Evening star. [volume] (Washington, D.C.) 1854-1972, 1939-04-13
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
BIZ Thomas r. Henry.

By Thomas r. Henry.
An amount Of power almost Infinite
Is poured on the earth by the sun. II
only a small fraction of it could be
utilized directly, instead of in the de-
rived forms of falling water and coal.
there would hardly be need for any
other source of energy.
: For years DR.. Charles G, Abbot, sec
rotary of the Smithsonian Institution,
has been working on this problem and
has devised various ways of direct utili-
zation. Solar-power utilization. he be-
lieves, now is just approaching the prac-
tical stage where, in certain limited
fields at least, 1t may compete success
fully with steam or water power.
His latest progress report reveals that
he has now devised highly efficient solar
engine which will supply power at a cost
of about half cent per horsepower
hour. In the same report he tells of a
suggestion of the distinguished WASH
ington chemist, DR.. Frederick G. Cot
trell, Of means of storing sun heat
The proposal would utilize a solar
heater, several types Of which have been
invented by DR.. Abbot, which would
catch the suns heat DR.. Cottrell sug-
gests sil9-shaped, cementlined pit IN
the ground, filled nearly to the top
with dry, loose sand and rooted oyer.
Above the sand would be layer of
glass wool, very poor heat conductor,
approximately 10 feet thick, such as is
used for roof insulation.
Then, as the proposal is reported, "a
pipe leading from the solar heater to
the center of the upper surface of the
sand has an appropriate network of
branch pipes covering the surface. A
similar network at the bottom OF the
pile leads to an outlet pipe, and thence
runs back to the heater. An automatic
pump which runs only while the focus
tube is hot draws hot air through the
solar heater into the top of the sand.
lowing to. the VIGOROUSLY bad con-
ductivity of dry sand, and the high
degree of protection from upward con-
vection and conduction offered by the
thick layer of glass wool, the sand pipe
keeps the heat and keeps 1t in a hori-
zontal layer. The heated layer grad
ually works down till, If the storage
operation is very long continued, the
whole sand pile becomes Of nearly as
high a temperature as the air in the
focus tube itself. With a sand silo Of
sufficient capacity DR.. Cottrell thinks
the efficiency would be so high that
when the heat was drawn away, per-
haps months later. by reversing the cir
culation Of air, the air would come away
from the top of the sand very nearly
as hot as it formerly entered"
Most Of the report is concerned with
the progress of DR.. Abbot's own re-
searches in the utilization of solar en-
ergy. With only is per cent CONVEX
sion into mechanical energy, he points
out. the State of New Mexico alone
could supply from solar radiation more
than 10000, 600, 000, 900 horsepower hours
of power per year-eQuivalent to the
power possibilities Of all the coal, oil
and water at present used for heat,
light and power in the United States. If
ways of efficient conversion and storage
can be devised this sun energy. from
which even now is derived indirectly al
most all energy known on earth, is
likely to be dominant factor in the
life Of the future, when coal approaches
exhaustion and all the available water
power is utilized.
DR.. Abbot's most recent researches
have been on the improvement of his
solar flash boiler engine-that is, an en-
CINE with single tube boiler protected
from heat losses by an elongated glass
vacuum jacket and fed by a current
Of water automatically graduated in
flow by the temperature of the boiler
With this device it is possible to raise
full steam pressure within five minutes
after exposure to the sun. Should the
sun enter cloud the water supply is
automatically shut of. Should the
steam pressure rise above the desired
maximum the water supply is increased.
Thus the boiler takes advantage auto
matically of all the clear sky which
comes between clouds. It is, in part
at least, an answer to the objection that
sun power would be very spasmodic.
since it would be cut of every time
the sky was darkened.
The solar flash boiler, DR.. Abbot's CAL
culations show, would be quite efficient,
utilizing somewhat over IS per cent Of
all the radiation energy striking its mir
ror. Power, he calculates, could be gen.
Grated IN this way at a cost of about
a half cent per horsepower hour.
Some Of his latest experiments have
resulted in the production OF very eff
Gent solar water distiller, which prom
ises to be of great value in regions
where the water is unfit to drink. The
solar distiller provides water of perfect
purity and odorlessness.
The real significance of the solar en-
ergy conversion work lies in the posi-
bilities and needs of the future. The
objection which at first thought comes to
everybody is that, regardless OF the
enormous energies which the sun is
pouring on the earth the supply is in
termittent-shut of at night and on
cloudy days and, in northern sections,
greatly reduced in winter.
But the outlook Is far from hopeless,