Page 4 ^ ^ The Clarion | Feb. 5, 2C
Efficiency tiie solution to our energy woes
by Dr. Jim Reynolds
Faculty Contributor
Water is the most abundant compound
on Earth’s surface. It is fascinating and
amazing stuff. Few people realize how
astounding it really is. Its abundance exists
because of Earth’s serendipitous location
at just the right distance from the sun to
accommodate H20 in its liquid state: a little
bit closer to the sun, like Venus, and most
water is in the vapor state while a little bit
farther away, like Mars, and it’s all frozen.
Such placement allows our numerous and
diverse life forms to exist.
Water has other fascinating properties.
Its molecular chemistry is a bit odd.
Because like charges repel while unlike
charges attract, we would expect that the
two positive hydrogen atoms to be on the
exact opposite sides of the negative oxygen
atom, separated by a 180° angle.
But that’s not the way water works. The
hydrogen atoms are separated by a 104.5°
angle making water a polarized molecule:
slightly positive on one side and slightly
negative on the other
This, in turn, allows the positive side
of one water molecule to snuggle up with
the negative side of another to form a
hydrogen bond. One familiar result of this
polarization is that things get wet!
Water is attracted to any static electrical
charge, positive or negative. Charged
surfaces get wet. Uncharged materials, like
Teflon, can be dried simply by shaking any
water droplets out.
Another, weaker, type of molecular
bond, the van der Waals bond, helps to hold
the molecule tighter against its neighbors.
Water also has a high heat capacity. It
absorbs lots of heat energy before it warms.
Would you rather hold 10 grams of water
that had been held over a candle for five
seconds or 10 grams of steel? It takes one
calorie of heat to raise the temperature of
one gram of water one degree Celsius.
Steel has a lower heat capacity and warms
much faster
Ice differs from water in that it only takes
half of a calorie to raise its temperature
one degree. With each degree of rising
temperature, the ice molecules vibrate a
little faster until, at melting temperature
they are vibrating fast enough to begin
breaking the van der Waals bonds and start
to change solid ice into liquid water
This doesn’t happen all at once. In fact,
ice will stay at the freezing temperature
until it absorbs enough energy to break
nearly all of the van der Waals bonds.
It takes an extra 80 calories per gram to
break these bonds and melt ice completely.
That’s why snowballs don’t melt
immediately when brought indoors and
why an ice cube doesn’t melt immediately
when plunked into a martini. Subsequent
heat input elevates the liquid temperature
but if the temperature remains constant.
Earth’s atmospheric pressure is low enough
so that liquid water evaporates.
Water continues absorbing energy to
the point where it vibrates so fast that the
hydrogen bonds and any remaining van
der Waals bonds are broken, liberating
individual water molecules to be absorbed
into the air as water vapor Incredibly, each
gram of water must absorb an additional
580 calories before it evaporates at room
temperature (20° C).
At boihng temperature (100° C), only an
additional 540 calories/gram are needed.
These transitions of state, from solid to
hquid and from liquid to vapor, are referred
to as the latent heat of melting and the latent
heat of vaporization, respectively.
During cooling, energy is released at
these state transitions, which are referred
to as the latent heat of condensation and
latent heat of fusion or freezing.
Because water is so abundant in nature,
these energy transfers through state
transitions go on all of the time. We give it a
special name: weather Basically, weather is
the transfer of heat through the medium of
water vapor carried on the winds. General
weather patterns are referred to as chmate.
The Industrial Revolution was based on
the realization that tremendous amounts
of energy could be stored in steam if water
were heated in boilers fed by coal.
Some of that energy could be expended
by using pressurized steam to drive pistons
or spin turbines to make electricity.
Under pressure, steam and its abundant
energy can be forced through pipes and
delivered to radiators for space heating.
What is done with that steam on this
campus is the real topic of this essay.
Myers Dining Hall, Coltrane, McLarty-
Goodson, Beam Administration, and
Moore Science are heated with hot water
that is heated by steam from the central
steam plant.
Steam is pumped through underground
pipes at high temperature and low pressure
(83 kiloNewtons/square meter (12 lbs/
in2), with about 40% heat loss to the
enviroimient through leaks and inadequate
insulation. The steam then enters a heat
exchanger where it warms water to about
65° C. The heated water is then pumped
to the radiators where it heats the air to a
temperature set by the thermostat (20° C).
The steam condensate is then recycled
back to the boiler systems and heated again
for another round.
In its endeavor to do away with the
central steam plant and decentralize steam
heating, the College is not only abandoning
a crumbhng infrastructure but it is creating
a huge savings in energy costs and reducing
our carbon footprint by becoming more
efficient in the way it uses energy for space
heating.
The new “boilers” in the buildings
will not really boil water because they
don’t need to create steam. This wfll save
the large amounts of energy required to
overcome the latent heat of vaporization.
Instead, water can just be heated to 65°
C and pumped through the buildings to the
radiators. There wiU be no further need for
steam! We wiU have entered the latter third
of the 20th Century!
To move us into the 21st Century, the
next step wfll be to heat water used in our
buildings directly from the sun and use
the new water heaters for back-up when
temperatures are cold or the sun isn’t
shining.
Through grants from the Katherine Prey er
Foundation and the Student Government
Association, the College has $10,000 in
starter money. Institutional Advancement
is currently pursuing grants to raise the rest
of the money needed for our first foray into
the Solar Era. Our littie college is getting
smarter and moving into a greener future.