What Are Geothermal Heating Systems?
A geothermal heating system is an ultra-efficient technology which involves the use of clean, renewable ground source thermal energy to heat and cool a home. Geothermal heating is also referred to as a ground source heat pump system, and it involves tapping into the earth’s natural warmth to provide heating.
The term “geothermal” has its root in the Greek language, a literal translation is “earth heat”. Accessing this stable energy source with a geothermal heating and cooling system can provide your home with efficient air conditioning, heating along with the generation of hot water.
At the heart of any geothermal heating system is a geothermal heat pump, which is an electrically powered unit that exchanges thermal energy to and from the earth. A ground source heat pump takes advantage of the constant subterranean temperature of 57°F (in Maryland) and channels the heat from 300 feet underground to the geothermal heating, ventilation, and air conditioning (HVAC) system.
Geothermal Heating Systems Act As:
- A heat source to heat one’s residence during the winter
- A heatsink to cool one’s residence during the summer
- A heat source for heating water for domestic use
How Do Geothermal Heating Systems Work?
A geothermal heat pump works automatically, varying its output depending on the ambient temperature of one’s home.
During winter, the ground source heat is absorbed by pumping an anti-freeze and water-based solution through the system’s geothermal loop field. The fluid circulates around this loop, transmitting the absorbed heat to a refrigerant via the evaporator, changing it from a liquid to gas. From here it passes through the compressor, increasing the temperature of the gas as a direct result of the compression process. From here, the gas moves to the condenser, which transfers the heat to the air blowing throughout the home’s central heating system.
As this process continues, the refrigerant fluid cools down and the system automatically circulates the solution back into the ground where the earth’s infinite supply of heat is transferred again, and the heating process repeats itself.
During summer, this process reverses. Excess heat is transferred to the geothermal loop field as hot air is blown over the significantly colder solution that continuously circulates within the system’s geothermal loops.
Aside from space heating, the geothermal heating system can also be connected to a device known as a geothermal desuperheater. The geothermal desuperheater can recycle the excess heat generated from the ground source heat pump compressor and uses it to heat water. This means that this device can also provide free hot water for domestic use in addition to its conventional geothermal heating and cooling purpose.
A geothermal desuperheater is useful and very efficient, especially during the Summer while the system acts to cool one’s home. This is because the excess heat absorbed from within the house is conducted into the hot water tank rather than being transmitted back into the earth. The result, therefore, is free hot water! Moreover, during winter, the heat from underground can be absorbed to heat domestic water alongside its primary purpose of providing space heating. This means that cost savings are still realized during the colder period. In fact, a desuperheater reduces winter water heating costs by approximately 50 percent.
Why Should You Invest in a Geothermal Heating and Cooling System?
- Geothermal Heating is a Sustainable and Renewable Energy
A geothermal heating system does not generate its power by burning fossil fuels such as gas, oil, or coal. Instead, it absorbs heat from within the earth. Furthermore, a geothermal heating and cooling system uses significantly less electricity compared to a standard electric heat-resistance heat pump. This makes a geothermal heating system an attractive solution to cut your carbon footprint, providing a positive impact on the environment.
- Geothermal Heating Saves Money
Using a geothermal system can make significant savings on your energy bills throughout the year, as much as 80 percent on your home’s energy costs.
- Geothermal Heating is Independent and More Reliable Than Other Renewable Energies
A geothermal heating system is more reliable than alternatives, and is not affected by any external factors, unlike other renewable energies such as wind energy and solar power. For instance, wind energy can only be used when there is wind, while solar energy relies on regular sunshine to work efficiently. Geothermal heating is dependent on neither the wind nor the sun, but instead takes its heat from the earth’s crust, which is always hot. This makes geothermal heating an available and reliable source of energy.
