will be made. 
Given: 
Power Required: 25 watt (average) 
Fuel: Propane at $20 gallons 
Near 
Present Future 
Fuel Cost per KW-hour 
(approximate) $.30 eel) 
The situation in regard to capital cost 
of thermoelectric generators is extremely 
uncertain at the present time and in the 
near future. Most generators now being sold 
are individually built for evaluation pur- 
poses and are priced at hundreds of dollars 
per output watt. Furthermore the useful 
life of these devices is not really known at 
this time. Thus, the annual costs attribu- 
table to the initial price of an operational 
unit must be based on at least pilot plant 
production and a projected, reasonable life 
time. Industry estimates of generator cost 
for small quantities in the twenty five watt 
resion are in the ten to fifty dollars per 
watt range. If a conservative value of 
forty dollars be used, and a five year life 
is expected, the kilowatt-hour cost is 
approximately 80 cents. Comparing this to 
the estimated fuel cost, it can be seen that 
the capital depreciation can be the deter- 
mining factor in overall cost. It should be 
noted however, that these conservative cost 
estimates compare very favorably to all 
types of batteries as well as silicon solar 
cells. 
Figure 4 depicts a ten (10) watt thermo- 
electric power supply recently developed by 
the General Instrument Corporation for eval- 
uation by the U.S. Coast Guard. It is 
designed for use with shore based lights 
as well as large buoys and obviously is 
directly applicable to oceanographic 
research installations. This device uti 
lizes catalytic combustion of propane fuel 
as a heat source. The use of a catalyst to 
promote the reaction of propane and oxygen 
gives high combustion efficiency due to the 
low reaction temperature and it is virtually 
impossible to extinguish the reaction except 
by interrupting the fuel supply. It is 
designed to operate in near hurricane winds 
(70 mph) and in any position of roll. The 
system has an automatic restart provision in 
the event of excessive winds or swamping. 
The system tries to restart once an hour. 
In this way we avoid the possibility of try- 
ing to restart under impossible conditions 
and thus depleting the energy storage 
system. 
293 
Utilizing some similar design principles 
and techniques the General Instrument 
Corporation is developing a thirty (30) watt 
thermoelectric generator for the Bureau of 
Standards and the Navy's Bureau of Weapons. 
It is to be evaluated for use aboard their 
Gulf of Mexico based weather boat buoy- 
NOMAD. In comparison to the Coast Guard 
generator mentioned above, we will take 
advantage of the sea water sink by directly 
coupling the cold junction to the hull below 
the water line. 
Fossil fueled thermoelectric generators 
are available from other industrial sources 
but, in general, these are not specifically 
designed for, nor take advantage of, the 
ocean environment. 
The U.S. Atomic Energy Commission, 
through its office of Isotope Development as 
well as its SNAP (System for Nuclear Auxi- 
liary Power) office of the Division of 
Reactor Development, is developing a series 
of radioisotope fueled thermoelectric gen- 
erators for oceanographic missions and 
environments. These are briefly discussed 
below. 
A five watt demonstration device is being 
developed for a Lamont Geophysical Labora- 
tory mission using Cesium - 137 as the fuel. 
It is specifically aimed at the underwater 
environment since little shielding is pro- 
vided for the very penetrating radiations 
(Cs-137 is often used as a teletherapy 
source). 
Strontium-90 is being employed as the 
heat source for another series of develop- 
mental thermoelectric generators in the five 
to thirty watt range. These units contain 
a considerable amount of shielding and can 
be used on land. The first of these has 
been built and is planned for early 
Weather Bureau service in the Arctic in 
conjunction with an automatic weather 
station. 
The obstacles to the widespread use of 
the above mentioned radioisotope fueled 
senerators are; potential hazards and the 
high cost of separated radionuclides. In an 
effort to reduce the cost of radioisotope 
heat sources for the oceanographic environ- 
ment, the General Instrument Corporation, 
under USAEC sponsorship, is developing 
techniques for the utilization of Mixed 
Fission Products in thermoelectric genera- 
tors. The goal of our current effort is a 
demonstration device for unshielded, under- 
water use. There is a very large, existing 
AEC program, including an existing pilot 
plant, for the solidification and concentra- 
tion of nuclear waste materials, that 
directly assists these efforts. 
