The Washington times., 1924-05-09
SURPLUSPOWE
DEMAND HERE
FORESEEN
Engineer Outlines Plan for
suppIemsrtIng Hydro by
Steam at Coal Mines
Continued from First Page,

Continued from First Page.)
tention has arisen during recent
days. Apart from its capacity to
serve the present needs and meet
the demands of common order in
the immediate future coming from
this territory, admittedly to absorb
only a portion of the total available
power, other fields of industry
identical with those devised for the
Tennessee river would naturally be
offered for exploitation, all de-
pendent upon cheap electric power.
There are two classes Of power
output to be generated at the falls
OF the Potomac, just as in nearly
Il all other hydro-electric develop
ments on Appalachian mountain
streams, arising from the charac-
teristic peculiar to them all of
widely varying fluctuation in the
volume of their discharges in the
several seasons of the year. These
two classes are known as primary
and secondary power. respectively
Primary power Is that generated
Of a dependable minimum amount
for application to continuous usage
every day Of the year. It's Valae
determines \the basic rating Of the
power plant in horsepower or kilo-
watts. The minimum regulated or
controlled volume Of stream dis.
charge in cubic feet per second Of
continuous flow is the prime factor
upon which its calculation rests,
The main inatrumentalitie Of regu-
lation and control are bondage and
storage, the former being of iuame-
date and normal recourse and the
latter of worth for emergency and
intermittent service.
Lake First Source.
Pondage is the term applied to
the volume of water held in leash
back of the main dam ana imme.
diately in contact with the power
station. which in the case of the
first stage development at Great
Falls Is represented by lake
thirty.four miles. in length. This
lake will be con- instantly fed by the
waters of natural flow from the
upper watershed. Whenever the
rate at which the power utilizes
the water exceeds that of the
natural stream flow, there follows
a gradual lowering of this lake sur.
face or, as technically known,
drawdown. Should this rate Of
drawdown become greater than a
definitely fixed amount, the deple.
ton Of the bondage would attain a
limit calling for replenishment
which can then be gotten by ca
upon the storage reserves in the
upstream valleys.
Storage volumes represent
portion of the excess run.off in per-
iods Of the year when rainfall Is
very heavy, confined to the larger
upstream tributary valleys by
means Of masonry dams provided
with regulating gates.
The instances where drawdown
and replenishment Of bondage are
necessary for continuous plant
operation are those obtaining dur.
ing drought periods of the year,
when natural stream flow from the
upper watershed area is deficient.
During the major portion Of the
year the natural stream flow is
equal to the demand for primary
power, and in some extended per.
iods greatly In excess. 1t is in
these latter that part OF the excess
run-off is collected for storage. The
storage reservoirs have fixed limits
and when the basins have been filled
surplus that cannot be conserved
spills to waste over the dam crests.
Accordingly to the natural stream
flow is then greatly increased be.
yond an amount necessary for pri.
mary power generation.
Secondary Power
In order that as nearly a full
value as possible may be extracted
in power generation from the stream
the year round means for utilizing
this surplus water are pro.
vided in the way of additional
waterwheels and electric generators
installed in the main powerhouse.
operating only when surplus Of water
Is available. The periods Of this
type Of operation are intermittent,
yet make UP in the total a good
percentage of the years run. The
power so generated ia known as
secondary.
The calculated secondary output
from the Potomac hydroelectric de-
velopments Is placed at amounts
varying from seventy to one hun.
bred and twenty thousand horse.
power. This energy IL available for
use to support industries whose
products are seasonal or that may
admit Of intermittent operation, such
as electrochemical works. The latter
are of the type proposed for estab.
Ashment on the Tennessee at Muscle
Shoals, although their layout 10
greatly in excess Of what Is possible
on the Potomac.
We have therefore in the Potomac
Valley a natural resource that com.
pares with the. much discussed
Muscle Shoals though in a modified
degree. The ratio between the two
is about four to ore. The potential
secondary power can be generated
here on the Potomac at a unit rate
to compare favorably with that cal.
| culated for the Muscle Shoals plants.
The Potomac country offers a far
superior location for distribution of
products than the mountainous and
remote Tennessee valley. Tapped
by main trunk lines and within a
few hours of the great cities and
industrial centers Of the Atlantic
States? its location is strategic.
Storage Reservoirs.
Fertilizer and such products az
calcium arsenate, the only effective
agency to combat and destroy tle
bOIl'weevil, can be readily and
cheaply manufactured at and near
the upper river power sites. The
fertilizer would have a ready mar.
ket close at hand to the site of
manufacture, to be utilized for the
rejuvenation Of the many wastes
OF wornout farmland of the Poto.
mac Valley, though by no means