However, the fuel storage space would be in-
requirements for nuclear-reactor power systems.
creased because of cryogenic storage of hydrogen.
Based on the overall system efficiency and flow
rates reported for the Aerojet experimental sys-
g. Stirling. The Stirling engine is an external-
tem (overall thermal efficiency about 20 percent),
the fuel and oxygen demand would be about 900
Stirling engine has not been widely used because
lb/MWh and 3200 lb/MWh, respectively. Assuming
the diesel engine costs less. The current high and
hard-mounted fuel storage with a small allowance
rising cost of petroleum-based fuels has caused re-
for ullage and tank, the fuel volume occupancy
newed interest in the Stirling engine because of its
would still be only about 17 ft /MWh. Oxygen, if
potentially high thermal efficiency. However, in a
stored as a liquid in dewars on shock-isolated struc-
closed-cycle system the efficiency of the Stirling
tures, would require a total storage space of about
engine may be similar to that of a diesel engine.
120 ft /MWh. Caustic scrubber solution must be
(1) If it is assumed (conservatively) that lower
stored separately but would not add appreciably to
parasitic loads would permit the Stirling engine
total space requirements.
system to operate at a thermal efficiency of 25 per-
cent the required heat-sink capacity should be
(4) The heat of formation of either potassium
based on a waste-heat load of 4 MWht/MWh e. Hy-
carbonate or sodium carbonate is on the order of
drogen and oxygen consumption would be about 56
1100 Btu/lb of carbon dioxide absorbed. This heat
a n d 444 lb/MWh t, values are 12.5 and 6.2
adds to the total waste-heat load.
ft3/ M W h t, respectively. The cryogenic hydrogen
and oxygen storage space requirement would be
(5) A recent survey (1977) of 15 projects to
about 300 ft3/MWh e.
(2) The weight and space occupancy of power-
indicated that 26 conventional automotive engines
dependent system equipment should be less for the
were modified for hydrogen fuel and 14 were being
Stirling than for the diesel system. Hydrogen fuel
road tested. With hydrogen in place of hydrocar-
would eliminate need for a caustic scrubber
bon fuel, a caustic scrubber and solution storage
would be eliminated and the system simplified.