Between absorbing the sun's energy and the heat released by the decay of minerals buried deep, the earth generates twice as much power as humans currently consume, making it a very attractive sustainable energy source. Unfortunately, most of this power is hard to reach on an industrial grade level. For the home use, however, geothermal power is becoming a readily available alternative energy source to both heat and cool the home.

THE BASICS

Geothermal energy is accessed through drilling into the earth where heat is stored and bringing it to the surface. While geothermal power plants drill wells as deep as three miles to tap into the massive amounts of energy, home units require a lot less power and simply have to break through the frost line of the earth's crust (roughly six feet deep) where the temperature stays constant all year round at about fifty degrees.

Home geothermal units consist of four main parts: the piping, the heat pump, the anti-freeze solution for the piping, and the air handling system.

The Piping

In most geothermal heating systems, a long continuous loop of piping is buried below the earth's frost line. It is attached to the heat pump and carries the anti-freeze solution through the earth to pick up or release heat. It is by far the biggest part of installing a geothermal heating system and does require a good deal of work to bury.

The Heat Pump

The heat pump is the main unit for a geothermal heating system and is kept indoors, usually in the basement or crawlspace. About the size of a refrigerator, the heat pump moves the anti-freeze solution through the underground pipes to transfer heat. Geothermal power is currently only used to heat and cool homes and does not generate any electricity. As such, the heat pump does require an external power supply. The electricity consumption, though, is very little, making geothermal heating systems vastly more cost effective than conventional boilers and air heating systems.

The Anti-freeze Solution

The anti-freeze solution is what actually heats and cools a home and is cycled through the underground piping by the heat pump. In the winter, the fluid absorbs heat from the earth and releases it into air handling system. In the summer, a reverse valve is switched on and the fluid carries heat from the home into the earth, using it as a heat sink.

The Air Handling System

The air handling system transfers heat between the anti-freeze solution and the house. It is attached to your home's ductwork and circulates the heated air throughout the house. If your home does not have existing ductwork, it will need to be installed if you wish to use geothermal heating.

COST

The cost of installing a geothermal heating system depends on many factors that include the size of system needed, the depth it needs to be buried at, contractor rates for drilling in your area, and the installation of ductwork if your home doesn't already have it. The system itself can cost as low as $3500, comparable to conventional heating systems. However, the cost of drilling can range from $5,000 to $30,000 depending on how the piping will need to be laid out. In the US, eligible geothermal heating systems can receive 30% of the cost of the system (including labor and installation) back in tax credits.

With savings of up to 50% over conventional heating systems, geothermal heating installation costs can usually break even in three to ten years. In addition, many systems can be purchased with a desuperheater, which also heats water when the system is heating the home, saving you even more money. Being indoors, the mechanicals are protected from the weather and last around twenty five years whereas the piping itself have a lifespan of over fifty years, making geothermal heating systems a very good long term investment.

PROS

- Cheap and reliable heating and cooling system

- Water can be heated for free with the installation of a desuperheater

- The initial cost is usually paid off between 3 and 10 years from the savings

- Long life span - around 25 years for the heat pump and over 50 years for the piping

- Viable in more areas than solar and wind power, which are more dependent on the local climate

- Sustainable and earth-friendly

CONS

- A larger scale setup than solar or wind power systems as due to drilling and digging

- Requires ductwork to be installed if not already present

- Requires another electric source to power the heat pump

For the ambitious types that want to install their system themselves, I would recommend you pick up Geothermal Heat Pumps: A Guide for Planning and Installing. It's a comprehensive guide on picking out and installing a geothermal system for the home.