- Geothermal Heat Pumps are Highly Efficient
Geothermal heat pumps are extremely efficient, because ground source heating is extracted from depths where the temperature is always at a constant temperature. These systems can attain a geothermal efficiency of about 300 to 600 percent during the, Coldest winter nights; whereas air-source heat pumps can only attain an efficiency of about 175 to 250 percent on the coldest days of winter. Just like other types of heat pumps, ground source heat pumps have their geothermal efficiency rated according to their coefficient of performance (COP). COP rates how much heat a system produces or removes (depending on whether it is, Heating or cooling), versus how much the system uses to create the heating or cooling effect. Most ground source heat pumps have COPs of about 3.0 to 5.0. What this means is that for every unit of energy used by a geothermal heat pump, approximately 3 to 5 units are supplied back in the form of heat.
- Geothermal Heat Pumps are Durable
A geothermal heat pump offers a quiet heating and cooling solution that does not disturb your neighbors with noise. Additionally, the ground source heat pump is extremely durable and can last you for many years with just a very little amount of maintenance, a big difference to the significant maintenance a more traditional system requires. If a geothermal heat pump is properly installed, the geothermal ground loop is also long-lasting. The handling unit, a geothermal pump, compressor and fan, are all installed indoors to protect them from unfavorable weather conditions, ensuring they can last for many years. Normally, annual coil cleaning, routine check, and filter changes are the only maintenance required to keep everything performing properly.
How Geothermal Heating and Cooling Systems Works?
Unlike conventional heating and cooling systems, the geothermal heating and cooling system does not generate heat from burning fossil fuel. The geothermal HVAC system simply conducts heat to and from the earth depending on the condition of the building. Electrical power is only needed to run the handling unit’s pump, compressor, and fan.
Generally, the outdoor temperature we experience fluctuates with the changing seasons. However, underground, the temperature remains relatively constant and does not change dramatically throughout the year, due to the earth’s insulating properties.
At about 4 to 6 feet below the surface, the geothermal heating system, which usually consists of an indoor handling unit, the geothermal loop, and a pump to reinjection well, relies on this constant temperature to supply “free” energy for geothermal heating, ventilating, and air conditioning (geothermal HVAC).
A geothermal HVAC is not the same as geothermal energy though, and the two should not be confused. Where a geothermal HVAC taps into the heat inside the earth for space heating, cooling or for heating one’s water supply, geothermal energy is the process by which the heat inside the earth is used for generating power in the form of electricity. The two operations use different processes, with geothermal energy requiring water be heated to boiling point to achieve its aims.
In a geothermal HVAC system, polyethylene pipes that make up the geothermal loop are buried under the ground, either vertically or horizontally, depending on the installation. Refrigerant fluid is usually used to fill the loop and conduct the heat.
There are several approaches to this, for instance an “open loop” system may be used if an aquifer is available. In this case, the engineers drill a well into the underground water table. Water from the well is pumped up into the unit, circulated through a heat exchanger, and then returned to the aquifer via reinjection.
During winter, the refrigerant fluid inside of the geothermal loop inserted beneath the earth or inside the well absorbs geothermal heat and air from within the earth and conducts it upward into the indoor unit. The indoor handling unit compresses the heat and air to a higher temperature and then circulates this throughout the building, working like an air conditioner in reverse.
During the summer periods, the geothermal HVAC system works in the opposite way, by pulling heat from within the building and conducting it to the reinjection well via the underground heat pump/ loop. The heat is then deposited into the cooler aquifer/earth.
The geothermal heating system has 4 main components, which are the thermal heat pump (indoor handling unit), the geothermal heat exchanger (either closed or open geothermal loop), the air delivery system and the geothermal radiant heat (in either the floor or somewhere else).
How Does A Geothermal Heating and Cooling System Work?
A conventional geothermal heat pump circulates a heated or cooled fluid to and from underground to regulate the temperature within a building. Although geothermal energy systems seem like a new technology, they have been in use since the late 1940s.
Understanding the Different Designs
There are several design approaches in use today; however, all ground source heat pumps operate with similar principles. Each one pumps liquid through the geothermal loop between the surface units and the underground heat source, whether that be an aquifer or the internal heat within the earth at depth. These different heat sources also dictate the nature of the system itself, with an aquifer using an open loop, and systems based upon the earth’s heat using a closed loop.
