To supply power for use in outer space and also at remote sites on earth, we need power sources that are reliable, light in weight, and capable of unattended Operation for long periods of time. Nuclear power plants using direct conversion techniques hold promise of surpassing conventional power sources in these attributes. In addition, the inherently silent operation of direct conversion power plants is an important advantage for many military applications.
The Atomic Energy Commission, the Department of Defense, and the National Aeronautics and Space Administration collectively sponsor tens of millions of dollars worth of research and development in the area of direct conversion each year. In particular, the Atomic Energy Commission supports more than a dozen research and development programs in thermoelectric and thermionic energy conversion in industry and at the Los Alamos Scientific Laboratory, and other direct conversion research at Argonne National Laboratory and Brookhaven National Laboratory. Reactor and radioisotopic power plants utilizing direct conversion are being produced under the AEC’s SNAP[1] program. Some of these units are presently in use powering satellites, Arctic and Antarctic weather stations, and navigational buoys.
Further applications are now being studied, but the cost of direct conversion appears too great to permit its general use for electric power in the near future. Direct techniques will be used first where their special advantages outweigh higher cost.
DIRECT VERSUS DYNAMIC ENERGY CONVERSION
Dominance of Dynamic Conversion
We live in a world of motion. A main task of the engineer is to find better and more efficient ways of transforming the energy locked in the sun’s rays or in fuels, such as coal and the uranium nucleus, into energy of motion. Almost all the world’s energy is now transformed by rotating or reciprocating machines. We couple the energy of exploding gasoline and air to our automobile’s wheels by a reciprocating engine. The turbogenerator at a hydroelectric plant extracts energy from falling water and turns it into electricity. Such rotating or reciprocating machines are called dynamic converters.
A New Level of Sophistication: Direct Conversion
A revolution is in the making. We know now that we can force the heat-and-electricity-carrying electrons residing in matter to do our bidding without the use of shafts and pistons. This is a leading accomplishment of modern technology: energy transformation without moving parts. It is called direct conversion.
The thermoelements shown above the turbogenerator in [Figure 1] illustrate the contrast between direct and dynamic conversion. The thermoelements convert heat into electricity directly, without any of the intervening machinery seen in the turbogenerator.
