Comparatively, a geo-thermal verse's a conventional HVAC system; we can show a significant increase in efficiency using geo-thermal. Where by we consider the physical properties of heat saturation between air (conventional HVAC) and the ground (Geo-thermal). First we will discuss what an insulator is and why we use insulation in a home. Second, we will look at air and its properties as an insulator. Second we will look at Geo-thermal and the properties that make it the most logical choice.
The transfer of heat energy from one substance to another is related to thermo-dynamics. A basic law of thermo-dynamics is that energy or heat is always transferred from a greater to the lesser source. An insulator is a substance that absorbs energy and has a high threshold to releasing that same energy. So we can say an insulator has an extremely high threshold to thermo-dynamics. Like the insulation that lines the walls of your house. An insulator in this manner will absorb the heat energy from the outside and store that energy. The insulator releases that energy slowly to the inner walls of your home or back to the outside wall at night when the temperature decreases.
There are many different kinds of insulation fiberglass being the most recognized. What is not commonly known is a lot of insulation manufactures produce insulation with the ability to store a lot of air. Combined with the insulating property of there materials air boosts the thermo-dynamic threshold of the end product. A good example would be looking at a hot water heater. If we remove a portion of the metal skin we will find a hardened fiberglass mold. The mold is formed by a process called injection molding. Where the fiberglass is pumped in as a liquid with an air injection method. Allowing the most amount of air possible to be trapped in the fiberglass mold.
Air is a natural insulator meaning that a volume of air will absorb energy with a low property of transfer. My background in combustion in the boiler field has given me a tremendous amount of knowledge dealing with air. In combustion, excess amounts of air will inhibit the transfer of heat to the water in the boiler. New technologies in combustion controls have allowed the boiler industry to decrease the amount of excess air in the combustion process leading to upwards of 20-30% more efficiency. The efficiency translates to an increase in the thermo-dynamics of heat transfer to the water in the boiler.
Now we see that air is an insulator. Which industry either uses to enhance insulation or strives to reduce as much as possible to promote more efficient heat transfer. Like the combustion process, your conventional HVAC heat pump, uses the outside air to extract (make heat) or remove heat from the system. Conventional HVAC manufacturers can implement technologies to reduce the amount of energy it takes to run there heat pump, but can never improve on the air quality that there system is working.
A geo-thermal system utilizes a fluid, like the anti-freeze used in your car to remove heat from the engine, pumped through piping in the ground. The thermo-dynamic property of the fluid is low. Meaning the fluid will absorb or transfer heat easily. The ground stores heat energy and even in cooler climates at 10' in the ground a medium temperature of around 55 degrees is consistent. In summer time the temperature at this depth does not change much. Making a geothermal system more efficiently capable of releasing heat in the summer or extracting heat in the winter. The heat pump works considerably less or uses less electric energy to do its job.
A traditional HVAC system also uses a heat pump, which extracts heat from the surrounding air. The energy stored in the air is much harder to extract. Since many other factors, such as air density (barometric) and moisture content, are involved. Making your HVAC system less efficient in the winter and summer.