Q: What is a geothermal heat pump?
A: A geothermal heat pump is an electrically-powered device that uses the natural heat storage ability of the earth (or the earth’s groundwater) to heat and cool your residence or business.
Q: How does it Work?
A: A heat pump simply moves heat energy from one place to another. You’re probably more familiar with the process than you might think. Refrigerators and air conditioners are heat pumps. They move heat from colder interior spaces to warmer exterior spaces for cooling purposes. A geothermal heat pump operates on the same principle to cool your home. By reversing this process, a geothermal heat pump moves the heat energy stored in the earth and transfers it into your home.
Q: How is heat transferred between the earth and home?
A: The earth absorbs and stores heat energy from the sun. To use that stored energy, heat is extracted from the earth through a liquid medium (ground-water or antifreeze solution), pumped to the heat pump and used to heat your home. In summer the process is reversed and indoor heat is extracted from your home and transferred to the earth through the same liquid medium.
Q: What is a closed-loop system?
A: The term "closed-loop" is used to describe a geothermal system that uses a continuous loop of special buried pipe as a heat exchanger. The pipe is connected to the indoor geothermal heat pump to form a sealed, underground loop through which a liquid medium is circulated. Unlike an open-loop system that consumes water from a well, a closed-loop system recirculates its heat-transferring solution in pressurized pipe.
Q: How is a loop system put into the ground?
A: Most closed-loops are trenched horizontally in the yard adjacent to the home. Trenches are normally four to six feet deep and up to 400 feet long. Open and vertical loop systems typically utilize holes bored into the ground. As a rule of thumb, 500-600 feet of pipe are required per ton of geothermal system capacity. For example, a well-insulated 2,000 sq. ft. home would require a three-ton system with 1,500-1,800 feet of pipe.
Q: How long will the loop pipe last?
A: Properly installed, high strength plastic pipes will last 25-75 years. They are inert to chemicals normally found in soil and have good heat conducting properties. PVC pipe should not be used under any circumstances.
Q: If the loop falls below freezing, will it hurt the system?
A: No. The antifreeze solution in the loop will keep it from freezing down to about 10 degrees F. Three types of antifreeze solutions are acceptable in the US and Canad A: propylene glycol, calcium chloride and methyl alcohol.
Q: What do I do with the discharge water?
A: There are a number of ways to dispose of water after it has passed through the geothermal heat pump. The open discharge method is the easiest and least expensive. Open discharge simply involves releasing the water into a stream, river, lake, pond, ditch or drainage tile which as the capacity to accept the amount of water used by the geothermal system. A second means of water discharge is the return well. A return well is a second well bore that returns the water to the ground aquifer. A return well must have enough capacity to dispose of the water passed through the system. A new return well should be installed by a qualified well driller. Likewise, a professional should test the capacity of an existing well before it is used as a return.
Q: How much groundwater does an open-loop system need?
A: This varies by geothermal unit manufacturer, and is listed in terms of gallons per minute (gpm) in the specifications of each model. Generally, the average system will use four to six gpm when in operation. An extremely cold day could result in the use of 6,000 to 10,000 gallons of water.
Q: Can a geothermal system also heat water for my home?
A: Yes, by utilizing what’s called a desuperheater. Some types of geothermal systems channel excess heat energy created to preheat tank water. Some homeowners have reported savings of up to 50 percent on their water heating costs.
Q: Can a geothermal system be added to my fossil fuel furnace?
A: Yes, a geothermal system can easily be added to existing furnaces to create a dual-fuel heating system. Dual-fuel systems use the geothermal heat pump as the main heating source and a fossil fuel furnace as a supplement in extremely cold weather when additional heat is needed.
Q: How efficient is a geothermal system?
A: More than three times as efficient as the most efficient fossil fuel furnace. Instead of burning a fuel to produce heat, the system simply moves heat that already exists. By doing that, it provides three units of energy for every one unit used to power the system.