At university, I knew a chap who, when strapped for cash, would go out and spend his last few pounds and shillings on a hat or some other such unnecessary paraphernalia. In the midst of the credit crunch, the subprimes and a dollar in free fall, we are doing likewise—acquiring, not a hat, but a holiday home in the Euro zone. While house hunting, I came across some rather intriguing notions about ways of heating and cooling your home in a particularly ‘ecological’ fashion.
The system is a variant on geothermal energy—taking heat from the ground. But in these ‘air geothermal’ systems the energy is taken from the air. In the winter, these heat pump-based ‘solutions’ take cold air from the outside and blow hot air into your living room. I must say I was perplexed. As a geophysicist, I like to take a ‘black box’ approach to such problems—I mean, whatever goes on inside the heat pump, calories, BTUs or whatever have to be added to raise temperature.
Yes indeed, say the geothermologists—but these calories come from the cold air on the outside. The result is that the system blows even colder air out to the outside, extracting its calories and warming up the inside of your home. On one blog posting, someone working for an air geothermal company claimed that useful heat could be extracted from air as cold as - 45°C!
When I got home I sat myself down in front of our old fashioned fire in a comfy chair, poured myself a drink and got thinking. These systems are quite incredible—not only do they give you calories for free—but they actually cool the atmosphere down—an instant solution to global warming! I had to check this out even though I was getting a bit sleepy by then. I decided to do a simple experiment...
We all have heat pumps in our refrigerators—and so with a few doors open, some plastic sheeting to duct cold air here and hot air there, I quickly turned our fridge into a geothermal heat engine. Next I ran around the house and turned every electrical appliance (including my wife’s bedside light) off. Then, with a Maglite, I shot down into the basement to check the electricity meter. There it was, incontrovertible evidence of energy saving—the meter was turning slowly around in the wrong direction! Electricity was being pumped out of the cold air and back into the grid. Just to check, I ran outside under the sheets with a handy thermometer - minus 50°. Wow! I thought, I didn’t know that our jam thermometer went down that low! And then I woke up...
My immediate reaction to hearing this tale of free energy was—no way! I studied physics a long time ago and vaguely remember some stuff (was it the first or second law of thermodynamics?) that says that you need a heat source and a cold heat sink to use thermal energy. I mean if there was free energy to be had from cold air, then there would be dirty great big air thermal heat pumps providing us with electricity wouldn’t there? I fondly imagined that a quick visit to Wikipedia would sort out the facts of the matter.
I was wrong. The heat pump Wikipedia page kicks off with the thermodynamical impossibility of getting energy from cold air. But if you visit the air source heat pump page you get an unequivocal pitch for the merits of the technology (lifted from a manufacturer’s sales document.) The French version of Wikipedia pitches right in with an explanation of how air heat pumps work and reports on tax breaks encouraging their installation. More publicly available information on the heat pump comes from blogs—usually rehashing the same sales pitch. Although one or two express disappointment at their high heating bills despite heat pump help!
Air geothermal heating and cooling is rather like the Monty Hall problem. Its logic seems to shift around every time you think about it. If someone knows where there is a definitive explanation—or more likely a debunking, I would like to hear it. But my failed attempt find THE answer made me reflect on the reliability of the world wide web as an information source.
Unfortunately, the preponderance of information on the web is unscientific chit chat. The web is a medieval world of charms, half-truths and snake oil—with air heat pump physics as a modern day equivalent of phlogiston. This is compounded by the fact that while the chit chat is free, science often is not. Books and scientific publications are hidden from public view and require subscriptions to read. I would suggest that the most likely source of truth in a scientific context is a university or learned society. But the paradox is that universities have a business model to defend, and learned societies tend to jealously guard the intellectual property (even when this has been given to them for free.) The result? As we see with the heat pump, on the web you are more likely to find bull from enthusiastic amateurs than gospel from the experts. There is a distinct weighting of the knowledge scales in favor of the unqualified hordes.
There is a curious corollary to all this. No scientific community really works in isolation. For instance, if you are a geologist working on say, reserves, then you will need information from some domains that are not really in your bailiwick. A geologist may need information on economics or statistics to complete his or her study. Where is this to come from? Unfortunately, unless the geologist reads the Journal of Statistics (I made that up) his or her knowledge of things statistical may be brought in from the above public (dubious) sources. This then feeds back into the geological domain and leads to questionable science and circular reasoning along the lines of the air heat pump. I would submit that a lot of the current discussion on reserves reporting and ‘risk management’ falls into this category. But I may be wrong on all counts...
References on www.oilit.com/links/0802_1.
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