Friday, October 30, 2009

Fantastic Future Friday: Geo-Thermal

This is the fourth part of my three part series (It’s a Douglas Adams type thing) on Alternative Energy.

Residential and Commercial Geo-Thermal Heating and Cooling:

Way Ahead of Humans in the use of Geo-Thermal Cooling

Last Friday I talked about using solar heating for hot water generation and heating a home in the winter. A big use of power is the opposite, cooling a home during the summer months.

The simplest Alternative to the big compression Air Conditioners is right underneath our feet, Geo-Thermal.

The basic idea behind Geo-Thermal hvac (Heating and Air Conditioning) is that the Earth between 10 and 40 feet underground stays at a constant temperature between 50 to 73 degrees in most parts of the world.

In the summer months it’s much easier to cool air that is that temperature to the standard 68 degrees than the outside air that is in the mid 80s to 100 degrees.

Geo-Thermal Air Conditioning also has the advantage that it has few or no moving parts so once it is installed it’s easy to maintain.

The simplest Geo-Thermal Air Conditioning system is so simple that prairie dogs have been using it for 1,000s of years. Since humans like to use fancy names when it is installed in a home it is called an Earth-Air Heat Exchanger.

The only components to this system are a tube between 4” and 24” buried 10 foot underground. It is open to the outside air at one end and either attaches to an existing central air unit, or uses a solar chimney to draw the air up into the home.

The only draw back to these systems is when the moist warm air is drawn into the tube and cooled down the moisture condenses and can cause mold. So the air needs to be heavily filtered. In some places the humidity isn’t high enough to cause this problem (lucky bastards) and the increased amount of fresh air in the home actually decreases indoor mold and mildew. In other areas with high humidity and a high water table (harder to drain the water) it is the biggest consideration in the system.

A more complex system is to use pipes buried 10 foot underground filled with saltwater and pumped into pipes in the house where fans blow across them to provide cool air for the home. This is good for the people in high humidity areas as they don’t have to worry about the mold.

The most complex system is one that uses existing heat pump (regular AC) technology, but instead of using the outside air to either pump out the excess heat in the summer or the cold in the winter it uses the water that has been pumped underground to heat or cool the unit.

The energy and cost savings from these units are phenomenal, a simple Earth-Air Heat Exchanger can pay for itself in the first summer it is used (depending on the climate).

As I talked about in my last post of this series anything that reduces peak power demands for electric utilities means they can build smaller more efficient power plants. If new homes are built to take advantage of Geo-Thermal heating and air conditioning, and existing homes get systems installed, it takes the load off the power plants during the high temperature days when they are taxed the most.

Besides the cost and energy savings that small-scale solar bring to residential customers, the flexibility it brings to the power grid can’t be understated. By decreasing the demand on the existing power grid it frees up city planners to look at other considerations like quality of living and better access to parks and recreations, instead of having the number one priority be how do we get power to theses people?

Having our homes less dependent on the existing power grid will lead to a Fantastic Future.


Stephanie B said...

Great post!

There is another form of geothermal energy (in the form of water heated underground through natural volcanic action) is used effectively costlessly in Iceland and is the primary source of power in Norway (which then can export the bulk of its' oil).

What I like about what you've described is that it can be used anywhere, even in cold climates (as 50-73 degree air is also easier to warm than -20 to 30 degree air). By bringing the air temperature (either through exposure to a water loop or directly from underground) to a temperature within a few degrees of comfortable, heating/cooling becomes a synch.

askcherlock said...

This is such a moral imperative. Unless we start delving into alternative energy supplies, we should be considered irresponsible and negligent.