As the name implies, a geothermal heat pump is the combination of a heat pump with the Earth’s natural warming ability. Heat pumps already have a sterling reputation for high efficiency. With this enhancement, their ability to provide cheap, clean home heating expands even further. To get an idea of how they accomplish this, here’s the basics about this system of heating.
The most basic component of this system is the heat pump itself. These pumps usually run on electricity and provide warmth in a manner similar to the way air conditioning or a freezer generates cold air. In fact, it can be thought of as an air conditioner in reverse. A casual observation of the heat coming from the exhaust-end of an air conditioner will confirm this. While the natural tendency is for heat to move from a hotter to a colder object, a heat pump uses a compressor to transfer heat towards the warmth of indoors.
A Basic Run-through
A heat pump starts by pressurizing a refrigerant with a compressor. This raises its temperature and vaporizes it. This gas flows to an indoor condenser where a fan transfers its heat to the surrounding air. In the process, the gas loses heat and condenses. This cooled liquid is then sent through a metering valve that causes a pressure drop. When this happens, the liquid refrigerant cools even further until its temperature is lower than the outdoor air. As a result, it’s able to absorb additional units of heat from the exterior environment as it passes through the evaporator.
Just as an example, air at 0°F contains 85% of the thermal energy of air at 70°F. With this input of heat, the refrigerant switches back into a gas and flows back to the compressor to repeat the cycle. There are limitations to this system, though. If the exterior air is too cold, the working fluid can’t cool low enough to absorb enough warmth from it. Fortunately, there’s a way around this.
Heat From Below
Depending on the particular type, a heat pump starts to have difficulty efficiently drawing heat from the exterior at around 0°F. On the other hand, soil temperature a few feet down remains moderate all year. A geothermal heat pump takes advantage of this fact. These systems are divided into either open-loop or closed-loop systems.
An open-loop arrangement uses groundwater to supply the heat. The groundwater is pumped up and directly passes across the evaporator. It’s then discharged to a pond, stream, or back into the ground. A closed-loop operation uses pipes placed in the ground to circulate either the heat pump’s own refrigerant or a separate fluid to gather heat. Geothermal systems avoid both the loss of efficiency on very cold days and the problem of frost build-up on the exterior evaporator.
By pulling heat from the ground instead of producing their own, geothermal heat pumps provide cheaper heating than any other method, even natural gas. They also have the ability to save even more money when they’re installed as an all-in-one system that also provides hot water and air conditioning. Remember, a heat pump is essentially a freezer in reverse. Some pumps are designed to be reversible to handle both winter heating and summer cooling with no extra equipment.