The optimum of a sustainable refrigerant, which reveals among other criteria a high SEER/SCOP and low refrigerant GWP in combination with zero ODP can ultimately only be achieved with natural refrigerants like hydrocarbons (R290, R600a ...), NH3 (R717), CO2 (R744), or H2O (R718). The triple point of R718 limits its application to air conditioning and heat pumps. Current R718 chillers use mainly turbo compressors, due to the low volumetric cooling capacity of R718. However, the maximum pressure ratio of turbo compressors is roughly 2.0 (axial) or 4.0 (radial) per compression stage which. This limits the internal temperature lift of current and future R718 chillers with turbo compressors to about 10 K (axial) … 25 K (radial) for single-stage machines. The main applications are therefore limited to air conditioning without dehumidification (e.g. cooling of datacenters) and without heat recovery. The approach in this paper uses a novel screw compressor concept for a R718 chiller prototype with heat recovery for a temperature lift from 5 °C to 50 °C.