The invention relates to a thermodynamic cycle apparatus, comprising: a working medium; an evaporator for evaporating the working medium; an expansion machine; a condenser, and a pump, wherein the geometrical arrangement of the evaporator is selected such that the condensed working medium can flow from the condenser to the evaporator by force of gravity and the working medium can circulate in a closed circuit via the evaporator and the condenser wherein a predetermined head height of the liquid working medium can be provided at the pump. The invention additionally relates to a method of starting the thermodynamic cycle apparatus the method comprising the following steps: applying heat to the evaporator and evaporating the working medium in the evaporator, wherein the working medium is caused to flow to the condenser; condensing the working medium in the condenser; starting the pump when a predetermined head height of the working medium at the pump is reached or exceeded.