Do you, like many homeowners, desire to reduce your home’s heating and cooling costs while helping the environment? A geothermal heating and cooling system may suit your energy and climate requirements.
This article will discuss how geothermal systems operate smarter – not harder – than conventional HVAC systems to help you save money, energy, and the environment.
Given that 40 percent of all energy consumed and related greenhouse gas (GHG) emissions in the United States are attributable to buildings — particularly heating and cooling — geothermal energy should comprise a significant portion of the answer to our climate dilemma.
What Is Geothermal Heating In A Home?
The direct translation of geothermal from the Greek is “ground heat.”
A geothermal energy production is a form of renewable energy that includes extracting heat as steam or extremely hot water from at least one mile below the Earth’s surface. The heat in the form of steam drives a turbine that generates energy for large cities and towns.
In contrast, a domestic geothermal HVAC system, sometimes referred to as a geo-exchange, earth-coupled, or earth energy system, depends on the sun’s radiant energy that is absorbed and stored in the soil surrounding your home.
Geothermal energy may also be viewed as naturally stored solar energy that is available 24/7/365.
How Does Geothermal Energy Function For Residential Use?
The planet’s surface absorbs about fifty percent of the sun’s energy that reaches the Earth.
This figure demonstrates the distribution of the sun’s radiant energy to Earth and its atmosphere:
Below the frost line, the average annual temperature is between 48 and 52 degrees Fahrenheit. (This temperature range might be greater or lower in extreme heat or cold locations.) This fact is the foundation upon which geo-exchange HVAC is based.
The precise location of the frost line in your region is heavily dependent on your latitude, soil type(s), and climate. It may be a few inches to one hundred inches beneath the surface.
Knowing the location of the frost line is essential for DIY geothermal installations.
To provide access to constant-temperature heat, installers of geothermal systems bury their plumbing at least 4 to 6 feet below the surface. Some systems may reach depths of several hundred feet in some locations.
Water, water-antifreeze mixtures, or refrigerant travels through the pipes between the earth and your home. In water-antifreeze solutions, food-grade propylene glycol is frequently employed.
The liquids transport the earth’s heat into your home. There, the heat is transferred to the air in order to heat your home and maybe your domestic hot water.
During the summer, geothermal systems also collect heat from the air in your home and transmit it underground via liquid-carrying pipes.
Closed Versus Open-loop Geothermal Systems
All geothermal systems utilize a subsurface or submerged loop field to heat or cool a residence. The “loop” is typically composed of high-density polyethylene (HDPE) #2 plastic tubing. Occasionally, the pipes are composed of copper.
The “loop” may be circular, U-shaped, overlapping, helical, or stretched out as if fingers were extended.
The two primary types of geothermal loop fields are closed and open.
Geothermal Closed-loop Systems
The underground pipe of a closed-loop system is organized in a continuous loop. In it, the same heat-carrying and heat-dispersing liquid circulate continuously.
The closed-loop can be arranged in a variety of ways. Horizontally (like a racetrack or serpentine), vertically (in a succession of long U-shaped tunnels extremely deep below), and horizontally in a neighboring pond or lake.
Horizontal loops:
- Work most effectively when there is ample outside area.
- Cost less to install than vertical loops since no good drilling is required.
- Due to better accessibility, it requires less complex upkeep.
Vertical loops:
- Are the only option when space is restricted.
- Do not alter the landscape much.
- In the event of damage or leakage, you should demand expensive, comprehensive repairs.
Pond loops:
- Possible if you have easy access to a nearby body of water.
- The simplest form of loop to fix (no digging or excavating required).
- Eliminates excavation expenditures because they are unnecessary.
Geothermally Powered Open-loop Systems
In a system with an open loop, there is no continuous loop of tubing or pipes. Rather, heat is transferred from source groundwater or well water via pipework leading to a heat pump. Later, it is drained via an exit pipe, often at a different place such as a discharge pond or return well.
This process gives an open-loop geothermal system the term “pump and dump.”
Today, open-loop geo-exchange systems are less prevalent than closed systems. There are too many uncertainties surrounding the local water supply and quality for open-loop systems to be cost-effective or long-term viable.
For instance, mineral scaling on the condenser of a heat pump caused by hard water is prevalent, as are fouling concerns caused by biological pollution, which block the pipework and the pump.
Both of these issues harm and shorten the lifespan of geothermal heat pumps utilized in an open-loop system.
