What is a geothermal heat pump system

Ground-Source Heat Pumps

Arif Hepbasli, in Encyclopedia of Energy, 2004

1 Ground-Source Heat Pumps

Ground-source heat pumps are not a new idea. Patents on the technology date back to 1912, in Switzerland. One of the oldest GSHP systems in the United States, in the United Illuminating headquarters building in New Haven, Connecticut, has been operating since the 1930s.

There are two main types of GSHP systems: ground-coupled (vertical or horizontal) closed loop and water-source (groundwater) open loop, as shown in Figs. 1 and 2, respectively. Ground-coupled heat pumps (GCHPs) are known by a variety of names. These include ground-source heat pumps, earth-coupled heat pumps (ECHPs), earth energy heat pumping systems, earth energy systems, ground-source systems, geothermal heat pumps, closed-loop heat pumps, solar energy heat pumps, geoexchange systems, geosource heat pumps, and a few other variations. In marketing ground-source heat pumps, to cope with the diverse terminology, sales personnel may wish to connect GCHPs to renewable energy sources (solar, geothermal), to connect them to environmental awareness (earth energy), and to dissociate them from air heat pumps (ground-source systems). However, two terms are commonly used to describe the technology in general: geothermal heat pumps and ground-source heat pumps. The former term is typically used by individuals in marketing and government, and the latter is used by engineering and technical types. In addition, ground-coupled, groundwater, and surface water heat pumps are referred to as subsets of ground-source heat pumps. The systems will be referred to as ground-source heat pumps throughout this text.

What is a geothermal heat pump system

Figure 1. Ground-coupled (closed-loop) systems. Reproduced by permission from the Geo-Heat Center, Oregon Institute of Technology.

What is a geothermal heat pump system

Figure 2. Groundwater (open-loop) systems. Reproduced by permission from the Geo-Heat Center, Oregon Institute of Technology.

The closed-loop systems use a buried earth coil as the ground heat exchanger (GHE) through which a heat transfer fluid, typically an antifreeze solution, is circulated. The GHE, installed either vertically in borings or horizontally in trenches, exchanges heat with the ground (Fig. 1). In open-loop systems, the groundwater is pumped into the heat pump unit, where heat is extracted from (or rejected into, depending on mode of operation) the water; the water is then disposed of in an appropriate manner. If possible, releasing the water into a stream, river, lake, pond, ditch, or drainage tile, known as open discharge, is the easiest and least expensive disposal method. A second means of water discharge is using a return well that returns the water to the ground aquifer (Fig. 2).

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Heat pumps and absorption chillers

Mamdouh El Haj Assad, ... Marc A. Rosen, in Design and Performance Optimization of Renewable Energy Systems, 2021

11.3.2 Benefits of geothermal heat pump systems

Geothermal heat pumps have a range of advantages, the most significant usually being their capability to provide a renewable and sustainable source of energy. Such systems thus help reduce greenhouse gas emissions. Geothermal heat pumps operate without harmful substances, are highly efficient, and have stable output capacities. They provide comfort and good air quality based on simple equipment and control mechanisms. Geothermal heat pump systems do not require equipment in the outdoor air, and they are relatively cost-efficient for water heating. They can be applied in a variety of situations, including residential, industrial, and commercial cooling and heating systems.

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Energy systems in buildings

Getu Hailu, in Energy Services Fundamentals and Financing, 2021

8.6.2 Ground-source heat pumps

GSHPs utilize the nearly constant temperature of the ground as the heat exchange medium. Even though the ambient temperature varies significantly around the world, from baking heat in the summer to subzero temperatures in the winter, in most parts, a few meters below the earth’s surface the ground temperature is nearly constant. Depending on the location, ground temperatures range from 7°C to 21°C (Kim et al., 2014). Ground temperature is cooler than the ambient air in the summer and warmer than the ambient air in the winter. GSHPs take advantage of this; they exchange heat with the ground. As any heat pump, GSHPs can be used for both heating and cooling. Compared to ASHPs, GSHPs are quieter, last longer, need little maintenance, and most importantly, they do not depend on the outdoor ambient air temperature.

