Geothermal

What Does Geothermal Mean?

The term geothermal means "of or relating to the internal heat of the earth." Geothermal energy is a renewable and sustainable source of thermal energy that originates from the Earth's core. This natural heat is continuously produced within the earth and can be harnessed for various applications, including heating, cooling, and electricity generation.

A few feet below the surface, the ground maintains a relatively constant temperature year-round, typically between 40°F and 70°F, depending on your location. This stable underground temperature is warmer than the air in the winter and cooler than the air in the summer, making it an efficient energy source for heating and cooling buildings.

What Is a Geothermal Heat Pump?

In commercial HVAC systems, geothermal energy is used by geothermal heat pumps (GHPs), also known as geoexchange or ground-source heat pumps. These systems leverage the stable temperature of the earth to provide highly efficient heating and cooling. A geothermal heat pump system consists of three main components: an underground loop of pipes (also called an exchanger), an indoor heat pump unit, and a distribution system to deliver conditioned air throughout the building.

How Does a Geothermal Heat Pump Work?

A geothermal HVAC system works by circulating a water-based solution through underground pipes (called ground loops). These loops absorb or release heat, depending on the season, and deliver it back to the building through a geothermal heat pump.

• Heating: During the winter, the fluid in the ground loop absorbs heat from the surrounding earth (a heat source). This heated fluid is then circulated to the indoor heat pump, which concentrates the heat and distributes it throughout the building via traditional ductwork or a radiant floor system.
• Cooling: In the summer, the process is reversed. The system extracts excess heat from the building and transfers it to the fluid in the ground loop. The fluid then circulates underground, where the heat is dissipated into the cooler earth (a heat sink).

Additionally, the geothermal heat pump may recover excess heat from within the building – for example, from people, computers, and lighting. That heat is then transferred to other parts of the building or into the ground or lake for later use.

How Deep Must We Dig?

The size of the available land and your budget determine the ground-source heat pump depth you need. Three types of heat exchangers are available:

• Horizontal heat exchanger: For horizontal loops, you need to dig trenches of three to six feet (one to two meters). These are shallow but require more land area.
• Vertical heat exchanger: For vertical loops, you need less surface area; instead, you need the ability to drill boreholes to a depth of 160 to 650 feet (50 to 200 meters).
• Lake or large pond: Access to a deep enough nearby body of water can also provide a stable heat source/sink and may be more economical than drilling.

When and Where Can Geothermal HVAC Be Used?

Geothermal systems are a viable option for a wide range of commercial buildings, including schools, universities, government buildings, office parks, and healthcare facilities. They are particularly effective in:

• New Construction: Integrating a geothermal heating and cooling system during the initial construction phase can be more economical.
• Major Renovations: Retrofitting older buildings with geothermal systems can significantly improve energy efficiency.
• Properties with Available Land: The installation of the ground loop requires sufficient space. However, different loop configurations are available to accommodate various site conditions.
• Regions with High Energy Costs: The significant energy savings offered by ground-source heat pump systems are especially beneficial in regions with high electricity rates.
• Climates with Extreme Temperatures: Geothermal systems perform exceptionally well in both very cold and very hot climates because their efficiency is not dependent on fluctuating outdoor air temperatures.

Advantages of a Geothermal Heat Pump System

Geothermal systems offer a multitude of benefits for commercial buildings:

• High energy efficiency: Geothermal heat pumps are the most efficient heating and cooling systems available today. They can achieve efficiencies of 300%-600%, meaning they produce three to six units of energy for every one unit of electricity consumed. This can lead to energy consumption reductions of up to 70% compared to conventional HVAC systems.
• Significant cost savings: The high efficiency of geothermal systems translates to substantial long-term savings on utility bills. While the initial installation cost can be higher than traditional systems, the payback period is often between 5 to 10 years.
• Environmental friendliness: Geothermal HVAC systems are an environmentally responsible choice. They don't burn fossil fuels, resulting in a significant reduction in greenhouse gas emissions and a smaller carbon footprint.
• Enhanced comfort and quiet operation: These systems provide consistent and even heating and cooling, eliminating the temperature fluctuations sometimes experienced with conventional systems. They also operate very quietly.
• Durability and low maintenance: The indoor components of a geothermal system can last for 20 to 25 years, while the underground loop can have a lifespan of over 50 years. With fewer moving parts and protection from the outdoor elements, these systems require minimal maintenance.
• Versatility: Commercial geothermal heat pump systems can be used for a variety of applications, including heating and cooling, hot water production, and even pool heating.
• Preservation of usable real estate: Underground loops allow the surface area to remain fully functional for needs like parking or playgrounds.
• Design flexibility: These systems work for single buildings or campuses and districts and support zoning and simultaneous heating and cooling with a shared water loop.

Additional Considerations:

Ground-source heat pumps are among the most efficient heating and cooling systems in existence today, and they are a powerful tool in the engineer's arsenal for application in green buildings due to their energy benefit.

The design of the ground loop and distribution system, and the number and size of heat pumps, can be modified depending on your specific facility's footprint and layout so that commercial geothermal will work in any commercial building.

Resources for Geothermal Heat Pump Systems

• Geothermal Systems
• How Thermal Energy Storage can be the Key for Cold Climate Heat Pumps
• Case study: North Shore District 112 Geothermal Install
• Case study: Robins Air Force Base
• Case study: Powering Efficiency at Marine Gateway Development
• Case study: University of Central Missouri

Geothermal systems represent a proven, reliable technology for commercial HVAC applications that delivers exceptional performance, significant energy savings, and environmental benefits across all climate zones. Contact your local Trane Commercial HVAC representative today to determine if a geothermal HVAC system will work for your building or campus.