In addition, you will likely want additional licenses to build and run an open-loop system because of the possible consequences on the aquifer and the surrounding environment.
However, the fundamental principles governing heat transmission inside a geothermal heat pump are identical for both open and closed-loop systems.
How Does A Geothermal Heat Pump Work?
The geothermal heat pump, also known as a ground source heat pump (GSHP), is the essential component of all earth-coupled HVAC systems, connecting your home to the earth. It transports heat from the soil to your residence and back.
The pump uses the same mechanism as refrigerators, freezers, and air conditioners to do this. In each situation, the pump works against the natural inclination of heat flow, which is to travel from warm to cold.
A GSHP employs a cycle of vaporization and condensation that involves pressurizing and depressurizing a refrigerant in order for it to undergo the phase shift from liquid to vapor and back again.
In instances when the geo-exchange system utilizes circulating water or water-antifreeze mixes, there is a two-step heat transfer process in the pump, which is also known as a water-source geothermal heat pump. (The term “water” in the name of this type of pump refers to the water or water/antifreeze mixture inside the pipe, not to ground, surface, or domestic water.)
The liquid within the tubing absorbs heat from the earth or groundwater and transports it to the pump. In one of the heat exchangers of the pump, the heat is then transferred to the refrigerant, warming it. The temperature of the heated refrigerant in the compressor rises further when the pressure is increased. At some point, the refrigerant evaporates.
Then, the heated refrigerant vapor passes through a refrigerant-to-air heat exchanger, which removes the heat and distributes it throughout the home’s air ducts.
Once the heat is gone, the refrigerant reverts to a liquid, ready to repeat the cycle.
In the summer, the procedure is reversed. The refrigerant collects heat from the interior air as it passes through the air ducts and, ultimately, the heat pump. When the refrigerant flows through the heat exchanger, it transmits heat to the water or water-antifreeze combination.
The heat energy then exits the residence and enters the subsurface loop. There, the earth absorbs thermal energy.
Types Of Geothermal Heat Pumps For Home Heating And Cooling
Nearly all geothermal heat pumps on the market today employ a two-step heat transfer technique to transmit heat energy from the earth or groundwater into your home. The preceding section detailed their operation.
However, when homeowners choose copper pipes in a closed-loop geothermal system, refrigerant rather than water or water/antifreeze cycles through the pipes.
R410A for geothermal heat pumps
R410A, a kind of hydrofluorocarbon (HFC) that is a potent greenhouse gas, is the most widely used refrigerant today. Due to their role in climate change, international accords dictate that governments immediately begin phasing down HFCs. Ongoing research aims to identify more eco-friendly refrigerants.
Geothermal heat pump
The heat transfer from the soil to the refrigerant in a direct exchange geothermal heat pump — also known as a DX geo or direct expansion pump — is straightforward and direct. Copper’s strong conductivity is responsible for this property. Consequently, energy efficiency is even better than with two-step pump systems.
All geothermal heat pumps measure their capabilities in tonnes.
One tonne equals 12,000 BTU/hour or 3.5 kW.
A typical American residence requires three tonnes of heating and cooling capacity. To establish the ideal size for your home, you must first calculate the heat load.
Is Geothermal Energy Cost-effective?
The installation expenses for geo-exchange systems may be substantial, but the system will pay for itself in two to seven years through energy savings and improved efficiency.
Compared to air source heat pump systems, geothermal systems can cut energy usage by 25 to 50 percent, according to the Environmental Protection Agency. Geothermal heat pumps have a maximum efficiency of 600 percent. (In comparison, an oil furnace with an efficiency of 80 percent is considered good.)
Coefficient of performance (COP)
A ground source heat pump’s energy efficiency is quantified by its coefficient of performance (COP). A COP of 1 indicates complete efficiency.
A GSHP may effortlessly achieve a COP of 4 or 5.
Energy performance ratios (EER)
Energy efficiency ratios (EER) are another method for measuring the efficiency of a pump. Geothermal pumps are typically rated between 13 and 20. However, the maximum rating is 30.
The more efficient the COP and EER, the better.
Costs for geothermal home energy systems
Knowing how beneficial geothermal heating and cooling is in terms of energy savings and efficiency may reduce price shock.
A comprehensive system for a 2,000-square-foot home in the United States might cost between $20,000 and $30,000. In addition to energy savings, there are various methods to justify the hefty initial investment.
Today, a ground-source heat pump with a 3-ton capacity and an EER of 28.7 costs around $4,500. In the past decade, this value was $7,500.