One drawback of GSHPs may be their initial cost, which is estimated at about 50%–100% more than that of ASHP. This additional cost is associated with the costs of digging a ground loop into the land. Although there is greater initial cost of installing GSHPs, they are more efficient when it comes to heating, which results in higher fuel savings and lower energy bills.

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Conclusions

Vivian W.Y. Tam, ... Khoa N. Le, in Sustainable Construction Technologies, 2019

GHP is the most energy efficient renewable technology and as a heat pump is able to provide both heating and cooling by taking advantage of the stable temperatures in the earth. There are two available GHP systems configurations, which allow the system to be assembled vertically or horizontally and depend directly on the type of rock and soil:

Open-looped (ground-coupled) system that is recommended in climates with moderate temperature variations and the existence of surface water.

Close-looped (groundwater) system that is allowed transferring the ground temperature to the GHP system by underground continuous piping loops (Cui et al., 2015).

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Recent progress in geothermal heat pumps

Maryam Karami, ... Jafar Esmaeelian, in Recent Advances in Renewable Energy Technologies, 2022

Abstract

Geothermal heat pumps, or ground source heat pumps (GSHP), which use shallow geothermal resources (normally a depth of 400 m) as heat source/sink, were first experimentally investigated by A.C. Crandall (1946) and gained popularity in Sweden in the 1970s. The leading countries in developing the market of GSHPs were Sweden and Switzerland in the early 1980s. Other countries experienced a slow growth rate so that by new installations in some countries such as Turkey, Indonesia, Kenya, Costa Rica, Japan, Mexico, The United States, and Germany in 2018 the geothermal direct useful thermal output was reached around 117 TWh (421 PJ) in 2019. The installed GSHP has the size of 3.5 kW for a residential building to more than 150 kW for large applications such as commercial building, hospitals, schools, etc.

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Impact of Energy and Atmosphere

Sam Kubba Ph.D., LEED AP, in Handbook of Green Building Design and Construction, 2012

Geothermal Heat Pumps

Geothermal heat pumps (GHPs)—sometimes referred to as geoexchange, earth-coupled, ground-source, or water-source heat pumps—have been in use for several decades. This is a technology that is gaining wide acceptance for both residential and commercial buildings. Studies show that approximately 70% of the energy used in a geothermal heat pump system is renewable energy from the ground and this system is more than 45% more energy-efficient than standard options. According to ENERGY STAR, “geothermal heat pumps (GHPs) are among the most efficient and comfortable heating and cooling technologies currently available, because they use the earth's natural heat to provide heating, cooling, and often, water heating.”

A GHP uses the relatively constant temperature of the ground or water several feet below the earth's surface as its source of heating and cooling. The earth's constant temperature is what makes geothermal heat pumps one of the most efficient (relative to air-source heat pumps), comfortable, and quiet heating and cooling technologies available today. GHPs also last longer, need little maintenance, and do not depend on the temperature of the outside air. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings.

There are four basic classifications of ground-loop systems. Three of these—horizontal, vertical, and pond/lake—are closed-loop systems. The fourth is the open-loop option; these systems use well or surface water as the heat exchange fluid that circulates directly through the GHP. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. Which one of these is best depends on climate, soil conditions, available land, and local installation costs at the site. All of these approaches can be used for residential and commercial building applications. The first three classifications are described in Table 9.2.

Table 9.2. Ground-Loop System Classifications

SystemDescription
Horizontal This type of installation is generally the most cost effective for residential installations, particularly for new construction, where sufficient land is available
Vertical These systems are often used by large commercial buildings and schools because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping.
Pond/lake This may be the lowest cost option if the site has an adequate body of water. A supply line pipe is run underground from the building to the water and coiled into circles at least eight feet under the surface to prevent freezing.

