Geothermal (Ground-Source) Heat Pumps (GHPs) make use of a completely different set of principles than the kind of geothermal we commonly discuss. Where the latter relies on the transfer of thermal energy from one fluid to another, like an egg placed in boiling water, the former relies on the principles of refrigeration, i.e., the evaporation and condensation of a substance in an enclosed space.
But considering that many people are unaware of this, how large an effect does public ignorance have? It’s huge, according to the U.S. Department of Energy, which dubs this effect a GHP “energy crisis” in their recent report:
The basics of GHP technology have changed very little over the decades but a geothermal identity crisis has been detrimental to fostering awareness, understanding, and acceptance of the technology. Depending on the perspective, GHPs have been cast as an energy source by many names (renewable, geothermal, solar, earth, alternative, recycled), as energy efficiency or energy conservation, or as an option within a broader category such as utility demand-side management.
There’s plenty to get excited about in GHPs, whose basic concept is that even very cold water or cold air contains an appreciable amount of energy that be extracted and moved very inexpensively.
In the coming month or two, I hope to corral GHP expert and professional consultant Mark Metzner for a webinar on the subject. I’m sure listeners will be surprised and delighted to learn how simple, inexpensive and ridiculously underused this technology is. More soon.
2 comments
Whenever I have mentioned Geothermal heat pumps to architects they have been very dismissive. Takes up too much room, very liable to breakdown and expensive to fix have been their comments. Does anyone have chapter and verse to correct these views?
Umm while the careless and incorrect use of language “on the street” and even in all kinds of media (which selectively exercise their responsibility to do some minimal communications-due-diligence…) is ubiquitous, perhaps in this more specialized forum, a more semantically correct approach is appropriate…
Geothermal means “heat from the earth”. When applied to the area of space heating for human occupancy, i.e. temperature of 25C, if the heat from the earth does not flow by its own energy, it is not geothermal. Geothermal is available in Iceland, Hawaii, and other places where the sub-surface temperature within “practical reach” of the surface is 40C plus. Everywhere else requires pumping via external high-grade-energy input.
An analog would be to call a pumped well an Artesian. True enough, the water pours out on the surface – but not without pumping via external energy input.
GSHP is simply the standard refrigeration cycle reversed. The “amazing” COP is arrived at by comparing the space-heating-energy provided by the medium-tech-gizmos divided by the space-heating-energy provided by a low-tech resistance-heater.
The barriers to adoption that GSHP faces demonstrates that people are doing research, due diligence, and penetrating the “conventional wisdom” (industry-bullshit).
When one considers all the factors, including embedded energy and upfront purchase and installation and ongoing maintenance and eventual replacement costs of the hardware, and the energy source (in USA Inc. electricity is predominantely coal-fired), and the inappropriateness of using high-grade energy to perform low-grade functions, and the susceptibility of relying on a single energy-source (at a time of increasing grid fragility) for all lighting/heating/etc., it raplidly becomes self evident that GSHP is an unsustainable technology unsuitable for general deployment.
Certain niche applications – like where no natural gas (or biomass) is available may be judged appropriate after taking into account full cradle-to-grave analysis of the available options.
My recommendation is to forget about GSHP and ensure the project maximizes passive solar, massive insulation, LED lighting, and install microCHP (biomass or NG) plus some local electrical energy storage, DC distribution, multiple mini-inverters
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