h a v e a major effect on power-system cost
oxygen storage space the total energy output of
the system would be reduced by about 8 percent
effectiveness.
(lost in battery charging), but the system cost
f. Diesel. In principle, closed-cycle diesel sys-
would increase only about 1 1/2 percent (for batteries
tems are relatively simple. Standard diesel fuels
and additional inverter capacity) and the system
may be used. Part of the exhaust gas is cooled and
space occupancy would increase only about 0.5
enriched with oxygen from storage, and recircu-
percent.
lated to replace the normal air supply. Excess
(2) There are numerous variations of combined
water is condensed from the exhaust and excess
fuel-cell and battery systems. In all such systems,
carbon dioxide is removed by a caustic scrubber.
maximizing use of direct current power will mini-
Trace quantities of other gases and impurities from
mize inverter costs and losses. In general, the
the exhaust stream are dissolved in the scrubber
greater the peak power demand relative to facility
solution; all exhausted scrubber solutions are re-
standby power demand and the smaller the energy
jected to storage. The only change in actual engine-
demand at peak power relative to the total energy
operating conditions is the substitution of an arti-
requirement, the greater will be the advantage of
f i c i a l working fluid for air. The Navy and
using batteries to support peak loads on fuel-cell
Aerojet-General Corp. (Hoffman et al., 1970) have
power systems.
experimented with a working fluid of water vapor,
carbon dioxide, and oxygen. Design of the scrubber
e. Nuclear reactor. Nuclear-reactor power sys-
system would depend on power generation re-
tems always appear attractive, since they are in-
quirements.
herently closed systems with respect to the energy
(1) In general, closed-cycle diesel systems are
source. Cost data on reactor power systems within
feasible. However, to maximize thermal efficiency
the power range up to 3MW are very scant. Costs
and minimize space needs (chiefly heat sinks), a
of record of the smaller power systems developed
substantial development effort would be required
for the Army Nuclear Power Program (ANPP)
to identify the optimum water vapor, oxygen, and
strongly indicate costs could be competitive with
carbon dioxide mix; engine input temperatures;
those for battery or Apollo type of fuel-cell pow-
caustic scrubber conditions; waste-heat rejection
ered systems at net useful power and energy levels
temperatures; and equipment configuration. A fur-
on the order of 20 KW and 35 MWh, respectively.
ther substantial test effort would be required to es-
(1) Any estimate of the space requirements for
tablish reliability and availability data. For the
the shock-isolated, power-dependent elements of
most part, all major items `of equipment would be
small reactor-powered systems is subject to very
off-the-shelf and the entire development and test
large uncertainties. However, for the same net
program would be an order of magnitude less cost-
electrical power output, it is probable that the
ly and of substantially shorter duration than that
volume requirement of reactor systems will be 5 to
required for a nuclear-reactor powered system.
10 times greater than those for the power-
(2) While available data are inadequate for
dependent elements of battery or fuel-cell systems.
firm design analyses, it is possible to estimate
Based on the average efficiency and waste-heat re-
probable costs and space requirements. Assume
jection temperature of the ANPP power systems,
the closed-cycle system efficiency to be at least 65
heat-sink volume requirements will be on the order
percent of that of a normal, open-cycle diesel-
of four times that for fuel-cell systems.
electric system, and the cost no more than 50 per-
(2) All reactor power systems in the power
cent higher than the open-cycle diesel. Using these
range of interest are one-of-a-kind experimental
conservative assumptions, small, closed-cycle pow-
er system (say, 10 to 100 kW) average costs would
systems with limited operating history, hence
be on the order of 0/kW, and the cost per unit
without reliability data. No reactor power system
net power should decline to about 0/kW in the 1
designed as a shock-isolated installation for a high
ground-shock environment is known to have been
to 3 MW range (1976 prices). Even if subjected to
wide variations, these costs are down more than
assembled or operated. For the first such system,
two orders of magnitude from those probable for
the system operating characteristics, overall
battery, fuel cell, or small nuclear-reactor-based
thermal efficiency, reliability, and costs must be
power systems.
verified by actual system construction and opera-
(3) Space requirement for shock-isolation
tion. The complete power system, including reac-
equipment and power-dependent elements aug-
tor, shielding, steam generators, turbogenerator,
menting the closed-cycle diesel system may not dif-
feed water heaters, and feed water pumps, must be
fer greatly from those of battery or fuel cell sys-
mounted on a common, shock-isolated support
tems, but will be substantially less than the space
structure. Any redundancy requirement would
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