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Geothermal Heating and Cooling

Geothermal Heating and Cooling is relevant to the home owner because it is simple technology and can be installed on just about any home property with a yard. It can also be an important feature that reduces your cooling and heating bill by up to 70% as well as increasing the value of your home.

What is Geothermal Energy?

Geothermal originally comes from two words - "geo" meaning earth and "thermal" meaning heat. Geothermal energy is achieved by using the earth's natural heat to heat water, heat buildings, boil water to turn turbines generating electricity, and cool buildings. Geothermal energy can be used on a large scale, such the largest geothermal power plant Geysers Dry Steam in California, to being used in hot tubs for therapy and relaxation. For home owners, a geothermal heat pumps can be installed to moderate temperatures in the home using the earth's stable temperatures.

Geothermal Heat Pumps

A geothermal heat pump is a simple system that pumps fluid through a flexible tube that is buried in the ground into the house. During the winter, the earth remains warm, so warm fluid is pumped out of the ground and into a device similar to a furnace where the warm fluid is converted to warm air, and then circulated through conventional heat ducts within the home. During the summer, when surface temperatures are hot, the ground remains a constant 55 degrees. So cool fluid is pumped out of the ground and converted to cool air, which then circulated throughout the house. The side benefit of installing a geothermal heat pump is that it can also replace your water heater.

Geothermal heat pumps' tubing will be dug vertically very deep in the ground around your home if you have a small yard. Also, if your surveyor determines that you have bedrock under your home, more holes may need to be drilled to allow for more tubes. Otherwise, if you have more than a couple of acres, the tubes will be installed more shallow and horizontal. Cost-wise, it is less expense to make shallow trenches, because the equipment needed is more common.

Geothermal Energy history

Geothermal heating has been used throughout pre-historic times for heating, bathing and minerals. The oldest known hot spring used by humans was found in China and dated back to the third century BC. In the first century, the Romans channelled hot geyser water through the city to various pools and charged for public use.

Throughout more recent history, beginning in the 1800s, various applications of thermal energy had been innovated. In 1892, America's first district heating system in Boise, Idaho was powered directly by geothermal energy, and was soon copied in Klamath Falls, Oregon in 1900. A deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the same time. Charlie Lieb developed the first down-hole heat exchanger in 1930 to heat his house. Steam and hot water from the geysers began to be used to heat homes in Iceland in 1943.

The concept of the heat pump was first developed in 1852 by Peter Ritter von Rittinger, an Austrian engineer. He discovered that it is far easier to move and upgrade heat utilizing the refrigeration process than to create heat. Using a heat pump, von Rittinger developed an extremely reliable and long-lasting system, which operates care-free for decades with filter changes being the only maintenance - we've all heard of Grandma's deep freeze, still running smoothly "over 30 years, non-stop".

The earliest application of the heat pump to a ground source (geothermal) heating and cooling system dates as far back as 1912, when the first patent of a system using a ground loop was recorded in Switzerland. It was not until the 1970's that geothermal systems gained widespread market acceptance, principally in Eastern Canada.

By the mid-1980's advances in heat pump efficiencies and operating ranges combined with the introduction of high density polyethylene pipe (HDPE) in the 3/4 inch inside diameter size (perfected by the natural gas distribution industry) resulted in a breakthrough practical geothermal system.

Geothermal Home Heating and Cooling

Geothermal heating systems are also known as ground-source heat pumps that draw a steady supply of heat energy from the soil and move it through a home or building. The three major benefits of this type of system are its energy efficiency, low cost and ability to lessen pollution. Ground-source heat pumps generally move heat using a network of tubes called "closed loops." These loops (vertical or horizontal) contain either water, refrigerant or an anti-freeze solution which run through the ground and absorb the earth's energy to deliver heating and cooling directly to the house via heat exchangers. Once the liquid is heated, they are pumped back through the system into the house. After passing through the home and transferring its energy, it goes back to the loop system and the process is repeated. During summer, the system works in reverse mode to provide cool air to homes.

Geothermal Heating system

A geothermal heating system includes several simple components: a trench, polyethylene tubing, a heat pump, a liquid to air heat exchanger, air ducts or hydronic floor tubing to distribute the heat through the home.

Fresh poly tubing bundle.
geothermal tubing bundle

Trench being dug.
geothermal trench being dug

Coiled poly tubing laid in trench.
geothermal tubing in trench

Geothermal pump and conditioned air producer
geothermal heat pump

Advantages of Home Geothermal Installations

  • Tubing for heat conduction can be placed shallow underground.
  • Geothermal systems use shallow ground that remains at a constant temperature of around 68F degrees year round.
  • The Department of Energy has determined that shallow geothermal systems can save as much as 70% off heating and cooling costs.
  • The Environmental Protection Agency described geothermal heat pumps as "the most energy efficient, environmentally clean and cost effective space conditioning systems available."
  • Although they are more expensive to install than traditional systems, savings are typically realized within two to five years of a project being completed. Savings come quicker in bigger buildings.
  • For large buildings that used heating oil, consider that one unit of energy generated by a heating oil boiler costs an average of $49, while the same amount produced by a geothermal heat pump costs $6 to $8.
  • With no transmission lines needed, a geothermal system puts limited demand on the grid. If low consumption geothermal pumps are powered by renewables, such as solar and/or wind, then no load is placed on the grid at all. Also, the sizing of your solar module would be much smaller.
  • Geothermal systems also more reliable than solar or wind power because it's not weather-dependent.
  • Geothermal systems produces no greenhouse gas emissions.
  • Because the technology uses no evaporative cooling systems, its water usage is nil.
  • The majority of equipment used in geothermal heat pump systems is hidden. Pipes and tubes are buried.

Government Incentives for Geothermal Installations

Up to $2000 tax rebate is available.

Geothermal Power Plants, Geothermal District Heating, and Geothermal Utility Scale Power

Large scale geothermal power plants have been in use for many decades. They tap into hot spots in the earth that have water running over hot rocks. Some places the water finds its way to the surface in the form of hot springs. In other places drilling is needed to get to the hot spot.

geothermal power plant
Geothermal Power Plant

Geothermal district heating can be created where an underground source of hot water is nearby a town. All or most of the buildings in the town can take advantage of the heat source. Several of these have been in place for many decades. If the heat source is strong enough, steam for turbines can generate electricity.

Summary

The Energy Department recently suggested that "federal policymakers seriously consider aggressively deploying geothermal heat pumps nationwide, with programs commencing as soon as possible, given the need to rein in our nation's energy consumptions and carbon emissions, while at the same time stimulating our economy out of its most serious downturn since the Great Depression."

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