system to include no fewer than the following
21. Three operating modes.
a. Overview. View the power supply system
--Satisfy peak-power and peak-energy demands.
--Satisfy normal power demands at acceptable
attack, transfer, and transattack/postattack. Usu-
ally, it will be most effective to use a different sys-
--Provide acceptable power quality.
tem to satisfy each of these three modes.
--Provide acceptable preattack availability.
b. Preattack power. Use either commercial pow-
-- P r o v i d e acceptable endurance availabil-
er or a dedicated power-supply to satisfy the
preattack power requirements. Use commercial
--Accommodate preattack exercising.
power if it is compatible with the system power re-
(1) Choose the effective degree of atmospheric
quirements. Conventional civil-power technology is
isolation of the power supply system and the at-
quite adequate to adapting commercial power to a
tendant waste-heat rejection system. Bear these
hardened system. The basic weakness is that loss
three facts in mind:
of commercial power forces the system to operate
--Except for exported communication signals,
on the transattack/postattack power supply, which
the total electrical energy produced reap-
has, of course, a finite endurance.
pears in the facility as waste heat to be
(1) This is a fundamental issue: When does a
added to the waste-heat rejection load.
mysterious, or even a not-so-mysterious, loss of
--For open-power systems that use air cooling,
commercial power constitute an "attack" on the
the parasitic electrical power demands of
system? An onsite, dedicated preattack power sup-
the waste-heat rejection system greatly
ply reduces the potential for a mysterious loss of
increases the power level requirements of
power but does not eliminate it.
the power-supply system.
(2) If commercial power is not satisfactory, use
--The costs of a closed-cycle power supply sys-
an onsite, surface power plant. State-of-the-art,
tem and a closed-cycle waste-heat rejec-
open-cycle systems are satisfactory candidates,
tion system can dictate the cost of the en-
whether the surface plant is unhardened or is nom-
inally hardened. Diesel-powered generators are the
In general, the more severe the survivability re-
most promising candidates for small and moderate
quirement, the more effective must be the closed-
power levels. Fossil-fueled or nuclear-powered
cycle operation of both the power supply system
steam-turbine generator systems offer comparable
and the attendant waste-heat rejection system (fig.
thermal efficiency only in large (>10 MW)
(2) During the preattack (peacetime) period,
c. Transfer power. Design of transfer power sys-
the transattack/postattack system would be period-
ically operated to demonstrate readiness; other-
tems are controlled by functional requirements of
wise, it would idle in a standby mode or stand dor-
the total facility. Delay tolerance and facility relia-
mant. I n o t h e r t h a n t h e d o r m a n t m o d e ,
bility must be considered in selecting subsystems
to transfer power mode from preattack condition to
consumables must be replenished to maintain ac-
transattack/postattack. The transfer-power system
can be as simple as a compressed-air supply con-
22. Open cycle.
trolled by battery and sequencing valve that can
a. Candidate systems. The diesel engine is the
start the engine of the postattack power system.
best candidate for prime mover in open power sys-
More typically, it will be a combination of such a
tems. Compared to diesels, steam-turbine-powered
system with an uninterruptible power system
systems are relatively inefficient except in the
(UPS) in the form of a battery-inverter supply for
multimegawatt range. They have the additional
handicap of requiring heat removal at relatively
d. Transattack/postattack power. This is the
low temperatures. The same objections apply to
critical operating mode and requires selection of
nuclear steam-powered systems, as well as the fur-
subsystem compatible with requirements for the
ther handicap of exorbitant capital cost at the low
hardness level of the entire facility. With prime-
power levels generally required for hardened facili-
mission materiel/personnel (PMMP) needs defined,
ties. Gas-turbine systems may present an alterna-
design the transattack/postattack power-supply