What Is A Geothermal Heat Pump? How A Heat Pump Works
What Is A Geothermal Heat Pump? How A Heat Pump Works
A geothermal heat pump (also known as a geoexchange or a ground source heat pump) is an electrically run central heating and cooling system that uses the constantly available heat energy beneath the earth’s surface, below the frost line, to provide heating and cooling for a building. While not suitable for all settings, a geothermal heat pump heating and cooling system is something home owners and building owners should consider to significantly save on heating and cooling costs. A geothermal heat pump heating and cooling system can save up to 75% of the cost of heating and 50% of the cost of cooling a building when compared to fossil fuel heating systems and central air cooling systems.
Geothermal Heat Pump Horizontal and Vertical Loop Configurations
How A Geothermal Heat Pump Works
A geothermal heat pump is the most efficient way to heat and cool a building, with some models approaching 400% efficiency in the heating mode. Meaning that for each unit of electricity utilized to operate the geothermal heat pump, four units of heat are provided to heat a building from heat extracted from the earth. In a roundabout way, geothermal heating is a form of solar energy. A few feet below the surface, the earth maintains a temperature between 45 and 70 degrees Fahrenheit throughout the year, even in the middle of winter. This subsurface heat is captured during the hot summer months, as the sun heats up the surface of the earth, and is transferred to lower levels of the subsurface where it is stored year-round.
A geothermal heat pump achieves high operating efficiencies by utilizing a highly efficient electric pump and piping system that circulates a mixture of water and anti-freeze through the earth to extract constantly available heat energy. Upon returning to a building structure, the warmed mixture of water and anti-freeze is then concentrated by the geothermal heat pump into heated air that is delivered through a duct system to heat a building. This is known as a closed loop geothermal heat pump heating and cooling system. Unfortunately, current geothermal heat pump technology only allows for forced air heat delivery, as the temperatures achieved are not hot enough to heat hot water for baseboard heating.
In the cooling mode, a geothermal heat pump system operates in reverse. The relatively constant temperature of the earth is used as a heat sink by the geothermal heat pump system, transferring heat from a building to the earth outside via the mixture of water and anti-freeze running through the piping system into the earth. The water and anti-freeze mixture that is returned to the building is significantly cooler than that which left the building, which is then used to provide cool air to the duct system to cool down the building.
Different Types of Geothermal Heat Pump Installations
There are variations on the design of geothermal heat pump systems, including closed systems that utilize a nearby body of water as a heat source and open loop systems that pump water from a well and then discharge the water after it is used to provide heat. In most applications, a closed loop system is used in a configuration in which the pipes are buried in the earth below the frost line either horizontally or vertically, wherever space is available on a property. If limited space is available and no nearby sufficient water body is available, a vertical closed loop system is the only option.
The Cost of a Geothermal Heat Pump Installation
A well insulated 2,000 square foot home would typically require a three or four ton geothermal heat pump system to provide adequate heating capacity. To determine the suitable geothermal heat pump system size for a particular building, a Manual J Heating / Cooling Load Calculation is utilized. This heating and cooling industry recognized standard takes into consideration such things at the amount of insulation present in a building, the size of the windows and their heat loss rating, and other factors in a building that cause heat loss. Since the cooling demands are much less than the heating demands, the size of a geothermal heat pump system is based on the heating needs. A ton of heating capacity requires approximately 400 feet of horizontal loop capacity or 300 feet of vertical loop capacity. A building that requires a three ton geothermal heat pump system will require 1,200 feet of horizontal loop capacity or 900 feet of vertical loop capacity.
