Geothermal

The most readily developed source of geothermal energy in Maryland is the geothermal heat pump. Also known as the ground source heat pump, it is a highly efficient renewable energy technology that is gaining wide acceptance for both residential and commercial buildings. Geothermal heat pumps are used for space heating and cooling, as well as water heating. Its great advantage is that it works by concentrating naturally existing heat, rather than by producing heat through combustion of fossil fuels.

Hybrid "geo-solar" systems combine heat pumps and solar panels for clean electricity and heating and cooling.

The geothermal heat pump takes advantage of the constant temperature of the ground – cooler than the air above it in summer, warmer in winter—by transferring heat stored in the Earth or in ground water into a building during the winter, and transferring it out of the building and back into the ground during the summer. The ground, in other words, acts as a heat source in winter and a heat sink in summer.

Geothermal Heath Pump systems include three principal components:

Earth Connection: Using the Earth as a heat source/sink, a series of pipes, commonly called a "loop," is buried in the ground near the building. It circulates a fluid (water, or a mixture of water and antifreeze) that absorbs heat from or radiates heat to the surrounding soil, depending on whether the ambient air is colder or warmer than the soil.

Heat Pump Subsystem: 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.

Heat Distribution Subsystem: Conventional ductwork is generally used to distribute heated or cooled air from the geothermal heat pump throughout the building. Many residential systems are able to transfer excess heat from the geothermal heat pump's compressor to the house's hot water tank, and even continue to operate to heat water when the heating and cooling systems are turned off.

Benefits

• Save electricity. Geothermal heat pumps use 25%–50% less electricity than conventional heating or cooling systems. Geothermal heat pumps can reduce energy consumption—and corresponding emissions—up to 44% compared to air-source heat pumps and up to 72% compared to electric heating with standard air-conditioning equipment.
• Improve humidity control. Geothermal systems also improve humidity control by maintaining about 50% relative indoor humidity, making them very effective in humid areas, like the mid-Atlantic and Maryland.
• Flexible and space-efficient to install. Geothermal heat pump systems can be installed in both new and retrofit situations. Because the hardware requires less space than that needed by conventional HVAC systems, equipment rooms can be much smaller. GHP systems also provide excellent "zone" space conditioning, allowing different parts of your home to be heated or cooled to different temperatures.
• Long life. Because GHP systems have relatively few moving parts, and because those parts are sheltered inside a building, they are durable and highly reliable. The underground piping often carries warranties of 25–50 years, and the heat pumps often last 20 years or more.
• Quiet. Because they have no outside condensing units like air conditioners, there's no concern about noise outside the home – and it works without fans, so there are no blasts of cold or hot air.

Considerations

• Upfront costs. Geothermal systems cost more than traditional HVAC systems – sometimes twice as much for a comparable unit. Add to that the cost of installing the geothermal loops, and the cost of a full system runs tens of thousands of dollars. Still, most systems recoup their costs in savings within 5 to 10 years.
• Disruptive drilling. Depending on the site, the geothermal loops can be installed vertically, sinking down into the ground, or horizontally, laid out flat beneath the surface of the ground. In either case, homeowners may need to rip out existing landscape to accommodate the system.

Getting Started

Invest in an Energy Efficiency Audit

This audit is a series of simple tests that will determine how energy efficient your building or home is. These tests should be conducted by a certified energy auditor and typically are conducted in a single day. The results of the audit will be able to tell where you are inefficiently using energy and what updates and improvements you can make.

Site Analysis

Geothermal heat pump systems are not do-it-yourself projects. To ensure good results, the piping should be installed by accredited professionals. Designing the system also calls for professional expertise: the length of the loop depends upon a number of factors, including:

• Whether you use vertical or horizontal loops
• Your home's heating and air conditioning load
• Local soil conditions and landscaping
• The severity of your climate.

Larger homes requiring more heating or air conditioning generally need larger loops than smaller homes.

Finding a Contractor

Search the MCEC resource database to find qualified geothermal heat pump installers and drillers.