Over the past year and more, there's been a lot of buzz about geothermal heating as the next big thing that's going to save us billions in energy costs in the future. The latest article to jump on this bandwagon, "Looks Like a Hot Deal" by Christopher Gearon, just turned up in the Washington Post today.
The science behind geothermal heating is that whatever the vagaries of weather on the earth's surface, the temperature of the earth just a few feet below the surface remains remarkable stable throughout the year. By running a sort of variant on heat-pump technology (drawing and concentrating warmth from a lukewarm medium), it's possible to heat buildings. Sounds very clever, doesn't it? I'm impressed by the idea, and it's not just theory; Gearon, the writer of this piece, has converted his home to geothermal at a net cost to him of about $10,000, with the promise of no future heating bills. Further, there are a number of organizations out there touting the benefits of the technology.
The process is accomplished by various means, but the most common and feasible is to run two or more closed-loop pipes into the stable-temperature subsurface, either horizontally (in which case they can take up most of the ground around the house) or vertically (in which case they may go as deep as 325 feet).
Has anyone, I wonder, considered the effect of all this heat exchange going on just below the earth's surface? It's OK for one or two houses but if geothermal became the norm, or was widely used in certain parts of the country, common sense tells me there's a good chance that the temperatures of that below-surface soil would start to change over time, with potential unknown effects on wildlife, agriculture, and even our climate. It's possible, of course, that the saving in heat generation gained by not running a fossil-fuel burner could offset some of these effects. But someone ought to consider it.
Other means of setting up a geothermal system (see the Washington Post article, they're outlined there) involve water as the heat exchange medium. Using a pond or lake would seemingly raise the same question of gradual warming; while using an open loop that would suck up groundwater and circulate it through a system before returning it to the ground seems to have even more potential for warming, and for polluting groundwater -- besides, don't we have enough demands on our aquifers already, without draining off more (even temporarily)? Incidentally, the pipe used in all these systems is PVC, but we've already seen some problems of deterioration with HDPE or PVC pipe in some plumbing installations...will it really last or will it need to be reinstalled every 10, 20, or 30 years? So I'm cautious. The idea is worth exploring, even worth constructing some test systems as Gearon has, but there are some longer term ramifications to be considered.
Other "new science" has evoked similar concerns about later fallout -- for example, the idea that we counter global warming by pumping the upper atmosphere full of sulphur particles or dusk (seriously!) without thinking of how that might affect our climate or even our mood. On a more mundane level, many developed societies years ago mandated low-flow toilets as a means of reducing water consumption. I'm not sure it accomplishes that (often, I'm told, it requires multiple flushes, so where's the gain?). Even if it did, did anyone think about whether the new technology creates enough flow to wash sewage all the way down and out to the sewer (or septic field), or will we be confronted, in another ten years or so, with the need to clear or replace clogged sewer lines?
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