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An overview of ground-source heat pump technology

Rao Martand Singh, ... Tony Amis, in Managing Global Warming, 2019

Abstract

Ground-source heat pumps (GSHPs) are renewable and environment-friendly systems that utilize the shallow ground energy to achieve space heating and cooling for the purpose of thermal comfort. The system works by circulating water-based solution in energy loops made from high-density polyethylene (HDPE) pipes, to transfer heat energy between superstructures (buildings) and the ground. This chapter presents an overview of the GSHP technology including different components of the system and their respective working principle, design considerations, and factors affecting the system performance. Lastly, few case studies are presented to give the reader an insight into GSHP systems currently operating in the UK.

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Energy conversion systems and Energy storage systems

Jian Zhang, ... Pedro J. Mago, in Energy Services Fundamentals and Financing, 2021

7.2.1.5 Geothermal system

Geothermal energy is a clean and sustainable energy generated by the earth. Compared to the conventional fossil-fueled systems, geothermal energy systems are usually environment friendly with much lower emissions (Wu, 2009; Neves et al., 2020). Generally, geothermal energy is utilized via three technologies: electricity production, direct heating, and geothermal heat pumps, providing indirect heating and cooling for buildings (Wu, 2009). According to a worldwide review on geothermal energy made by Lund et al. Lund and Boyd (2016), geothermal heat pumps make up the largest share of energy usage and capacity installation, accounting for 55.15% of the energy usage and 70.90% of the installed capacity.

Geothermal heat pumps, also known as ground-source heat pumps (GSHPs), are considered as one of the most energy-efficient technology for space heating and cooling in buildings. Typically, GSHP systems consist of three core subsystems (U.S. Department of Energy DOE, 2019; Self et al., 2013):

1.

Earth connection: circulating the working fluid (water or antifreeze solution) to absorb heat from or reject heat to the ground via a ground heat exchanger (GHE) loop.

2.

Heat pump: transfer heat between the building and the earth connection.

3.

Heat distribution: distribute heated or cooled air throughout the building space.

The way that a GSHP system works is based on the fact that the temperature beneath a certain distance of the earth’s surface remains at a nearly constant temperature throughout the year, warmer in the winter and cooler in the summer than the air. In the winter time, a GSHP system extracts heat from the ground and distributes it to the building space, whereas in the summer time, it removes heat from the building and transfers it to the ground for cooling. Based on the geothermal sources, that is, groundwater, surface water, and ground, GSHP systems have been classified into three categories by ASHRAE (2011): groundwater heat pump (GWHP) systems, which transfer heat with ground water; surface water heat pump (SWHP) systems, which use the surface water such as pond, reservoir, lake, and so on as heat source or sink; and ground-coupled heat pump (GCHP) systems. The schematics of each system are displayed in Fig. 7.9. Among different types of GSHP systems, the GCHP is the most attractive one. In a GCHP system, a GHE is employed to combine the refrigerant loop and the water loop as a closed loop. Based on the arrangement of the pipes connected to GHE, the closed loop systems are classified as vertical closed loop and horizontal closed loop. Literally, the pipes in the ground run vertically in a vertical closed loop, whereas they run horizontally in a horizontal closed loop, as shown in Fig. 7.10.

What is a geothermal heat pump system

Figure 7.9. Schematic of different GSHP systems: (A) GWHP, (B) SWHP, and (C) GCHP (Sarbu and Sebarchievici, 2014).

What is a geothermal heat pump system

Figure 7.10. (A) Vertical closed loop and (B) horizontal closed loop (Sarbu and Sebarchievici, 2014).

