Can be operated with hot or cold things, as long as there is a large enough temperature gradient. For hot: boil some water on a beaker and place engine on top of beaker. For cold: submerge a slab of metal in liquid nitrogen until nitrogen stops boiling; then place engine on top of cold slab. Cool observation: the steam based procedure can last a long time (half an hour or more) due to water's large specific heat.
P1
PIRA DCS 4F30.10