When most people hear geothermal they think it is some new untested technology. The truth is, heat pumps are as well tested as any device you use everyday (there is one in your fridge for example) and using the earth for heat has been done since the paleolithic era. It took some time for us to connect the heat pump to the earth but even that has been going on for nearly a century.
|1824||Nicolas Léonard Sadi Carnot describes the heat pump in Reflections on the Motive Power of Fire.|
|1852||Lord Kelvin invents the heat pump.|
|1912||Heinrich Zoelly patents the idea of using the ground as the heat pump’s source.|
|c.1940||Robert C. Webber installs a home-made direct exchange geothermal system.|
|1948||Portland Oregon's Commonwealth Building is the first commercial geothermal heat pump system.|
|2004||An estimated total of 1,000,000 geothermal systems are installed world-wide.|
In today’s marketplace, consumers have many space conditioning system options to choose from. Only the ground source heat pump (GSHP) system was reported by the EPA in its April, 1993 Report: Space Conditioning, The Next Frontier (Report 430-R-93-004) as...
" the most energy efficient, environmentally clean and cost effective space conditioning system available today. "
That was 19 years ago so this statement is more true today because of significant advances in GSHP equipment efficiencies and improvements in ground coupling technology, while most conventional heating and cooling technologies reached their maximum efficiencies years ago (IGSHPA 2009).
In an average year, the earth absorbs roughly 47% of the energy delivered to its surface by the sun. This is 500 times more energy than the world uses in a given year and best of all, it is clean and renewable. Geothermal or Ground Source Heat Pumps (GSHPs) tap into this endless source of renewable energy by exploiting the fact that the absorption of the sun’s rays by the earth creates a near constant deep earth temperature throughout the year.
That means when outside air temperatures reach 100°F or even when they fall to -25°F, the temperature of the earth just a few feet below the surface stays nearly constant. The actual deep-earth temperature varies depending on soil composition and yearly average air temperature but it is always cooler than the air temperature on your hottest summer days and warmer than the outside air temperature on your coldest winter days.
Driven by the basic vapor-compression refrigeration cycle, GSHPs extract heat from the earth during the winter months and reject heat to the earth during the summer months through a ground connection. A normal air source heating or cooling unit (air-source heat pump, ASHP) uses the outside air as its source when heating or cooling a space.
Because of this fact, an air-source heat pump has to use a lot more energy to bring that air to the desired temperature. Think about it this way, boiling an ice-cube will take more heat and more time than boiling tap water. This is where the advantage of the GSHP system resides, using the near constant and moderate temperatures below the earth’s surface rather than using the extreme outdoor air temperatures as a heat source/sink.