Ground Source Heat Pump: a Complete Guide

Figure 1: Ground source heat pump unit.

Ground source heat pumps (GSHPs) are a type of renewable energy technology that can be used to heat and cool buildings. They are becoming increasingly popular as people look for ways to reduce their carbon footprint and energy costs. In this article, we will explore what a ground source heat pump is, how it works and more.

1. What is a Ground Source Heat Pump?

A ground source heat pump ((also geothermal heat pump)) is a heating and cooling system that uses the earth's natural heat to regulate the temperature of a building. The type of heat pump is made up of a buried loop of pipes that contain a fluid. The fluid circulates through the pipes and absorbs heat from the ground in the winter and transfers heat to the ground in the summer.

The loop is buried in the ground either horizontally or vertically, depending on the available space. Horizontal loops are more common and require a large area of land, while vertical loops are suitable for smaller spaces and can be installed in a borehole.

1.1 Components of a Ground Source Heat Pump System

A ground source heat pump system consists of several key components:

1. The heat pump unit: This is the main component of the system and is responsible for extracting/releasing heat from/to the fluid flowing through the pipes buried in the ground.

2. The ground loop: This is the buried loop of pipes that contains the fluid. The loop can be made of a variety of materials, including high-density polyethylene (HDPE) and polybutylene (PB).

3. The fluid: The fluid in the loop is typically a mixture of water and antifreeze.

4. The distribution system: This is the system of pipes that distributes the heat throughout the building. It can be either a radiator system or an underfloor heating system.

5. The control system: This controls the operation of the heat pump and ensures that it is working efficiently and effectively.

Figure 2: Ground heat pump system.

2. How Does a Ground Source Heat Pump Work?

A ground source heat pump works by taking advantage of the constant temperature of the earth. The temperature of the ground below the surface remains relatively stable throughout the year, ranging from 7°C to 12°C (45°F to 54°F) in most parts of the world. This temperature is known as the ground source temperature.

In winter, the heat pump extracts heat from the ground source and uses it to warm the building. The fluid in the pipes absorbs the heat and carries it to the heat pump’ heat exchanger. The refrigerant in the heat exchanger evaporates and then enters the compressor in which it increases its temperature and pressure.

Then the refrigerant enters another heat exchanger to release heat. The heat is then distributed through the building's heating system, either through radiators or underfloor heating.

In summer, the process is reversed. The heat pump extracts heat from the building and transfers it to the ground source through the buried loop. The heat is absorbed by the ground, and the cooled fluid is then circulated back to the heat pump to start the process over again.

Figure 3: Ground source heat pump application diagram.

3. Types of Ground Source Heat Pump

There are three main types of ground source heat pumps: horizontal, vertical, and pond/lake.

3.1 Horizontal Ground Source Heat Pumps

Horizontal ground source heat pumps are the most common type of ground source heat pump. They are installed in a horizontal loop, which is buried in trenches that are typically 1.5 to 2 meters deep. The length of the loop depends on the size of the building and the heating and cooling requirements.

Horizontal ground source heat pumps are suitable for properties with large gardens or open land. They require a lot of space to install, but the cost of installation is lower than other types of ground source heat pumps.

Figure 4: 3D rendered illustration of horizontal ground source heat pump system.

3.2 Vertical Ground Source Heat Pumps

Vertical ground source heat pumps are installed in a borehole that is drilled into the ground. The depth of the borehole depends on the size of the building and the heating and cooling requirements. The loop is then inserted into the borehole and connected to the heat pump.

Vertical ground source heat pumps are suitable for properties with limited space, such as urban areas. They require less space than horizontal ground source heat pumps, but the cost of installation is higher due to the drilling required.

Figure 5: 3D rendered illustration of vertical ground source heat pump system.

3.3 Pond/Lake Ground Source Heat Pumps

Pond/lake ground source heat pumps are installed in a loop that is submerged in a body of water, such as a pond or lake. The loop is connected to the heat pump, which extracts heat from the water and distributes it through the heating system.

Pond/lake ground source heat pumps are suitable for properties with access to a body of water. They are less common than horizontal and vertical ground source heat pumps, but they can be a good option for properties that do not have enough space for a horizontal loop or where drilling is not possible.

4. Benefits of Ground Source Heat Pumps

There are several benefits to using a ground source heat pump:

1. Energy efficiency: Ground source heat pumps are highly efficient and can produce up to three times more energy than they consume. This means that they can save homeowners a significant amount of money on their energy bills.

2. Low carbon emissions: Ground source heat pumps produce very low carbon emissions compared to traditional heating systems. This makes them an environmentally friendly option for homeowners who are concerned about their carbon footprint.

3. Long lifespan: Ground source heat pumps have a long lifespan and can last up to 25 years with proper maintenance. This makes them a cost-effective option for homeowners who want a long-term heating solution.

