Otto Engine

Abstract:
Scientists at Johannes Gutenberg University
Mainz (JGU) and the University of Erlangen-
Nuremberg are working on a heat engine that
consists of just a single ion. Such a nano-heat
engine could be far more efficient than, for
example, a car engine or a coal-fired power plant.
A usual heat engine transforms heat into
utilizable mechanical energy with the
corresponding efficiency of an Otto engine
amounting to only about 25 percent, for instance.
The proposed nano-heat engine consisting of a
single calcium ion would be much more efficient.
The main aim of the research being conducted is
to better understand how thermodynamics works
on very small scales. A pilot prototype of such a
single-ion heat engine is currently being
constructed at Mainz University.
Physicists at Mainz University build pilot
prototype of a single ion heat engine: Nano-heat
engine likely to operate at high efficiency /
Publication in Physical Review Letters
Mainz, Germany | Posted on February 3rd, 2014
As the physicists explain in an article recently
published in the journal Physical Review Letters,
the efficiency of heat engines powered by thermal
heat reservoirs is determined by the second law
of thermodynamics, one of the fundamental
concepts in physics. It was as far back as 1824
that Frenchman Nicolas Carnot calculated the
maximum possible efficiency limit of such
engines, now known as the Carnot limit. In the
case of the newly proposed nano-heat engine, the
scientists have been theoretically able to exceed
the classic Carnot limit by manipulating the heat
baths and exploiting nonequlibrium states.
Calculations and simulations made about a year
ago showed for the first time that the thermo-
dynamic flow in an internal combustion engine
could be reproduced using individual ions. The
idea was to use a calcium 40 ion, which has a
diameter a million times smaller than that of a
human hair, for this purpose. "Individual ions can
basically act as the piston and drive shaft or, in
other words, represent the entire engine,"
explained Johannes Roßnagel of the Quantum,
Atomic, and Neutron Physics (QUANTUM) work
group of the JGU Institute of Physics. Individual
ions have already been captured in Paul traps
and, using laser beams and electrical fields, not
only cooled and heated but also compressed.
"This means we are able to manipulate the pulse
location distribution for optimum efficiency,"
added Roßnagel. "Exceeding the Carnot limit for a
standard heat engine thus does not violate the
second law of thermodynamics but instead
demonstrates that the use of specially prepared,
non-thermal heat reservoirs also makes it
possible to further improve efficiency." In their
publication, the physicists calculated the general
Carnot limit for this situation. As the mechanical
capacity of a single ion machine is extremely low,
it can probably only be used in heating or cooling
nano systems.
The intention is now to actually develop the
proposed single ion heat engine in initial
experiments and construct a prototype in the
laboratory.