Determining which is the best geothermal home heating system, length of the geothermal ground loop and design for a residential geothermal heating system all depend on a variety of factors, including the local installation costs, the required cooling and heating load, land availability, soil conditions and climate factors, etc.
Open Loop System
Less common than the closed loop system, the open loop system is designed to capture heat from an underground geothermal well. This means that the property owner must have a sufficient supply of water. Unlike the closed loop system, the liquid in the open loop system is not circulated continuously throughout the system.
Instead, as the liquid is pumped through the closed loop pipes, the heat in the fluid is extracted, and redirected to a return well. Some areas, however, do not allow open loop geothermal systems.
Closed Loop Systems
The closed loop geothermal system is found in two distinct designs, the horizontal loop system or vertical loop system. The horizontal closed loop geothermal system is usually the most affordable loop system for residential use. During installation of the horizontal closed loop geothermal system, a trench of about 4 to 6 feet is dug and the tubes are placed in it.
One downside is that the horizontal geothermal heat pump usually requires a larger surface area than a vertical installation. However, a smaller trench size and less surface area are required if the geothermal heating system installer uses coiled geothermal ground loops, which allows more loops to be fitted into a smaller area.
The vertical closed loop geothermal system is more expensive to install than the horizontal geothermal loop, as the name suggests the loop is installed vertically, requiring much deeper holes to be dug.
However, the geothermal vertical loop uses thinner uncoiled tubes that are looped to much greater depths, somewhere between 100 and 400 feet in most locations and requires much less space, making it the ideal choice for most homes where finding space for horizontal installations is a challenge, and no aquifer is available for alternative open loop options.
Earth River Geothermal, Inc. installs vertical closed loop geothermal loop fields because they provide better heat transfer properties between the earth and the fluid circulating within the geothermal pipes.
The Advantages of Geothermal Home Heating System
Geothermal heating systems require digging or drilling of the ground and some technical work to install, requiring the service of an experienced geothermal heating system installer to handle the installation project. This may increase the initial costs of installing the geothermal heating system.
However, the main question is “how much exactly does the geothermal heating system cost?” The answer is, aside from the initial high cost of installation, the geothermal heating system is an affordable energy source.
The U.S. Department of Energy research into geothermal heating has shown that a geothermal HVAC can cut energy consumption by between 25 and 50 percent compared to a conventional HVAC system.
This means that by using the geothermal heating system to heat a standard 1,500 sq. ft. home, you would be spending only about $30 to $50 monthly in most climates. Over time, that initial installation expenditure is returned many times over by reducing heating and cooling costs.
Long-Lasting and Safe
According to the U.S. Department of Energy, on average, a geothermal heat pump can last approximately 20 years and its underground geothermal loops can last between 25 and 50 years. The geothermal loop field does not require any repair or maintenance because it is protected from the elements, and the cost of repair and maintenance for the surface units is very low.
A geothermal heat pump is also a very safe heating and cooling solution, because it does not require any kind of combustion, unlike alternatives. This makes the WaterFurnace geothermal system a better option for those who are concerned about safety, both in terms of people and the environment, with geothermal solutions offering an eco-friendly energy source for heating and cooling homes.
A ground source heat pump does require electrical power to function, however, it does not generate any onsite emissions, unlike conventional boilers or fossil fuel-powered furnace. In addition, ground source heat pumps are much quieter than other conventional cooling/heating systems. The geothermal system does not contain any noisy fans or outdoor compressors. The indoor unit is also only as loud as a refrigerator.
The Drawbacks of Geothermal Home Heating System
High Upfront Cost
The cost of installing the geothermal heating and cooling system is its main drawback.
Geothermal heat system installation costs between $10,000 and $30,000, depending on the amount of drilling and digging required, site accessibility, geothermal system configuration, required plot size and the soil conditions.
As a result, the installation costs of the geothermal system are about 40 percent higher than that of a conventional HVAC system.
