Sunday, January 9, 2011

Energy, Chocolate, and Mechanical Engineering

Mechanical Engineering magazine has been on a roll lately with articles that I think are pretty damn interesting.  I read them but also feel compelled to share them with you here.  Such is the case with their January 2011 issue.

In Myth vs. Fact, two folks from MIT's Sloan School of Management try to separate myth from fact when it comes to energy policy.  They write "Before we can embrace appropriate energy policies, we have to face the hard truths about the technologies available to us."  So here I'll just repeat their headlines verbatim for you to deliberate, discuss, and debate.

  • Truth: Without significantly higher energy prices, energy demand will continue to grow - especially in developing countries. 
  • Myth: The world is running out of fossil fuels.
  • Myth: Renewable energy generation technologies are free from environmental concerns.
  • Truth: Continued reliance on fossil fuels is altering Earth's energy balance.  The risks of extreme temperature changes and subsequent impacts will grow substantially unless concrete actions are taken.
  • Myth: Getting started on reducing greenhouse gas emissions will require transformative technologies.
  • Truth: There are opportunities to greatly reduce energy intensity through gains in efficiency.  These gains could be made by both technological advances and price-induced substitution.
  • Myth: There is little room for improvement on fossil energy technologies - fossil fuel extraction, internal combustion engines, and so on.  Therefore, only small advances are needed before alternative energy technologies are competitive.
  • Myth: Explosive growth in renewable fuels in recent years is evidence that these alternatives are economically competitive with traditional fossil fuels.
  • Truth: Subsidizing renewable energy generation doesn't lower the cost of alternative energy; we simply pay the cost in other ways - and at the expense of cost-effective market-based policies.
  • Truth: The true costs and benefits of available alternative technologies are highly uncertain.  Therefore we should all be careful about predicting technology winners.

The same issue provides dessert in the form of a great article on the high-tech challenges involved in making chocolate, Engineering Taste, authored by researchers at the University of Birmingham in the U.K.

The complexity here is based in the fact that molten chocolate is a non-Newtonian fluid whose viscosity changes with applied shear force.  What's important is to solidify this liquid in one of its six stable solid forms, one of which is preferred from the standpoint of mouth feel (melts at body temperature) and visual appeal (glossy).  Unfortunately, this solid form isn't stable and often the result is a less desirable solid form that looks funny and tastes gritty.  (I recognize this taste as a brand that begins with "H".)

One key to achieving the correct solid form is the cooling rate.  One method uses a very slow cooling of 1 or 2 degrees Celsius per minute.  But another technique called the "frozen cone" method chills the chocolate in 3 seconds using a cone plunger at -20 degrees Celsius.  Obviously, this works well for creating thin chocolate shells.

So now we have some insight into the science behind the fluid dynamics of something we're all familiar with but have probably not thought much about.  In addition to mouth feel and taste, another area interest for these researchers is the nutrition and digestion of this manufactured food.  My parting chocolate advice is to stay away from the "kiss" - that little pointy tip always breaks off and leaves tiny brown stains on your shirt.

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