Chapter 9: Advantages and Disadvantages of Geothermal Energy

Air temperatures vary. In some locations, seasonal differences are great. However, four to six feet underground, temperatures are relatively consistent year-round, and geothermal energy harnesses this heat.

To scrutinize geothermal versus oil heat, it’s necessary to understand geothermal basics.

Geothermal Essentials

Geothermal systems operate because the earth’s temperature remains stable all year long a few feet underground. Temperatures vary by location but are generally between 45 and 75 degrees Fahrenheit.

Geothermal pumps provide both heating and cooling. Some also warm household water. Geothermal systems are effective in most climates, but sometimes homeowners may keep a back-up heating source for extremely cold weather, especially if their geothermal system is a bit smaller.

The different types of geothermal pumps are:

  • Closed loop. In a closed loop pump, antifreeze runs through tubing that is underwater or underground. The system lies vertically or horizontally.
    When the antifreeze reaches the house, a heat exchanger moves heat between the antifreeze and liquid in a heat pump. Heat travels through the building in ductwork or radiant heating systems in floors or walls.
    Horizontal arrangements are often least expensive for homes. Two pipes stretch four to six feet underground. In vertical systems, pipes run 100 to 400 feet into the earth.
    When a pond or lake is nearby, a low-cost closed loop system is possible. An underground pipe connects the house to the water source. The pipe is coiled at least eight feet below the water’s surface.
  • Open loop. An open loop system requires surface water or a well. Water goes from the source, through a heat exchanger, throughout the house and back to its point of origin.
  • Hybrid. In some cases, geothermal systems are combined. Other times geothermal heating works together with an air source. Hybrids are most useful in regions where cooling is more important than heating.

Assessing Geothermal Energy

While efficiency and cost are important factors to consider, location is also an issue when evaluating geothermal systems. Like other heating systems, there are advantages and disadvantages of geothermal energy. Deciding if this type of heating works for you involves taking all the factors into consideration and weighing the pros and cons.

Efficiency

All heat pumps, including geothermal models, report their efficiency through a coefficient of performance, or COP. This compares the number of units of energy used to create power to the number of units of power actually generated.

Usually, for every unit of power needed to run a geothermal pump, the mechanism produces three to five units of energy. This means the COP of most geothermal pumps is between 3 and 5.

Geothermal systems are 50 to 70 percent more efficient than other heating methods. They also cool 20 to 40 percent better than standard air conditioners.

Geothermal systems are 50 to 70 percent more efficient than other heating methods. They also cool 20 to 40 percent better than standard air conditioners.

Cost

Geothermal systems are more expensive to install than air heating systems. Pond or lake geothermal versions are less costly if a water source is convenient. If there is no water source readily available, the next option is to use the horizontal option to keep costs as low as possible.

However, due to lower annual operating and maintenance costs, homeowners recoup their investments within five to 10 years. In addition, some federal and local government agencies offer incentives that bring the initial price down significantly.

Homeowners recoup their investments within five to 10 years.

Geothermal systems have long lives as well. Indoor parts are good for about 25 years, while underground components last at least 50 years. These systems also generally have low operating and maintenance costs.

The expense of heating and cooling with geothermal energy varies by model and capacity of the pump. For 2016 Energy Star certified pumps, the national average annual cost to run ranges from just under $100 to less than $600.

Disadvantages

One of the primary disadvantages of geothermal energy is that homeowners must have sufficient room to install the system, and there is an expensive upfront cost.

However, even with enough land, setting up the equipment disturbs the environment. Geothermal heating is also a relatively new process, so there are comparatively fewer installers than with more established systems.

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