Evening star., 1923-04-01


power per acre. do not imagine that
anything like that amount can be
Icaptured or converted into mechanical
power by any methods known at
present. We are very wasteful with
heat and power derived from coal.
even under the best mechanical con-
trivances we have today, and coal
burning has had a great deal of sci
entifc thought expended on it.
THE heating value of good coal is
Il about 14.5O0 B. {. us per pound
A B. t. u. is short for British thermal
unit, the amount of heat required to
raise a pound of pure water 1 degree
Fahrenheit in temperature. The ton
OF coal. having 14.500 units TO the
pound, is equivalent to about 12.760
horsepower hours. Yet the best
results human brains have so far Sc
cured, by means of boilers and steam
engines, will bring out only about
l,470 horsepower hours at a place
where II can be utilized. That is
something less than IL per cent heat
efficiency. An ordinary locomotive is
between and 10 per cent efficient on
a heat basis.
| With internal combustion engines
the heat efficiency runs somewhat
higher. Gas engines have as high as
25 per cent. Diesel engines, using
heavy oil at very high compressions,
| nave recorded an efficiency of 81 per
cent. This. therefore. Is the most
efficient power unit yet devised. Yet
it gets less than one-third the avail
| able heat converted into mechanical
| anepgy. If your auto engine ran even
| % per cent efficiently, on heat basis,
-ou would get around 100 miles TO
| he gallon of gas.
In turning the suns heat into
| steam by direct processes the eff
cheney of the methods so far used in
Egypt, South America, Arizona and
other places has been around 40 per
cent. This compares with 75 per
cent heat efficiency for a coal-fired
boiler. Making coal-fired boilers.
however, is an art well understood,
and making sun boilers is relatively
new and may be improved as new
brains get to work on the problem.
At this time. when so much pub
licity has been given a new sun en-
gine invented up at New York City
College, II is difficult to say in all
fairness whether or not anything new
has been discovered. From what has
been made public, however. It would
appear as old stuff. The idea that
immense quantities of sun heat can
4 ho c4a ioto
mechanical power, is not new, nor
is 1t true that any method has yet
been found for transferring that stored
heat after 1t is canned"
! Many years ago sun-power plants
we're used An Egypt to pump water
for irrigation systems in arid sections.
That system used a mirror placed
horizontally, parallel to the ground.
The Button mirror was a big i'm
provement, and the parabolic mirror
even greater; and these are nearly
200 years old. With the horizontal
mirror an efficiency of about per
cent was obtained. With parabolic
mirror 40 per cent has been recorded.
Even old Capt. John Ericsson, de-
signer of the Monitor of civil war
fame, took a fling at sun engines
back in the post-civil-war days. He
spent about 100000 experimenting,
and then wrote: Though the heat is
obtained for nothing, so expensive,
; costly and complex is the mechanism
for concentration apparatus that
solar steam Is many times more ex-
pensive than steam produced by
burning coal" That was in 1873, be-
fore the days of present freight
rates. Ericsson took the engine he
had designed to run by sun power,
turned 1t into a gas engine to run on
ordinary illuminating gas and made
4 ments from profits on the gas-power
many times the cost of his expert
plant.
The diameter Of the sun is some
II $4,000 miles, nearly 100 times that
of the earth. This big mass. so far
away and so mysterious in its work.
ings, keeps US alive. 1t spreads down
the energy in dilute form to produce
the things we need. AS fuel or as a
source of power. one may figure that
the heat on two and a half acres for
an hour is equal to a ton of coal.
Or you can figure that in a year the
wood produced on an acre OF ground,
which amounts to an automatic bot
tling of the suns rays, is equal to a
ton Of COAL The plants. which store
up sun energy. are found to be right
careless in their efficiency, for they
! take in only Q per cent or less Of
solar energy to be transformed into
j chemical energy.