Disruption of the Landscape
Since installing the geothermal ground loop involves extensive digging and drilling, it may lead to the disruption of the surrounding landscape. This is especially true of a horizontal geothermal loop that requires a larger area to be excavated to lay the underground heating and cooling system.
The cost of returning a garden area or landscaping to its previous state must also be considered, and for many the idea of digging up a carefully created area is often a significant barrier to adoption of the geothermal system, however the vertically installed loop drastically reduces this disruption, making them a viable option even in situations where space is available for the horizontal approach.
In addition to these issues, if you rely solely on the geothermal home heating and cooling system, a backup system may be required to handle your heating and cooling needs in case of power outage, especially if you live in extreme climates, as without electricity to power the pump, the system ceases to function.
Not A DIY Project
Installing the geothermal home heating and cooling system is not something that can be undertaken yourself. Due to its structure, size and technicality, an effective installation of the geothermal home heating system requires the expertise of a well-trained and experienced installer.
The Technology Is Still Relatively New
Although commercial geothermal systems have been in existence since the mid-90s, and the idea established much earlier than that, its application in homes is still relatively new. That means there are fewer professional installers than with traditional systems, and less competition means higher prices. In general, because it is still not widely adopted, it can also be a challenge to find experienced installers at your location.
It Doesn’t Suit All Climates
The ground source heating system is not appropriate in areas with a consistently cold climate. This is because the lack of heat in these areas may cause the fluid in underground heat source pump to freeze and cause the pipes to burst.
Finally, a ground source heat pump system requires electricity to operate. In areas where there is an absence of reliable electrical power, a geothermal system would be useless. There are installations that use solar power to run systems, charging batteries to maintain operation overnight, but again, these are very climate dependent and not suitable everywhere.
Basic Requirements for Benefitting from Geothermal Heating
There are several requirements to get the best out of a geothermal heating system. Ground temperature is constant in most locations, so the ground source heat pump system can be used virtually anywhere. However, there are other areas that need to be considered:
The properties and composition of the soil in an area can affect the rate at which heat is conducted through the ground. These must be taken into consideration before choosing the best design of an underground heating and cooling system. Soil with positive heat transfer properties requires fewer pipes to achieve the desired underground heating and cooling effect, while those with reduced thermal conductivity will need more pipes.
While this will not affect overall performance once installed correctly, it does influence the initial installation cost, and it is something that must be considered at the beginning of the project.
To successfully install a geothermal heat pump, groundwater or surface water must be available, with the type and location of the water affecting the type of geothermal loop that can be used.
Depending on the water quality, volume, and depth, an open loop geothermal system may be installed. However, this process requires research into water quality to avoid potential problems.
Perhaps more than anything, the successful installation of a geothermal heating system is dependent on having the land available to install it. The land size, landscaping, layout, and the underground utilities within the land would affect the type of geothermal system that can be installed, determining not just the performance of the installed system, but also the cost.
For instance, the horizontal geothermal loop is usually installed in homes with a sufficient area of land. However, where there is a limited land space available, the vertical closed loop geothermal system can be installed, with the cost of each varying quite significantly.
Is Residential Geothermal Heating System Right for You?
The rate of adoption of geothermal cooling and heating systems is greatly increasing in the United States year by year. It has been observed that general interest in the installation of geothermal HVAC is really on the increase.
However, before you can embark on installing a geothermal cooling and heat pump for your home, it is important to find out whether the geothermal HVAC system is right for you. You should be considering a geothermal heating and cooling solution for your home if:
- You are building a new home and can add the installation costs onto your mortgage. By doing this, you will enjoy the lower energy costs from day one of your new home.
- You have a plan to stay in your new house for about 4 to 7 years or about 10 to 12 years (retrofit). This will allow you to recover the initial installation costs through energy or cost savings.
- Your home has a large area of lane with a large pond or a deep well. This would enable you to use an affordable geothermal ground loop.
The installation and implementation of geothermal heating system requires professional expertise. So, if you are considering the installation of the residential geothermal heating system, ensure that you contact a well-trained and well-experienced geothermal system installer who can help you find the appropriate solution for your situation.