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Starting with Geothermal

October 27, 2009
Geothermal installation

Geothermal tubes laid horizontally


Geothermal Can Generate Big Savings vs. Fossil Fuels

As an environmentally-minded homeowner who is also interested in lowering the energy costs for my active home, I have spent the past18 months researching various alternative energy solutions for my home, and interviewing contractors for these solutions.  The next several posts will summarize my experiences with the leading renewable energy options available.

First on my list to investigate was geothermal.  Of all of the major alternative technologies, none seemed as practical and efficient as geothermal.  I had heard about some local geothermal energy projects (and my then 5th grade son had even done a school report on geothermal), but exactly what it was and how it could be applied in a residential setting was a mystery- and no it doesn’t require hot springs or magma, or a property adjacent to Yellowstone.

There’s no shortage of information and media touting the benefits of geothermal. Check out this great video piece that appeared on CNBC.

My first experience with a geothermal contractor occurred after driving past a newly constructed home.  I noticed a sign out front that said “geothermal installation by “xxx Energy.  I called xxx Energy to ask what they had done at this home and whether it was something that I could do on my property.  I didn’t get much in the way of details of installation, or even anticipated savings, but what the contractor was more than willing to quote me was a $45,000 project to retrofit my home.  This was a brief conversation.  At the time, oil was more than $125/barrel and this contractor seemed to know that he didn’t need to provide much of an explanation of exactly what geothermal was in order to protect homeowners from rapidly rising oil prices.  But I needed to get a better understanding of exactly what geo-thermal is, how it helps the environment and how it would help me to save on energy expenses.

So here’s what I learned by scouring the Internet and ultimately meeting and speaking to multiple contractors:

1.  Geothermal, in virtually all residential and small business applications, does not access volcanic gases or any other “underground geyser” or hot air supply.  In fact, geothermal is much simpler than that.  It is a simple energy exchange.  When the air is cool above the ground (like in the winter in the North), about 3 feet below the ground, the temperature remains above freezing, sort of at a constant 50 degrees.  And when it’s hot above the ground, guess what?  It’s still 50 degrees about 3 feet below the ground.  So in its simplest form, all geothermal energy consists of is taking the 50 degree temperature below the ground and moving to the inside of your house.

2.  So how to do this?  How do you get the 50 degrees outside to come inside your home?  Surprisingly, the solutions are all fairly easy to understand and mostly low-tech.  In fact, geothermal techniques have remained largely unchanged for almost 30 years.  The way to extract that energy from the ground requires that a tube (usually about 210 feet long) is either laid under the ground horizontally at least 3 feet under the ground (the tube can be bent and curved to accommodate smaller pieces of land) or dropped straight down a 200-300 foot well (the same type that is drilled for well water).  The tube is injected with water (and sometimes a little antifreeze), and the the water is pushed through the tube, and returned back to the house.  If the water was 70 degrees when it started (in warm climates or summer in the North), when it comes back it should be no surprise that it is now 50 degrees.  The energy of the ground was transferred to the flowing water, and the efficiency of this transfer is extremely high.  There are alternate methods of constructing and laying out these tubes, with the most popular being a straight vertical “well” being drilled the full 210 feet for the transfer.  There are costs and benefits associated with each of these applications that will be posted later.

3.    Once the 50 degree water is back at your house from its journey under the ground the next problem is how to get it to cool or warm your home.  Again, a simple solution has been developed that takes the 50 degree water and sends it through a “new” air handler for your home that contains several baffles (folds) that distribute the water as air is blown over it.  If the air is 80 degrees and the water is 50, the air is cooled, providing air conditioning.  If the air is cold (25 degrees), the cold air is warmed to 50 degrees, providing heat.


How Geothermal Heat Exchange Works

4.  For air conditioning, the only energy that is needed for geothermal is the electricity for the water pump and the air handler.  For heat, a small backup heating system may be needed to push the temperature from 50 to 65-70 degrees, but the energy needed to do this is far less than that required to heat a home from 20 degrees.

5.  Geothermal can be applied in all 50 states.

6.  It can be done on virtually any sized plot of land.


Vertical Drilling on Smaller Plot of Land

7.  The equipment required replaces polluting air conditioning condensers that hog electricity.

8.  Due to the simplicity of these systems that are not prone to breakdown and can last up to 30 years with little to no maintenance.


Geothermal Air Handler Looks Like a Typical Air Handler

9.  The amount of savings associated with geothermal systems can be substantial.  The number one category of energy consumption for a home is heating and air conditioning.  Geothermal systems are generally expected to reduce energy consumption for cooling by approximately 80% (energy is still required to run the water pump and the air handler).  The efficiency of geothermal for heating systems varies, but significantly reduces dependence on oil, gas or electric heating because the home only needs enough energy to increase the temperature from 50 degrees to 65-68 degrees.

Some more geothermal information…

Coming up next… Geothermal costs, tax incentives and return on investment.. and who is geothermal right for?

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