I’ve noticed over the past couple years working on different geothermal projects and learning myself that many people are very intrigued about what exactly this technology is, how it works, and why it’s so efficient.  First off, what is geothermal?  Geothermal broken down means, geo = earth and thermal = heat.

This “earth heat” is used in different applications:

1. Geothermal Energy (Electricity) – From hot springs to hot rocks geothermal power plants are seen in 24 countries around the world.  Many people think of Iceland or Yellowstone National Park as visual representations of this heat below the earth.  According to the International Geothermal Association (IGA) the USA lead the world in 2010 with 3086 MW of installed capacity at 77 plants.  For reference, the Philippines had a capacity of 1,904 MW which created 18% of their countries electric generation, and Iceland created 575 MW.  Japan and many European countries also have geothermal power plants in place.  Generally the best locations are near tectonic plates.
2. Geothermal Heating and Cooling (Heat pump) – This is what encompasses our business.  When referring to geothermal heating and cooling in a residential home, a business or government building, we’re using the constant temperature of the ground to heat and cool these structures.  Here in Minnesota, we have a constant ground temperature of about 47 degrees.  In the winter, your geothermal loopfield circulates fluid through (HDPE) piping in the ground to extract heat which is transferred into your house.  When inside the fluid moves to the heat pump where it goes through the vapor combustion cycle to heat the fluid up hot enough to make your home comfortable.  This heat is then distributed through the building using traditional duct work or hydronic systems (radiant floor).  An important note on this is that existing ductwork in retrofit applications may need to be upsized to maintain 400 cfm per ton of heating load.  In the summer, this process is reversed transferring heat from inside your home and putting it back into the earth.

Why is this system so efficient?

One must understand in simple terms how conventional systems are rated.  A natural gas furnace rated at 95% efficiency means that for every 1 unit of energy put into this system, it creates .95 of energy in return.  This system cannot be more efficient than 100%.  Geothermal uses the advantage of the earth’s temperature to increase efficiency many times over.  This is best explained by understanding Coefficient of Performance (COP) or how a geothermal heat pump is rated.  According to the International Ground Source Heat Pump Association (IGSPHA), COP is a measure of heating efficiency for the heat pump equipment, expressed as the heating energy provided to the space (Btu) divided by the electric energy consumed to provide that heating (Btu).  In more basic terms, this means that if your geothermal heat pump is rated at COP of 3.5, the system is essentially 350% efficient.  For every 1 unit of energy put into the system, it yields 3.5 units.

References :

Oklahoma State University – International Ground Source Heat Pump Association.  ”Design and installation Guide.”

More to come  in the following weeks as we kick off our 2012 season.