This lecture covers the historic evolution of COP trends in power cycles and heat pumps, the key challenges in heat pump cycles, compressor technology selection, turbocompressor scaling analysis, high-speed bearing classes, and the potential of oil-free turbocompressors on COP. It also discusses domestic heating with heat pumps, thermally driven heat pump compressors, experiments on thermally driven heat pumps, and the challenges of reduced-scale turbomachinery.