmental Energy Systems

P.O. Box 598 Davis, CA 95617 2001 Second St., Suite 5, Davis, CA 95616

(530) 750‑0135 Fax: (530) 750‑0137 Email: info@aeees.org

 

Why Geoexchange Heating & Air Conditioning 

1. Geoexchange systems not only save energy (kWh's) year round, they also shave peak loads (about 0.5 kW per ton of cooling), as compared to conventional central air conditioning including air source heat pumps. 

2.    Since geoexchange systems utilize the constant ground temperature of the earth (approximately 57-67 deg F), they are sized for the building load only. Central air conditioning including air source heat pump systems are sized for the building load plus the additional capacity required to compensate for the loss of efficiency/capacity as a result of high outdoor ambient temperatures (which can easily reach 130 deg F+ on many roofs). The degradation caused by outdoor weathering of conventional systems also reduces the operating load for cooling on residential, commercial and school buildings. The energy and demand savings gained by using a geoexchange systems will range from 10 to 30 %, in addition to the peak load savings of approximately 0.5 kW per ton of cooling depending on the type of facility and its location. 

3. Geoexchange systems keep on saving energy and shaving peak loads year after year, which is not true for conventional central air conditioning or air source heat pumps. Per a study commissioned by the California Energy Commission in the 1980's, it is clear that there is a hidden efficiency loss associated with conventional central air conditioning including air source heat pumps. The study shows that because of air coil contamination and weathering, the standard plate fin coil equipment looses 27% efficiency over the first eighteen months after installation. Thus, a 10‑ton air source system with a 10 EER efficiency rating quickly becomes a 7.5‑ton system with a 7.5 EER. Geoexchange systems do not have this problem because the equipment is installed inside a building with no fin or plate coils exposed to outside weather conditions, so they continue to deliver their original 14 to 22 EER year after year.

4. Geoexchange systems also reduce the "Heat Island Effect" that is plaguing most urban areas. Conventional central air conditioning, including air source heat pumps, significantly raises the ambient outdoor temperatures in urban areas as they exhaust heat directly into the air. This effect not only increases the cooling loads within buildings; it also reduces the capacity and efficiency of the air source equipment, requiring, even larger capacity equipment to handle the increased loads. The only way to stop this rapidly increasing upward spiral is to stop using central air or air source heat pump equipment in these areas. Since geoexchange systems dump heat directly into the earth through the polyethylene loops buried in the ground, they do not increase the amount of heat into the atmosphere. 

5. Geoexchange systems can facilitate voluntary commercial load shaving. Since commercial geoexchange systems are normally designed using many small heat pumps (or two‑speed and twin compressor models) to serve individual building zones, it is easy for the facility managers to shut down (or reduce load by 50%) non‑critical zones while allowing critical zones to operate normally. 

6. Geoexchange saves natural gas resources. Geoexchange heating (space and/or water) requires only 4 kWh (13,600 BTU) to produce l6kWh (54,000 BTU) for space or water heating. In comparison, it takes 60,000 BTU's of natural gas to produce 54,000 BTU (assuming a 90% AFUE furnace) of space heating, or 90,000 BTU's of natural gas to produce 54,000 BTU of water heating. Geoexchange installations appear to be the only way to cut natural gas consumption, since it would be virtually impossible to have residential gas blackouts. As an added bonus, each ton of Geoexchange equipment installed will cut carbon emissions by one metric ton annually. 

7.   A peer‑review study by the Oakridge National Laboratory, published in 1981, based on the actual selling prices of 1317 homes, found an increase in market value of the house of $20 for every dollar of utility bill savings per year. The EPA estimates that a $35/month, $420/year savings would add about $8,400 to the market value of an average‑sized home. 

8.   Thus money spent on high efficiency conventional central air conditioning including air source heat pumps does not provide an effective payback, whereas money spent on geoexchange systems will payback consistently throughout their 20+ year life expectancy.

 

Association for Efficient Environmental Energy Systems

         Western Geothermal Heat Pump Resource Center

P.O. Box 598, Davis, CA 95617

       2001 Second Street, Suite 5    Email: geahp@concentric.

    Phone: (530) 750‑0135 Fax: (530) 750‑0137

 

A BETTER WA Y TO HEAT AND COOL A HOME OR B US17VESS 

So, you have heard about geoexchange (geothermal heat pump: GHP) systems, and you are considering one for a new business or home or possibly for a retrofit of an existing home. You cannot make a better choice. "GeoExchange" systems provide the best system efficiency while affording the highest level of comfort possible. A GeoExchange system will cost more to install than a conventional furnace and air conditioning system because it requires the installation of a ground loop (heat exchanger). However, this extra cost is far less than purchasing fuel every month for the next five to fifteen years (i.e. natural gas, propane, fire wood, electricity for resistance heating, or air source heat pumps). A GeoExchange system can also satisfy most of the domestic hot water needs with additional savings. They operate on electricity, but GHP systems use less than one‑third the electrical energy of a conventional air‑conditioning and heating system. 