Depending on the where a building is located and local labor and drilling or equipment costs, a typical three ton geothermal heat pump system could cost anywhere from $20,000 to $50,000 for everything needed for a geothermal heating and cooling system. The geothermal heat pump is approximately $5,000 to $10,000, depending on which model is selected. Most of the installation costs associated with installing a geothermal heat pump system are the labor and loop installation costs, with vertical loops typically costing more than horizontal loops, due to the cost of drilling deep boreholes for vertical loops. Another cost consideration is whether or not a house has the duct work necessary to deliver the forced hot air and cool air that a geothermal heat pump provides during the winter and summer seasons. If duct work is not already installed, the cost of such an installation could be significant. In buildings with existing duct work, the duct work may need to be upgraded, so the geothermal heating and cooling system operates at peak efficiency.
Cost Savings and Advantages When Using a Geothermal Heat Pump
The cost of a geothermal heat pump system installation is considerable. However, the installation costs can be reduced by tax credits that are offered by the federal government. These federal tax credits are for up to 30% of the total cost of a geothermal heat pump system installation (including duct work installation or modifications), which would bring down the cost of a $30,000 geothermal heat pump system installation to $21,000. Some state governments offer additional tax credits and subsidies that can be applied towards the cost of a geothermal heat pump system installation to bring the cost down even more.
Once a geothermal heat pump system has been installed and is functioning properly, the savings begin. First off, a geothermal heat pump system needs very little maintenance and produces no exhaust, so costs for annual system maintenance and chimney cleaning will not be incurred. On an ongoing basis, the annual savings for heating or cooling a building with a geothermal heat pump system are considerable.
Paul Wilkes of Garden State Geothermal has been installing geothermal heating and cooling systems for years in the New Jersey, New York, and Pennsylvania area. For a well insulated 2,000 square foot home with a three ton geothermal heating and cooling system in New Jersey, Paul said, “I would estimate your total heating and cooling cost to be somewhere in the $1,500 per year range. Heating is probably around $1,000 of that total cost, and that would be in electric.” That comes out to approximately $125 per month (averaged out over one year) for heating and cooling a 2,000 square foot home via a geothermal heating and cooling system. Heating the same home with heating oil and cooling it with a central air conditioner would cost approximately $230 per month over a one year period, assuming heating oil costs $3.50 per gallon. That is a savings of $1,260 per year on heating and cooling costs. This is how geothermal heating and cooling systems can save money on an ongoing basis.
Paul stressed that this is a rule of thumb estimate only. He further stated, “there is no accounting for life style use, and no two homes are alike in how much energy they use. Two of the same homes in different locations will use different amounts of energy to heat and cool.”
If a geothermal heat pump system costs $20,000 to install after federal and state tax credits and subsidies are figured into the cost, and the annual savings remain at $1,260 per year for heating and cooling costs, the system would pay for itself in 16 years. A long period of time, but worthwhile if one is going to remain in a building for a long period of time. If the cost of natural gas and heating oil were to rise significantly and electricity costs rose modestly, then the payback time would be accelerated accordingly. Having a geothermal heating and cooling system installed on a building also increases the value of the building, as prospective buyers are enticed by the low heating and cooling costs.
Declaring Energy Independence With a Geothermal Heat Pump System
If used in conjunction with a renewable electricity source, such as a solar or wind power generated electricity, a geothermal heat pump system can provide heating or cooling that is entirely free of the electrical grid and fossil fuel inputs. While such an installation would be quite expensive, the operational cost savings of using a combined renewable electricity system and a geothermal heat pump system would be significant. For those concerned about the environment and mankind’s use of fossil fuels, a fossil fuel free geothermal heating and cooling that runs on renewable electricity may be worth the up front investment.
Geothermal Heat Pump Operating In Summer and Winter Modes
- How Geothermal Energy Works
Geothermal energy is energy generated by geologic sources of heat and can be considered a form of renewable energy, when measured in the short term. It is based on the production of natural heat of the earth (geothermal) fed by the thermal...
- Maximizing Energy Efficiency Via Home Performance Wi...
Rather than focusing on a single energy wasting component within a home, Home Performance With ENERGY STAR™ takes a holistic approach to assess how improvements in several energy wasting components within a home can work together.
GeoExchange Heating and Cooling System
© 2011 John Coviello