first of all you need a liquid, which has a boiling temperature at around 20°C.
by choosing the pressure level in the glass, this is the easy part for now.
the boiling happens due to heat input.
condensing means that the glass also needs the same amount of energy as an output.
this would enable a cycle and permanent boiling would be possible.
so how can a heat be extracted?
by flow, heat conduction or radiation.
and this is exactly where the difficulty lies, since the amount of heat that is transferred insde must be completely removed again.
unfortunately it is not possible to use an roughly isenthalpe throttle (change of pressure after boiling) here, because otherwise the pressure level during evaporation is simply a different one.
so what would be conceivable?
the condensation part of the vessel could be made larger.
a thermal brige (vessel condenser connected to window or floor or wall)
or
a temperature difference of the air (depending on the height in the room)
or
a condenser whose material (and shape) enables a higher heat radiation output
but all this is not trivial.
after all, you want to be able to ventilate a room and admire permanent cooking even in the middle of summer.
the design of the capacitor must be sufficient for all these cases.
and at this point you have to keep an eye on the pressure loss again (see above).
very fine flow channels for the utilization of the heat radiation could, for example, make use of the filling level (pressure).
but how much should that be? 1m? so around 0,1bar? that is not much.
so you can conclude, the thing could be realized but the condenser part will be huge compared to the boiling part.
in the end you cant really put the thing on a shelf. and it will be pretty expensive.