A geothermal heat pump system should not be confused with the older, less efficient airsource heat pump. A GHP system uses the constant temperature of the earth which in California, depending where you are, ranges between 55 to 73 deg F.  For example, the large temperature difference an air source heat pump sees when operating in air temperatures at the extreme ends of the temperature scale, i.e. 30 deg F or 105 deg F, requires far more energy to accomplish the same results than a GHP system using the earth's temperature of 57 to 70 deg. F. 

A GeoExchange system can be installed in a new home or business by including the construction cost in the mortgage. For a retrofit of an existing home, a GHP should be purchased when the existing furnace and air conditioner need to be replaced. Both the furnace and air conditioner will be replaced by one GHP unit, which almost always can be installed in the same space which was occupied by the heating unit, therefore, eliminating the space needed for an air conditioner.  The cost of a heat pump is approximately the same as both a heater and air conditioner, however, there is an additional cost for the installation of the ground loop. A more specific accounting of these costs is given below. 

Under no circumstances should you consent to having a GeoExchange system installed  without the assurance that the system is designed using accurate heat loss and heat gain data.    The heating and cooling air duct system should be designed properly and be in good order.  The building should be adequately insulated, and a ventilation system that will allow a continuous infusion of fresh air should be part of the system. An adequately prepared structure can always reduce the tonage size of the GHP unit to be installed and the length of the ground loop by   approximately 20%.  In retrofitting a building for a GHP, generally, enough money can be saved   in reducing the heat pump unit capacity and the ground loop length to pay for the building shell retrofit work. In addition, an adequately sized heat pump used to heat and cool a building that has been weatherized will cost 20 to 30% less to operate during its working life. 

Before getting into a discussion on how to finance your GHP system, it should be made clear that costs should be a secondary decision to physical comfort when investing in a GHP system In fact, cooling and heating with a heat pump includes enough advantages to outweigh the extra cost of the ground loop. A partial list of the advantages follows. 

Quiet Operation

Heat pumps are usually installed inside the house or building, and they are noted for being very quiet. Great strides have been taken in recent years by manufacturers to lessen noise. One of the most successful devices for GHP's is the use of the scroll compressor which does not use a reciprocating piston; thus, it is far quieter and more reliable. Also, there is no noisy air condenser unit located just outside your window or on the roof. 

Health and Safety

Since there is no combustion involved with the operation of a GHP system, there are no carbon monoxide or carbon dioxide fumes produced within a structure or errant propane fumes that could be inadvertently ignited by a random spark. Therefore, there is never a worry about carbon monoxide poisoning or explosion and fire. 

Maintenance of Proper Humidity

Gas fired systems (usually oversized) cycle through a periodic series of ignitions followed by an infusion of hot air throughout the building that periodically raises the temperature of a building as much as 5 degrees to 10 degrees F higher than the temperature set on the thermostat.  This periodic infusion of heat without outside ventilation has a tendency to dry the air in a building structure making it physically uncomfortable for the inhabitants. 

Any system, conventional or GHP, should be designed to provide adequate ventilation and to maintain a proper level of humidity. GeoExchange systems, with their almost consistent low air flow, help to maintain a constant level of heat and humidity. 

Inherent Comfort

As mentioned above, conventional systems can cause fluctuation in a building's temperature by 5 to 1 10 deg. F above or below the temperature set on the thermostat, causing residents to feel too cool or too hot because of the lack of a continuous low flow of heated or cooled air.  GHP systems have run‑cycles that are longer but do not exhibit the strong flow of air that is characteristic of a conventional heating system. By running longer at a more even flow, GeoExchange systems can maintain a near constant temperature in a dwelling which is noticeable and enjoyable to residents and visitors alike, especially to those who are temperature sensitive. 

Efficiency

Because GBP systems draw their heat from the earth, the owner does not have to purchase natural gas, propane, fire wood, electricity for electric resistance heating, or fuel oil. Although geothermal heat pumps operate on electricity, the use of electricity can be 30% less than that used by an air conditioner and 70% less than that used by resistance electric heaters. Most GHP systems have coefficient of performance (COP) ratios of 3.5 or better.  A COP of 3.5 means that for every one unit of energy bought and put into the process, 3.5units of energy are produced leaving a net of 2.5 units at no cost. This reduction is possible because the ground loop provides heat energy from the earth.  In the cooling mode, heat is drawn from the building and deposited back into the ground. 

