Heating buildings with direct use geothermal energy systems requires that sites are located in areas that have ready access to underground supplies of heated water. In Colorado, geothermal waters tend to be in the mountains and on the Western Slope. There are no identified areas on the Eastern Plains.
The underground heated water is used like a regular hot water heater, but this source comes preheated from within the earth and does not require additional heating. Geothermally-heated waters can also be used for hot springs, pools, spas, and greenhouses.
Water temperatures ranging from 65oF to 175oF are best for successfully heating buildings with geothermal energy. The water is typically brought to the surface by the use of a well. The water itself is used to heat the building; a heat exchanger is not usually a part of this system. The water is used like a hot water heating system with radiators or a radiant floor system. Ideally, the cooled water is returned to the ground through an injection well but may also be stored in a pond. Colorado’s Division of Water Resources determines whether the water must be re-injected or can be disposed of at the surface.
In municipalities that have significant geothermal resources, heating districts may be formed. In those cases, water is typically pumped from the ground, sent through a processing facility, and then used to heat another liquid to provide direct heat to buildings. Heating districts can benefit from economies of scale that individual businesses or homes could not. District geothermal heating systems can save between 30 and 50% on heating costs compared to natural gas systems.
Geothermal waters can be used to generate electricity. The waters used for electricity generation are normally at high temperatures around 300oF. However as technology improves, the temperatures needed are lower. There are four different methods used to generate electricity from geothermal resources – flash power plants, dry steam plants, binary plants, and flash/binary combined plants.
Flash power plants operate by separating the geothermal waters into steam and hot water. As the waters emerge from the ground, they are under pressure. The water “flashes” as it reaches the surface, producing steam along with the hot water. The hot water, or “brine”, is re-injected back into the geothermal reservoir. The steam is utilized to operate a turbine that generates the electricity.
A dry steam plant utilizes steam to run the turbines to produce the power. The wells are dry wells that only produce steam. No hot water or brine is produced by the well so no re-injection is required. Yellowstone National Park is an area where this technology can be used.
A binary power plant is a newer method of electricity generation and uses geothermal water that is lower than 300oF. These power plants use the hot water to heat another liquid. In a heat exchanger, the water transfers its heat to a liquid such as isobutene, pentafluoropropane, or other organic fluid that boils at a lower temperature than water. The liquids never come in contact with each other. The vapor formed from the other liquid is then used to power the turbine that generates the electricity.
A flash/binary system utilizes both the flash of the water and the steam of the binary system. The initial steam production is used to run turbines. The hot water is then used in a binary system, transferring its heat to the organic fluid. Again, the organic fluid boils at a lower temperature and produces vapors that operate a turbine.
Ground Source Heat Pumps
Ground source heat pumps utilize the relatively constant temperature of the earth as a heat source in cold months and as a heat sink in warm months. They consist of an electric heat pump and a water pump in a building as well as underground plastic tubing. The water pump circulates water (or an antifreeze solution) through the underground tubing, where it collects or dumps heat. This liquid gets further heated or cooled by the heat pump and, if necessary, a backup heating or cooling system. The liquid can then be used to condition air blown through ducts or as a heat source for radiant floor systems.
Source: U.S. Department of Energy
Ground source heat pumps can have underground piping that is laid out in horizontal fashion, typically 4-6 feet or more underground. They can also have piping laid out vertically, reaching depths of 100-400 feet.
No financial incentives are available at the current time. However, some electric utilities may offer incentives for the installation of a ground source heat pump.
Federal Tax Credits for Home Energy
A ground source heat pump may be right for you if:
- You wish to both heat and cool your building
- You have enough land area for a horizontal system or are willing to pay more for a vertical system
- Your land area for the loop isn’t rocky
- You currently use expensive fuels like electricity or propane to heat your building
- You have access to an experienced installer with a proven track record of success
- You are prepared to pay significantly more for a GSHP than a conventional heating and cooling system in order to recoup operating costs over time
Last updated: May 3, 2017 at 10:48 am