A comprehensive analysis of binary mixtures as working fluid in high temperature heat pumps

•An optimizer was developed to evaluate binary mixtures as refrigerant in heat pump.•Three relevant cases with different sources/sink temperature profile were identified.•For sensible sink/source cases binary mixtures improve the performance significantly.•Binary mixtures can also reduce compression ratio and compressor outlet temperature.•Water/ammonia is a suitable refrigerant once flammability is an issue in the process.