Low to moderate temperature geothermal water reservoirs of 68°F to 302°F (20°C to 150°C) provide direct heat for residential, industrial and commercial uses. Instead of heating the water so that it stays stored, they heat it very quickly in a copper section of less than 8 feet. Long, wrapped around the gas heat exchanger. Electrical units use solid-state TRIAC output switches that operate at high temperatures.
Water must be heated from a ground temperature of 50° F to at least 120° F, which represents an increase of 70° F in less than 8 feet. This rapid heating removes the air dissolved in the water and deposits all the minerals dissolved in the water inside the copper. Over time (sometimes as little as months), coating these minerals decreases the heat transfer efficiency of hot flue gases to water and, as a result, the temperature of the exhaust flue gas increases, wasting the energy that was intended to heat the water. While many parts of the country experience extreme seasonal temperatures, from scorching heat in summer to freezing cold in winter a few meters below the Earth's surface, the soil remains at a relatively constant temperature.
Depending on the latitude, ground temperatures range from 45° F (7° C) to 75° F (21° C). Like in a cave, the temperature of the ground is warmer than the air above it during the winter and cooler than the air in summer. The GHP takes advantage of these more favorable temperatures to be highly efficient in exchanging heat with the earth through a terrestrial heat exchanger. Geothermal technology harnesses Earth's heat.
Just a few meters below the surface, the Earth maintains an almost constant temperature, in contrast to the summer and winter extremes of ambient air above ground. Further below the surface, the temperature rises at an average rate of approximately 1°F for every 70 feet of depth. In some regions, tectonic and volcanic activity can cause higher temperatures and pockets of superheated water and steam to come much closer to the surface. Hybrid systems that use several different geothermal resources or a combination of a geothermal resource with outdoor air (that is, with today's state-of-the-art geothermal equipment, more than 80% of heating and cooling energy can come from the earth in a responsible manner).
The attached specification sheet is for a part of Climate Master 1991 geothermal heating and cooling equipment. The heat pump circulates a heat-carrying fluid, sometimes water, through pipes to move heat from one point to another. This hot steam passes through the tubes of the secondary heat exchanger installed in the duct network, which functions as a condenser that gives off heat as the vapor condenses back into liquid. Geothermal systems cost less to operate than electric heat pumps, oil, kerosene, natural gas and propane.
While the price of installing a geothermal system may be several times greater than that of an air supply system with the same heating and cooling capacity, the additional costs can return in energy savings over 5 to 10 years, depending on the cost of energy and incentives available in your area. In commercial buildings, geothermal air conditioning systems produce twice as much energy savings, first in much lower heating and cooling costs and then in a drastic reduction in electricity demand costs. Most closed-loop geothermal heat pumps circulate an antifreeze solution through a closed circuit, usually made of high-density plastic tubing, that is buried in the ground or submerged in water. Dual-source heat pumps have higher efficiency rates than air source units, but they are not as efficient as geothermal units.
An average geothermal system in the Northeast would operate from 2000 to 2,600 hours for heating and 400 to 500 hours for cooling, with an annual total of 2,400 to 3,100 hours. .