Geothermal

Maryland does not have volcanic activity and the associated very high subsurface temperatures needed for electric power generation.  What Maryland does have, regardless of the season,  is a constant 57-degree temperature below a depth of about 10-feet and a geothermal (ground source) heat pump coupled to this moderate earth temperature happens to be the most energy-efficient, environmentally clean and cost effective space-conditioning system available.  Geothermal heat pumps offer both comfortable heating and cooling and have a long system life. 

Click to enlarge diagram.

HOW IT WORKS

Both ground-source (geothermal) and air-source (conventional) heat pumps heat and cool homes using a compressor-driven refrigerant cycle like those found in refrigerators.  Unlike oil and gas furnaces that generate heat through combustion, heat pumps generate heat (and cooling) by moving heat from one place to another, e.g. from the inside to the outside of a refrigerator or from the inside to the outside of a house.  Moving heat with a heat pump requires less energy than generating it through combustion, e.g. burning oil or gas.  In heating mode a heat pump transfers heat to the interior of the building and cooling to the outside.  In cooling mode the direction of heat transfer is reversed with heat transferred to the outside and cooling to the inside.

Geothermal “ground-source” heat pumps have two efficiency advantages over conventional air source heat pumps.  First, a conventional heat pump uses air as the heat transfer medium while a geothermal heat pump uses the natural heat storage ability of the earth and/or the groundwater as the heat transfer medium.  The thermal conductivity of ground-source  is 200 times greater than air allowing more efficient heat transfer and lower operating cost for geothermal heat pumps.

Second, the temperature difference between the desired indoor temperature and the outside temperature is less with a geothermal heat pump.  For example, maintaining a 70-degree indoor temperature on 20-degree day requires a temperature lift of 50-degrees for a conventional heat pump.  The lift for a geothermal heat pump coupled to the 57-degree earth is only 13-degrees, which enables the compressor to operate much more efficiently.  The situation is similar in the summer when a conventional heat pump can have a lift as high as 20-degrees, while there is no lift for a geothermal heat pump since the earth temperature is actually less than the desired indoor air temperature. 

A geothermal heat pump system consists of pipes installed in vertical well bores or buried in the  ground near the building, a geothermal heat pump, pumps to circulate water/antifreeze through the pipes and ductwork inside the building.  Geothermal heat pumps can also provide hot water for radiant floor heating systems and can assist in low-cost domestic hot water heating  Geothermal heat pumps  may be used in combination with solar photovoltaic systems to form geosolar systems, further reducing the electricity demand of a household.

GEOTHERMAL ENERGY IN MARYLAND

Geothermal heat pump systems are viable in just about any location in the state and can provide a consistent, reliable, and largely clean source of energy for residents.

Geothermal heat pumps can dramatically reduce Maryland’s energy costs.

  • Studies show that approximately 70 percent of the energy used in a geothermal heat pump system is renewable energy from the ground.
  • The U.S. Environmental Protection Agency estimates that geothermal heat pumps can lower energy bills by 30-40%.

Increased demand for geothermal system will create new jobs for Maryland.

  • Geothermal installations require professionals to help design and install the system, as well as contractors who can do the labor required to install the loops and the pump equipment. It can also create new business opportunities for HVAC companies.

Geothermal  FAQs

Why Geothermal Heating and Cooling?
How Do Geothermal Heating and Cooling Systems Work?
Will Geothermal Work Well at My Home?
How Much Do Geothermal Heating and Cooling Systems Cost?
What Will I Save on My Heating and Cooling Bills?
Are There Incentives and Financing Opportunities?
Where Can I Find a Geothermal Contractor?

Why Geothermal Heating and Cooling?

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, using 20%–50% less electricity than a conventional heating or cooling system. Geothermal systems also can provide water heating for household use. With excess heat from the geothermal heat pump's compressor can be transferred to the house's hot water tank. Additional benefits of the geothermal heat pump include:

Additional benefits of the geothermal heat pump include:

  • Humidity control—maintaining about 50% relative indoor humidity;
  • Space-efficient and easy installation—in new or retrofit situations, the hardware requires less space than conventional HVAC systems;
  • Flexible—“zone” space conditioning allows you to set different temperatures for the different areas of your home;
  • Long life—relatively few moving parts which are durable and highly reliable, with systems often lasting 20 years or more and warranties of 25-50 years for the underground piping.
  • Quiet—with no outside condensing units and no fans so there are no blasts of cold or hot air.

Increased demand for geothermal systems will create new jobs for Maryland.  Geothermal installations require professionals to help design and install the system, as well as contractors who can do the labor required to install the loops and the pump equipment. It can also create new business opportunities for HVAC companies.

How Do Geothermal Heating and Cooling Systems Work?

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.

It is important to note that geothermal heat pumps are different from air-source heat pumps.  Air-source heat pumps transfer heat to or from the outside air while geothermal, or ground-source heat pumps, exchange heat with the ground. This is much more energy-efficient because underground temperatures are more stable than air temperatures through the year.

A geothermal heat pump system includes 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.  Geothermal heat pumps can also supply the hot water required for radiant floor heating.

Will Geothermal Work Well for My Home?

Geothermal heat pump systems are viable in just about any location in the state and can provide a consistent, reliable, and largely clean source of energy for residents.

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, geology and landscaping;
  • The severity of your climate.

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, landscaping or reseeding may be required after system installation.  The size of the system will be proportional to the heating and cooling load with larger homes generally requiring larger loops than smaller homes.

How Much Do Geothermal Heating and Cooling Systems Cost To Install?

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. But don’t get sticker shock!  Rebates, tax credits, and exemptions are available from the Federal and state governments and utilities..  See the MCEC Residential Financial Incentives page for more details.    In addition, some cities and counties offer loans and property tax incentives for the purchase of geothermal heat pump systems.

How Much Will I Save on My Heating and Cooling Bills?

The amount saved in utility bills will be dependent on the system being replaced with saving highest for replacement of electric resistance, oil, and propane furnace systems and somewhat lower for conventional heat pump and natural gas furnace systems. The U.S. Environmental Protection Agency estimates that geothermal heat pumps can lower energy bills by 30-40%.  Most geothermal heat pumps systems recoup their costs in savings within 5 to 10 years.

Incentives and Financial Opportunities

Check our Financing and Incentives pages for information specific to:

Finding a Geothermal Contractor

It is important that you work with an accredited and experienced geothermal contractor who first can conduct a thorough analysis of your residential site.  Designing the system also calls for professional expertise.  Questions to ask when looking for a geothermal contractor include:

  • Are they licensed as a Maryland Home Improvement Contractor, electrician, HVAC, or plumbing contractor?
  • Does the contractor offer energy audit services or will you need another contractor?
  • What kind of site analysis and consultation services does the contractor offer prior to installation?
  • How many installations have they done over the lifetime of the company and in the last year?
  • What kind of certifications does their staff hold? Is someone on the staff certified by the North American Board of Certified Energy Practitioners (NABCEP) or the International Ground Source Heat Pump Association (IGSHPA)?
  • How will they help you with incentive and grant funding applications?
  • Does the contractor only install the system or do they also provide maintenance?
  • Are they a national organization or local to the state?

Use the MCEC Business Directory to identify Maryland companies who specialize in geothermal heat pump installations.

The International Ground Source Heat Pump Association and the Geothermal Exchange Organization also have directories of accredited geothermal heat pump professionals.