Scientists at Johannes Gutenberg University Mainz and at the University of Erlangen-Nuremberg are working on a heat engine that consists of only one ion. Such a nano heat engine may be far more efficient than, for example, the engine of a car or a thermal power station. An ordinary heat engine converts heat into mechanical energy with the corresponding engine efficiency (up to 25% in the case of an internal combustion engine). The proposed nano heat engine, consisting of a single calcium ion, should be more efficient. The main aim of the research is to understand better how thermodynamics works on very small scales. A pilot prototype of such a single-ion heat engine is at present being built at the university in Mainz.
The efficiency of heat engines is determined by the second law of thermodynamics, one of the fundamental concepts in physics. As early as 1824 the French scientist Nicolas Carnot calculated the highest possible limit of the efficiency of such engines. In the case of the new nano heat engine being proposed, scientists are theoretically in a position to exceed the classical Carnot limit of efficiency.
Calculations and modelling done about a year ago showed that the thermodynamic flow in an internal combustion engine can be reproduced with the help of individual ions.
The idea was to use for this purpose the 40Ca ion, whose diameter is a million times smaller than that of a human hair. "Individual ions can act as the piston and the drive shaft or, in other words, make up the whole engine. Individual ions have already been caught in a Paul trap and, using laser beams and electric fields, not only cooled and heated but also compressed. This means that we are in a position to control the distribution of position and momentum for optimal efficiency", the scientist explained.
Since the mechanical power of a machine made of one ion is extremely small, it can probably be used only in the heating or cooling of nanosystems.
The scientists plan to build a prototype of the engine in the laboratory.