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5272Re: Air Conditioning, Cars, and livable places

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  • Theo Schmidt
    Jun 10, 2002
      "smoky_johnson" wrote:
      >Perhaps "Their share" was a poor choice of words. My comments were
      >directed at the original poster's implication that the people of the
      >deep south wasted energy through the use of air conditioning, without
      >his considering equivalent energy use for heating. In my view, both
      >uses are equally defensible (or indefensible) uses of energy. Just
      >because the technology for heating has been around longer doesn't
      >give it any particular priority. If this is wasteful - than so be it.

      Actually heating and cooling are quite different.

      As heat is the "lowest" form of energy, everything turns into heat
      eventually and it is easy to heat simply by burning something. In the
      case of cars and bicycles, the heating is free, being a "waste
      product" of the motor or human engine. In the case of houses, modern
      heating systems are between 90 and 100% efficient. If a "high" form
      of energy is available (e.g. electrical or mechanical), these can be
      turned into a greater amount of heat by the device called a "heat
      pump". Typically a heat pump produces three times the heat that you
      would get by direct conversion, e.g. electric resistance heating. If
      the sun shines, you can have "free" heat by using solar collectors or
      just windows or black paint.

      Cooling is usually much more difficult. Refrigerators or air
      conditioning work like a heat pump, but in reverse. Thus you need
      typically at least three units of a "high" form of energy like
      electricity in order to produce one unit of "coldness". Coolers which
      use heat (e.g. propane refigerators) are even less efficient.

      Only in some special circumstances is it possible to cool
      "efficiently", e.g. especially dry air, where all that is needed is a
      samll amount of evaporating water, or an available reservoir of
      "coolness", e.g. lake water or cold nights.

      It is remarkable that the human body can cope with both high and low
      temperatures, however many animals are even more remarkable, e.g.
      efficiently exchanging large amounts of heat and moisture in their
      noses at each breath and thus being able to survive high temperatures
      even without drinking.

      Theo Schmidt, Switzerland
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