Preserving / conserving energy

« previous post | next post »

The other day, I bought a soda from a vending machine that was adorned with this sticker:

Wait, I thought to myself, shouldn't that be "This machine conserves energy"?

But then again, the first law of thermodynamics guarantees that conservation of energy applies to ALL machines.  Still, "… preserves energy" sounds strange — probably because it's relatively rare:

And pretty much all of the examples of "conserves energy" that I find (e.g. in recent news reports) deal with saving fuel or electricity rather than with the consequences of Noether's theorem.


  1. KathrynM said,

    October 30, 2012 @ 8:28 am

    Preserved energy. Petroleum jelly?

  2. Joe Green said,

    October 30, 2012 @ 8:29 am

    Something that preserves energy would be for example a battery, I suppose. Or jam.

  3. Rod Johnson said,

    October 30, 2012 @ 8:34 am

    "This machine uses energy (less in)efficiently (than it might have)" doesn't have quite the same zing to it.

  4. Andy Averill said,

    October 30, 2012 @ 8:40 am

    Noether's law doesn't apply to dissipative systems, but anyway, isn't the first law of thermodyamics more relevant here? Since the vending machine presumably has a refrigeration unit, and therefore dissipates heat, I would say it does not preserve energy.

  5. MattF said,

    October 30, 2012 @ 9:02 am

    On the other hand, if I saw a vending machine that said "This Machine Conserves Angular Momentum", I'd think about it for a minute and then (keeping my hands in my pockets) slowly back off.

  6. David L said,

    October 30, 2012 @ 9:04 am

    "This machine husbands energy?" I suppose that might be decried as sexist these days, but I can't think of another word that quite captures the same meaning — i.e. the opposite of "squanders."

    Jams and jellies, by the way, are referred to both as preserves and conserves.

  7. The Ridger said,

    October 30, 2012 @ 9:05 am

    "This machine is energy-efficient" – why not?

  8. David L said,

    October 30, 2012 @ 9:10 am

    @The Ridger: because someone at the vending machine factory is convinced that "is" is a passive verb, and therefore to be avoided strenuously.

  9. Henning Makholm said,

    October 30, 2012 @ 9:20 am

    After googling "VendingMiser", I think the meaning must be something like: "This machine uses a complex and expensive after-market gadget to do what a simple thermostatic control on its cooling system could have done better, and thereby uses less energy than a hypothetical machine that has neither a thermostat nor an external gadget."

  10. Shanth said,

    October 30, 2012 @ 9:22 am

    "saves energy" seems to be the standard phrasing I've seen. @Andy, well heat is a form of energy, the first law of thermodynamics is just the statement of the conservation mechanical+thermal energy.

  11. Andy Averill said,

    October 30, 2012 @ 9:24 am

    Can't help thinking of what it said on Woody Guthrie's guitar case: This machine kills fascists.

  12. Joshua said,

    October 30, 2012 @ 9:33 am

    Wouldn't want our energy getting all stale, would we?

  13. Duncan said,

    October 30, 2012 @ 10:39 am

    @ Henning M:

    You got me googling too. (I totally overlooked the brand name until you mentioned it, then got curious.)

    Seems the thing powers down the machine for extended periods (1-3 hours at a time based on ambient temps) when the area's unoccupied (infra-red sensor detected). In addition to the cost of the lighted display, here in Phoenix, that could be the difference between keeping soda and bottled water at a thermostatically controlled 40F 24/7, and letting the temp rise to say 60F when nobody's around anyway. With summer outdoor highs 110F+ and winter highs in the 60s or 70s anyway, that could be significant savings over a simple "stock" thermostat, particularly for outdoor machines.

  14. Brett said,

    October 30, 2012 @ 11:09 am

    @Andy Averill: It was Guthrie's actual guitars that sported that statement, not merely the case.

  15. Jim Milstein said,

    October 30, 2012 @ 11:45 am

    I thought of Woody Guthrie's "This machine kills fascists", on his guitar.

  16. Eee said,

    October 30, 2012 @ 7:58 pm

    @Andy Averill re: Thermodynamics:

    I'd say whether you use the term "preserve" or "conserve", the truth statement simply depends on whether you consider the machine as a closed system or not.

    Per the 1st Law, everything preserves energy, when you really think about it, until you put an arbitrary boundary around the system.

    [(myl) And the system's operation is surely time-invariant, at least considered abstractly, so Noether's theorem applies…]

  17. Andy Averill said,

    November 2, 2012 @ 6:51 am

    @Eee, if you're talking about a vending machine, isn't the machine itself the relevant system? Closed systems only exist in physics textbooks — in the real world, you'd have to expand the system to the size of the whole universe to get everything conserved down to the last significant digit.

RSS feed for comments on this post