Typically, pump warranties exceed 10 years. Their real-life expectancies are often at least twice as long. In addition, the subsurface pipe might survive over fifty years.
Tax credits and other incentives for geothermal
The attractiveness of a geothermal home HVAC system is enhanced by the substantial tax advantages and state rebates.
The federal tax credit was extended to 2023 at the end of 2020’s December. By 2022, it will remain at 26 percent before dropping to 22 percent in 2023.
Visit the Database of State Incentives for Renewables & Efficiency to discover other methods to minimize the overall cost of your geothermal energy system at home.
Environmental aspects of geothermal residential energy systems
An earth-coupled home energy system enables homeowners to reduce their carbon footprint without difficulty.
Oak Ridge National Laboratory (ORNL) showed in a case study review of six GSHP projects that geo-exchange systems decreased carbon emissions by up to 65%.
Another analysis by ORNL concluded that installing geothermal systems in all single-family residences in the United States would result in:
- 45 percent CO2 emissions decrease
- 48 percent energy savings and 56 percent summer peak electricity demand decrease
Where Are Geothermal Heating And Cooling Most Effective?
The good news is that geo-exchange systems operate effectively everywhere in the United States. Which method is appropriate for you depends on a number of criteria unique to your property:
- Geology
- Hydrology
- Geographic characteristics
Geological considerations
When building a geo-exchange energy system, the soil type, its moisture content, and the presence of subterranean rock must be taken into account.
Hydrological considerations
The height of the water table in your region has a direct bearing on the design of your geothermal system, particularly if you are considering a vertical loop system.
If you are considering installing a horizontal loop in a nearby pond, ensure that the water depth and volume remain stable throughout the year.
Land availability
Have you considered installing a horizontal geothermal system? Existing subsurface utilities that might interfere with the horizontal or vertical installation of a loop?
Consult with a geothermal specialist to build the optimal energy system to fulfill all of your demands and work with (rather than against) the property’s soil and water features.
How Do You Install A Geothermal Heat Pump?
Geothermal DIY is gaining popularity, while the majority of homeowners seek out a certified installer. The Geothermal Exchange Organization provides a state-by-state directory of geo specialists.
The most typical form of geo-exchange home energy system consists of plastic tubing through which a water/antifreeze combination flows.
The closed-loop system is located below near your residence. The actual heat pump is often installed in the basement or garage.
Horizontal system closed-loop characteristics.
Horizontal closed loops are installed in 400-foot-long, 4 to 6 feet deep to 10 feet-deep holes. Typically, a backhoe or mini-excavator suffices for trench digging.
Once the plumbing has been installed in the trench, it is covered with backfill. For every tonne of GSHP capacity, approximately 500-600 feet of pipe is required.
System vertical, closed-loop characteristics
Vertical, closed loops may descend 100 to 400 feet. A 4-inch diameter hole is bored 20 feet apart from other vertical loops for each tonne of pump capacity. Vertical loop systems must be excavated using sophisticated well-drilling equipment.
Vertical loop systems often use less tubing than horizontal configurations. Each tonne of pump capacity needs 300-600 feet of tubing.
Components of an interior geothermal HVAC system
In your house, both closed and open-loop geothermal systems contain comparable components.
The subterranean pipe is initially installed through the floor or wall. It is connected to the heat pump in the basement. No outside compressor is present, unlike typical heating and cooling systems.
Existing ducting and air handling systems can be utilized to complete your geothermal home energy installation. If not, new ductwork with at least a big blower and filter must be installed to distribute warm or cold air throughout your home’s rooms.
Geothermal Heating And Cooling Lessons For The House
According to the United States Environmental Protection Agency, a geothermal heating and cooling system for your house are the most efficient, cost-effective, and environmentally-friendly energy system available.
Geothermal energy from the ground is 100 percent renewable energy that is always accessible and is sourced directly from the earth.
Some homes may find the initial installation costs excessive. However, the payback time is typically between 2 and 7 years when energy savings, tax rebates, and other incentives are included.
Because geo-exchange systems rely on the consistent temperature of the Earth below the frost line, they can be implemented everywhere.
There are a variety of conceivable loop systems. The optimal decision relies on the peculiarities of your property.
Earth-coupled energy systems for house heating and cooling have a relatively small carbon footprint compared to conventional HVAC systems. Geothermal residential energy systems are thus a vital component of the answer to our climate dilemma.
