Evening star., 1942-10-06
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Laboratory, Field
And Study
BIZ Thomas r. Henry.

ana Stuoy
By Thomas r. Henry.
The building Of tomorrow will require
sources OF power not dependent on
dwindling resources.
Some of the possibilities are described
in the annual report of the Smithsonian
Institution, just issued. Fascinating pos
sibilities are offered by the energy
equivalent to that OF 81 900, 100000 tons
of coal which the sun showers on the
surface of the globe every hour.
This has been foremost objective of
the researches of DR.. Charles G. Abbot,
secretary of the Smithsonian, who has
built highly efficient solar engines which
have come very close to economic prac-
ticability.
But there is one major obstacle to
high eficiency-the fact that the amount
of power produced depends directly on
the area over which the solar energy is
gathered. This soon becomes very large
and the cost consequently high-when
great amounts of power are considered.
Other ways are open, however, and are
outlined in the Smithsonian report by
DR.. H. c. Hotel of the Massachusetts,
Institute of Technology.
Experiments now in progress there
are intended to explore all the posi-
bilities of economic conversion Of solar
energy into forms useful in industry.
One possibility is direct conversion into
olo ofyioi hv Nf Ievipo
based on the principle OF the thermo-
couple. When wires to two different
elements are joined and the junction is
heated small part of the heat is con-
verted into electrical energy.
The amount converted is very small.
The phenomenon now is made use of in
construction Of some Of the most deli
cate scientific instruments known to
man, by means Of which it Is possible to
measure temperatures Of distant planets
by focusing their light on such juno
ton. The efficiency of the system de-
pends on the heat-conducting and elec-
trical-conducting properties of the two
materials used in the thermocouple.
Intensive studies of the thermo-elec-
trio properties Of various metallic COM
pounds and alloys now is in progress
to determine which is the most efficient.
At present, says DR.. Hotel, the best
results are obtained with an alloy OF
zinc and antimony, containing about As
per cent zinc, coupled with an alloy
known as "copel" Actually when
temperature difference between the hot
and cold sides of the junction Is main
tanned at 400 c., there is about per
cent conversion Of heat to electrical
power. This seems small, but the best
of modern steam power plants has only
q Is per cent efficiency in converting
coal into energy 1t Is entirely possible
that more efficient functions will be
found from the present experiments
With the heat Of the sun focused on a
great number Of such couplings a small
engine might be built which would be q
fairly efficient power producer-consid-
ering that the heat itself costs nothing.
Another means of conversion is the
phenomenon of photo electricity in which
there Is direct conversion of solar energy
without first converting it into heat.
The phenomenon is we'll known to the
meter which indicates on a dial the
intensity of illumination.
Light is converted directly into elec-
trical energy which in turn is used to
| make the galvanometer meter move.
The light falls on light sensitive unit
I>,,4x !, 61,1ocIjrr y,hnfo-po11 -
| The copper oxide cell is typical, although
several other forms are in use. This
| consists of a massive plate of copper
which has been oxidized on one face and
then etched, to produce thereby layer
| grading from pure copper oxide through
all proportions of oxygen down to pure
oxygen. This plate is covered with a
is transparent to light.
| If quantum of visible light strikes
the thin metal cover it passes through
and penetrates to some point in the
structure where the composition lies
between that of copper oxide and cop
per, and there the quantum, or bullet
of electrical energy, succeeds in knock
ing out an electron. This electron can
move more easily through copper and
through copper oxide toward the other
metal film. Thus small current of
electricity is set up.
There is small overall conversion
of the solar light waves to electrical
power of about half of l per cent. If
this could be increased tenfold the
apparently lies in the discovery OF more
and more efficient photo-electric cells
and there is no certainty that this will
not be possible. Experiments now are
in progress, without any present prac-
tical objective, to determine exactly
what happens in the process.