Geothermal Advantages & Disadvantages
Geothermal heat pumps have several advantages and disadvantages. Which geothermal system is right for a given installation, or even whether to use a geothermal system, depends on the circumstances of that particular installation.
Among the advantages are:
- In both commercial and residential installations, geothermal heat pump systems typically have lower maintenance costs than conventional systems as all equipment is installed inside the building or underground. This means that there is no outside equipment exposed to weather and vandalism. All refrigerant systems are sealed, similar to household refrigerators.
- Geothermal systems are very flexible. They can be easily and inexpensively subdivided or expanded to fit building remodeling or additions. They are particularly well-suited to "tenant finish" installations.
- In commercial installations, systems can save money by recovering excess heat from building interior zones and moving it to the perimeter of the building. They can also save money by allowing management to isolate and shut down unoccupied areas of the building.
- Refrigerant Loop geothermal systems have several advantages over other geothermal systems. They are potentially more efficient than water loop systems. They require fewer feet of buried piping than other geothermal systems, have no freeze problems, and better heat transfer.
Disadvantages include the following:
- Geothermal systems tend to have a somewhat higher first cost than conventional systems. Open-loop systems have more potential problems than either conventional systems or closed-loop geothermal systems because they bring outside water into the unit. This can lead to clogging, mineral deposits, and corrosion in the system.
- Open-loop systems require a large supply of clean water in order to be cost effective. This often limits their use to coastal areas, and areas adjacent to lakes, rivers, streams, etc. In addition, there must be an acceptable method of returning the used water to the environment. This may be limited not only by environmental factors (such as no place to dump that much water), but also by local and state regulations.
- Many closed-loop systems use an antifreeze solution to keep the loop water from freezing in cold temperature conditions.
- Most antifreeze solutions have very low toxicity, but many produce CFCs and HCFCs, which add to environmental concerns. In addition, some antifreeze solutions increase fluid viscosity making the system work harder and adding to the cost of pumping.
- Refrigerant Loop systems have several disadvantages, including: Environmental issues related to the system's use of refrigerant, Corrosion issues since they use copper piping which needs anodic protection, and the need to maintain refrigerant temperatures within certain limits to keep from freezing or baking the ground, Difficulty in finding and fixing a refrigerant loop leak, should one occur.
- Since accessibility to terminal units is important in geothermal systems, architects and mechanical and structural designers must carefully coordinate their work.
- Each unit requires both electrical and plumbing service.
- Duct systems must be installed to bring outside air to each space.
- Secondary or backup heat sources are required in cooler climates.