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Geothermal Energy

L. Rybach, in Comprehensive Renewable Energy, 2012

Abstract

A geothermal heat pump (GHP) is a central heating and/or cooling system that pumps heat to or from the ground. It uses the earth as a heat source (in the winter) or a heat sink (in the summer). They can be established in sizes from a few thermal kW to several MW capacity. GHPs are among the fastest growing renewable energy technologies: from 1995 to 2010 the globally installed capacity grew exponentially with 20% per year. Various GHP types are used: horizontal loops, energy piles (foundation piles equipped with heat exchanger pipes), ground water wells, borehole heat exchangers. GHPs can provide space heating, cooling, and domestic water with the same equipment. The core piece is the heat pump, mostly driven by electricity. Design and installation, especially of large systems, need careful sizing and engineering, tailor-made to cope with the local needs, climatic conditions, and ground properties. Careful design also guarantees production sustainability. Current installation and maintenance costs make GHPs competitive on the market.

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Impact of Energy and Atmosphere

Sam Kubba PH.D., LEED AP, in Handbook of Green Building Design and Construction (Second Edition), 2017

Geothermal Heat Pumps

Geothermal heat pumps (GHPs, sometimes referred to as GeoExchange, earth-coupled, ground source, or water source heat pumps) have been in use for several decades. It is a technology that is gaining wide acceptance for both residential and commercial buildings. Studies show that approximately 70% of the energy used in a GHP system is renewable energy from the ground and more than 45% more energy efficient than standard options. According to Energy Star, “Geothermal heat pumps (GHPs) are among the most efficient and comfortable heating and cooling technologies currently available, because they use the earth’s natural heat to provide heating, cooling, and often, water heating.” This system utilizes the relatively constant temperature of the ground or water several feet below the earth’s surface as source of heating and cooling. The earth’s constant temperature is what makes GHPs one of the most efficient (relative to air source heat pumps), comfortable, and quiet heating and cooling technologies available today. They also last longer, need little maintenance, and do not depend on the temperature of the outside air. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Setup costs are normally higher than for conventional systems, but the difference is usually reimbursed in energy savings in 3–10 years, and shorter lengths of time if federal, state, and utility tax credits and incentives are taken into account.

There are four basic classifications of ground loop systems. Three of these—horizontal, vertical, and pond/lake—are closed-loop systems. The fourth type of system is the open-loop option; these systems use well or surface water as the heat exchange fluid that circulates directly through the GHP. Once water has circulated through the system, it returns to the ground through the well, a recharge well, or surface discharge. Which one of these systems is best depends on the climate, soil conditions, available land, and local installation costs at the site. All of these approaches can be used for residential and commercial building applications. The first three classifications are described in Table 9.2.

Table 9.2. Ground-loop system classifications

SystemDescription
Horizontal This type of installation is generally the most cost-effective for residential installations, particularly for new construction, where sufficient land is available
Vertical These systems are often used by large commercial buildings and schools because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping
Pond/lake This may be the lowest cost option if the site has an adequate body of water. A supply line pipe is run underground from the building to the water and coiled into circles at least 8 ft under the surface to prevent freezing

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How does a geothermal heat pump work?

For heating, a geothermal heat pump removes the heat from the fluid in the earth connection, concentrates it, and then transfers it to the building. For cooling, the process is reversed. Conventional ductwork is generally used to distribute heated or cooled air from the geothermal heat pump throughout the building.

What is the downside of geothermal heating?

Con: Higher upfront cost for geothermal The initial costs of buying a geothermal system exceed those of a single conventional furnace, boiler, or air conditioning unit. Buying a new furnace could cost anywhere from $2,000 to $6,000 upfront. This is based on furnace type, efficiency, size, and installation cost.

Which is better heat pump or geothermal?

According to the EPA, a geothermal heating and cooling system can reduce energy consumption and corresponding emissions by more than 40 percent as compared to an air-source heat pump, and by over 70 percent as compared to standard heating and cooling equipment.

What are 4 reasons to use geothermal heat pumps?

While there are many heating systems to choose from, here are five strong reasons why you should choose geothermal..
Efficient heating and cooling. ... .
Environmentally-friendly, renewable energy. ... .
Annual savings on heating and cooling. ... .
Improved comfort. ... .
Hot water, too!.