How a geothermal heat pump system works

[Karl]

A geothermal heat pump system uses the heat from ground water to heat or cool your home or business. It works by exposing your ground water to a refrigerant. The heat evaporates, and after going through a compressor, is condensed and blown into your home. To cool the home, the heat-extracted water is used as the source. Air is circulated over pipes containing that water, and blown into your home, with the extracted heat as a byproduct of the process.

"It's so efficient because we didn't make the heat. It's already there. You're not making heat, you're moving it," said Robert Branch, an engineer who designs energy-efficient systems. Electricity is a premium priced fuel. You are still using it, but you are using it more intelligently," he said.

From: Environmental efficiency no longer just about tree hugging; it's about saving money - poconorecord.com - The Pocono Record

[GreenerPeople]

Are there any downsides to this? Could heavy usage cause localized cooling of the ground?

[Karl]

Originally Posted by GreenerPeople

Are there any downsides to this? Could heavy usage cause localized cooling of the ground?

Some of the downsides to geothermal energy use have been discussed here:
(CR4 - Comment: Re: Geothermal Power Generation - The sleeping giant?).

However, I have not encountered the idea of possible localized cooling identified as a potential impact. This may be a question of the scale of the use; however, these systems can be designed for buildings as both heating and cooling, in which case they "use available heat in the winter and put heat back into the ground in the summer"
(Geothermal heat pump - Wikipedia, the free encyclopedia)
(Geothermal Heat Pumps).

[Karl]

Some more views and perspectives on geothermal energy, from...

EnergyRefuge.com - June 07, 2008: Geothermal Energy: Not a New concept

We struggle with the concept of burning through a finite supply of fossil fuel for our energy needs when the very core of our own planet is a nearly inextinguishable ball of pure heat energy. The logic behind the concept is incredibly simple: By pumping water down into the super-heated dry rock underground, massive amounts of dry steam and flash steam are released in the process. It is the energy in this steam that can be harnessed much in the way early locomotives and ocean-liners made use of heated water.

The concept of tapping into this limitless energy reserve is nothing new. In fact geothermal power production traces its roots back to the early 1900s when the first geothermal generator proved successful in Italy. Bathers have been exploiting the benefits of hot springs for countless centuries before that even. In the 104 years that followed early attempts at transferring geothermal heat into electricity, we’ve made leaps and bounds in terms of world-wide construction of geothermal power plants and yet sadly, as of last year, geothermal power accounted for a mere 1% of the world’s energy.

The good news is that long-term studies of the environmental effects of tapping into these energy reserves are quite positive. Not only does pollution byproduct pale greatly in comparison (some 5%) to levels emitted by even our cleanest fossil fuel production facilities but even more impressive is the fact that when left to recuperate, the earth’s mantle will recover it’s lost heat thanks to near limitless heat reserves.

Experts predict that the next fifteen years will witness a massive shift in fossil fuel alternative development by focusing efforts on the energy below the earth’s crust. To provide a sense of this potential, consider the following: According to a recent report from MIT, there is enough heat energy in the hard rocks seven miles below the United States to supply current energy needs for the entire world for 30,000 years.