Durability and Reliability

The durability of refrigeration systems are legendary, and heat pumps easily match this level of performance. Owners of geothermal heat pump systems commonly refer to this longevity when asked about their system. This reliability of more than twenty years is due to many factors. The two most important factors are: (1) the small difference in temperature that they work against and (2) the fact that the equipment is housed inside rather than out in the harsh elements. The ground loop is usually guaranteed for up to fifty‑five years and has a life expectancy of more than 100 years. 

Affordability

If a new home or industrial facility is being constructed, the cost of the installation of the ground loop can be easily included in the building mortgage. The cost of the geothermal heat pump equipment is approximately the same as the conventional heater and air conditioner equipment which it replaces.  The cost for a vertical ground loop is approximately $900.00 to $1,500.00 per ton.

For example, a 2,000 sq. ft. house would require about 2.5 tons of heating and cooling for a total ground loop cost of approximately $3,750.00, which is minimal when compared to the overall construction cost. However, this cost will easily be offset the first time that the air source condenser has to be replaced, usually within ten to fifteen years depending on the type of system and location. Of course, the cost to install ground loops vary with the kind of soil and rock being drilled. If a horizontal loop system is installed, the cost will be $75.00 to $150.00 less per ton because only a backhoe is needed, not a drilling rig. 

If a structure is to be retrofitted and the heater and air conditioner need replacing, it is recommended that they are replaced by a GHP system. If this is the case, the only extra item that will have to be purchased is the ground loop.  The most important thing to remember is that the ground loop cost represents a fraction of what would be paid for conventional energy fuel for the next twenty to thirty years.  During its lifetime, a GHP system will not only cost you less to operate but will literally pay you back in fuel savings. There is no other air conditioning system that can make this claim! 

No Need for Air Conditioning

In higher altitudes and colder climates there is a common remark from all who are approached to install a GHP, which is, "We have no need for air conditioning because our summers are so mild, and the temperature never gets above 85 deg. F." This may be true. However, almost everyone who installs a ground source heat pump in a cold climate finds that they run the unit on the cooling mode far more than they expected. By operating the unit on the cooling cycle, owners find that they can eliminate the entry of dust and pollen (important to allergy sufferers) as well as insects into the dwelling while maintaining the building at an average comfortable temperature level. Presently, there is a common trend in new up‑scale homes to use a lot of glass and vaulted ceilings on the sunny side of the building which cause indoor temperatures to rise above tolerable levels in the summer. When vaulted ceilings and glass are used, a GHP can maintain the inside temperature at a comfortable level. 

Aesthetics and Outside Units. GHP's are almost always installed inside in the building. There are no units on the roof or roof penetrations, and there are no outdoor units. This translates into a sleek building profile with no unsightly boxes. This feature was used advantageously in the restoration of a two-story public house in Colonial Williamsburg, Virginia, where the object was to air condition the Colonial building without any visible heating and cooling equipment. 

Finally, all of the heat exchange loops and headers, which are installed adjacent to the structure, are located below ground, usually about five to six feet deep if the loops are installed horizontally or if in vertical bore holes from 100 to 400 feet deep. Ground loops may be placed under driveways, parking lots, lawns, parkways, or patios where they will remain totally obscure throughout their life time. Also, there is no worry that the polyethylene loop pipe will need repair if it has been installed properly by a professionally trained GHP contractor/installer. 

Low Maintenance. Just like any other air‑conditioning system, a geothermal heat pump requires occasional replacement of the air filter. Unlike other systems, however, geothermal heat pumps generally do not require ongoing mechanical maintenance, such as tuning up, cleaning of burners or recharging refrigerant.  This translates into greater reliability, the persistence of higher performance levels, and lower maintenance costs for owners. 

This information provides a better appreciation of just what GBP's can do in the way of comfort and efficiency for heating and cooling. There is nothing complicated about GHP's, and they will always perform as expected when the system is designed and installed correctly by a professionally trained heat pump contractor/installer.  You owe it to customers to suggest a GHP system when you are asked to build or retrofit a home or business. 

Association for Efficient Environmental Energy Systems (AEEES), with its Western Geothermal Heat Pump Resource Center, is a non-profit, educational association located in Davis, California, dedicated to encourage the installation of geothermal heat pumps through training of system designers and installers, educating the general public, and working with governmental regulators to solve problems before they occur.  AEEES has a full array of publications and videos for those who are interested in this technology. We can be reached at (530) 750-0135, fax (530) 750-0137, or Email at geahp@concentric.net