4. Low maintenance: Ground source heat pumps require very little maintenance compared to traditional heating systems. This means that homeowners can save money on maintenance costs over the lifespan of the system.

5. Versatility: Ground source heat pumps can be used for both heating and cooling, making them a versatile option for homeowners.

Figure 6: Ground source heat pump installation.

5. Drawbacks of Ground Source Heat Pump

While ground source heat pumps (GSHPs) offer many benefits, there are also some drawbacks to consider before investing in this type of heating and cooling system. Here are some of the potential drawbacks of ground source heat pumps:

1. High upfront cost: The initial cost of installing a ground source heat pump system is typically higher than that of traditional heating and cooling systems. This is due to the cost of the equipment, installation, and any modifications that may be needed to the property.

2. Ground disturbances: Installation of a ground source heat pump system may cause disruption to the land, such as digging trenches or drilling boreholes. This can be an issue for some homeowners, particularly those with landscaped gardens or historic properties.

3. Installation complexity: Installation of a ground source heat pump system requires specialized expertise and equipment. As such, it can be more complex and time-consuming than traditional heating and cooling systems.

4. Potential for system failure: While well-maintained ground source heat pump systems are generally reliable, they can still experience issues such as leaks, blockages, or compressor failures. Repairs and replacements can be costly and disruptive.

5. Limited cooling capacity: Ground source heat pumps are primarily designed for heating, and their cooling capacity may be limited in some climates or situations.

6. Limited availability: Ground source heat pump systems require suitable land or water sources for installation, making them less viable for some properties or locations. Additionally, it may be difficult to find qualified installers or maintenance providers in some areas.

Figure 7: using an excavator to help install a ground source heat pump system.

6. Ground Source Heat Pump Installation and Costs

The installation of a ground source heat pump can be more expensive than traditional heating systems. However, the long-term savings on energy bills can offset the initial cost. The cost of installation can vary depending on several factors, including the size of the system, the type of ground loop, and the complexity of the installation.

In general, the cost of a ground source heat pump system can range from $10,000 to $30,000 or more. However, there are incentives and rebates available in many areas that can help offset the cost.

7. Factors to Consider When Choosing a Ground Source Heat Pump

When choosing a ground source heat pump, there are several factors to consider:

1. Property size and heating and cooling requirements: The size of the property and the heating and cooling requirements will determine the size of the ground source heat pump required.

2. Available space: The type of ground source heat pump that can be installed will depend on the available space. Horizontal ground source heat pumps require the most space, while pond/lake ground source heat pumps require access to a body of water.

3. Soil type: The type of soil will affect the efficiency of the ground source heat pump. Some soils are better at conducting heat than others.

4. Installation costs: The installation costs will vary depending on the type of ground source heat pump and the complexity of the installation.

5. Maintenance costs: Ground source heat pumps require very little maintenance compared to traditional heating systems. However, it is important to factor in any maintenance costs when choosing a system.

Figure 8: Ground source heat pump installation project.

8. FAQs

8.1 How Much Space Needed for Ground Source Heat Pump?

The amount of space needed for a ground source heat pump depends on the type of system being installed.

● Horizontal ground source heat pumps require a significant amount of space, as they are installed in a loop that is buried in trenches that are typically 1.5 to 2 meters deep. ●Vertical ground source heat pumps require less space, as they are installed in a borehole that is drilled into the ground.
● Pond/lake ground source heat pumps require access to a body of water, such as a pond or lake.

8.2 How Deep Does Ground Source Heat Pump Need to be?

The depth of a ground source heat pump (GSHP) system depends on the type of system being installed.

● Horizontal GSHP systems typically require trenches that are 1.5 to 2 meters deep.
● Vertical GSHP systems, on the other hand, require boreholes that can range from 30 to 150 meters deep, depending on the size of the building and the heating and cooling requirements.
● Pond/lake GSHP systems require a loop submerged in a body of water, which can vary in depth depending on the location and the size of the system.

8.3 Are Ground Source Heat Pumps Better than Air Source?

Whether ground source heat pumps (GSHPs) are better than air source heat pumps (ASHPs) depends on the specific circumstances of the property and the preferences of the homeowner.

GSHPs tend to be more efficient than ASHPs, as they are able to draw heat from the ground, which remains at a relatively constant temperature. This means that GSHPs can provide a more consistent level of heating and cooling throughout the year.

However, GSHPs are typically more expensive to install than ASHPs, as they require more extensive excavation work. ASHPs can be a good option for properties with limited space or where excavation work is not possible.

8.4 Do Ground Source Heat Pumps Work in Cold Climates?

Yes, ground source heat pumps (GSHPs) can work in cold climates. While the temperature of the ground may be cooler in winter, it remains relatively constant throughout the year and is typically warmer than the outside air temperature in winter. This means that GSHPs can still extract heat from the ground and use it to heat a building, even in cold climates.

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