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A wax motor manufactured by iSwell

A wax motor is a linear actuator device that converts thermal energy into mechanical energy by exploiting the phase-change behaviour of waxes . [ 1 ] During melting, wax typically expands in volume by 5–20% [ 2 ] .

A wide range of waxes can be used in wax motors, ranging from highly refined hydrocarbons to waxes extracted from vegetable matter. Specific examples include paraffin waxes in the straight-chain n-alkanes series. These melt and solidify over a well-defined and narrow temperature range.

The principal components of a wax motor are:

An enclosed volume of wax

A plunger or stroke-rod to convert the thermo-hydraulic force from the wax into a useful mechanical output

A source of heat such as: Electric current; typically a PTC thermistor , that heats the wax

Solar radiation; e.g. greenhouse vents

Combustion heat; e.g.…